10.5 - types of variation

Question 1

Types of variation

Answer 1

• The widest type of variation is between members of different species - these differences are known as interspecific variation.
• For example, a mouse has four legs, teeth, and fur, whereas a bird has two legs, two wings, a beak and feathers
• Every organism in the world is different - even identical twins differ in some ways.
• Differences between organisms within a species are called intraspecific variation. For example, people vary in height, build, hair colour and intelligence

Question 2

Causes of variation: Genetic

Answer 2

1) Alleles - genes have different alleles. With a gene for a particular characteristic, different alleles prodduce different effects. For exampl, the gene for human blood groups has three different alleles (A, B, O). Depending on the parental combination, four different blood types can be produces.
2) Mutations: changes to the DNA sequence and therefore genes can lead to changes in the proteins that are coded for. These protein changes can affect physical and metabolic characteristics. If a mutation occurs in somatic (body) cells, just the individual is affected
3) Meiosis - Each gamete receives half the genetic content of a parent cell. Before the nucleus divides and chromatids of a chromosome separate, the genetic material inherited form the two parents is ‘mixed up’ by independent assortment and crossing over. This leads to the gametes of an individual showing variation
4) Sexual reproduction - the offspring produces from two individuals inherits genes from each of the parents. Each individual produces therefore differs from the parents.
5) Chance - many different gametes are produced from parental genome. During sexual reproduction, it is a result of chance as to which two combine. The individuals produced therefore also differ from their siblings. The individuals produced therefore also differ from their sibling.

Question 3

Causes of variation: Environmental

Answer 3

• Due to their lack of mobility, plants are more greatly affected than animals by their environment.
• For example, two rose bushes are planted in different positions in a garden. The one that has greater access to the sun will generally grow larger than one in a shadier position.
• An example of a characteristic that is determined purely by environmental variation is the presence of any scars on your body. They will have occurred as a result of an accident or disease and have no genetic origin

Question 4

Causes of variation: Environmental and genetic

Answer 4

• In most cases variation is caused by a combination of both envirnomental and genetic factors:
  1) If you have very tall parents, you have most likely inherited the genes to also grow to a tall height. However, if you eat a very poor diet or suffer form disease you may only grow to below average height.
  2) Another example of a characteristic that shows both environmental and genetic causes is your skin colour. Your skin colour at birth is purely by genetics - however, when you expose your skin from. harmful UV rays, your skin turns darker.