GBIO 153 Exam 1

A population has 700 individuals, 85 of genotype AA, 320 of genotype Aa, and 295 of genotype aa. What are the frequencies of alleles A and a?

# of individuals= 85BB 320Bb 295bb # of B alleles= 2(85) + 320 + 0= 490 B alleles # of b alleles= 0 + 320 + 2(295) = 910 b alleles Total= 1400 total alleles 490/ 1400= 0.35 so 35% are B 910/1400= 0.65 so 65% are b

(a) Which species concept(s) could you apply to both asexual and sexual species? (b) Which would be most useful for identifying species in the field? Explain.

(a) All except the biological species concept (b) morphological species concept because based on appearance of organism

How does evolution account for (a) the similar mammalian forelimbs with different functions shown in Figure 19.16 and (b) the similar forms of the two distantly related mammals shown in Figure 19.18?

(a) Despite their different functions, the forelimbs of different mammals are structurally similar because they all represent modifications of a structure found in the common ancestor. (b) This is a case of convergent evolution. The similarities between the sugar glider and flying squirrel indicate that similar environments selected for similar adaptations despite different ancestry.

Explain what is meant by the genome of an organism

A genome is the complete set of genetic information in an organism. It provides all of the information the organism requires to function. In living organisms, the genome is stored in long molecules of DNA called chromosomes.

Distinguish between phenotype and genotype

A genotype refers to the genetic characteristics of an organism. A phenotype refers to the physical characteristics. For example, having blue eyes (an autosomal recessive trait) is a phenotype; lacking the gene for brown eyes is a genotype.

Fossils show that dinosaurs originated between 200 and 250 million years ago. Would you expect the geographic distribution of early dinosaur fossils to be broad (on many continents) or narrow (on one or a few continents only)? Explain.

At the time that dinosaurs originated, Earth's landmasses formed a single large continent, Pangaea. Because many dinosaurs were large and mobile, it is likely that early members of these groups lived on many different parts of Pangaea. When Pangaea broke apart, fossils of these organisms would have moved with the rocks in which they were deposited. As a result, we would predict that fossils of early dinosaurs would have a broad geographic distribution (this prediction has been upheld).

What factors promote adaptive radiations?

Adaptive radiation often happens after mass extinctions because it allows animals to occupy different niches and ecological roles and evolve because of it. Also, the migration to a new habitat in which few or different predators exist promotes adaptive radiation. Species that adapt can promote adaptive radiation in others by becoming food sources.

Summarize evidence that the yup flower-color locus acts as a prezygotic barrier to reproduction in two species of monkey flowers. Do these results demonstrate that the yup locus alone controls barriers to reproduction between these species? Explain.

Alleles at yup locus can pollinator choice, which provides primary barrier to interspecific mating. Nevertheless, experiment does not prove that yup locus alone controls barriers to reproduction between M. lewisii and M. cardinalis; other genes might enhance effect of yup locus or cause entirely different barriers to reproduction

Explain why natural selection is the only evolutionary mechanism that consistently leads to adaptive evolution in a population.

Although gene flow and genetic drift can increase frequency of advantageous alleles in a population, they can also decrease the frequency of advantageous alleles. Only natural selection can consistently increase the frequency of advantageous alleles.

Explain how the following statement is inaccurate: "Antibiotics have created drug resistance in MRSA."

An environmental factor such as a drug does not create new traits, such as drug resistance, but rather selects for traits among those that are already present.

VISUAL SKILLS Consider a population in which heterozygotes at a certain locus have an extreme phenotype (such as being larger than homozygotes) that confers a selective advantage. Compare this description to the three types of selection depicted in Figure 21.13. Does this situation represent directional, disruptive, or stabilizing selection? Explain your answer.

The three modes of natural selection are defined in terms of selective advantage of different phenotypes, not different genotypes, thus, the type of selection represented by heterozygote advantage depends on the phenotype of the heterozygote, in this question, because heterozygous individuals have a more extreme phenotype than either homozygote heterozygote advantage represents directional selection

Speciation can occur rapidly between diverging populations, yet the time between speciation events is often more than a million years. Explain this apparent contradiction.

