Genetic diversity Flashcards
Natural selection
The process by which the frequency of ‘advantageous’ alleles gradually increases in a population’s gene pool over time.
Evolution
A change in allele frequency overtime
Stabilising selection
A type of selection that favours individuals close to the mean, maintaining the traits of the population.
Selection pressure
An external factor that influences the reproductive success of an individual.
Example of Selection pressure
Disease acts as a selection pressure that increases the reproductive success for individuals who are immune to the disease.
In what type of enviroment does stablising selection take place in
An enviroment that does NOT change
Example of stablising selection
Human birth rate.
- If a baby has a below average weight, it is unlikely to survive.
- If a baby has an above average weight, it is more likely to encounter difficulties during birth.
Directional selection
The process where natural selection favours an extreme phenotype
When does directional selection take place?
After an environment has experienced a change.
Example of Directional selection
Antibiotic resistance
If bacteria are exposed to antibiotics, most of the population will not be resistant to its effects and will not survive.
If a mutation evolved that confers resistance, selection will strongly favour bacteria with the resistant phenotype.
What phenotype is favoured in bacterial populations that are exposed to antibiotics?
Antibiotic resistance
What type of environment does stabilising selection take place in?
Non-changing
Describe how an adaptation, such as better running speed, relates to natural selection.
Natural selection reproduces individuals with favourable genetic traits-such as adaptation of better running speed-over time
Adaptions
A feature of an organism that increases its chance of survival in its environment. An adaptation may be anatomical, physiological or behavioural.
Anatomical adaptations
Physical structures that have evolved to increase the chance of survival.
Examples of Anatomical adaptations
The long neck of giraffe - Allows them to get food easily
Blubber - Insulates Walruses. helps them prevent heat loss
Physiological adaptations
are processes within the body that have evolved to increase the chance of survival.
Examples of Physiological adaptations
- Venom produced by some snake species (e.g. the black mamba) is a physiological adaptation.
- to protect them from potential predators which increases their chance of survival.
- Shivering is a physiological adaptation.
Mammals have evolved to shiver in cold environments.
Shivering helps maintain body temperature within optimum range
Behavioural adaptations
actions that have evolved to increase the chance of survival.
Example of Behavioural adaptations
Hunting of cheetahs’s - The stalking behaviour increases the chance the cheetah will successfully catch a prey.
Spider webs - Increases the chance the spiders will survive because they can catch food more easily.
Snake venom is an example of what type of adaptation?
A physiological adaptation
Aseptic techniques include:
Disinfect surfaces.
Sterilise equipment to destroy microorganisms.
Flame the necks of bottles on opening.
What is the zone of inhibition?
Zone where no bacteria grow
Stages involved in investigating Microbial growth:
- Make sure the conditions for experiment are aseptic
- Spread the bacteria onto a petri dish
- Place antibiotic ring on the petri dish
- Place lid on the petri dish and loosely secure the lid with tape
- Incubate the petri dish upside down for 24-48 hours
- Observer the growth pattern of bacteria
