3.2 Origins of biodiversity

Question 1

What did Charles Darwin believe in his “Theory of Evolution”?

Answer 1

All species of living things which exist today, and many more which are now extinct, have evolved from simple life forms which first developed more than 3000 mya.

Question 2

What is the definition of “speciation”?

Answer 2

Speciation is the process by which new species form (gradually.. over time)

Question 3

How is Natural Selection a driving force for speciation?

Answer 3

• Darwin proposed idea that evolution occurs through natural selection.
• Natural selection is a possible driving force for speciation.
• Process by which change in frequency of genetic traits in population occurs in response to environmental pressure

Question 4

What is the definition of “genes”?

Answer 4

Sections of DNA found in the nucleus of all cells. They are the instructions from which a species if produced.

Question 5

What is the definition of “evolution”?

Answer 5

The cumulative, gradual change in the genetic composition of a species over many successive generations, ultimately giving rise to species different from the common ancestor.

Question 6

What is the definition of “evolution”?

Answer 6

Darwin envisaged a branching tree of life with closely related species being close together with a common ancestor on that tree.

Question 7

What are some of Darwin’s Principles?

Answer 7

• Variation within populations
• Overproduction of offspring
• Struggle for existence
• Unequal survival and reproduction rates

Question 8

Explain the process of natural selection:

Answer 8

1. Population of organisms
2. Overproduction of offspring - the more young produced than can survive in a particular habitat
3. Mutations & sexual reproduction produce genetic variation among offspring
4. Limited resources leads to a struggle for existence between offspring
5. Individuals with characteristics most suited to environment are more likely to survive and breed successfully - survival of the fittest
6. Genes which enabled these individuals to survive are then passed on to their offspring (the next generation)
7. Populations changes over time

Question 9

How does natural selection lead to the formation of new species?

Answer 9

Over many generations, if separated, differences between populations become so large that if reunited they will be unable to interbreed
–> A new species is then formed

Question 10

What is the problem with using pesticides and natural selection?

Answer 10

As more pesticide is applied the success will fall as those early survivors (probably immune to the poison), have reproduced and passed on their genes, conferring resistance to the pesticide. The population thus adapts to environmental change.

Question 11

What are the two types of speciation?

Answer 11

• Sympatry - the same geographical area
• Allopatry - separate geographical areas

Question 12

What is “allopatric speciation”?

Answer 12

(Geographic isolation)

When two populations of the same species become geographically (physically) isolated then different environmental pressures may act upon the two populations giving rise to different selection pressures on the two populations.

Question 13

What is “sympatric speciation”?

Answer 13

(Reproductive isolation)

Causes of reproductive isolation include:
- Temporal or seasonal isolation
- Behavioral isolation
- Gametic isolation (gametes may be prevented from fusing)

EG (behavioral isolation)
- Ecological isolation may arise as individuals start to specialize in their feeding or behavioral habits
- Genetic divergence follows
- Eventually the new species will be reproductively isolated

E.g. North American maggot fly: Hawthorns and apples

Question 14

What do tectonic plates do?

Answer 14

• Slip past each other
  Causing earthquakes.
• Move towards each other
  Causes subduction and mountain building.
• Move away from one another
  When plates move apart under the oceans, magma rises to the surface, creating new rock.

Question 15

How does the movement of the plates of the earth’s crust influence evolution and biodiversity?

Answer 15

• Divergence of plates leads to isolation of populations and the separation of gene pools, and the development of distinctive climates. This results in the development of new species, increasing biodiversity.
• Formation of barriers and or land bridges can influence biodiversity
• Volcanic activity/ plate collisions producing islands/ mountains leads to diversity of habitats and evolution of new species.

Question 16

What are the 4 layers of the earth?

Answer 16

• A thin outer crust
• The mantle (mainly solid but just under the crust it is almost molten)
• Outer core (liquid)
• Inner core (solid)