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Biology Year 2 > Chapter 18 + 19 - Populations And Evolution, Populations In Ecosystems > Flashcards

Chapter 18 + 19 - Populations And Evolution, Populations In Ecosystems Flashcards

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1
Q

What is a species

A

Organisms that can reproduce to produce fertile offspring

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2
Q

What is a population

A

All of the organisms of a single species in one place at one time

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3
Q

What is a community

A

All the organisms of all the species in one place at one time

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4
Q

What is a gene pool

A

All the alleles present in a population

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5
Q

What is allele frequency

A

How common an allele is in the population

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6
Q

What is meant by evolution

A

A change in allele frequency over time

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7
Q

What’s meant by differential reproductive success

A

Organisms with a phenotype better adapted to their environment have a selective advantage and are more likely to survive and reproduce and vice versa

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8
Q

What is meant by speciation

A

The process of forming a new species

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9
Q

What is the purpose of the Hardy-Weinberg principle

A

Predicts the frequency of alleles, genotypes and phenotypes in a population

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10
Q

What does the Hardy-Weinberg principle predict

A

The frequency of alleles of a gene will stay constant over generations

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11
Q

What are the assumptions of the Hardy-Weinberg principle

A
  • No mutations
  • No selection
  • Random mating
  • Large population (no genetic drift)
  • Population is genetically isolated
  • No migration between populations
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12
Q

What is the equation for the Hardy-Weinberg principle

A

P + q = 1
P = All dominant alleles
Q = All recessive alleles

If you know the frequency of one allele you can find the frequency of the other

p^2 + 2pq + q^2 = 1
P^2 = Homozygous dominant
2pq = Heterozygous
q^2 = Homozygous recessive

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13
Q

Research Hardy-Weinberg to understand it

A

Research

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14
Q

What is infraspecific variation

A

Individuals of the same species have the same genes but different alleles
There is variation in their phenotypes

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15
Q

What is interspecific variation

A

Individuals of different species have different genes and and live in different environments

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16
Q

What is continuous variation

A

Variation is not discrete so can not be set into specific categories
Represented on a line graph
Eg height

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17
Q

What is discontinuous variation

A

Individuals fall into discrete groups with no intermediates
Represented on a bar chart
Eg blood group

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18
Q

What are the causes of variation

A 
Genetic
- Mutation
- Meiosis (crossing over and independent segregation)
- Random fertilisation
- Inherited by next generation 
Environmental
- Environment can influence phenotype
- Can change over lifetime eg accent 
Most variation is likely to be as a result of both eg height due to genetics and childhood nutrition
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19
Q

What is speciation

A

The process of forming a new species

  • Populations becomes reproductively isolated
  • There can be no gene flow between them
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20
Q

What is meant by allopatric speciation

A
  • Geographical isolation resulting in reproductive isolation
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21
Q

What is meant by sympathetic speciation

A

Speciation occurs when species are not geographically isolated or reproductively isolated, therefore can be:
Morphological - anatomy
Seasonal - reproductive at different times of years

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22
Q

Explain how speciation occurs

A
  • Variation exists in population due to mutations and environmental differences
  • Different selection pressures eg environmental conditions, courtship behaviour
  • Directional selection of different phenotypes
  • Differential reproductive success
  • Causes a change in allele frequency over many generations
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23
Q

What is meant by genetic drift

A

When there is a change in allele frequency between generations due to random chance

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24
Q

What are some characteristics of genetic drift

A
  • It affects small populations much more than large populations
  • Changes the allele frequency so is a cause of evolution
  • Does not depend on the environment
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25
Q

Explain directional selection

A
  • A change in environmental conditions
  • Individuals with an extreme type of characteristic are more likely to survive and reproduce
  • Parent population is exposed to antibiotic
  • Only those with allele for resistance will survive and reproduce
  • Antibiotic resistance allele will increase in offspring
  • The mean amount of antibiotic resistance changes
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26
Q

Draw the graph for directional selection

A

In folder

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27
Q

Explain stabilising selection

A
  • Individuals with extreme types of characteristic are less likely to survive and reproduce
  • Most extreme likely to die
  • Most likely to survive in middle range
  • Means remains the same
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28
Q

Draw the graph showing stabilising selection

A

Folder

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29
Q

What is meant by disruptive selection

A

When both extremes of the phenotype are more likely to survive and reproduce than the mean phenotype
The environment selects for 2 separate phenotypes
Contribute to sympathetic speciation

30
Q

Draw the graph showing disruptive selection

A

In folder

31
Q

What is an example of disruptive selection

A

Environment = black rocks and white rocks
White and black rabbits survive due to camouflage
Intermediates don’t survive

32
Q

What is meant by abundance

A

The number of individuals of a single species in an ecosystem/habitats (population size)

