Topic 4 - Natural Selection And Genetic Modification

Question 1

Definition of a fossil:

Answer 1

• Any trace of an animals or plant that lived a long time ago.

Question 2

Where are fossils found?

Answer 2

• These are most commonly found in rocks.
• Generally, the deeper the rock, the older the fossil.

Question 3

How do fossils provide evidence for evolution?

Answer 3

• By arranging fossils in chronological order, gradual changes in organisms can be observed.
• It shows how species have evolved and developed over billions of years.

Question 4

How do bacteria provide evidence for evolution?

Answer 4

1) - Bacteria can develop random mutations in their DNA caused by genetic variation. These can create new alleles, which change the bacteria’s characteristics e.g making them more resistant to a antibiotic.

2) - This ability is a big advantage. These bacteria are better able to survive than the non-resistant bacteria and so it lives for longer and reproduces many times.

3) - This leads to the allele for antibiotic resistance being passed on to lots of offspring - this is natural selection.

Question 5

How did Darwin propose the theory of evolution by natural selection?

Answer 5

1) - He noticed that there was variation in members of the same species and:

2) - That those with characteristics most suited to the environment were more likely to survive.

3) - He noticed that characteristics could be passed on to offspring.

Question 6

How did Wallace contribute to the theory of evolution by natural selection?

Answer 6

• He realised that warning colours were used by some species e.g butterflies to deter predators from eating them - an example of a beneficial characteristic that had evolved by natural selection.

Question 7

How have ideas of evolution influenced modern biology?

Answer 7

1) Classification: If all living organisms have descended from a common ancestor, then we’re all related in some away. We now classify organisms based on how closely related they are.

2) - Antibiotic Resistance: We know that you need to finish the course of drugs to prevent resistant bacteria spreading. We know we need to constantly develop new antibiotics to fight newly evolved resistant bacteria.

3) - We understand the importance of genetic diversity and how it helps populations adapt to changing environments. This has led to conservation projects to protect species.

Question 8

Ardi: How old is she, what species was she and where was she found?

Answer 8

• 4.4 million years old
• Species ardipithecus ramidus
• Found in Ethiopia

Question 9

Features of Ardi (4 things):

Answer 9

• Structure of her feet suggested she climbed trees - she also had an ape-like big toe to grasp branches.
• She also had long arms and short legs (like an ape).
• Her brain size was roughly equivalent to a chimpanzee’s.
• The structure of her legs suggested she walked upright. Her hand bone structure suggests that she didn’t use her hands to help her walk like apes do.

Question 10

Lucy: Age, species and location?

Answer 10

• 3.2 million years old
• Australopithecus afarensis
• Ethiopia

Question 11

Lucy’s features:

Answer 11

1) - Arched feet more adapted to walking than climbing, no ape-like big toe.

2) - Size of arms and legs between apes and humans.

3) - Slightly larger brain than Ardi’s, but still similar in size to a chimp’s brain.

4) - Structure of leg bones and feet suggest she walked upright more efficiently than Ardi.

Question 12

Turkana Boy: Age, Location, Species?

Answer 12

• 1.6 million years old
• Kenya
• Homo Erectus

Question 13

Turkana Boy Features:

Answer 13

1) - Short arms, long legs are more human like.

2) - Much larger brain size than Lucy’s (similar to a human’s).

3) - Structure of legs and feet suggested he was even better adapted to walking upright than Lucy.

Question 14

How do stone tools provide evidence for human evolution?

Answer 14

1) - simple stone tools could crack bones open with homo habilis (2.5-1.5 million years ago).

2) - Stone tools became more complex and could hunt, dig, chop etc with homo erectus (2-0.3 million years ago).

3) - More complex tools that were made of flint. Some wooden spears and pointed tools (300,000-25,000 years ago with Homo neanderthalensis).

4) - Widely used flint tools. Pointed tools e.g arrowheads, fish hoods and needles appeared around 50,000 years ago with Homo sapiens.

Question 15

How can tools and fossils be dated?

Answer 15

1) - Looking at the structural features of the tool/fossil. E.g simpler tools are older.

2) - Using Stratigraphy: the study of rock layers. Older rock layers are found below younger layers, so tools or fossils in deeper layers are usually older.

3) - Stone tools are sometimes found with carbon-containing material e.g wooden handle. Carbon-14 dating can be used to date this material.

Question 16

How does the pentadactyl limb provide evidence for evolution?

Answer 16

1) - It is a limb with five digits.

2) - Found in many different species with a similar bone structure but usually a different function.

3) - This similarity in bone structure provides evidence that species with a pentadactyl limb all evolved from a common ancestor.

Question 17

Old Five Kingdom Classification System:

Answer 17

• Animals (fish)
• Plants (grasses)
• Fungi (mushrooms)
• Prokaryotes (single-called organisms without a nucleus)
• Protists (eukaryotic single-called organisms like algae).

Question 18

What are the smaller sub-groups that the three domains are divided into?

Answer 18

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Question 19

Why did the Three Domain system come into place?

Answer 19

1) - Technology has developed further and our understanding of genetics has increased. We can determine the sequence of DNA bases in different organisms’ genes and compare them.

2) - The more similar a gene, the more closely related the organism. This can also be used in RNA sequences.