The time between speciation events includes (1) length of time it takes for populations of newly formed species to begin diverging reproductively from one another (2) time it takes for speciation to be complete once this divergence begins. Although speciation can occur rapidly once populations have begun to diverge from one another, it may take millions of years for that divergence to begin.

Describe evolution as a process of descent with modification

Darwin defined evolution as "descent with modification," the idea that species change over time, give rise to new species, and share a common ancestor. The mechanism that Darwin proposed for evolution is natural selection.

The frequency of allele a is 0.45 for a population in Hardy-Weinberg equilibrium. What are the expected frequencies of genotypes AA, Aa, and aa? A locus that affects susceptibility to a degenerative brain disease has two alleles, V and v.

Freq of allele 'a' is 0.45Freq of allele 'A' is 0.55 (q=1-0.45 = 0.55)Expected genotype frequenciesAA P2 = 0.3025Aa 2pq = 0.495aa q2 = 0.2025

Given that changes in morphology are often caused by changes in the regulation of gene expression, predict whether noncoding DNA is likely to be affected by natural selection. (Review Concepts 15.2 and 15.3.)

From genetics, we know that gene regulation is altered by how well transcription factors bind to noncoding DNA sequences called control elements. Thus, if changes in morphology are often caused by changes in gene regulation, portions of noncoding DNA that contain control elements are likely to be strongly affected by natural selection

Distinguish genetic drift from gene flow in terms of (a) how they occur and (b) their implications for future genetic variation in a population.

Genetic drift results from chance events that cuase allele frequencies to fluctuate at random from generation; within a population, this process tends to decrease genetic variation over time. Gene flow is the exchange of alleles between populations, a process that can introduce new alleles to populations and hence may increase its genetic variation (albeit slightly, since rate of gene flow are often low)

Explain how organisms inherit traits from their parents

Genetic inheritance occurs due to genetic material, in the form of DNA, being passed from parents to their offspring. When organisms reproduce, all the information for growth, survival, and reproduction for the next generation is found in the DNA passed down from the parent generation

Distinguish between homologous and analogous characters

Homologous structures are structures that are similar in related organisms because they were inherited from a common ancestor. These structures may or may not have the same function in the descendants. ... Analogous structures are structures that are similar in unrelated organisms.

DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that 1. humans and chimpanzees share a relatively recent common ancestor. 2. humans evolved from chimpanzees. 3. chimpanzees evolved from humans. 4. convergent evolution led to the DNA similarities.

Humans and chimpanzees share a relatively recent common ancestor.

Review the process of meiosis in Figure 10.8. Describe how an error during meiosis could lead to polyploidy.

If all homologs failed to seperate during anaphase I of meiosis, some gametes would end up with extra set of chromosomes. If gamete with extra set of chromosomes fused with normal gamete, triploid would result; if two gametes with extra set of chromosomes fused with each other, tetraploid would result.

What factors can support the long-term stability of a hybrid zone if the parent species live in different environments?

If the hybrids are selected against, the hybrid zone could persist if individuals from the parent species regularly traveled into the zone, where they mate to produce hybrid offspring. If hybrids are not selected against, there is no cost to the continues production of hybrids, and large number of hybrid offspring may be produced. However, natural selection for life in different environment may jeep he gene pools of the two parent species distance, this preventing the loss ( by fusion) of the parent species and once again causing the hybrid zone to be stable over time.

Contrast allopatric and sympatric speciation. Which type of speciation is more common, and why?

In allopatric speciation, new species forms while in geographical isolation from its parent species; in sympatric speciation, new species forms in absence of geographic isolation. Geographic isolation reduces gene flow between populations, where ongoing gene flow is more likely in sympatric populations. So, sympatric speciation is less common than allopatric speciation.

Why is it likely that Hox genes have played a major role in the evolution of novel morphological forms?

In animal embyros, Hox genes influence the development of structures such as limbs and feeding appendages. As a result, changes in these genes or in the regulation of these genes are likely to have major effects on morphology

Summarize how mass extinctions affect the evolutionary history of life.

