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envr 202 > lectures 6-8 > Flashcards

lectures 6-8 Flashcards

1
Q

What is biological evolution?

A

The gradual change in the inherited traits of a population.

Survival and reproduction are the main factors of evolution.

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2
Q

What are the two ideas established in Darwin’s book “On the Origin of Speicies”?

A
  1. The tree of life:
    - all species on earth have evolved from other species (perhaps from one).
  2. Natural selection:
    - organisms are well-adapted to their environments because they accumulate, over the generations, traits that enable them to survive and/or reproduce better than organisms lacking those traits.
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3
Q

Explain natural selection.

A
  1. Individuals in a population differ in their traits.
  2. Some traits confer an advantage (in a given environment).
  3. Individuals that have these traits survive and reprouce better than others.
    - selection is on phenotype.
  4. If difference are heritable, the frequency of advantageous traits will increase in the next generation.
    - evolution is due to changing genotype.
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4
Q

What is a gene?

A

A self replicating DNA unit that occupies a specific location on a chromosone and determines a particular characteristic in an organism.

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5
Q

What is an allele?

A

A variant (different) form of a given gene (section of DNA) that codes for something (e.g. a trait).

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6
Q

What 2 factors explain biological evolution?

A
  1. Change in allele frequencies in a population over time.

2. Driven by variation in reproductive success (fitness).

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7
Q

Are all differences in traits heritable?

A

No.

Phenotype: interacion between the genotype and the environment.

Plasticity: environmentally determined, non-heritable, trait differences.

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8
Q

How do prokaryotes reproduce? How do prokaryotes transfer genetic information?

A

Binary fission.

An enzyme breaks apart the two DNA strands. Other enzymes attach complemnetary bases to the strands. Another enzyme checks for mistakes and a DNA repair enzyme fixes them.

Result: two identical strands to the original.

Genetic variation through mutation.

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9
Q

What are the 4 modes of transmitting genetic information?

A
  1. Binary fission: asexual reproduction in prokaryotes, creates new prokaryotes, and some genetic diversity.
  2. Conjugation: sharing plasmids (seperate rings of DNA) between cells.
    - NOT reproduction, introduces genetic variation.
  3. Transformation: a prokaryote picks up a plasmid from the environment and obtains genetic instructions.
    - NOT reproduction, introduces genetic variation.
  4. Transduction: a virus relocates DNA from one prokaryote to another via viral replication cycles.
    - NOT reproduction, introduces genetic variation.
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10
Q

How does a eukaryote have a different genetic strucutre than a prokaryote?

A

Its genetic material is organized into mulitple linear chromosones. Each chromosone consists of one long molecule of DNA.

After DNA replication, there are two identical sister chromatids.

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11
Q

Explain the process of asexual reproduction in a single-celled eukaryote.

A
  1. Duplication.
  2. Mitosis.
  3. Fission.
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12
Q

What is mitosis?

A

Duplicate chromosones line up and are pulled to opposite sides of of the parent cell.

The cells then divide (fission) to produce daughter cells.

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13
Q

What is the difference between eukaryotic asexual and sexual reproduction.

A

2 parents are needed for sexual reproduction. The cell goes through meiosis.

There is much greater genetic variation possible in sexual reproduction.

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14
Q

Explain the process of eukaryotic sexual reproduction.

A

2 gametes fuse to form a diploid zygote. 6 chromosones (3 from each parent) become uncondensed inside the new nuclear membrane.

The diploid ges through reassortement or reassorment + recombination. The chromosones duplicate and homologuous chromosones line up in the center of the cell. The homologous chromosones seperate and move to opposite sides of the cell = 2 groups of 3 chromosones (with replicated sister chromatids).

Sister chromatids seperate = 4 groups of 3 chromosones each.

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15
Q

What are the consequences of eukaryotic sexual reproduction?

A
  1. Mate searching costs.
    - probability of finding a mate declines when the population size is smaller.
  2. Competition.
    - behavioral effects.
  3. Display costs.
    - costs associated to displaying something for a mate.
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16
Q

What are 2 direct advantages of sex?

A
  1. DNA repair mechanism.

2. Masking mutations - higher chance that one copy works.

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17
Q

How did eukaryotes arise during evolution?

