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2B > Populations etc > Flashcards

Populations etc Flashcards

1
Q

What are the sources of genetic variation?

A

Mutation, meiosis (through crossing over of chromatids and independent segregation) and because of random fertilisation.

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2
Q

Define evolution

A

When the frequency of an allele in a population changes over time

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3
Q

Outline how natural selection works.

A
  1. Individuals of the same species cary due to having different alleles.
  2. Prediation, disease and competition (selection pressures) create struggle for survival. Some are better adapted than others.
  3. Individuals with a phenotype that increases their chance of survival are more likely to survive, reproduce and pass on their genes.
    4 So a greater proportion of the next generation inherit the allele.
  4. This process repeats and the freq of the beneficial allele increases from generation to generation.
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4
Q

What is stabilising selection?

A

Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce.

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5
Q

When does stabilising selection occur?

A

When the environment isn’t changing

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6
Q

What does stabilising selection actually do?

A

Reduce the range of possible phenotypes

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7
Q

What is directional selection?

A

Where individuals with allele for a single extreme phenotype are more likely to survive and reproduce.

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8
Q

What is directional selection in response to?

A

An environmental change.

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9
Q

What is disruptive selection?

A

Where individuals with alleles for extreme phenotypes at either end of the range are more likely to survive and reproduce.

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10
Q

When does disruptive selection occur?

A

When the environment favours more than one phenotype.

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11
Q

Define population

A

A group of organisms of the same species occupying a particular place at a particular time, that can potentially interbreed.

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12
Q

Define gene pool.

A

The complete range of alleles present in a population

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13
Q

What is allele frequency?

A

How often an allele occurs in a population.

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14
Q

What is P?

A

frequency of one allele (dominant)

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15
Q

What is Q?

A

frequency of the other allele (recessive)

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16
Q

What is P2?

A

frequency of homozygous dominant allele

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17
Q

What is Q2?

A

frequency of homozygous recessive allele

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18
Q

what is 2pq?

A

frequency of heterozygous genotype

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19
Q

Which equation is used to predict allele frequency?

A

p+q=1

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20
Q

Which equation is used to predict genotype and phenotype frequency?

A

p2+2pq+q2+1

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21
Q

What is speciation?

A

The development of a new species from an existing species.

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22
Q

When does speciation occur?

A

When members of the same species become geographically isolated; changes in allele frequency cause change in phenotype, meaning they can no longer interbreed to produce fertile offspring.

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23
Q

Outline allopatric speciation.

A
  1. Populations that are geographically separated will experience slightly different conditions.
  2. Meaning they’ll have different selection pressures, so changes in allele frequency could occur. (Egdifferent alleles will become more advantageous, so directional selection acts on certain alleles).
  3. This leads to differences accumulating in the gene pools of the separated populations of the separated populations, causing changes in phenotype frequencies.
  4. Eventually, the two groups are so different that they can’t produce fertile offspring, so have become reproductively isolated.
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24
Q

What is sympatric speciation?

A

When random mutations occur within a population, preventing members of that population from breeding with other members of the species.

25
Q

What are the three ways in which reproductive isolation can occur?

A
  • seasonal (individuals from same pop develop diff flowering / mating seasons, or become sexually active at diff times of year)
  • mechanical (changes t genitalia prevent successful mating)
  • behavioural (a group of individuals develop courtship rituals that aren’t attractive to the main population)
26
Q

What is genetic drift?

A

Chance (rather than environmental factors) dictates which individuals survive, breed and pass on their alleles/

(Eg one allele being passed on more often than others).

27
Q

When does evolution by genetic drift have a greater effect?

A

In smaller populations where chance has a greater influence.

28
Q

Define habitat

A

The place where an organism lives.

29
Q

Define community

A

Populations of different species in a habitat

30
Q

Define ecosystem

A

A community, plus all the abiotic conditions in an area in which it lives.

31
Q

Define abiotic factors.

A

The non-living features of the ecosystem, e.g. temp, availability of water

32
Q

Define biotic conditions.

A

The living features of an ecosystem, e.g. presence of predators.

33
Q

Define niche.

A

The role of a species within its habitat. Eg what it eats, what and when it feeds.

34
Q

Define adaptation.

A

A feature that members of a species have that increases their chance of survival and reproduction. e.g. giraffes long necks.

