2b.6 - Fossils, Extinction and Speciation Flashcards
1
Q
What is a fossil?
A
The remains of organisms from many, many years ago which are found in rocks
2
Q
How can fossils be made? (3)
A
- Gradual replacement by minerals
- From casts and impressions
- From preservations where no decay happens
3
Q
How are fossils made by gradual replacement by minerals? (3)
A
- Things like bones which don’t decay easily, can last a long time when buried
- They’re eventually replaced by minerals as they decay, forming a rock-like substance shaped like the original hard part
- The surrounding sediments also turn to rock but the fossil stays distinct
4
Q
How are fossils made from casts and impressions? (2)
A
- An organism is formed when an organisms is buried in a soft material like clay. The clay hardens, organism decays and leaves a cast of itself
- Things like footprints can be pressed into these materials when soft, leaving an impression when it hardens
5
Q
How are fossils made from preservation? (3)
A
- In amber and tar pits there’s no oxygen or moisture so decay microbes cannot survive
- In glaciers, it is too cold for decay microbes to work
- Peat bogs are too acidic for decay microbes
6
Q
Where can fossils be preserved? (3)
A
- Amber
- Glaciers
- Peat bogs
7
Q
How can species become extinct? (6)
A
- Environment changes
- New predator kills them
- New disease
- Cannot compete with a new species for food
- A catastrophic event
- A new species developes
8
Q
What is speciation?
A
The development of a new species
9
Q
What is a species?
A
A group of similar organisms that can reproduce to give fertile offspring
10
Q
What is isolation of a species?
A
Where the populations of a species are separated
11
Q
Describe speciation
A
- Two populations of the same species
- Physical barrier separates them (isolation)
- Populations adapt to new environments (natural selection)
- Development of a new species
