Lecture 7: Populations: Natural selection & evolution

Question 1

Define population

Answer 1

A group of individuals of the same species living in the same location

Question 2

define species

Answer 2

A group of individuals that naturally interbreed with each other and produce fertile offspring

Question 3

define natural selection

Answer 3

-Differential survival and reproduction of individual organisms dictated by the interactions between phenotype and the environment
-leads to evolution in the next generation— the process that is unique to populations.
-primary non-random mechanism of evolution
-is an ecological process

Question 4

define evolution

Answer 4

Change in a population’s gene pool over time

Question 5

Three key steps in adaptive evolution by natural selection

Answer 5

1. Heritable variation
2. Differences in reproductive success among individuals
3. Heritable phenotype of more reproductively successful individuals is more prevalent in the following generation.

Question 6

Mutation

Answer 6

-Any change in the DNA that codes for a gene or the expression of a gene
-Some changes can cause fatal phenotypic changes, some are neutral or “silent”, some can result in beneficial changes - the raw material of adaptive evolution

Question 7

Pleiotropy

Answer 7

Single genetic change that results multiple phenotypic effects.

Question 8

Epistasis

Answer 8

Hierarchical control of the expression of one gene by another gene.

Question 9

Polygenic traits

Answer 9

Complex interactions among many genes, resulting in continuously varying phenotypic traits

Question 10

Epigenetic changes

Answer 10

Heritable phenotype changes that do not involve alterations in a DNA sequence

Question 11

3 major types of natural selection

Answer 11

1. Stabilizing selection.
2. Directional selection.
3. Disruptive selection

Question 12

Stabilizing selection

Answer 12

-When ecological interactions increase survival and fitness of the most common phenotype in the population
-parent population starts of broader then progeny population
-progeny population gets thinner with the mean phenotype being higher than the parent phenotype
-the phenotype on the ends of the parent distribution are lost in the next generation

Question 13

Directional selection

Answer 13

-When ecological interactions increase survival and fitness of a rare phenotype in the population
-all of the phenotypes on one end of the parental distribution are favored become the mean in the next generation
-individuals in the other end are doing poorly and in the next generation, they are entirely gone
-the environment changes, and it pushes the population to fit that particular environment

Question 14

Disruptive selection

Answer 14

-When ecological interactions increase survival and fitness of two or more rare phenotypes in the population.
-the two ends of the parent distribution become the mean in the progeny population, results in the parent population’s mean lowering

Question 15

When does selection act?

Answer 15

Environment can “select” (create differential survival) at any stage before and during reproduction.

Question 16

Evolution through random processes

Answer 16

1. genetic drift
2. bottleneck effect
3. founder effect

Question 17

define genetic drift

Answer 17

any random loss of genetic variation followed by reinforcement

Question 18

define the bottleneck effect

Answer 18

random loss of genetic variation due to severe reduction in population size

Question 19

define the founder effect

Answer 19

random subset of original genetic variation in small populations that occupy a new area.

Question 20

How do phenotype and genotype interact?

Answer 20

-Selection acts on the genotype via the phenotype.
-Genotype of an individual is fixed, BUT a phenotype might have the capacity to vary with environment in ways that are adaptive.

Question 21

Phenotypic plasticity

Answer 21

The capacity of an individual’s phenotype to respond developmentally to environmental change within its lifetime.

Question 22

Adaptive phenotypic plasticity

Answer 22

The capacity of an individual’s phenotype to respond developmentally to environmental change in a way that increases its survival and reproduction

Question 23

Reaction norms

Answer 23

-The observed relationship between individual phenotype and the environment
-the observable pattern of phenotypic plasticity within a population

Question 24

define acclimatization

Answer 24

-Dynamic phenotypic plasticity in response to repeated (especially seasonal) environmental shifts
-reversible

Question 25

define developmental phenotypic plasticity

Answer 25

-Permanent phenotypic plasticity that tracks persistent environmental characteristics during development
-irreversible
-shows up during juvenile development and stays through adulthood

Question 26

Reciprocal transplant experiments

Answer 26

-take 2 organisms that have adapted to their respective environments and swap them and observe the results
-help address why populations from different environments show different phenotypes

Question 27

results of Reciprocal transplant experiments - genetic factors

Answer 27

phenotypes in each population are insensitive to environmental change

Question 28

results of Reciprocal transplant experiments - environmental factors (phenotypic plasticity)

Answer 28

individuals in each environment has similar reaction norms

Question 29

results of Reciprocal transplant experiments - differenced responses to environment (both genetic and phenotype)

Answer 29

reaction norms in each population have evolved in response to different prevalent environments