Genetic Diversity And Natural Selection Flashcards Preview

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Flashcards in Genetic Diversity And Natural Selection Deck (16):

Define genetic diversity?

The total number of different alleles in a population.


Define population?

Groups of interbreeding individuals of the same species. The greater the number of different alleles that a population posses the greater the genetic variation.


Define gene pool?

The total number of alleles in a population at a specific time.


How does genetic variation enable natural selection to occur?

It is the survival of the fittest, the winner posses characteristics providing a selected advantage e.g. Orchid bee with a longer tongue to reach the pollen.


Define evolution?

The change in allele frequency in a population over time, for evolution to occur there must be genetic variation within the population, a change in environment may result in an allele becoming selectively advantageous.


Define natural selection?

Random mutations of the DNA in the species which leads to an advantageous allele


How do advantageous alleles get passed on?

There is a selection pressure or change in the environment, for example competition or predation. The mutation makes he organism more adapted for the habitat. Individuals with the advantageous alleles will survive by out competing others. Individuals without the advantageous alleles will die. Individuals with the advantageous alleles will breed and reproduce so the advantageous alleles will be passed on to future generation which increases the frequency of alleles in the population.


What leads to evolution?

Differential reproductive success leads to evolution.


Define adaptability?

How well an organism suits is environment.


What does adaptability depend on?

- size of gene pool
- strength of selection pressure and how important it is
- reproductive rate of organisms


What are the three types of adaptions?



What are behavioural adaptions?

Actions taken by organisms e.g. squirrels burying nuts and plants turning towards the sun.


What are physiological adaptions?

Features of internal workings for the organism which aid survival or reproduction e.g. Danish scurvy grass which tolerates high salt concentrations.


What are anatomical adaptions?

Structures of the organism we can observe or dissect e.g. Bees with long tongues to collect nectar.


Define stabilising selection?

When conditions remain stable, this favours average individuals in the middle range e.g. birth weight of babies. It reduces the range of possible characteristics, it narrows the data more closely bunched around the mean. And the selection pressure effects both sides of the mean.


Define directional selection?

It occurs when a selective pressure occurs i.e. an environmental change, this favours one direction away from the mean e.g. Antibiotic resistance in bacterial populations. It changes the characteristics of the population, the mean shifts to the left or the right and the selection pressure effects one side of the mean.