Origins of Biodiversity

Question 1

What is speciation?

Answer 1

The gradual change of a species over a long time.

Question 2

How does speciation occur?

Answer 2

When populations of the same species become separated, they cannot interbreed and if the environments they inhabitat change they may start to diverge and a new species forms.

Question 3

How can humans speed up speciation?

Answer 3

Artificial selection of animals and plants and by genetic engineering.

Question 4

What supports the theory of evolution?

Answer 4

• Each individual is different as they are made up of different genes
• Each will be slightly differently adapted to their environment
• Resources are limited for any population and there will be competition for these resources. Some are better adapted and so will be more successful. They will survive and breed and pass on their genes.
• Over time these changes show and the whole population gradually changes.

Question 5

How do species become isolated?

Answer 5

Geographically, so in a lake or island, and also some populations have different mating cycles or their flowers mature at different times.

Question 6

What is a physical barrier?

Answer 6

Something that splits populations physically,

Question 7

Example of a physical barrier leading to speciation:

Answer 7

Large flightless birds only occur on continents that were part of Gondwana (Africa, Australasia and South America. Gondwana land split up millions of years ago and the large flightless birds are not closely related.

Question 8

What are land bridges?

Answer 8

These allow species to invade new areas.

Question 9

What is an example of a land bridge?

Answer 9

North and South America used to be separated but now they are joined by a land bridge, Isthmus of Panama, which allowed species to move from the North to the South, e.g. bears.

Question 10

What do land bridges result from?

Answer 10

Continental drift or sea water level change. There used to be a land bridge connecting England and Europe but now it is the English channel.

Question 11

How has continental drift effected biodiversity?

Answer 11

Continental drift causes continents to shift climate zones. Species globally are forced to adapt which resulted in an increase in biodiversity.

Question 12

Example of continental drift effecting biodiversity?

Answer 12

Antarctica used to have a tropical climate and was covered in forests. Continental drift caused Antarctica to mouth southwards and the forest gradually disappeared and species adapted to the new, ice-covered landscape.

Question 13

How many mass extinctions have there been?

Answer 13

5

Question 14

What do we think may have caused these mass extinctions?

Answer 14

Rapid changes in climates, natural disasters (volcano, meteorite)

Question 15

What do we call animals that can survive well in environments humans create?

Answer 15

Weedy species

Question 16

How are we causing a sixth mass extinction?

Answer 16

• Altering the environment with infrastructure
• Overexploiting other species (fishing, hunting, harvesting)
• Introducing alien species that may not have natural predators
• Polluting the environment

Question 17

What are the two stages of the sixth mass extinction?

Answer 17

Stage 1: modern humans spread over the earth

Stage 2: Agriculture started when there were one to ten million people on the earth

Question 18

How did modern humans begin the mass extinction?

Answer 18

In Australia the megafauna disappeared after the arrival of humans.
In North America the arrival of humans resulted in the hunting and extinction of woolly mammoths.

Question 19

How did agriculture perpetuate extinction?

Answer 19

Humans were no longer in competition with other species or amongst themselves, they could now manipulate the environment for their benefit.
They could exceed the natural carrying capacity.
They focused on using a few species and considered the others pests or weeks.