Natural Selection and Genetic Modification

Question 1

Evolution is…

Answer 1

a gradual change in the inherited characteristics of a population over time

Question 2

Ardi
- how many years ago
- skull volume
- 3 details

Answer 2

4.4 million years ago
350 cm cubed
Long, curved big toes that stick out to the side
Long, powerful arms
May have walked bipedally (on 2 legs)

Question 3

Lucy
- how many years ago
- skull volume
- 2 details

Answer 3

3.2 million years ago
400 cm cubed
Fully bipedal, due to slanted femur
Arms shorter than Ardi, big toe doesn’t point out

Question 4

Leakey’s discovery
- how many years ago
- skull volume
- 3 details

Answer 4

1.6 million years ago
850 cm cubed
Large increase in skull volume
Provides evidence of humans originating in Africa (like Lucy and Ardi)
First hominin species to leave Africa (died out)

Question 5

Stone tools

Answer 5

Development of stone tools provides evidence for evolution
These can be dated from their environment
Can radiometrically date the rock that is layered around the tool

Question 6

Natural selection

Answer 6

Occurs when variations that make some better at coping with environmental change than others mean that these are more likely to survive to reproduce and pass on the characteristics

Question 7

Explain Darwin’s theory of evolution by natural selection

Answer 7

1) individual organisms within a particular species show a wide range of variation for a characteristic
2) individuals with characteristics most suited to the environment are more likely to survive and to breed successfully
3) the characteristics that have enabled these individuals to survive are then passed on to the next generation

Question 8

Explain how the emergence of resistant organisms supports Darwin’s theory of evolution including antibiotic resistance in bacteria

Answer 8

1) random mutations occur in the genes of individual bacterial cells
2) some mutations protect the bacterial cell from the effects of the antibiotic
3) bacteria without the mutation die or cannot reproduce when the antibiotic is present

Question 9

Describe the work of Darwin and Wallace in the development of the theory of evolution by natural selection and explain the impact of these ideas on modern biology

Answer 9

Darwin - Spent 5 years on a voyage around the world studying different species (Galapagos Islands e.g. Finches, tortoise) and discovered that ones with variations in characteristics better adapted to their environment were more likely to survive to reproduce
Wallace - Gathered evidence from around the world to support the theory, most known for studying warning colouration in animals

Question 10

Darwin and Wallace impact on modern biology

Answer 10

Contradicted commonly held religious views that God created the world, animals and humans

Question 11

How does the pentadactyl limb suggest evolution

Answer 11

Many vertebrates have a very similar bone structure despite their limbs looking different from the outside. The pentadactyl limb (5 fingered) suggests that many vertebrates are descended from a common ancestor. This provides evidence for the theory of evolution

Question 12

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

Answer 12

Until the development of genetic analysis, organisms were classified on their observable characteristics. With the development of the idea of evolution of species, the classification system was adjusted to try to show how closely organisms were related by evolution. This led to the understanding that some organisms look similar but are not closely related. Genetic analysis then started to show that some relationships in the kingdom system were incorrectly identified. This is because the characteristics were similar due to adaptation to the same environment rather than inheritance. Similar DNA means similar inheritance as the DNA is not changed by the environment.

Question 13

What is genetic engineering?

Answer 13

A process which involves modifying the genome of an organism to introduce desirable characteristics

Question 14

What is selective breeding?

Answer 14

The process in which humans control the breeding of animals or plants with a desirable trait in order to produce offspring with that particular trait

Question 15

Steps of selective breeding

Answer 15

1. Breed together the individuals with the desired trait - Only works if there is genetic variation for that trait
2. Choose the offspring with the desired trait and breed them
3. Repeat for many generations

Question 16

Tissue culture is…

Answer 16

Growing cells or tissues in either a liquid containing nutrients or a solid nutrient medium

Question 17

Steps of tissue culture in plants

Answer 17

Plants
1. Take a tiny piece of plant tissue from a rapidly growing area
2. Prepare a solid medium containing sugars, nutrients and growth hormones
3. Place the tiny piece of tissue on the sterile solid medium
4. Store in a warm place in bright light to encourage cell division, growth and differentiation

Question 18

Steps of tissue culture in animals

Answer 18

Animals
1. Separate the cells in a small piece of tissue by mashing or using enzymes
2. Prepare a solid or liquid growth medium containing sugars and nutrients
3. Pour a thin layer of cells onto a sterile solid medium or suspend the cells in a sterile liquid medium
4. Store the cells in a warm place to encourage cell division and growth

Question 19

Advantages of tissue culture in medicine

Answer 19

Medicine
- Growing replacement organs
- Studying how cells communicate with each other
- Study viruses by infecting cells and researching how to stop them
- Study tumours, create tumours and try different drugs to kill them

Question 20

Advantages of tissue culture in plant breeding programmes

Answer 20

Plants
- Clone plants to prevent extinction of plants
- Clone genetically modified plants
- Clone plants that are difficult to grow from seeds

Question 21

Benefits of genetic engineering

Answer 21

Medicine
- Can be used to mass-produce hormones (e.g. insulin)
Agriculture
- Can be used to genetically modify crops to have a higher yield or improve a quality (e.g. drought resistant). This would help developing countries
- Can be used to genetically modify crops to produce their own pesticide (BT corn)

Question 22

Risks of genetic engineering

Answer 22

• A gene could spread to other plants such as weeds which could increase their yield or qualities
• Often more expensive to buy and produce than regular plants
• Producing pesticide could lead to pests becoming resistant
• Could cause allergic reactions
• Unethical to interfere with nature

Question 23

Benefits of selective breeding

Answer 23

• Increase yield of crops or livestock
• Can make plants or livestock can be bred to be resistant to disease

Question 24

Risks of selective breeding

Answer 24

• Can result in health problems for organisms (e.g. chickens with so much meat they can’t walk)
• Causes lack of variation within a breed (disease could wipe out a breed), no variations in alleles
• Inbreeding means that there is an increased chance of organisms inheriting harmful genetic defects (less chance of resistant alleles being presented in a reduced gene pool)

Question 25

Stages of genetic engineering

Answer 25

1. Cut out the gene for insulin from a cell
   
   2. Use restriction enzyme to cut out the gene from the chromosomes
   3. Expose sticky ends - unpaired bases on the gene
   4. Use restriction enzyme to cut the plasmid to make space for insulin gene. Cut gap in the plasmid DNA using the same restriction enzymes so we get the same sticky ends
      
      5. Mix them together and use the ligase enzyme to stick them together

Question 26

Explain the advantages and disadvantages of genetic engineering to produce GM organisms including the modification of crop plants, including the introduction of genes for insect resistance from BT into crop plants

Answer 26

Pros
- Toxic to insects that try to
eat the plant
- Doesn’t harm humans
- Increases yield
Cons
- Expensive for farmers to buy
GM seeds
- If wild plants pick up the BT
toxin gene
- Insects evolve resistance

Question 27

Explain the advantages and disadvantages of agricultural solutions to the demands of a growing human population, including use of fertilisers and biological control

Answer 27

Advantages
- Increased yield means farmers are getting more crops from their seeds meaning more food is made
Disadvantages
- Some don’t want to eat BT products, possible allergies
- More expensive to produce
- Could be unethical to tamper with nature