Genetics, Population, Evolution and Ecosystems

What does genotype mean?

The genotypes is all of the alleles that an organism carries on its chromosomes

What does phenotype mean?

The phenotype is the observable characteristics of an organism which is the result of the genotype as well as environmental factors

What is an allele?

An allele is an alternative form of a gene

What is the locus?

The locus is the specific position of the gene on the chromosome

What does being diploid mean for organisms?

Being diploid means that the organisms carry two alleles for each gene that they possess on each chromosome

What does a dominant allele mean?

Only a single allele is required for the characteristic to be expressed in the phenotype. Whether the organism only has one dominant allele or has two dominant alleles the trait will be expressed.

What does a recessive allele mean?

The characteristic is only expressed if there is no dominant allele present. It therefore means there must be two recessive alleles present in order for the phenotype to be expressed

What does a codominant allele mean?

Both alleles are expressed equally and contribute to the phenotype, with there with being a blend of the two characteristics or both characteristics being seen together.

What does pure breeding mean?

It is a homozygous pair of alleles

What is monohybrid inheritance?

when a phenotype or trait is controlled by a single gene

What is the ratio of phenotypes of the offspring of the F1 generation?

3:1

What is dihybrid inheritance?

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

What is an example of codominance?

The human ABO blood groups.

What is sex linkage?

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

What chromosomes do males have?

XY

What chromosomes do females have?

XX

Give an example of a sex-linked disease

Haemophilia

What is the cause of haemophilia

Haemophilia is caused by a change to the DNA sequence resulting in a faulty protein being created

What is autosomal linkage?

When two or more genes are on the same autosomal chromosome

What is epistasis?

The interaction between non-linked genes which causes one to mask or supress the expression of the other in the phenotype

What is recessive epistasis?

When the presence of a recessive allele prevents the expression of another allele

What is the ratio for recessive epistasis?

9:3:4

What is dominant epistasis?

When a dominant allele at one locus masks the alleles at a second locus

What is the ratio for dominant epistasis?

12:3:1

What are the conditions for the Hardy-Weinburg principle?

No mutations occur, there is no migration into or out of the population, mating is random, the population size is large, there are no natural selection pressures

What letter represents the frequency of the dominant allele?

P

What letter represents the frequency of the recessive allele?

Q

What letters represent the frequency of heterozygous individuals

2PQ

What is the equation for the possible allele combinations?

p2 + 2pq + q2 = 1

What is the equation for all of the alleles in the gene pool

p + q = 1

What is the chi-squared test?

a statistical test which can be used to establish whether the difference between the observes and expected results is small enough to occur purely due to chance

What is the formula for chi-squared?

the sum of [(O - E)2/E]

What are the conditions for using student's t-test are?

The data must be continuous and normally distributed, the variance of the populations should be equal, the samples must be independent of each other.

How do you calculate degrees of freedom in the chi-squared test?

n-1

How do you calculate degrees of freedom in the t-test?

n1+n2 -2

How do you calculate degrees of freedom in the correlation coefficient test?

n-2

What is speciation?

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

What is allopatric speciation?

when members of a population are geographically separated by a physical barrier and the separation exposed the different populations to different environmental pressures

Give an example of allopatric speciation?

The camel and the llama which both came from a common ancestor that lived on the landmasses that are now Africa and South America before continental drift separated these continents

What is sympatric speciation?

speciation that takes place within the same geographical location. Ecological or behavioural mechanisms, like habitat preference or mate selection, cause the speciation

How do you know whether to accept or reject the null hypothesis?

If the value obtained is equal to or greater than the critical value, the null hypothesis is accepted as the difference due to chance is not significant. If the value obtained is less than the critical value, the null hypothesis is rejected meaning that the difference between observed and expected

What is a population?

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

What is the gene pool of a population?

The gene pool is the total number of alleles that are present in a population

What is the allelic frequency?

