Inheritence/ variation 3

Question 1

How do gene mutations cause variation

Answer 1

-the dna base sequence is altered which then results in a new polypeptide

Question 2

How does crossing over result in variation?

Answer 2

• The chromosomes cross over where the alleles are crossed and new combinations of alleles are formed

Question 3

How does independent segregation cause variation?

Answer 3

• during meiosis II
  -the fist separation of homologous chromosomes happens separately from the separation of the other pair , resulting in random allele combinations

Question 4

How does random fertilisation cause variation?

Answer 4

-ocurrs during sexual reproduction,

Question 5

What are characteristic influenced by genetic factors

Answer 5

-controlled by one or two genes
-expressed as phenotypes
-represented as distinct groups on a bar chart.

Question 6

What are characteristic by environmental factors

Answer 6

• controlled by many genees
  -have no separate categories
  -normal distribution curve

Question 7

What are the 3 selection pressures in natural selection

Answer 7

predation
disease
competition

Question 8

What is stabilising selection

Answer 8

-when the environment isn’t changing
-the average in the graph is the one passing the genes as they’re not advantageous for a specific allele.

Question 9

What’s directional selection?

Answer 9

-when the environment is changing
-the change in environment selects for those organisms with allies for a phenotype towards an extreme range

Question 10

What’s disruptive selection

Answer 10

-opposite of stabling selection
-involves selection of phenotype from extreme
-most important bringing about evolutionary change
-the average isn’t advantaous

Question 11

When does evolution occur

Answer 11

When there’s a change in allele frequencies in a population

Question 12

What’s speciation

Answer 12

• evolution of new species from existing ones

Question 13

What can reproductive isolation of 2 populations cause in a gene pool?

Answer 13

• decreased variation
  -accumilation of difference

Question 14

How do new species arise from reproductive isolation

Answer 14

• allopatric speciation
  -they arrive from existing species

Question 15

describe allopatric speciation

Answer 15

-population already has variation due to meiosis, mutations and graphological differences
-populatons are isolated meaning there’s no gene flow
-different selection pressures for different phenotypes
-frequency of selected phenotypes
-

Question 16

why might allelic frequencies change. ( number of alleles for specific gene )

Answer 16

-mutations may occur independently in each population

Question 17

explain sympatric speciation

Answer 17

-not isolated due to geographical barrier
-isolated due to random mutations of an organism than rest of the population .Meaning they cant breed with the rest of the population

Question 18

what speciation is sympatric

Answer 18

-distruptive speciation