TOPIC 4 - Genetic diversity and adaption Flashcards
Define genetic diversity
The number of different alleles of a gene in a species/ population
Why is genetic diversity important?
-If a population has a low genetic diversity it may not be able to adapt to changes in the environment and the whole population could be wiped out by a single event such as disease
Which factors increase genetic diversity?
-Mutations in the DNA forming new alleles- can be advantageous/ disadvantageous (point mutations and frameshifts
-Different alleles being introduced into a population migrate into it and reproduce (gene flow)
-Crossing over
-Independent segregation
-Random combination of gametes
-Non disjunction
-Homologous chromosomes in A1
-Sister chromatids in A2
-Sister chromatids in mitosis
-Allele interactions
What is a genetic bottleneck?
-An event that causes a big reduction in a population
Give an example of a genetic bottleneck
-When a large number of organisations die within a population before being able to reproduce
Why do genetic bottlenecks reduce genetic diversity?
-Reduces the number of different alleles in the gene pool
What is the founder effect?
-Describes what happens when just a few organisms from a population start a new colony and there is only a small amount of different alleles in the initial gene pool
-This frequency of each allele in the new colony might be very different to the frequency of those alleles in the original population
What does the founder effect lead to?
-High rates of genetic disease
How does the founder effect occur?
-As a result of migration leading to geographical separation or if a new colony is separated from the original population for a reason such as religion
What is natural selection?
-When the allele codes for a characteristic that increases the chances of an organism surviving, its frequency within the population can increase
What is differential reproductive success?
-Individuals that have an allele that increases their chance of survival are more likely to survive, reproduce and pass on their genes however the individuals with less advantageous alleles are less likely to survive
Explain the steps of natural selection
- Differential reproductive success
- DFS means that a greater proportion of the next generation inherits the beneficial allele
- They are more likely to survive, reproduce and pass on their genes
- The frequency of the beneficial allele in the population increases from generation to generation
- Over generations this leads to evolution as the advantageous alleles become more common in the population
Define evolution
-The gradual change in species over time
What are adaptions?
-Features that help organisms to survive in their environment
What are the three types of adaptions?
-Behavioural
-physiological
-Anatomical (structural)
What are behavioural adaptions?
-These are ways an organism acts that increase it’s chance of survival
Give 2 examples of behavioural adaptations
-Possums- play dead to escape attack
-Scorpians- dance before mating- makes sure they attract a mate of the same species
What are physiological adaptions?
-Processes inside an organisms body that increase it’s chance of survival
Give 2 examples of physiological adaptions
-Brown bears hibernate- Lower their metabolism to conserve energy
-Some bacteria produce antibiotics- kill other species of bacteria, less competition
What are anatomical adaptions?
-Structural features of an organisms body that increase chance of survival
Give 2 examples of anatomical adaptions
-Otters- streamlined, easier to catch, increase their chance of survival
-Whales- have a thick layer of blubber, increases chances of survival in the places where their food is found
What is directional selection?
-Individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce
What could directional selection be a response to?
-Environmental change
What is stabilising selection?
-Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
When does stabilising selection occur?
-When the environment isn’t changing
What does stabilising selection reduce?
-The range of possible characteristics
What factors decrease diversity?
-Natural selection/artificial
-Selective breeding
-Selection pressure
-(All environmental)
What are selection pressures?
-A factor which causes selection within a population
by exerting environmental resistance
Draw a flow diagram for natural selection
-Mutations
-Variation
-Adaptations
-Survive
-Reproduce (differential success)
-Alleles passed on
-Change in allele frequency
Give some examples of selection pressures
-Competition
-Predation
-Limited light, oxygen,water and other abiotic factors
-Variation in temp (global warming)
-Disease
-Human influence- pollution,overuse of antibiotics, pesticides and poisons
How would you apply natural selction?
-Random mutation may result in a new allele of a gene
-The new allele may provide the possessor with an advantage/adaptation
-This individuals will be better adapted to source resources, compete and survive
-As a result of being successful they will be more likely to attract a mate, reproduce and pass on their alleles onto the next generation
-As their offspring will have the new, advantageous allele they are more likely to survive
-Over time the frequency of the new allele will increase in the population
What is a dominant (S) allele?
-The allele that is always expressed even if only one copy (of the two) is present
What is a recessive (s) allele?
-Trait is only produced if there is 2 copies of the allele
What is allele frequency?
-How common an allele is in a population