Allelic frequency is the proportion of a certain allele in a gene pool expressed as a decimal or percentage

What are the factors that cause variation in the alleles of genes?

random fertilisation, meiosis, mutation

What is a niche?

the niche of a species is its role within the environment

What happens if two species share the same niche?

the better adapted species survive

What did Darwin think was the reason for animals have so many offspring?

Darwin suggested that the reason so many offspring are produced is so that 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 onto the next generation.

Give a summary of natural selection

Theres a variety of phenotypes within a population. An environment change occurs and a as a result of that the selection pression 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 leads to evolution.

What is selection?

the process by which individuals that are better adapted to their environment are more likely to survive. As a result, these individuals will breed and produce offspring.

What are the 3 main types of selection?

Directional, stabilising and disruptive

When does directional selection occur?

Directional selection occurs when the environmental conditions change and the phenotypes best suited to the new conditions are more likely to survive. As a result these individuals will breed and produce offspring. Over time the mean of the population will move in the direction of these individuals.

Give an example of directional selection

Bacteria being resistant to antibiotic. A single bacteria will have had a mutation that meant it was not killed by penicillin as it could produce the enzyme penicillinase. As a result, it was able to grow and populate, and the frequency of the allele that enable penicillinase production increased in the population. There fore the population moved to have greater penicillin resistance.

What happens in stabilising selection?

In stabilising selection the phenotypes with successful characteristics are preserved and those of greater diversity are reduced.

Why does stabilising selection occur?

Stabilising selection doesn't occur due to changes in environment. If the environment stays the same then 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.

Give an example of stabilising selection?

An example of stabilising selection is newborn babies' weights. Those that have a birth weight of around 3kg are more likely to survive than those at the extremes.

What is disruptive selection?

the opposite of stabilising selection and is where both extreme of the normal distribution are favoured over the mean

Give an example of disruptive selection

An example of disruptive selection is where certain large mammals are adapted to surviving long period without food due to increase in body fat, whilst small mammals of the same species survive sue to their decreased need for food. As a result, the intermediate sized animals are selected against.

What is an ecosystem?

An ecosystem includes all the organisms living in a particular area known as the community as well as all the non-living elements of that particular environment.

What controls the distribution and abundance of organisms in a habitat?

It is controlled by both biotic (living) and abiotic (non-living) factors).

Which abiotic factors affect size and rate of population growth?

Temperature (each species has its own optimum temperature), light (rate of photosynthesis is dependent on light), pH (impacts enzymes), water and humidity.

What is carrying capacity?

The certain size of population of a species that an ecosystem can support

Give examples of factors that species might be competing for

Food, water, mates, shelter, minerals, light

What are the two types of competition?

Interspecific and intraspecific competition

What is interspecific competition?

Where members of different species compete with one another for the same resources

What is intraspecific competition?

Where members of the same species compete with one another 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 predation occurs and the populations of the predator and prey affect one another

How can the size of the population for slow-moving/ non-motile organisms be estimated?

Using either randomly placed quadrats, or quadrats along a belt transect

How can the size of the population for fast-moving organisms be estimated?

Using the mark-release-recapture method

What is the equation for the estimated population size in the mark-release-recapture method?

(PHOTO)

What are the assumptions made with the mark-release-recapture method?

The marked individuals distribute evenly, no immigration or emigration, no births or deaths, marking method does not reduce chance of survival, marks don't rub off, the proportion of marked to unmarked individuals remains constant.

What is primary succession?

When a land previously devoid of life is colonised by a pioneer species that stabilise the environment, making it more suitable for more complex organisms.

What is a climax community?

A self-sustaining and stable community of organisms - the final stage of succession

What is secondary succession?

When a previously colonised area in which an existing community has already been clear, undergoes succession. However, succession begins at a later stage.

What is conservation?

Conservation is the human management of the earth's resources and typically involves the managing of succession

Give an example of conservation

The controlled burning of land in order to stop the formation of a climax community