Darwins observations

what are the 4 observations of darwin

1. organisms have an ability to produce large numbers of offspring (they over reproduce)

2. populations in nature tend to remain fairly stable in size

3. no two individuals are identical (organisms vary)

4. offspring generally appear similar to their parents

over production of offspring

• all species have the potential to increase their numbers exponentially

• this doesn’t happen due to predators, competition, disease etc

examples of over production

• bacteria divide by binary fission every 20 mins. 1 bacteria can create 4 ×10 to the 21 in 24 hours

what is an example of over production control

• introducing non indigenous species which is a biological control

Darwins 3 deductions

1. there is a struggle for survival ie competing

2. individuals that are better adapted to their environment are most likely to survive and reproduce

3. these advantageous characteristics are then passed onto their offspring

natural selection

• variation in the basis of evolution

• genetics/genes and environment cause variation in a population

What is selection pressure

• environmental factor that affects the organisms chance of survival or reproductive success

• eg food, climate, water, mates

organisms who are best adapted to selection pressure

• have an increased chance of surviving and reproducing

• survival of he fittest

stages if natural selection

1. individuals with favourable characteristics will survive longer, reproduce more and have more offspring

2. their favourable alleles will be passed onto offspring

3. over many generations, the frequency of favourable allele will increase

adaptations

• a feature of an organisms that enhances survival and long term reproductive success

adaptations can be split into 3 groups

1. behavioural adaptations- way organisms acts

2. physiological adaptations- processes taking place inside organisms

3. anatomical adaptations- physical features- internal and external

speciation

• selection over time can lead to speciation

• this is the formation of a new species through the process of evolution