Evolution of Species

• Genetic Variation: Members of the same species are varied because of slightly different versions of the same genes.
• Mutations: Mutations are spontaneous, random changes to the genetic material of an organism.
• Mutations are the only way that new alleles are added into a population.
• Each sub-population evolves until they become so genetically different that they are two different species.
• Rabbits and hares are different species.
• A species is an organism that can reproduce to produce fertile offspring.
• A Liger or Tigon is not a new species because they cannot reproduce to produce fertile offspring.
• These butterflies have different wing types because of mutations.
• An allele is a form of a gene.
• Mutations can be neutral or have a advantage or disadvantage to survival.
• Sickle cell anaemia causes red blood cells to be a different shape.
• The malaria parasite reproduce in red blood cells but can’t affect a person with sickle cells because of the different shape.
• Sickle cells are less “bendy” so cannot get through blood vessels as easily.
• This causes blood clots and organ failure.
• Mutations are rare but some environmental factors increase the rate of mutations.
• Nicotine, Bromine, Chemicals, UV rays, Gamma rays, Radiation can increase the rate of mutations.
• New alleles that are produced by a mutation can cause plants and animals to change.
• If these changes are an advantage to survival then the plant or animal becomes better adapted to their environment.
• Camouflage helps an organism to hide from predators or to catch prey.
• Adaptation: An inherited characteristic that makes an organism well suited to surviving in its environment/niche.
• Beak shape is an adaptation in finches.
• The finches shown all descend from one type of finch.
• Variation within a population makes it possible for a population to evolve over a long period of time if their environment is changing.
• If populations can not do this then they will not survive!
• Timothy the dinosaur and the population he lives in need to adapt to the changing environment.
• Some mutations are a disadvantage to survival.
• Natural selection occurs when members of a species produce more offspring than are going to survive because there are not enough resources for them.
• Selection pressures occur when there are not enough resources to allow all members of a species to survive.
• The best adapted individuals survive to reproduce, producing offspring that have favourable alleles that help them to better survive over others.
• The least adapted individuals do not survive to reproduce so their alleles are not passed onto the next generation.
• Over time, the favourable alleles increase in frequency until most members of the population have them.
• Research one of the examples of natural selection below: Antibiotic resistance, Pesticide resistance in weeds, Darwin’s finches.
• Speciation is when two or more species are formed from one original species.
• There are four stages of speciation: Isolation, Mutation, Natural Selection, New species.
• Isolation is when one population of a species is separated by an isolation barrier, which can be geographical, ecological, or behavioural.
• Different mutations occur in each sub-population.
• Natural selection selects for the mutations that give the biggest advantage to the survival of each sub-population as they face new selection pressures.
• The best adapted individuals survive to reproduce, producing offspring that have favourable alleles that help them to better survive over others.
• The least adapted individuals do not survive to reproduce so their alleles are not passed onto the next generation.
• Over time, the favourable alleles increase in frequency until most members of the population have them.