TERMS FOR TEST 3

Question 1

adaptation

Answer 1

an inherited trait that makes an organism more fit in it;s abiotic (non-living) and biotic (living) environment, and that has risen as a result of the direct action of natural selection for its primary function.

Question 2

antagonistic pleiotropy

Answer 2

A hypothosis that proposes that the genes that code for beneficial effects also codes for deleterious effects in other contexts

Question 3

coevolution

Answer 3

When evolutionary change in one species can affect selective conditions for a second species.

Question 4

differential reproductive success

Answer 4

One of the three conditions of natural selection. Individuals with certain traits are more successful than others at surviving and reproducing in their environment.

Question 5

exaptation

Answer 5

A trait that serves one purpose today but evolved under different conditions and served a different condition in the past.

Question 6

gene duplication

Answer 6

an extra copy of a working gene is formed. Once an organism has two copies of one gene, one of the gene copies might change to a new function, while the other can remain unchanged and thus perserve the original function.

Question 7

gene sharing

Answer 7

a protein that serves one function in one part of the body is recruited to perform a new and different function in a second location.

Question 8

inheritance

Answer 8

One of the three conditions of natural selection. Some differences in poulations are inherited by offspring from their parents.

Question 9

life history strategy

Answer 9

the schedule and manner of investment in survivorship and reproduction of an individual in a lifetime.

Question 10

marker gene

Answer 10

a gene used in nuclear biology to determine if a nucleic acid sequence has been successfully inserted into an organism’s DNA.

Question 11

norm of reaction

Answer 11

Genes produce a trait that that may differ according to the context of a set of environmental conditions.

Question 12

pleiotropic genes

Answer 12

when genes affect more than one characteristic.

Question 13

trade-off

Answer 13

EX: :Larger offspring may survive with higher probabilities but because such offspring require more resources during thier in utero development than do smaller offspring, fewer larger offspring will be produced.

Question 14

variation

Answer 14

One of the three conditions of natural selection. Individuals in a population differ from one another,

Question 15

selection coefficient

Answer 15

to quantify the strength of natural selection, a parameter called the selection coefficitent is used, labeled s to describe the fitness reduction of one type.

Question 16

frequency-independent selection

Answer 16

fitness associated with a trait is not directly dependent on the frequency of the trait in a population.

Question 17

directional selection

Answer 17

one allele is constantly favored against the other allele. IE selection drives allele frequencies in a single direction toward an increasing frequency of the favored allele.

Question 18

Fixation

Answer 18

when an allele becomes fixed (impossible according to the hardy-Weinberg model for an infinite population size.

Question 19

Over dominance

Answer 19

also known as heterozygote advantage, check page 221 for more info

Question 20

Frequency-dependent selection

Answer 20

when the costs and benefits associated with a trait depend on its frequency in the population. Can be positive or negative, positive means the fitness associated with a trait increases as the frequency of the trait increases in the populations. With negative, the fitness associated with a trait decreases as the frequency of the trait increases in the population. under negative frequency-dependent selection, each phenotype is favored when it is rare.

Question 21

Fecundity

Answer 21

the number of offspring produced

Question 22

Wright-Fisher model

Answer 22

a way to think about small populations in a quantitive way. Basically a small version of the Hardy-Weinberg model. Check page 246

Question 23

Genetic drift

Answer 23

the process of random fluctuation in allele frequencies due to sampling effects of finite populations.

Question 24

The Three consequences of genetic drift

Answer 24

In a finite population, allele frequencies fluctuate over time, even in the absence of natural selection.

Some alleles are fixed, others are lost, and th fraction of heterozygotes int he population decreases over time

Separate populations diverge in their allele frequencies and in terms of which alleles are present.

Question 25

selectively neutral

Answer 25

no difference in fitness between alleles

Question 26

observed heterozygosity

Answer 26

used to measure the amount of variation in a population. A fraction of the individuals in the population that are heterozygous at the given location.

Question 27

expected heterozygosity

Answer 27

the fraction of heterosygotes expected under the Hardy Weinberg model, given the allele frequencies of the population.

Question 28

population bottleneck

Answer 28

When populations become very small, even for a short time, allele frequencies change dramatically. The sampling that occurs during the reduction of population size and because of the accelerated pace of genetic drift in a small population.

Question 29

Founder Effect

Answer 29

the change in allele frequencies that result from sampling effects that occur when a small number of individuals from a large population initially colonize a new area and found a new population. Genes of founders usually only represent a subset of the genes present in the mainland population and so te allele frequencies ofin the founders may deviate by chance from those in the large population. Extremely rare alleles that are extremely rare may become common.

Question 30

Substitutions

Answer 30

when a new allele arises by mutation and is subsequently fixed in the population. The substitution rate is defined as the rate at which new 3alleles become fixed int he population.

Question 31

Neutral theory

Answer 31

proposed that at a molecular level of DNA sequence:

1 Most of the variation present within a population is selectively neutral.

2 most of the changes in dna or amnio acid sequence over time - and thus many of the molecular differences between related species - are selectively neutral.

3 Most of the genetic variation within a population is neutral and thus not subject to natural selection.

Question 32

Pseudogenes

Answer 32

non-functional and typically untranslated segments of DNA that arise from previously functional genes.

Particularly very informative about evolutionary history as they are derived fro, homologous genes and subject to neutral drift.

Question 33

Molecular clock

Answer 33

The fact that substitutions occur in the population at the same rate that neutral mutations arise in an individual.
Substitution rates at different loci do not depend of population size or other demographic parameters, neutral mutations arise at similar rates in different taxa and should also be fixed at similar rates.

Question 34

Nearly neutral theory

Answer 34

posits that most substitutions are, if not exactly neutral, only mildly deleterious. Therefor population size plays a critical role in determining the balance between drift and selection.

Question 35

Heterozygosity in Genetic Drift

Answer 35

When an allele heads towards fixation, less alleles are available to make heterozygous pairs

Question 36

Name the three different types of selection and how they work

Answer 36

Directional

Heading towards one homozygous pair

Stabilizing

Heading towards one heterozygous pair

Diversifying

Disruptive selection separating from heterozygous pair to separate homozygous pairs

Examples:

Longest tail length has highest fitness, directional

Average tail length has highest fitness stabilizing

CHANGES TO ENVIRONMENT
usually induces directive selection followed by stabilizing

Question 37

Positive dependent selection

Answer 37

More rare greater the fitness

IE left or right mouthed fish example.

Question 38

Negative frequency selection

Answer 38

More common greater the fitness

IE butterfly example

Question 39

Genetic Drift

Answer 39

Not due to natural selection, due to sampling error. Can affect allele frequencies that are affected by natural selection. Genetic drift does not result in adaptation. Only natura selection does.

Question 40

Absolute fitness equation

Answer 40

better fitness over worse fitness