Biology 152 Final Multiple Choice

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Among protists one taxon, Dictyostelium, can exist either as a single-celled form or a multi-cellular aggregate. How does this multi-cellular aggregation differ from true multi-cellularity and what this this ability suggest about "individuality"? a- Dictyostelium exists as a unicellular amoeboid organisms or as a complex arrangement of cells that can specialize to function in different roles. The reason that this aggregation or multicellular arrangement differs from true multi-cellularity is that the aggregation can be reversed and the cells can re-assert themselves as separate individuals, a situation that is not possible in true multi-cellular organisms. b- The ability for Dictyostelium to aggregate and produce fruiting bodies that result in spore formation and hence increase chances of dispersal are a unique advantage when the organism's resources have become diminished and a new habitat may be required for continued survival. c- Individuality among living organisms poses some intriguing questions from a biological perspective - notably in the life cycle of Dictyostelium. The absence of a discrete barrier between what distinguishes a single organism for Dictyostelium and a multi-cellular aggregate pushes the boundaries of the definition of individuality.

Coleochaetes represent green algae that tend to form ... A. ... algal mats in partially submerged freshwater rocks. B. ... huge marine colonies that are resistant to extreme cold. C. ... be sensitive to bacterial infections and are thus found only in anaerobic environments. D. ... long filamentous structures that are used to trap unsuspecting microbes E. ... small globular structures that are used as floatation devices that help keep the algae close to the water surface

Cooksonia represents an early "vascular" plant. It is thought to be the first fully terrestrial plant and as such would have possessed a particular type of tissue. What is this tissue and where would Cooksonia fall onto the cladogram of green plants from lecture # 8? a- Cooksonia possessed a form of xylem and phloem that suggests a close association with vascular plants. Its most logical placement on the cladogram presented in lecture is as the sister-clade to the monophyletic grouping that includes Lycophyta and all its descendants. b- The tissue type that is shared by Cooksonia and all vascular plants is xylem and phloem which allows for the proper movement of water and nutrients through the plant. The most logical sister-group arrangement is to place Cooksonia as the sister-clade to Lycophyta. c- Although Cooksonia is a primitive vascular plant, it shares with more derived members the presence of vascular tissue that was not fully developed in more basal plants such as bryophytes etc. Phylogenetically, Cooksonia is important as it bridges the gap between the mosses and liverworts and the more advanced seed-plants.

Describe how genetic changes might accumulate over many generations and what this accumulation might mean with respect to speciation and evolution? A The unqual ability of individuals to survice and reproduce will increase favorable traits in the population over generations. This means that over time many species will go extinct while new ones will arise. Those that survive to the present may, therefore, have little resemblance to their ancestors. B. Individuals with favourable genetic variations will produce offspring and will, therefore, pass on their favourable traits. If those conditions persist, the initial offspring that inherited the favourable trait will pass the same traits onto their offspring, thereby increasing the frequency of those traits over many generations and ultimately allowing that population to evolve. C. The more beneficial the trait is the more likely it is to be passed on to later generations. In the case of genetic mutations, change may occur suddenly, if the mutation allows the organism to fare better in its environment. Over time these mutations accumulate and evolution of new species may result. D. The accumulation of genetic differences within a population is the basis for genetic change through evolutionary history. Over geological time scales that are much greater than that which describes a human lifetime, the continued accumulation of these changes leads to a speciation event. E. None of the Above.

Describe how genetic changes might accumulate over many generations and what this accumulation might mean with respect to speciation and evolution? a- The unequal ability of individuals to survive and reproduce will lead to accumulation of favorable traits in the population over generations. This means that over time many species will go extinct while new ones will arise. Those that survive to the present may, therefore, have little resemblance to their ancestors. b- Individuals with favourable genetic variations will produce offspring and will, therefore, pass on their favourable traits. If those conditions persist, the initial offspring that inherited the favourable trait will pass the same traits onto their offspring, thereby increasing the frequency of those traits over many generations and ultimately allowing that population to evolve. c- The more beneficial the trait is the more likely it is to be passed on to later generations. In the case of genetic mutations, change may occur suddenly, if the mutation allows the organism to fare better in its environment. Over time these mutations accumulate and evolution of new species may result.

Plasmodium represents a protist that is responsible for causing malaria in what type of tissue/cell? A. Red Blood Cells. B. White Blood Cells. C. Muscle Tissue. D. Nervous tissue. E. Both A & C are correct.

Select the explanation that most accurately distinguishes between primary endosymbiosis and secondary endosymbiosis? a- When examining the endosymbiotic theory for the evolution of Eukarya, scientists have concluded that one heterotrophic single-celled organism must have engulfed another and the two eventually built a mutually beneficial symbiotic relationship. This is the explanation for how mitochondria and chloroplasts eventually became components of eukaryotic cells. The distinction between this primary endosymbiotic event and secondary endosymbiosis is that in the latter, an existing eukaryote engulfed another eukaryotic cell. This secondary approach is exactly the process by which complex single-celled organisms such as dinoflagellates and apicomplexans, to name but two, are believed to have evolved. b- The endosymbiotic theory has been around for quite some time but it is not without controversy. For example, there is still no direct means of identifying whether Eukarya existed prior to the incorporation of mitochondria or whether the association of mitochondria with some other prokaryotic heterotroph was the initial driver behind eukaryotic evolution. Nevertheless, all living eukaryotes contain organelles and once of these organelles, the mitochondrion, contains a simple strand of DNA that most closely resembles that of living bacteria. The same could be argued for the association of chloroplasts and their resemblance to cyanobacteria. There is very little doubt that the endosymbiotic theory is supported by physical evidence but the actual mechanism that was undertaken remains undetermined. c- Current textbooks describe two possible endosymbiotic hypotheses for the evolution of a number of eukaryotes. Some of the hypotheses are more fully supported than others, but an interesting one points to how some complex "protists" might have evolved. One such organism is represented by the dinoflagellates, which are common in the world's oceans and contain a number of specialized structures which belie their symbiotic origins. Others include the euglenozoans, which include the common fresh water, free-living Euglena and the pathogenic, parasitic Trypanosoma.

The nitrogen cycle is a crucial component of living systems and is absolutely essential for plant survival. Why is this cycle so crucial to plant survival and in what form does nitrogen need to be in for plants to properly absorb it? a- Plants require nitrogen for their metabolic processes, but the molecular nitrogen (N2) present in our atmosphere cannot be readily utilized by plants. Instead plants depend on a close association with bacteria which help with the nitrification process by reducing nitrogen bearing compounds such as ammonia into Nitrite (NO2-) and Nitrate (NO3-), which can then be more easily absorbed by plants. b- The nitrogen cycle is an essential part of the biosphere as the nitrogen present in organic matter undergoes decomposition and nitrification to yield reduced forms that can be more easily metabolized. However, although bacteria are active in the nitrification process they are also involved in denitrification, eventually leading to the return of fully reduced nitrogen gas back into the atmosphere. c- Microbes such as bacteria and other decomposers are active in a number of important organic cycles, including the carbon and nitrogen cycles. These elemental transformations that involve the reduction and/or oxidization of compounds are essential for the production of ATP, through a series of electron acceptors. Unlike oxygen, which is the preferred electron acceptor in aerobic environments, nitrogen takes on this critical role in environments where oxygen is less plentiful, such as soil.

The production of fleshy fruit to house and protect seeds has very high energy costs. What is a possible adaptive advantage for this costly investment? • A. Fleshy fruit is nutrient rich, which invites foraging by animals who then distribute the seeds which are generally not digested. This behaviour increases seed dispersal which is beneficial to the plant despite its costly investment. • B. An advantage for the fleshy fruit housing seeds would be that the fruit is a source of nutrients for the insects, which then increases the rate of pollination. • C. The fleshy fruit can attract animals which increases the chance of pollen being transferred from the anther of one plant to the stigma of another. • D. The added cost is offset by the advantage for the plant of having a source of reliable pollinators. • E. The development of fleshy fruit is very costly to the plant but it does provide an evolutionary advantage as it promotes outcrossing and as such reduces conspecific competition between closely associated members of a population.

This expression (2n-3)!/2^(n-1)(n-2) explains how the possible number of trees in a given data set are calculated given "n" taxa. How have Phylogeneticists compromised in dealing with the computational limits of existing computer algorithms and what is an example of this compromise? A. One compromise applies a heuristic methodology that incorporates a set of limits or boundaries. Using neighbour joining, which seeks the shortest tree in a limited predetermined number of iterations/repetitions, the shortest tree or trees are chosen. The search then repeats using the newly imposed tree-length. If in the new search a shorter tree or trees are not found, the search stops. B. One compromise applies a heuristic methodology that incorporates a set of limits or boundaries. Using neighbour joining, which seeks the longest tree in a limited predetermined number of iterations/repetitions, a set of trees is found that set the boundaries for the next iteration or search. The search then repeats using the newly imposed tree-length. If in the new search a longer tree is not found, the search stops. C. One compromise applies a cladistic methodology that incorporates a set of limits or boundaries. Using phylogenetic joining, which seeks the longest tree in a limited predetermined number of iterations/repetitions, a set of trees is found that set the boundaries for the next iteration or search. The search then repeats using the newly imposed tree-length. If in the new search a longer tree is not found, the search stops. D. One compromise applies a phenetic methodology that incorporates a set of limits or boundaries. Using parsimony philosophy, which seeks the longest tree in a limited predetermined number of iterations/repetitions, a set of trees is found that set the boundaries for the next iteration or search. The search then repeats using the newly imposed tree-length. If in the new search a longer tree is not found, the search stops. E. One compromise applies an exhaustive methodology that incorporates a set of limits or boundaries. Using neighbour joining, which seeks the shortest tree in a limited predetermined number of iterations/repetitions, the shortest tree or trees are chosen. The search then repeats using the newly imposed tree-length. If in the new search a shorter tree or trees are not found, the search stops.

