Population and evolution

Question 1

What is a gene pool?

Answer 1

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

Question 2

allelic frequency

Answer 2

The number of times an allele occurs within the gene pool

Question 3

Five assumptions of Hardy Weinberg

Answer 3

• no mutations arise
• the population is isolated, that is, there is no flow of alleles into or out of the population
• no selection, that is, that alleles are equally likely to be passed to the next generation
• the population is large
• mating within the population is random

Question 4

Hardy Weinberg equation

Answer 4

p(squared)+ 2pq+q(squared)
- in p+q – p= probability of allele A
q= probability of allele a

Question 5

variation due to genetic factors

Answer 5

Genetic vatiation arises as a result of:
- mutations: sudden changes to genes and chromosomes may or may not be passed on to the next generation.
mutations are a main source of variation
- meiosis: this form of nuclear division produces a new combination of alleles before they are passed to the gametes
- random fertilisation of gametes: in sexual reproduction this produced new combinations of alleles and the offspring are different from parents. Which gamete fuses with which at fertilisation is a random process further adding to the variety of offspring two parents can produce

Question 6

Variation due largely to environmental influences

Answer 6

• environmental exerts influence the way the organisms genes are expressed
• for example buttercups: one plant may be determined by its genes to grow much taller than other plants .
• if however, the seed germinated in an environment of poor light or low soil nitrate, the plant might not grow properly and it will
• environmental influences include soil conditions, pH and food avaliability

Question 7

selection pressures:

Answer 7

The environmental factors that limit the population of species are called selection pressures. These selection pressures include predation, disease and competition

Question 8

the process of evolution by means of natural selection depends upon a number of factors such as

Answer 8

• organisms produce more offspring that can be supported by the available supply of food, light, space etc
• there is genetic variety within the populations of all species
• a variety of phenotypes that selection operates against