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A Level Biology Paper 2 > Genetics, Populations, Evolutions And Ecosystems > Flashcards

Genetics, Populations, Evolutions And Ecosystems Flashcards

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1
Q

What is the name for the differences that exist between individuals? This can be caused by genetics and also the environment.

A

Variation.

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2
Q

What is the name for a change in allele frequencies over time? This can occur by natural selection.

A

Evolution.

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3
Q

What are some examples of selection pressures?

A

Predation, disease and competition which creates a struggle for survival.

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4
Q

What is the name for when individuals with alleles for a single extreme phenotype are more likely to survive and reproduce and when does this often happen?

A

Directional selection, it often happens as a response to an environmental change.

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5
Q

What is it called when individuals with alleles for extreme phenotypes at either end of a range are more likely to survive and reproduce and characteristics towards the middle range are lost, and when does this occur?

A

Disruptive selection, it occurs when the environment favours more than one phenotype.

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6
Q

What is speciation?

A

The development of new species from an existing species.

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7
Q

What is sympatric speciation?

A

Speciation that doesn’t require geographical isolation. This could happen due to mutation in a population, which prevents members of the population from breeding with other members of the species.

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8
Q

What is allopatric speciation?

A

Speciation that requires geographical isolation (a river etc).

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9
Q

What is the name of a place where an organism lives?

A

Habitat.

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10
Q

What is the population?

A

All the organisms of one species in a habitat.

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11
Q

What is the community?

A

Population of different species in a habitat.

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12
Q

What is an ecosystem?

A

A community, plus all the non-living conditions in the area.

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13
Q

What does abiotic mean?

A

The nonliving features in an ecosystem, such as temperature and light intensity.

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14
Q

What does biotic mean?

A

The living features of an ecosystem, such as predators and food.

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15
Q

What is a niche?

A

A niche contains the exact resources for an individual species to survive.

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16
Q

What is adaptation?

A

A feature that members of a species have that increases their chance of survival and reproduction.

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17
Q

What is inter-specific competition?

A

Competition between different species.

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18
Q

What is intraspecific competition?

A

Competition between individuals of the same species.

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19
Q

What is the carrying capacity of an ecosystem?

A

The certain size of population of a species that the ecosystem can support.

This is the maximum stable population size of a species it can support.

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20
Q

What is the population size dependent on?

A

The balance between birth rate, death rate and resources available in the habitat.

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21
Q

What can cause variation in population size?

A

~ abiotic factors
~ interactions between organisms (competition, predation)

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22
Q

What is an example of an abiotic factor influencing population size?

A

Light can affect the size of photosynthesising populations, as light intensity increases the rate of photosynthesis would increase. This leads to more growth in the individuals which increases the carrying capacity. Therefore, the carrying capacity of herbivores would increase leading to more spores and seeds being produced.

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23
Q

What happens when niches overlap between species?

A

Competition may occur

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24
Q

What is competitive exclusion?

A

When a species becomes extinct because of the competition for the same niche between two species.

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25
Q

What kind of relationship is predation?

A

An inter-specific relationship.

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26
Q

Why does an increase in predator numbers not always mean a decrease in a species of prey?

A

Because predators often feed on multiple kinds of prey species.

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27
Q

When you are writing about population size, what do you need to include?

A

Births and deaths (more/less individuals)

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28
Q

What do ecologist need to know to study an ecosystem?

A

The abundance and the distribution of organisms in the area.

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29
Q

Why sample?

A

Because it allows ecologist to investigate how biotic and abiotic factors affect an ecosystem.

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30
Q

What are the advantages of sampling?

A

It is more efficient when the area is too large or they are too many individuals to count.

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31
Q

What must sampling be to be accurate?

A

Representative of the population.

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32
Q

What are the two kinds of sampling?

A

Sample using a quadrat
Sampling using mark release recapture.

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33
Q

What are the two kinds of sampling using quadrats?

