Genetics, populations, evolutions and ecosystems

Define genotype

All of the alleles that an organism carries on its chromosomes

define phenotype

Observable characteristics of an organism which the result of the genotype as well as environmental factors

What is monohybrid inheritance

When a phenotype or trait is controlled by a single gene

What is dihybrid inheritance

When two characteristics are studied and is determined by two different genes that are present in two different chromosomes at the same time

What is codominance

When two phenotypes are expressed such as when birds have feathers that are both black and white

What is sex linkage

The expression of an allele dependent on the gender of the individual as the gene is located on a sex chromosome

What’s XY

Male

What’s XX

Female

What is autosomal linkage

Two or more genes are on the same autosomal chromosome

What is epistasis

The interaction of different loci on the gene, one gene locus affects the other gene locus

What are the criteria’s for the chai squared test

-The sample size must be sufficiently large enough, that is over 20

-Used only for data that falls into discrete categories

-Only raw counts and not percentages, rates etc can be used

Define population

A group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed

Define gene pool

The total number of alleles that are present in a population

What’s the hardy Weinberg equation used for

Used to estimate the frequency of alleles in a population

What are the 5 needs for the hardy Weinberg equation

1.) no mutations occur to create new alleles

2.) there is no movement of alleles into or out of the population by migration

3.) the population is large

4.)there is no selection so every allele has an equal chance of being passed to the next gen

5.) mating is random

What are the 2 equations for hardy Weinberg

P + Q = 1

P2 + 2PQ + Q2 = 1

What does P stand for in the hardy Weinberg equation

The frequency of the dominant allele

What does q stand for in the hardy Weinberg equation

The frequency of the recessive allele

What are the 3 reasons for variation in alleles of genes for members of the same species

1.) random fertilisation (the gametes that are carrying different alleles will join together randomly)

2.) meiosis (the sorting of the gametes are random)

3.) mutation (the mutation of an allele can go on to lead to the creation of another new allele)

What is the niche of a species

It’s role in the environment

What do species that share the same niche do

Compete with each-other and a better adapted species will survive

What is the basis of natural selection

The idea that better adapted species survive

What is the reason many organisms have unsustainably large numbers of offspring’s

There is greater competition within the species (intraspecific competition) and therefore only those that have the alleles best suited to the environment survive long enough to grow and reproduce passing the alleles on to the next gen

What does the variation in genotypes and phenotypes do

Increases the chance than a species will survive in a habitat that is changing

What’s the process of evolution via natural selection

-There’s a variety of phenotypes within a population

-An environmental change occurs and as a result of that the selection pressure changes

-Some individuals possess advantageous alleles which give them a selective advantage and allow them to survive and reproduce

-The advantageous alleles are passed on to their offspring

-Over time the frequency of alleles in a population changes and this lead to evolution

Define selection

The process by which individuals that are better adapted to their environment are more likely to survive and breed

Define directional selection

Occurs when the environmental conditions change and the phenotypes best suited to the new conditions are more likely to survive. Therefore the population will start to move in the direction of these individuals

Define stabilising selection

In stabilising selection the phenotypes with successful characteristics are preserved and those of greater diversity are reduced. So the individuals closest to the mean are favoured because they have the alleles that have given them the survival advantage (the furthest from the mean are selected against)

Define disruptive selection

This is the opposite of stabilising selection and in this case both extremes of the normal distribution are favoured over the mean

Define speciation

The process by which new species arise after a population becomes separated and cannot interbreed

What is allopatric speciation caused by

A physical barrier

What is sympatric speciation

Where a new species evolves from a single ancestral species

Define ecosystem

Includes all the organisms living in a particular area known as the community

What does biotic mean

Living

What does abiotic mean

Non living

What are 4 biopics factors that can affect the growth rate of a population

1. Temperature

2. Light

3. pH

4. Water and humidity

What’s intraspecific competition

When members of the same species compete

What factors affect intraspeciifc competition

-food

-water

-mates

-shelter

-minerals

-light

What’s interspecific competition

When members of different species compete for the same resources

What is predation

When one species (the prey) is caught and eaten by another species (the predator)

What is a predator-prey relationship

When the populations of the predators and prey affect each other

How does predation occur

1. When the prey is eaten by the predator the population of the prey falls

2. This results in the predator population growing however means that more prey is consumed

3. Therefore the population of prey reduces and there is increased competition for the prey between the predators

4. The lack of food for the predators means that the population falls meaning that less prey is eaten

5. This allows the population of the prey to recover and therefore the cycle occurs over in a oscillating manner

How can the size of a population be estimated randomly

Using a quadrat

What are 2 main ways the abundance of different species can be measured

1. Percentage cover

2. Frequency

What’s the process of mark-release-recapture and when is it used

For fast moving animals

1. Known number of species is captured and marked in a way that doesn’t reduce their chance of survival

2. Theses marked organisms are then released again into the same area they were caught

3. After a suitable length of time another known number of organisms are captured, with the number of these that are marked are being recorded

What’s the equation for the estimated population size

Estimated population size = (total number of individuals in the first sample x total number of individuals in the second sample) / number of marked individuals recaptured

What assumptions does the mark-release-recapture method rely on

1. The proportion of marked to unmarked individuals in the second sample is the same as the proportion of marked to unmarked individuals in the population as a whole

2. The marked individuals released from the first sample distribute evenly amongst the remainder of the population and have sufficient time to do so

3. There is a definite boundary to the population so there is no immigration into or emigration out of the population

4. There are a few if any births and deaths within the population

5. The method of making is not toxic and does not reduce the chance of survival for the population

6. The mark of labels do not run off during the investigation

Define succession

The change of one community of organisms into another

When does primary succession occur

When the area previously devoid of life is colonised by communities of organisms

When does secondary succession occur

In a previously colonised area in which an existing community has been cleared

What is conservation

The human management of the earths resources