What are plasmids and how do they increase genetic diversity among bacteria? A. Plasmids are either a linear or circular double-stranded DNA segment that is capable of replicating independently of the chromosomal DNA. Its ability to insert itself in segments of host DNA, where there are common sequences of nucleotides, permits rapid genetic change to occur. B. Genetic diversity among bacteria is opportunistic and given the ability that bacteria possess with respect to adding new genetic material, through conjugation and transformation, their increased variability is much more easily acquired than in eukaryotes. C. The ability to reproduce through binary fission allows bacteria to replicate rapidly in order to take advantage of available resources. This ability to reproduce in isolation (i.e., without a suitable "mate") is the most significant advantage that bacteria have over the more recently evolved eukaryotes. D. The evolution of life on this planet started with simple, single-celled organisms such as Archaea. These organisms are prokaryotic but although simple in design exhibit an array of complex metabolic processes, which have allowed them to colonize every corner of this planet. E. Plasmids represent isolated fragments of DNA that are found sporadically inside prokaryotic cells. The presence of this isolated DNA can contribute to speciation among those organisms that possess sufficient genetic material.

What are plasmids and how do they increase genetic diversity among bacteria? a- Plasmids are either a linear or circular double-stranded DNA segment that is capable of replicating independently of the chromosomal DNA. Its ability to insert itself in segments of host DNA, where there are common sequences of nucleotides, permits rapid genetic change to occur. b- Genetic diversity among bacteria is opportunistic and given the ability that bacteria possess with respect to adding new genetic material, through conjugation and transformation, their increased variability is much more easily acquired than in eukaryotes. c- The ability to reproduce through binary fission allows bacteria to replicate rapidly in order to take advantage of available resources. This ability to reproduce in isolation (i.e., without a suitable "mate") is the most significant advantage that bacteria have over the more recently evolved eukaryotes.

What are the primary advantages and disadvantages to wind pollination and why does wind pollination persist in many plants if it truly a disadvantage? a- The processes of natural selection act on promoting any trait that provides some competitive benefit to an individual. Although wind pollination is not an effective means of promoting plant reproduction in wet environments, it is highly advantageous in regions with a short growing season and with low rainfall. As such, what might be a disadvantage under one set of circumstances, would instead by advantageous in another and hence the behaviour/practice persists among many plants. b- The major advantage of wind pollination is associated with environments that exhibit low diversity and have unpredictable growing seasons. However, in many other types of environments such as those that are very wet, such as the tropics, wind pollination presents a significant disadvantage to the plants that depend on this means of reproduction. Grasses are an example of a wind pollinated plant that is common in open habitats but uncommon in tropical forests. c- Selective forces function to ensure the survival of those organisms that possess the most useful and/or beneficial traits for survival in a given environment. However, traits that may provide an advantage in one environment may not be helpful in another and this is why wind pollinated plants tend to be common in some environments and rare in others. The conditions that suit wind pollinated plants depend primarily on geography and more specifically the climatic conditions of the particular region.

What is a pollinator syndrome and how is it managed to ensure continued survival of both pollinator and plant? a- A pollinator syndrome is a term used to describe a very precise association between a particular animal (often an insect) and a species of plant. The association depends on a number of important events such as the timing of flowering, so that it might better coincide with insect mating behaviours, etc. In addition, the amount of pollen and other resources are closely controlled to ensure the most energy efficient exchange between the pollinator and the flower/plant. b- In order to ensure that a particular pollinator and a plant develop a mutually beneficial association, pollinator syndromes evolved to maximize the needs of both. In other words, the timing of certain events in the plant needed to coincide with certain insect behaviours so that a dependency between pollinator and plant would be confirmed and hence perpetuated. c- Pollinator syndromes represent an association between animal and plant aimed at ensuring a continuing dependence between the two organisms. Without pollinator syndromes, the mutualistic behaviour commonly found between plants and insects would never have evolved and animal dependent pollination would not have come to represent such a significant aspect of plant and animal interactions

What is descent with modification? a- Descent with modification is explained as the mechanism that will allow descendants of some organisms to retain/propagate traits that provide those descendants with an advantage, given the environmental conditions. Gradually, over time, making subsequent generations of descendants different from their ancestors. b- Descent with modification is an important segment in Charles Darwin's theory of Evolution, it is the passing on of parental traits and characteristics to offspring, and so the population evolves as greater survival and reproductively advantageous traits are passed on. c- Descent with modification primarily refers to genes that are inherited throughout many generations which modify the genotype and possibly the phenotype over time. This modification is due to constraints which only allow successful genes to be passed on (natural selection).

What is meant by a monophyletic taxon? a- In phylogenetic systematics, monophyly is defined as a minimum of two taxa that have diverged from a single node and share a single, common ancestor. b- Monophyly is defined as a clade or group of organisms that shares a common ancestry. There is no limit to how many taxa can be included in a monophyletic group or clade. c- The ability to assign sister-group relationships between a range of organisms is the key behind the definition of a monophyletic unit.

What is meant when a phylogeneticist describes a cladogram or phylogenetic tree as the "Most Parsimonious" and who is responsible for this postulate? a- Occam's razor is a mathematical postulate that says that the simplest solution is often the most accurate. This explanation is described as parsimony and, therefore, when phylogeneticists describe a cladogram as "Most Parsimonious" they are suggesting that it is the shortest and hence most plausible phylogenetic tree. b- The concept of parsimony is based on the mathematical principle that the shortest, simplest solution to a problem is likely the most accurate. William of Occam developed this postulate back in the 13th century and it has been adopted by phylogenetic systematists as the basis for "Maximum Parsimony". c- In phylogenetic hypotheses testing, there are a number of methods that have been applied to testing the consistency of a cladogram. One method reflects the concept of parsimony which is an adaptation of the philosophical argument - "Numquam ponendo est pluritas sine necessitate."

What is one of the hypotheses that supports the path leading to the evolution of complex leaves, such as megaphylls, from the more primitive microphylls? a- A prevailing hypothesis for the evolution of megaphylls is that the more primitive finger-like microphylls, which were essentially small bifurcations that resulted from the branching of the central stem, developed extensions of parenchyma tissue, between adjacent members, that eventually linked these individual "leaflets" together, resulting in the complex venation patterns we see in leaves today. b- The evolution of broad leaves was a significant event in the evolution of higher plants as it effectively increased the surface area where photosynthesis could occur and thus provided much greater access to the sun's energy than would have been possible is leaves had never evolved past the microphyll stage. c- The earliest leaves are believed to have evolved from the sporangia that are found in the most primitive non-vascular and even the early vascular plants. Since sporangia were spore bearing structures that tended to grow on the periphery of the plant, they were also more fully exposed to the sun and generally possessed a high surface to volume ratio. Therefore, any photosynthetic tissue that occupied these reproductive sporangia would also be an excellent source for the production of food - over time some of these structure became exclusively adapted for a food production role.

What is the basis for the origin of the nuclear membrane/envelope and what might have been the initial adaptive reason for its development? a- One hypothesis claims that during the evolution of Eukarya, the plasma membrane became prominently infolded. Initially this infolding served to increase surface area and hence enhanced absorption, but over time this infolded membrane became closely associated with the cells chromosomes (DNA) and was co-opted to function as a barrier to separate the nuclear material from the cell's cytoplasm. b- Among eukaryotes, the nuclear material is segregated from the cytoplasmic organelles by way of a nuclear membrane. The origins of this membrane are disputed but there is some support for the membrane evolving through a symbiotic association with another prokaryotic organism, such as a bacterium. The rationale for this pathway is carved out of the endosymbiotic theory for the evolution of Eukarya. c- All living Eukarya contain inter-cellular organelles and a distinct nucleus. These structures are absent in both Eubacteria and Archaea and are hence a valid synapomorphy uniting all eukaryotes to the exclusion the others. The reason for the evolution of the nuclear envelope is uncertain but it appears to have occurred sometime after the separation between Eubacteria and Archaea.

What morphological differences characterize the two growth forms of extant fungi? a- In general, fungi can be grouped on the basis of two distinct life forms. One form which is believed to be the more primitive is commonly referred to as yeasts and is represented by single-celled organisms, whereas the alternative life form is represented by web-like filaments called mycelia. b- The major difference between the two known fungal life forms is that one form is parasitic and the other is mutualistic. In terms of the impact to human society, one life forms results in significant economic costs whereas the other provides extensive benefits. c- Single-celled fungal life forms are considered to be the more primitive members of the fungi and it is one of the reasons why slime molds, which are not true fungi, were once thought to be closely related. Today, we recognize that there are over 80,000 species of fungi and many are actually quite beneficial to human society.

What trait of the angiosperm water vascular system differs significantly from other vascular plants? a- Flowering plants possess a series of complex cell structures associated with xylem tissue that are unknown in other plants. One of the major differences is the presence of vessel elements, specialized cells that are perforated at their ends resulting a in tubular network allowing for the rapid transportation of water through the plant. b- All angiosperms are derived relative to gymnosperms in possessing the ability to produce flowers, which allow for the protection of the developing embryo inside a life sustaining ovary. This advancement in reproductive capacity provided flowering plants with the ability to rapidly diversify, resulting in the extensive world-wide distribution of the clade. c- Unlike gymnosperms, angiosperms possess an additional tissue types known as phloem, which enhances the ability of these plants to circulate larger volumes of water through their vascular network. This ability has provided angiosperms with a much greater ability to colonize diverse habitats, which has led to the great success of the clade.

