Genetics, population, evolution & ecosystems Flashcards
(74 cards)
1
Q
genotype
A
the genetic constitution of an organism
2
Q
phenotype
A
the observable or biochemical characteristics of an organism due to the genotype and the environment
3
Q
homozygous
A
a pair of homologous chromosomes carrying the same alleles for a single gene
4
Q
heterozygous
A
a pair of homologous chromosomes carrying two different alleles for a single gene
5
Q
recessive allele
A
an allele that is only expressed in the absence of a dominant allele
6
Q
dominant allele
A
an allele that is always expressed in the phenotype
7
Q
codominant
A
both alleles are equally dominant and are both expressed in the phenotype
8
Q
multiple alleles
A
more than two alleles for a single gene
9
Q
sex linkage
A
a gene whose locus is on the X chromosome
10
Q
autosomal linkage
A
genes that are located on the same chromosome (not the sex chromosomes)
11
Q
epistasis
A
when one gene modifies or masks the expression of a different gene at a different locus
12
Q
monohybrid
A
genetic inheritance cross of a characteristic determined by one gene
13
Q
dihybrid
A
genetic inheritance cross for a characteristic determined by two genes
14
Q
what must be included in a genetic diagram
A
parent genotypesparent phenotypesgametesPunnett square (technically optional)offspring genotypeoffspring phenotypethe probability/ratio of offsprings have a condition/feature
15
Q
phenotype ratio for a dihybrid cross of two heterozygous parents
A
9:3:3:1
16
Q
why might you not get the expected ratio
A
if there is autosomal linkage or crossing over in meiosis
17
Q
population
A
group of the same species in the same habitat at the same time
18
Q
gene pool
A
all the alleles for all the genes for a population at one time
19
Q
allele frequency
A
the proportion of each allele within the gene pool
20
Q
gene
A
sequence of nucleotide bases that code for the amino acid sequence of a polypeptide or a sequence of bases that code for a function RNA like rRNA or tRNA
21
Q
allele
A
a version of a gene
22
Q
locus
A
the position of a gene on a chromosome
23
Q
diploid
A
have two copies of each allele
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haploid
A
have one copy of each allele
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homologous chromosomes
chromosomes with the same genes at the same loci, but they may be different alleles
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carriers
those who carry an allele that is not expressed in the phenotype but can be passed onto offsprinf
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heterogametic
two different sex chromosomes
e.g. male humans XY
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homogametic
two of the same sex chromosome
e.g. female humans XX
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epistatic gene
a gene that masks the expression of another gene when expressed
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hypostatic gene
gene that is masked by the expression of another gene
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phenotypic ratio for heterozygous monohybrid inheritance
0.12569444444444455
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phenotypic ratio for heterozygous codominant inheritance
0.043067129629629664
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phenotypic ratio for dominant epistasis
12:3:1 or 13:3
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phenotypic ratio for recessive epistasis
0.3771296296296296
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phenotypic ratio for complementary epistasis
0.3798611111111112
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dominant epistasis
dominant allele A masks the expression of B, A is the epistatic gene of B
B is only expressed when aa is present so it is called dominant epistasis
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recessive epistasis
recessive allels aa masked the phenotypic expression of other gene locus (BB, Bb, or bb)
the allele of B express themselves only when A has a dominant allele, AA or Aa
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complementary epistasis
both gene loci have homozygous recessive alleles and both of them produce identical phenotype
aaBB, aaBb, AAbb, Aabb, and aabb produce the same phenotype
39
what can cause a difference between observed vs expected results
small sample sizerandom fusion/fertilisation of gameteslinked genes (crossing over or sex linkage)epistasislethal genotypes
40
what is the Hardy Weinberg equation
p2 + 2pq + q2 = 1
p + q = 1
p = frequency of dominant allele
q = frequency of recessive allele
p2 = frequency of homozygous dominant genotype
q2 = frequency of homozygous recessive genotype
2pq = frequency of heterozygous genotype
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why does the Hardy Weinberg principle state
allele frequencies will remain constant from one generation to the next
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what does the Hardy Weinberg principle assume
there is a large population sizemating is random within the populationthere is no mutationthere is no migrationno genotype has a selective advantage there is no genetic drift
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what acts as selection pressures for natural selection
competition for resources
disease
predation
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sources of genetic variation
mutation
meiosis
random fusion of gametes
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species
organisms with similar characteristics that can breed to produce fertile offspring
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why is genetic diversity important
greater genetic diversity
means more alleles in a gene pool
means greater variety of phenotypes in a population
means it's more likely that some members of the population would survive an environmental change
this enables natural selection
47
general process for natural selection
genetic variation in a population and random mutations may create new alleles
some allele/mutations have advantageous effects due to a selection pressure
individuals with these characteristics have increased reproductive success, therefore the allele is more likely to be passed on to next generation
frequency of advantageous allele increases
48
disruptive selection
when individuals which contain the alleles coding for either extreme trait are more likely to survive and pass on their alleles
