6 Old and new species Flashcards
What are fossils?
the remains of organisms preserved in rocks, ice and other places from thousands/millions of years ago
What are the time scales for the evolution of life?
- a thousand years
- a million years
- a billion years
- 10 to the 3
- 10 to the 6
- 10 to the 9
What are the four main ways a fossil is formed?
- from hard parts of an animal
- when an animal which has died does not decay (preserved where one or more of the conditions needed for decomposition aren’t present)
- harder parts of the animal or plant are replaced by other minerals
- some not from actual organism, but from traces they have left behind
What are examples of fossils formed from the hard parts of an animal?
- bones
- teeth
- claws
- shells
How do animal and plants which have not decayed form?
one or more of the conditions needed for decay aren’t there…
- little or no oxygen present
- poisonous gases may kill off bacteria which cause decay
- temperature too low for decay to take place
- Then they may be preserved in ice-rare-can visualise traits and also extract DNA to compare to modern organisms
How long does a fossil of harder animal/plant parts replaced by other minerals take to form?
- a long period of time
- most common fossil
What are examples of fossil traces left behind by organisms?
- fossil footprints
- burrows
- rootlet traces
- droppings
Why is there an incomplete fossil record?
- many of the earliest forms of life were soft-bodied organisms (left no trace)
- most organisms that died did not become fossilised-right conditions are rare
- many fossils formed in rocks have been worn away by geological activity
- still many we haven’t found
Explain how a common fossil is formed?
- animal dies and falls to ground
- flesh rots, leaving the skeleton to be covered in sand or soil and clay before it is damaged
- protected, over millions of years, the skeleton becomes mineralised and turns to rock-the rocks shift in the earth with fossil trapped inside
- eventually, the fossil emerges as rock and erosion takes place
How can the fossil record help us?
helps us to understand how much organisms have changed since life developed on earth e.g. horses
also shows us which animals have not changed much due to being perfectly adapted to environment which has not changed much e.g. sharks
What is extinction?
the permanent loss of all the members of a species
What are the three main causes of extinction?
Caused by a change in the environment…
- new predators
- new diseases
- new, more successful competitors
How can new predators cause extinction?
- can wipe out unsuspecting prey animals quickly
- prey don’t have adaptations to protect themselves
- new predators may evolve or an existing one may move into new territory
- can be due to human intervention e.g. brown tree snake form Australia to Guam after WW2 which caused rapid extinction of many bird species
How can new diseases cause extinction?
- caused by microorganisms
- can bring species to point of extinction
- most likely to happen on islands where the whole population is close together
- e.g. tasmanian devil- rare animals dying from a new form of infectious cancer, attacking and killing them quickly
How can successful competitors cause extinction?
- new mutations can give one type of organism an advantage over the other
- sometimes new species can be introduced into an area by mistake
- new,more successful competitor can take over from the original animal and make it extinct
- e.g. rabbits in Australia are eating so much and breeding so fast that they are wiping out native species
