Evolution

Question 1

Both Darwin and Wallace observed:

Answer 1

Pattern: organisms only live in environments to which they are well-adapted
Hypothesized process: environmental factors prevent any organism that is NOT well-adapted from successfully reproducing (natural selection)

Question 2

Darwin’s Theory of Evolution

Answer 2

• Variation exists among individuals within a pop
• Variation is heritable
• Variation affords different traits to individuals in a pop and competition exists among individuals
• Organisms whose variation best fits them to the environment are the ones most likely to survive, reproduce, and pass those desirable traits on the next gen
• Variation provides the raw material for natural selection to act on
• Natural selection: observable way for life to change

Question 3

Genetic Basis of Evolution

Answer 3

Traits are coded for by DNA which join together to form genes, which are linked to form chromosomes

Question 4

Sexual reproduction

Answer 4

• Offspring inherit genetic material from their parents
• Results in constant recombination of genetic material within a pop
• New combos in every gen
• Mutations

Question 5

Asexual Reproduction

Answer 5

Mutations

Question 6

Mutations

Answer 6

• Random and occur within DNA
• Mutations arise and if favoured by natural selection, can spread through the pop
• Can help provide genetic variation within a pop, resulting in evolution over time
• Small changes are key cuz big ones = death

Question 7

Natural Selection

Answer 7

Struggle to survive and the natural variability that exists among individuals results in some individuals being more likely to produce offspring. Therefore, those traits get passed on.

Question 8

Survival of the Fittest

Answer 8

• Fitness = probability of successful reproduction
• Ability to survive
• Find a mate
• Produce viable offspring
• Heritable traits that increase an organism’s fitness are more likely to be passed on to subsequent gens
• Traits that aid survival and reproduction become more frequent in the population than disadvantageous traits

Question 9

Traits selected for are dependent on:

Answer 9

the environment the organism is living in. IF the environment changes, then the traits that are beneficial also change

Question 10

Natural selection cannot supply what an organism needs, it just acts on:

Answer 10

the individual; it survives to reproduce or it doesn’t

Question 11

Natural selection is the engine

Answer 11

of evolution

Question 12

Evolution is neither:

Answer 12

progressive nor ‘goal-orientated’

Question 13

Evolution is

Answer 13

a change in gene frequency within a pop from gen to gen

Question 14

Does the process of evolution ever stop?

Answer 14

No.

• The environment applies constant selective pressure to pops.
• Even during intervals of apparent stasis, pops still changes genetic composition via recombination (sexual reproduction, mutation, and natural selection)

Question 15

Importance of large pop size to evolution

Answer 15

• Larger pops have more ‘genetic inertia’
• New traits take longer to express themselves
• More variability (genetic potential) with which to respond to selective pressure.

Question 16

Small pop size and evolution

Answer 16

• Small pops can evolve rapidly
• Traits the increase fitness can be spread throughout the pop more readily
• Less variability
• Vulnerable to rapid extinction

Question 17

Convergent Evolution

Answer 17

• The wings of a bird and a bat are bit homologous because they cannot be traced back to a common ancestor. These are analogous structures.
• The limbs of a bird, a bat, and even a pterosaur are homologous, the use of those limbs as wings is not. Wings evolved independently (and differently) in each of these groups from a non-flying ancestor.

Question 18

Biological Evolution: descent with modifications

Answer 18

• Small scale: changes in gene frequency in a pop from one gen to the next
• Large scale: descent of different species from a common ancestor over many generations
• Common ancestor on Earth gave rise to diversity in fossil record and today

Question 19

How do we define species?

Answer 19

Biological species concept: members of a pop who can breed and produce viable offspring, can be observed in nature

Question 20

How do we differentiate species in the fossil record?

Answer 20

Morphological species concept: species distinguished on basis of physical (morphological) differences, for example differences in shapes of bones

Question 21

Observing Evolution in the fossil record

Answer 21

1. Gradual lineage evolution (see every step)
2. Quick lineage evolution (rapid don’t see all the steps just “result”)
   - The observed fossil record seems to show rapid evolution but this pattern can also be explained by irregular preservation of transitional forms

Question 22

How do we track biodiversity in the fossil record?

Answer 22

Sum total of different taxa: affected by rates of origination and extinction

Question 23

Origination rate

Answer 23

• Rate at which new taxa evolve/are found in the fossil record
• Can increase rapidly when new niches are invaded

Question 24

Extinction rate

Answer 24

• The rate at which taxa go extinct through geologic time
• The end of a genetic lineage
• 99% of all species are now extinct
• Most species disappear in “background extinctions”

Question 25

Mass extinctions

Answer 25

• When the extinction rate increases and overwhelms the origination rate, mass extinctions occur
• Significant decrease in global biodiversity
• Five generally recognized mass extinctions: End Ordovician, End Devonian, Permo-Triassic (~95% extinction of all species on Earth), End Triassic, Cretaceous-Paleogene