A
  1. Diversified prokaryotic life.
  2. Oxygenated world.
  3. Different reproductive approach (massive variation = accodmation for environmental fluctuations).
  4. Many organelles.
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18
Q

What are the eukaryotes common ancestors?

A

Two prokaryote domains: bacteria and archaea.

Genetically closer to archaea than bacteria.

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19
Q

What is the biochemical evidence for the archaea as the eukaryote’s ancestor?

A

DNA sequences data from genes in the nucleus of eukaryotes suggest that eukaryotes are more closely relates to archaea than bacteria.

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20
Q

What is the biochemical evidence for the bacteria as the eukaryote’s ancestor?

A

Mitochondria and chloroplasts (eukaryotic organelles) have their own circula DNA and prokaryotic type ribosomes. Mitochondrial DNA is inherited from the mother. This makes it more similar to bacteria.

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21
Q

What is the conclusion about the eukaryotic ancestors?

A

Chimeric model: eukaryotes are cobbled together from bits and pieces of other organisms through endocytosis.

A fusion of prokaryotes that resulted in the larger, more complez eukaryotic cell.

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22
Q

What is endocytosis?

A

A substance gains entry into a eukaryotic cell; the cell membrane warps itself around the particle and pinches off a vesicle inside the cell.

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23
Q

What is the endosymbiotic theory?

A

Suggests that mitochondria, chloroplasts and possibly other organelles, were acquired by a primitive cell through endocytosis.

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24
Q

Explain the process of comparing lines of descents with simple phenotypic traits.

A

Simpel observations and measurements to make comparisons among living and fossil organisms.

Simple inferences can evaluate degrees of similarity and account for patterns of change in time. This allows us to reconstruct relationships and lines of descent and patterns of change.

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25
Q

What are the probelms with the process of comparing lines of descents with simple phenotypic traits.

A
  1. Environmental influence on phenotypes.
  2. Ontogenetic changes.
    - two organisms that look the same, but are different.
  3. Identifying ‘derived’/ancestral traits.
  4. Insufficient data from living and fossil organisms.
  5. Lack of universal traits.
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26
Q

What are the chances of finding a fossil?

A

Extremely small.

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27
Q

What are the 4 lines of evidence for lines of descent?

A
  1. Selection experiments.
  2. Comparative biology: form, function.
  3. Fossil records.
  4. Molecular phylogeny.
    - proteins
    - nucleotides
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28
Q

What are the advantages with comparing lines of descent with molecular traits?

A
  1. Nucleotide sequences provide a direct record of all information stored in the genome.
  2. No environmental or ontogenetic effects on the observed traits.
  3. Potentia for universal traits, which we can build genetic relationships back to the first organisms.
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29
Q

What are the difficulties with comparing lines of descent with molecular traits?

A
  1. Traits observed only with use of sophisticated technology.
  2. Inferring patterns of change in time not intuitive.
  3. Back mutation at a site in the sequence is possible and complicates analysis.
  4. Assuming constant molecular clock.
    - mutations can go back and forth like no evolution happened.
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30
Q

How do we reconstruct phylogeny (lines of descent)?

A
  1. Acquire nuclotide sequence data.
    - sampled part of genome depends on how far back in time the relationships of interest lie.
  2. Align sequences from different organisms.
    - allow for mistmatches due to point mutations, insertions, and deletions.
  3. Reconstruct most likely lines of descent.
    - assess the minimal number of steps required to change from one sequence to another and use this as a measure of relatedness across all the organisms in the analysis.
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31
Q

Why did eukaryotic diversity increase?

A
  1. Increase in size of genome.
    - more proteins, enzymes coded for.
  2. Sexual reproduction.
    - meiosis increases possible variation/mixing.
  3. Increase in structural complexity.
    - locomotion, protection.
  4. Ecological changes.
    - O2, energy sources.
    - physical/biological landscape.
    - photsynthesis in shallow water.
32
Q

How did multicellular life originate?

A

The colonial hypothesis.
- change will persist and pass on if there is an advantage to that original mutation or change.

Colonial protists and algae illustrate the intermediate stage of complexity.

Colonial life allows evolution of seperate functions for individual cells.

  • feeding, reproduction, locomotion, etc.
  • different metabolic pathways turned on and off.

Not all cells are identical, the expression of genes depends on the environment. Different functions and complexity.

