Module 4

Evidence that supports the endosymbiotic origin of mitochondria and plastids

-The inner membranes of both organelles have enzymes and transport systems that are homologous to those found in the plasma membranes of living bacteria. -Mitochondria and plastids replicate by a splitting process that is similar to that of certain bacteria. In addition, each of these organelles contains circular DNA molecules that, like the chromosomes of bacteria, are not associated with histones or large amounts of other proteins. -As might be expected of organelles descended from free-living organisms, mitochondria and plastids also have the cellular machinery (including ribosomes) needed to transcribe and translate their DNA into proteins. -Finally, in terms of size, RNA sequences, and sensitivity to certain antibiotics, the ribosomes of mitochondria and plastids are more similar to bacterial ribosomes than they are to the cytoplasmic ribosomes of eukaryotic cells.

Why is there high genetic variability in bacterial populations?

1. Rapid reproduction rates via binary fission 2. High mutation rates 3. Genetic recombination due to horizontal gene transfer

Describe the structure of a gymnosperm seed. Which structures are haploid/diploid?

1. Seed Coad: (2n) old sporophyte generation; former integument 2. Female gametophyte (n) becomes a food reserve for the developing embryo 3. embryo (2n) new sporophyte generation

What are the four major phyla of gymnosperms?

1.Cycads 2.Ginkgo 3.Conifers -most gymnosperms are conifers! 4.Gnetophytes

What are the four supergroups of protists?

1.Excavata 2.SAR 3.Archaeplastida 4.Unikonta

What adaptations have enabled seed plants to make up the vast majority of plant biodiversity?

1.Reduced male and female gametophytes •Gymnosperms: cones •Angiosperms: Flowers 2.Pollen 3.Ovules 4.Seed

What does the SAR supergroup of protists consist of?

1.Stramenopiles-diatoms and brown algae 2.Alveolates -dinoflagellates and apicomplexans•Dinoflagellate ex: red tide 3.Rhizarians-amoebas

What is one way in which a cellular slime mold differs from a plasmodial slime mold?

A cellular slime mold is multicellular.

How could phylogenies be used to help researchers search more efficiently for novel medicines derived from seed plants?

A detailed phylogeny of the seed plants would identify many different monophyletic groups of seed plants. Using this phylogeny, researchers could look for clades that contained species in which medicinally useful compounds had already been discovered. Identification of such clades would allow researchers to concentrate their search for new medicinal compounds among clade members—as opposed to searching for new compounds in species that were selected at random from the more than 290,000 existing species of seed plants.

What would a fossil record of life today look like?

A fossil record of life today would include many organisms with hard body parts (such as vertebrates and many marine invertebrates), but might not include some species we are very familiar with, such as those that have small geographic ranges and/or small population sizes (for example, endangered species such as the giant panda, tiger, and several rhinoceros species).

What are mycorrhizae?

A fungus grows in association with the roots of a plant to improve absorption for the plant.

What characteristics of pathogenic fungi result in their being efficiently transmitted?

A hardy spore stage enables dispersal to host organisms through a variety of mechanisms; their ability to grow rapidly in a favorable new environment enables them to capitalize on the host's resources.

serial endosymbiosis

A hypothesis for the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells.

Distinguish between the four major modes of nutrition, noting which are unique to prokaryotes.

A phototroph derives its energy from light, while a chemotroph gets its energy from chemical sources. An autotroph derives its carbon from CO2, HCO3 -, or related compounds, while a heterotroph gets its carbon from organic nutrients such as glucose. Thus, there are four nutritional modes: photoautotrophic, photoheterotrophic (unique to prokaryotes), chemoautotrophic (unique to prokaryotes), and chemoheterotrophic.

Cambrian explosion

A relatively brief time in geologic history when many present-day phyla of animals first appeared in the fossil record. This burst of evolutionary change occurred about 535-525 million years ago and saw the emergence of the first large, hard-bodied animals.

What are some of the benefits that lichen algae can derive from their relationship with fungi?

A suitable environment for growth, retention of water and minerals, protection from intense sunlight, and protection from being eaten

Which of the following is the best description of protists' contribution to photosynthesis?

About 30% of the world's photosynthesis is performed by protists.

Describe two adaptations that enable prokaryotes to survive in environments too harsh for other organisms.

Adaptations include the capsule (shields prokaryotes from the host's immune system) and endospores (enable cells to survive harsh conditions and to revive when the environment becomes favorable).

What evidence supports the hypothesis that mitochondria preceded plastids in the evolution of eukaryotic cells?

All eukaryotes have mitochondria or remnants of these organelles, but not all eukaryotes have plastids.

What do we mean by "alternation of generations"?

Alternation of generations, also called metagenesis or heterogenesis, in biology, the alternation of a sexual phase and an asexual phase in the life cycle of an organism. The two phases, or generations, are often morphologically, and sometimes chromosomally, distinct. The fern is an example of alternation of generations, in which both a multicellular diploid organism and a multicellular haploid organism occur and give rise to the other. ... The large, leafy fern is the diploid organism. On the undersurface of its fronds or leaves, its cells undergo meiosis to create haploid cells.

What is the alternation of generation life cycle?

Alternation of sexual/nonsexual phases in plants Gametophyte generation: Multicellular haploid form, produces gametes via mitosis •Multicellular gametophyte is specialized for fertilization Sporophyte generation: Multicellular diploid form, happens after the fusion of gametes and produces spores via meiosis •Multicellular sporophyte is specialized for dispersal on land

Explain how prokaryotes, though small, can be considered giants in their collective impact on Earth and its life.

Although prokaryotes are small, their large numbers and metabolic abilities enable them to play key roles in ecosystems by decomposing wastes, recycling chemicals, and affecting the concentrations of nutrients available to other organisms.

Contrast the pseudopodia of amoebozoans and forams.

