Natural Selection 3 30 Describe the process of

Natural Selection � 3. 30 Describe the process of evolution by means of natural selection. � 3. 32 Understand how resistance to antibiotics can increase in bacterial populations (natural selection).

Natural selection � Darwin put forward theory of ‘natural selection’. � It can be summarised by the following points: Variation Over-production Struggle for existence Survival of the fittest Advantageous characteristics passed on to offspring ◦ Gradual change ◦ ◦ ◦

Variation � Organisms are genetically different, they have different characteristics � Some may be slightly better adapted to their environment than others.

Over-production Over-Production � More offspring are produced than will survive.

Struggle for existence Struggle for Existence � There will be competition between organisms for resources e. g. food, water, light, shelter and mates. �

Survival of the fittest Survival of the Fittest � Only those who are best adapted to their environment will survive and reproduce (the strongest).

Reproduce � Beneficial genes and characteristics will be past onto offspring when these organisms reproduce � This is theory of natural selection - when nature selects which organisms will survive and reproduce. Those that are best-adapted to their environment will pass their genes onto their offspring.

Antibiotic resistance � Some bacteria can become resistant to antibiotics, such as penicillin.