In each of the five mass extinctions documented in the fossil record, 50% or more of marine species became extinct, as did large numbers of terrestrial species. As a result, a mass extinction alters the course of evolution dramatically, removing any evolutionary lineages and reducing the diversity of life on Earth for millions of years. A mass extinction can also change ecological communities by changing the types of organisms that live in them.

Consider two species that diverged while geographically separated but resumed contact before reproductive isolation was complete. Predict the outcome over time if the two species mated indiscriminately and (a) hybrid offspring survived and reproduced more poorly than offspring from intraspecific matings or (b) hybrid offspring survived and reproduced as well as offspring from intraspecific matings.

a. Reinforcement could occur. If it did, natural selection would cause prezygotic barriers to reproduction between parent species to strengthen over time, decreasing production of unfit hybrids, leading to completion of the speciation process b. Indiscriminate mating between parent species would lead to the production of large numbers of hybrid offspring. As these hybrids mated with each other and with members of both parent species, gene pools of parent species could fuse over time, reversing speciation process.

Explain the logic of using shared derived characters to infer phylogeny.

all features of organisms arose at some point in the history of life in the group in which a new feature first arose that feature is a shared derived character unique to that clade that group in which each shared derived character first appeared can be determined and the resulting nested pattern can be used to infer evolutionary history

Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent? 1. habitat isolation t 2.temporal isolation 3.behavioral isolation 4.gametic isolation

behavioral isolation

Compare Figure 10.11 with Figure 22.19. What cellular process could cause the hybrid chromosomes in Figure 22.19 to contain DNA from both parent species? Explain

crossing over

Your measurement indicate that a fossilized skull you unearthed has a carbon- 14/ carbon-12 ratio about 1/16 that of the skulls of present-day animals. What is the approximate age of the fossil skull?

four half lives: 5730 X 4= 22,990 year

Which of the following factors would not contribute to allopatric speciation? 1.A population becomes geographically isolated from the parent population. 2.The separated population is small, and genetic drift occurs. 3.The isolated population is exposed to different selection pressures than the ancestral population. 4.Gene flow between the two populations is extensive.

gene flow between the two populations is extensive

If the nucleotide variability of a locus equals 0%, what are the gene variability and number of alleles at that locus? g 1. gene variability=0%; number of alleles=0 2.gene variability=0%; number of alleles=1 gene 3.variability=0%; number of alleles=2 gene 4.variability>0%; number of alleles=2

gene variability= 0%; number of alleles= 1

Why was the five-kingdom system abandoned for a three-domain system?

genetic data indicated that many prokaryotes differed as much from each other as they did from eukaryotes this indicated that organisms should be grouped into three super kingdoms or domains these data also indicated that the previous kingdom Monera did not make biological sense and should be abandoned later genetic and morphological data also indicated that the former kingdom protista should be abandoned because some protists are more closely related to plants fungi or animals

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa.Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from 1.genetic drift. 2.gene flow. 3.nonrandom mating. 4.directional selection.

genetic drift

Why is it necessary to distinguish homology from analogy to infer phylogeny?

homologous characters result from shared ancestor as organisms diverge over time some of their homologous characteristics will also diverge the homologous characters of organisms that diverged long ago typically differ more than do the homologus charateristics can be used to infer phylogeny. in contrast analogous characteristics of organisms result from convergent evolution not shared ancestry and hence can give misleading estimates

Natural selection changes allele frequencies because some survive and reproduce better than others. 1.alleles 2.loci 3.species 4.individuals

individuals

Explain the chromosomal basis of inheritance

is the idea that genes are located on chromosomes as well as the idea that the behavior of chromosomes during Meiosis accounts for Mendel's Laws of Segregation and Independent Assortment.

Explain the process of speciation

is the process by which new species form. It occurs when groups in a species become reproductively isolated and diverge. In allopatric speciation, groups from an ancestral population evolve into separate species due to a period of geographical separation.