Amoebozoans have lobe- or tube-shaped pseudopodia, whereas forams have threadlike pseudopodia.

What is an extremophile?

An organism (primary archaea species) that are capable in living in stressful environments including areas with very high salinity or very high/low temperatures

Give three examples of how structure fits function in bryophytes.

Answers may include the following: Large surface area of protonema enhances absorption of water and minerals; the vase-shaped archegonia protect eggs during fertilization and transport nutrients to the embryos via placental transfer cells; the stalk-likeseta conducts nutrients from the gametophyte to the capsule, where spores are produced; the peristome enables gradual spore discharge; stomata enable CO2/O2 exchange while minimizing water loss; lightweight spores are readily dispersed by wind.

Which of these groups includes parasitic unicellular organisms with a complex of organelles specialized for penetrating host cells and tissues?

Apicomplexans

Review Figure 10.3 and Figure 10.5. If a plant has mycorrhizae, where might carbon that enters the plant's stomata as CO2 eventually be deposited: in the plant, in the fungus, or both? Explain.

Carbon that enters the plant through stomata is fixed into sugar through photosynthesis. Some of these sugars are absorbed by the fungus that partners with the plant to form mycorrhizae; others are transported within the plant body and used in the plant. Thus, the carbon may be deposited in either the body of the plant or the body of the fungus.

What is the main difference between bacteria/archaea cell structure?

Bacteria cell membranes are made of a lipid bilayer, while archaea cell membranes are made of a lipid monolayer

What are some examples of Archaea? How do they differ from bacteria?

Bacteria contain peptidoglycan in the cell wall; archaea do not. The cell membrane in bacteria is a lipid bilayer; in archaea, it can be a lipid bilayer or a monolayer. Bacteria contain fatty acids on the cell membrane, whereas archaea contain phytanyl.

Explain why forams have such a well-preserved fossil record.

Because foram tests are hardened with calcium carbonate, they form longlasting fossils in marine sediments and sedimentary rocks.

Justify the claim that photosynthetic protists are among the biosphere's most important organisms.

Because photosynthetic protists constitute the base of aquatic food webs, many aquatic organisms depend on them for food, either directly or indirectly. (In addition, a substantial percentage of the oxygen produced by photosynthesis is made by photosynthetic protists.)

Which example below is a characteristic shared by diplomonads and parabasalids?

Both lack plastids.

How do the main similarities and differences between seedless vascular plants and nonvascular plants affect function in these plants?

Both seedless vascular plants and bryophytes have flagellated sperm that require moisture for fertilization; this shared similarity poses challenges for these species in arid regions. With respect to key differences, seedless vascular plants have lignified, well-developed vascular tissue, a trait that enables the sporophyte to grow tall and that has transformed life on Earth (via the formation of forests). Seedless vascular plants also have true leaves and roots, which, when compared with bryophytes, provide increased surface area for photosynthesis and improve their ability to extract nutrients from soil.

What are bryophytes? What are the three major types?

Bryophytes: Seedless, non-vascular plants •Lack of rigid support structures, lack of vascular tissue, lack of true roots and leaves •Dominant gametophyte generation Three types: 1.Liverwort 2.Moss 3.Hornwort

A bacterium requires only the amino acid methionine as an organic nutrient and lives in lightless caves. What mode of nutrition does it employ? Explain.

Chemoheterotrophy; the bacterium must rely on chemical sources of energy, since it is not exposed to light, and it must be a heterotroph if it requires a source of carbon other than CO2 (or a related compound, such as HCO3-).

Which of the following is not a protist genera that parasitizes humans?

Chlamydomonas

What is the difference between conjugation, transduction, and transformation?

Conjugation: A donor cell will give DNA to a recipient cell through direct contact via a pilus Transduction: A bacterium will gain new DNA from viral infection (ex. bacteriophage infection) Transformation: Bacteria obtaining foreign DNA from the environment

High water temperatures and pollution can cause corals to expel their dinoflagellate symbionts. How might such "coral bleaching" affect corals and other species?

Corals depend on their dinoflagellate symbionts for nourishment, so coral bleaching could cause the corals to die. As the corals die, less food would be available for fishes and other species that eat coral. As a result, populations of these species might decline, and that, in turn, might cause populations of their predators to decline.

Then summarize the main steps by which cyanobacteria produce O2O2 and use CO2CO2 to make organic compounds.

Cyanobacteria produce oxygen when water is split in the light reactions of photosynthesis. The Calvin cycle incorporates CO2 from the air into organic molecules, which are then converted to sugars.

What are cyanobacteria? How do they get their food?

Cyanobacteria, often known as blue-green algae, are among the most abundant organisms in oceans and fresh water. They are similar to green plants because they can use the energy from sunlight to make their own food through photosynthesis

Why are fungi classified as opisthokonts despite the fact that most fungi lack flagella?

DNA evidence indicates that fungi, animals, and their protistan relatives form a clade, the opisthokonts. Furthermore, chytrids and other fungi thought to be members of basal lineages have posterior flagella, as do most other opisthokonts. This suggests that other fungal lineages lost their flagella after diverging from ancestors that had flagella.

Review Figures 9.2 and 10.5, and then summarize how CO2CO2 and O2O2 are both used and produced by chlorarachniophytes and other aerobic algae.

During photosynthesis, aerobic algae produce O2O2 and use CO2CO2. O2O2 is produced as a by-product of the light reactions, while CO2CO2 is used as an input to the Calvin cycle (the end products of which are sugars). Aerobic algae also perform cellular respiration, which uses O2O2 as an input and produces CO2CO2 as a waste product.

Review the discussion of feedback regulation in Concept 1.1. Could effects of global warming on peatlands alter CO2CO2 concentrations in ways that result in negative or positive feedback? Explain.

