Ngā Whāinga Ako ^🔗

• Understand the importance of variation

Brainstorm: Variation
What are some ways that humans vary? ^🔗

Continuous vs Discontinuous ^🔗

• We can split variation up into two different groups: continuous and discontinuous.
• Continuous is a spectrum like height or hair colour
• Discontinuous is things like attached or dangling earlobes

Whakamātau: sciPAD Page 50 ^🔗

Sources of Variation ^🔗

There are four main sources of variation that we are interested in:

• Mutation
• Sexual reproduction
• Fertilisation
• Environment

Mutation ^🔗

• Random changes in the base sequence of DNA that may result in a new allele forming.
• Many things can cause mutations: think radiation (e.g. UV & skin cancer)

Sexual Reproduction (Meiosis) ^🔗

• Meiosis is the process through which your body produces gametes (sex cells). These are sperm and ova in humans.
• It produces cells that have only one allele for each gene (23 chromosomes) so that when it combines with the opposite gamete, a full 46 chromosomes are made.

Fertilisation ^🔗

• When sperm and ova fuse, it is a random event. So, the final combination is random chance.

Environment ^🔗

• In some organisms the environment alters the expression of a genotype. Food and nutrient availability, competition, light intensity and disease may modify an expected phenotype.

Natural Selection ^🔗

• The biological imperative for any organism is to pass along its genes.
• The better you are able to this, the more fit (biologically speaking) you are.
• Therefore, natural selection is about environmental pressures that cause some individuals to die, while others survive due to a slightly different phenotype!
• We can see that variation is key to surviving change.