When did angiosperms begin their close association with animals and how did this association get started? a- It is generally regarded that plant associations with animals were established during the Cretaceous, but although today many of these associations are mutualistic, it is believed that initially these interactions were borne out of exploitation. In other words, animals, primarily insects, began by trying to take advantage of the plants or the plants began by trying to take advantage of the insects. There is more evidence in support of the latter than the former. b- Plant associations with insects can be traced back to the Cretaceous where a mutualistic interaction is believed to have developed where both plant and insect benefited from the interaction. Today, the majority of angiosperms depend heavily on insect pollination to ensure their own survival. It is estimated that if a pollinating insect such as the bee would become extinct that a number of important commercial species of plants would follow. c- Competition for survival is as ancient as the first organisms that inhabited this planet. Interactions between competing organisms will sometimes lead to a type of interaction known as mutualism and this is precisely what scientists believe happened with respect to plants and insects. Today, the vast-majority of flowering plants have some sort of mutualistic interaction with insects.

Which of the following organisms are more closely related to land plants? A. Stoneworts. B. Coleochaetes. C. Red Algae D. Ulvophytes E. Cyanobacteria.

Why is drug resistance in bacteria influenced by our practice of antibiotic use? • A. The indiscriminate use of antibiotics permits rapidly reproducing bacteria with the opportunity to acquire genetic material through mutation & conjugation, therefore, resulting in drug resistant forms. • B. The indiscriminate use of antibiotics can cause harm to our very own gut flora by eliminating those essential bacterial populations in what can best be described as a "nuk'em" approach. • C. The indiscriminate use of antibiotics has had a significant impact on the cost and efficiency of our health care system. • D. A, B, & C are correct. • E. None of the above.

Why is drug resistance in bacteria influenced by our practice of antibiotic use? A. The indiscriminate use of antibiotics permits rapidly reproducing bacteria with the opportunity to acquire genetic material through mutation & conjugation, therefore, resulting in drug resistant forms. B. The indiscriminate use of antibiotics can cause harm to our very own gut flora by eliminating those essential bacterial populations in what can best be described as a "nuk'em" approach. C. The indiscriminate use of antibiotics has had a significant impact on the cost and efficiency of our health care system. D. A, B, & C are correct. E. None of the above.

Why is the term "Protista" not considered a viable phylogenetic rank and what traditional example is used to support the unnatural grouping? a- Historically, protists represented a collected of single-celled organisms that could not easily fit into either the plant or animal kingdoms. Little thought was given to common descent, which resulted in the placement of bacteria, such as cyanobacteria, into a close association with green algae. b- Protists represent a collection of closely related microbes that share a distant phylogenetic relationship. However, more recently we have come to recognize that some protists are more closely related to bacteria than they are with other groups such as plants. c- The phylogenetic history of "Protista" is one of informal classification that is based on general similarity and not due to common descent. This non-phylogenetic construct is not unlike the Linnean classification of elephants and rhinos, which were once grouped together in the unnatural pachyderms.

The evolutionary history of a given taxon determines its character distribution (i.e., which characters are symplesiomorphic vs. characters that are synapomorphic). What is essential to correctly polarize a character set? A. The only way to ensure proper character polarization is if a discrete out-group taxon is included in the analysis, otherwise symplesiomorphic characters could inadvertently be B. In order to fully polarize a character set, it is necessary to ensure that a wide range of taxa are utilized so that better character resolution is possible. This often requires the use of many taxa, as the more diverse the taxon sample is the more informative it is likely to be. C. The evolutionary history of life on this planet is classified through the use of phylogenetic systematics. Taxa and characters are evaluated using computer algorithms that are designed to yield the most plausible phylogenetic hypothesis. D. A complete character set is necessary in order to test an hypothesis of relationships. To compile this set, characters must be polarized through a test for primary homology. This approach is possible only if you use non-supra-generic taxa, which eliminates ambiguities in character polarization.

ABCD

The most basal member of the Unikonta (Amorphea) are the Amoebozoa. One amoebozoan, commonly used in scientific research, is the slime mold Dictyostelium. Although, the common name suggests a relationship with fungi, does current phylogenetic evidence support this relationship? A. As an amoebozoan, slime molds are known to share some affinity with animals and their relatives, such as fungi. This close association led to the taxonomic inclusion of slime molds within the Fungi, which phylogenetic evidence now recognizes as false. B. Slime molds such as Dictyostelium are extremely important in scientific research, especially when exploring the distinction between single-celled organisms and true multi- cellularity. Much of this research stems from an examination of its complex life-cycle where a single, free living cell can, under the right condition, divide into a collection of cells that specialized to serve different functions. C. The Amoebozoa represent one clade among the Unikonta (Amorphea), which are believed to represent the most basal members of that assemblage. Until quite recently, it was believed that amoebozoans and opisthokonts (animals and their kin) shared a common ancestry, but this has more recently been challenged. D. Amoebozoans such as Dictyostelium belong to a monophyletic group known as the Opisthokonta. This taxon is closely allied to Animalia and includes all members of the fungi. Present day phylogenetic evidence is supportive of a close association, but the exact sister-group distribution is uncertain.

ACBD

What is likely the single most significant extinction event in the history of this planet and what organism was responsible? • A. The advent of photosynthesis by cyanobacteria over 2.5 billion years ago resulting in the release of O2 as a byproduct likely caused the extinction of most lifeforms on the planet. • B. The dramatic change to the climate over 2.5 billion years ago resulted in changes that have never before been experienced on earth and dwarfs the current climate change we are experiencing. • C. The evolution of cyanobacteria over 2.5 billion years ago resulting in the release of O2 as a byproduct likely caused the extinction of most lifeforms on the planet. • D. The advent of photosynthesis by green algae over 2.5 billion years ago resulting in the release of O2 as a byproduct likely caused the extinction of most lifeforms on the planet.

ACBD

In a hypothetical experiment to test for the occurrence of natural selective forces, bird populations have their beak depth measured over a period of nearly 50 years in an environment where food sources (i.e., seeds) are transitioning from small to larger, thicker shelled variants. What would you expect to find if selection is acting on beak depth? A. As natural selection acts on the variability in a population, the larger beaks should, on average show a shift toward larger size. This will not eliminate the other beak sizes but a B. Given that natural selection acts directly on individuals within a population, we should see no change in the population beak size ratios as the path regarding beak evolution would remain random. C. Natural selection would act on all birds in the population and would select for larger beaks capable of cracking the thicker seeds. D. The events influencing natural selection on this hypothetical population of birds would be an excellent opportunity to examine the rate of change and how quickly a group might evolve if placed under significant selective pressure.

ACDB

How did Darwin impact society in the 19th and early part of the 20th centuries and what challenges do we face when trying to explain "fitness" to the non-biologist? • A. Darwin's theory changed our view of the natural world and his use of terms such as "survival of the fittest" continue to confound the non-biologist, as is true for many scientific terms to which we apply a colloquial (common or non-scientific) usage. It is essential that evolutionary "fitness" be explained as opportunistic and not exclusively as the more generally perceived "superior". • B. Darwin was solely responsible for changing the biological landscape and all of us today have to deal with the repercussions, including but not limited to how the idea of "survival of the fittest" explains the notion of "use and disuse" which is so fundamental to evolutionary theory. • C. Darwin's theory was undoubtedly the most significant contribution to the natural sciences since Socrates and his theory of Evolution established biology as a study that is much more than a science that was primarily dedicated to classification and description but one which asked questions about the very origins of life. • D. Darwin's theory changed how we viewed ourselves and his use of terms such as "survival of the fittest" continue to confound the non-biologist, as is true for many scientific terms to which we apply a colloquial (common or non-scientific) usage. It is essential that "fittest" be described as being opportunistic and not as "superior".

ADCB

How has climate been influenced by changes in the distribution of continental land masses? A. During the early part of the Paleozoic, one large continent (Pangea) meant that the ocean was one large body of water where currents flowed uninterrupted. B. The break-up of the super continent Pangea resulted in a number of smaller separate continents, which in turn produced a series of additional bodies of water that in turn C. Present day continent distribution is very different from the conditions found during the Paleozoic era, which explains why climate would have been significantly different from that which we experience today. D. Modern day climate changes is influenced by much more than greenhouse gas emissions. Throughout earth's history, fluctuations in the composition of atmospheric gases has either caused the earth to cool or to heat up. E. A large super continent has a very different influence on climate than a land masses that are distributed throughout the earth's surface, as we have today.

How has climate been influenced by changes in the distribution of continental land masses? a- During the early part of the Paleozoic, one large continent (Pangea) meant that the ocean was one large body of water where currents flowed uninterrupted. b- The break-up of the super continent Pangea resulted in a number of smaller separate continents, which in turn produced a series of additional bodies of water that in turn changed ocean currents resulting in a disruption to atmospheric currents. c- Present day continent distribution is very different from the conditions found during the Paleozoic era, which explains why climate would have been significantly different from that which we experience today.

The evolution of fully terrestrial plants depended primarily on which steps and in what order are these critical evolutionary events believed to have evolved? a- Once out of water plants needed to overcome a number of challenges. The most important was the ability to photosynthesize efficiently, followed by an ability to resist desiccation, which in turn demanded the development of a waxy cuticle and the evolution of a sophisticated vascular system. b- Leaving the water required plants to resist desiccation, which in turn led to the evolution of a water resistant cuticle and the eventual appearance of pores and ultimately stomata. In addition, terrestrial plants needed to develop an ability to reach upward away from the substrate, which in turn led to the evolution of a supportive stem and more efficient photosynthetic structures known as microphylls. c- The most critical step in the evolution of terrestrial plants was the ability to house and protect an embryo, which was no longer bathed in the water. Secondly, terrestrial plants needed to evolve a means of transporting nutrients and water through their tissues, which required the evolution of a water vascular transport system and the eventual evolution of complex leaves known as megaphylls.

There are a number of methods that are currently used to apply or test phylogenetic hypotheses. In all cases, computer algorithms are used to construct the phylogenetic trees. Which statement below best responds to the concept of the "Greedy Algorithm"? • A. The "Greedy Algorithm" considers the probability that a chosen evolutionary path supports the given hypothesis. • B. The "Greedy Algorithm" consider the possibility that there is a risk of missing the most likely phylogenetic path as the path selected by the algorithm might have missed the real or actual path. • C. The "Greedy Algorithm" opines that the shortest path is the most likely event to support the given hypothesis. • D. The "Greedy Algorithm" is a hypothetical argument that argues that the most complex path is the most likely evidence supporting the given hypothesis. • E. The "Greedy Algorithm" represents a hypothetical statement that argues that the shortest most direct path is the most likely event to explain the given evolutionary hypothesis.