Effects of global warming on peatlands could result in positive feedback, which occurs when an end product of a process increases its own production. In this case, global warming is expected to lower the water levels of some peatlands. This would expose peat to air and cause it to decompose, thereby releasing stored CO2 to the atmosphere. The release of more stored CO2 to the atmosphere could cause additional global warming, which in turn could cause further drops in water levels, the release of still more CO2 to the atmosphere, additional warming, and so on: an example of positive feedback.

Find an example of a protist that has photosynthesis. Find an example of a protist that is a human pathogen

Examples of protists include algae, amoebas, euglena, plasmodium, and slime molds. Protists that are capable of photosynthesis include various types of algae, diatoms, dinoflagellates, and euglena. Most protist diseases in humans are caused by protozoa. Protozoa make humans sick when they become human parasites. Trypanosoma protozoa cause Chagas disease and sleeping sickness. Giardia protozoa cause giardiasis, and Plasmodium protozoa cause malaria.

What are some characteristics of our "Last Universal Common Ancestor" (LUCA)? How do we know?

Features. By analysis of the presumed LUCA's offspring groups, the LUCA appears to have been a small, single-celled organism. It likely had a ring-shaped coil of DNA floating freely within the cell. Morphologically, it would likely not have stood out within a mixed population of small modern-day bacteria. That one cell is called the Last Universal Common Ancestor (LUCA). It probably existed around 3.5 billion years ago. LUCA was one of the earliest prokaryotic cells. It would have lacked a nucleus and other membrane-bound organelles.

Which of the three life cycles in Figure 13.6 exhibits alternation of generations? How does it differ from the other two?

Figure 13.6b. Algae and plants with alternation of generations have a multicellular haploid stage and a multicellular diploid stage. In the other two life cycles, either the haploid stage or the diploid stage is unicellular.

What was the first organic molecule? Did the first prokaryotes utilize oxygen or carbon dioxide?

First organic molecule: RNA, then DNA, then protein The first prokaryotes utilized carbon dioxide because oxygen wasn't present in the Earth's atmosphere until much later.

What feature of chytrids supports the hypothesis that they include members of basal fungal lineages?

Flagellated spores; molecular evidence also suggests that chytrids include species that belong to lineages that diverged from other fungi early in the history of the group.

What is an evolutionary advantage of flowers? fruits?

Flowering plants mature more quickly than gymnosperms, and produce greater numbers of seeds. The woody tissues of angiosperms are also more complex and specialized. Their seeds are enclosed in a fruit for easy dispersal by wind, water, or animals.

The first appearance of free oxygen in the atmosphere likely triggered a massive wave of extinctions among the prokaryotes of the time. Why?

Free oxygen attacks chemical bonds and can inhibit enzymes and damage cells. As a result, the appearance of oxygen in the atmosphere probably caused many prokaryotes that had thrived in anaerobic environments to survive and reproduce poorly, ultimately driving many of these species to extinction.

If fungi colonized land before plants, where might the fungi have lived? How would their food sources have differed from what they feed on today?

Fungi are heterotrophs. Prior to the colonization of land by plants, terrestrial fungi would have lived where other organisms (or their remains) were present and provided a source of food. Thus, if fungi colonized land before plants, they could have fed on prokaryotes or protists that lived on land or by the water's edge—but not on the plants or animals on which many fungi feed today.

plant vs fungi

Fungi can reproduce asexually by budding, and many also have sexual reproduction and form fruitbodies that produce spores. ... Unlike plants, fungi do not produce their own food - like animals, they have to source it.

What is the difference between a gram positive and a gram negative bacterial cell?

Gram-positive: Has a thick peptidoglycan layer (stains purple) Gram-negative: No peptidoglycan layer (stains pink)

What are some examples of photoautorophs, chemo-heterotrophs, etc.?

Green plants and photosynthetic bacteria are examples of photoautotrophs Photoheterotrophs are organisms that capture light energy to convert to chemical energy in the cells, but they get carbon from organic sources (other organisms). Examples are purple non-sulfur bacteria, green non-sulfur bacteria and heliobacteria. Chemoheterotrophs are the most abundant type of chemotrophic organisms and include most bacteria, fungi and protozoa.

What is the difference between heterospory and homospory? What about microspores and megaspores?

Heterospory: Male and female gametophytes are two different sizes Homospory: Gametophytes are the same size Microspores: Smaller spores that give rise to male gametophyte Macrospores: Larger spores that give rise to female gametophyte

What are some of the similarities and differences between ferns, horsetails, and lycophytes?

Horsetails are related to ferns in that they have a vascular system. They never developed the ability to reproduce with seeds. ... Unlike ferns, these are tough plants. While ferns are soft, horsetails are rough plants and even have silica (silicon-based compound) in their epidermal cells. Ferns are an ancient group of around 12,000 vascular plants. ... Lycophytes, also known as the 'fern allies', are a group of roughly 1250 primitive plant species. They similar to ferns but have unique leaves called 'microphylls' which have only a single vein. Fern fronds are the leaves of ferns.

Lecture Notes 4/5

How did life get started? DNA is much more stable than RNA Proteins replace RNA as the base of enzymes because they have more properties and u can have more enzymes made out of proteins than RNA Prokaryotes can exchange DNA one way or another. divide by budding 1. transformation 2. conjugation 3. transduction

If a seed could not enter dormancy, how might that affect the embryo's transport or survival?

If a seed could not enter dormancy, the embryo would continue to grow after it was fertilized. As a result, the embryo might rapidly become too large to be dispersed, thus limiting its transport. The embryo's chance of survival might also be reduced because it could not delay growth until conditions become favorable.

Describe what you might eat for a typical meal if humans, like cyanobacteria, could fix nitrogen.

