Topic 4 - Natural Selection and genetic modification - inheritance (4.1B-4.6B)

Question 1

Describe the process of natural selection (4 marks)

Answer 1

Different individuals within a biological population display genetic variation
Individuals with genes that can make them better adapted to the environment will have a greater chance of survival
Individuals with the best chance of survival will be most likely to breed successfully,
These favourable characteristics are passed onto next generations and eventually all members within the population will acquire these characteristics.

Question 2

Evolution Definition

Answer 2

Evolution is the gradual change of the inherited characteristics of biological populations over time.

Question 3

Explain antibiotic resistance. (6 marks)

Answer 3

A random mutation occurs in the DNA of individual bacterial cells.
The mutation protects the bacterial cell from the effects of the antibiotic - it becomes antibiotic resistant.
Bacteria without the mutation die when the antibiotic is present
Antibiotic resistant bacteria survive and can reproduce with less competition from non-resistant bacterial strains.
The genes for antibiotic resistance are passed to the offspring.
Over time the whole population of bacteria becomes antibiotic resistant because the antibiotic resistant bacteria are best suited to their environment.

Question 4

Explain how pentadactyl limbs are evidence for evolution

Answer 4

Modern limbs show the same basic pentadactyl structure. They have long bones supporting carpal bones and phalanges. This suggests that the human and the “x” evolved from the same ancestor. The differences between the limbs can be explained by evolution and different environments. The limbs have developed in different ways because they have adapted to different uses.

Question 5

Explain the theory of speciation, from Wallace

Answer 5

Populations of the same species can become isolated from one another due to the formation of a physical barrier – this is known as geographic isolation
The environment will be different on either side of this physical barrier, for example a different climate.
The environmental differences on either side will provide different natural selection will cause a different set of characteristics to become more common in the two isolated populations
Over many generations, individuals from the two populations will have become so distinctly different that they will no longer be able to interbreed and produce fertile offspring
The two populations are now separate species

Question 6

Explain why the fossil record is incomplete (2 marks)

Answer 6

Soft tissue organisms do not form fossils

Some fossils are still yet to be found

Question 7

What is meant by speciation (2 marks)

Answer 7

The formation of new species due to geographical isolation

Question 8

what is a phenotype

Answer 8

the characteristics an organism holds because of their genotype

Question 9

B4.5 Describe the evidence for human evolution based on stone tools, including:
b) how these can be dated from their environment. (carbon dating, layering and complexity)

Answer 9

Simpler tools are more likely to be older than more complex tools.
The deeper the layer of rock, the older it tends to be.
carbon dating - Plants absorb carbon dioxide and animals eat these plants. The concentration of carbon-14 present in the animal can show how long ago it was alive as carbon-14 has a specific half life and can therefore be compared.

Question 10

Describe how genetic analysis has led to the suggestion of the
three domains rather than the five kingdoms classification
method

Answer 10

Research on genes shows prokaryotes need to be split into two groups as some bacteria have genes that function more similarly to eukaryotes

Question 11

Describe the 3 domain system

Answer 11

Eubacteria, Eukaryota, Archaea.

Question 12

Describe Ardi

Answer 12

Structure of feet suggests she climbed trees
Longer arms and legs (more ape-like)
Brain size the same size as chimpanzees

Question 13

Describe Lucy

Answer 13

• Had arched feet which were more for walking than climbing
• Sizes of arms and legs similar to apes and humans
• Brain slightly larger than Ardi
• Leg bone structure suggests that she walked upright and more efficiently

Question 14

Describe the fossils that leakey found

Answer 14

Longer legs and shorter arms, like humans
Larger brain sizes than Lucy and Ardi
Best adapted to walking upright