Is allopatric speciation more likely to occur on an island close to a mainland or on a more isolated island of the same size? Explain your prediction.

it is less likely to occur on island near mainland than on isolated island of same size. We expect this result because continued gene flow between mainland populations and those on a nearby island reduces chance that enough genetic divergence will take place for allopatric speciation to occur.

According to the punctuated equilibria model, 1.natural selection is unimportant as a mechanism of evolution. 2.given enough time, most existing species will branch gradually into new species. 3.most evolution occurs in sympatric populations. 4.most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species

The largest unit within which gene flow can readily occur is a 1.population. 2.species. 3.genus. 4.hybrid.

species

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating 1. the bottleneck effect. 2. disruptive selection. 3. frequency-dependent selection. 4.stabilizing selection.

stabilizing selection

The relative lengths of the frog and mouse branches in the phylogenetic tree in Figure 20.13 indicate that.. 1. frogs evolved before mice 2. mice evolved before frogs 3. the homolog evolved more rapidly in the mouse lineage 4. the homolog evolved more slowly in the mouse lineage

the homolog evolved more slowly in the mouse lineage

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds were reclassified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification? 1.The two forms interbreed often in nature, and their offspring survive and reproduce well. 2.The two forms live in similar habitats and have similar food requirements. 3.The two forms have many genes in common. 4.The two forms are very similar in appearance.

the two forms interbreed often in nature, and their offspring survive and reproduce well

What are hybrid zones, and why can they be viewed as "natural laboratories" in which to study speciation?

they are regions in which members of different species meet and mate, producing some offspring of mixed ancestry. This can be viewed as natural laboratory because scientist can directly observe factors that cause reproductive isolation

Explain how new body forms can originate by heterochrony.

this can cause a variety of morphological changes. For example, if the onset of sexual maturity changes, a retention of juvenile characteristics may result. Small genetic changes lead to substantial changes in morphology

Explain the role of gene flow in the biological species concept.

this concept states that a species is a group of populations whose members interbreed, thus, gene flow occurs between populations of a species; the absence of gene flow plays a key role in the formation of new species, as well as in keeping them apart once their potential to interbreed has been reduced

If you were using cladistics to build a phylogentic tree of cats, which of the following would be the best outgroup? 1. wolf 2. domestic cat 3. frog 4. leopard

wold

Can factors that cause sympatric speciation also cause allopatric speciation? Explain.

yes: polyploidy, habitat shifts, sexual selection

Based on the tree in Figure 20.4 are leopards more closely related to badgers or wolves, or are they equally related to those two species? explain

In the image shown leopards are the sister taxon to a group consisting of the family Mustelidae (which include badgers) and the family Canidae (which includes wolves). Since members of a sister group are each others closest relatives, leopards are equally related to badgers and wolves.

Suppose that an invertebrate species was lost in a mass extinction caused by a sudden catastrophic event. Would the last appearance of this species in the fossil record necessarily be close to when the extinction actually occurred? Would the answer to this question differ depending on whether the species was common (abundant and widespread) or rare? Explain.

In theory, fossils of both common and rare species would be present right up to the time of the catastrophic event, then disappear. Reality is more complicated because the fossil record is not perfect. So, the most recent fossil for a species might be a million years before the mass extinction even though the species did not become extinct until the mass extinction. This complication is especially likely for rare species because few of their fossils will form and be discovered. Hence, for many rare species, the fossil record would not document that the species was alive immediately before the extinction

Humans and chimpanzees are sister species. Explain what this statement means.

It indicates that we share a more recent common ancestor with chimpanzees than we do with any other living primate species.

What is a molecular clock? What assumption underlies the use of a molecular clock?

It is a method of estimating the actual time of evolutionary events based on the number of base changes in orthologus genes It is based on the assumption that the regions of genomes being compared evolve at constant rates

How might secondary sex characteristics in males differ from those in females in a species in which females compete for mates?

It is likely that the females of such species would be larger more colourful, endowed with more elaborate ornamentation. and more apt to engage in the behaviors intended to attract mates or prevent other members of their sex from obtaining mates.

How can the Darwinian concept of descent with modification explain the evolution of such complex structures as the vertebrate eye?

