Fossils, speciation and extinction

Question 1

Why are fossils so useful?

Answer 1

If well preserved they show what creatures have been dead for millions of years. They provide the evidence that they lived so long ago

Question 2

What are fossils?

How many ways do they form in rock?

Answer 2

Remains of plants and animals, form many years ago found in rocks. 3

Question 3

Gradual replacement by minerals is one way of fossils forming. How does this happen?
Decay
Minerals
Surrounding area

Answer 3

After the soft material decays teeth, bones and shells are left, lasting longer when buried.
They are eventually replaced by minerals as they decay forming a rock like substance shaped like the original hard bone (part).
The surrounding sediment also turns to rock and the fossil stays distinct inside, to eventually be discovered.

Question 4

What are the three ways fossils form?

Answer 4

Gradual replacement by minerals
From casts and impressions
Preservation in the places where no decay happens

Question 5

Fossils form from casts and impressions. How does this happen?
In what…

Answer 5

When an organism is buried in soft materials like clay, the clay later hardens around the organism as it decays leaving a cast of itself.

Question 6

Give two examples of casts in the environment…

Answer 6

Burrows or plant roots

Question 7

Give an example of a cast made my a human used for research present day…

Answer 7

Footprints made in mud and other soft materials leave an impression when hardened.

Question 8

Why does preservation happen?

Answer 8

Because the organism doesn’t decay

Question 9

How does preservation happen?

Microbes

Answer 9

There is no oxygen or moisture, or it’s not warm enough or the right pH so decay microbes can’t survive.

Question 10

Give three examples of where preservation happens, and how this area stops microbes surviving….

Answer 10

Amber, fossilised resin, or tar pits have no moisture or oxygen for decay microbes to survive.
They van’t survive in glaciers where it’s too cold for them to work.
Peat bogs are too acidic for the microbes to survive.

Question 11

What do fossils show us about the organisms today?

Answer 11

How they evolved to become that organism, it’s adaptations over the millions of years.

Question 12

What are some hypotheses for the origin of life?
Soup
Space

Answer 12

Primordial Swam, electric shocks may be involved, or under the sea, containing proteins and nutrients, forming simple molecules, building into organisms.
Simple organic molecules brought to Earth on comets, turning more complex to then form simple life forms.

Question 13

Why can’t the theories of how life started be proved?

Why is this?

Answer 13

There is a lack of reliable and valid evidence
It is believed many of the earlier organisms were soft bodied and therefore did not leave fossils as they decayed with no imprint, mineral replacement or preservation. The fossil record is incomplete.

Question 14

What is a physical reason for the lack of fossils from ancient life forms?

Answer 14

Any fossils in the rocks may have already been destroyed by tectonic movement meaning the fossils have been crushed or melted.

Question 15

Why does extinction happen? (simple)

Answer 15

If you can’t evolve quickly enough

Question 16

List 6 reasons why species become extinct... (example)
Trees
TRex
Jabs
Bananas
Crater
New

Answer 16

Environment changes to quickly… destruction of habitat
A new predator kill them all .. humans, human introduction
A new disease wipes them out
Can’t compete with another (new) species for food.squirrels
A catastrophic event happens, killing all .. volcano, asteroid
A new species develops - speciation

Question 17

What is speciation?

Answer 17

The development of a new species

Question 18

What is a species?

Answer 18

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

Question 19

When does speciation occur

Answer 19

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

Question 20

What are two causes of speciation?

Answer 20

Natural selection

Isolation

Question 21

What is isolation?

Answer 21

Where populations of species are separated

Question 22

Why does isolation happen? e.g…

Answer 22

Due to physical barriers… floods and earthquakes or mountains can geographically isolate some individuals from the main population.

Question 23

Why do species speciate on different sides of the barriers?

Answer 23

Conditions on either side will be slightly different, climates or food.

Question 24

How does isolation prompt natural selection?

Answer 24

With the different conditions on the side of the barrier other characteristics are needed and will become more common, due to natural selection.

Question 25

Why do different populations show variation?
How does this help them on their side of the barrier?
Suits
Babies
Passing

Answer 25

Because they have different alleles.
Individuals with characteristics better suited to their environments have a better chance of survival and therefore breeding, and successfully, so the alleles, the beneficial characteristics are passed down to the next generation.

Question 26

How does the process of natural selection through alleles stop interbreeding?

Answer 26

Eventually they will have changed so much, the alleles in their DNA, they will not produce fertile offspring.

Question 27

Describe a flow chart of speciation in 4 stages.
Land, spread of animals
Mountains in the middle, separated colonies
Sun on one side of the mountain, clouds on the other
Big ears on one side, fur on the other.

Answer 27

Two populations of the same species live on an island.
Physical barriers separate the populations, mountains.
Populations adapt to the new environments.
They develop into new species with different characteristics due to natural selection.