If humans could fix nitrogen, we could build proteins using atmospheric N2 and hence would not need to eat high-protein foods such as meat, fish, or soy. Our diet would, however, need to include a source of carbon, along with minerals and water. Thus, a typical meal might consist of carbohydrates as a carbon source, along with fruits and vegetables to provide essential minerals (and additional carbon).

It is said that an oak is an acorn's way of making more acorns. Write an explanation that includes these terms: sporophyte, gametophyte, ovule, seed, ovary, and fruit.

In the oak's life cycle, the tree (the sporophyte) produces flowers, which contain gametophytes in pollen grains and ovules; the eggs in ovules are fertilized; the mature ovaries develop into dry fruits called acorns. We can view the oak's life cycle as starting when the acorn seeds germinate, resulting in embryos giving rise to seedlings and finally to mature trees, which produce flowers—and then more acorns.

Distinguish between the three mechanisms by which bacteria can transfer DNA from one bacterial cell to another.

In transformation, naked, foreign DNA from the environment is taken up by a bacterial cell. In transduction, phages carry bacterial genes from one bacterial cell to another. In conjugation, a bacterial cell directly transfers plasmid or chromosomal DNA to another cell via a mating bridge that temporarily connects the two cells.

Stromatolites

Layered rock that results from the activities of prokaryotes that bind thin films of sediment together.

List the key derived traits found in monilophytes and seed plants, but not in lycophytes.

Lycophytes have microphylls, whereas seed plants and monilophytes (ferns and their relatives) have megaphylls. Monilophytes and seed plants also share other traits not found in lycophytes, such as the initiation of new root branches at various points along the length of an existing root.

How might life on Earth differ from what we know today if no mutualistic relationships between fungi and other organisms had ever evolved?

Many different outcomes might have occurred. Organisms that currently form mutualisms with fungi might have gained the ability to perform the tasks currently done by their fungal partners, or they might have formed similar mutualisms with other organisms (such as bacteria). Alternatively, organisms that currently form mutualisms with fungi might be less effective at living in their present environments. For example, the colonization of land by plants might have been more difficult. And if plants did eventually colonize land without fungal mutualists, natural selection might have favored plants that formed more highly divided and extensive root systems (in part replacing mycorrhizae).

Contrast red algae and brown algae.

Many red algae contain a photosynthetic pigment called phycoerythrin, which gives them a reddish color and allows them to carry out photosynthesis in relatively deep coastal water. Also unlike brown algae, red algae have no flagellated stages in their life cycle and must depend on water currents to bring gametes together for fertilization.

Explain how molecular systematics and metagenomics have contributed to our understanding of the phylogeny and evolution of prokaryotes.

Molecular systematic studies indicate that some organisms once classified as bacteria are more closely related to eukaryotes and belong in a domain of their own: Archaea. Such studies have also shown that horizontal gene transfer is common and plays an important role in the evolution of prokaryotes. By not requiring that organisms be cultured in the laboratory, metagenomic studies have revealed an immense diversity of previously unknown prokaryotic species. Over time, the ongoing discovery of new species by metagenomic analyses may alter our understanding of prokaryotic phylogeny greatly.

Moss life cycle

Mosses have diploid and haploid generations. Gametophytes, spores, sperm, and eggs are all haploid. Zygotes and their resulting sporophytes are diploid. When the antheridia are ripe the antherozoids are released, these antherozoids or sperm cells then swim by means of two threadlike tails and are attracted chemically to the archegonium, where fertilization occurs to form a zygote.

How do bryophytes differ from other plants?

Most bryophytes do not have a vascular transport system, and their life cycleis dominated by gametophytes rather than sporophytes.

Describe the importance of mycorrhizae, both today and in the colonization of land. What evidence supports the antiquity of mycorrhizal associations?

Mycorrhizae form extensive networks of hyphae through the soil, enabling nutrients to be absorbed more efficiently than a plant can do on its own; this is true today, and similar associations were probably very important for the earliest plants (which lacked roots). Evidence for the antiquity of mycorrhizal associations includes fossils showing arbuscular mycorrhizae in the early plant Aglaophyton and molecular results showing that genes required for the formation of mycorrhizae are present in liverworts and other basal plant lineages.

how do prokaryotes reproduce

Prokaryotes reproduce through a cell division process called binary fission. Like mitosis in eukaryotes, this process involves copying the chromosome and separating one cell into two.

A pathogenic bacterium's toxin causes symptoms that increase the bacterium's chance of spreading from host to host. Does this information indicate whether the poison is an exotoxin or endotoxin? Explain.

No. If the poison is secreted as an exotoxin, live bacteria could be transmitted to another person. But the same is true if the poison is an endotoxin—only in this case, the live bacteria that are transmitted may be descendants of the (now-dead) bacteria that produced the poison.

Compare and contrast a pine cone and a flower in terms of structure and function.

Pine cones and flowers both have sporophylls, modified leaves that produce spores. Pine trees have separate pollen cones (with pollen grains) and ovulate cones (with ovules inside cone scales). In flowers, pollen grains are produced by the anthers of stamens, and ovules are within the ovaries of carpels. Unlike pine cones, many flowers produce both pollen and ovules.

What are some essential adaptations for life on land

Plant adaptations to life on land include the development of many structures — a water-repellent cuticle, stomata to regulate water evaporation, specialized cells to provide rigid support against gravity, specialized structures to collect sunlight, alternation of haploid and diploid generations, sexual organs, a multicellular embryo protected by parental tissue, a vascular transport system, and rhizoids, roots and root hairs essential for the absorption of nutrients and anchoring to the substrate 4, 5, 6, 7, 8, 9. Regulation of gene expression is essential for the evolution of morphological diversity, including the establishment and perpetuation of developmental programs involved in plant adaptations to life on land [9]. However, our knowledge of the genetic and molecular mechanisms underlying morphological diversity and plant adaptation to land remains limited.

