evolution - topic 5

Question 1

define evolution

Answer 1

changes in the heritable characteristics of organisms over generations

Question 2

why might allel frequency change over time?

Answer 2

random mutations

Question 3

describe the stage sof natural selection

Answer 3

• variation occurs between idividuals in a population
• due to mutations and diffeences from meiosis
• selection pressure introduced
• individuals with advantagous alleles survive
• reproduce passing allele onto offspring
• allele frequency changes

Question 4

what must happen for speciation to occur?

Answer 4

individuals become isolated

Question 5

what are the two types of speciation ?

Answer 5

allopatric
sympatric

Question 6

why does speciaton occur when individuals are islolated?

Answer 6

no gene flow
(no exchange in genes betwen groups)

Question 7

what is allopatric speciation ?

Answer 7

geographical isolation

Question 8

what is sympatric isolation?

Answer 8

random mutations prevent interbreeding between individuals

Question 9

describe what happens in allopatric speciation

Answer 9

• populations of a species become separated from each other by geographical barriers (e.g a river)
• no gene flow can occur between seperated populations
• Different selection pressures acting on them + genetic drift cause changes in allele frequencies
• change so much that they can no longer successfully interbreed and are different species.

Question 10

describe what happens in sympatric speciation

Answer 10

• random mutation occurs causing a changes allele and therefore phenotype of an individual
• preventing them from successfully breeding with other individuals in the population
• this could be a seasonal, behavioural or mechanical change
• isolated in the sense that they do not interbreed
• lack of gene flow
• allele frequencies in the gene pools change

Question 11

5 basic principles of natural selection

Answer 11

1. variaton present
2. selection pressures act on population
3. advantageous allel = increased survival
4. alleles passsed on
5. allele frequencies change

Question 12

give 3 xamples of evidence for evolution

Answer 12

• fossils
• observation of antibiotic resistance
• molecular evidence
• gene sequencing

Question 13

explain how theories are validated by the scientific community

Answer 13

• publishing in scientific journals
• peer reviews
• scientific conferences
• ensuring correct stats tests have been produced

Question 14

explain the method of gene sequencing in providing evidence for evolution

Answer 14

• determine sequence of bases that makes up a gene
• compare base sequences with other individuals
• if sequences similar this indicated common ancestory
• level of similarity indicate how long ago the two species diverged