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AQA A-Level Biology > Genetics and Populations > Flashcards

Genetics and Populations Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

abiotic factors

A

The non-living aspects of an ecosystem e.g. temperature, light intensity, moisture, soil pH and oxygen levels.

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2
Q

adaptation

A

a feature of an organism that increases its chance of survival in its environment.

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3
Q

allele

A

a version of a gene

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4
Q

allele frequency

A

The number of times an allele appears within a population’s gene pool.

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5
Q

allopatric speciation

A

A form of speciation that occurs when two populations become geographically isolated.

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6
Q

autosomal linkage

A

​When two or more genes are positioned on the same autosome. They are unlikely to be separated by crossing over during meiosis so are often inherited together.

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7
Q

autosome

A

a chromosome that is not an X or Y chromosome

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8
Q

belt transect

A

A line along a sampled area, upon which quadrats are placed at certain
intervals to determine the abundance and distribution of organisms in an ecosystem.

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9
Q

biodiversity

A

​The variety of genes, species and habitats within a particular area.

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10
Q

biotic factors

A

The living components of an ecosystem e.g. food availability, pathogens and predators.

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11
Q

carrying capacity

A

The average size of a population that can be supported by an ecosystem over extended periods of time. This varies depending on biotic and abiotic factors.

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12
Q

chi-squared test

A

A statistical test used to determine whether a pattern of inheritance is statistically significant.

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13
Q

climax community

A

The stable community of organisms that exists at the final stage of ecological succession.

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14
Q

codominant

A

when both alleles for a gene in heterozygous organisms equally contribute to the phenotype

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15
Q

community

A

all of the populations of different species living together in a habitat

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16
Q

conservation

A

The​ ​maintenance of ecosystems and biodiversity by humans in order to preserve the Earth’s resources. This typically involves the management of succession.

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17
Q

degrees of freedom

A

the number of categories minus one

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18
Q

dihybrid inheritance

A

​The inheritance of two different genes, that determine two
phenotypes, on two different chromosomes.

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19
Q

diploid

A

​Describes a cell with a nucleus containing two sets of chromosomes.

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20
Q

directional selection

A

A type of selection that favours one extreme phenotype and selects against all other phenotypes.

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21
Q

disruptive selection

A

A type of selection that favours individuals with extreme phenotypes and selects against those with phenotypes close to the mean.

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22
Q

dominant

A

Describes an allele that is always expressed. Represented by a capital letter.

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23
Q

ecosystem

A

​The community of organisms (biotic) and non-living (abiotic) components of an
area and their interactions. It is a dynamic system.

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24
Q

epistasis

A

​Describes a relationship between genes where the allele of one gene affects the expression of a different gene.

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25
Q

evolution

A

The gradual change in the allele frequencies within a population over time. Occurs due to natural selection.

26
Q

gene

A

A length of DNA on a chromosome that codes for the production of one or more polypeptide chains and functional RNA.

27
Q

gene pool

A

All of the different versions of genes (alleles) in the individuals that make up a population.

28
Q

genetic drift

A

variations in allele frequencies in small populations due to chance

29
Q

genetic variation

A

Differences in genotypes between members of a population which may
occur due to mutations, meiosis, or random fertilisation.

30
Q

genotype

A

an organism’s genetic composition (describes all alleles)

31
Q

habitat

A

the region where an organism normally lives

32
Q

hardy-weinberg principle

A

​A model that predicts that the ratio of dominant and recessive alleles in a population will remain constant between generations if the following five conditions are met: no new mutations; no natural selection; no migration; large population; and random mating. It provides an equation for calculating the frequencies of alleles:
p2​ ​ + 2pq + q2​ ​ = 1.0
where p is the frequency of the dominant allele, and q is the frequency of the recessive allele.

33
Q

heterozygous

A

​When someone has two different alleles of a gene e.g. Ff.

34
Q

homozygous

A

​When someone has two identical alleles of a gene e.g. ff.

35
Q

interspecific competition

A

A type of competition that takes place between members of different species.

36
Q

intraspecific competition

A

A type of competition that takes place between members of the same species.

37
Q

locus

A

the position of a gene on a chromosome

38
Q

mark-release-recapture

A

A method of estimating the population size of motile organisms. It involves capturing a sample of the population, marking them and releasing them. At a later date, another sample is captured and the number of marked individuals recorded.

39
Q

monohybrid inheritance

A

the inheritance of one gene

40
Q

multiple alleles

A

when a gene has more than two potential alleles

41
Q

natural selection

A

​The process by which the frequency of beneficial alleles gradually increases in a population’s gene pool over time. This theory was developed by Charles Darwin.

42
Q

niche

A

Describes how an organism ‘fits’ into an ecosystem and its role in that environment.

43
Q

phenotype

A

An organism’s observable characteristics. Due to interactions of the genotype
and the environment.

44
Q

pioneer species

A

Species that can survive in hostile environments and colonise bare rock or sand e.g. lichens.

45
Q

population

A

All organisms of the same species living with one another in a habitat at the same time.

46
Q

predator

A

an organism that eats other organisms

47
Q

prey

A

an organism that is eaten by predators

48
Q

quadrat

A

A square grid of a known area used in sampling to determine the abundance of organisms in a habitat. There are two types: point quadrats and frame quadrats.

49
Q

random sampling

A

​A sampling technique used to avoid bias e.g. creating a square grid and generating random coordinates.

50
Q

recessive

A

​Describes an allele that is only expressed in the absence of a dominant allele. Represented by a small letter.

51
Q

selection pressures

A

Environmental factors that drive evolution by natural selection and limit population sizes e.g. competition, predation and disease.

52
Q

sex-linkage

A

the presence of a gene on an X or Y chromosome

53
Q

speciation

A

The formation of new species due to the evolution of two reproductively
separated populations. Two forms: allopatric and sympatric speciation.

54
Q

species

A

A group of similar organisms that are able to breed with one another to produce living, fertile offspring.

55
Q

stabilising selection

A

A type of selection that favours individuals with phenotypes close to the mean (average) and selects against extreme phenotypes.

56
Q

succession

A

​Describes changes in the community of organisms occupying a certain area over time.

57
Q

sustainable

A

the ability to maintain something for future generations

58
Q

sympatric speciation

A

​A form of speciation that occurs when two populations within the
same area become reproductively isolated.

59
Q

systematic sampling

A

A sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals e.g. along a belt transect. This is commonly used in ecosystems where some form of gradual change occurs.

60
Q

variation

A

the differences between individuals due to genes, the environment, or a combination of both

AQA A-Level Biology (8 decks)

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