the allele frequency changes to be greater for the extreme traits and the middling trait becomes less frequent
this can eventually lead to speciation
e.g. beak size of birds on the Galápagos Islands
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stabilising selection
the mean is favoured/against the extremes
range of alleles decreases
e.g. human birth weight
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directional selection
selection pressure means one extreme is advantageous
e.g. antibiotic resistance
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when does speciation occur
when the original population is reproductivly isolated so there is no gene flow between the two populations
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mechanisms of reproductive isolation
different eating times
geographical barriers
have different courtship behaviours
mechanically incompatible features
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general process of allopatric speciation
populations are geographically separated and so reproductively isolated - no gene flow between populations
within the separate gene pools there is genetic variation due to mutation (and sexual reproduction)
in different environments there are different selection pressures
there is differential reproductive success - natural selection occurs in each population
over time the allele frequency changes
eventually different species are formed that cannot interbreed to produce fertile offspring
54
general process of sympatric speciation
populations are within the same habitat but become reproductively isolated
there are separate gene pools
in each population, different alleles are passed on
natural selection occurs
over time, the allele frequency changes
eventually different species are formed that cannot interbreed to produce fertile offspring
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genetic drift
change in allele frequency between generations
continual, substantial genetic drift results in evolution
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why does evolution occur more rapidly in smaller populations
the smaller a population, the bigger the impact allele frequency changes have proportionally
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habitat
part of an ecosystem in which particular organisms live
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community
all the populations of different species in the same area at the same time
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ecosystem
a community and the non-living components of an envrionment
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niche
an organisms role within an ecosystem, including their position in the food web and their habitat
each species occupies their own niche governed by adaptation to both biotic and abiotic factord
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carrying capacity
the max population size an ecosystem can support
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abiotic factors
nn living conditions of an ecosystem
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biotic factors
impact of the interactions between organisms
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examples of abiotic factors
temperature, oxygen and CO2 conc, light intensity, pH, soil conditions
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interspecific competition
members of different species are in competition for the same limited resource e.g. habitat/food/water
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intraspecific competition
members of the same species are in competition for resources and a mate
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sampling non moving organisms with uniform distribution
quadrat and random sampling
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sampling non moving organisms with uneven distribution
using a quadrat and line transect
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mark release recapture to estimate population size of motile organisms
initial sample of the population is capturedthese individuals are marked in a way that is non toxic, weather resistant, and doesn't impact reproduction or predationthe marked individuals are released and left to randomly disperse throughout the habitatsecond sample is capturedtotal number captured in second sample and number recaptured with markings is recordedestimated total population = (no. organisms originally caught x no. organisms in second sample)/no. marked organisms recaptured
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wha does mark release recapture assume
no migrationno births/deathsmarking is permanent and doesn't impact survivalmarked individuals have randomly mixed marked individuals have had sufficient time to disperse
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primary succession
pioneer species such as lichen colonise bare rock/sand
the pioneer species are adapted to survive harsh abiotic factors
there death and decomposition change the abiotic factors to become less harsh and from a thin layer of soil called humus
moss and smaller plants can then survive and they further increase the depth and nutrient content of the soil
this pattern continues, with abiotic factors continuing to be less harsh, larger plants surviving, and the environment being further changes
each new species may change the environment in a way that makes it less suitable for the previous species, so each existing species is outcompeted
the final stage in a succession is known as the climax community - this is dominated by trees
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how is secondary succession different from primary
there is disruption and plants are destroyed]sucession starts again but soil is already created so it does not start from the bare rock sera stage
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how do food webs become more complex in succession
the species richness and number of organisms increase (biodiversity increases)
larger plant species and animals can colonise the area
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how can managing succession conserve habitats
y maintaining earlier stages in succession and preventing a climax community, a greater variety of habitats are conserved, and so a greater range of species
