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OFFICIAL Biology AQA Year 2 > Topic 7B: Population and Evolution > Flashcards

Topic 7B: Population and Evolution Flashcards

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1
Q

What is a species?

A

a group of similar organisms that produce fertile offspring

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2
Q

What is a population?

A

a group of organisms of the same species living in a particular area at a particular time

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3
Q

What is a gene pool?

A

Complete range of alleles present in the population

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4
Q

What is allele frequency?

A

How often an allele occurs in a population

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5
Q

What does the Hardy-Weinberg principle predict?

A

that the frequency of alleles in a population wont change from one generation to the next

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6
Q

The Hardy-Weinberg prediction is only true under what conditions?

A
  • large population
  • no immigration/emigration
  • no mutations
  • no natural selection
  • random mating
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7
Q

What do the Hardy-Weinberg equations calculate?

A

-frequency of alleles

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8
Q

What is the equation that calculates allele frequency?

A

p + q = 1

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9
Q

What is the equation that calculates genotype/phenotype frequency?

A

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

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10
Q

p is….

A

dominant

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11
Q

q is….

A

recessive

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12
Q

What is variation?

A

differences that exist between individuals

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13
Q

What causes variation?

A
  • genes
  • the environment
  • or both
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14
Q

Variation within species means….

A

wide range of different phenotypes

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15
Q

Although individuals of the same species have the same genes but

A
  • they have different alleles

- this causes genetic variation

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16
Q

What is the main source of genetic variation?

A 
-mutation
BUT also 
-crossing over
-independent segregation
-random fertilisation
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17
Q

What type of variation is caused within species most commonly?

A

a combination of genetic and environmental factors

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18
Q

Only genetic variation causes….

A

evolution

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19
Q

What is evolution?

A

A change in allele frequencies over time

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20
Q

What is a method by which evolution occurs?

A

Natural selection

21
Q

Outline how evolution changes the allele frequency…

A
  • Individuals of the same species vary between different alleles
  • selection pressures create a struggle for survival
  • organisms better adapted to the selection pressure survive/reproduce/pass onto offspring
  • greater proportion inherit the beneficial alleles
  • changes the frequency of alleles
22
Q

Name the three different types of selections?

A
  • Directional
  • Stabilising
  • Disruptive
23
Q

What is stabilising selection?

A
  • favours the middle of the range
  • environment isnt changing
  • reduces the range of possible phenotypes
  • avoid extremes
24
Q

What is directional selections

A
  • favours an extreme phenotype

- response to environmental change

25
Q

What is disruptive selection?

A
  • favour BOTH extreme phenotypes
  • opposite to stabilising selection
  • middle range is lost
  • environment favours more than one phenotype
26
Q

Explain an example of stabilising selection

A
  • fur length
  • fur at extremes reduced the chance of survival
  • because harder to maintain body temperature
  • so average fur length are most likely to survive and reproduce
27
Q

Explain an example of directional selection

A
  • cheetahs run really fast
  • due to directional selection
  • individuals with increased speed more likely to catch prey
  • these compete with slower individuals and survive and reproduce etc
28
Q

Explain an example of disruptive selection

A
  • range of beak sizes
  • birds with large beaks are designed to eat large seeds
  • birds with small beaks are designed to eat small seeds
  • birds with medium sized beaks have reduce chance of survival
  • pop of small and large beaks increases
29
Q

Name two types of speciation?

A
  • Allopatric

- Sympatric

30
Q

What is speciation?

A

development of new species from an existing one

31
Q

How does speciation occur?

A

when population of the same species becomes reproductively isolated

32
Q

What does it mean being reproductively isolated?

A

when the species can no longer interbreed to produce fertile offspring

33
Q

What is reproductive isolation?

A

changes in allele frequency cause changes in the phenotypes

34
Q

What does geographical isolation lead to?

A

allopatric speciations

35
Q

Outline allopatric speciations

A
  • population geographically isolated due to selection pressure OR genetic variation due to mutation
  • creates physical barrier
  • pop experience different selection pressures
  • different environmental conditions
  • changes in the alleles cause directional selection
  • causes differential reproductive success
  • changes in allele frequency/gene pool
  • they become reproductively isolated
36
Q

Examples of selection pressures

A

predatation, climate, disease

37
Q

What is sympatric speciation?

A

Random mutations that could occur within population, preventing members of that population breeding with other member of the species

38
Q

What is polyploidy?

A

When mutations can occur that increase the number of chromosomes

39
Q

Example of sympatric speciation?

A
  • eukaryotic organisms are diploid
  • if they are polyploidy then reproduction can not happen sexually
  • polyploidy organism becomes reproductively isolated
  • if polyploidy organisms can reproduce asexually they new species could develop
40
Q

Is sympatric speciation more common in plants or animals?

A

Plants

41
Q

What in are the ways species can be reproductively isolated?

A

Changes in:
seasonal
mechanical
behavioural

42
Q

What is a seasonal change?

A

-developing different flowering/mating seasons
OR
-becoming sexually active at different times of the year

43
Q

What is a mechanical change?

A

changes in the genitalia preventing successful mating

44
Q

What is a behaviour change?

A

a group of individuals developing courtship rituals that are not attractive to the main population

45
Q

What is genetic drift?

A

When chance rather than environment factors dictates which individuals survive breed and pass on their alleles.

46
Q

Example of genetic drift

A
  • variation in genotype
  • by chance allele for one genoptype is passed on to offspring
  • allele frequency of that allele increases
  • reproductive isolation
47
Q

Evolution can occur by

A
  • genetic drift

- natural selection

48
Q

When does genetic drift have a greater effect?

A
  • When population size is smaller and so chance has a greater influence
  • in greater population the chance variation tends to even out
49
Q

Evolutionary changes causes..

A

greater diversity

OFFICIAL Biology AQA Year 2 (15 decks)

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