present complex forms of living organisms have arisen from simpler ancestral forms through process called evolution.
Definition
Gradual change in the inheritable characteristics of a population over time is called evolution #BiologyDefinitions
Spontaneous Mutation Takes Place, producing varieties of coat colour and size in a rabbit population
- rabbits may migrate to 2 diff. env. for e.g. dense forest and open plain
Competition among the different rabbit varieties results in the survival of the fittest. nature selects the varieties with the favourable genes and characteristics best fitted to the environment to survive (natural selection). the other varieties may die or decrease in number due to competition for food, diseases or predation.
| Dense Forest | Open Plain | |
|---|---|---|
| - Variety A has dark coloured fur coat which camouflages it well in the dark forest - This together with its small size and crouching position, makes it less easily detected by predators. - small size also allows it to hide in crevices or among logs | those that survive reproduce and pass down their favourable genes to their offspring. they become predominant variety in their env. | - Variety B develops a light coloured fur coat, as this colour is ideal camouflage for open plains - larger size and long hind legs enable it to run faster and escape from predators. - long ears give it a keener sense of hearing to detect predators. - upright position allows it to see farther both for its source of food and for the approach of predators. |
| Over LONGGG period of time → 2 diff varieties have evolved as a result of mutation, competition, natural selection. | ||
| each variety is suited to survive in its own environment but not the others. | ||
| such a process of evolution takes long time to occur, maybe thousands or millions of years, which could lead to the formation of new species. |
Summary
1. Variety and Competition for Survival
- organisms have great reproductive potential
- they produce more offspring than can survive
- organisms die bc of environmental such as competition for food, diseases and being eaten up by predators
- mutations cause organisms to show variation i.e. differences in characteristics.
- variations and competition lead to differential survival and reproduction by those organisms best fitted to the env.
2. Survival of the fittest
- organisms with favourable genes and characteristics that make them better adapted to env conditions → most likely to survive.
3. Reproduction and Passing down Favourable Genes
- organisms that survive reproduce and pass down their favourable genes to their offspring
- over time, more beneficial qualities (genes or alleles) may accumulate in a species.
- new breed of organisms may be better adapted to their new env.
- they may even change so much that they become a new species which differs from the original species from which they have evolved.