A

Random sampling and systematic sampling

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34
Q

When should you use Mark release recapture?

A

When an organism is motile.

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35
Q

When should you use a quadrat for sampling?

A

When a slow moving or non-motile organism is being sampled.

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36
Q

When should you use random or systematic sampling?

A

You should use random when the organisms are uniformly distributed, and systematic when there is an uneven distribution.

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37
Q

What is the method for random sampling?

A

Lie to tape measures at the right angle to create a gridded area
Use a random number generator to generate two coordinates
Place the quadrat and collect the data.
Repeat at least 30 times and then calculate the mean.

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38
Q

When do you use systematic sampling?

A

When the estimated population size is unevenly distributed (e.g. populations which change over distance such as rivers or Rocky Shores).

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39
Q

What equipment would you use for systematic sampling?

A

A trans sect

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40
Q

What is a belt transact?

A

The quadrat is placed at every position along the tape measure.

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41
Q

What is an interrupted belt transect?

A

The quadrat is placed at uniform intervals along with the tape measure.

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42
Q

What is the method for systematic sampling?

A

Place the tape measure at the right angle to the…
Place the quadrat every (e.g.5 m)
Collect the data
Repeat by placing another 30 transects Right angles to the…

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43
Q

What is the method for systematic sampling?

A

Place the tape measure at the right angle to the…
Place the quadrat every (e.g.5 m)
Collect the data
Repeat by placing another 30 transects Right angles to the…

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44
Q

What are the methods to estimate species abundance?

A

Local frequency (percentage of squares in the quadrant with the species present)
Density (the number of one species in a given area)
Percentage cover (proportion of the ground occupied by the species)

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45
Q

When should you use percentage cover all local frequency over density as an estimate of species abundance?

A

When you cannot identify individual organisms or there are too many to count.

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46
Q

What are the negatives of using local frequency as an estimate of species abundance?

A

It has poor accuracy as it doesn’t consider overlapping plants or the size of a plant.

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47
Q

What are the negatives of using density as an estimate of species abundance?

A

It’s very time-consuming.

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48
Q

What are the negatives of using density as an estimate of species abundance?

A

It’s very time-consuming.

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49
Q

What are the negatives of using percentage cover as an estimate of species abundance?

A

It is subjective which limits accuracy, and it doesn’t consider overlapping plants or the size of a plant.

50
Q

What are the positives of the different estimates of species abundance?

A

Local frequency is a quick method when sampling a large area
Density is more accurate if you can easily distinguish an individual plant or there aren’t too many
Percentage cover is a quicker method than density.

51
Q

What is the method for mark release recapture?

A

An initial sample of the population is captured
Individuals are marked and then released into natural habitat while number caught is recorded
The marked individuals are left for a period of time to allow them to randomly disperse throughout the habitat
The total number captured in the second sample and the number recaptured with the markings is recorded
The size of the population is then estimated

52
Q

What increases the accuracy of mark release recapture?

A

The more times it is repeated

53
Q

What is the calculation for mark repeat recapture?

A

Estimated total population = number of organisms initially caught x number of organisms in second sample ➗ number of marked organisms recaptured

54
Q

What are the ethics of Mark release recapture?

A

The mark cannot cause permanent harm such as not being toxic, increasing chances of predation, reducing chances of reproduction.

55
Q

What are the assumptions of Mark release recapture?

A

The population size is constant
The animals always redistribute evenly (given them sufficient time to do this)
The marking remains visible throughout the sample and doesn’t come off

56
Q

Why would a mark being seen by predators make a mark release recapture sample less accurate?

A

Because the population would be over estimated as they would be proportionally fewer marked individuals in the second sample

57
Q

What is succession?

A

The change in ecological community overtime.

58
Q

What is each stage of succession called?

A

A seral stage

59
Q

What defines a pioneer species?

