Chapter 18 - Population and Evolution Flashcards

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?

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
Why is variation important?
To adapt to changing conditions
26
What impact does environment have on allelic frequency?
Impacts the frequency of a mutant allele that is already in the gene pool
27
What is speciation?
The evolution of a new species from an existing one
28
What is adaptive radiation?
Population separates Mutations occur, forming new alleles Each environment is slightly different - different selection pressures Natural selection leads to changes in allelic frequency
29
What is genetic drift?
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
What is allopatric speciation?
``` 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
Which type of speciation involves geographical isolation?
Allopatric
32
Example of allopatric speciation
Galapagos finch
33
What is sympatric speciation?
A species is separated in some way other than geographic separation
34
Examples of ways species can be separated:
Geographical Ecological Mechanical