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 (resulting in new allele of a gene) occurs to some individuals
• selection pressure changes
• those with advantageous allele survive and reproduce
• advantageous allele passed on to offspring
• over time, frequency of allele increases in population

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

Question 14

What is the primary source of genetic variation?

Answer 14

mutation

Question 15

Why is genetic drift important only in small populations?

Answer 15

• smaller gene pool
• so any change in allele frequency has great effect