Explain why plant diversity can be considered a nonrenewable resource.

Plant diversity can be considered a resource because plants provide many important benefits to humans; as a resource, plant diversity is nonrenewable because if a species is lost to extinction, that loss is permanent.

Why do researchers identify the charophytes rather than another group of algae as the closest living relatives of plants?

Plants share some key traits only with charophytes: rings of cellulose-synthesizing complexes and similarity in sperm structure. Comparisons of nuclear, chloroplast, and mitochondrial DNA sequences also indicate that certain groups of charophytes (such as Zygnema) are the closest living relatives of plants.

Suggest a hypothesis that explains why the thylakoid membranes of chloroplasts resemble those of cyanobacteria.

Plastids such as chloroplasts are thought to have evolved from an endosymbiotic photosynthetic prokaryote. More specifically, the phylogenetic tree shown in Figure 26.21 indicates that plastids are closely related to cyanobacteria. Hence, we can hypothesize that the thylakoid membranes of chloroplasts resemble those of cyanobacteria because chloroplasts evolved from an endosymbiotic cyanobacterium.

Give examples of how form fits function in mucoromycetes, ascomycetes, and basidiomycetes.

Possible answers include the following: In mucoromycetes, the sturdy, thick-walled zygosporangium can withstand harsh conditions and then undergo karyogamy and meiosis when the environment is favorable for reproduction. In one group of mucoromycetes, the glomeromycetes, the hyphae have a specialized morphology that enables the fungi to form arbuscular mycorrhizae with plant roots. In ascomycetes, the asexual spores (conidia) are often produced in chains or clusters at the tips of conidiophores, where they are easily dispersed by wind. The often cup-shaped ascocarps house the sexual spore-forming asci. In basidiomycetes, the basidiocarp supports and protects a large surface area of basidia, from which spores are dispersed.

Identify four derived traits that distinguish plants from charophyte green algae and facilitate life on land. Explain.

Possible answers include walls toughened by sporopollenin (protects against harsh environmental conditions); multicellular, dependent embryos (provide nutrients and protection to the developing embryo); cuticle (reduces water loss); stomata (control gas exchange and reduce water loss)

Although rare on a per gene basis, new mutations can add considerable genetic variation to prokaryotic populations in each generation. Explain how this occurs.

Prokaryotes can have extremely large population sizes, in part because they often have short generation times. The large number of individuals in prokaryotic populations makes it likely that in each generation there will be many individuals that have new mutations at any particular gene, thereby adding considerable genetic diversity to the population.

Contrast the cellular and DNA structures of prokaryotes and eukaryotes.

Prokaryotic cells lack the complex compartmentalization associated with the membrane-enclosed organelles of eukaryotic cells. Prokaryotic genomes have much less DNA than eukaryotic genomes, and most of this DNA is contained in a single ring-shaped chromosome located in the nucleoid rather than within a true membrane enclosed nucleus. In addition, many prokaryotes also have plasmids, small ring-shaped DNA molecules containing a few genes.

What is a protist? Why are protists important for our biosphere?

Protist: diverse group of unicellular/multicellular organisms (ex. unicellular eukaryotes, multicellular algae) Protists perform about 30% of the world's photosynthesis!

Describe three symbioses that include protists.

Protists form mutualistic and parasitic associations with other organisms. Examples include photosynthetic dinoflagellates that form a mutualistic symbiosis with coral polyps; parabasalids that form a mutualistic symbiosis with termites; and the stramenopile Phytophthora ramorum, a parasite of oak trees.

The commonly used term "Protist" is actually paraphyletic grouping. What does that mean and why does that matter?

Protists make up a group that is paraphyletic, meaning that they do not make up all of the descendants of their most recent common ancestor. This is because plants, animals and fungi share this lineage, but are not considered to be protists.

How do protists reproduce?

Protists reproduce asexually, but can undergo genetic recombination through conjugation

Suggest a possible reason why species in the green algal lineage may have been more likely to colonize land than species in the red algal lineage.

Red algae have no flagellated stages in their life cycle and hence must depend on water currents to bring their gametes together. This feature of their biology might increase the difficulty of reproducing on land. In contrast, the gametes of green algae are flagellated, making it possible for them to swim in thin films of water. In addition, a variety of green algae contain compounds in their cytoplasm, cell wall, or zygote coat that protect against intense sunlight and other terrestrial conditions. Such compounds may have increased the chance that descendants of green algae could survive on land.

Which of the following does not take place during the process of conjugation?

Reproduction

protists asexual vs sexual

Reproduction in protists varies widely, depending on the species of protist and the environmental conditions. Some protists reproduce sexually by conjugation, while others form gametes. Others reproduce asexually by formation of zygospores

Identify at least two ways that prokaryotes have affected you positively today.

Sample answers: eating fermented foods such as yogurt, sourdough bread, or cheese; receiving clean water from sewage treatment; taking medicines produced by bacteria

Cite at least four examples of structural and functional diversity among protists.

Sample response: Protists include unicellular, colonial, and multicellular organisms; photoautotrophs, heterotrophs, and mixotrophs; species that reproduce asexually, sexually, or both ways; and organisms with diverse physical forms and adaptations.

What are some of the ways prokaryotes are important for ecological processes or for human health?

Scientists and doctors can even utilize prokaryotes to help the human body. Bacteria are used to make antibiotics that can be helpful in treating infections, as well as insulin for diabetes management.

How has DNA sequencing changed our understanding of prokaryotic diversity

Scientists estimate there may be millions of prokaryotic species (or species-like groups), but we know very little about most of them.^11start superscript, 1, end superscript This is starting to change thanks to large-scale DNA sequencing. DNA sequencing makes it possible for scientists to study entire prokaryotic communities in their natural habitats - including the many prokaryotes that are unculturable, and would previously have been "invisible" to researchers. The collective genome of such a community is called its metagenome, and the analysis of metagenome sequences is known as metagenomics. Prokaryotic metagenomics is one of the areas of biology that I find coolest and most mysterious. For example, a DNA sample can be taken from a hot spring microbial mat, such as the beautiful, multicolored mats found in Yellowstone National Park. Even a tiny sample from this rich community includes many, many individuals of different species.^99

What is "secondary endosymbiosis"?

