B2 - Old And New Species Flashcards
What are the ways in which fossils are formed?
- From hard parts that don’t decay easily
- When conditions for decay are absent
- When parts are replaced by other materials as they decay
- As preserved imprints
Why are fossils useful for us today?
They provide us evidence of how life has developed by filling in gaps in the fossil record and teach us how much (or how little) organisms have changed.
Why can’t scientists be certain about how life began on Earth?
Scientists do not have enough evidence as not all remains were preserved and there’s no evidence as to where the first living thing came from.
What is the definition of extinction?
The dying out or termination of a species.
What are the causes of extinction?
- New predators
- New infectious diseases could arise
- Competition with a better adapted species for essential things. e.g. food
What may cause the mass extinction of a species?
- Climate change, such as ice ages
- Volcanic eruptions
- Asteroid impacts
What is speciation?
Speciation is the formation of a new species from a pre-existing one.
What is meant by the term ‘species’?
A group of similar organisms that are geographically isolated, so can’t breed with another species to form fertile offspring.
Explain how new species arise using the term ‘isolation’.
1 • Two or more populations of a species become isolated from each other.
2 • This occurs by GEOGRAPHICAL ISOLATION, where a physical barrier prevents the groups from mixing.
3 • There will be a genetic variation between the organisms in each isolated group.
4 • Different living conditions cause different adaptations
- over time, the proportions of different alleles will change - different mutations
5 • Eventually, sufficient differences will evolve in each population so that they could no longer interbreed to produce fertile offspring.
What is a fossil?
A fossil is the preserved remains or traces of a dead organism.
What are the problems with the fossil record?
- Gaps in the record where no fossils have been found.
- Incomplete parts of the organism.
- The soft parts of the organism are rarely preserved.
- Organisms may have lived in some parts of the world where fossils are rarely formed.
What is genetic variation?
The variation is alleles of genes, both within and among populations.
Why might a species become endangered?
- There is a fall in the number of habitats available for the species to live in.
- There is not enough genetic variation in the population.
According to the Theory of Evolution, how do species evolve?
Species evolve through natural selection, according to the Theory of Evolution.
Why do we have a good evolutionary record of the horse?
The fossil record of their ancestors is complete.