Using the graph provided, what conclusions can best reflect our societies use of wood based products over the last 200 years? In making your choice, consider the points that were discussed in the last lecture as well as the data as presented in the graph and select the statement that best fits the arguments that were presented. a- Fossil fuels have been a major component of human civilization and continue to be one even to the present. Although the choice of fuel has changed over the last 20 years, the source of the fuel remains primarily a by-product of plants. Since the end of the 20th century, there has been a perceptible change in the ratio of petroleum vs. coal with the two moving in opposite directions. b- Modern society depends as much on plants for its fuel use as earlier societies have. In fact, the only difference between the present day and societies in the past is the choice of plant material responsible for the fossil fuel we use. Changing economic cycles, such as the rapid economic growth of China in the last few decades has resulted in trend whereby coal use has actually made a slight return to levels not witnessed since before the 1960s. c- A global solution to address the crisis between fossil fuels and its well documented link to climate change requires modern society to develop alternatives to fossil fuels. Some of these alternative fuels are already in use today, but much more research is required to permanently eliminate our dependence on fossil fuels.

What best describes fungi and their way of acquiring nutrients and what is meant by the term osmotrophy? a- Fungi represent a complex life form that exists in a number of symbiotic relationships with other organisms. The most frequently recognized association is with plants and specifically flowering plants, where fungi help in the processing of nitrogen. Osmotrophy is best interpreted as the ability to absorb nutrients through osmosis. b- Among fungi, the acquisition of nutrients is described as mixotrophic, which implies an ability to exist across a range of metabolic methods that can include autotrophic and heterotrophic methods. While feeding, fungi are osmotrophic, which implies that they absorb nutrients osmotically across a concentration gradient - the fundamental definition of osmotrophy. c- All fungi are osmotrophic, which describes a method of nutrient acquisition that relies on the absorbance of nutrients across a concentration gradient. Many fungi are also parasitic and can be the cause of a number of human pathogens.

What is currently one of the more well supported hypotheses for the origin of the nuclear membrane/envelope and what might have been the initial adaptive reason for its development? A. Among eukaryotes, the nuclear material is segregated from the cytoplasmic organelles by way of a nuclear membrane. The origins of this membrane are disputed but there is some support for the membrane evolving through a symbiotic association with another prokaryotic organism, such as a bacterium. The rationale for this pathway is carved out of the endosymbiotic theory for the evolution of Eukarya. B. One hypothesis claims that during the evolution of Eukarya, the plasma membrane became prominently infolded. Initially this infolding served to increase surface area and hence enhanced absorption, but over time this infolded membrane became closely associated with the cells chromosomes (DNA) and was co-opted to function as a barrier to separate the nuclear material from the cell's cytoplasm. C. All living Eukarya contain inter-cellular organelles and a distinct nucleus. These structures are absent in both Eubacteria and Archaea and are hence a valid synapomorphy uniting all eukaryotes to the exclusion the others. The reason for the evolution of the nuclear envelope is uncertain but it appears to have occurred sometime after the separation between Eubacteria and Archaea. D. Current textbooks describe two possible endosymbiotic hypotheses for the evolution of a number of eukaryotes. Some of the hypotheses are more fully supported than others, but an interesting one points to how some complex "protists" might have evolved. One such organism is represented by the dinoflagellates, which are common in the world's oceans and contain a number of specialized structures which belie their symbiotic origins. Others include the euglenozoans, which include the common fresh water, free-living Euglena and the pathogenic, parasitic Trypanosoma. E. None of the Above.

What is meant by the weighting of a phylogenetic character? a- Some cladists argue that weighting of character states is inappropriate as presumes - a priori - that the investigator is choosing an evolutionary path for which there is no direct evidence. b- Character weighting is often done to increase the resolution of a cladogram. This effectively means that a single character can carry the influence of multiple characters. c- In one of our lectures we examine how weighting of a character helps to resolve a phylogenetic uncertainty.

What is meant regarding the establishment of "Primary Homology" for a character trait when attempting to reconstruct a phylogenetic tree? a- Character traits can be homologous or analogous. In the former, the trait has been inherited through common ancestry, whereas in the latter, the trait evolved independently. Only traits that can be traced to a common ancestor can be used for establishing phylogenetic relationships. b- A homologous trait may be informative only if it has a recent origin (synapomorphy). For example, primitive characters, although inherited through common descent may contribute very little to phylogenetic hypothesis testing. c- Primary homology is the term used to distinguish between convergent and shared plesiomorphic character states from those characters that may represent synapomorphies.

What is one of the more phylogenetically relevant distinctions between monocots and dicots? a- Both monocots and dicots are anthophytes (angiosperms) and hence both produce flowers. Monocots differ in the structure of the embryo, which results in a single cotyledon, whereas dicots possess a pair of these embryonic tissues. b- Amongst flowering plants, monocots can trace their ancestry to single common ancestor, whereas dicots appear to have evolved at least two separate times. c - All dicots are more fully derived than monocots and can trace their origins to a unique monophyletic point of origin.

What is the phylogenetic impact of having Archaea fall out as the sister taxon to Eukarya? a- Amongst the earliest single celled, prokaryotic organisms, Archaea and Eubacteria (Bacteria) are believed to represent the earliest organisms to have evolved on this planet. Contrary to the primitive nature that is generally assigned, these two groups of organisms possess sophisticated metabolic processes that include pathways of cellular respiration and fermentation that would be more fully expected in more derived taxa such as Eukarya. b- Although Eubacteria (bacteria) and Archaea share some general similarities, they are not that closely related. In fact, more recent work suggests that Archaea actually share a closer affinity to Eukarya and are thus more closely related to us than to bacteria. c- The evolution of life on this planet started with simple, single-celled organisms such as Archaea. These organisms are prokaryotic but although simple in design exhibit an array of complex metabolic processes, which have allowed them to colonize every corner of this planet.

What is the primary morphological difference between vascular and non-vascular plants? a- Vascular plants are much more complex than non-vascular plants and are able to dominate a wide range of environments. This ability to undergo a number of adaptive radiations has permitted vascular plants to evolve many diverse forms and is a primary reason for their current success. b- Although there are many differences that exist between these two plant forms, the most immediate difference lies in the presence of two tissue types in vascular plants (i.e., xylem and phloem), which are absent in non-vascular forms. c- Vascular plants are able to colonize terrestrial habitats that are not readily available to nonvascular plants, as water transportation networks are absent in the latter and hence restrict their ability to colonize a wide range of terrestrial habitats.

Why is it essential for evolutionary biologists to establish the "Primary Homology" for a character trait when attempting to reconstruct a phylogenetic tree? A. Character traits can be homologous or analogous. In the former, the trait has been inherited through common ancestry, whereas in the latter, the trait evolved independently. B. A homologous trait may be informative only if it has a recent origin (synapomorphy). For example, primitive characters, although inherited through common descent may C. Primary homology is the term used to distinguish between convergent and shared plesiomorphic character states from those characters that may represent synapomorphies. D. Phylogenetic systematics is a novel approach for examining the history of life on this planet and is based on the cladistic methodology that was developed by Willi Hennig in the 1950s. E. All except "D" are possible.

Why would it be appropriate to refer to Reptilia as Paraphyletic? a- Historically, taxonomists separate amniotes into three major groups, reptiles, birds, & mammals. However, this classification fails to recognize the evolutionary descent of birds from reptiles. b- A unit or group of organisms is termed paraphyletic if one or more members of the clade are excluded from their systematic classification. The exclusion, by most classification methodologies, of birds from Reptilia renders the latter paraphyletic. c- A paraphyletic group is defined on the basis of excluding one or more members of that respective clade. This practice is based on pre-cladistic interpretations of taxonomic classification.

5. What did Linnaeus base his classification on and how does it differ from the modern phylogenetic methodology. A. The hypothesis that life has more than one origin. B. Linnaeus based his classification on phenetics - that similarity of appearance meant close association of different species. C. Linnaeus based his classification on Occam's razor that the simplest path to the evolution of a group must be the correct path. D. That multiple generations arose independently. E. None of the Above.

B NEED TO FIX

Lycophytes include modern taxa that tend to be small in stature but during the Carboniferous ... A. ... some lycophytes were extremely large and produced fragrant fruit that attracted the many insects that were abundant during the lush tropical climate of that period. B. ... many lycophytes were enormous reaching heights of more than 15 or 20 metres and having trunk diameters that exceeded 1 metre. C. ... most lycophytes were ground hugging plants that spread over huge areas creating what might best be described as an algal mat. D. ... the vast majority of lycophytes were mid-sized, tree-like plants with woody secondary growth. E. ... lycophytes were rare and were restricted to the hot dry regions that were common during the period.

B NEED TO FIX

Why specifically would it be appropriate to refer to FISH as a paraphyletic taxon? A. Historically, taxonomists separate amniotes into three major groups, reptiles, birds, & mammals. However, this classification fails to recognize the evolutionary descent of birds from reptiles. B. A unit or group of organisms is termed paraphyletic if one or more members of the clade are excluded from their systematic classification. The exclusion, by most classification C. A paraphyletic group is defined on the basis of excluding one or more members of that respective clade. This practice is based on pre-cladistic interpretations of taxonomic classification. D. Paraphyly is common in present day classification, with many current taxonomic units being excluded from clades that otherwise share direct common ancestry. E. Monophyletic units are the single most important basis for modern day classification. However, it is not uncommon for related taxa to be excluded from a more inclusive grouping from which they descended. The result is that many supra-generic ranks are paraphyletic.