33
Q

Explain the Ediacaran diversity.

A

Variety of forms (vendian animals).
- leaflike fronds, round pads, worms.

Some reseble jellyfish, sponge. Most are unique and unlike known animals.

34
Q

Explain the diversity of the Ediacaran Seascape circa.

A

In the late Precambrian era, life is in the ocean but not yet on land.

Small shelly fossils in ocean sediments. Soft parts are not preserved - we have no idea what organism constructed the shells.

35
Q

What are the advanatges and costs associated to shells and hard body parts?

A

Advantages:
- protection, locomotion, killing prey.

Costs:

  • long development, need for resources and right conditions (calcium, phosphorus).
  • ocean acidification dissolves the shells.
  • energetic consequences.
36
Q

Explain the Burgess Shale Diversity.

A

Explosion of life on earth, many fossils arre better preserved at this time due to good environmental conditions.

Ancestors of many modern groups.
- arthropods, worms, sponges, jellyfish.

Many mystery organisms.
- possibly failed lines of evolution or victims of chance.

37
Q

What is Pikaia?

A

Ancestor of chordates, vertebrates, mammals, and humans.

38
Q

What is the Cambrian Explosion?

A

Diversification in the animal kingdom.

All modern animal body plans established in less than 25 million years. Changes since then are just variatiosn on those established plans.

39
Q

What explains the Cambrian explosion?

A

A combination of biological and environmental factors.

Increase in genetic complexity.
- enough DNA to code for a much greater range of structural and metabolic proteins.

Increase in structural complexity.

  • more body parts for variation and selection to act on.
  • more strucutres that were adapted to multiple functions.

Change in environment and ecological relationships.

Much new diversity was in shallow water marine environments (exposed to sunlight = photosynthesis, more nutrients - sets conditions by which other features can arise).

40
Q

Explain the concept of “fitness landscape”.

A

Depending on the environment, the fitness landscape will be different.

As complexity increases, the fitness landscape roughens.

  • new species and characteristics have new pressures and advantage.
  • a fluctuating environment changes the fitness landscape.

Intermediate species are more at risk, it is better to be big or small.

41
Q

Explain the predatory-prey “arms race.”

A

Mutations create variation in organism traits.

There is a co-evolution: a selection of favorable mutatiosn in a biotic interaction between different organisms.

NOT the organism that selects new traits in response to the prey/predator.

42
Q

Does evolution have a purpose?

A

NO. Variation arises through chance mutations.

It is selection that decides which variatiosn will survive or succeed, not the organisms.

Always interpret evolution in terms of chance variations, selection of random variation, probabilities of survival, not purpose and progress toward an objective.

43
Q

What are the charcteristics of the early protezoic era?

A

Beginning: primarily bacteria/archae, oxigenation event.

  • photsynthesis evolves.
  • eukaryotes (cells with nucleus) evolve.
  • proliferation of bacterial mats.
  • oxygen began builing in the atmosphere.
  • formation of ozone layer.
  • animals: dominated by soft bodied sessile or slow moving organisms.
44
Q

What are the charcteristics of the late protezoic era?

A

End of proterozoix era: multicellular photosynthesizers begin to appear, algae. late stages.

  • emergence of shells and “hard bodies” - begin to dominate the fossil record.
  • animals becomre more motile.
  • explosion of evolution of new body types in animals.
45
Q

What are the characteristics of the Ordovician period?

A

Mix of continents (break up of super continent) and shallow ocean shelves, rising and falling sea levels.

First true verterbrates (fish with jaws) evolve from Pikaia.

Life was still underwater- aquatic ecosystem with diverse plants and life, multicellular, motile.

46
Q

What are the 8 bariers to adapting to land?

A
  1. Desiccation.
  2. Gas exchange.
  3. Reproduction.
  4. Buoyancy.
  5. Temperature fluctuations.
  6. Vision and hearing (animals only).
  7. Mineral nutrition (plant only).
  8. Harmful UV radiation.
47
Q

Explain the challenge of desiccation as a barrier to adaptating to land.

A

Desiccation = drying out.

