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2. A level year 13 > Natural selection and speciation > Flashcards

Natural selection and speciation Flashcards

1
Q

Genetic and environemntal factors cause ……

A

Variation

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2
Q

What is the primary source of genetic variation?

A

Mutation

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3
Q

Define gene pool

A

All of the alleles of all of the genes of all the individuals within a particular population at a given time

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4
Q

What is intraspecific competition?

A

competition between individuals of the same species

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5
Q

Give 3 reasons why differential survival and reproduction could occur.

A

Prediation

Disease

Competition

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6
Q

An organism has a selecive advantage. What does this mean?

A

Better adapated for the conditions present.

More likley to survive and reproduce.

Pass on favourable alleles

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7
Q

How is genetic variation produced/

A

Crossing over

Independent segregation/random assortment

random fusion of gametes

Mutation

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8
Q

Name 3 types of selection

A

Stabilising

Directional

Disruptive

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9
Q

Describe stabilising

A

Preserves the average phenotype

Selection against extreme phenotypes.

Occurs when enviornment is stable

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10
Q

Give an example of stailising selection

A

Human birht wieght

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11
Q

Give an example of directional selection

A

Antibioitic resistance in bacteria

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12
Q

Give a defition of speciation

A

Evolution of a new species from an existing one

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13
Q

Define a species

A

Group of similar organisms that breed producing fertile offspring

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14
Q

Give the 2 types of speciation

A

Allopatric and sympatric

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15
Q

The effect of genetic drift is greater on which population size - small or large?

A

small

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16
Q

Allopatric speciation occurs when …..

A

When 2 populations become geographically isolated

17
Q

Give examples of how organims might be geographical isolatied

A

physical barrier which prevents interbreeding e.g. oceans, rivers, mountains, deserts.

18
Q

Define reproductive separation

A

when 2 populations can no longer interbreed and produce fertile offspring

19
Q

Example of allopatric speciation

A

Finches on the Galapagos Islands!

20
Q

Sympatric means

A

same country

21
Q

Sympatric speciation occurs

A

within a population of organisms living in the same area (doesnt require geographical isolation)

22
Q

sympatric speciation arises because

A

they have different breeding seasons, they may inhabit different habitats in the same area so never meet, anatomical differences,

23
Q

Name the type of selection shown

A

stabilising

24
Q

name the type of selection shown

A

directional

25
Q

Describe how allopatric speciation occurs

A

Two populations are geographically isolated

Creates separate gene pools with no interbreeding

Variation due to mutaiton

Different selection prressures

Differential reproductive success

Leeds to change in allele frequencies

Occurs over long period of time

Populations no longer albe to interbreed to produce fertile offspring

26
Q

Name the type of selection shown

A

Disruptive

27
Q

What does evolution do to the frequency of alleles in a population?

A

Changes them - increase or decrease

28
Q

What happens to the frequency of the alleles that give organisms an advantage?

A

Increases

29
Q

What happens to those organisms that are better adapted to the selective pressures in the environment?

A

Survive, reproduce and pass on favourable alleles

30
Q

What happens to the phenotype during stabilising selection?

A

Preserves the middle of the range phenotypes

31
Q

Which phenotype is selected for during directional selection?

A

An extreme phenotype - these are more likely to survive and reproduce

32
Q

What phenotype is preferred in disruptive selection?

A

BOTH extremes (select against the middle phenotype)

33
Q

Genetic drift can lead to ..

A

speciation

34
Q

What is genetic drfit?

A

Chance (not the environment) determines which organisms survive,

reproduce and pass on their alleles

35
Q

Genetic drift has a greater effect on which size population?

A

Smaller populations

36
Q

Describe Sympatric Speciation

A

Occurs in the smae population

Mutations cause variation in alleles

Reproductive separation with no gene flow

Different allleles selevted for

Change in allele frequency

Disruptive selection

Differnet specifies formed which cannot interbreed

2. A level year 13 (19 decks)

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