It is the idea that complex structures do not develop overnight, they become more complex in increments of adaptations and evolution

What might a fossil record of life today look like?

It would include many organisms with hard body parts, but might not include some species we are very familar with, such as those that have geographic ranges and small population sizes (endagered species like pandas and tigers)

If a population stopped reproducing sexually (but still reproduced asexually), how would its genetic variation be affected over time? Explain.

Its genetic variation (whether measure at the level of the gene or at the level of nucleotide sequences) would probably drop over time. During miosis, crossing over and the independent assortment of chromosomes produce many new combinations of alleles. In addition, a population holds a vast numbers of mating combinations and fertilization of gametes of individuals with different genetic backgrounds. Thus, via crossing over, independent assortment of chromosomes, and fertilization, sexual reproduction reshuffled alleles into fresh combos each generation. Without sexual reproduction new sources of genetic variation would be reduced, causing the overall amount of genetic variation to drop.

Of all the mutations that occur in a population, why do only a small fraction become widespread?

Many mutations in somatic cells that do not produce gametes and are so lost when organism dies Of mutations that do occur in cell lines that produce gametes, many do not have a phenotypic effect on which natural selection can act others have a harmful effect and are thus unlikely to increase in frequency because they decrease the reproductive success of their bearers.

Distinguish meiosis from mitosis.

Mitosis Involves one cell division. Results in two daughter cells Results in diploid daughter cells. (chromosome number remains the same as parent cell) Daughter cells are genetically identical. Occurs in all organisms except viruses. Creates all body cells (somatic) apart from the germ cells (eggs and sperm). Prophase is much shorter No recombination/crossing over occurs in prophase. In metaphase individual chromosomes (pairs of chromatids) line up along the equator. During anaphase the sister chromatids are separated to opposite poles. Meiosis Involves two successive cell divisions Results in four daughter cells Results in haploid daughter cells (chromosome number is halved from the parent cell) Daughter cells are genetically different Occurs only in animals, plants and fungi Creates germ cells (eggs and sperm) only Goes through prophase 1, Metaphase 1, Anaphase 1, and anaphase 11

Typically, most of the nucleotide variability that occurs within a genetic locus does not affect the phenotype. Explain why.

Much of the nucleotide variability at a genetic loci occurs within introns.Nucleotide variation at these sites does NOT affect the phenotype because INTRONS DO NOT code for the protein of the gene.Many variable nucleotide sites within Exons. Most of the variable site within exons reflect changes to the DNA sequence that do not change the sequence of amino acids encoded by the gene (may not affect the phenotype).

In Figure 20.4, which similarly inclusive taxon is represented as descending from same common ancestor as Canidae? 1. Felidae 2. Mustelidae 3. Carnivora 4. Lutra

Mustelidae

The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for this data? 1. Forelimb evolution was adaptive in people and bats, but not in whales. 2. Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy. 3. Genes mutate faster in whales than in humans or bats. 4. Whales are not properly classified as mammals.

Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.

In what sense is natural selection more "predictable" than genetic drift?

Natural selection is more predictable in that it alters allele frequencies in a nonrandom way; it tends to increase the frequency of alleles that increase the organisms; reproductive success in its environment and decreases the frequency of alleles that decreases the organisms reproductive success. Alleles subject to genetic drift increase or decrease in frequency by chance alone, whether they are helpful.

To distinguish a particular clade of mammals within the larger clade that corresponds to class Mammalia, would hair be a useful character? Why or why not?

No because hair is shared ancestral character common to all mammals

What is the relative fitness of a sterile mule? Explain.

None because relative fitness includes reproductive contribution to the next generation and a sterile cannot produce offspring

Would two small, geographically isolated populations in very different environments be likely to evolve in similar ways? Explain.

Not likely, because natural selection is dependent on the environment so the alleles favored in one environment may be completely detrimental in the other therefore we not likely be favourably selected.

How does the concept of descent with modification explain both the unity and diversity of life?

Organisms share characteristics (the unity of life) because they share common ancestors; the great diversity of life occurs because new species have repeatedly formed when descendant organisms gradually adapted to different environments, becoming different from their ancestors.

