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A Level > Biology: Genetics, Populations, Evolution and Ecosystems > Flashcards

Biology: Genetics, Populations, Evolution and Ecosystems Flashcards

1
Q

What’s the difference between genotype and phenotype?

A

Genotype: the combination of alleles in an organism.

Phenotype: observed characteristics of an organism.

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2
Q

What is an allele?

A

A variation of a gene.

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3
Q

What’s the difference between diploid and haploid cells?

A

Diploid: a cell which contains 2 pairs of homologous chromosomes.
Haploid: a cell which contains half the number of chromosomes.

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4
Q

What does chi-squared test for?

A

Goodness of fit, whether results are obtained by chance or not.

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5
Q

What is carrying capacity?

A

The number of organisms supported by an ecosystem without environmental degradation.

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6
Q

What are limiting factors?

A

Factors which could stop/slow the growth of a certain population, such as food, water availability etc.

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7
Q

Why are populations described as dynamic?

A

Populations can vary in size and composition. There are also interactions between species, such as competition and there are many biotic and abiotic factors in an environment.

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8
Q

What is the equation for population growth?

A

(births+immigration)-(deaths+emigration)

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9
Q

What’s the difference between biotic and abiotic factors?

A

Biotic: living factors

Abiotic factors: non-living factors

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10
Q

Give some examples of biotic factors in an ecosystem

A
  • predators
  • competition for space
  • disease
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11
Q

Give some examples of abiotic factors in an ecosystem

A
  • pH (soil)
  • Oxygen concentration
  • temperature
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12
Q

What is an ecological niche?

A

How an organism fits into its role within the environment. It includes where it lives and what it does and biotic/abiotic factors needed for survival.

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13
Q

Why don’t 2 organisms occupy the same niche?

A
  • different tolerance levels to environmental factors.
  • competition
  • in a stable environment, one grows at the expense of the weaker species.
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14
Q

What is a cyclic relationship?

A

One population size increases at the expense of another, this population then decreases as the other increases. This cycle continues.

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15
Q

What are the advantages and disadvantages of random sampling?

A

ADVANTAGES:

  • avoids bias
  • large areas can be covered quickly.

DISADVANTAGES:

  • Chance of not getting any results.
  • Time is limited
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16
Q

What are the advantages and disadvantages of systematic sampling?

A

ADVANTAGES:

  • used for linear habitats.
  • studies distribution of a species.
  • important for when gradual changes happen along a transect.

DISADVANTAGES:

  • maybe inaccurate
  • small chance of bias
  • could take a long time.
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17
Q

What is measuring abundance by frequency and what are the advantages and disadvantages of this?

A

Likelihood of a particular species occurring in a quadrat.

ADVANTAGES:

  • useful for small populations
  • comparable

DISADVANTAGES:

  • may be inaccurate
  • no detail of distribution
  • slower than measuring percentage cover
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18
Q

What is measuring abundance by percentage cover and what are the advantages and disadvantages of this?

A

Estimate the area within the quadrat that a particular plant species covers.

ADVANTAGES:
-fast

DISADVANTAGES:

  • may not be representative of the whole population.
  • may be inaccurate
  • less useful in areas where plants overlap
  • needs to be something we can see
  • only works with plants.
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19
Q

Describe the process of mark-release-recapture.

A
  • catch organism(s)
  • tag the organisms
  • release them
  • randomly collect some of the same organism
  • count the number of animals marked
  • find the estimate population size using equation
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20
Q

what’s the calculation for estimate population size using mark-release-recapture?

A

no. in sample 1 x no. in sample 2 / number of marked individuals recaptured.

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21
Q

which assumptions are made when conducting a mark-release-recapture.

A
  • marked individuals distribute themselves easily
  • population has definite boundary
  • marking is non-toxic and doesn’t make individual stand out.
  • population size is constant.
  • markings not rubbed off/removed
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22
Q

What is the correlation coefficient used for?

A

can be used to prove/disprove associations between samples.

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23
Q

what is the t test used for?

A

it tells you if 2 results are different from eachother.

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24
Q

What is the competitive exclusion principle?

A

the idea that one species is eliminated as a result of succession. this is because they can’t occupy the same niche.

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25
Q

What is succession?

A

The change in species in an area over time. it can be fast or slow.

26
Q

What happens at each stage of succession?

A

each species changes the environment so it becomes more suitable for other species different adaptations.

27
Q

What does the process of succession start and finish with?

A

starts with a pioneer species and finishes with a climax community.

28
Q

What are the characteristics of pioneer species?

A
  • adapted to living in harsh conditions because they colonise areas which other organisms wouldn’t be able to survive in.
  • produce lots of offspring as they die quickly and the species needs to be continued.
29
Q

describe the process of succession.

