Ecology of Algae and Prokaryotes: Diversity, Evolution, and Symbiosis, Exams of Biology

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BIOL 200 Midterm | 100% Correct Answers |

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The ecology of algae in aquatic ecosystems parallels that of plants in terrestrial ecosystems. Make three points to support this statement. - ✔✔ Aglae and mosses/plants have similar features such as:

• branched apical growth
• cuticles
• asymmetrical flagellated cells
• cellulose, thylakoids, chlorophyll b, some have 2 flagella... If some Euglenoids have the same pigment as green algae and higher plants, why are they not so closely related? - ✔✔secondary endosymbiosis Why evolve towards a substantial part of the cycle being diploid phase? - ✔✔- most of life cycle is in gametic meiosis in the diploid phase and this permits diversity
• heterozygosity occurs in this phase
• all genes expressed in haploid phase are subject to selection and mutation but reduction in this phase leads to protection of the gene.
• decrease in haploid phase reduces the uv or other fatal factors affecting the gene Describe the primary and secondary mechanisms that generate biological diversity across the tree of life
• ✔✔Primary: natural and sexual selection based on the combination of genetic mutation and environmental/spatial and temporal heterogeneity Secondary: features and impacts of diversity that generate more diversity so development of more structures, colonization, development of more advanced reproductive systems, interactions... What are some structural differences between prokaryotes and eukaryotes? - ✔✔Eukaryotes have:
• dna in nucleus
• membrane bound organelles
• cytoskeleton

• flagella
• larger ribosomes
• chromosome pairs Why do people call viruses borrowed life? - ✔✔they can grow provide and produce but only with a host. They are not able to generate life on their own. What is a thermophilic environment? - ✔✔alkaline environment often found in deep sea vents protected from UV it is extremely harsh/hot environment. What are some biological characteristics of prokayrotes? - ✔✔surface area to volume ratio is important, they are unicellular, one double stranded circular chromosome, lack nucleus, no sexual reproduction What are some benefits to being 'so small?' - ✔✔- intimate contact with surroundings
• high rate of living
• rapid reproduction
• boom and bust
• but water is viscous (neg) List the four steps of fission - ✔✔1. duplication of circular chromosome

2. cell elongation
3. ingrowth of plasma membrane
4. ingrowth of cell wall What are 3 reasons for prokaryotic success in early earth? - ✔✔- small size

• rapid generation time
• prolonged dormancy
• diverse mechanisms

What is co-evolution? Give an example. - ✔✔rumen bacteria we see in Cows. They can regurgitate their cud which is why they can digest grass. grasses evolved around the same time as rumen organisms.represents co-evolution. calf gets symbionts from mom's mucus. another example is soil bacterial symbioses of nitrogen fixing association with legumes. What evidence supports serial endosymbiosis? - ✔✔- Mitochondria and chloroplasts resemble bacteria in many ways (in size, appearance, 2 lipid bilayer etc

• Cyanobacteria and chloroplasts both have chlorophyll and producing oxygen during photosynthesis What are the benefits of eukaryotic asexual reproduction? - ✔✔- less energy is required
• no mate is required
• faster generation growth so more rapid reproduction
• if the genotype is suited for the environment, why change How did alternation of generations evolve? - ✔✔- diploid phase expanded
• haploid dominant turned to diploid expansion turned to zygotic meiosis and eventually alt of generations
• meiosis created more recombination
• the increase in the number of gametes came from this too How are fungi different and diverse? - ✔✔-eukaryotes with sexual stages in the life cycle therefore more potential for species because of meiosis and more potential for genetic diversity.
• chemotropic only
• range of catabolic enzymes and defence compounds
• cell walls have chitin
• reproduce with cytoplasmic and nuclear fusion stages (dykaryotic) Where do fungi get their nutrient acquisition from the environment? - ✔✔- rigid cell walls preclude phagocytosis
• fungi can break down organic matter and grow where water is limited
• they can break down dry wood

• they can produce water though metabolism Why is there a trend in extended diplomatic stage in advanced fungi? - ✔✔- if there was no gap between haploid and diploid stage it would be alternation of generation
• may generate variability
• greater potential for phenotypic variability and evolutionary adaptation to changing environment
• enhanced capacity to create genetic variability between 2 nuclei during cell duplication What is symbiosis and what is one example of a parasitic and mutualistic relationship? - ✔✔- close long term allocation with organisms between difference species
• coral reefs and algae (mutual)
• ticks on dogs (parasitic) How were lichens and mycorrhizae likely essential for plants to colonize land? - ✔✔- terrestrial earth was bare and rocky not a lot of water available
• abundant light and co
• lichen initiated development of soil organic matter that stores and supplies nutrients and water
• mychorrhizae lead evolution of roots with branched system that possibly led to stems leaves epidermis, etc etc Structure usually relates to function in living organisms. Provide three distinct examples from prokaryotic organisms to illustrate this concept. - ✔✔Flagellum - motility; Thick cell wall membrane (esp. Gram positives) to resist desiccation; Endospore development to survive periods of unfavourable environmental conditions; Granules (inclusion bodies) for storage of food reserves Describe two lines of evidence supporting the hypothesis that life evolved in deep sea thermal vents - ✔✔a) Thermophiles are particularly frequent at the base of the Tree of Life b) The reducing conditions in vents are consistent with the biochemistry of early life forms (heterotrophic, and anaerobic)

c) Most of the fundamental housekeeping (cellular maintenance) proteins and biochemical processes seem to have a heritage reflecting a hydrothermal environment d) UV levels are low in vents relative to the ocean surface meaning nucleic acid degradation was minimal Briefly explain two different reasons why the evolution of photosynthesis in the cyanobacteria is believed to have been critical to the subsequent development of the diversity of life on Earth (2 x 2 marks). - ✔✔1)Ozone development (O3) associated with an oxygenic atmosphere meant that the organisms at the top of the land or aquatic surfaces were better protected against UV radiation.