To apply parismony to constructing a phylogenetic tree

Choose the three that represents the fewest evolutionary changes, in either DNA sequences or morphology

Which of the following is NOT an observation or inference on which natural selection is based? 1. There is heritable variation among individuals 2. poorly adapted individuals never produce offsprings. 3. species produce more offspring than the environment can support. 4. Only a fraction of an individuals offspring may survive.

Poorly adapted individuals never produce offspring.

Suppose two bird species live in a forest and are not known to interbreed. One species feeds and mates in the treetops and the other on the ground. But in captivity, the birds can interbreed and produce viable, fertile offspring. What type of reproductive barrier most likely keeps these species separate in nature? Explain.

Prezygotic barrier because live in similar environments and can breed successfully in captivity and different preferences in habitats could result in habitat isolation.

The most parsimonious tree of evolutionary relationships can be inaccurate. How can this occur?

Principle of maximum parsimony states hypothesis about nature we investigate first should be simplest explanation found to be consistent with facts. Actual evolutionary relationships may differ from those inferred by parsimony owing to complicating factors

Suppose two plant populations exchange pollen and seeds. In one population, individuals of genotype AA are most common (9,000 AA, 900 Aa, 100 aa), while the opposite is true in the other population (100 AA, 900 Aa, 9,000 aa). If neither allele has a selective advantage, what will happen over time to the allele and genotype frequencies of these populations?

Selection is not important at this locus; furthermore, the populations are not small, and hence the effects of genetic drift should not be pronounced, gene flow is occurring via the movement of pollen and seeds, thus allele and genotype frequencies in these populations should become more similar over time, with regards to this locus, as a result of gene flow.

Within six months of effectively using methicillin to treat S. aureus infections in a community, all new S. aureus infections were caused by MRSA. How can this best be explained? 1. A patient must have become infected with MRSA from another community. 2. In response to the drug, S. aureus began making drug-resistant versions of the protein targeted by the drug. 3. Some drug-resistant bacteria were present at the start of treatment, and natural selection increased their frequency. 4. S. aureus evolved to resist vaccines.

Some drug- resistant bacteria were present at the start of treatment, and natural selection increased their frequency.

Which of the following observations helped Darwin shape his concept of descent with modification? 1. Species diversity declines farther from the equator. 2. Fewer species live on islands than on the nearest continents. 3. Birds live on islands located farther from the mainland than the birds' maximum nonstop flight distance. 4. South American temperate plants are more similar to South American tropical plants than to European temperate plants.

South American temperate plants are more similar to South American tropical plants than to European temperate plants.

Is speciation something that happened only in the distant past, or are new species continuing to arise today? Explain.

Speciation continues today, a new species can begin to form whenever gene flow is reduced between populations of the parent species. Such reductions in gene flow can occur in many ways: A new, graphically isolated population may be founded by a few colonists; some members of the parent species may begin to utilize a new habitat; and sexual selection may isolate formerly connected populations or subpopulations. These and many other such events are happening today.

Suppose that two species, A and B, have similar appearances but very divergent gene sequences, while species B and C have very different appearances but similar gene sequences. Which pair of species is more likely to be closely related: A and B, or B and C? Explain.

Species B and C, because small genetic changes produce divergent physical appearance, but if genes diverged lineages seperate for a long time.

Explain why anatomical and molecular features often fit a similar nested pattern. In addition, describe a process that can cause this not to be the case.

Specific anatomical and molecular features are shared by a narrow range of species are not shared by a more broad range of species. However, other features are shared not only among their narrow range of species but also a broader range. The process of convergent evolution producing analogous structures may confuse this.

Summarize the flow of information from genes to proteins

The central dogma: Instructions on DNA are transcribed onto messenger RNA. ... The central dogma of molecular biology describes the flow of genetic information in cells from DNA to messenger RNA (mRNA) to protein. It states that genes specify the sequence of mRNA molecules, which in turn specify the sequence of proteins.

Predict whether a fossil of an extinct mammal that lived high in the Andes would more closely resemble present-day mammals that live in South American jungles or present-day mammals that live high in Asian mountains. Explain.

