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15. Natural selection and extinction Typeit
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Extinction
Scientists say that an organism is extinct when there are members of that species left alive.
Individual members of a species that are poorly adapted to their environment are less likely to survive and reproduce than those that are well adapted, and species will change characteristics over time due to natural .
However, if the environment changes too rapidly, a whole species may not survive the change, and the species may become extinct.
We get our information about extinct species from , which are the remains of dead organisms that have been preserved in rock.
Extinction can be caused by changes such as:
- Changes to the , such as increased temperature and rainfall.
- Loss of habitat; for example, due to deforestation.
- New species of entering the habitat, so that too many of the existing species are eaten.
- New bacteria and viruses which cause .
- New animals or plants that for natural resources and are more successful.
extinction is where many species are wiped out at around the same time. The best known example is the dinosaurs.
This could have been caused by a single catastrophic event; for example:
- Massive volcanic eruptions
- An colliding with Earth
The fossil record is evidence that many species have become extinct since life on Earth first started. Extinction is still happening today and human activities are responsible for a lot of it.
There are many species threatened with extinction now. These are called species, and they may soon become extinct unless humans take steps to protect them.