Chapter 24 & 25

Question 1

Evolution occurs because ..

Answer 1

traits vary among the individuals of a population and because individuals with certain traits produce more offspring than others
The main idea here is population

Question 2

Population thinking

Answer 2

Focusing on the variation of individuals in a population
Not dismissing the genetic differences and looking at the whole

Question 3

“descent with modification”

Answer 3

Species change over time
Species are related by a common ancestor

Question 4

Extant

Answer 4

still alive

Question 5

Radiometric dating

Answer 5

determine when and how long they have been decomposing

Determine age of bones by carbon dating

Question 6

Evidence

Answer 6

Fossil record vs Extant species
Geological time scale
Radiometric dating with parent and daughter particles

Extinctions
Transitional features
Homology
Vestigial traits

Question 7

Four postulates

Answer 7

Variation
Variation is heritable
Mortality due to differences in fitness
Survivors are not random

This leads to a new way of defining evolution as the “change in allele frequency in a population over time”

Question 8

Misconceptions about Natural selection and adaptation

Answer 8

• Selection is on individuals, but evolution is on population
  
  • During the process individuals do not change
  • The pressure on individuals and the difference in reproduction causes the population to change
  • The allele frequencies change, not the alleles themselves
• Acclimation is not adaptation
• Evolution is not goal directed
• Adaptations do not happen because the animals wanted or needed them
• Adaptation happened because they increased reproductive capabilities
• Evolution is not progressive
  
  • Being more Highly evolved does not make you better
  • Evolution can cause the loss in really complex traits
• No organism is higher or lower
  
  • We are not a higher being
  • We are adapted to our environment like every other organism
• Organisms do not act for the good of the species, but the good of the organism
  
  • Reproduction
  • Self sacrificing alleles vs. selfish alleles

Question 9

Limitations of natural selection

Answer 9

• Non-adaptive traits
  
  • Vestigial traits
  • Silent mutations
• Genetic constraints
  
  • Genetic correlation
  • Variation
  • Fitness tradeoffs: compromise of a variety of traits
  • Historical constraints

Question 10

Population

Answer 10

group of individuals in the same species and location that can breed

Question 11

Evolution Mechanisms

Answer 11

natural selection

genetic drift

gene flow

mutation

Question 12

natural selection

Answer 12

increases the frequency of certain alleles

Question 13

Genetic drift

Answer 13

causes alleles to change randomly

Change in allele frequencies that is due to chance
Blind luck
A couple on an island with the genes AtAh and AtAh
They have five children
50:50 chance of each gene

Random
More pronounced in small populations
Can lead to the loss or fixation of alleles

Question 14

Gene flow

Answer 14

individual movement causes a change in allele frequency

Typically causes equalization between the two populations

Question 15

Mutation

Answer 15

produces new alleles

Most other mechanisms lead to loss of genetic diversity
Mutations do not
May not increase fitness
May be detrimental or beneficial or neutral

Not very significant for evolution
why?
Slow

Question 16

Hardy Wienberg principle

Answer 16

1908 G.H. Hardy and Wilhelm Weinberg
Believed that variation only occurred from reproduction

a population viewpoint for the allele frequency

Question 17

Gene pool

Answer 17

all of the gametes of a population

Exp: clams and sea urchins

Question 18

Hardy Wienberg principle

finding geneotype

Answer 18

Two alleles of one gene
A1 and A2
p= frequency of allele A1
q = frequency of A2

Since the frequency must =1

p + q = 1

Three genotypes are possible:
A1A1, A1A2, A2A2

Question 19

Hardy Wienberg principle

finding frequency

Answer 19

The frequency of:
A1A1 is p^2
A1A2 is 2pq
A2A2 is q^2

So the equation is p^2 + 2pq + q^2 = 1

Question 20

To calculate the respective allele frequencies

Answer 20

p= ½(2pq) + p^2

Question 21

Natural selection

3 types

Answer 21

Directional
Stabilizing
Disruptive

Question 22

Directional selection

Answer 22

Reduces genetic diversity
Purifying selection
Exp: freeze caused insect and bird die off
Fitness trade off for maneuverability

Question 23

Stabilizing selection

Answer 23

No change in the average value of the trait
Genetic variation is reduced

Question 24

Disruptive Selection

Answer 24

Black bellied seed crackers
Speciation
Could be a Heterozygote advantage
Balancing selection: no allele has an advantage

Question 25

Natural selection causes

Answer 25

Increases fitness
Leads to adaptation

Question 26

Nonrandom mating

Answer 26

Inbreeding
Sexual selection

Question 27

inbreeding

Answer 27

Between relatives

Increases homozygosity
No evolution
Inbreeding depression: decline in average fitness
Loss of function mutations
Many genes including fighting disease have a heterozygous advantage

Question 28

Sexual selection

1948 asymmetry of sex theory

Answer 28

sexual selection acts on males more than females
“eggs are expensive, sperm is cheap”

Question 29

Sexual selection

1948 asymmetry of sex theory

prediction

Answer 29

Females are choosy
Equal frequency of sexes
Any allele that increases male attractiveness should increase rapidly

Question 30

Females choose good alleles

Answer 30

Well fed
Good health

Paternal care - male care for young and resources

male- male competition

Question 31

Male- male competition

Answer 31

compete for the opportunity to mate with females

Typically involves a territory
Males that lose fight are relegated to other areas, being sneaker males or the rejected females

Question 32

sexual seletion can lead to

Answer 32

sexual dimorphism or differences between males and females

Question 33

Answer 33

http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/life4e_15-6-OSU.swf