A2 Genetics, populations, evolution and ecosystems

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68 Terms

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Codominant definition

Both alleles equally dominant and expressed in the phenotype

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multiple alleles definition

More than 2 alleles for a gene

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sex linkage definition

A gene whose locus is on the X chromosome

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what is incomplete dominance?

- 1 allele codes for enzyme that catalyses formation of pigment

- other allele codes for other enzyme which lacks this activity so does not produce pigment

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example of sex linkage

Haemophilia

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what is monohybrid inheritance

The inheritance of a single gene

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what does dihybrid mean

the inheritance of 2 different genes

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what is the ration in dihybrid crosses

9:3:3:1

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what is epistasis?

how the expression of one gene affects the phenotypic expression of another gene

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example of epistasis

in mice and other mammals, coat color depends on two genes, one gene determines the pigment color (with alleles B for black and b for brown), the other gene (with alleles C for color and c for no color) determines whether the pigment will be deposited in the hair

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what is autosomal linkage

2 Genes (characteristics) carried on the same Chromosome

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why do results of genetic crossed often differ from predicted results

- random fertilisation

- independent assortment

- crossing over

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how is the chi-squared test used

determines statistical difference between observed and expected frequencies

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genotype definition

genetic makeup of an organism

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phenotype definition

the expression of the genotype

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how is sex determined genetically

Y chromosome

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why are pedigree diagrams useful?

see inheritance of traits over many generations

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what test do we use to compare the goodness of fit of observed phenotypic ratios with expected ratios.

chi squared

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definition of autosomal linkage

two genes carried on same autosome

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species exist as ___ or ____ populations

one or more

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define population

a group of organisms of the same species in the same place at the same time and can interbreed

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define gene pool

the range of alleles in a population

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define allele frequency

how often an allele occurs in a population

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What are the Hardy-Weinberg equations?

p+q=1

p^2+2pq+q^2=1

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what are the conditions for the Hardy-Weinberg principle?

- no mutations arising

- large population

- no natural selection

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what is p in Hardy-Weinberg

dominant allele

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what is q in Hardy-Weinberg

recessive allele

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what is p^2 in Hardy-Weinberg

homozygous dominant genotype

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what is q^2 in Hardy-Weinberg

homozygous recessive genotype

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what is 2pq in Hardy-Weinberg

heterozygous genotype

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how do genetic factors lead to variation

mutations which change base sequence of amino acids

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how does meiosis lead to variation

crossing over, independent assortment, random fertilisation

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what are some examples of environmental factors leading to variation

climate, food, lifestyle

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define evolution

the change in allele frequency in a population over time

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describe natural selection in simple steps

- mutations create variation

- selection pressure e.g. competition

- organisms with favourable allele survives and reproduces, passing on allele to next generation

- allele frequency in gene pool change over many generations

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define speciation

Formation of new species

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when does allopatric speciation occur

geographically isolated

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Describe allopatric speciation

- mutations create variation

- selection pressures

- favourable alleles survive and reproduce to pass allele to offspring

- leads to change in allele frequency

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when does sympatric speciation occur

not geographically isolated

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describe sympatric speciation

- mutations create variation

- causes individuals to become reproductively isolated

- temporal, behavioural and mechanical

different selection pressures operate

- leads to change in allele frequency

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define the temporal mechanism

different mating seasons

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define the behavioural mechanism

different courtship behaviour preventing mating

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define the mechanical mechanism

incompatible genitalia

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define genetic drift

change in allele frequency in a population due to chance

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where does genetic drift have the strongest effect

in small populations

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what is a genetic factor in evolution?

mutations

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how does meiosis affect variation in phenotype?

- crossing over between homologous chromosomes

- independent segregation

- random fertilisation of gametes

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define evolution

the change in allele frequency in a population over time

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what causes variation in a population ?

mutations

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define community

The populations of different species living in a habitat

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define biotic factor

A living component of an ecosystem

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define abiotic factor

non-living component of an ecosystem

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define carrying capacity

max stable population size of a species that an ecosystem can support

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define population

group of same species living in same place at same time

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define ecological niche

the role it plays within the community

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define niche competition

between 2 species when niche overlap

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define ecosystem

a community and non living components of its environment

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define ecology

the study of how organisms interact with one another and with their physical environment

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the population size of a species can vary as a result of...

- abiotic factors

- interactions between organisms

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What is intraspecific competition?

competition within a species

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intraspecific competition is _______ dependent because more individuals means less _________

density, resources

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What is interspecific competition?

competition between different species (occupying similar niches)

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what is a predator prey example?

lynx and hare, rabbit and fox

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what is succession?

the gradual change in the species that make up a community over time

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what is a pioneer species?

first species to colonise and area (e.g. lichens)

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what is primary succession?

plants grow where no plants have grown before

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what is secondary succession?

plants grow where there has been a previous population

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what happens when plants decompose?

provide the soil with nutrients