3) - Using RNA sequencing, Carl Woese found that some members of the Prokaryote Kingdom weren’t very closely related and to split this into two groups.

Question 20

What are the three domains?

Answer 20

• ARCHEA (look similar to bacteria but are different as their DNA and RNA sequences show).
• BACTERIA (true bacteria e.g E. coli).
• EUKARYA (Broad range of organisms like fungi, plants, animals and protists).

Question 21

Define Selective Breeding:

Answer 21

• When humans artificially select the plants/animals that are going to breed so that the genes for particular characteristics remain in the population.

Question 22

Useful Features include:

Answer 22

• Animals produce more meat/milk.
• Crops with disease resistance.
• Dogs with a good, gentle temperament.
• Plants that produce a bigger fruit.

Question 23

Process of Selective Breeding:

Answer 23

1) - Select which animals/plants have the desirable characteristics.

2) - Breed them with each other.

3) - Select the best of the offspring, and breed them together.

4) - Continue this process over several generations and the desirable trait will get stronger and stronger. Eventually, all the offspring will have the characteristic.

Question 24

Selective Breeding in Agriculture:

Answer 24

1) - Genetic variation means that some cattle will have better characteristics for producing meat than others.

2) - To improve meat yields, a farmer could select cows and bulls with these characteristics and breed them together.

3) - After doing this and selecting the best of the offspring for several generations, the farmer would get cows with a very high meat yield.

Question 25

Selective Breeding in Medical Research:

Answer 25

1) - Rats have been bred with either a strong preference for or against alcohol.

2) - This has allowed researchers to compare between the two different types of rats, including differences in their behaviour and in the way that their brains work.

Question 26

Disadvantages of Selective Breeding:

Answer 26

1) - Reduces the gene pool and causes inbreeding.

2) - This can cause health problems because there’s more chance of the organisms inheriting harmful genetic defects when the gene pool is limited.

3) - Because there is not much genetic variation, there is less chance of resistance alleles being present. So, if a new disease comes along and kills one organism, the others are also likely to die from it.

Question 27

Process of tissue culture:

Answer 27

1) - You choose the plant you want to clone based on its characteristics e.g a beautiful flower.

2) - You remove several small pieces of tissue from the parent plant. Take tissue from fast-growing root or shoot tips for the best results.

3) - Grow the tissue in a growth medium containing nutrients and growth hormones.

4) - As the tissues produce shoots and roots, they can be moved to potting compost to carry on growing.

Question 28

Why is tissue culture done under aseptic conditions?

Answer 28

This is done under aseptic conditions to prevent the growth of microbes that could harm the plants.

Question 29

Process of animal tissue culture being used in medical research?

Answer 29

1) - Take a sample of tissue you want to study.

2) - The cells in this sample are separated from each other using enzymes.

3) - They are placed in a culture vessel and bathed in a growth medium containing all the nutrients that they need. This allows them to grow and multiply.

4) - After several rounds of cell division, the cells can be split up again and placed into separate vessels to encourage further growth.

5) - Once the tissue culture has been grown, it can be stored for future use.

Question 30

What does the cells in animal tissue culture being placed in a growth medium containing all the nutrients that they need allow?

Answer 30

This allows them to grow and multiply.

Question 31

Define genetic engineering:

Answer 31

• Involves modifying an organism’s genome to introduce desirable characteristics.

Question 32

Stages of genetic engineering:

Answer 32

1) - The DNA you want to insert (e.g gene for human insulin) is cut out with a restriction enzyme. The vector DNA is then cut open using the same restriction enzyme.

2) - The vector DNA and the DNA you’re inserting are left with complimentary sticky ends. They are mixed together with ligase enzymes.

3) - The ligases join the pieces of DNA together to make recombinant DNA.

4) - The recombinant DNA is inserted into other cells e.g bacteria.

5) - These cells can now use the gene you inserted to make the protein you want (e.g bacteria containing the gene for human insulin can be grown in huge numbers in a fermenter to produce insulin for those with diabetes).

Question 33

Risks of genetic engineering:

Answer 33

1) Growing genetically modified crops: transplanted genes may get out into the environment (e.g herbicide gene picked up by weeds, creating super weeds).

2) - GE of animals: Can be hard to predict what effect modifying its genome will have on the organism - many embryos don’t survive and some GM animals suffer from health problems later in life.

Question 34

How can GMOs be used to provide more food for people?

Answer 34

1) - Crops that are genetically engineered to be resistant to pests or to grow better in drought conditions can help to improve crop yields.

2) - Some crops can be engineered to combat certain deficiency diseases e.g golden rice produces a chemical converted in the body to Vitamin A.

BUT:

3) - Some people argue that people can’t afford to buy this - tackle poverty first.

4) - Countries may become dependent on companies who sell GM seeds.

5) - Poor soil can be the reason why crops fail, and even GM crops won’t survive.

Question 35

Advantages of GE:

Answer 35

1) - GM Crops can be made resistant to herbicides, increasing crop yield.

2) - Bacteria can be GE to produce human insulin.

3) - Transfer human genes that could produce useful proteins into sheep and cows

4) - Animals with organs suitable for organ transplants into humans could be produced in the future.