Old and New Species

Question 1

How old do scientists think the Earth is?

Answer 1

4500 million years old

Question 2

How long ago do scientists think life on Earth began?

Answer 2

3500 million years ago

Question 3

Where are fossils found and how does this help us date them?

Answer 3

They are found in rocks

We can date rocks, therefore we can date fossils

Question 4

What are the two main theories for how life on earth developed?

Answer 4

It developed due to the conditions on Earth

Simple life forms arrived from another planet

Question 5

How can fossils be formed?

Answer 5

• From the hard parts of an animal that do not decay easily e.g. bones, teeth
• From the parts that have not decayed because some of the conditions for decay are absent e.g. being preserved in ice
• When parts of the organism are replaced by other materials, such as minerals, as they decay
• As preserved traces of organims e.g. footprints, burrows

Question 6

Why did most organisms that died not leave a fossil?

Answer 6

Because the exact conditions for fossil formation were not present

Many early life forms had soft bodies so few traces were left behind

Question 7

Why are some fossils destroyed over time?

Answer 7

Due to geological activity which breaks them up or wears them away

Question 8

What does extinction mean?

Answer 8

That a species which once existed has completely died out

Question 9

What does extinction always involve?

Answer 9

A change in circumstances (that the species can’t adapt successfully to)

Question 10

What factors can cause extinction?

Answer 10

• A new disease may kill the entire species
• The environment changes over geological time
• New diseases introduced
• A new predator may evolve or be introduced
• A new competitor may evolve or be introduced
• A single catastrophic event may occur, destroying the habitat/species
• Natural changes in the species over time

Question 11

What are the biggest influences on species survival?

Answer 11

Changes in enviroment

Question 12

What specific environmental change threatens species in the present day, and has also done so in the past?

Answer 12

Climate change

Question 13

What changes might climate change cause?

Answer 13

Making it too hot/cold

Making it too wet/dry

This could result in a species’ food supply being reduced and it not surviving

Question 14

What type of extinctions do fossil records show have occured?

Answer 14

Mass extinctions on a global scale

Question 15

What types of mass extinctions on a global scale have occured?

Answer 15

• The habitat a species lived in was destroyed by catastrophic events such as a major volcanic eruption
• The environment changed dramatically following a collision between a giant asteroid and Earth

Question 16

Why does nobody know why the dinosaurs became extinct?

Answer 16

Because there were no scientists there at the time

(Or anyone else…)

Question 17

What theories do scientists have for why the dinosaurs became extinct?

Answer 17

• The collision of a giant asteriod caused huge fires, earthquakes, landslides, and tsunamis. The dust which rose masked the Sun causing darkness and lowing temperatures. This meant that plants could not grow.
• The exctinction was a slower process due to sea ice melting and cooling the sea tempertature by about 9°, therefore there was less plankton and the food chain collapsed as there was less food available

Question 18

What is geographical isolation?

Answer 18

When two populations become physically isolated by a geographical feature

Question 19

What can cause geographical isolation?

Answer 19

• An island becoming seperate from the mainland
• A new river seperates two areas
• Mountain ranges
• Old craters

Question 20

What is speciation?

Answer 20

The formation of a new species

Question 21

Describe the process of speciation

Answer 21

• New species can occur following the seperation of two populations, such as by geographical isolation
• Each population has a wide range of alleles that control their characteristics. This is genetic variation
• Natural selection will occur in each population. The alleles that control the characteristics which help the organism survive are ‘selected’. The organisms with these alleles survive and breed
• If the environment, competitors, food supply, and predators are different for each population they will evolve differently
• Speciation has occured when the populations can no longer successfully interbreed

Question 22

Summarise the process of speciation

Answer 22

Isolation

Genetic variation

Alleles selected

Interbreeding no longer possible

Speiciation

Question 23

What factors affecting seperated populations can lead to speciation?

Answer 23

Different…

• Environment
• Competitors
• Food supply
• Predators