Populations and Evolution-BP

Question 1

What is Evolution?

Answer 1

change in allele frequency in a population

Question 2

What are the 2 Types of Evolution?

Answer 2

Adaptation and Speciation

Question 3

What is Adaptation?

Answer 3

• a species adapting to changes in the environment (e.g. new diseases or change in climate)
• driven by natural selection
• most of the individuals in the species will have the favourable allele/characteristic for that environment

Question 4

Process of Adaptation?

Answer 4

 variation in population of species
(genetic diversity/genetic variation/variety in gene pool)
 new alleles arise by random mutation
 environment applies a selection pressure on the population
 those with favourable characteristics/alleles survive, the others die [natural selection]
 the ones that survive will reproduce, passing on their favourable alleles = reproductive success
 if this happens for many generations, then that characteristic will become most common – the favourable alleles will become more frequent [adaptation]

Question 5

What are the 3 types of selection?

Answer 5

stabilising and directional and disruptive

Question 6

What is stabilising selection?

Answer 6

 when the environment favours those with the most common characteristic – those on the extreme dies out
 the common characteristic increases in proportion
 the range (standard deviation) will reduce

Question 7

What is directional selection?

Answer 7

 when the environment favours those individuals with characteristics on one of the extremes
 over time this will become the most common characteristic
 normal distribution will shift to that extreme

Question 8

What is disruptive selection?

Answer 8

 when the environment changes between both extreme conditions
 hence, individuals on both extremes are favoured at different times and increase in number
 those in the middle (average) will decrease in number

Question 9

What is Speciation?

Answer 9

process by which new species arise from existing species

Question 10

What are the 2 Types of Speciation?

Answer 10

• Allopatric
• Sympatric

Question 11

What is Alloptaric Speciation?

Answer 11

speciation driven by geographical isolation

Question 12

Describe Allopatic Speciation

Answer 12

 start with a population of species
 variation in the population
 population separated into different groups by geographical isolation
 each group is exposed to different environments/selection pressures
 each group undergoes different directional selections
 therefore each group changes so much in genetic diversity (variety of alleles) that they can no longer interbreed with each other to produce fertile offspring = different species
 changes include different courtship behaviour or incompatible gametes

Question 13

What is Sympatric Speciaition?

Answer 13

speciation occuring in the same geographical area (driven by random mutation)

Question 14

What does Hardy-Weinberg Principle calculate?

Answer 14

frequency of an allele in a population

Question 15

What does the Hardy-Weinberg Principle assume?

Answer 15

that the frequency will not change over time, based on:

 isolated population
 large population
 random mating
 no mutation
 no selection

Question 16

What is the Hardy-Weinberg Principle?

Answer 16

 p = frequency of dominant allele
 q = frequency of recessive allele
 p + q = 1 (100%, all the population)
 p2 = frequency of homozygous dominant
 2pq = frequency of heterozygous
 p2 + 2pq = frequency of the dominant condition
 q2 = frequency of homozygous recessive (of recessive condition)
 p2 + 2pq + q2 = 1

Question 17

what is selection?

Answer 17

the process that results in the best adapted individuals in a population surviving to breed and pass on their advantageous alleles

Question 18

Adaptive radiation?

Answer 18

if two populations are no longer isolated they can’t reproduce as they are two separate species