variation and selection

All organisms vary from one another , even within a species. Variations in living organisms has both a genetic and environmental basis. Name a feature which is due to genetics only Name a feature which is due to environment only Name a feature which is due to both

There are 2 types of variation in organisms: 1. Discontinuous variation These characteristics fall into groups for example your blood group can be A, B, AB or O

Another example includes whether you can or can’t roll your tongue.

Discontinuous characteristics tend to be the result of genes only.

The bars are separated from one another by a space Bar graphs are used to display data gathered about discontinuous characteristics. The bars are separated from one another by a space

Height is an example of discontinuous variation Characteristics are between 2 extremes Height is an example of discontinuous variation

Continuous characteristics tend to be the result of both genes and the environment. Factors such as the availability of food, water, and disease will affect the eventual height a person is able to grow to.

Both of these maple trees are 30 years old. The one on the left is a bonsai, it’s roots have been pruned to restrict growth. However, it has the genetic potential to reach the same height as the tree on the right.

Histograms are used to display data gathered about continuous variation. The bars are not separate from one another, but show a continuous range. Found in the middd

This characteristic bell shape is known as a normal distribution. The histogram shows that there are few very small or very tall people; most are of the middle heights. This characteristic bell shape is known as a normal distribution. Found in the middd

Write a title for the graph. Use the graph to describe two differences between the heights of men and women. How would you gather reliable, valid data to produce this graph? The height of men compared to women The average height of men is more than women. The range of heights of men is bigger than women. There are fewer men of average height than women. Large sample of men and women (>1000) Same age Same ethnic origin

Sexual reproduction results in genetic variation due to meiosis, fertilisation and mutation

Variation and selection may lead to evolution or extinction. Organisms that can adapt to a changing environment evolve, those that don’t become extinct.

natural selection Organisms within a species have different features or phenotypes In large populations organisms will compete for resources (food, space, mates) A change in the environment occurs Organisms with the best adapted features are more likely to survive These organisms reproduce, passing on their genes to their offspring The new population gradually changes to suit the environment.

antibiotic resistance

mrsa

antibiotics kill bacteria A population of disease causing bacteria has many mutations. One mutation may give resistance to an antibiotic such as penicillin. When someone is given penicillin to kill an infection of these bacteria, the ones without the mutation will die, but the antibiotic resistant ones will survive and reproduce. All of their offspring will be resistant to the antibiotic and so will continue to multiply. A different antibiotic must be used to kill these bacteria.

Charles Darwin from “The Origin of Species” British 1809-1882 “ I have called this principle by which each slight variation, if useful, is preserved, by the term Natural selection.” Charles Darwin from “The Origin of Species”

evolution Natural selection over thousands of years is thought to be the driving force behind evolution in which organisms gradually change from one form to another