2. Endosymbiosis of cyanobacteria led to the evolution of the first and most photosynthetic eukaryotes. The biology of viruses is important to human societies in many different ways. Give three examples to demonstrate this point. - ✔✔a) Smallpox led to the development of vaccines as a preventative medical procedure. b) Viruses such as phages are very important tools in molecular biology. c) Viruses cause many serious human diseases.(AIDS, influenza) Provide 2 reasons to explain why prokaryotes are generally only metabolically active when their cells are in contact with external water. - ✔✔a) diffusion can supply nutrients and organic matter b) diffusion will remove waste excretions c) water is necessary as a metabolite Give three distinct reasons why viral diseases can evolve rapidly. - ✔✔a) Rapid reproduction in host cell b) Nucleic acid mutations during replication cause antigenic drift. c) Nucleic acid reassortment can occur when two strains infect the same cell (antigenic shift). Explain what is meant by the term chemoautotroph, and provide an example illustrating their role in a biogeochemical cycle. - ✔✔A chemoautotroph obtains its energy obtained by chemical oxidation of a reduced compound such as Fe2+, NH4+, S, CH4, and its by reducing CO2 gas to an organic compound such as carbohydrates.

• Chemoautotrophs have globally significant and critically important impacts on the biogeochemical cycling of iron, nitrogen, and carbon cycles

Explain three features that can be used to distinguish members of the Domain Bacteria from the Domain Archaea - ✔✔a) rRNA sequence b) Membrane lipid tails are branched and sometimes linked. c) Some bacteria can photosynthesize d) Bacterial cell walls contain some peptidoglycan, Archaea do not. e) Some Archaea can synthesize methane. Briefly suggest a reason why there is a trend towards a smaller-sized and shorter-lived haploid phase in some of the more evolved taxonomic eukaryotic groups. - ✔✔- decreased time period which uv or other factors could cause fatal mutations to single gene

• genetic recombination in diploid phase leads to genetic diversity
• more time within the life cycle for natural and sexual selection Green algae are believed to be the progenitors of higher plants. Describe three pieces of evidence to support this statement. - ✔✔a) Photosynthetic pigments for both include chlorophyll a and b b) Cell walls contain cellulose, hemicellulose and pectin c) Chloroplast thylakoids are stacked in piles d) Starch is the major storage product e) structural similarities Diversity begets diversity. Explain this central concept of the course, and illustrate it using three separate examples that you have learnt about in this course. - ✔✔Concept: The evolution of traits that enhance diversity give rise to further diversity. i) Evolution of diploidy paved the way for polyploidy which has been such an important mechanism for speciation in higher plants. ii) Diploidy also paved the way for sexual reproduction and the incipient processes of recombination and meiosis that generate further genetic diversity. iii)Evolution of primitive roots (rhizoids) in certain green algae were a precursor to more advanced roots in the highly diverse vascular plants.

A chickadee, a caterpillar, a chanterelle and a cedar are all believed to have evolved from a common pool of ancestral prokaryotes. List four types of evidence to support this hypothesis: - ✔✔a) Nucleic acid mechanism of heredity b) Nucleic acid code c) Cellular organizational patterns d) Energy transformations based on ATP currency Explain two lines of evidence indicating that some Euglenoids gained the capacity to photosynthesize by secondary endosymbiosis? - ✔✔Chloroplasts in the photosynthetic euglenoids were acquired through (secondary) endosymbiosis by an ancestral heterotrophic euglenoid host of an ancestral green algal cell that itself was a result of (primary) endosymbiosis by an ancestral heterotrophic eukaryotic host of a cyanobacterium that became an ancestral chloroplast. Dry rot' refers to decomposition of wood in a dry environment by certain fungi but not by bacteria. Explain two distinctive features of fungi that allow them to achieve this process? - ✔✔a) Capacity to translocate water and nutrients along the mycelium from hyphae that are in contact with moist areas to hyphae that are actively decomposing wood in dry areas. b) Certain dry rot fungi can synthesise water as a byproduct of glycolysis c) Synthesize specialised wood-decaying enzymes

1. Compare and contrast fungal and vascular plant reproduction by describing three distinctive features of the genetics and lifecycles of the Kingdom Fungi. - ✔✔a) Sexual reproduction is by zygotic meiosis in most fungi whereas vascular plants have alternation of generations. b) Zygotic (diploid) stage in fungi is unicellular and often represents the dormant highly protected stage of the life cycle that is favoured when environmental conditions are not favourable for growth. c) Cytoplasmic and nuclear fusion are substantially separated in time in many fungi meaning there is a distinct and prolonged dikaryotic phase. d) Asexual reproduction is common in most fungi, but a much smaller proportion of vascular plants.
2. Indicate how lichens acquire their carbon and sulfur. - ✔✔Alga fixes CO2 during photosynthesis some of which is used for its own metabolism and some of which is translocated to the fungus. Sulfur is generally acquired from atmospheric deposition of particles and rainfall.