4 Genetic Information & variation- Genetic diversity & adaptation Flashcards
What is genetic diversity?
The number of different alleles of genes in a population
What is an allele?
Multiple versions of a specific gene
Greater number of alleles = greater genetic diversity
How is genetic diversity in a population increased?
-Mutations (new allele creation)
-Gene flow (introduction of new alleles by migration)
What does genetic diversity in a population allow?
Natural selection to take place
-Acts on a population to increase frequency of advantageous alleles & decrease frequency of disadvantageous alleles
What are the principles of natural selection?
-Random mutation occur spontaneously and can result in new alleles of a gene
-Many mutations are harmful, but some may have a beneficial trait, leading to increased reproductive success
-After reproduction, offspring will inherit advantageous allele
-Over many generations, the allele will increase in frequency; evolution.
What is a selection pressure?
Natural selection acts on an individual by imposing a selection pressure, an external factor that influences the reproductive success of an individual, e.g. disease
What is stabilising selection? + example
-The process where natural selection favours an average phenotype
-Selection pressure selects against the extreme phenotype
-Takes place in environments that do not change
e.g. human birth weight- if a baby has below average weight, it’s less likely to survive & if it has above average weight, it’s more likely to encounter difficulties following birth. Stabilising selection selects for a phenotype within average weight range
What is directional selection? + example
-The process where natural selection favours an extreme phenotype
-Selection pressure selects against all other phenotypes
-Takes place after an environment has experienced a change
e.g. antibiotic resistance- if bacteria are exposed to antibiotics, most of the population will not be resistant to its effects, won’t survive. If a mutation evolves that causes resistance, selection will strongly favour the extreme, resistant phenotype.
What are adaptations?
Traits that have been selected for because they help increase an organism’s chance of survival and reproduction
What are anatomical adaptations? + examples
Physical structures that have evolved to increase the chance of survival
-Giraffe’s long necks allow them to access food other organisms can’t compete for
-Walrus blubber (thick layer of insulating fat), walruses live in cold environments so this helps them lose less heat
What are physiological adaptations? + examples
Processes within the body that have evolved to increase chance of survival
-Snake venom, protects from predators & captures prey
-Shivering mammals in cold environments, maintains body temperature at optimum range
What are behavioural adaptations? + examples
Actions that have evolved to increase chance of survival, can be learnt or inherited
-Cheetah hunting; stalking behaviour, creeping up silently and then chasing, increases chance of successfully catching prey
-Spider’s web; sticky, silk web allowing them to catch insects for food