A

Reproduces asexually
Produces seeds/spores
Photosynthesises
Can tolerate extreme conditions
Nitrogen fixation

60
Q

What could cause the start of the succession cycle?

A

Glacier retreat, sand dunes, volcanoes, subsiding land, river deposition

61
Q

What happens as succession moves through the seral stages?

A

Biomass increases
Diversity of species increases
Depth and nutrient content of the soil increases
There are larger number of habitats and niches
More complex food webs
All of this creates the stability in the habitat.

62
Q

What does primary succession start with?

A

A pioneer species colonising bare land.

63
Q

What are pioneer species adapted to survive in?

A

Harsh abiotic factors

64
Q

How do pioneer species change the abiotic factors to become less harsh?

A

Through their death and decomposition. This forms of thin layer of soil called humus.

65
Q

What can begin to survive after the humus is formed in succession?

A

Mosses and smaller plants, they further increase the depth and nutrients content the soil.

66
Q

What happens when, during succession, the depth and nutrient content of the soil becomes less harsh?

A

Overtime, larger and larger plants can survive and change the environment further.

67
Q

During succession, what happens when larger plants stop being able to survive and change the environment?

A

They make it so that the environment is less suitable for previous species leading to them being out competed by a new colonising species.

68
Q

What is the final stage of succession called?

A

The climax community, in the UK this is Woodlands that are dominated by trees.

69
Q

How does secondary succession begin?

A

When succession is disrupted and plants are destroyed, succession starts again but the soil is already created so it doesn’t start from the bare rock seral stage.

70
Q

What is one way to conserve habitats?

A

By managing succession in a way that prevents a change to the next stage.

71
Q

What is natural selection?

A

When alleles code for a characteristic that increases the organisms chance of surviving, its frequency in the population can increase.

72
Q

What does high genetic diversity in a population mean?

A

A higher chance of having an advantageous allele

73
Q

What does an advantageous allele give organisms?

A

A better ability to survive an environmental changes

74
Q

How many steps are there in natural selection?

A

4

75
Q

What is the first step of natural selection?

A

Mutations, randomly occurring mutations sometimes result in new alleles being formed. Occasionally, these mutations can lead to advantages allele rather than a harmful one which often disappear in species.

76
Q

What is an example of an advantageous allele?

A

A protein that works better than the original.

77
Q

What is genetic diversity?

A

The number of different alleles in a gene of a population.

78
Q

What is step two of natural selection?

A

Differential reproductive success, not all individuals have an equal chance of reproducing. Individuals with an advantageous allele are more likely to survive reproduce and pass on their genes

79
Q

What is the third step of natural selection?

A

Increase in advantageous a little frequency, a greater proportion of the next generation inherit the advert dangerous allele. They intern survive breed and pass on this all. Over generations, the frequency of the allele increases.

80
Q

What is the fourth step in natural selection?

A

Evolution, over generations this leads to evolution as the advantageous of all becomes more common in the population.

81
Q

What does it mean if a population has low genetic diversity?

A

It would be less likely to have an advantageous all that would allow it to adapt to a selection pressure leading to natural selection.
This could wipe out the species!

82
Q

What are the three type of adaptations?

A

Anatomical, behavioural, physiological

83
Q

What is an anatomical adaption?

A

Structural features in an organisms body that increased chances of survival (Darwin finches beaks).

84
Q

What is a behavioural adaptation?

A

The organism acts to increase its chance of survival (hedgehogs roll into balls).

85
Q

What is a physiological adaptation?

A

Processes inside the body which increases the chance of survival(Arctic cod produce antifreeze proteins).

86
Q

What is an exam tip for selection?

A

Look at the shapes of the graphs given, this can tell you which type of selection you need to talk about.

87
Q

What are the three types of selection?

A

Directional
Stabilising
Disruptive

88
Q

What is directional selection?

A

This is selection where individuals with alleles for characteristics at an extreme are favoured.

89
Q

When does directional selection often occur and what is the result?