The fossil mammal species (or its ancestors) would most likely have colonized the Andes from within South America, whereas ancestors of mammals currently found in African mountains would most likely have colonized those mountains from other parts of Africa. As a result, the Andes fossil species would share a more recent common ancestor with South American mammals than with mammals in Africa. Thus, for many of its traits, the fossil mammal species would probably more closely resemble mammals that live in South American jungles than mammals that live on African mountains. It is also possible, however, that the fossil mammal species could resemble the Af- rican mountain mammals by convergent evolution (even though they were only distantly related to one another).

Describe an example from the fossil record that shows how life has changed over time.

The fossil records shows that different organisms dominated life of Earth at different points in time and that many organisms once alive are now extinct. It also indicates that a new group of organisms can arise via the gradual modification of previously exsisting organisms as illustrated by fossils that document the origin of mammals from cynodont ancestors

Suppose a molecular clock dates the divergence of two taxa at 80 million years ago, but new fossil evidence shows that the taxa diverged at least 120 million years ago. Explain how this could happen.

The genes used for the molecular clock may have evolved more slowly i these two taxa than in the species used to collaborate the clock; as a result, the clock would underestimate the time at which taxa diverged from each other

Plant species A has a diploid number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be 1 1. 14. 2. 16. 3. 28. 4. 56.

28

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2? 1. 0.7 2. 0.49 3. 0.42 4. 0.21

70% = A1 100-70 = 30% = A2 The proportion with both: 2 X .70 X .30= .42 0.42

Review the relationship between genotype and phenotype (see Figure 11.6). Suppose that in a particular pea population, flowers with the white phenotype are favored by natural selection. Predict what would happen over time to the frequency of the p allele in the population, and explain your reasoning.

As long as the white phenotype (encoded by the genotype pp) continues to be favored by natural selection, the frequency of the p allele will likely increase over time in the population. If the proportion of white individuals increases relative to purple individuals, the frequency of the recessive p allele will also increase relative to that of the P allele, which only appears in purple individuals (some of which also carry a p allele).

Suppose that a gene for coat color in mice has two alleles, B and b, where B is completely dominant and encodes a black coat color, and b is recessive and encodes a brown coat color. A mouse that is heterozygous has genotype ____ and its phenotype is ___.

Bb; black because heterozygous is different.

Why is the kingdom Monera no longer considered a valid taxon?

Because it includes members from two domains, groupings that are one level above kingdom. Also, Domain Archaea are more closely related to Domain Eurkarya then they are to Domain Bacteria.

Explain why phylogenies based on different genes can yield different branching patterns for the tree of all life.

Because of horizontal gene transfer, some genes in eukaryotes are more closely related to bacteria, while others are more closely related to archaea; thus depending on which genes are used phylogentic trees constructed from DNA data can yield conflicting results

Scientific hypotheses must be testable (see Concept 1.3). Applying this criterion, are Cuvier's explanation of the fossil record and Lamarck's hypothesis of evolution scientific? Explain your answer in each case.

By this criterion, Cuvier's explanation of the fossil record and Lamarck's hypothesis of evolution are both scientific. Cuvier thought that species did not evolve over time. He also suggested that sudden, catastrophic events caused extinctions in particular areas and that such regions were later repopulated by a different set of species that immigrated from other areas. These assertions can be tested against the fossil record, and his assertion that species do not evolve has been demonstrated to be incorrect. With respect to Lamarck, his principle of use and disuse can be used to make testable predictions for fossils of groups such as whale ancestors as they adapted to a new habitat. Lamarck's principle of use and disuse and his associated principle of the inheritance of acquired characteristics can also be tested directly in living organisms; these principles have been shown to be incorrect.

Distinguish between prokaryotic and eukaryotic organisms

The primary distinction between these two types of organisms is that eukaryotic cells have a membrane-bound nucleus and prokaryotic cells do not. ... The nucleus is only one of many membrane-bound organelles in eukaryotes. Prokaryotes, on the other hand, have no membrane-bound organelles

Explain how the scientific process works

The process of the scientific method involves making conjectures (hypotheses), deriving predictions from them as logical consequences, and then carrying out experiments or empirical observations based on those predictions. ... Scientists then test hypotheses by conducting experiments or studies.

