4.4 Flashcards
Define population
all the organisms of a particular species that live in the same place
what is an allele?
different forms of a particular gene found at the same locus on a chromosome
A single gene could have many alleles
define genetic diversity
the total number of different alleles in a population
what advantages does a high genetic diversity provide?
ability to adapt to a change in environment allows natural selection to occur
explain how natural selection results in development of new characteristics
-random mutations result in new alleles
-some alleles provide an advantage, making an individual more likely to survive and reproduce
-their offspring receive the new allele and frequency continues to increase over many generations
What is directional selection?
-occurs when environmental conditions change
-individuals with phenotypes suited to the new conditions will survive and pass on their genes
-Overtime the mean of the population will move towards these characteristics
Give an example of directional selection
-Antibiotic resistance
-Bacteria with a mutation allowing them to survive in the presence of antibiotics will reproduce
-therefore frequency of this allele will increase and the population will shift to have greater antibiotic resistance
What is stabilising selection?
~Occurs when environmental conditions stay the same.
-Individuals closest to the mean are favoured and any new characteristics are selected against
-Results in low diversity
Give an example of stabilising selection?`
-birth weights
-babies that weigh around 3kg are more likely to survive than those at lower or higher weights
Define a niche
-the role of a species within its environment
-species sharing the same niche will compete with each other
What are three types of adaptation?
Give examples of each
-Anatomical (changes to body structure) e.g. oily fur
-Physiological (changes to bodily processes) e.g. venom production
-Behavioural (changes from actions) e.g. hibernation.
