Lecture 3, 4, & part of 5

Question 1

Neutral evolution

Answer 1

non-adaptive evolution, no fitness changes. therefore, selection cannot act on it.

Question 2

Why does neutrality arise?

Answer 2

1. Many genotypes may produce the same phenotype
2. Many phenotypes may have essentially the same fitness

Question 3

why do many genotypes produce the same phenotype?

Answer 3

because genetic code is redundant, some DNA is not expressed, some amino acid substitutions produce no change in the shape or charge of a protein, and development is canalized.

Question 4

why do many phenotypes have essentially the same fitness?

Answer 4

that particular trait variation makes very little difference to reproductive success and the impact on fitness of a chain in one trait compensates for that of a change in another trait (trade-off).
end result is the same

Question 5

Pseudogenes are

Answer 5

genes that are no longer expressed
will not affect phenotype

Question 6

how do pseudogenes arise?

Answer 6

a gene duplicates then that duplicate gets a loss of function mutation

Question 7

Canalization

Answer 7

the limitation of phenotypic variation by developmental mechanisms
production of the same phenotype regardless of variability of environment or genotype

Question 8

some traits canalized in tetrapod’s (4 limbs, 2 eyes, etc.). genetic variation affects many things about those traits but not their ___

Answer 8

number

Question 9

Genetic drift

Answer 9

is the random, aimless wandering of frequencies of neutral genes (gene frequency)
it fixes neutral alleles faster in smaller populations but occurs in populations of all sizes

Question 10

What are the effects caused by small population sizes?

Answer 10

founder effect and genetic bottleneck

Question 11

founder effect

Answer 11

a few individuals found a new population, bringing with them only a small portion of the genetic variation of the original stock

Question 12

genetic bottleneck

Answer 12

a population crashes to very small size; only a few alleles make it through b/c there are only a few individuals left alive to carry them

Question 13

An adaptation is a trait that

Answer 13

increases fitness

Question 14

any hypothesis of adaptation needs to be ____

Answer 14

tested against alternatives

Question 15

what are the 3 criteria talked about in class of adaptation?

Answer 15

1. natural selection itself
2. the perturbation criterion
3. the functional criterion

Question 16

The perturbation criterion

Answer 16

requires both a predictive model and an experiment
an adaptation is the state of a trait predicted by a model that is tested by using some method to perturb the phenotype from the optimal state and to demonstrate that the fitness of the perturbed phenotypes is lower than the fitness of the predicted one

Question 17

what is an example of perturbation criterion?

Answer 17

clutch size example
-manipulate clutch size and measure reproductive output
-want max. amount of babies without adding too much stress to parent

Question 18

the functional criterion

Answer 18

define adaptation as an appropriate plastic response (developmental plasticity)
an adaptation is a change in a phenotype that occurs in response to a specific environmental signal and has a clear functional relationship to that signal that results in an improvement in growth, survival, or reproduction

Question 19

what is an example of the functional criterion?

Answer 19

daphnia; spines/helmets produced when predators in area and not produced when no predators
humans; inutero mom can expose baby to cortisol which changes metabolism and also genetic tags for how certain genes are expressed

Question 20

what are the 5 questions of adaptation?

Answer 20

1. have experiments been done to support the claimed function?
2. has the performance of the trait with regard to a function been compared with alternative states of the trait?
3. do phylogenetic analyses suggest that the adaptation is repeatedly associated with the kind of natural selection needed to produce the adaptation?
4. could the trait have been selected to this state as a byproduct of selection on other traits?
5. is it a spandrel?

Question 21

what does spandrel mean?

Answer 21

ascribing a physical function to a form that exists for a different biological function

Question 22

what are the three main types of thought in evolutionary biology?

Answer 22

1. typological thinking
2. population thinking
3. tree thinking

Question 23

typological thinking

Answer 23

the most important thing to know about something is the category that it represents: the “normal” condition
derives from Plato’s theory of ideals and Aristotle’s theory of types

Question 24

When/why is typological thinking useful?

Answer 24

whenever the average properties of a thing are much more important than its variation
is a powerful simplification that makes life easier
**it will mislead you when thinking about evolution

Question 25

population thinking

Answer 25

the most important thing to know about something is the variation in the population from which it is drawn
tied to Darwin’s insight into the central role of variation in natural selection
view emphasizes variation in the population and the processes that change it, with individual samples whose traits can be estimated from population frequencies

Question 26

When/why is population thinking useful?

Answer 26

whenever it is important to know whether, and how fast, something will evolve
conceptualizes frequency distributions, patterns of variation in space and time, and probabilities
*antibiotic resistance & gut microbiome example

Question 27

Tree thinking

Answer 27

the most important thing to know about something is its position in a phylogenetic tree
derives from the insight that all species are related in a single tree of life
HIV & criminal case example
Used for flu shots!

Question 28

When/why is tree thinking useful?

Answer 28

whenever there is insight to be drawn from comparisons among species
knowing where on the tree of life a condition is present or absent gives clues to its correlations and possible causes
*know the lice example