p2: evolution may lead to speciation

Question 1

state 2 factros which cause variation in phenotypes

Answer 1

genetics and evironment

Question 2

what factor influences discontinous variation

Answer 2

result from genetics only

Question 3

what is continuous variation and give an exmaple

Answer 3

continous data e.g. height or mass

Question 4

what factor influences continous variation

Answer 4

environment and genes

Question 5

explain how natural selection allows evolution of populations to occur

Answer 5

• due to amuttion some organsms have an advantageous allele for … which gives them a selecttive advantage in the presence of a selection pressure
• the orgaisms with the advantageous allele is more likely to survive and pass of the allele to be inherited by thier offspring
• over many generatiion the advaantageous allel frequency will increase
• name type of selection

Question 6

what is stabilising selection and explain why it occurs

Answer 6

• slection pressures at both ends of the distribution so the middle is favoured so eliminates the extremes.

Question 7

give an example of stabilising selection and show a graph

Answer 7

example = birth mass

Question 8

what is directional selection and sketch a graph to show

Answer 8

selection pressure that favours the extreme pheotype

Question 9

give an exmaple of directional selection and explain why it occurs

Answer 9

antibiotic resistance

Question 10

what is disruptive selection and sketch a graph

Answer 10

selection pressures favour both extemes

Question 11

what is disconntinous variation and give an example

Answer 11

discrete categories e.g. ABO blood types

Question 12

whatis a gene pool

Answer 12

all the alleles of all th genes in a population

Question 13

what is meant by speciation

Answer 13

the process through which new species aries

Question 14

desribe how allopatric speciation can lead to formation of new species

Answer 14

• populations of same species become geographically isolated
• they cannot interbreed so form seperate gene pools
• the different area have different selection pressures
• in each population mutations form nw alleles
• different alleles get passed onto offspring
• allele ffrequence changs over time
• when the barrier is removed, the populations cannot interbreed to produce fertile offspring

Question 15

describe how sypatric speciation can lead to the formation or a new species

Answer 15

• occurs wihtin the same area
• mutations form different alleles in the population
• populations become reproductivalyy isolated
• offspring inherit different alleles chnage the allele frequency over many generations
• causes disruptive selection
• populations cannot interbreed to produce fertile offspring

Question 16

describe how genetic drift occcurs and what sort of popultion it occurs in

Answer 16

• occurs in small populations
• by chnace one allele is inherited mre often so becomes more frequent