Extinction and Speciation Flashcards
How does extinction happen?
If something can’t evolve quickly enough.
What does the fossil record contain?
Many species that don’t exist any more these species are said to be extinct.
Name 6 reasons why species can become extinct?
The environment changes too quickly. New predator kills them. New disease kills them. Can't compete with others for food. Catastrophic event kills them. New species develop.
Give a good example of an extinct animal?
Dodos.
Human hunted them.
As well as introducing other animals which ate all their eggs and destroyed the forest they lived in.
What is speciation?
It is the development of a new species.
What is a species?
A group of similar organisms that can reproduce to give fertile offspring.
When does speciation occur?
When populations of the same species become so different that they can no longer breed together to produce fertile offspring.
What is isolation and how does it happen?
Where a population of a species are separated.
Can happen due to physical barriers.
eg floods/earthquakes can cause barries that geographically isolate individuals from main population.
What will conditions be like on either side of the barrier?
Slightly different eg may have slightly different climates.
Because the environment is different on each side, different characteristics will become more common in each population due to natural selection.
How does natural selection lead to speciation?
Each population shows variation because they have a wide range of alleles.
In each population individuals with characteristics that make them better adapted to their environment have a better chance of survival and breed successfully.
Alleles that control the beneficial characteristics are more likely to be passed on to next generation.
Eventually what happens in speciation?
Individuals from different populations will have changed so much they won’t be able to breed with one another to produce fertile offspring.
2 groups will have become separate species.
