Biodiversity Flashcards
what is genetic diversity?
Genetic diversity is the number of different alleles within a population.
What is a population?
A population is a group of the same species, in the same place that can interbreed
What is the result of genetic diversity?
-More Genetic Diversity = More Alleles
-Wider Range of Characteristics/Variation (bigger gene pool)
-Greater Chance of Individuals Surviving
Environmental Change
Use the example of the giraffes with long necks in to explain how a change in the environment leads to the length of necks increasing
-Change in environment causes a selection pressure.
-Random mutations produce genetic diversity- alleles for neck.
-Some alleles provide an advantage to gaining resources.
-Those individuals with the alleles survive and reproduce.
-Advantageous alleles are passed on.
-The frequency of advantageous alleles in the population increases.
-Frequency of long neck increases.
Who decides what is advantageous?
either the environment or nature
What is the mnemonic to remember?
Some - selection pressure
Really - random
Mental - mutations
Goats - genetic diversity
Ate - advantage
Some - survive
Raw - reproduce
Premium - pass on alleles
Fish - freq of alleles increase
Fingers - frequency of trait increase
Explain variation BETWEEN species
Different species have different genes.
They may also have a different number of chromosomes.
They cannot breed to produce fertile offspring and have different features.
Explain variation WITHIN a species
All members of the same species have the same genes.
Members of the same species differ due to their allele combinations.
What is selection?
The process by which organisms that are better adapted to their environment survive and reproduce, while those who are less well adapted do not.
What is a selection pressure?
An environmental change that leads to selection.
What are the types of variation?
continuous and discontinuous
What is continuous variation?
A characteristic that can have a wide range of values shows continuous variation.
Producing a histogram of continuous variation produces what kind of distribution curve?
A ‘bell shaped’ normal distribution curve
What is discontinuous variation?
A characteristic with few possible values shows discontinuous variation. There is no bell curve
What are most characteristics controlled by?
Most characteristics are controlled by multiple genes/alleles (polygenic) so show more variation.
What is the difference between polygenic traits and monogenic traits?
Polygenic traits are more influenced by the environment than monogenic traits. The environment affects gene expression - more genes more exposure to environment.
What 2 effects can selection produce on a population?
-Favouring individuals that vary from the mean -directional selection.
-Favouring the average individuals - stabilising selection.
What is directional selection?
Favouring individuals whose characteristics vary from the mean.
Phenotypes are selected for. Genotypes are indirectly selected.
What are some things we should remember about mutations?
-Mutations do not occur because of selection pressures
-Mutations are random and rare
-Most do nothing or are harmful and lead to death.
-A mutation leading to an advantage is a result of chance
-Bacterial populations are large so chance is greater
How can the rate of mutations increase?
-due to environment
What is stabilising selection?
-If conditions remain stable, individuals with average characteristics are favoured.
-Phenotypes at the extremes are selected against. Genotypes are indirectly being selected.
What does increased proportion =?
increased proportion=well adapted
What do directional and stabilising selection do to characteristics?
Directional selection CHANGES
CHARACTERISTICS, Stabilising selection
PRESERVES CHARACTERISTICS.
What do courtship behaviours allow individuals to do?
-Recognise of members of the same species.
-Identify a sexually mature mate.
-Form a pair bond that will lead to successful mating and raising of offspring.
-Synchronise mating so that it takes place at a time where egg and sperm are most likely to meet.
-Become able to breed by bringing a member of the opposite sex into a state that allows breeding to occur.