B NEED TO FIX

The evolutionary history of a given taxon determines its character distribution (i.e., which characters are symplesiomorphic vs. characters that are synapomorphic). What is essential to correctly polarize a character set? • A- In order to fully polarize a character set, it is necessary to ensure that a wide range of taxa are utilized so that better character resolution is possible. This often requires the use of many taxa, as the more diverse the taxon sample is the more informative it is likely to be. • B- The only way to ensure proper character polarization is if a discrete out-group taxon is included in the analysis, otherwise symplesiomorphic characters could inadvertently be considered as derived. • C- The evolutionary history of life on this planet is classified through the use of phylogenetic systematics. Taxa and characters are evaluated using computer algorithms that are designed to yield the most plausible phylogenetic hypothesis. • D- A complete character set is necessary in order to test an hypothesis of relationships. To compile this set, characters must be polarized through a test for primary homology. This approach is possible only if you use non-supra-generic taxa, which eliminates ambiguities in character polarization.

BACD

Complete the statement by selecting the most appropriate statement: Cyanobacteria represent ... A. ... monophyletic bacteria that are the sister-group of plants B. ... organisms that resembles algae but is prokaryotic and more closely related to bacteria than to plants. C. ... single celled photosynthetic archean. D. ... prokaryotic organisms that are more closely related to proteobacteria than to plants. E. ... a multicellular organism distantly related to modern plants.

Dictyostelium, can exist either as a single-celled form or a multi-cellular aggregate. How does this multi-cellular aggregation differ from true multi-cellularity and what does this ability suggest about "individuality"? A. The ability to aggregate and produce fruiting bodies that result in spore formation and hence increase chances of dispersal are a unique advantage when the organism's resources have become diminished and a new habitat may be required for continued survival. B. Individuality among living organisms poses some intriguing questions from a biological perspective - notably in the life cycle of Dictyostelium. The absence of a discrete barrier between what distinguishes a single organism for Dictyostelium and a multi-cellular aggregate pushes the boundaries of the definition of individuality. C. Dictyostelium exists as a unicellular amoeboid organism or as a complex arrangement of cells that can specialize to function in different roles. The reason that this aggregation or multi-cellular arrangement differs from true multi-cellularity is that the aggregation can be reversed and the cells can re-assert themselves as separate individuals, a situation that is not possible in true multi-cellular organisms. D. Although there are many differences that exist between these two forms, the most immediate difference lies in the presence of two tissue types in the multi-cellular state (i.e., xylem and phloem), which is absent in the single celled form. E. Both C & D are correct.

Distinguish between ingestive feeding and absorptive feeding among protists. A. Ingestive feeding is only possible in protists that lack a cell wall as the outer membrane can expand and surround the prey, usually bacteria or archaea. Once engulfed, digestive enzymes can chemically break down the food item. Absorptive feeding differs in that material simply diffuses across the outer membrane, and is common only to amoeboid protists. B. Among many single-celled organisms, both forms of feeding are practiced. The distinction between the two forms is that one method is active while the other is passive. Phylogenetically the passive method is believed to be more derived. C. Two primary forms of feeding are common in single-celled protists: ingestive feeding, which requires the ability of the protist to use pseudopodia to surround the prey item, and absorptive feeding, which is accomplished by either simple or active diffusion across the outer membrane. D. Both B & C E. None of the above.

Distinguish between ingestive feeding and absorptive feeding among protists? a- Ingestive feeding is only possible in protists that lack a cell wall as the outer membrane can expand and surround the prey, usually bacteria or archaea, and then allow digestive enzymes to chemically break down the food item. Absorptive feeding differs in that material simply diffuses across the outer membrane. b- Among many single-celled organisms, both ingestive and absorptive feeding are practiced. The distinction between the two forms has to do with the more active mechanism that is involved with ingestive feeding while a more passive method is applied for absorptive feeding. c- Two primary forms of feeding are common in single-celled protists: ingestive feeding, which requires the ability of the protist to use pseudopodia to surround the prey item, and absorptive feeding, which is accomplished by either simple or active diffusion across the outer membrane.

Early terrestrial plants experience alternation of generations. Among ferns the dominant life cycle is ... A. ... dominated by the gametophyte generation which is characterized by haploid cells. B. ... the result of a fully functional gametangia that results in the production of both microspores and megasopres. C. ... the sporophyte generation, which is made up of diploid cells. D. ... expressed by the macrosporangium, which is the major spore producing site of this primitive plant. E. Both C & D are correct.

Examine the figure provided and identify the image that most likely contains a 2n (diploid) structure? Explain how you came to that conclusion. a- Option C is the most likely as it contains two separate hyphal nuclei (shown as black and white) inside a sporangium of the Basidiomycota fungus. These different coloured structures refer to genetic material from different fungal hyphae that are in the process of fusing. b- All except option A represent stages in fungal reproduction where either the same or different mating types have fused or are in the process of fusing. c- Option B is most likely as it represents the zygosporangium of the Zygomycota fungus. This structure is the result of the fusion of two haploid hyphae from either the same or different mating types.

Explain how artificial selection can provide clues to serendipitous nature of natural evolution? a- Humans have modified specific species over many generations by selecting and breeding individuals that possess desired traits, this has led to the rich diversity we see today. Some of the animals or crops we have today, did not exist before. b- Artificial selection can provide us with clues to evolution because it can be used to assess how selecting for a particular trait (i.e., genes) to express a specific phonotype may result in unexpected, hidden changes, that in turn may result in either adaptive or maladaptive traits. c- An example of artificial selection is dog breeding; you take two different dogs and breed them to make a desirable one for the consumer. If consumers only want certain types of dogs, the ones needed to produce that offspring will be allowed to breed, and all others will be ignored and go extinct. So, this form of "human driven evolution" will favour the dogs needed to produce the desired breed or phenotype.

Heterochrony plays a very important role in the evolutionary process. What aspect of heterochrony plays a critical role in the evolution of chimps and humans from a shared common ancestor? a- Humans and chimps are closely related and share a great deal in common including over 98% of the entire genome. Most of the genetic differences can be attributed to the timing of development. b- Heterochrony refers to the process by which development is regulated in organisms and the differences in timing can be enough to lead to evolution of entirely new species, especially when studying closely related groups. c- In the evolution of apes, humans and chimps diverged from a common ancestor due to changes in the timing of development. The most notable difference is represented by the prolonged neotenic period that is influenced by a heterochronic shift in the development of humans.

How does the presence of Hox genes help to support a monophyletic origin for animal life on earth? a- The presence of a number of regulatory genes in a wide range of organisms is supportive of a common ancestry for all animals and emphasizes the conservative nature of regulatory genes. These genes have effectively remained unchanged throughout evolutionary history. b- The fact that Hox genes which are found in invertebrates such as flies and in vertebrates such as humans are effectively the same supports the nature of common descent. c- The fact that the same Hox genes that regulate body segmentation in insects are homologous with the genes that regulate body partitioning in humans is strong support for a common ancestry for animals

How has the cladistic methodology influenced traditional taxonomic classification? a- In traditional Linnean classification, hierarchical ranks were rigid and hence did not allow for the inclusion of novel interpretations. b- An entomologist named Willi Hennig developed the cladistic methodology to help distinguish between the many species of beetles that he worked on. c- A greater emphasis on establishing the necessary homology in cladistic applications have taught us that overall similarity is not necessarily and indicator of common descent.

Individual vessel elements in the xylem of angiosperms (anthophytes) regulate water pressure by ... • A. ... reducing or increasing the water absorption rate form the substrate (ground). • B. ... their ability to resist expansion. • C. ... their ability to share water volume with neighbouring vessels elements. • D. ... an ability to expand and contract as necessary. • E. ... an ability to shutdown water intake when pressure is too high.

The evolution of "true leaves" appears to have been accomplished ... A. ... by reducing or increasing the water absorption rate form the substrate (ground). B. ... through the expansion of root tissue. C. ... through morphological and functional changes in the reproductive structures D. ... by the development of cuticle which once established could grow and expand into what we now recognize as a leaf or "megaphyll". E. ... by an ability to transform epidermal tissue into photosynthetic tissue.

The most basal member of the Unikonta (Amorphea) are the Amoebozoa. One amoebozoan, commonly used in scientific research, is the slime mold Dictyostelium. Although, the common name suggests a relationship with fungi, does current phylogenetic evidence support this relationship? a- Slime molds such as Dictyostelium are extremely important in scientific research, especially when exploring the distinction between single-celled organisms and true multi-cellularity. Much of this research stems from an examination of its complex life-cycle where a single, free living cell can, under the right condition, divide into a collection of cells that specialized to serve different functions. b- The Amoebozoa represent one clade among the Unikonta (Amorphea), which are believed to represent the most basal members of that assemblage. Until quite recently, it was believed that amoebozoans and opisthokonts (animals and their kin) shared a common ancestry, but this has more recently been challenged. c- As an amoebozoan, slime molds are known to share some affinity with animals and their relatives, such as fungi. This close association led to the taxonomic inclusion of slime molds within the Fungi, which phylogenetic evidence now recognizes as false.

What is meant when a phylogeneticist describes a cladogram or phylogenetic tree as the "Most Parsimonious" and who is responsible for this postulate? A. The concept of parsimony is based on the mathematical principle that the shortest, simplest solution to a problem is likely the most accurate. William of Occam developed this postulate back in the 13th century and it has been adopted by phylogenetic systematists as the basis for "Maximum Parsimony". B. In phylogenetic hypotheses testing, there are a number of methods that have been applied to testing the consistency of a cladogram. One method reflects the concept of parsimony which is an adaptation of the philosophical argument - "Numquam ponendo est pluritas sine necessitate". C. Occam's razor is a mathematical postulate that says that the simplest solution is often the most accurate. This explanation is described as parsimony and, therefore, when phylogeneticists describe a cladogram as "Most Parsimonious" they are suggesting that it is the shortest and hence most plausible phylogenetic tree. D. Some cladists argue that weighting of character states is inappropriate as presumes - a priori - that the investigator is choosing an evolutionary path for which there is no direct evidence. E. In traditional Linnean classification, hierarchical ranks were rigid and hence did not allow for the inclusion of novel interpretations.

