topic 9 modes of natural selection

Question 1

directional selection?

Answer 1

• Favoring one extreme over the other
• Ex body size of european black bear btwn glacial and inter glacial period - ie bigger could survive cold better
Ex 2 . Evolution in horses - •
• Bigger could outrun predators better

Question 2

darwins finches ex - read it

Answer 2

ok

Question 3

•

Stabilizing selection

Answer 3

Favouring intermediate 
phenotypes over both 
extremes 
Birth weights of human 
babies (3-4 kg) (Fig. 6.8A) 
Clutch sizes in birds

Question 4

diversifying selection?

Answer 4

Disruptive (Diversifying) 
selection 
t.' Favouring both extremes 
over intermediate 
phenotypes 
E Black-bellied seedcracker 
finches of Cameroon

Question 5

• Fitness?

Answer 5

• Average lifetime contribution of individuals of a particular genotype to the population after one or more generations
  
  • Includes not only the number of offspring born but also the number that survive
  • fitness= Reproductive SUCCeSS

Question 6

• Fitness in asexual species

?

Answer 6

•

• Parthenogenetic populations; non-overlapping generations 
	○ Weevils & other insects 
• Fitness of an asexual species is pop growth rate - higher R = more fit

Question 7

fitness of a genotype?

Answer 7

• Fitness of a genotype = proportion surviving X average fecundity
• This is also population growth
rate (R)

Question 8

absolute fitness?

Answer 8

Per capita growth rate of each
genotype is that genotype’s
absolute fitness

Question 9

relative fitness?

Answer 9

Relative fitness of a genotype is 
its value of R to that of some 
reference genotype 
Refererx:e genotype with 
highes R

Question 10

mean fitness?

Answer 10

Mean fitness = average fitness of
individuals relative to fittest
genotype

Question 11

absolute fitness in sexual species?

Answer 11

• Absolute fitness: Number of zygotes (offspring) produced over a lifetime
  
  • Absolute fitness (W) = (probability that the individual survives to maturity) X (expected number of offspring if the individual does survive)

Question 12

genotype and allele freq in seuxal species?

Answer 12

• Genotype frequencies depend on allele frequencies among uniting gametes
Allele frequencies affected by several components of selection

Question 13

• Components of selection in sexual species (4)

Answer 13

*

* Viability, mating success, fecundity, fertilization success

Question 14

viability?

Answer 14

Viability: Probability of 
survival through 
reproductive age; 
does not affect fitness 
after last age of last 
reproduction

Question 15

fecundity?

Answer 15

2. 
Fecundity: Average 
number of viable 
offspring per female; 
fertility of mating may 
depend on maternal 
genotype or genotypes 
of both partners

Question 16

fertilization success?

Answer 16

Fertilization success: An allele may affect gamete’s

ability to fertilize an ovum

Question 17

read pepper moths ex

Answer 17

ok