5. Introducing Evolution

Question 1

‘Evolution’ has several meanings, but what is the gist of the word?

Answer 1

gradual development of something

Question 2

What is the biology specific definition of ‘evolution’? When does evolution, therefore, occur?

Answer 2

• changes that occur in living organisms over many generations
• when heritable characteristics of a species change

Question 3

Has the theory of evolution been proved?

Answer 3

• no!

- but there is very strong evidence

Question 4

What can happen to populations within a species? What happens if this occurs?

Answer 4

• they can become separated and unable to breed with each other (because of geography)
• they evolve differently and their characteristics diverge

Question 5

How long does it take for populations of the same species to develop different such different characteristics that they can no longer interbreed? What has happened when this is the case?

Answer 5

• but thousands of years or more

- the two populations are said to be different species (if they can no longer interbreed)

Question 6

What do taxonomists do?

Answer 6

classify living organisms into species

Question 7

What do taxonomists argue about (not a joke)?

Answer 7

whether populations in different geographical areas are part of the same species or are different species

Question 8

Why do the arguments between taxonomists occur?

Answer 8

there is continuous variation in the amount of difference to populations

Question 9

What idea does evolution not fit with?

Answer 9

creationism - distinct species being created and not evolving

Question 10

How many groups of vertebrates have limbs? What are the names of the groups?

Answer 10

4:

• amphibians
• reptiles
• birds
• mammals

Question 11

Of the vertebrates that have limbs, how are the limbs used?

Answer 11

variety of ways:

• walking
• jumping
• swimming
• climbing
• digging

Question 12

Vertebrates (with limbs i.e. not fish) use their limbs in a variety of different ways. What is the same in all of them?

Answer 12

the basic bone structure

Question 13

What is the vertebrate limb structure known as?

Answer 13

the pentadactyl limb

Question 14

What is the most plausible explanation for the pentadactyl limb?

Answer 14

all vertebrates share an ancestor that had pentadactyl limbs

Question 15

If many different vertebrates evolved from one ancestor with the pentadactyl limb, how come the limbs developed in wildly different ways? What type of evolution is this?

Answer 15

• the vertebrates adopted different types of locomotion (movement) so the limbs developed differently to suit the type of locomotion
• adaptive radiation

Question 16

What is adaptive radiation?

Answer 16

• the diversification of a group of organisms into forms filling different ecological niches (dictionary definition not IB)

Question 17

What are homologous structures?

Answer 17

structures (like the pentadactyl limb) that have evolved from the same part of a common ancestor

Question 18

What would call a ‘structure that has evolved from the same part of a common ancestor’?

Answer 18

a homologous structure

Question 19

What are the features of a homologous structure?

Answer 19

• similarities of structure

- despite the differences in function

Question 20

Can homologous structures be explained in any way but evolution?

Answer 20

• not really

- (creationism)

Question 21

Draw a diagram of a pentadactyl limb structure. (p63)

Answer 21

-

Question 22

Give some examples of organisms with the pentadactyl limb structure.

Answer 22

bat, porpoise, anteater, human, mole, horse