Genetics, populations, evolution and ecosystems 7 Flashcards
definition of phenotype
visible characteristics in an organism, determined by the genotype and its environment
definition of genotype
the genetic makeup of an organisms, by the combination of alleles found
definition of codominance
both alleles contribute to and are expressed in the phenotype
definition of multiple alleles
when a gene has more than two alleles
definition of a dominant allele
an allele that is always expressed in the phenotype of an organism
definition of recessive allele
an allele that is only visible in the phenotype in the presence of another identical allele
definition of homozygous
the alleles for a particular gene are identical
definition of heterozygous alleles
the alleles for a particular gene are different
definition of diploid
nucleus contains two sets of chromosomes (homologous pairs)
definition of haploid
the nucleus contains only one copy of each chromosome
what is dihybrid inheritance
inheritance of two characteristics, determined by two different genes on different chromosomes at the same time
how do we work out gamete combinations in dihybrid inheritance using an anagram
FOIL
F - first
O - outside
I - inside
L - last
what are the gamete genotypes of Round (R) Yellow (Y) seeds if the alleles for both yellow and round are dominant, as opposed to green (y) and shrivled (r). The gametes are heterozygous
Genotype: RrYy
gamete genotypes: RY, ry, Ry, rY
what are the chromosome representations for a boy
XY
what are the chromosome representations for a girl
XX
any gene that is on the X or Y chromosome is said to be ….
sex linked
if the parents phenotype is XX for female and XY for male, what are the gametes?
And what is the ratio of which offspring they will have
X or X and X or Y
1:1 ratio
what is a gene
a length of DNA that codes for a specific polypeptide
what is an allele
a part of the DNA base sequence that codes for the alternative form of a gene at a specific loci
A gene controlling coat colour in cats is sex linked. The two alleles of this gene are black and orange. When both are present the coat colour is called tortoise shell. Explain why there are no male tortoise cats
the gene is only on the X chromosome, and males cats only have one X
So male cats can only have one coat colour as only one out of the homologous pairs can code for a coat colour
and two coat colour alleles are needed for a tortoiseshell coat
what is meant by the term sex linked
traits or disorders that are influenced by the genes on a sex chromosomes
definition of population
a group of organisms of the same species in a particular place at a particular time and have the potential to interbreed
what is a gene pool
all the alleles of all the genes of all the individuals in a population at a given time
what is allelic frequency
the number of times an allele occurs within a gene pool
What is the Hardy-Weinberg equations we need to remember
p² + 2pq + q² = 1.0
p + q = 1.0
what are some assumptions we make when using the hardy-weinberg equation
- no mutations arise
- the population is isolated, so no immigration or emigration
- no allelic selection occurs, so both alleles are equally as likely to be passed onto the next generation
- large population is being sampled
- mating within the population is random and NOT controlled, so no interbreeding
what does p² stand for in the Hardy Weinberg equation
the percentage/proportion of homozygous dominant individuals
what does q² stand for in the Hardy Weinberg equation
the percentage/proportion of homozygous recessive individuals
what does 2pq stand for in the Hardy Weinberg equation
the percentage/proportion of heterozygous individuals
what does p stand for in the Hardy Weinberg equation
the frequency of dominant alleles in a population
what does q stand for in the Hardy Weinberg equation
the frequency of recessive alleles in a population
Cystic fibrosis is an autosomal recessive genetic disorder.
4 in 10,000 newborn babies in the United Kingdom have the disease.
Use the Hardy-Weinberg principle to estimate the percentage of UK newborns that are carriers for cystic fibrosis.
Give your answer to one decimal place.
In a population of 10,000 UK newborn babies, the expected proportion of babies having the disease is 4/10,000 = 0.0004 = q2.
The frequency of the allele that causes the disease (q) if the square root of this number, 0.0004 = 0.02.
You know that p + q = 1, therefore p = 1 – 0.02 = 0.98. Now, you can calculate the expected frequency of the three genotypes:
p2 (homozygous dominant; normal) = 0.9604
2pq (heterozygous; normal but carrier) = 0.0392
q2 (homozygous recessive; cystic fibrosis) = 0.0004
Therefore 3.9% of UK newborns are carriers of cystic fibrosis.
what do we use chi squared to find
whether there’s a difference between expected and observed result
if i have a null hypothesis for a t test, what do we say
that theres no statistically significant difference between results and that they are due to chance
if i have a alternative hypothesis for a t test, what do we say
that there is a significantly significant difference between results and that they are not due to chance
What is epistasis
when two genes (usually on different chromosomes) interact together to affect the phenotype. An allele of one gene may affect or mask the expression on another gene.
