Natural Selection Flashcards
What causes variation within a population
Genetics: controls what characteristics are inherited
1. Mutation
2. Meiosis -> genetic variation between the gametes produced by an individual
3. Random Fertilisation (random fusion at fertilisation creates genetic variation between zygotes
Environmental: (controls how inherited characteristics develop)
4. Environmental factors e.g. plant growing taller in the shade to reach more light
Variation definition
Differences between individuals of the same species
What is discontinuous variation caused by
Genetic variation alone
What cause variation in continuous features and why do they often vary
-combination of genetic and environmental causes
Darwins theory of evolution
Evolutionary change has occurred and that natural selection is the process that has driven this change
Process of natural selection
-Mutation/meiosis
-causes variation by difference in genes
-individuals with advantageous characteristics are better adapted to the environment they are in
-they are more likely to survive
-surviving individuals are more likely to reproduce and so are more likely to pass on their advantageous genes/alleles
-over many generations this change in characteristics leads and the characteristics becoming more common in a population is evolution
Antigen
Substance on the outside of pathogens that elicits an immune response
Antibiotic resistance process
-mutation occurs which carries the gene for antibiotic resistance
-variation is introduced into the population
-bacteria are better adapted to the environment with antibiotics
-antibiotics acts as a selection pressure
-adapted bacteria survive, non-resistant are killed
-bacteria with advantageous genetics reproduce, passing advantageous genes.
-there is a rapid population growth
-Over generations the bacteria evolves to form new species
-after this bacteria are resistant to antibiotics
-if antibiotic resistant bacteria enter our body likely an infection will be cause because it will not be killed by antibiotics
Evolution
Where there is a cumulative change in heritable characteristics over time in a population
Selective breeding
Select individuals with desirable characteristics and breed them together
Why is the selective breeding repeated for many successive generations
-not all offspring will show characteristics initially, -offspring that show the desired characteristics are selected and bred together
-continued until offspring reliably show selected characteristics
Reasons for selective breeding in plants
-disease resistance in food crops
-increased crop yield
-hardiness to weather conditions
-large/unusual flowers
-better tasting fruits
Problems with selective breeding
-can lead to inbreeding, where the best animals or plants are closely related to each other are bred together
-results in a reduction in the gene pool
-reduction in number of alleles in a population
-increased chance of inheriting harmful genetic defects
-organisms being vulnerable to new disease (less chance of resistant alleles being present in gene pool)
Reasons why animals are selectively bred
-animals that produce more milk or meat
-chickens that lay large eggs
-domestic pets that are gentle
-sheep with good quality wool
-horses with a fast pace
Differences between artificial selection and natural selection
-humans not involved
-best adapted survive in natural
-more generations involved on natural
-natural involves the role of mutations
-natural selection involves evolution
