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a-level bio > Topic 7 > Flashcards

Topic 7 Flashcards

1
Q

Define genotype

A

The genetic constitution of an organism

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2
Q

Define phenotype

A

The expression of the genes and its interaction with the environment

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3
Q

Define homozygous

A

A pair of homologous chromosomes carrying the same alleles for a single gene

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4
Q

Define heterozygous

A

A pair of homologous chromosomes carrying 2 different alleles for a single gene

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5
Q

Define a recessive allele

A

An allele only expressed if no dominant allele is present

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6
Q

Define dominant allele

A

An allele that will always be expressed in the phenotype

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7
Q

Define codominance

A

Both alleles are equally dominant and expressed in the phenotype

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8
Q

What is it called when you have more than 2 alleles for a single gene

A

Multiple alleles

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9
Q

Define sex linkage

A

A gene whose locus is located on the X chromosome

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10
Q

Define autosomal linkage

A

genes that are located on the same chromosome (Not sex chromosomes)

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11
Q

Define epistasis

A

When one gene modifies or masks the expression of a different gene at a different locus

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12
Q

Define monohybrid in terms of a genetic cross

A

A genetic cross of a characteristic determined by one gene

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13
Q

Define dihybrid

A

A genetic cross of a characteristic determined by two genes

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14
Q

Monohybrid inheritance genetic diagram coding and example

A

Single letter, capital or lower case

B or b

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15
Q

Codominant inheritance genetic diagram coding and example

A

Gene^allele
I^BI^A
C^RC^W

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16
Q

Multiple allele inheritance genetic diagram coding and example

A

Gene^allele
I^BI^O
I^AI^O

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17
Q

Sex linkage inheritance genetic diagram coding and example

A

Chromosome^allele
X^RX^r
X^RY

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18
Q

Autosomal linkage inheritance genetic diagram coding and example

A

Single letter, capital or lower case

Aa Bb

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19
Q

Epistasis inheritance genetic diagram coding and example

A

Single letter, capital or lower case

Ee Bb

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20
Q

What test would you use to compare the goodness of fit of observed phenotypic ratios with expected ratios

A

Chi squared test

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21
Q

Why is there a difference between observed and expected phenotypes of an organism’s autosomally linked alleles?

A

Crossing over occured during meiosis
Made new combinations of gametes

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22
Q

How to decide what statistical test is to be used

A

First decide if continuous data (measurements) was collected or if frequencies were (how many individuals are in a category) - if the latter, it’s a Chi squared test

If continuous data, are you:
- investigating an association between two measurements (Correlation Coefficient)
- investigating a difference between 2 means (Student T test)

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23
Q

What is a species

A

One or more populations that can breed together to produce fertile offspring

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24
Q

What is the Hardy Weinberg principle and what is it used for

A

p^2 + 2pq + q^2 = 1 where p+q=1
Predicting the allele frequencies within a population

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25
Q

Define gene pool

A

All the alleles of all the genes within a population at one time

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26
Q

Define population

A

All the individuals of one species in one area at one time that can potentially interbreed

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27
Q

Define allele frequency

A

The proportion of an allele within the gene pool

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28
Q

In the Hardy Weinberg equation, what is p, q , p^2, 2pq, and q^2

A

p= frequency of the dominant allelle
q= frequency of the recessive allele
p^2 = frequency of homozygous dominant genotype
2pq= frequency of heterozygous genotype
q^2= frequency of the homozygous recessive genotype

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29
Q

Why do individuals within a population of a species show a wide range of variation in phenotype?

A

Genetic and environmental factors

30
Q

What causes genetic variation in a population?

A

Mainly mutations
Meiosis and random fertilisation of gametes also introduces genetic variation
Random Assortment or Independent Segregation

31
Q

Summarise natural selection

A

Predation, disease and competition for means of survival result in differential survival and reproduction
Organisms with phenotypes providing selective advantages are likely to produce more offspring and pass on their favourable alleles to the next generation
This changes the allele frequencies within a gene pool

32
Q

3 Types of selection

A

Stabilising
Directional
Disruptive

33
Q

Explain disruptive selection

A

Individuals containing alleles coding for either extreme trait are more likely to survive and pass on their alleles
Allele frequency changes over time so more individuals have the allele for the extreme trait
Average trait allele becomes less frequent
Can ultimately lead to speciation

34
Q

Explain the speciation process

A

When one original population of a species becomes reproductively isolated so the 2 populations cannot breed to produce fertile offspring due to the accumulation of differences in their gene pools

35
Q

Explain allopatric speciation

A

Populations become separated georgaphically leading to reproductive isolation (by mountain ranges or new bodies of water separating land masses)
Both populations will continue to accumulate different beneficial mutations over time to help them survive in their environments which are likely to vary
They then become so genetically different they cannot interbreed to produce fertile offspring - 2 different species

36
Q

Explain sympatric speciation

A

Populations become reproductively isolated due to differences in their behaviour
Due to random mutation within the population impacting reproductive behaviour, eg causing individuals to perform a different courtship ritual or for individuals to be fertile at different times of the year
Due to this, there would be no gene flow between the two groups within the populations
Over time they accumulate different mutations to the extent that their DNA is so different they cannot interbreed to create fertile offspring - 2 different species

37
Q

What is genetic drift

A

The change in allele frequency within a population between generations

38
Q

Does all genetic drift cause evolution?

