Evolution

Question 1

What is the theory of evolution?

Answer 1

More than 3 billion years ago, life on earth began as simple organisms from which all the more complex organisms evolved

Question 2

What explains how evolution occurs?

Answer 2

Natural selection

Question 3

According to natural selection, why do species show variation?

Answer 3

Individuals within a species show variation because of the differences in their genes

Question 4

How do individuals with better characteristics pass on their characteristics?

Answer 4

1. Individuals with characteristics that make them better suited to the environment have a better chance of survival and so are more likely to breed successfully
2. The genes for the useful characteristics are more likely to be passed on to the next generation

Question 5

Give three reasons why many people didn’t accept Darwin’s theory?

Answer 5

1. It went against common religious beliefs about how life on earth developed
2. Darwin couldn’t give a good explanation for why these new, useful characteristics appeared or exactly how individual organisms passed on their beneficial characteristics to their offspring.
3. There wasn’t enough evidence to convince many scientists

Question 6

What was Lamarck’s theory?

Answer 6

That if a characteristic was a lot by an organism then it would become more developed during its lifetime.
E.g. If a rabbit used its legs to run a lot then it’s legs would grow longer

Question 7

What are fossils?

Answer 7

The remains of organisms from many thousands of years ago

Question 8

What can fossils tell us?

Answer 8

How much of how little organisms have changed over time

Question 9

What are three ways fossils form?

Answer 9

1. From gradual replacement by minerals
2. From casts and impressions
3. From preservation in places where no decay happens

Question 10

Describe how fossils form from gradual replacement by minerals?

Answer 10

• Things like teeth, shells, bones etc… which don’t decay easily, can last a long time when buried
• They’re eventually replaced by minerals as they decay, forming a rock-like substance shaped like the original part
• the surrounding sediments also turn to rock, but the fossil stays distinct inside the rock and eventually someone digs it up

Question 11

Describe how fossils form from casts and impressions?

Answer 11

• Sometimes, fossils are formed when an organism is buried in a soft material like clay. The clay later hardens around it and the organism decays, leaving a cast of itself.
• Things like footprints can also be pressed into these materials when soft, leaving an impression when it hardens

Question 12

Describe how fossils form from preservation in places where decay happens? (Peat bogs)

Answer 12

• In amber and tar pits there’s no oxygen or moisture so microbes can’t survive
• In glaciers its too cold for the decay microbes to work
• Peat bigs are too acidic for decay microbes

Question 13

Give 5 reasons why a species would become extinct?

Answer 13

1. The environment changes too quickly
2. A new predator kills them all
3. A new disease kills them all
4. They can’t compete with another species for food
5. A new species develops (speciation)

Question 14

What is a species?

Answer 14

A group of similar organisms that can reproduce to give fertile offspring

Question 15

What is speciation?

Answer 15

The development of a new species

Question 16

When does speciation occur?

Answer 16

When populations of the same species become so different that they can no longer breed together to produce fertile offspring

Question 17

What is isolation?

Answer 17

Where populations of a species are separated

Question 18

Describe how natural selection works

Answer 18

1. Each population shows genetic variation because they have a wide range of alleles
2. In each environment, individuals with better characteristics that make them better adapted to their environment have a better chance of survival and so are more likely to breed successfully
3. So the alleles that control the beneficial characteristics are more likely to be passed on to the next generation