7.3 - Evolution and speciation

Question 1

define niche

Answer 1

a species’ role within the environment

Question 2

what is intraspecific competition?

Answer 2

competition between individuals of the same species
only those which have alleles best suited environment survive and reproduce, passing on advantageous allele/s

Question 3

what is interspecific competition?

Answer 3

competition between individuals of different species

Question 4

what increases the chance that a species will survive in a changing habitat?

Answer 4

variation in genotypes and phenotypes

Question 5

describe the process of natural selection

Answer 5

• random mutation occurs to some individuals
• selection pressure changes
• those with advantageous allele/s survive and reproduce
• advantageous allele/s passed on to offspring
• over time, frequency of allele/s increases

Question 6

define evolution

Answer 6

a change in the allele frequencies in a population over time

Question 7

define selection

Answer 7

individuals better adapted to their environment are more likely to survive and reproduce, passing on advantageous alleles

Question 8

what is directional selection?

Answer 8

• occurs after environmental conditions change
• favours an extreme phenotype
  e.g antibiotic resistant bacteria

Question 9

what is stabilising selection?

Answer 9

• no prior change in environmental conditions
• favours average phenotype, selects against extreme phenotypes
• phenotypes of greater diversity are reduced
  e.g new born babies’ weights

Question 10

what is disruptive selection?

Answer 10

• both extremes of phenotype are favoured over average
• e.g some large mammals and small mammals can survive a long time without food (due to body fat, due to decreased need for food) but intermediate sized animals can’t

Question 11

define speciation

Answer 11

when new species arise after a population becomes separated and cannot interbreed

Question 12

what is allopatric speciation?

Answer 12

• caused by physical barrier
• groups become reproductively isolated
• gene flow reduced
• allele frequency changes due to N.S.
• two parts of population can no longer interbreed and become separate species
  e.g camel and llama

Question 13

what is sympatric speciation?

Answer 13

• new species evolve from single ancestor when inhabiting same geographic region
• e.g due to chromosomal error during cell division which leads to reproductive isolation; mutations which mean courtship behaviour not recognised