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A-level Biology > genetics, populations, evolution and ecosystems > Flashcards

genetics, populations, evolution and ecosystems Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Genotype

A

the genetic constitution of an organism

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2
Q

Phenotype

A

the expression of the genetic constitution
and its interaction with the environment

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2
Q

Homozygous

A

two copies of the same allele for a gene

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2
Q

Recessive allele

A

An allele that is only expressed if there are no dominant alleles present

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3
Q

Dominant allele

A

An allele that is always expressed in the phenotype

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3
Q

Codominance

A

two alleles are both dominant both are expressed in the phenotype

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3
Q

Heterozygous

A

two different alleles for the same gene

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3
Q

Sex-linkage

A

a gene located on the X chromosome
in the non-homologous region

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4
Q

Multiple alleles

A

More than two alleles for a gene

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5
Q

Autosomal linkage

A

genes located on the same chromosome (not the X or Y chromosome)

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6
Q

Epistasis

A

When one gene masks/modifies with the expression of another gene

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7
Q

Dihybrid

A

The inheritance of two genes

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7
Q

Monohybrid

A

The inheritance of one gene

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8
Q

Natural selection

A

the process that leads to evolution in populations results in species becoming better adapted to their environment

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9
Q

Selection pressure

A

factors that affect the survival of an organism
the driving force of natural selection

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10
Q

Differential reproductive success

A

not all individuals are equally
likely to reproduce
results in changes in allele frequencies within a gene pool

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11
Q

Allele frequency

A

The proportion of an allele in the population

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12
Q

Disruptive selection

A

Individuals with either extreme trait are more likely to survive and pass on their alleles
the middling trait allele becomes less frequent
leads to speciation

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13
Q

Reproductively isolated

A

Two populations of the same species, but they cannot breed together
there is no gene flow

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14
Q

Speciation

A

the process that results in the
creation of new species

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15
Q

Allopatric speciation

A

Two populations become reproductively isolated due to being geographically separated
results in the formation of two new species

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16
Q

Sympatric speciation

A

Two populations become reproductively isolated whilst in the same location
e.g. due to changes in behaviour results in the formation of two new species

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17
Q

Genetic drift

A

the change in the allele frequency within a population between generations
occurs from one generation to the next substantial genetic drift results in evolution

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18
Q

Population

A

All the individuals of one species in the same area at the same time

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19
Q

Habitat

A

The range of physical, biological and environmental factors in which a species can live

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20
Q

Community

A

all the species in a particular area at a particular time

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21
Q

Ecosystem

A

a community and the non-living components of an area
they can range from very small to very large in size

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22
Q

Carrying capacity

A

The maximum population size an ecosystem can support

23
Q

Niche

A

An organism’s role within an ecosystem
their position in the food web and their habitat

24
Q

Biotic factors

A

Impact and interactions between organisms

24
Q

Abiotic factors

A

Non-living conditions of an ecosystem

25
Q

Interspecific competition

A

Competition between members of different species

26
Q

Intraspecific competition

A

Competition between members of the same species

27
Q

Predator-prey relationship

A

the interaction between predator and prey and how this affects their population sizes

28
Q

When would you use random
sampling?

A

when there is a uniform distribution of the plant species to avoid bias

29
Q

Quadrat

A

a frame
gridded or opened
used to sample non-motile organisms

30
Q

What must you do to ensure your samples are representative?

A

Take a large sample (at least 30)
randomly sample

31
Q

When would you use a line transect

A

When sampling a non-uniform area
e.g. a rocky shore

32
Q

Belt transect

A

one tape measure is placed through an ecosystem that is not uniform
the quadrat is placed at every position along a tape measure

33
Q

Interrupted belt transect

A

one tape measure is placed through an ecosystem that is not uniform
the quadrat is placed at set intervals along the tape measure

34
Q

The 3 measurements you can take when counting plants in a quadrat?

A

density
percentage cover
frequency

35
Q

Density measurement

A

when you count the individuals present

36
Q

Frequency measurement

A

count how many squares out of the 100 contain the species you are investigating

37
Q

Percentage cover measurement

A

investigator estimates the percentage of the entire quadrat covered with the species that is being investigated
standardise by counting 1% for every small square that is at least half covered by the plant

38
Q

When would you use mark-release- recapture?

A

Estimate the population size of
motile organisms

39
Q

What is a succession?

A

the change in an ecological community over time

40
Q

What is a primary
succession

A

a succession with a pioneer species colonising bare rock or sand
the first time the land is colonised

41
Q

What is a secondary succession?

A

there is a disruption that causes plants to be destroyed succession starts again, but the soil is already formed

42
Q

Pioneer species

A

The first species to colonise an area
e.g. lichen

42
Q

Climax community

A

The final seral stage in succession
the most stable stage

42
Q

Humus

A

A thin layer of soil that forms in early primary succession

43
Q

Conservation of habitats

A

Protecting habitats as a means to protect species
maintains habitats and food sources

43
Q

Hardy-Weinberg principle

A

a mathematical model used to
predict the allele frequencies
within a population

p2 + 2pq + q2 = 1

44
Q

What is the advantage of
managing succession?

A

Conserves a range of habitats and a range of food sources
enabling a wider range of species to survive

45
Q

Assumptions of the Hardy-Weinberg principle

A

There will be no change in the allele frequency between generations within a population e.g. no deaths, births or migration

46
Q

Assumptions of mark-release- recapture

A

the marked individuals released distribute evenly after being released
no migration
no births or deaths

47
Q

What creates genetic variation?

A

mutations
crossing over in meiosis independent segregation in meiosis
random fertilisation of gametes

48
Q

Selective advantage

A

Individuals with alleles that make them more likely to survive in that environment

49
Q

Effects of stabilising selection

A

the middle (median) trait has a selective advantage and continues to be the most frequent in the population range decreases as the extreme traits are lost over time

50
Q

Effects of directional selection

A

one of the extreme traits has a selective advantage
occurs when there is a change in the environment
the modal trait changes

51
Q

Evolution

A

a change in allele frequencies in populations
over many generations

51
Q

Effects of disruptive selection

A

alleles for the extreme traits and the middling trait allele become less frequent
leads to speciation

52
Q

Why is genetic drift important in small populations?

A

the impact of allele frequency changes has a bigger impact
proportionally
results in evolution occurring more rapidly

53
Q

How would you randomly sample?

A

place two tape measures at right angles to create a gridded area
use a random number generator to get coordinates
place the quadrate at the coordinates and collect the data repeat at least 30 times

54
Q

How would you sample using a line transect?

A

Place a tape measure at a right angle to the road/river/shoreline
place quadrat every set distance meters (e.g. 5 metres) collect the data in each quadrat repeat placing the tape measure in parallel 30 times

55
Q

What is the formula to calculate population size with mark-release- recapture?

A

number of marked organisms recaptured

56
Q

Describe the mark- release-recapture method of sampling

A

an initial sample of the population is captured individuals are marked and released
allow them time to randomly
disperse
a second sample is captured the total number captured in the second sample and the number recaptured with the marking are recorded

57
Q

Describe the changes you would see in a succession

A

Abiotic factors become less hostile
biodiversity increases
becomes more stable

A-level Biology (8 decks)

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