SB4 - Natural Selection and Genetic Modification ✓

Question 1

SB4a - How do fossil remains provide evidence for evolution?

Answer 1

• Fossil remains of humans can show us the bone structure of previous species
• It also shows how the size of (volume) the skulls, increased over time, suggesting that the size of the brain increased aswell
• The fossils are dated by the layers under the surface that they are

Question 2

SB4a - How do stone tools provide evidence for evolution?

Answer 2

• Stone tools show us what previous species of humans did and what they required tools for
• We can see that over time, they become more sophisticated, going from skining animals/cutting up meat to decorations
• Stone tools are dated by the rock that they are found in.

Question 3

SB4a - Name the species of ‘human’ in order of their evolution, and describe the trend in skull volume.

Answer 3

• Adripithecus (Ardi)
• Australopithecus (Lucy)
• Homo habilis
• Homo erectus
• Homo sapiens

Increasing skull volume over time

Question 4

SB4a - Why is it that fossil evidence may not provide conclusive evidence of human evolution?

Answer 4

• There are gaps in fossil evidence so scientists aren’t sure the species evolved from each other
• Not all fossils have been discovered
• Some fossils are destroyed so we cannot draw a conclusion from it

Question 5

SB4a - What are the two types of evidence for evolution?

Answer 5

• Fossil remains
• Stone tools

Question 6

SB4a - How did Leakey’s findings provide evidence for human evolution?

Answer 6

• He discovered many hominid fossils.
• In 1984, in Kenya, he discovered an almost complete 1.6 million year old skeleton, providing evidence that humans evolved in Africa
• The species was tall and strongly built

Question 7

SB4a - Describe methods used by scientists to date tools

Answer 7

1. Carbon-14 Dating - estimating the age of carbon-containing material found in the tool, whether it’s the handle or the fur
2. Statigraphy - using the layers of sediment as an indication of the age of the tool

Question 8

SB4a - What do Ardi and Lucy tell us about human evolution?

Answer 8

• Ardis 4.4 million years old - she had characteristics both ape-like (long arms, big toes), and human-like (walked upright)
• Lucy, whereas, is more adapted to walking than climbing.

Question 9

SB4b - Describe Darwin’s theory of evolution through natural selection (6 marks)

Answer 9

• variation - most populations of organisms have individuals who are very slightly different to one another due to mutations
• over-production - most organisms produce mroe offspring than will survive to childhood
• struggle for existence - because populations do not generally increases rapidly in size, there therefore must be competition for survival
• survival - those with advantgeous characteristics are more likely to survive this struggle
• advantageous characteristics inherited - better adapted organisms are more likely to reproduce successfully passing on the advantageous characteristics to their offspring
• gradual change - over a period ftime, the proportion of individuals with the advantageous characteristic increase and the poorly adapted characteristic will eventually bel ost

Question 10

SB4b - Using the theory of natural selection, explain why not completing a course of antibiotics is so dangerous.

Answer 10

• The population of bacteria have variation in their resistance to antibiotics.
• The course of antibiotics kill most of the bacteria
• Before the course is finished, the only remaining bacteria are the most resistant
• If the course isn’t completed, the remaining (more resistant) bacteria will reproduce,
• This will produce another generation of highly resistant bacteria which the antibiotic will be less effective against

Question 11

SB4c - Describe how Darwin’s theories were developed.

Answer 11

• After visiting the galapagos islands and seeing differences in the mockingirds of different islands he wondered if spcies changed how they look based on their surroundings
• After reading an essay by Thomas Malthus, he came to the conclusion organisms produce more offspring than could survive and so only the best suited survive
• Wallace wrote a letter to him saying he came to the same conclusion
• They both worked together and Darwin summarised their ideas in a book claled ‘on the origin of species’

Question 12

SB4c - What is the pentadactyl limb and how does this provide evidence for evolution?

Answer 12

• The pentadactly limb is a limb that has 5 main bone structures and this is visible in many organisms from humans to bats to dolphins.
• As we all have the same 5 bone base structure, this suggests that we all have a common ancestor.
• However the layout of these 5 bones changed depending on the surroundings and conditions of a species.

Question 13

SB4d - As you go further down the order of classification, what will happen to the species that are there?

Answer 13

They will have increasingly similar characteristics and genes.

Question 14

SB4d- What is the bi-nomial system?

Answer 14

• Genus + Species

Question 15

SB4d - What are the 5 kingdoms and the characteristics of each of these?

Answer 15

• Animalae: Multicellular. Nuclei are present but no cell walls
• Plantae: Multicellular. Nuclei, chloroplasts and (cellulose) cell walls are present
• Fungi: Multicellular (apart form yeast). live on dead matter. Nuclei and (chitin) cell walls are present.
• Protists: Mostly unicellular. Nuclei and cell walls present
• Prokaryotes: Unicellular. No nucleus, flexible cell walls

Question 16

SB4d - What are the three domains and the characteristics of each?

