3.4.4 Genetic diversity and adaptation Flashcards Preview

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Flashcards in 3.4.4 Genetic diversity and adaptation Deck (28)

Define 'genetic diversity'

The number of different alleles of each gene (within in a population )


Apart from genetic factors what other type of factors causes variation within a species

Environmental (biotic and abiotic) factors


What is a species?

A group of organisms with similar features that can interbreed to produce fertile offspring


Explain how crossing over can contribute to genetic diversity

Sections of chromatids are exchanged.
Different sections have different alleles so new combinations of linked alleles are made.


What can different species not do?

They cannot breed to produce fertile offspring as they have different genes and may have a different number of chromosomes


What is a population

A population is a group of the same species in the same place that can interbreed


Go through the stages of natural selection

1. A change in the environment causes a selection pressure
2. Random mutations produce genetic diversity
3. Some alleles provide an advantage
4. Those individuals with the advantageous alleles survive and reproduce
5. So the advantageous alleles are passed on
6. This means the frequency of advantageous alleles in the population increases


Who decides what is the advantageous alleles?

The environmental conditions (nature)
Humans if selective breeding


What is a selection pressure?

An environmental change that affects a population resulting in the death of some individual and the survival of those that are better adapted (those with favorable alleles)


What are the 2 types of variation and give examples

•Continuous variation - a characteristic that an have a wide range of values shows continuous variation e.g. height, weight

•Discontinuous variation - a characteristic with few possible values shows discontinuous variation e.g. blood group


Monogenic characteristics often show which type of variation



Polygenic characteristics often show which type of variation



Describe and explain how selection can affect the genetic diversity of a species

The genetic diversity is reduced as alleles have been chosen and rejected


What is selection?

Selection is the process by which organisms that are better adapted to their environment survive, reproduce and pass on their genes


Other than hunting give 2 reasons why populations might show low levels of genetic diversity.

1. population is small
2. inbreeding
3. population started with one pregnant female


Index of diversity is higher in a hedge than a barley field - why?

1. more plant species
2. more food sources/variety of food
3. more habitats
4. More niches


In a diploid organism phenotype (expressed characteristics) is determined by what?

Genotype (the combination of alleles present)


What is meant by a low genetic diversity?

A small variety of different alleles.


If there was no genetic diversity could natural selection occur?

No - because there would be no advantageous alleles.


Define the term 'gene pool'.

The total number of alleles in a population at any given time.


What is directional selection and what does it result in?

1. Where selection favours individuals that vary in one direction from the mean of the population e.g. antibiotic resistant bacteria when using antibiotics.

2. This changes the characteristics of the population.


What is stabilising selection and what does it result in?

1. Where selection favours individuals average individuals e.g. when environmental conditions are stable.

2. This preserves the characteristics of the population.


When you plat continuous variation on a graph it will produce which type of curve?

A 'normal distribution curve'.


The 3 types of adaptations are...

1. Anatomical
2. Physiological
3. Behavioural


Give an example of an anatomical adaptation.

Short ears and thick fur in arctic foxes.


Give an example of a physiological adaptation.

Physiological = functional changes e.g. oxidising fats instead of carbohydrate in kangeroo rats to provide additional water in a hot environment.


Give an example of a behavioural adaptation.

Autumn migration of swallows from U.K. to Africa to avoid winter food shortages.


state 3 comparisons of genetic diversity

base sequence DNA
base sequence RNA
amino acid sequence of proteins

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