Evolution

Question 1

What does Darwin’s theory of natural selection state?

Answer 1

All species of living things have evolved from simple life forms that first developed more than three billion years ago.

Question 2

How evolution occurs by natural selection:

Answer 2

• individuals within a species show genetic variation due to genetic mutations/difference in their genes.
• individuals with characteristics that make them better adapted to the environment have a better chance of survival and are more likely to breed successfully.
• so the genes that are responsible for the useful characteristics are more likely to be passed on to the next generation

Question 3

Causes of extinction

Answer 3

• environment changes too quickly
• new predators
• new disease
• new, more successful competitors
• a catastrophic event
• a new species develops

Question 4

What were Lamarck’s ideas?

Answer 4

• if a characteristic was used a lot by an organism then it would become more developed during its lifetime
• he believed that acquired characteristics would be passed on to the next generation

Question 5

How are fossils formed?

Answer 5

• Gradual replacement by minerals: things like teeth, bones etc, which don’t decay easily, last a long time when buried. Eventually replaced by minerals, for making a rock-like substance shaped like the original hard part. Surrounding sediments also turn to rock but fossil stays distinct
• Cast and impressions: sometimes fossils are formed when an organism is buried in a soft material like clay. Clay hardens around it and the organism decays, leaving a cast do it self. Footprints can also be pressed, leaving an impression when it hardens.
• Preservation in places where no decays happens: in amber, there’s not oxygen or moisture; in glaciers, it’s too cold; peat bogs are too acidic.

Question 6

Speciation arise as a result of:

Answer 6

• Isolation: two populations of a species become geographically separated.
• Genetic variation: each population has a wide range of alleles
• Natural selection: in each population, the alleged that control the characteristics which help the organise to survive are selected
• Speciation: the populations became so different that successful interbreeding is no long possible

Question 7

What are fossils?

Answer 7

The preserved remains of organism from many thousands of years ago, which are found in rocks

Question 8

Why was Darwin’s theory controversial?

Answer 8

• went against common religious beliefs about how life in earth develops, it was the first plausible explanation for our own existence without the need for a creator
• Darwin couldn’t give a good explanation why these new, useful characteristics apparent for exactly how individual organism passed on those beneficial characters to their offspring. He didn’t know about genes.
• there wasn’t enough evidence to convince many scientist because not many other studies had been done into how organism change over time

Question 9

What do fossils tell us?

Answer 9

How much or how little organism have changed