What is the basis for evolutionary biologists referring to the Cercozoa as a monophyletic taxon? a- Cercozoans are a very diverse assemblage of single-celled organisms. They exhibit a variety of morphotypes that have been difficult to support as representing a phylogenetic signal. Some are photosynthetic and many are parasitic and occupy a diverse set of environments. b- Establishing the monophyly of the Cercozoa has proven quite challenging as traditional morphological characters have proven to be difficult to properly polarize. As such, the taxon is believed to represent an unnatural assemblage that may not share a common origin. c- Although the question of cercozoan monophyly has been difficult to assess, molecular data strongly supports a close association between these diverse, single-celled protists.

What trait of the angiosperm water vascular system differs significantly from other vascular plants and what is one of the phylogenetic implications for this trait? A. All angiosperms are derived relative to gymnosperms in possessing the ability to produce flowers, which allow for the protection of the developing embryo inside a life sustaining ovary. This advancement in reproductive capacity provided flowering plants with the ability to rapidly diversify, resulting in the extensive world-wide distribution of the clade. B. Unlike gymnosperms, angiosperms possess an additional tissue types known as phloem, which enhances the ability of these plants to circulate larger volumes of water through their vascular network. This ability has provided angiosperms with a much greater ability to colonize diverse habitats, which has led to the great success of the clade. C. Flowering plants possess a series of complex cell structures associated with xylem tissue that are unknown in other plants. One of the major differences is the presence of vessel elements, specialized cells that are absent in all gymnosperms except one taxon, the Gnetophyta, which suggests a closer association with angiosperms. D. Both A & C are correct. E. None of the Above.

Why are green algae best interpreted as a paraphyletic assemblage? a- The most recent phylogenetic analyses show that "green algae" represent successively more derived organisms with coleochaetes representing the closest sister-group to stoneworts + land plants. b- All green algae are more distantly related to each other than any single species is to terrestrial plants. As a result, terrestrial plants tend to be excluded from algae and as such algae cannot be readily viewed as a monophyletic clade. c- The paraphyletic nature of green algae is accepted because algae are not descended from a single common ancestor but instead contain representatives that are more closely related to terrestrial plants than to other algae.

Angiosperms (Anthophytes) have co-evolved with insects and have established a symbiotic relationship that is referred to as a "Pollinator Syndrome". What are some of the benefits of these relationships and how have cheating plants prospered? • A. Pollinator syndromes represent an exclusive relationship that maximizes reproductive success. Plant cheaters have prospered by mimicking insect mates while providing little to no benefit to the insect and taking advantage of the insect as a source of food. • B. Pollinator syndromes represent an exclusive relationship that maximizes reproductive success for the plant and nutritive success for the insect. Plant cheaters have prospered by mimicking insect mates which provide little to no benefit to the insect while taking advantage of the insect as a pollinating agent. • C. Pollinator syndromes benefit each other through an exclusive relationship that maximizes reproductive success for the plant and nutritive success for the insect. Plant cheaters have prospered by mimicking insect mates either by appearance or through odour that provide little to no benefit for the insect while taking advantage of the insect as a pollinating agent. • D. Pollinator syndromes are a significant branch in study of ecology which studies the possible environmental influences that might explain the evolutionary hypotheses that have led to this unique association. We can learn much about organismal specialization by studying this co- evolutionary model and the role that insects played in the evolution of flowering plants.

CBDA

The diagram below exhibits what type of fungal/plant association? What morphological feature helps you to come to your answer (conclusion)? d- The fungal hypha depicted in this diagram is of the arbuscular form as the hypha penetrates the plant cell wall and makes direct contact with the plasma membrane of the plant cell. e- The diagram depicts a mutualistic association of fungal hyphae with the root filament of a plant. This is typical of either the ectomycorrhizal or arbuscular relationship and is characterized by the close association of the fungal hypha with the plant cell. Many plant species have developed a close mutualistic relationship with fungi. One of the most extensive relationships exists between arbuscular fungal hyphae and plant cells. These associations permit the efficient and rapid exchange of materials between the two participants.

Why was the evolution of cuticle so important during the evolution of land plants? A. It protected plants from the damaging effects of high-intensity solar radiation on land. B. It allowed plants to capture sunlight more effectively on land. C. It allowed the efficient exchange of gases, with CO2 entering and O2 leaving. D. It drastically reduced rates of water loss on land. E. Both C & D are correct.

Why was the evolution of cuticle so important during the evolution of land plants? • A. It protected plants from the damaging effects of high-intensity solar radiation on land. • B. It allowed plants to capture sunlight more effectively on land. • C. It allowed the efficient exchange of gases, with CO2 entering and O2 leaving. • D. It drastically reduced rates of water loss on land. • E. Both C & D are correct.

Why is the term "Protista" not considered a viable phylogenetic rank and what traditional example is used to support the unnatural grouping? A. Protists represent a collection of closely related microbes that share a distant phylogenetic relationship. However, more recently we have come to recognize that some protists are more closely related to bacteria than they are with other groups such as plants. B. The phylogenetic history of "Protista" is one of informal classification that is based on general similarity and not due to common descent. This non-phylogenetic construct is not unlike the Linnean classification of elephants and rhinos, which were once grouped together in the unnatural pachyderms. C. Among eukaryotes, the nuclear material is segregated from the cytoplasmic organelles by way of a nuclear membrane. The origins of this membrane are disputed but there is some support for the membrane evolving through a symbiotic association with another prokaryotic organism, such as a bacterium. The rationale for this pathway is carved out of the endosymbiotic theory for the evolution of Eukarya. D. Historically, protists represented a collected of single-celled organisms that could not easily fit into either the plant or animal kingdoms. Little thought was given to common descent, which resulted in the placement of bacteria, such as cyanobacteria, into a close E. With the advent of cladistics, traditional classification has been upended. The result is that many of the historically recognized taxonomic units are no longer valid. In most cases the relationship between the members of the traditional classification have been shown not only to be unrelated to be so distantly related that the traditional classification needs to be utterly abandoned.

D NEED TO FIX

Protists represent a paraphyletic assemblage. What does "Paraphyly" represent and what does this "Paraphyly" suggest about the organisms that we have historically assigned to the now defunct kingdom "Protista"? • A. The term "paraphyly" suggests that the current group is "unnatural" or not monophyletic. This simply means that all members of that group cannot trace their origins to a single common ancestor. With respect to the former kingdom "Protista", we can conclude that this group is not a "natural group" and hence does not trace its origins to a common point of origin. In other words, some "protists" are more closely related to other taxa than they are to other currently recognized "protists". • B. The term "paraphyly" suggests that the current group is represents a "natural group" or a group that is monophyletic. This simply means that all members of that group can trace their origins to a single common ancestor. With respect to the former kingdom "Protista", we can conclude that this group is a "natural group" and hence can trace its origins to a common point of origin. In other words, some "protists" are more closely related to other taxa than they are to other currently recognized "protists". • C. The nomenclature (language) associated with testing phylogenetic hypotheses depends on a logical structure that includes a number of possible classifications that are placed into three distinct groupings: monophyletic, paraphyletic, & polyphyletic taxonomic associations. Protists represent a taxonomic unit that falls into one of these categories. • D. A paraphyletic group suggests that not all members of that group can trace their origins to a single ancestral node on a phylogenetic tree. With respect to the former kingdom "Protista", we can conclude that this group is not a "natural group" and hence does not trace its origins to a common point of origin. In other words, some "protists" are more closely related to other taxa than they are to other currently recognized "protists".

DACB

Describe how genetic changes might accumulate over a number of generations and what this accumulation might mean with respect to evolution? • A. Genetic changes are due simply to chance and likely will accumulate over a period of time. These changes are the result of mutations that will always lead to a more well adapted organism which will increase its survivability and fecundity. • B. Genetic changes may lead to phenotypic differences. These changes will likely alter each individual's fitness, which may impact on its survival rate and influence its fecundity. As changes accumulate and if reproductive success continues new species may evolve. • C. Genetic change is the key to evolution. Darwin described it even without having the knowledge of the molecular basis for evolution. Biologists today explore evolution using a number of techniques that can trace back to Darwin's epic work. • D. Genetic changes may lead to behavioural and or morphological differences. These changes will likely alter each individual's fitness, which may impact on its survival rate and influence its fecundity. As changes accumulate and if reproductive success continues it is possible that new species may evolve.

DBCA

Evolution can be best described as being the by-product of ... • A. Chance. • B. Natural Selection. • C. Accumulation of adaptive traits. • D. None of the above. • E. A, B, & C all contribute to evolution.

The two cladograms below differ on what basis? Select the statement(s) that best describe(s) the phylogenetic differences between the two cladograms. A. Cladogram (i) has 6 steps including one autapomorphy and 5 synapomorphies at various locations on the tree, whereas cladogram (ii) requires 8 steps to resolve, including a reversal and a convergence. B. Both cladograms present an hypothesis of phylogenetic relationships for taxa "A" through "E". Cladogram (ii) is more parsimonious than cladogram (i). C. Cladogram (i) & (ii) differ in that the latter has taxon "B" as the out-group taxon, whereas the former has taxon "A" as the out-group taxon. D. All of the above. E. All except choice B is correct.

What did Linnaeus base his classification on and how does it differ from the modern phylogenetic methodology. • A. The hypothesis that life has more than one origin. • B. That multiple generations arose independently. • C. Linnaeus based his classification on Occam's razor that the simplest path to the evolution of a group must be the correct path. • D. Linnaeus based his classification on phenetics - that similarity of appearance meant close association of different species. • E. None of the Above.

