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AQA A-Level Biology > Chapter 18 - Population and Evolution > Flashcards

Chapter 18 - Population and Evolution Flashcards

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1
Q

What is the gene pool?

A

All the allele of all the genes of a population

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2
Q

What is allelic frequency?

A

The number of times an allele occurs within the gene pool

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3
Q

What will the allelic frequency always be?

A

Less than one

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4
Q

What does the Hardy-Weinberg principle predict?

A

The frequency of alleles will stay constant over generations providing there are no mutations

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5
Q

What are the five conditions required for the Hardy-Weinberg principle to work?

A 
No mutations
Population is isolated - no new alleles
No selection
Large population
Mating is random
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6
Q

What does p equal?

A

Dominant allele

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7
Q

What does q equal?

A

Recessive allele

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8
Q

What are the two Hardy-Weinberg equations?

A

p + q = 1

p^2 + q^2 + 2pq = 1

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9
Q

What are the three ways in which variation occurs?

A

Mutations, meiosis, random fertilisation of gametes

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10
Q

How does meiosis produce variation?

A

Nuclear division produces new combinations of alleles

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11
Q

What does stabilising selection do?

A

Preserves the average phenotype by reducing the variation of values around the mode

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12
Q

What does directional selection do?

A

Favours an extreme phenotype

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13
Q

What does disruptive selection do?

A

Favours both extreme phenotypes

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14
Q

How does directional selection occur?

A

Natural selection

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15
Q

What may disruptive selection result in?

A

Speciation

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16
Q

How does disruptive selection occur?

A

There are two environments and a different characteristic is advantageous in each

17
Q

Are environmental factors usually controlled by a single gene?

A

No - normally it is many

18
Q

What will we get if we plot an environmental factor on a graph?

A

Bell shaped normal distribution curve

19
Q

Where variation is largely due to genetic factors, how can this information be represented?

A

On a bar chart or line graph

20
Q

Are genetic factors usually controlled by a single gene?

A

Yes

21
Q

What are selection pressures?

A

The environmental factors limiting the population of a species

22
Q

What is a gene pool?

A

The total number of alleles within a population

23
Q

Why have species evolved to have high reproductive rates?

A

To ensure there is a sufficiently large next generation

24
Q

How do large reproductive rates contribute to natural selection?

A

When there are too many individuals for the environment to support, infraspecific competition occurs which ensure the best adapted survive and the worst adapted die

25
Q

Why is variation important?

A

To adapt to changing conditions

26
Q

What impact does environment have on allelic frequency?

A

Impacts the frequency of a mutant allele that is already in the gene pool

27
Q

What is speciation?

A

The evolution of a new species from an existing one

28
Q

What is adaptive radiation?

A

Population separates
Mutations occur, forming new alleles
Each environment is slightly different - different selection pressures
Natural selection leads to changes in allelic frequency

29
Q

What is genetic drift?

A

In small populations, there is a smaller gene pool
As there are so few alleles, there is an uneven chance of each being passed on
Once passed on, a high frequency means the whole population is impacted quickly
Population changes rapidly - more likely to form new species

30
Q

What is allopatric speciation?

A 
A species is geographically separated
There are different environments
Mutations = new alleles
Different selection pressures
Different alleles become advantageous
Natural selection occurs
New species formed
31
Q

Which type of speciation involves geographical isolation?

A

Allopatric

32
Q

Example of allopatric speciation

A

Galapagos finch

33
Q

What is sympatric speciation?

A

A species is separated in some way other than geographic separation

34
Q

Examples of ways species can be separated:

A

Geographical
Ecological
Mechanical

AQA A-Level Biology (22 decks)

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