Secondary endosymbiosis is when a living cell engulfs another eukaryote cell that has already undergone primary endosymbiosis. It has happened often enough that it has led to genetic diversity among the organisms on Earth.

What are some differences between bryophytes and seedless vascular plants?

Seedless vascular plants have: •Life cycles with dominant sporophytes •Transport within vascular tissue •Well-developed roots and leaves •Sporophylls

DNA sequence data for a diplomonad, a euglenid, a plant, and an unidentified protist suggest that the unidentified species is most closely related to the diplomonad. Further studies reveal that the unknown species has fully functional mitochondria. Based on these data, at what point on the phylogenetic tree in Figure 28.5 did the mystery protist's lineage probably diverge from other eukaryote lineages? Explain.

Since the unknown protist is more closely related to diplomonads than to euglenids, it must have originated after the lineage leading to the diplomonads and parabasalids diverged from the euglenozoans. In addition, since the unknown species has fully functional mitochondria—yet both diplomonads and parabasalids do not—it is likely that the unknown species originated before the last common ancestor of the diplomonads and parabasalids.

In what sense is "fungus animal" a fitting description of a slime mold? In what sense is it not fitting?

Slime molds are fungus-like in that they produce fruiting bodies that aid in the dispersal of spores, and they are animal-like in that they are motile and ingest food. However, slime molds are more closely related to tubulinids and entamoebas than to fungi or animals.

How might a sudden and dramatic change in your diet affect the diversity of prokaryotic species that live in your digestive tract?

Some of the many different species of prokaryotes that live in the human gut compete with one another for resources (from the food that you eat). Because different prokaryotic species have different adaptations, a change in diet may alter which species can grow most rapidly, thus altering species abundance.

Describe the different structures within a flower

Stamen (Male) - anther -filament Carpel (female) - stigma -style -ovary - petal -receptacle -sepal

Summarize the role of endosymbiosis in eukaryotic evolution.

Strong evidence shows that eukaryotes acquired mitochondria after a host cell (either an archaean or a cell closely related to the archaea) first engulfed and then formed an endosymbiotic association with an alpha proteobacterium. Similarly, chloroplasts in red and green algae appear to have descended from a photosynthetic cyanobacterium that was engulfed by an ancient heterotrophic eukaryote. Secondary endosymbiosis also played an important role: Various protistan lineages acquired plastids by engulfing unicellular red or green algae.

Suppose that the mutation of an ascomycete changed its life cycle so that plasmogamy, karyogamy, and meiosis occurred in quick succession. How might this affect the ascospores and ascocarps?

Such a change to the life cycle of an ascomycete would reduce the number and genetic diversity of ascospores that result from a mating event. Ascospore number would drop because a mating event would lead to the formation of only one ascus. Ascospore genetic diversity would also drop because in ascomycetes, one mating event leads to the formation of asci by many different dikaryotic cells. As a result, genetic recombination and meiosis occur independently many different times—which could not happen if only a single ascus was formed. It is also likely that if such an ascomycete formed an ascocarp, the shape of the ascocarp would differ considerably from that found in its close relatives.

Compare and contrast the nutritional mode of a fungus with your own nutritional mode.

Suppose a certain fungus is a mutualist that lives within an insect host, yet its ancestors were parasites that grew in and on the insect's body. What derived traits might you find in this mutualistic fungus?

How do eukaryotes differ from the other two domains?

The Eukarya differ from the Archea and Bacteria in that their cells are eukaryotic, meaning they contain a membrane enclosed nucleus and other membrane enclosed organelles. Archea and Bacteria have prokaryotic cells, meaning their cells do not contain a membrane enclosed nucleus or other membrane enclosed organelles

Suppose a certain fungus is a mutualist that lives within an insect host, yet its ancestors were parasites that grew in and on the insect's body. What derived traits might you find in this mutualistic fungus?

The ancestors of such a mutualist most likely secreted powerful enzymes to digest the body of their insect host. Since such enzymes would harm a living host, it is likely that the mutualist would not produce such enzymes or would restrict their secretion and use.

dikaryon? plasmogamy? karyogamy?

The dikaryon is a nuclear feature which is unique to certain fungi. Compatible cell-types can fuse cytoplasms. When this occurs, the two nuclei of two cells pair off and cohabit without fusing. This can be maintained for all the cells of the hyphae by synchronously dividing so that pairs are passed to newer cells. plasmogamy: fusion of cytoplasm karyogamy: fusion of nuclei

Once life began, what types of organisms lived on Earth for the next 2 billion years?

The earliest direct evidence of life comes from fossils of prokaryotes that date to 3.5 billion years ago. Fossil evidence also shows that for the next 2 billion years (3.5 to 1.5 billion years ago), life on Earth consisted entirely of unicellular organisms. In fact, from 3.5 billion years ago to 1.8 billion years ago, all of Earth's organisms were prokaryotes; around 1.8 billion years ago, these unicellular prokaryotes were joined by unicellular eukaryotes (multicellular eukaryotes emerged about 1.3 billion years ago).

What is the endosymbiont theory?

The endosymbiont theory is the theory that mitochondria and chloroplasts/other plastids were originally prokaryotes that gained entry into a host cell either as undigested prey or as internal parasites.

Explain the endosymbiotic theory for the origin of mitochondria and chloroplasts. What is the evidence?

