IVE - Fossils/Speciation

Question 1

3 examples of what a fossil can be

Answer 1

1. skeleton made of rock
2. impressions made in the ground
3. entire organisms that haven’t decayed

Question 2

1. gradual replacement by minerals

Answer 2

• harder parts of the organism like bones decay much more slowly
• these minerals are sometimes replaced with those in the soil, forming a rock like substance
• these will be the same size and shape as the original
• once they are dug up and separated from rock you can see that they form a perfect model

Question 3

2. casts and impressions

Answer 3

organisms are buried in soft materials like clay, which hardens and conserves the shape/ footprints

Question 4

3. preservation

Answer 4

must happen in conditions wherein no decay happens, like in amber or tar where there is no oxygen available for decomposers.

or in glaciers where its too cold for decomposers to carry out decay

Question 5

why are there gaps in fossil records?

Answer 5

there are large gaps wherein fossils were not discovered - for instance, we still don’t know what early forms of life were like - this is probably because these animals had softer tissues that decayed entirely, also due to ice ages and volacanoes which destroyed fossils. also these were so long ago that they were bound to be destroyed.

Question 6

What is the definition of a species?

Answer 6

A group of genetically similar organisms that are able to interbreed and produce fertile offspring.

Question 7

What is speciation?

Answer 7

When a new species is formed, so different to the original species that they cannot interbreed.

Question 8

Why does speciation occur?

Answer 8

Isolation happens when a physical barrier (such a new river or mountain range) separates two different populations of a given species.

The environment may be different on either side of the barrier. For example the climate or food sources on either side of a mountain range may be different.

Because the populations on either side of the barrier now live in different environments, the two populations experience different selection pressures. This means that different traits become more favourable in each population, and through the process of natural selection, different characteristics will become more common in the two populations.

Question 9

Speciation can also occur due to…

Answer 9

natural selection.

Question 10

who came up with speciation?

Answer 10

Alfred Wallace