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BIOL 108 > Topic 3: Evolution and Darwin > Flashcards

Topic 3: Evolution and Darwin Flashcards

1
Q

Why is all life on earth-related?

A

It all evolved from a common ancestor

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2
Q

Overall, what was the general sentiment of early thinking of species diversity?

A

Described life as being created, not evolved

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3
Q

According to the Pre-Darwin way of thinking, what was the reasoning behind fossil organisms not resembling living ones?

A

-extinction of species must occur

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4
Q

What are some different reasons given for extinction?

A
  • natural disasters (Cuvier)
  • apparent disappearance of species was actually one species changing slowly into another (Lamarck)
  • supernatural disasters
  • not actually extinct, just hiding
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5
Q

What explanation did Cuvier give for the succession of life-forms in earth’s strata?

A
  • a catastrophe occurs, which results in local extinction and the presence of fossils in the stratum
  • after the catastrophe, a new species will move into the area, followed by another catastrophe and another layer of fossils
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6
Q

What did Cuvier believe about evolution?

A
  • did not believe in evolution, thought that species do not change over time (fixed)
  • believed in the interdependence of organs to survive, if some organs changed, the organism would not survive
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7
Q

What did Lamarck believe about evolution?

A
  • species change over time (evolution) because the characteristics an individual acquires during their lifetime can be passed on to their offspring (thought traits can be passed on in a single generation)
  • the use and disuse of structures results in heritable change eg: giraffes need long necks so they gained them (had an innate drive to improve)
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8
Q

What were the drawbacks of Lamarck’s ideas?

A

-there was no experimental evidence of his ideas and his logic was greatly flawed

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9
Q

Did Lamarck believe in extinction?

A

Said extinction was rare and that species just changed

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10
Q

What were James Hutton’s main ideas?

A
  • uniformitarianism (our present is the key to the past)

- gradualism (the features of the earth result from a slow accumulation of events- catastrophes are rare)

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11
Q

What significant contributions did Charles Lyell make concerning evolution?

A
  • advocated uniformitarianism and gradualism

- made Hutton’s ideas accessible to a wide audience-including Darwin

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12
Q

Did Darwin write about the survival of the fittest?

A

-the survival of the fittest was not discussed by Darwin, this statement is inaccurate because it only focuses on how the fit will survive and overlooks the aspect of reproductive success (it does not address roots of evolution)

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13
Q

What did Darwin observe on his voyage that was critical in his future theories?

A
  • similarity and dissimilarity in the same species of finches
  • redundant forms from one place to another (common ancestry) but also variation within a region
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14
Q

What were Darwin’s 5 observations?

A
  1. organisms produce many more offspring than survive to reproduce themselves
  2. most populations are relatively stable
    - resources are limited (not enough for all offspring of individuals)
  3. there is variation among individuals within a species (no understanding of genetics)
  4. some variation is heritable
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15
Q

Explain Darwin’s three inferences

A
  1. organisms must compete for limited resources and not all succeed (struggle for existence)
  2. some heritable variations provide individuals with a competitive advantage (allows them to survive in the conditions of their environment and achieve survival/reproductive success)
  3. individuals with advantageous variations are likely to leave more offspring than individuals without these variations
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16
Q

Explain the concept of relative fitness

A
  • Individuals have many traits/variations, some are better for survival, while some are better for reproduction
  • traits that have a high frequency of survival and reproduction are the ones that are passed on
17
Q

Explain the process of “descent with modification”

A
  • explains how species change and diversify over time
  • the idea that a lack of resources results in competition, and some individuals have heritable variations that provide a competitive advantage, making them more likely to leave more offspring than those without variations
  • as a result, have more individuals with that variation than were present in previous generations
  • the overall result is adaptive changes over generations
18
Q

Explain some important characteristics of Natural Selection

A
  • gives rise to adaptations
  • as individuals adapt to different environments, new species may arise over time (over many generations)
  • populations evolve, not individuals (can’t pass traits in a single generation)
  • natural selection acts on existing variation
  • is context-dependent (species change in the context of what will help them survive in their environment)
19
Q

Explain the statement “natural selection has no innate tendency towards perfection”

A

A species cannot be perfectly suited to its environment because then it can’t adapt and survive when the environment changes, therefore there is no tendency to perfectly suit the environment

20
Q

Why can’t acquired traits be inherited?

A

Because acquired traits involve changes in the phenotype, not in the actual DNA (genotype)

21
Q

Phenotypic Variation

A

-involves variation in form, function, and behavior

22
Q

Genotypic Variation

A

-involved variation in the genetic makeup itself

23
Q

What are the conditions for natural selection to act on variation?

A
  • must be expressed in the phenotype (seen by environment)

- must be heritable (caused by genotype)

24
Q

Is Natural Selection random?

A
  • no, natural selection is always directed towards one extreme state/variant
  • however, variations in species are random
25
Q

What are some sources of variation?

A
  • mutation (random changes to DNA)
  • recombination (crossing-over)
  • independent assortment (of chromosomes)
  • fertilization (sexual reproduction)
26
Q

Selective Agent

A
  • is a component of the natural environment that consistently causes differential survival/ or reproduction
  • biotic (predators, disease, competitors) and abiotic (temperature, rainfall, etc)
27
Q

Selection Pressure

A

-the intensity in which the selective agents acts on a population to evolve

28
Q

What is the result of a large amount of selective pressure?

A

-more rapid changes in the population

29
Q

What is the result of a lower amount of selective pressure?

A

-variants will be more stable and populations will look largely similar

30
Q

What are the four types of data that document the pattern of evolution?

A
  • the fossil record
  • homology
  • direct observations
  • biogeography
31
Q

How does the fossil record provide us with evidence of evolution?

A
  • dating of sedimentary rock layers allow fossils to be placed in time (oldest at the bottom, newer on top)
  • the same aged stratum will have consistent forms of organisms
  • intermediate forms can be identified that appear to be ancestors of current species (derived forms)
  • extinction can be seen in the fossil record
32
Q

How does homology provide us with evidence of evolution?

A

-common structures is evidence that species evolved from a common ancestor

33
Q

What are vestigial structures?

A
  • are ones that don’t have perceived functionality, they are retained from a previous ancestor
    eg: appendix, wisdom teeth, human tails
34
Q

How does molecular structure provide evidence of evolution?

A
  • the fact that every organism has the same universal genetic code (DNA to amino acids to protein) provides evidence of evolution because we all share the same code
  • the different nucleotide sequences that account for variation and different traits explain descent with modification
35
Q

Explain how direct observations provide us with evidence of evolution

A
  • can see it happen through artificial selection (breeding things for desirable phenotypes) eg: veggies like broccoli and cabbage were artificially modified from wild mustard or breeding dogs
  • antibiotic resistance-the resistant phenotype becomes the most common because the weak bateria get killed off so only the strong will reproduce
  • pesticide resistance in insects and pests
36
Q

Explain how biogeography provides us with evidence of evolution

A
  • regions with identical climates have different species, but they show similar forms and functions
  • geographic barriers result in differences in taxonomic groups eg: Ethiopia being divided by the Sahara desert resulting in separate traits in species there
  • in the same region, organisms are usually closely related even across environmental gradients

BIOL 108 (5 decks)

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