The endosymbiotic hypothesis for the origin of mitochondria (and chloroplasts) suggests that mitochondria are descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm. The ribosomes of mitochondria and chloroplasts also resemble the smaller ribosomes of bacteria, and not the large eukaryotic ribosomes. This is more evidence that the DNA originated inside of the organelles, and is separate completely from the eukaryotic DNA. This is consistent with endosymbiotic theory.

Do speciation rates in closely related clades of flowering plants show that flower shape is correlated with the rate at which new species form or that flower shape is responsible for this rate? Explain.

The fact that the clade with bilaterally symmetrical flowers had more species establishes a correlation between flower shape and the rate of plant speciation. Flower shape is not necessarily responsible for the result because the shape (that is, bilateral or radial symmetry) may have been correlated with another factor that was the actual cause of the observed result. Note, however, that flower shape was associated with increased speciation rates when averaged across 19 different pairs of plant lineages. Since these 19 lineage pairs were independent of one another, this association suggests—but does not establish—that differences in flower shape cause differences in speciation rates. In general, strong evidence for causation can come from controlled, manipulative experiments, but such experiments are usually not possible for studies of past evolutionary events.

What were the first land plants?When did they arise?

The first land plants appeared around 470 million years ago, during the Ordovician period, when life was diversifying rapidly. They were non-vascular plants, like mosses and liverworts, that didn't have deep roots

Alpha proteobacteria were used as the outgroup to estimate the tree shown in Figure 28.26. Explain why these bacteria were selected as the outgroup rather than other bacterial or archaeal lineages.

The genes used to estimate the tree shown in Figure 28.26 were transferred from an alpha proteobacterium to an early eukaryote. Based on the sequences of these genes, the eukaryotes should be more closely related to alpha proteobacteria than they are to any other lineage of prokaryotes. Thus, alpha proteobacteria are well suited as an outgroup to the eukaryotes (the group of species whose relationships we are trying to determine).

What is the phylogenetic relationship between plants and algae? How do we know?

The green algae and land plants form a monophyletic lineage (the chlorophytes) that contains both protistan and higher taxa (Graham, 1996). An important issue regarding the evolution of this green lineage that still remains in question is the identity of the green algal (i.e. flagellate) ancestor of land plants.

Using the analogy of a 1-hour countdown timer, when did prokaryotes originate? When did the colonization of land occur?

The horizontal time scale indicates that prokaryotes originated 3.5 billion years ago and that the colonization of land took place 500 million years ago. On a 1-hour time scale, this indicates that prokaryotes appeared about 46 minutes ago, while the colonization of land took place less than 7 minutes ago.

What is the difference between gymnosperms and angiosperms?

The key difference between angiosperms and gymnosperms is how their seeds are developed. The seeds of angiosperms develop in the ovaries of flowers and are surrounded by a protective fruit. ... Gymnosperm seeds are usually formed in unisexual cones, known as strobili, and the plants lack fruits and flowers.

Compare Figure 31.5 with Figure 13.6. In terms of haploidy versus diploidy, how do the life cycles of fungi and humans differ?

The majority of the fungal life cycle is spent in the haploid stage, whereas the majority of the human life cycle is spent in the diploid stage.

What would the human life cycle be like if we had alternation of generations? Assume that the multicellular diploid stage would be similar in form to an adult human.

The multicellular diploid stage of the life cycle would not produce gametes. Instead, both males and females would produce haploid spores by meiosis. These spores would give rise to multicellular male and female haploid stages—a major change from the single-celled haploid stages (sperm and eggs) that we actually have. The multicellular haploid stages would produce gametes and reproduce sexually. An individual at the multicellular haploid stage of the human life cycle might look like us, or it might look completely different.

Based on Figure 30.4, compare and contrast the function of pollination and fertilization in sexual reproduction in pines.

The pine life cycle illustrates heterospory, as ovulate cones produce megaspores and pollen cones produce microspores. The reduced gametophytes are evident in the form of the microscopic pollen grains that develop from microspores and the microscopic female gametophyte that develops from the megaspore. The egg is shown developing within an ovule, and a pollen tube is shown conveying the sperm. The figure also shows the protective and nutritive features of a seed.

We are pretty sure that LUCA had a DNA genome and proteins. How do we know?

all known living cells have DNA and proteins

Explain how the pine life cycle in Figure 30.4 reflects the five adaptations common to all seed plants.

The pine life cycle illustrates heterospory, as ovulate cones produce megaspores and pollen cones produce microspores. The reduced gametophytes are evident in the form of the microscopic pollen grains that develop from microspores and the microscopic female gametophyte that develops from the megaspore. The egg is shown developing within an ovule, and a pollen tube is shown conveying the sperm. The figure also shows the protective and nutritive features of a seed.

Would you expect the plastid DNA of photosynthetic dinoflagellates and diatoms to be more similar to the nuclear DNA of plants (domain Eukarya) or to the chromosomal DNA of cyanobacteria (domain Bacteria)? Explain.

The plastid DNA would likely be more similar to the chromosomal DNA of cyanobacteria based on the well-supported hypothesis that eukaryotic plastids (such as those found in the eukaryotic groups listed) originated by an endosymbiosis event in which a eukaryote engulfed a cyanobacterium. If the plastid is derived from the cyanobacterium, its DNA would be derived from the bacterial DNA.

What features not present in seedless plants have contributed to the success of seed plants on land?

The reduced gametophytes of seed plants are nurtured by sporophytes and protected from stress, such as drought conditions and UV radiation. Pollen grains, with walls containing sporopollenin, provide protection during transport by wind or animals. Seeds have one or two layers of protective tissue, the seed coat, that improve survival by providing more protection from environmental stresses than do the walls of spores. Seeds also contain a stored supply of food, which provides nourishment for growth after dormancy is broken and the embryo emerges as a seedling.

You should be familiar with the major groups of seed plants.

