Evolution Flashcards
When have scientists estimated that life on Earth began?
About 3 billion years ago
Complete the sentence:
Before the 18th century there were…
…few scientific ideas about how evolution worked
Describe Jean-Baptiste Lamarck’s theory
- Called ‘The Inheritance of Acquired Characteristics’
- Stated that characteristics which develop during an organisms lifetime can be passed onto the next generation
- E.g. If two parents got ripped in the gym, Lamarck believed this characteristic would be passed onto their offspring (i.e. their baby would have a 6 pack)
- People found this difficult to believe
Describe Darwin’s theory
- Developed ‘natural selection’ after journey to the Galapagos islands
- Stated that small changes in organisms took place over a very long time
- All organisms in a species vary and therefore some are more likely to survive (natural selection).
- Those that are best adapted breed and pass on their characteristics
- Darwin did not know about genes. We can now say that the best adapted organisms survive to breed and are the ones that pass their genes onto the next generation
Summarise the sequence of Darwin’s theory of evolution/natural selection
- Best adapted
- Survive
- Breed
- Pass on genes (Darwin didn’t know this)
Why was Darwin’s theory of evolution only gradually accepted?
- It challenged the idea made all the plants + animals on Earth (Creationism)
- Mnay scientists were not convinced because there was not sufficient evidence
- Darwin could not explain variety or inheritance. (No genetics until 50 years later)
- Had shown difference in finches on Galapagos islands during lifetime due to environmental factors but couldn’t explain inheritance.
Why will individual organisms show a wide range of varitation?
Because of differences in their genes
Summaries the the sequence of natural selection (modern)
Mutation
Variation
Best adapted
Survival
Breed
Genes passed on to offspring
What will all organisms the the population compete for?
- Food
- Shelter from predators
- Mates
What types of organisms are most likely to survive?
Those with characterists best suited to the environment.
The ‘fittest’ (survival of the fittest)
Does a good adaptation guarantee survival?
No!
An organism is only ever ‘more likely’ to do something (e.g. breed)
What are mutations?
A change in the genetic material/genes of an organism.
When might a mutation be passed on to an organism’s offspring?
If the mutated gene controls a characteristic which makes the organism better adapted to its environment
When might mutations be particularly important in natural selection?
If the environment changes.
E.g. Some rabbits mutated a gene giving them immunity to myxomatosis. They survived whilst most of the rabbits in the UK died.
Complete the sentence:
Mutations are not always…
…advantageous