Answer 16

• Bacteria: (Cells with no nucleus; containing unused sections of DNA)
• Archaea: (Cells with no nucleus or unused sections of genes)
• Eukarya: (Cells with a nucleus and no unused sections of genes)

Question 17

SB4e - Describe the process of selective breeding.

Answer 17

• Firstly, out of the population, you pick the two organisms that most strongly present your desired characteristic
• Breed these two together
• From the offspring choose the two that most strongly show this and repeat
• After a couple of generations, almost all of the offspring will display the characteristic
• This is selective breeding/artificial selection

Question 18

SB4e - What may humans selectively breed an organism for?

Answer 18

• Disease resistance
• Increased yield
• Coping with certain conditions

Question 19

SB4f - What are the uses of tissue culture in agriculture and medicine?

Answer 19

Agriculture

• Producing clones of GMOs
• Growing plants which are going extinct

Medicine

• Testing new medical treatment without any affects on life forms
• Studying viruses as they require host cells to be alive

Question 20

SB4f - What is tissue culture?

Answer 20

• The growing of cells or tissue in a liquid containing nutrients or a solid medium (e.g nutrient agar).
• This forms a callus (bunch of unspecialised cells) which can be differentiated and inserte dinto the body

Question 21

SB4f - Describe the steps of plant tissue culture

Answer 21

1. Tissue removed from the tip of the plant
2. Tissue is placed on a medium containing agar jelly containg plant hormones and nutrients
3. Sample grows into hundreds of tiny, identical plants

Question 22

SB4g - What are the problems with genetically engineering plants?

Answer 22

• Genes may ‘hop’ onto wild plants, making them resistant
• Reduce gene pool
• Very expensive
• Some people think its bad for your health to eat GMOs

Question 23

SB4g - What are the risks of selective breeding?

Answer 23

• Animals may loose an allele through this process.
• This may be needed later on to help them survive/cope
• All the animals become very similar and so any disease that affects one of them, affects all of them
• Unethical as some animals live in conditions that aren’t comfortable (e.g chickens with a lot of meat can’t stand up)

Question 24

SB4h - What are the advantages of plants that produce ‘their own insecticide’ such as Bt toxin to famers?

Answer 24

• It only affects insects that chew it meaning it targets pests specifically
• Higher yield
• Less money spent on insecticides

Question 25

SB4h - What are the disadvantages of plants that produce 'their own insecticide' such as Bt toxin, to farmers?

Answer 25

* Insects such as aphids which suck up sap aren't affected * Insects can develop resistance to the toxin * GM crops that produce the Bt toxin are expensive

Question 26

SB4i - What is a biological control?

Answer 26

When organisms are used to control pests.

Question 27

SB4i - What are the advantages / disadvantages of fertilisers?

Answer 27

**Advantages** * Contain nutrients including nitrogen, phosphorus and potassium that helps crops grow well * Increase crop yield producing more food * Good way to use manure from farms **Disadvantages** * Excess fertiliser can pollute waterways, causing eutrophication * Artificial fertilisers can be expensive to make * Artificial fertilisers reduce soil biodiversity

Question 28

What are the **advantages / disadvantages** of Biological Control?

Answer 28

**Advantages** * Less insecticide wasted * Biological Control is usually specific to the pest * Pest cannot become resistant **Disadvantages** * Biological Control may become a pest in itself * Doesn't guarantee to kill all the pest

Question 29

Pros and cons of GMO

Answer 29

Advantages: *Crops can be GM to be resistant to insects. *More food for people. *Improved crop yield. * Crops might be modified to grow in drought conditions. * Crops can be GM to be resistant to herbicides( chemical that kills weeds). Disadvantages: *Long term exposure to GMO is still unknown and might not be healthy. *Insects or weed can get resistant to it. *Seeds are expensive. * If the resistance to herbicides gene will jump on the weed , then weed will be resistant to herbicides.

Question 30

Pros and cons of selective breeding.

Answer 30

Pros: *Animals can produce more meat or milk. *Crops with desease resistance. *Dogs with good and gentle temperament. *Plants that produce bigger fruit. Cons: *Reduces gene pool. *Inbreeding can cause health problems, more chances to inherit genetic defects. *Ethical issues- as animals are sometimes bred too big to stand. * If a new disease appears, there is no variation in DNA and most likely will kill all of those animals.

Question 31

Biological control pros and cons.

Answer 31

Pests can be controlled by biological control (predators and parasites) to reduce pest number Pros: *Much more Long lasting effect than chemical perticides and be less harmful. Cons: *Introducing new organisms can cause problems as those predators or parasites might become pests themselves.

Question 32

Strawberry fruits, containing seeds, are produced after a flower is fertilised. (ii) Explain why seed production is an advantage to the strawberry plant

Answer 32

*introduces variation into the population,which allows for natural selection of fitter plants/increased chance of the population surviving.

Question 33

Describe 2 ways that stone tools and fossils can be dates to find out how old they are .

Answer 33

compare with other tools / fossils (that have already been dated) (1) • from the (layer of) rock in which they are found / how deep down each was found (1) • radiometric dating / description of radiometric dating (1) • comparing to other finds (of known age) from the same layer (of rock) (1)