Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Biology Longridge Towers School > Chapter 18 Populations and Evolution > Flashcards

Chapter 18 Populations and Evolution Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is evolution?

A

A change in allele frequency in a population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a gene pool?

A

All of the alleles of all of the genes of all of the individuals of a population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is allelic frequency?

A

The number of times an allele occurs in the gene pool.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the process of evolution in 4 steps.

A
  1. There is variation in a population due to mutation.
  2. Selection pressures are applied.
  3. Those with favourable characteristics survive and reproduce
  4. Favourable alleles get passed on
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does the Hardy-Weinberg principle calculate?

A

The frequency of an allele in a population.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What 5 assumptions does the Hardy-Weinberg Principle make?

A
  1. Large population
  2. No genetic drift
  3. No natural selection
  4. No mutation
  5. Random mating
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the two equations used to calculate HWP?

A

p + q =1
p2 +2pq + q2 = 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does p represent?

A

The frequency of dominant allele.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does q represent?

A

The frequency of the recessive allele.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does 2pq represent?

A

The frequency of heterozygotes in the population.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What can cause variation in phenotype?

A

Genetic and environmental factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where does genetic variation come from?

A
  1. Mutations
  2. Meiosis
  3. Random fertilisation of gametes.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are selection pressures?

A

Factors which limit the population of a species.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Give 3 examples of selection pressures?

A

Predation

Disease

Competition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What 3 factors does evolution by natural selection rely on?

A
  1. Organisms produce more offspring than the environment can support.
  2. There is genetic variety within the populations of species.
  3. There are a variety of phenotypes that selection operates against.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why is the overproduction of offspring important in natural selection?

A

If there are more offspring than the environment can sustain, there will be intraspecific competition. the most likely to survive will be those best adapted to the environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is variation important in natural selection?

A

Variation within a population allows for the selection pressure to change over time, and for the population to evolve and adapt to new circumstances.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the three types of selection?

A
  1. Stabilising
  2. Directional
  3. Disruptive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Draw a graph 9with 2 lines) to represent the effect of stabilising selection.

A
20
Q

Under what conditions does stabilising selection occur?

A

Stabilising selection occurs when the environment favours those with the most common characteristic – those on the extreme dies out.

21
Q

Give 2 examples of stabilising selection.

A

Clutch size in robins.

Human birth weight.

22
Q

Draw a graph to represent directional selection.

A
23
Q

Under what conditions does directional selection occur?

A

Directional selection occurs when the environment favours those individuals with characteristics on one of the extremes.

24
Q

Give 2 examples of directional selection.

A

Colour in peppered moths.

Neck length in giraffes.

25
Q

Draw a graph to represent disruptive selection.

A
26
Q

Under what conditions does disruptive selection occur?

A

Disruptive selection can occur when the environment changes between both extreme conditions hence, individuals on both extremes are favoured at different times and increase in number. This is the least common type of selection.

27
Q

Give 2 examples of disruptive selection.

A

Colouration in african swallowtail butterflies.

Shell colour in limpets.

28
Q

What is speciation?

A

Speciation is the evolution of a new species from existing ones.

29
Q

What is a species?

A

A group of individuals with a shared ancestry, share the same genes, but different alleles and are able to breed to produce fertile offspring. They are reproductively isolated from other species.

30
Q

What are the stages in speciation?

A

I’M a New Species!
Isolation - populations are separated by an isolating mechanism so they cannot interbreed. There is no gene flow.
Mutation - different mutations accumulate in the 2 populations leading to variation
Natural Selection - natural selection acts on the populations with different selection pressures

Eventually the 2 populations become sufficiently genetically different so that when placed together they are unable to interbreed to produce fertile offspring and a new species is formed.

31
Q

What is gene flow?

A

Gene flow is the movement of genes from one population to another.
If there is a barrier to gene flow then genetic differences between populations can accumulate.

32
Q

Name the two types of speciation.

A

Allopatric and sympatric.

33
Q

What are the isolating mechanisms that result in allopatric speciation?

A

Allopatric speciation results from geographical isolating mechanisms such as:
Mountain ranges

Rivers

Oceans

Deserts

34
Q

What are 4 isolating mechanisms that result in sympatric speciation?

A

Sympatric speciation happens in the same geographical location.
Sympatric speciation can be caused by:
1. Ecological isolation

  1. Mechanical isolation
  2. Behavioural isolation
  3. Temporal isolation
35
Q

What is ecological isolation?

A

The populations inhabit different niches within the same habitat so do not meet to breed.

36
Q

What is mechanical isolation?

A

During mechanical isolation the populations are in the same habitat but are physically incompatible so cannot interbreed.

37
Q

What is behavioural isolation?

A

Differences in behaviour prevent breeding. Examples include:
Differences in song to attract mates.

Differences in mating displays.

38
Q

What is temporal isolation?

A

Temporal isolation occurs when the populations live in the same habitat but their breeding times do not overlap.

39
Q

What are the 2 mechanisms that prevent 2 individuals from producing fertile offspring?

A

The inability to produce fertile offspring is caused by:
Gametic Isolation

Hybrid sterility

40
Q

What is genetic isolation?

A

The gametes are unable to fuse due to genetic or biochemical incompatibility.

41
Q

Give 3 causes of gametic isolation.

A

Gametic isolation could be due to:
Sperm being unable to survive in the reproductive system of the female.

Enzymes on the sperm being unable to react with the egg to allow entry.

Pollen being unable to create a pollen tube.

42
Q

What is hybrid sterility?

A

Hybrids are often sterile due to an inability of chromosomes to pair up during meiosis.
Genes cannot be passed on.

43
Q

What is adaptive radiation?

A

Adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches.

44
Q

What is genetic drift?

A

Genetic drift is the process of random changes in allele frequency due to a chance event. It affects small, isolated populations.

45
Q

Why does genetic drift affect small isolated populations more?

A

Genetic drift has a greater impact in small, isolated populations, as alleles are more likely to be lost from the gene pool. It can lead to the random loss of rare alleles, reducing the genetic diversity of a population.

46
Q

What is the bottleneck effect?

A

Genetic bottlenecks occur when a small number of individuals are the only contributors to future generations. This can happen when most of the population dies out.

47
Q

What is the founder effect?

A

The founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

A-level Biology Longridge Towers School (37 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions