3.4.4 Genetic diversity and adaptations Flashcards
Define “genetic diversity”
The number of different alleles of each gene within a population
Apart from genetic factors what other type of factors cause 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 offspirng 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 speicies in the same place that can interbreed
The stages of natural selection
- A change in the environment causes a selection pressure
- Random mutations produce genetic diversity
- Some alleles provide an advantage
- Those individuals with the advantageous alleles survive and reproduce
- So the advantageous alleles are passed on
- This means the frequency of advantageous alleles in the population increases
Who decides what is he 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 individuals and the survival of those that are better adapted (those with favourable alleles)
What are the two types of variation and give examples
Continuous variation - a characteristic than can have a wide range of values e.g. height, weight
Discontinuous variation - a characteristic with few possible values e.g. blood group
Monogenic characteristics often show which type of varation
Discontinuous
Polygenic characteristics often show which type of variation
Continuous
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 selction?
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
- Population is small
- Interbreeding
- Population started with one pregnant female
Index of diversity is higher in a hedge than a barley field - why?
- More plant species
- More food sources / variety of food
- More habitats
- 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 diveristy?
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?
Where selection favours individuals that vary in one direction from the mean of the population e.g. antibiotic resistant bacteria when using antibiotics
This changes the characteristics of the population
What is stabilising selection and what does it result in?
Where selection favours individuals average individuals e.g. when environmental conditions are stable
This preserves the characteristics of the populaion
When you plot continuous variation on a graph, it will produce which type of cure?
A “normal distribution curve”
The 3 types of adaptations are..
- Anatomical
- Physiological
- Behavioural
Give an example of an anatomical adaptation
Short ears and thick furs in arctic foxes
Give an example of a physiological adaptation
Physiological = functional changes
e.g. oxidising fats instead of carbohydrates in kangaroo rates to provide additional water in a hot environment
Give an example of a behavioural adaptation
Autumn migration of swallows from UK to Africa to avoid winter food shortages
State 3 comparisons of genetic diversity
Base sequence DNA
Base sequence RNA
Amino acid sequence of proteins