What is meant when we say that liverworts, hornworts and mosses are polytomic? A. That all three are derived from a separate ancestor and are thus not closely related. B. That all three represent primitive non-vascular plants that lack polymorphism. C. That all three primitive plants evolved during the Carboniferous and represent a polymorphic grade of primitive plant. D. That all three taxa are derived relative to green algae. E. That all three taxa are so closely related that it is difficult to determine which two are

Why should we not be exclusively concerned with increasing levels of CO2 in our atmosphere as it pertains to climate change? • A. Focusing on CO2 undermines the influence of other gases in our atmosphere that might have at least as significant an impact on our climate. • B. The atmosphere of our planet currently has a CO2 concentration of just under 400ppm which is about half the concentration on earth during the Carboniferous period. • C. Worrying exclusively about CO2 limits our ability to explore other atmospheric contributors to climate change and oversimplifies our response. • D. The earth is dynamic system which is continuously changing albeit in time scales that far exceed of human lifetime. • E. All of the Above except "B".

Why would wind pollination not be advantageous in a tropical rain forest? A. The sparse vegetation would limit the distribution potential of the pollen. B. Wind is not effective in a dense forest because the plants are too short to be able to capture the wind-blown pollen. C. There are too many animals that would easily make a meal of the pollen. D. Wind is only effective in cold environments. E. The densely packed vegetation reduces the ability of wind to blow pollen in a sufficiently widespread manner.

What specific ability provides the fungus of the Basidiomycota with a major role in the decomposition of woody plants? d- Many fungi are able to breakdown complex organic materials, but basidiomycetes are exceptional in their ability to breakdown nitrogen rich compounds. With this ability, basidiomycetes serve an important role in the nitrogen cycle. e- Woody plants require a great deal of effort to breakdown and only one type of fungus is able to fully render woody tissue inert. Without basidiomycetes, woody plants would remain undisturbed after death and its tissues would not be properly recycled. f- Although most fungi represent saprobes, basidiomycetes are exceptional in their ability to breakdown not only cellulose but lignin, which are responsible for the tough fibrous tissue that makes up woody plants.

Cnidarians are best known as Jellyfish. However, there are two main parts to the cnidarian lifecycle - the medusa stage, which is what we generally recognize as a jellyfish, and the polyp stage, which is generally recognized as coral and/or anemones. How does the lifecycle of cnidarians differ between the polyp and medusa stages and which lifecycle is responsible for sexual reproduction? g- Cnidarians are an ancient lineage and may predate many animals as the Ediacaran faunae are believed to have been members of this clade. Among Cnidaria, jellyfish are perhaps the most readily recognized members of the clade and can present a threat to human activities as many species can be quite toxic and even deadly. Corals on the other hand are generally more fully appreciated by human society and pose less of a direct threat to human activities in the shallow marine environments where they are common. h- Cnidarians possess two parts to their lifecycle, with the medusa serving as the dispersal stage and the polyp serving as the sessile stage. However, the major difference between the two stages is that the medusa (jellyfish) represents the sexually active stage, whereas the poly (coral) represents the asexual phase of the life cycle. It is only in the medusa stage that haploid germ cells are produced which then fuse to produce a diploid zygote that can then grow into a polyp. The medusae are then released from a specialized reproductive polyp. i- The lifecycle of cnidarians is complex as it moves through a polyp and medusa stage. In some species, the most common stage is the medusa (jellyfish), whereas in other species, the polyp (coral/anemone) stage is more prevalent. Regardless as to which stage is more common all cnidarians will go through both stages throughout one lifecycle. The medusa stage is primarily used for increasing the dispersal of a population as it is on the stage that is free-swimming.

What is meant by the statement that sponge cells are totipotent? g- The cells of all organisms have some capacity for differentiation. Even in higher vertebrates, embryonic cells can develop into a wide range of tissue types. However, this capacity for totipotency is lost as cells begin to divide in the later stages of embryogenesis and in higher vertebrates totipotency is effectively lost beyond the gastrula stage. h- Although sponges are recognized as members of the animal clade, they retain a number of plesiomorphic abilities including the ability to regenerate. In effect, the cells that make up a mature sponge are independent and can exist on their own. This means that throughout the life cycle of a sponge, sponge cells remain totipotent. i- Totipotency is the ability of a given cell to generate any number of possible tissue types. Embryonic stem cells retain this ability and as such are extremely valuable in genetic research. The ability to use stem cells to replace damaged tissues in diseased organs is an area of medicine that continues to expand, with the hope that many debilitating diseases can be cured.

Although generally accepted as primitive animals, sponges are uniquely adapted to serve their marine existence. Examine the options (choices) provided and select the one that most accurately describes the feeding pattern in a typical marine sponge? g- Sponges possess a collection of cells that when grouped together result in the mature sponge body. These cells are referred to as choanocytes and resemble very closely the anatomical structure of a single-celled protist known as a choanoflagellate. This similarity in morphology has led most evolutionary biologists to suggest a close association between choanoflagellates and the common ancestor of all animals. h- Feeding in sponges is passive and relies on the ocean currents to provide all of the nourishment. However, the small flagella associated with each choanocyte in the sponge's body. The beating of these flagella creates a current that draws water in through the sponge's pores and permit food particles to be strained by the cells while funnelling the water out through the large common opening known as the osculum. i- Sponges feed in a manner that relies primarily on ocean currents. However, the feeding is not entirely passive, as the flagellated choanocytes create a strong current around the body of the sponge that draws water in through the various pores along the sponge's outer margin and into the spongocoel. Food particles are also drawn in and are trapped by the small cells lining the spongocoel, with the water allowed to continue through the body of the sponge and out through the osculum - a large opening at the free end of the sponge.

The correct option responds to the question completely including identifying the role of the medusa as the sexual phase of cnidarians. One of the remaining options is limited because it fails to point out the role of the medusa, whereas the other discusses the impact of cnidarians with respect to their impact on human activities. Although the content of this response if valuable it does not respond to the question. Lophotrochozoans grow by the addition of segments, which differentiates them from ecdysozoans that grow through a molt. Aside from growth, what attribute unites all lophotrochozoans? j- The difficulty in determining the monophyly of the Lophotrochozoa has to do with the very disparate nature of their adult anatomies as worms and molluscs are indeed quite different. However, they all share a trocophore larval stage. k- Presently all lophotrochozoans are categorized as protostomes. However, at one time, some of its members were thought to be more closely associated with the deuterostomes. This included a clade previously known as the lophophorates. l- All lophotrochozoans are unified on the basis of the lophophore, a structure associated with feeding. In addition, most share the presence of a unique larval form referred to as a trocophore.

Flatworms are one of the most diverse members of the Lophotrochozoa. Although they are grouped within this assemblage they lack one of the diagnostic characters that unite all Lophotrochozoa. What is this character? j- Among the Lophotrochozoa, there are two key features that describe a common ancestry. One of these and perhaps the most readily described is the lophophore, which is associated with feeding in the larval stage. Surprisingly flatworms lack this derived character. k- Diagnosing a clade is replete with uncertainty. Characters may be re-defined and new finds may cause synapomorphies to be rendered as plesiomorphies. This is precisely what has happened in the assessing flatworm ancestry. l- Flatworms represent a very diverse assemblage of lophotrochozoans. Many are free living, but most are parasitic, with a significant number being problematic for human health. Tape worms for example, are significant health issue in underdeveloped countries.

Among all of the lophotrochozoans, perhaps the most intriguing clade are represented by the Mollusca. Among molluscs, we find a number of distinct morphologies, but perhaps the most intriguing is that of the cephalopods. What behaviour of cephalopods has provided biologists with a number of additional questions about intelligence? j- Cephalopods have had a dubious history. More often, when not being used as food, they are being characterized as evil creatures that can attain monstrous sizes - the giant squid and the fantastical "Kraken". However, today, we know that these lophotrochozoans are just another creature that faces the same challenges all living creatures face in their struggle for survival. k- Until the last decade, cephalopods were thought of nothing more than marine creatures with some infamous literary applications - i.e., the "Kraken". However, recent studies have suggested that certainly in the octopus family there is a great deal more to their abilities than previously believed. It has been noted that an octopus can learn to solve a problem, which denotes a degree of intelligence that is much more mammalian than previously expected. l- Among all cephalopods, the octopus is by far the most well studied. The groups is noted for having exceptional eye-sight even matching or possibly exceeding our own. However, what has really drawn the attention of scientists is an apparent intellectual ability that has been recently observed, which is thought to match the intellectual skills of higher vertebrates.

The earliest true arthropods are represented by which taxa and how can we be confident of this relationship? m- MyriapodsaretheearliestmembersofArthropoda.Thisisevidentbytheirjointedlimbs-a trait that they share with all other arthropods. n- Arthropoda is the most diverse lineage of animals on the planet with well over 1,000,000 species. Among these many species, one clade, the Myriapoda, which includes the millipedes and centipedes, is representative of the most basal members. o- The ability to molt unites the myriapods with arthropods. Only these two clades are capable of molting during their development.

Why are some basal ecdysozoans, such as onychophorans and tardigrades believed to represent the sister-clade to Arthropoda? m- TheEcdysozoarepresentsacladethatincludes:Nematoda,Onychophora,Tardigrada,& Arthropoda. Among these taxa, the onychophorans are believed to be the sister-taxon to Arthropoda. Although, wormlike in appearance these basal ecdysozoans have the unique ability to molt that is common to all Ecdysozoa. n- Tardigrades and onychophorans share with arthropods a unique form of reproduction that is diagnostic of the entire clade. All of these taxa lay eggs that hatch into miniature versions of the adults with no larval stage. o- Arthropods possess jointed appendages which are unique among Ecdysozoa. Other more primitive members such as nematodes lack appendages and a few taxa such as onychophorans and tardigrades possess unjointed limbs. However, it is hypothesized that the unjointed limbs of these taxa are reflective of a step that led to the Arthropoda.