33
Q

What is meant by distribution

A

Where a species is found in an ecosystem/habitat

34
Q

What is meant by infraspecific competition

A

Competition within a species

  • occupy the same niche
  • Compete for everything such as food and mates
35
Q

What is meant by carrying capacity

A

The maximum stable population an ecosystem can support

36
Q

Draw a graph showing carrying capacity and population

A

In folder

37
Q

Why does carrying capacity vary

A

Due to biotic and abiotic factors that are limiting factors

38
Q

What are examples of biotic and abiotic factors that can act as limiting factors to a carrying capacity

A

Biotic - competition for food

Abiotic - Nesting sites

39
Q

Draw a graph showing predator-prey relationship

A

In folder

40
Q

What is meant by interspecific competition

A

Competition between species

  • The abundance of one species will affect the other
  • Species with a similar niche will compete for resources
41
Q

What is meant by a niche

A

The role that an organism plays in an ecosystem

42
Q

What are examples of biotic factors that make up a niche

A
  • Interspecific competition for resources
  • What it eats
  • What eats it
43
Q

What abiotic factors make up a niche

A
  • Shade
  • The availability of gases it uses
  • Absorption if nitrates
  • Where it lives
  • Temperature
44
Q

Explain why each species has its own niche

A
  • If 2 species had exactly the same niche they would compete for everything
  • Species can have similar niches, known as a niche overlap
  • Causes interspecific competition
45
Q

What will the abundance of a species depend on in an ecosystem

A

How much competition for resources exists

46
Q

What will the distribution of a species depend on in an organism

A

Where it’s niche exists

47
Q

What are transects and quadrants used to survey

A

Immobile or slow moving organisms eg plants

48
Q

What type of sampling are transects used for

A

Systematic

50
Q

What is the purpose of systematic sampling

A

Records the distribution of the organisms/species changing in a line
Eg between high and low tide

51
Q

Explain the process of line transects

A
  • Run a tape measure between 2 points

- Record all of the species on that line

52
Q

Explain the process of belt transects

A
  • Using quadrants along three length of the transect
53
Q

What type of sampling are quadrants used for

A

Random sampling

54
Q

What is the purpose of random sampling

A

Records the abundance of species in an area

55
Q

What is the purpose of sampling

A
  • Impossible to count all organisms
  • Samples have to be representative of the whole ecosystem
  • Sample data can be used to estimate the total number of individuals in an ecosystem
56
Q

Explain random sampling

A
  • Divide sampling area into a grid
  • Number squares
  • Use random number generator to choose coordinates
  • Avoids bias
57
Q

Explain and give an example of non-random sampling

A

Systematic sampling

Samples taken at fixed intervals

58
Q

How does the number of samples influence data

A
  • Can be more representative of population
  • Larger number is more reliable
  • Too many is a waste of time and resources
  • Need enough data to carry out statistical test
  • calculate a running mean, stop when mean levels out
59
Q

What is the purpose of mark-release-recapture

A

Used to estimate the abundance of a mobile species eg fish or rabbits

60
Q

Explain the method for mark-release-recapture

A
  • Capture organisms using appropriate method
  • Make them in a way that doesn’t harm them (doesn’t effect their ability to mate, doesn’t increase their chance of predation)
  • Wait (long enough for them to redistribute amongst population, not too long so that births/deaths and immigration/emigration take place
  • Capture second sample
  • Use equation
61
Q

Explain the process of interrupted transect

A
  • Using quadrants at fixed intervals along the transect
62
Q

What is meant by succession

A

A series of changes in a species composition in a given place over time

63
Q

What is meant by climax community

A

The final stage of succession, where few species dominate and there is a stable equilibrium of species

64
Q

Draw a diagram and explain the process of succession

A
  • Area is colonised by pioneer species
  • This makes the environment less hostile eg due to increase in nutrients like phosphate
  • This allows other species to out-compete preceding species
  • This continues until climax community is reached eg woodland
65
Q

What factors increase as succession take place

A 
Soil depth
Water and nutrient availability
Biodiversity 
Plant height
Niches
66
Q

What factor decreases as succession takes place

A

Light intensity near the ground

67
Q

What are the three types of succession

A

Primary
Secondary
Deflected

68
Q

Explain primary succession

A
  • Starts from newly formed land with no soil
  • Harsh abiotic conditions
  • Very slow to climax
69
Q

Explain secondary succession

A
  • Starts from land where vegetation has been cleared eg deforestation, fire
  • Less harsh abiotic conditions (more soil etc)
  • Much faster to climax
  • Pioneer species can be larger
70
Q

What is meant by deflected succession

A

A community that remains stable because human activity prevents natural succession from taking place eg mowing and grazing

71
Q

Explain what happens when deflected succession takes place

A
  • Succession stops as plants can’t grow
  • Therefore can’t be outcompeted
  • Grassland becomes climax community
72
Q

Why are not all climax communities the same

A

Different ecosystems have different abiotic conditions so develop into different climax communities

73
Q

What is the formula to work out total population from mark-release-recapture

A

Total no. of individuals caught in 1st sample x total no. In 2nd sample / no. of make in 2nd sample

Biology Year 2 (10 decks)

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