Variation and Evolution

• Variations are differences between members of the same species.
• The 3 causes of variation are:

  -Genes

  -Environment

  -Genes and environment
• We inheret our genes from our parents.
• We can not change genetic variations.
• You can pass genetic variations onto your offspring.
• An environmental variation is events that have happened in your life. (hair cut).
• You can change environmental variation.
• You can not pass on environmental variation on to your offspring.
• Example of gene variation:

  -Having dimples or not.

  -Being able to roll your tongue.

  -Blood type.

  -Gender.

  -Having attached or detached ear lobes.

  -Eye colour.

  -Natural hair colour.

  -Natural skin colour.
• Example for environmental variation:

  -Hair cut

  -Religion

  -Broken nose

  -Scar

  -Language spoken.

  -The ability to swim.

  -Tooth decay.
• Both Genes and environment:

  -Hair colour

  -Skin colour

  -Weight

  -Height
• The two types of variation are continuous or discontinuous.
• Examples of continuous variation are height and weight.
• Continuous variation are characteristics that change gradually over time.
• Examples of discontinuous variation are blood type and gender.
• Discontinuous variation are characteristics of any species with only a limited number of possible values.
• The two types of reproduction are sexual and asexual.
• In sexual reproduction there are two parents.
• In sexual reproduction, there are two gametes (egg + sperm)
• Fertilisation occurs in sexual reproduction.
• In sexual reproduction,the offspring are not genetically identical.
• Examples of sexual reproduction are:

  -Lions

  -Humans

  -flowering plants

  -Horses
• In asexual reproduction only 1 parent is present.
• In asexual reproduction there are no gametes.
• In asexual reproduction fertilisation does not occur.
• In asexual reproduction, the offspring are genetically identical (clone).
• In asexual reproduction there is no variation.
• Examples of asexual reproduction are:

  -Starfish
• A mutation is caused by a change in a gene.
• Mutations are usually harmful.
• Mutations can be good as the organism can develop characteristics that can help them to be better adapted to their environment.
• Mutations happen naturally and at random.
• Mutation can cause cancer then can potentially lead to death.
• The causes for mutation are:

  -X-rays

  -Ultra-violet rays.

  -Toxic chemicals.

  -Radioactive substances.
• Being in the presence of ionising radiation can greater the risk of mutations.
• An inherited disease that is caused by mutation is cystic fibrosis.
• Cystic fibrosis causes the production of thick mucus in the lungs and it blocks the bronchioles.
• Cystic fibrosis is inherited as a recessive allele.
• The symptoms of cystic fibrosis are coughing.
• Cystic fibrosis is treated by using gene therapy.