The seed plants are often divided arbitrarily into two groups: the gymnosperms and the angiosperms. The basis for this distinction is that angiosperms produce flowers, while the gymnosperms do not.

The bacterium Wolbachia is a symbiont that lives in mosquito cells and spreads rapidly through mosquito populations. Wolbachia can make mosquitoes resistant to infection by Plasmodium; researchers are seeking a strain that confers resistance and does not harm mosquitoes. Compare evolutionary changes that could occur if malaria control is attempted using such a Wolbachia strain versus using insecticides to kill mosquitoes.

The two approaches differ in the evolutionary changes they may bring about. A strain of Wolbachia that confers resistance to infection by Plasmodium and does not harm mosquitoes would spread rapidly through the mosquito population. In this case, natural selection would favor any Plasmodium individuals that could overcome the resistance to infection conferred by Wolbachia. If insecticides are used, mosquitoes that are resistant to the insecticide would be favored by natural selection. Hence, use of Wolbachia could cause evolution in Plasmodium populations, while using insecticides could cause evolution in mosquito populations.

Suppose that you sample the DNA of two mushrooms on opposite sides of your yard and find that they are identical. Propose two hypotheses that could reasonably account for this result.

The two mushrooms might be reproductive structures of the same mycelium (the same organism). Or they might be parts of two separate organisms that have arisen from a single parent organism through asexual reproduction (for example, from two genetically identical asexual spores) and thus carry the same genetic information.

Why do some biologists describe the mitochondria of diplomonads and parabasalids as "highly reduced"?

Their mitochondria do not have an electron transport chain and so cannot function in aerobic respiration.

How do prokaryotes get carbon and energy?

They may get energy from light (photo) or chemical compounds (chemo). They may get carbon from carbon dioxide (autotroph) or other living things (heterotroph). Most prokaryotes are chemoheterotrophs. They depend on other organisms for both energy and carbon.

In Figure 29.17, if fertilization occurred between gametes from one gametophyte, how would this affect the production of genetic variation from sexual reproduction?

Three mechanisms contribute to the production of genetic variation in sexual reproduction: independent assortment of chromosomes, crossing over, and random fertilization. If fertilization were to occur between gametes from the same gametophyte, all of the offspring would be genetically identical. This would be the case because all of the cells produced by a gametophyte—including its sperm and egg cells—are the descendants of a single spore and hence are genetically identical. Although crossing over and the independent assortment of chromosomes would continue to generate genetic variation during the production of spores (which ultimately develop into gametophytes), overall the amount of genetic variation produced by sexual reproduction would drop.

Contrast how sperm reach the eggs of seedless plants with how sperm reach the eggs of seed plants

To reach the eggs, the flagellated sperm of seedless plants must swim through a film of water, usually over a distance of no more than a few centimeters. In contrast, the sperm of seed plants do not require water because they are produced within pollen grains that can be transported long distances by wind or by animal pollinators. Although flagellated in some species, the sperm of seed plants do not require mobility because pollen tubes convey them from the point at which the pollen grain is deposited (near the ovules) directly to the eggs.

What did plants evolve from? What are some of the key traits that appeared in plants that are absent in their ancestor?

Traits: 1.Alternation of generations 2.Multicellular gametangia 3.Walled spores produced in sporangia 4.Waxy cuticle 5.Apical meristem

Why is it accurate to say that Ulva is truly multicellular but Caulerpa is not?

Ulva contains many cells and its body is differentiated into leaflike blades and a rootlike holdfast. Caulerpa's body is composed of multinucleate filaments without cross-walls, so it is essentially one large cell.

How does the life cycle of seed plants differ from ferns and mosses?

Unlike nonvascular plants, all vascular plants—including seedless vascular plants—have a dominant sporophyte generation. Seedless vascular plants include clubmosses and ferns. ... The resulting zygote develops into an embryo that becomes a new sporophyte plant. Then the cycle repeats

Why are protists considered to be a paraphyletic group?

While it is likely that protists share a common ancestor, the exclusion of other eukaryotes in its group means it doesn't form a monophyletic clade.

If a nonpathogenic bacterium were to acquire resistance to antibiotics, could this strain pose a health risk to people? In general, how does DNA transfer among bacteria affect the spread of resistance genes?

Yes. Genes for antibiotic resistance could be transferred (by transformation, transduction, or conjugation) from the nonpathogenic bacterium to a pathogenic bacterium; this could make the pathogen an even greater threat to human health. In general, transformation, transduction, and conjugation tend to increase the spread of resistance genes.

Prokaryotes lack the nucleus found in eukaryotic cells. As a result, prokaryotic cells do not contain

a nuclear membrane

Endosymbiosis

a relationship between two species in which one organism lives inside the cell or cells of another organism

What are the three shapes of bacteria?

a.Coccus b.Bacillus c.Spirochetes

Green algae are divided into two main groups, the charophytes and the __________.

chlorophytes

Which of the following is not a structure used for locomotion in protists?

flagella, cilia, pseudopodia, undulating membrane

What are the major angiosperm taxa?

•Basal angiosperms •Magnolids •Monocots •Eudicots

What are some derived features of angiosperms that distinguish them from gymnosperms?

•Flowers and fruits that encourage seed dispersal •Ovule enclosed in an ovary •Double fertilization

Describe the moss life cycle.

•When in an ideal habitat (moist and close to the ground), moss spores will develop into gametophytes •Gametes produce gametangia, which are structures that produce gametes •Archegonia: female gametangia •Antheridia: male gametangia •Flagellated sperm swim through water to the egg to fertilize it inside the archegonium •Sporophytes will develop. Sporophytes are attached to and are dependent on the gametophyte. The gametophyte will nourish and support the plant Gametophytes, spores, sperm, and eggs are all haploid. Zygotes and their resulting sporophytes are diploid.