18 - Populations and Evolution

Question 1

gene pool

Answer 1

all the alleles of all the genes of all the individuals in a population at a given time

Question 2

allelic frequency

Answer 2

number of times an allele occurs within the gene pool

Question 3

use of Hardy-Weinberg principle

Answer 3

used to predict the proportion of dominant and recessive alleles of any gene in the population, provided the population remains the same from one generation to the next

Question 4

conditions required for Hardy-Weinberg

Answer 4

no gene mutations
no immigration
no emigration
large population
random mating between individuals
all genotypes have the same reproductive success

Question 5

effect of population size on the impact genetic drift on a population’s genetic diversity and evolution

Answer 5

greater population size, smaller impact of genetic drift on a population’s genetic diversity

Question 6

genetic variation arises as a result of

Answer 6

mutation
meiosis
random fertilisation of gametes

Question 7

selection pressures that limit the population of a species

Answer 7

predation, disease, competition, food, light, space

Question 8

evolution by natural selection depends on

Answer 8

1. over production of offspring
2. genetic variation within populations of all species
3. phenotypic variation

Question 9

over production of offspring

Answer 9

death rates must be high as populations rarely increase exponentially
some species have lower reproductive rates but increased parental care in order to maintain population
intraspecific competition for aailable resources
death isn’t random

Question 10

disruptive selection

Answer 10

selection pressure towards the extreme values creates two modal values

Question 11

stabilising selection

Answer 11

selection pressure towards the central value increases the number of individuals at the modal value

Question 12

directional selection

Answer 12

selection pressure towards one xtreme value moves the mode in this direction

Question 13

speciation

Answer 13

the evolution of new sppecies fro existing ones, often caused by geographical isolation and different selection pressures acting over many generations

Question 14

allopatric speciation

Answer 14

speciation caused by geographical separation

1. environmental conditions on either side of the geographical barrier vary
2. natural selection influences the two populations differently
3. each evolves in different ways leading to adaptations to their local conditions

Question 15

sympatric speciation

Answer 15

speciation caused by reproductive separation within the same population

1. different individuals of the same species start utilising a new resource or area
2. mate with other individuals in this area
3. over time mutations arise which lead to genetic differences
4. results in unsuccessful breeding between the different groups of individuals