What needs to be done so using a quadrat is reliable and true and why
- quadrats are placed with no bias (computer chosen randomly)
- multiple samples taken so theres more reliability and its representative of more of the field
Why might a sample from a quadrat not be representative of the whole population?
- sampling bias
- chance
- sample size
how do you calculate the mean number of organisms per unit of size when using quadrats
total number of organisms / number of quadrats = mean number of organisms per unit of size
What are biotic factors
a factor that makes up part of an organism’s living environment (e.g. predators, disease, food availability)
What are abiotic factors
a factor that makes up part of an organism’s non living environment (e.g. light, pH, water)
Describe a spearmans rank graph
shows whether there is a correlation between recorded results and if there is, whether it is negative or positive
what is the p Value that we need to make sure our results are valid
5% or 0.05
what is a positive correlation
general trend upwards
what is a negative correlation
general trend downwards
what is no correlation
no trend in any direction
what are some genetic factors that can influence variation
random mutations
meiosis
random fertilisation of gametes
describe stabalising selection
the average phenotype of a population is favoured, and there selection against in the extreme phenotypes
describe directional selection
the phenotypes of a population change by favouring phenotypes that vary in one direction from the mean of the population, selecting for one extreme phenotype
describe disruptive selection
individuals with extreme phenotypes are favoured, over those with phenotypes around the mean of the population
what is speciation
the evolution of new species from existing ones
what is allopatric speciation
speciation that results from two populations becoming geographically isolated e.g. physical barriers
what is sympatric speciation
speciation that results within a population in the same area, but something is isolating them (no physical separation)
outline allopatric speciation
Geographical isolation of populations (so this is an example of allopatric speciation)
Therefore there was reproductive separation/isolation between these two populations because no interbreeding could take place
There is variation in each population due to random mutations (and genetic drift)
Different environmental conditions in the different locations lead to different selective pressures
Advantageous alleles in each population are selected for by natural selection (these individuals survive, reproduce and pass on their alleles) changing the frequency of alleles in the different populations
Eventually each population may change so much that they can no longer interbreed between the populations to produce fertile offspring so have become different species
Outline sympatric speciation
Speciation in the Anoles occurred by:
There is variation in the population of anoles due to random mutations (eg. causing different leg length, toe pad size, dulap colour etc)
The anoles are not geographically isolated as they are found in the same environment (so this is an example of sympatric speciation)
A species living in the same area compete for limited resources, so members of the species move into different habitats in the same area to access and use resources not available to the others
Therefore becoming reproductively separated/isolated
Different environmental conditions in the different locations lead to different selective pressures
Different advantageous alleles in each population are selected for by natural selection (the individuals better adapted survive, reproduce and pass on their alleles) changing the frequency of alleles in the different populations
Eventually each population may change so much (different coloured dulaps - behavioural isolation) that they can no longer interbreed between the populations so have become different species
what are some assumptions made during marking and recapturing
that the motile organisms have had enough time to redistribute
there’s no emigration or immigration
the markings haven’t come off
what is a population (2)
groups of organisms of the same species living in the same area at the same time that can interbreed to make fertile offspring
what is a habitat
part of an ecosystem in which particular organisms live
what is a community
all the populations of different species are in the same area at the same time
what is an ecosystem
a community and the nonliving components of an environment. Ecosystems can range in size from very small to very large
what is a niche
an organisms role within an ecosystem, including its position in the food web and habitat. Each species occupies its own niche governed by adaptation to both abiotic and biotic factors
what is carrying capacity
the maximum population size an ecosystem can support
abiotic factors definition
non-living conditions of an ecosystem
biotic factors definition
impacts of interactions between organisms
abiotic factors that affect population size
temperature, light, pH
intraspecific competition meaning
occurs when individuals of the same species compete for resources
interspecific competition meaning
occurs when individuals of different species compete for resources
what causes interspecific competition
one species competing against another, usually where one has a competitive advantage over the other, causing it to increase in size and the other to diminish
what causes intraspecific competition
competition within a species, where the availability of a resource usually determines the size of that population
What is predation
the preying of one animal on others
Describe and explain how succession is reached
Pioneer species colonise the barren land.
There is a change in competition for abiotic factors.
Increases stability and makes the environment less hostile.
More and more species start to grow and colonise space.
Biodiversity increases
Climax community is reached
what kind of succession can there be
primary and secondary
what is conservation
the method of maintaining ecosystems and the living organisms that occupy them, by human intervention.
what are the reasons for conservation
personal - to maintain out planet
ethical - other species occupied Earth far longer than us
economic - living organisms have a huge pool of genes with the capability to make millions of substances which may be valuable to us in the future
cultural and aesthetics - habitats and organisms enrich our lives
