(todo 4.5-7) Natural Selection and Evolution - Paper 1

Question 1

Describe the theory of evolution by natural selection.

Answer 1

1. Individuals in a population show genetic variation.
2. Selection pressures affect the chance of individuals of surviving and reproducing.
3. Individuals with characteristics advantageous under these selection pressures have a better chance of survival and so breeding successfully.
4. Alleles responsible for the useful characteristics are more likely to be passed on.
5. Less well adapted individuals are less likely to survive and reproduce.
6. The beneficial characteristics become more common in the population over time.

Question 2

Explain Charles Darwin’s work on the theory of evolution by natural selection.

Answer 2

Darwin travelled the world for 5 years and noticed variation, leading him to publish ‘On the Origin of Species’ explaining his observations.

Question 3

Explain Alfred Russell Wallace’s work on the theory of evolution by natural selection.

Answer 3

Wallace was working at the same time as Darwin. He independently came up with natural selection, and provided lots of evidence. The two collaborated with and acknowledged each other.

Question 4

What are antibiotics, and how can resistance to them spread among bacteria?

Answer 4

Antibiotics are drugs that are designed to kill bacteria or prevent them from reproducing. A bacterium could become resistant due to a mutation. This trait would spread due to evolution by natural selection, if a host is being treated (providing a selection pressure).

Question 5

How old is the hominid fossil ‘Ardi’, and of what species?

Answer 5

4.4 mya, Ardipithecus ramidus

Question 6

Describe the features of the hominid fossil ‘Ardi’.

Answer 6

• She had an ape-like big toe to grasp branches - suggesting tree climbing.
• She had long arms and short legs - more like an ape than today’s human.
• Her brain size was similar to a chimpanzee’s.
• Her leg structure suggests upright walking, unassisted by hands.

Question 7

How old is the hominid fossil ‘Lucy’, and of what species?

Answer 7

3.2 mya, Australopithecus afarensis

Question 8

Describe the features of the hominid fossil ‘Lucy’.

Answer 8

• She had arched feet, more adapted to walking than climbing, and no ape-like big toe.
• Her limbs were between size expectations for apes and humans.
• Her brain size was slightly more than that of ‘Ardi’ but still similar to a chimpanzee’s.
• Her leg structure suggest she walked upright slightly more efficiently than ‘Ardi’.

Question 9

Describe Richard Leakey’s work on fossils providing evidence for human evolution.

Answer 9

Leakey led a 1984 expedition to Kenya that discovered many Australopithecus and Homo species. “Turkana Boy”, a Homo erectus fossil from 1.6 mya, was much closer to a human (short arms, long legs, legs/feet structure) than an ape - including in brain size.

Question 10

How did Homo habilis contribute to development of stone tools?

Answer 10

Homo habilis, living 2.5 - 1.5 mya, made ‘pebble tools’ by hitting rocks together. These could scrape meat from bones or crack bones open.

Question 11

How did Homo erectus contribute to development of stone tools?

Answer 11

Homo erectus, living 2-0.3 mya, sculpted rocks into more complex tools like simple hand-axes for hunt, dig, chop and scrape meat from bones.