Are all deuterostomes chordates? How do we distinguish between deuterostomes and protostomes? p- Yes, all deuterostomes are members of Chordata. This association is due to the presence of a number of chordate features that are also shared with basal deuterostomes such as marine echinoderms. q- Deuterostomes are a diverse and ancient lineage of animals that represents the sister-taxon to the protostomes. The divergence occurred well back near the origin of animals sometime during the Cambrian. One method used to differentiate between the two clades is embryonic development. r- No, not all deuterostomes are chordates, although most do fall into that clade. Nevertheless, while some deuterostomes are invertebrates, they are still more closely related to chordates than to other invertebrates on the basis of embryonic development.

What are the attributes that can be used to diagnose Chordata and are there any taxa that fail to exhibit at least one of these diagnostic traits in one part of its lifecycle? p- The presence of paired appendages (fins or limbs), a spinal cord, pharyngeal gills slits and a notochord are the key attributes that diagnose all chordates. All chordates except urochordates possess all of these attributes during their lives. q- Chordata are a large taxonomic unit that includes the subordinate clades, Urochordata, Cephalochordata, and Vertebrata. All members of Chordata include all four of the key diagnostic traits. r- There are four key attributes that are shared by chordates: Pharyngeal gill slits, notochord, dorsal hollow nerve tube, and a muscular post-anal tail. Some basal chordates such as Urochordata only express a single trait (gill slits) in the adult form.

What specialized feature of the radial arms of some echinoderms (starfish), is unique to this taxon and what is its purpose? p- Starfish possess a specialized respiratory system that is maintained through an elaborate water vascular system, which facilitates oxygen exchange. q- Some basal deuterostomes have the ability to reproduce through parthenogenesis and as such do not require a mate to reproduce. This is a unique feature of this clade. r- Among some deuterostomes, such as starfish, a unique water vascular system has developed, which functions as locomotory structure.

How are the hierarchical ranks Craniata (craniates) and Vertebrata (vertebrates) viewed and what are the major differences between Craniata (craniates) and Vertebrata (vertebrates)? s- Craniates are a more inclusive grouping that includes hagfish plus lampreys and all other gnathostomes (jawed vertebrates). In addition, aside from a number of physiological differences between the two groups, craniates lack the ossification necessary to support a true vertebral column. t- Vertebrates are a much more inclusive grouping of animals that includes all living organisms that share a closer ancestry with Craniata than with any other member of Animalia. There are a number of physiological and morphological differences that separate the two clades, including the presence of true vertebral column in Vertebrata. u- Throughout the evolutionary history of Animalia, structural complexity has been the hallmark of the clade. Today, vertebrates are an incredibly diverse assemblage that includes both jawless and jawed forms.

What is it about the appendicular skeleton in sarcopterygians that demonstrates the components necessary for the development of the tetrapod limb and supports the close sister-group association between derived sarcopterygians and the earliest tetrapods? s- Among sarcopterygians, fish such as Eusthenopteron, or more derived forms such as Tiktaalik, a fully formed humerus along with the more distal elements such as the radius and ulna are present. These elements are recognized homologues of the tetrapod limb and hence support a close sister-group arrangement between these fish and the first tetrapods. t- During the Devonian, dramatic changes to the ecosystem were taking place, including a noticeable decrease in oxygen levels. It is hypothesized that this reduced oxygen contributed to anoxic environments, notably in shallow ponds, that might have triggered the evolution of tetrapods. u- Many Devonian vertebrates have been linked to the evolution of tetrapods, notably the Canadian fossil Tiktaalik. This stem tetrapod possesses a number of characteristics that speak to its tetrapod affinities. However, even Tiktaalik lacks the true digits that distinguish all tetrapods.

What is the ontogenetic process by which neural crest tissue is formed in the development of a vertebrate embryo? s- Neural crest tissue forms on a region of ectodermal tissue referred to as the neural plate. As the ectoderm begins to fold in on itself to form the neural tube, a region associated with the folding separates and transforms into neural crest tissue. t- Neural crest tissue is a novel tissue type that is found only in higher vertebrates. It is primarily responsible for the development of the brain and other associated structures including sensory organs. u- Embryonic development in vertebrates is quite complex and undergoes a number of reorganizations. During an early stage in neurulation, the neural crest tissue is formed. Once formed this tissue becomes associated with various sensory structures as well as the formation of the jaws.

What is the current understanding with respect to the phylogenetic placement of turtles in the reptile family tree and why was this conclusion so heretical when first proposed? v- Today, turtles are recognized as diapsid reptiles, which may share a closer affinity to archosaurs (crocodiles and birds) than they share with lepidosaurs (lizards and snakes). However, although this discussion continues, the most significant finding, around 20 years ago, was that turtles should even be considered as diapsids instead of belonging to an ancient lineage of amniotes known as parareptiles. This novel hypothesis was based on developmental and morphological arguments and was heretical at the time because turtles lack the typical temporal fenestration known in all extant reptiles. A few years after researchers at UTM and Chicago had presented this heretical view, independent researchers, using molecular data, supported that initial find and the heresy of the 1990s is now recognized as the most convincing argument for turtles origins. w- The origin of turtles has been filled with challenges and controversy. For most of the 19th and 20th centuries, turtles were viewed as a problematic taxon with very ancient origins. However, the challenge was also that the anatomy of turtles is so specialized that it made character polarization difficult. In addition, determining a plausible out-group to help verify character polarity and homology added another degree of complexity. By the late 20th century, turtles had been assigned as the last living representative of an enigmatic group known as the Parareptilia, which had been dominant during the Permian, but had been extinct since the Triassic, except for their descendants the turtles. It was not until the advent of molecular analysis that turtle origins would be fully resolved. x- Turtles represent a vet diverse clade that includes aquatic and terrestrial forms, along with a large number of amphibious representatives. Today, turtles are known from all continents except Antarctica and can be found in temperate and tropical environments. Some aquatic members are so specialized that they are effectively warm-blooded. However, the most intriguing aspect of turtle anatomy is the ability to recoil into a shell, a behaviour that required some very significant changes to the turtle anatomy, notably the placement of the should and pelvic girdles inside the rib cage, a condition that is in sharp contrast to all other extant amniotes. Regardless of the phylogenetic position of this enigmatic and curious taxon, turtles remain a successful taxon that should survive well into the next millennium.

The Evolution of the tetrapod limb has been a focus of evolutionary research for decades. Ever since the link between sarcopterygian fish, such as Eusthenopteron, and tetrapods, such as Ichthyostega, were established, comparative anatomists and evolutionary biologists have argued over how digits evolved from the dermal fin rays of fish. What is the latest interpretation regarding the evolution of tetrapod digits and what are the morphological consequences of the latest view? v- Phylogenetic studies of the development of the fish fin and the tetrapod hand/foot suggest that tetrapod digits are a novel feature that evolved with the evolution of tetrapods. As such the sarcopterygian fish from which tetrapods are believed to have evolved lack the genetic coding necessary to produce tetrapods digits. w- Recent studies involving fish and tetrapods has concluded that a change in the developmental timing of the fin/limb bud and specifically the apical ectodermal ridge (AER) suggests that fish already have the capacity to grow digits but fail to do so. Hox genes, therefore, play a role in altering the timing and expression of genes that result in the formation of digits in tetrapods, which unlike the rays of the fish fin are endochondral in origin as opposed to dermal in fish. x- The origin of the tetrapod limb and specifically the evolution of tetrapod digits have been at the forefront of evolutionary studies for decades. The challenges are associated with whether or not the ability to grow digits is a novel tetrapod feature or simply a change in the developmental timing of pre-existing genes. More recent work has explored the role of Hox genes in the development of tetrapod digits and there is hope that a conclusion may reached soon.

Mammals are separated into a number of categories or extant clades. What are these clades and what are the distinguishing features associated with these clades? v- There are three groups of mammals, the placentals, marsupials, and monotremes. These three taxa differ anatomically and physiologically. Marsupials are restricted to Australasia except for one clade in the Americas (i.e., Opossum), whereas monotremes are exclusively Australasian. w- The most basal extant mammalian group is the Monotremata, with marsupials and placentals both belonging to a more inclusive grouping known as Theria. All mammals can trace their earliest origins to the Triassic and possibly even the Late Permian, but most modern mammalian clades likely evolved sometime in the Cenozoic. x- Modern mammals belong to three distinct clades: the Eutheria, Marsupialia, & Monotremata. All three give birth to live young, but only eutherians nurse fully developed young. Marsupials give birth to embryonic young that then complete their development in a pouch and monotremes lay leathery eggs and lack proper mammary glands.

In the diagram below, a fungal lifecycle is displayed. What lifecycle is depicted and how can this lifecycle be distinguished from that which is depicted by the unicellular Chytridiomycota? d- This lifecycle is found in the mushroom class and is derived relative to the more primitive Chytridiomycota fungal lifecycle by exhibiting a more complex series of steps in its reproductive phase - leading to stage where mating types do not fuse their nuclei until the fruiting body has been produced. e- This lifecycle is typical of the Basidiomycota, a fungus that has a complex lifecycle that separates plasmogamy from karyogamy - a condition that occurs simultaneously within the more primitive Chytridiomycota. f- All fungi exhibit an alternation of generation in their lifecycle, but the Basidiomycota are specialized relative to other fungi in that they produce a very prominent fruiting body that we refer to as the mushroom.

What is the primary difference associated with growth between members of the Lophotrochozoa and those of the Ecdysozoa? m- MembersoftheEcdysozoagrowbymoltingorthesheddingofthecuticle.Most lophotrochozoans grow by adding concentric growth rings or segments. In addition, ecdysozoans possess a group of steroids associated with molting known as ecdysteroids. n- The two groups differ in a number of critical ways. Most notably the larval form present in lophotrochozoans is unique to the clade and is referred to as the trocophore larva. o- The ability to grow by adding segments is the primary means of growth exhibited by ecdysozoans. All lophotrochozoans are unsegmented and hence are unable to grow in that manner.

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