Unit 2 - Speciation (fossils, extinction, speciation) Flashcards
What is a fossil
Fossils are remains of organisms from many years ago, preserved in rock.
What is mineralisation?
Where the hard parts of animals/plants are replaced with minerals over long periods of time.
Explain how mineralisation works
- Mud and sand fall to the sea bed. As layers build up, heat and pressure convert the sediment to rocks
- Dead animals sink to the sea floor. The soft part decompose or are eaten away, leaving only the skeletons
- The skeleton is buried by sediment and is gradually mineralised so it turns into stone
- Over millions of years, more fossils are formed - upper layers of rock contain more recent fossils
- As the sea retreats, or the rock layers are pushed up, the rock becomes exposed to the elements
- Erosion by wind, rain, earthquakes and human activity gradually erode the rock layers, exposing the fossils.
What is an ammonite?
What is a trilobite?
[Image result for trilobite]
Name the 3 ways in which fossils can be made
- From gradual replacement by minerals (most common)
- From casts and impressions
- From preservation in places where no decay happens
Give some reasons why extinction can occur
- Because a specicies couldn’t evolve quickly enough
- The environment changes too quickly
- A new predator kills them all
- A new disease kills them all
- They can’t compete with another species for food
- A catastophic event occurs and kills them all
- A new species develops (speciation)
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What is speciation
The development of a new species
When does speciation occur?
When populations of the same species become so different they can no longer breed together to produce fertile offspring
Give an example of when speciation may occur
When a physical barrier splits a population (eg mountains, trees, floods, earthquakes) meaning that the conditions in the different places may vary, meaning the populations adapt to the environment and the development of a new species occurs
