Old And New Species Flashcards
(13 cards)
What are fossils?
The remains of organisms from many years ago, which are found in rocks. Fossils provide the evidence that organisms lived ages ago.
How can fossils be formed?
By the hard parts pf an animal which don’t decay such as bones. When an animal does decay after it has died, in glaciers it is too cold for decay microbes to work. Many fossils are formed when harder parts of the animal or plant are replaced by other minerals. Some fossils are traces, which we take impressions of, such as burrows and footprints.
Why is the fossil record incomplete?
Earliest forms of life were soft bodied. Many didn’t fossilise once dead as conditions for fossil rock formations were rare. Many fossils are still to be found.
What does the fossil record help us to do?
Understand how much organisms have changed since life developed on Earth.
How else may fossils have been destroyed?
By geological activity.
Why may animals become extinct?
The environment changes too quickly, a new predator, a new disease, catastrophic event, new species, new competitors.
What is a species?
A group of similar organisms that can reproduce to give fertile offspring.
What is speciation?
The development of a new species.
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?
Where populations of a species are separated.
When a species evolved in insolation and is only found in one place in the world, what is it said to be?
Endemic to that area.
How can isolation occur?
Due to a physical barrier such as floods and earthquakes.
How does speciation occur?
- Conditions on either side of the barrier will be slightly different.
- Because the environment is different on each side, different characteristics will become more common in each population due to natural selection.
- Eventually, individual from the different populations will have changed so much that they wont be able to breed with one another to produce fertile offspring.
- They have become separate species.