35
Q

How many species can occupy one niche?

A

Only one

36
Q

What happens if two species try to occupy one niche?

A

They will have to compete with each other

37
Q

Give an example of an adaptation to abiotic conditions.

A

Seals have a thick layer of blubber to help them keep warm in the coldest seas.

38
Q

give an example of an adaptation to biotic conditions.

A

Male frogs produce mating calls to attract females, this ensures they attract a mate of the same species.

39
Q

What is the carrying capacity?

A

The maximum stable population size of a species that an ecosystem can support. This varies as a result of both biotic and abiotic factors.

40
Q

Interspecific competition is a biotic factor. Outline this.

A

Competition between different species e.g. for the same resources.

41
Q

What does interspecific competition result in?

A

Reduced resources available to both populations, or one species is better adapted so the less one will become out-competed.

42
Q

Outline infraspecific competition.

A

Members of the same species compete with each other for the same resources

43
Q

Predation is a biotic factor. Outline this.

A

Where the predator kills and eats they prey1

44
Q

what are the two ways in which transects can be used?

A

Species frequency or % cover

45
Q

What is a belt transect?

A

Whee quadrants are placed next to each other, along the transect to work out species freq / % cover. Can be placed at intervals if needed at larger distances (aka interrupted belt transect)

46
Q

What is the process of MRR?

A
  1. Capture a species using an appropriate technique ( e.g. pitfall traps).
  2. Mark them in a harmless way.
  3. Release back into their habitat.
  4. Wait a week, then take a second sample from the same population.
  5. Count how many of this second sample are marked.
47
Q

What is the MRR equation?

A

Total population size = no caught in 1st sample x no caught in 2nd sample / number marked in 2nd sample.

48
Q

What assumptions are made in MRR?

A
  • no changes in pop size die to births, deaths.
  • marked sample has had time and opportunity to mix back in with the population.
  • marking hasn’t affected chances of survival.
49
Q

Outline the process of succession.

A
  1. Primary succession; when a species colonise a new land surface. The abiotic conditions are harsh, so only pioneer species can survive due to adaptations.
  2. These pioneer species change the abiotic conditions, making it less hostile as they die and microorganisms decompose the humus, forming a basic soil.
  3. Eg the basic soil can retain water, so new organisms with diff adaptations can move in and grow. They cycle continues.
  4. Secondary succession then occurs where the land has been cleared of all plants but soil remains.
  5. At each stage, diff plants that are better adapted for the new conditions move in, out-compete and become the dom species.
  6. As succession continues, the ecosystem becomes more complex. New species move in alongside old so the biodiversity increases.
  7. Then reaches climax community - the ecosystem is supporting its largest and most complex community of plants and animals it can.
50
Q

what is plagioclimax?

A

When human activities prevent succession, stopping a climax community from developing (stopped artificially).

51
Q

what is conservation?

A

The protection and management of species and habitats in a sustainable way.

52
Q

Give a couple of examples of conservation.

A
  • fishing quotas
  • protected areas e.g. nature reserves
  • endangered species bred in captivity to increase numbers, then returned to the wild.
53
Q

How is biomass measured?

A
  1. A sample of the organism is dried (often in an oven). The sample is weighed at regular intervals (e.g. everyday). Once the mass becomes constant, you know that all the water has been removed.
  2. The mass of carbon is said to be 50% of the dry mass.
54
Q

How can you use a calorimeter to measure biomass?

A
  1. A sample of dry biomass is burnt, and the energy released is used to heat a known volume of water.
  2. The change in temperature of the water is used to calculate the chemical energy of the biomass.
55
Q

What is GPP?

A

The total amount of chemical energy converted from light energy from plants, in given area, in a given time.

56
Q

What is NPP?

A

The energy available to the plant for growth and reproduction; the energy is stored in the plant’s biomass.

57
Q

How do you calculate NPP?

A

GPP - respiratory losses.

58
Q

What is the equation for the net production of consumers?

A

N = I - (F+R)

I = chemical energy in injected food 
F = chemical energy lost in faeces and urine
R = energy lost through respiration.
59
Q

How is energy lost at each trophic level?

A
  • some energy is indigestible, so are ejected as faeces

- some is lost to the environment through respiration or excretion of urine,

2B (26 decks)

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