  1. Aquatic organisms are adapted to being surrounded by water - dry out easily.
  2. Cannot be waterproof: need to allow for the passage of water and gases in and out of the body.
  3. Smaller organisms dry out faster.
    - greater surface area to volume ratio.
    - internal space = water storage.
    - surface area = water loss.
48
Q

Explain the challenge of gas exchange as a barrier to adapting to land.

A

Gases (CO2 and O2) are absorbed differently depending on whether they are in air or dissolved in water.

There is a need for a new system of gas exchange.

Gases are diffused differently in and out of war = need for a new respiratory system.

49
Q

Explain the challenge of reproduction as a barrier to adapting to land.

A
  1. Aquatic organisms need water to facilitate reproduction.

2. Male and female gametes (egg and sperm) are released into the water fir fertilization and development.

50
Q

Explain the challenge of buoyancy as a barrier to adapting to land.

A

Water and water presures support body tissues, air does not.

Land plants and animals needed supporting structures.

51
Q

Explain the challenge of temperature fluctuation as a barrier to adapting to land.

A

Seawater temperature is slow and change very little.
- the sea surface changed by 4C in the past few centuries.

Land heats up quicker and has larger changes.
- can change as much as 30C in 24h.

52
Q

Explain the challenge of vision and hearing as a barrier to adapting to land.

A

Light and sound waves move differently through water compared to air.

There is a need to adjust to vision and hearing.

53
Q

Explain the challenge of mineral nutrition as a barrier to adapting to land.

A

Water contains dissolved minerals for added nutrition - no need to scanvang for materials, the water brings them to you.

Many aquatic animals are sessile (immobile) - they need a way to supplement on land.

They need a way to get nutrition on land (e.g. plants developped roots).

54
Q

Explain the challenge of harmful UV radiation as a barrier to adapting to land.

A

Water can filter UV light and protects life.

Oxygen creates the ozone layer - filters out enough UV radiation for life to survive on land.

UV radiation can damage tissue and DNA (e.g. cancer).

55
Q

Who were the first to colonize life on land? Why?

A

Cyanobacteria, green algae (eukaryotes).

Plants are autotrophs - it was advantageous to grow near the surface, in shallow waters, on coastal shelves.

56
Q

How did green algae evolve?

A

Green algae were exposed to periods of drought.

There was a selection for individuals who could tolerate extended periods of desiccation.

Over time, evolved from algae to more complex form that coudl survive entirely on land (moss, liverwort).

57
Q

What is the biological evidence for the plant’s adaptation to life on land?

A

Existing species had traits which likely predisposed them to being able to adapt terrestrial environments.

58
Q

What is the fossil evidence for the plant’s adaptation to life on land?

A

Fossil evidence in this period supports the emergence of terrestrial life.

Suggests that life consisted of plants.

59
Q

How did plants adapt to desiccation?

A
  1. Developed mutiple cell layers and a layer of wax (cuticle - prevents drying out) on the epidermis.
  2. Evolved roots or root-like strucutres.
    - direct movement of water into the body.
60
Q

How did plants adapt to gas exchange?

A
  1. Evolved specific pore (stomata) to allow for gas to enter the body.
    - plants can open/close stomata if water is limited/abundant.
  2. Could be closed to prevent the plant from drying out.
61
Q

How did plants adapt to reproduction?

A

Evolved spores which could survive desiccation.

  • still depended on water to move them.
  • eventually evolved seeds - more desiccation tolerant than spores.
62
Q

How did plants adapt to buoyancy?

A

Evolved strong fibers and compounds such as lignin and cellulose.

Purely structural support (wood and stuff).

63
Q

How did plants adapt to temperature fluctuations?

A

Traits that evolved to prevent desiccation eventually helped plants survive extreme temperature fluctuations.

Much later, plants evolved methods (e.g. dormancy) to survive in extreme environments (desert, winter).

  • dropping leaves to becomes dormant.
  • transpiration when it is hot.
64
Q

How did plants adapt to mineral nutrition?

A

Roots allowed plants to take minerals right out of the soil.

Some plants formed symbiotic associations with microbes: exchange minerals for sugars.

65
Q

Why did animals move onto land 30-100MY after plants?

A

Plants: autotrophs
- get their energy mainly from the sun.

Animals: heterotrophs

  • get energy by consuming organic matter (plants, other animals).
  • before terrestrial plants: no food.
66
Q

Who were the first land animals?