A
  • pioneer species colonise the area, this area is inhospitable to most species so the pioneer species are adapted to living in harsh environments.
  • pioneer species reproduce quickly, but then die.
  • the envionment is now changed due to the presence of the pioneer species. a new species moves into the area, this species is better adapted to the new conditions and outcompetes the pioneer species. these are known as primary colonisers.
  • the environment keeps changing, it’s more hospitable for other species and so secondary colonisers move into the area, outcompete the primary colonisers and the environment continues to change. secondary colonisers dominate the area.
  • The environment is very well established and a number of species can live there. tertiary colonisers outcompete the secondary colonisers and the environment changes.
  • the result is a climax community. this is often dominated by large trees but the environment is very well established and it can house a number of species. this community doesn’t change, the environment stays the same.
30
Q

What are the 3 measures of biodiversity? explain each

A
  • species diversity (no. of species in area)
  • genetic diversity (no. of alleles in area)
  • ecosystem diversity (variation in ecosystems)
31
Q

What is the definition of preservation?

A

maintaining individuals in their current state without exploitation of their natural resources.

32
Q

What is the definition of conservation?

A

allowing ecosystems to evolve naturally, without natural resources being overused.

33
Q

What are the 2 types of conservation? explain each.

A
  • ex-situ: individual endangered species in zoos, active human management.
  • in-situ: whole ecosystems and landscapes.
34
Q

How does conservation allow succession to happen?

A

it involves managing species naturally with no detrimental effects on any stage of succession. it also enables maximum diversity and ecosystems.

35
Q

Which stage of succession is the highest priority for conservation?

A

the highest priority is mid-succession. this is because it isn’t dominated by one species, and it’s not a harsh environment so it can support a number of species, so it has the highest biodiversity.

36
Q

Why does the community of an area return to a climax community faster in secondary succession as opposed to primary succession?

A
  • the environment isn’t as hostile as it’s already undergone primary succession.
  • spores and seeds are already present.
37
Q

why are heath moorlands burnt?

A
  • prevents dominance/climax community.
  • destroys seedlings of complex organisms, preventing dominance
  • increases complexity of food webs
  • increases biomass
38
Q

what would happen to a heath moorland if it wasn’t burned or grazed on?

A

the succession cycle would continue, the enviromnent would continue to change and develop, there would be a dominant species, reducing species diversity. climax community is formed.

39
Q

what is a dominant allele?

A

masks the expression of another allele of the same gene. dominant character is expresses because of the presence of the dominant allele.

40
Q

what is a recessive allele?

A

if present, it has its expression masked by a dominant allele. the characteristic can only develop in the absence of a dominant allele.

41
Q

how can genetic variation happen?

A
  • sexual reproduction
  • segregation of homologous chromosomes during meiosis
  • random fertilisation
  • crossing over
  • mutation
42
Q

what is natural selection?

A

When changes in the environment result in the least adapted organisms dying out, favouring the organisms with the best adaptations so that they can pass on the successful alleles onto their offspring.

43
Q

What is stabilising selection?

A

a type of selection pressure which decreases the frequency of extreme phenotypes.

44
Q

What is directional selection?

A

when selection pressure increases the frequency of one extreme.

45
Q

Which factors increase/decrease the chance of selection?

A
  • Predation as they adapt to eachother (increases selection)

- Disease as some individuals are immune, others die (increases selection)

46
Q

Name some factors required for evolution to occur.

A
  • successful alleles
  • stable environment
  • large population
  • genetic diversity
  • sufficient resources
47
Q

what is disruptive selection?

A
  • favours the extremes at the expense of the intermediate phonetypes.
  • occurs when an evironmental factor takes 2 or more distinct forms.
  • creates 2 new species
48
Q

what will the total frequency of alleles always be?

A

1

49
Q

what is the hardy-weinberg principle?

A

equation used to calculate the frequencies of alleles of a particular gene in a population.

50
Q

what is the hardy-weinberg equation?

A

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

p^2 = homozygous dominant
2pq = heterozygous
q^2 = homozygous recessive
51
Q

What are the 5 conditions for the hardy-weinberg principle to be used?

A
  • no mutations arise
  • population is isolated
  • no selection bias
  • population is large
  • mating is random
52
Q

what is the definition of speciation?

A

the evolution of a new species from an existing species which enables evolutionary change and diversity.

53
Q

How does speciation happen through geographic separation?

A
  • species all live, interbreed and migrate to and from eachother in one geographical range.
  • a distuirbance means that species no longer come into contact with eachother. they can’t migrate or interbreed anymore.
  • selection pressures lead to changes in populations over time, different alleles are favoured.
  • one or both populations undergo mutations due to differing selection pressures.
  • allele frequencies change.
  • results in then being unable to interbreed even if the barrier is removed (adaptive radiation)
54
Q

What is allopatric speciation?

A

geographic separation through a physical barrier causes speciation?

55
Q

what is sympatric speciation?

A

same location, reproductive isolation

56
Q

What is dihybrid inheritance?

A

2 characteristics determined by 2 genes on different chromosomes are inherited.

57
Q

What is codominance?

A

when both alleles are expressed in the phenotype.

58
Q

What is sex-linkage?

A

When genes are located on sex chromosomes (X or Y). haemophilia gene is located on the X chromosome so more men have it than women.

59
Q

What is an atutosome?

A

any chromosome which isn’t a sex chromosome.

60
Q

What is autosomal linkage?

A

when 2 or more genes are carried on the same autosome.

61
Q

What is epistasis?

A

when the expression of one gene has an effect on the expression of another.

A Level (36 decks)

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