End Of Unit Questions Flashcards
When do we think life on Earth began?
3.5 billion years ago
How are fossils dated?
Date the rocks the fossils were preserved in as they are the same age
Why are there no fossils of early life forms?
Early life forms were soft bodied and did not leave fossils
What is the shortest way to represent 3billion in numbers?
3 x 10 to the power of 9
How might a new competitor cause the extinction of a species?
The original species may be left with too little to eat
Suggest 2 ways that people can cause the extinction of some species
- hunting them for food
- polluting the environment
- introducing new competitors
- accidentally introducing a new disease
What are the 2 main ideas put forward for the extinction of dinosaurs?
- a giant asteroid colliding with the earth causing natural disasters
- sea ice melting causing sea temps to reduce by 9*c
What is meant geographical isolation?
Two populations becoming separated by some type of landform
What are the stages in speciation?
- Isolation
- Genetic variation
- Alleles selected for natural selection
- Interbreeding not possible
- Speciation is compete
How old is the earth?
4.5 billion years old