Explain the consequences of plate tectonics for life on Earth.

The theory of plate tectonics describes the movement of Earths continental plates, which alerts the physical geography and climate of Earth, as well as the extent to which organisms are geographically isolated. Because these factors affect extinction and speciation rates, place tectonics has a major impact of life on Earth.

In a population, 16 people have genotype VV, 92 have genotype Vv, and 12 have genotype vv. Is this population evolving? Explain.

There are 120 individuals in the population, so there are 240 alleles. Of these, there are 124 V alleles—32 from the 16 VV individuals and 92 from the 92 Vv individuals. Thus, the frequency of the V allele is p = 124/240 = 0.52; hence, the frequency of the v allele is q = 0.48. Based on the Hardy-Weinberg equation, if the population were not evolving, the frequency of genotype VV should be p2 = 0.52 × 0.52 = 0.27; the frequency of genotype Vv should be 2pq = 2 × 0.52 × 0.48 = 0.5; and the frequency of genotype vv should be q2 = 0.48 × 0.48 = 0.23. In a population of 120 individuals, these expected genotype frequencies lead us to predict that there would be 32 VV individuals (0.27 × 120), 60 Vv individuals (0.5 × 120), and 28 vv individuals (0.23 × 120). The actual numbers for the population (16 VV, 92 Vv, 12 vv) deviate from these expectations. This indicates that the population is not in Hardy-Weinberg equilibrium and hence may be evolving at this locus.

Review Concept 14.5. Then explain how numerous base changes could occur in an organism's DNA yet have no effect on its survival and reproduction.

There are many portions of the genome that do not code for genes; many base changes in the regions could accumulate through drift without affecting an organisms fitness. Even in coding regions of genomes, some mutations may not have a critical effect on gene or proteins

How did Hutton's and Lyell's ideas influence Darwin's thinking about evolution?

They proposed that geologic events in the past were caused by the same processes operating today, at the same gradual rate. This suggested that Earth must be much older than a few thousand years. Also, that slow accumulation of small changes could produce the profound changes documented in the fossil record. The age of the earth was important to Darwin, because unless it was very old, he could not envision how there would have been enough time for evolution to occur.

Explain why genetic variation within a population is a prerequisite for evolution.

Within a population, genetic differences among individuals provide the raw material on which natural selection and other mechanisms can act without such differences, allele frequencies could not change over time and hence the population could not evolve

Describe some assumptions and limitations of molecular clocks.

a key assumption of molecular clocks is that nucleotide substitutions occur at fixed rates and hence the number of nucleotide differences between two DNA sequences is proportional to the the time since the sequences diverged from each other some limitations of molecular clocks; no gene marks time with complete percision, natural selection can favor certain DNA changes over others, necleotide substitution rates can change over long periods of time , and the same gene can evolve at different rates in different organisms

Three living species X, Y, and Z share a common ancestor T, as do extinct species U and V. A grouping that consists of species T, X, Y, and Z (but not U or V) makes up 1. a monophyletic taxon 2. an ingroup, with species U as the outgroup 3. a polyphyletic group 4. a paraphyletic group

a paraphyletic group

In a comparison of birds and mammals, the condition of having four limbs is.. 1. a shared ancestral character 2. a shared derived character 3. a character useful for distinguishing birds from mammals 4. an example of analogy rather than homology

a shared ancestral character

Decide whether each of the following pairs of structures more likely represents analogy or homology, and explain your reasoning: (a) a porcupine's quills and a cactus's spines; (b) a cat's paw and a human's hand; (c) an owl's wing and a hornet's wing.

a. Analogy, since porcupines and cacti are not closely related and since most other animals and plants do not have similar structures b. Homology, since cats and humans are both mammals and have homologous forelimbs, of which the hand and paw are the lower part. c. Analogy, since owls and hornets are not closely related and since the structure of their wings is very different