B17 - Varitation and Selection Flashcards
Variation
Differences between individuals of the same species
Continuous variation results
A range of phenotypes between two extremes; examples include body length
Discontinuous variation results
A limited number of phenotypes with no intermediates; examples include ABO blood groups
Mutation
Genetic change
How are new alleles formed
Mutation
Genetic variation
Differences in the genotype (alleles that are present)
Phenotypic variation
Differences in the phenotype (observable characteristic)
Natural selection
- genetic variation within populations
- (over) production of many offspring
- struggle for survival, including competition for resources
- a greater chance of reproduction by individuals that are better adapted to the environment than others
- these individuals pass on their advantageous allele/characteristic to the next generation and become more common in the population
Selective breeding/ artificial selection
- selection by humans of individuals with desirable features
- crossing these individuals to produce the next generation
- selection of offspring showing the desirable features
How is selective breeding used to improve crops and animals?
- Parents with desired traits are chosen and bred
- Their best offspring are selected and bred again
- This repeats over generations to enhance traits (carried out over many generations)
(Domesticated animals and improvement in crops)
Causes of continuous variation + type of graph
- genetic and environmental
- histogram (have no gaps between bcus all data is flowy)
Causes of discontinuous variation + type of graph
- genetic
- bar chart (separate bars = separate groups)
Continuous variation
Can take any value within a range; many intermediate classes between the extremes
E.g - height, length of fur, hair colour, leaf circumference
Discontinuous variation
Can only result in specific (discrete) values; no intermediate classes
E.g - eye colour, biological sex, wrinkled seeds, left or right handed
How do strains of antibiotic-resistant bacteria develop?
- as bacteria are reproducing they make bacteria with mutations that resist antibiotics
- these survive treatment and reproduce
- Over time, resistant strains become more common — an example of natural selection.
Causes of variation
- genetic
- environmental
Types of variation
- continuous
- discontinuous
Define artificial selection (selective breeding)
Choosing particular organisms with desirable characteristics to breed together and continuing this over many generations
Define Natural Selection
A process in which individuals with advantageous features are more likely to survive + reproduce and pass on their alleles to the next generation
Agent of selection
Natural - Nature
Artificial - Humans
Species chance of survival
Natural- Good (increases)
Artificial- Low (decreases)
Speed of Change
Natural- Slower
Artificial- Faster