A

Arthropods

Cambrian-era fossils of arthropods tracks on land, even before plants (temporary, may have been fleeing predation).

Scorpions, millipedes, springtails present in Devonian - rapid increase in diversity.

Exoskeleton = ability to support their body and resistance to desiccation.

67
Q

Which ancestor of ours emerged onto land first? When?

A

A lobe-finned fish during the Late Devonian period. First evidence of leap of life on land.

Lived on land, closely tied to water for reproduction, etc.
- not fully terrestrial, might go to water for reproduction.

Shared ancestor of all tetrapods (amphibians, mammals, reptiles).

  • evolved from pikai (spine and backbone).
  • 4 limbs.
68
Q

Why could so many groups colonize land?

A

Many animals preadapted to life on land.

Structures that evolved for other uses are also effective for living on land.
- e.g. exoskeleton of arthropods, vertebrates skeletons, types of movement = easier buoyancy on land.

Coelacanth’s fins moved with a rowing=crawling motion = preadaptation.

69
Q

How did animals adapt to desiccation?

A
  1. Physical: waxy coating or exoskeleton.
    - e.g. arthropods, reptiles (scales).
  2. Behavioural: live in damp habitats, active at night.
    - e.g. amphibians.
  3. Physiological: concentrate waste, remove water and excrete waste as uric acid (drier, less water).
    - e.g. reptiles.
70
Q

How did animals adapt to gas exchange?

A

How to get oxygen into cells?

  • O2 is easily absorbed from water, not air.
  • O2 must be absorbed across a moist membrane.
  1. Single celled or simple organisms: oxygen can diffuse across the cell memebrane.
  2. Multicellular aquatic animals: gills - membrane where O2 diffuses into the body.
71
Q

What is the challenge with gas exchange for animals? What are the solutions?

A

How to keep the membranes wet in dry air without losing water.

  1. Insects.
    - amll openings in the exoskeleton (spiracles).
    - network of tubes branching throughout the body (tracheae).
  2. Vertebrates.
    - small opening (trachea).
    - sacs with large surface area and many blood vessels for gas exchange (lungs).
72
Q

How did animals adapt to reproduction (pre-fertilization)?

A

The ovum and sperm must be kept wet (usually fertilized in water).

Internal fertilization.

  • keep ova inside the body to prevent desiccation.
  • fertilization inside the female.

Internal fertilization also mazimizes th eprobability of gametes encountering one another.
- targeted reproduction, more chances of fertilization.

73
Q

How did animals adapt to reproduction (post-fertilization)?

A

The zygote is inside the female - the embryo needs to get outside. Embryo faces the same challenges (desiccation, nutrients, gas exchange, waste disposal).

Solution: modify the egg for terretrial life.

  • self contained world.
  • major energy investment by the female.
74
Q

What are the characteristics of the amniotic egg?

A
  1. It is a major evolutionary adaptation in reptiles - it allowed eggs to be laid on dry land.
    - does not desiccate, does not need to be laid in water.
  2. Temperature fluctuation is a problem.
    - bury in temperature-buffering material.
    - incubation behavior.
  3. Fewer eggs produced.
    - need more resource per egg.
  4. Nesting parent is an easy prey.
75
Q

How did animals adapt to buoyancy?

A
  1. Arthropods (e.g. insects).
    - exoskeleton made of chitin.
  2. Vertebrates (e.g. mammals).
    - internal skeleton made of cartilage and bone.
  3. Molluscs.
    - external shell (calcium).
    - hydrostatic skeleton (fluid pressure inside the body).
76
Q

How did animals adapt to temperature fluctuation?

A

Development of strategies for thermoregulation.

  1. Homeothermy = the ability to regulate the internal body temperature.
  2. . Both active and passive strategies.
    - metabolism (high food requirement).
    - behavior (reptiles move around in colder areas to control their body temeprature).
77
Q

How did animals adapt to vision and hearing?

A
  1. Vision.
    - early eyes: filled with water from the environment.
    - terrestrial eyes: sealed chamber filled with fluid.
    - eye shape chnage to resend light and focus, refraction of light is different in air/water.
  2. Hearing.
    - early hearing adapted to wavelengths traveling through water.
    - later specialized in some species to airbrone wavelengths.
    - cochlea in mammals still contains fluid for sound transmission.

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