A

There will always be some between generations but continual, substantial genetic drift results in evolution

39
Q

Why does evolution occur more rapidly in smaller populations

A

The smaller the population, the bigger the impact allele frequency changes have proportionally and this is why evolution occurs more rapidly in smaller populations

40
Q

Define habitat

A

Part of an ecosystem in which particular organisms live

41
Q

Define community

A

All of the populations of different species in the same area at the same time

42
Q

Define ecosystem

A

A community and the non living components of an environment

43
Q

Define niche

A

An organisms role within an ecosystem including their position in the food web and habitat

44
Q

Define carrying capacity

A

The maximum population size an ecosystem can support

45
Q

Define abiotic factors

A

The non living conditions of an ecosystem

46
Q

Define biotic factors

A

Impacts of the interactions between organisms

47
Q

What can abiotic factors do within an ecosystem

A

Affect the size of different populations

48
Q

List some abiotic factors

A

Temperature
Oxygen and CO2 concentrations
Light intensity
pH
soil conditions

49
Q

The less harsh the abiotic factors…

A

…the larger the range of species and the larger the population sizes

50
Q

List some biotic factors

A

Inter/intraspecific competition
Predation

51
Q

Explain interspecific competition

A

Members of different species compete for the same limited resource (eg food, water, habitat)
The individual better adapted is more likely to succeed

52
Q

Explain intraspecific competition

A

Members of the same species are in competition for finite resources and a mate
Individuals with more energy for a more impressive ritual or fur/feathers may attract a mate easier

53
Q

How do predator prey graphs look?

A

Always more prey than predators, and both population sizes fluctuate

54
Q

What is lag time in predator prey graphs?

A

The time between the size of the population changing in prey, then predators

55
Q

Why sample instead of record an entire environment’s data?

A

More time efficient and accurate

56
Q

How to ensure samples accurately represent the population?

A

Random sampling in uniform areas to eliminate bias
Line transects to examine changes over a distance
Large number of samples (30>)

57
Q

How to sample a non-motile/slow moving organism with uniform distribution

A

Random sampling with a quadrat

58
Q

How to sample a non-motile/slow moving organism with an uneven distribution

A

Line transect with a quadrat

59
Q

How to sample motile organisms

A

Sample using mark-release-recapture method

60
Q

How to do random sampling in 3 steps

A
  1. Lie 2 tape measures at a right angle to create a gridded area
  2. Use a random number generator to generate 2 coordinates
  3. Place the quadrat and collect the data (density,freq,percentage cover)
61
Q

Types of transect?

A

Belt transect
Interrupted belt transect (uniform intervals down the tape measure)

62
Q

Line transect method in 4 steps

A
  1. Place the tape measure at a right angle to the shore line (or shade etc)
  2. Place the quadrat every 5 metres/every position on the line
  3. Collect the data (density, freq, percentage cover)
  4. Repeat by placing another 30+ transects along the beach at right angles to the shore line
63
Q

MRR method (6 steps)

A
  1. Initial sample of population is captures
  2. Individuals are then markes and the number caught is recorded (mark must be resistant to weather)
  3. Marked individuals released and are left for a period of time to allow them to randomly disperse throughout the habitat
  4. A 2nd sample is captured
  5. The total number captured in the 2nd sample and the number recaptured with markings are recorded
  6. Size of population is then estimated on the principle that the proportion marked in the 2nd sample equals the proportion of marked individuals in the population as a whole
64
Q

MRR calculation

A

estimated total population = (no. organisms initially caught x number of organisms in second sample)/number of marked organisms recaptured

65
Q

MRR ethics

A

Mark must

be non toxic
not increase chances of predation
not decrease chances of reproduction

66
Q

MRR assumptions

A

Population size is constant (no births, deaths or migration)
Animals always redistribute evenly (they all might huddle near food in reality…)

67
Q

Define succession

A

A change in an ecological community over time

68
Q

Primary succession steps

A
  1. When a pioneer species colonises bare rock or sand (Lichen, a pioneer species, are adapted to survive in harsh abiotic factors and through their decomposition, change abiotic factors to become less harsh and form a thin layer of soil, humus)
  2. Mosses and smaller plants can now survive and further increase the depth and nutrient content of soil
  3. The pattern continues - abiotic factors continue to become less harsh so larger plants can survive and change abiotic factors further
  4. This can result in an increase in biodiversity and species richness
  5. Each new species may change the environment in a way that it becomes less suitable for the previous species, so each existing species is outcompeted by a new species colonising
  6. Climax community is the final stage and is dominated by trees
69
Q

What is the difference between primary and secondary succession

A

Succession is disrupted (eg by a forest fire) and plants are destroyed
Succession starts again but the soil is already created, skipping the bare rock stage

70
Q

Why is the destruction of habitats bad

A

Loss of food and space for organisms, can lead to extinctions

71
Q

How are a greater variety of habitats conserved?

A

By maintaining earlier stages of succession and preventing a climax community, conserving more habitats and a greater number of species

72
Q

What is the example of a compromise between human needs and conservation in order to maintain sustainability of the resource?

A

Forests being coppiced to provide timber for fuel and furniture while still allowing the tree to survive

a-level bio (9 decks)

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