natural selection pack 9

Question 1

natural selection

Answer 1

is the mechanism by which organisms change over time as they adapt to their changing environments

Question 2

struggle for existence

Answer 2

when a population increases in size a lot of individuals will die or fail to reproduce due to completion for food and recourses. disease and extreme environmental conditions may also cause the deaths

Question 3

evolution

Answer 3

a change in allele frequency in a population over time (generations)

Question 4

for natural selection to lead to evolution there must be

Answer 4

some genetic variation in the population

Question 5

describe stabilising selection

Answer 5

if the environment remains stable, then organisms may simply become better and better adapted to their existing niches- if the environment changes then selection changes too

Question 6

the ability of a population to adapt to new conditions will depend on

Answer 6

strength of the selection pressure, size of the gene pool, reproduction rate of the organism

Question 7

a gene pool consists of

Answer 7

all the alleles of all the genes present in a population of a species at a given time

Question 8

populations with a bigger gene pool have

Answer 8

more different alleles of each gene and are said to have greater genetic diversity

Question 9

evolution

Answer 9

a change in allele frequency in a population over time (generations)

Question 10

allele frequency

Answer 10

the relative frequency with which an allele is found in a population

Question 11

selection pressure

Answer 11

a change in the environment that can affect the organism ability to survive in a given environment

Question 12

struggle for existence

Answer 12

competition between members of a species for resources for survival and reproduction

Question 13

process of natural selection

Answer 13

there is genetic variation in population- often due to a random mutation. a change in the environment provides a selection pressure. some individuals possess an advantageous characteristic in the changed environment. there is competition for survival. individuals with the advantageous allele have a selective advantage so are more likely to survive to adulthood and breed, passing on the advantageous allele to their offspring. the advantageous allele frequency in the population increases- a change in allele frequency over generations indicates evolution. this can allow a species to become better adapted to the environment.