A

Often occurs when an environmental change takes place (puts selection pressure on one of the extremes)
Population changes until the new suitable phenotype is reached

90
Q

What is an example of directional selection?

A

Bacteria becoming resistant to antibiotics

91
Q

What is stabilising selection?

A

Where individuals with alleles for characteristics towards the middle of the range are favoured, thereby reducing the range of characteristics.

92
Q

What is stabilising selection?

A

Where individuals with alleles for characteristics towards the middle of the range are favoured, thereby reducing the range of characteristics.

93
Q

When does stabilising selection take place?

A

When an environment is stable and unchanging

94
Q

What does stabilising selection tend to do?

A

Eliminate extreme variations from a population, preserving the characteristics of the population

95
Q

What is an example of stabilising selection?

A

Babies of a middle range weight are most likely to survive and are more common

96
Q

What is a gene?

A

A sequence of bases on a DNA molecule that codes for a protein which results in a characteristic

97
Q

What is an allele?

A

A different version of a gene as a result of a slightly different order of bases which code for different versions of the same characteristic, but still the same locus on the chromosome.

98
Q

What is a genotype?

A

The alleles of a gene possessed by an individual.

99
Q

What is a phenotype?

A

The observable characteristics of an organism as a result of both the genotype and the environmental factors.

100
Q

What is dominant allele?

A

And all whose characteristic appears in the phenotype, even when there is only one copy, represented by a capital letter

101
Q

What is a recessive allele?

A

An allele whose characteristic appears in the phenotype and they want two copies of present, represented by a lowercase letter

102
Q

What does codominant mean?

A

We’re both alleles are expressed in the phenotype, neither is recessive.

103
Q

What is the gene locus?

A

The fixed position of a gene on a chromosome. Alleles of a gene found at the same position on each chromosome in a pair

104
Q

What does homozygote mean?

A

When the two allele copies in an individual are the same (e.g. bb or BB)

105
Q

What does heterozygous mean?

A

When the two alley copies in an individual are different (e.g.Bb)?

106
Q

What is a carrier?

A

A person who is carrying an allele which is not expressed in the phenotype but can be pressed onto offspring.

107
Q

What does diploid mean?

A

When there are two sets of a chromosome (one from each parent) the chromosomes are in pairs.

108
Q

What does haploid mean?

A

Where there is only one set of chromosomes, e.g. A gamete

109
Q

What are chromosomes?

A

Thread like structures of DNA

110
Q

What does homologous mean?

A

Pairs of matching chromosomes which are the same size and contain the same genes on the same loci

111
Q

What is a karyotype?

A

An individuals collection of chromosomes

112
Q

What is mono hybrid inheritance?

A

The inheritance of a characteristic controlled by a single gene

113
Q

How should gametesbe represented?

A

In a circle

114
Q

What should you remember to label in a punnet square?

A

The parents (like a title above the genotypes)
Gametes
Phenotype
Genotype

115
Q

What does pure breeding mean?

A

Homologous individuals that can only pass on a single type of allele

116
Q

What are the rules for genetic diagrams that show co dominance?

A

Lowercase letters are not used
Different letters for different alleles
The letters are written as superscript on a letter that represents a gene, e.g. For colour C^R or C^W for red and white

117
Q

What are the rules for genetic diagrams that show co dominance?

A

Lowercase letters are not used
Different letters for different alleles
The letters are written as superscript on a letter that represents a gene, e.g. For colour C^R or C^W for red and white

118
Q

What does multiple alleles mean?

A

Sometimes genes has more than two alleles, an example of this is blood group

119
Q

What is an example of multiple alleles?

A

Bullet types, is there are three alleles for blood group: A B and O

120
Q

What is the difference between the different blood groups?

A

I^A leads to the production of antigen A
I^B leads to the production of antigen B
I^O leads to the production of neither antigen
A and B are codominant to each other, O is recessive

A Level Biology Paper 2 (2 decks)

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