Natural Selection & genetic modification

Question 1

what is evolution?

Answer 1

the slow and continuous change of organisms from one generation to the next

Question 2

How are stone tools dated from their environment?

Answer 2

structural features- simple tools are older
stratigraphy- deeper rock layers are older
carbon-14 dating of parts containing carbon e.g. wood or bone

Question 3

how have stone tools changed over time

Answer 3

homo habilis (2.5-1.5mya)- pebble tools (sharp flakes of stone) to scrape and crack bones
homo erectus (2-0.3mya)- more complex sculpted tools e.g. hand axes used to hunt, dig, chop & scrape bones.
Homo neanderthalis (300000-25000ya) - flint tools, pointed tools, wooden spears
Homo sapiens (200000ya to present)- widely used flint tools. Pointed tools inc. arrowheads, fishhooks, buttons, needles appeared 50000ya.

Question 4

What is the fossil evidence for human-like (hominid) species 4.4mya?

Answer 4

Ardi- Ardipithecus ramidus, found in Ethiopia, apelike big toe for climbing trees, long arms & short legs (like an ape’s), similar brain size to a chimp’s, structure of legs suggests she walked upright, hand bone structure suggests she didn’t use her hands to help her walk like a chimp.

Question 5

What is the fossil evidence for human-like (hominid) species 3.2mya?

Answer 5

Lucy- Australopithecus afarensis, Ethiopia, more human like than Ardi, arched feet for walking (no apelike big toe), size of arms and legs between those of apes and modern humans, brain larger than Ardi’s but still similar in size to a chimp’s brain, walked upright but more efficiently than Ardi (structure of leg bones and feet)

Question 6

What is the fossil evidence for human-like (hominid) species 1.6mya?

Answer 6

Turkana Boy, Homo erectus, Leakey expedition to Kenya, more human like than Lucy, short arms &long legs like humans, brain size larger than Lucy’s (similar to humans’), leg & feet structure suggests that he walked upright better than Lucy

Question 7

What is the cause of genetic variation?

Answer 7

differences in alleles (caused by mutations)

Question 8

How do adaptations allow organisms to survive?

Answer 8

changes to make the organism more suited to its location e.g. warning colours to deter predators

Question 9

How does natural selection allow some members of a species to survive better than others when conditions change?

Answer 9

Individuals in a population show genetic variation which allows some of them to survive selection pressures better. These individuals survive and reproduce, becoming more adapted to the conditions, and eventually form new species.

Question 10

How does bacterial and other organisms’ resistance provide evidence for evolution?

Answer 10

Bacteria develop random DNA mutations which can create new alleles which can sometimes make certain bacteria more resistant to antibiotics (a selection pressure). These bacteria survive, reproduce and pass on the antibiotic resistance allele. Other resistant organisms (e.g. Warfarin-resistant rats) provide evidence for evolution.

Question 11

Which scientists first developed the idea of evolution by natural selection?

Answer 11

Charles Darwin and Alfred Russel Wallace

Question 12

What evidence did Darwin use to support his ideas?

Answer 12

He spent 5 years on HMS Beagle observing plants and animals. He observed variation within species and noticed that those with characteristics most suited to the environment were more likely to survive and that characteristics could be passed on to offspring. He wrote a theory of evolution by natural selection to explain his observations.

Question 13

What evidence did Wallace use to support his ideas?

Answer 13

He observed warning colours used by species e.g. butterflies to deter predators (a beneficial characteristic evolved by natural selection).

Question 14

How has the theory of evolution by natural selection influenced modern biology?

Answer 14

Classification- organisms are now classified according to how closely they are related.
Antibiotic resistance- we understand the importance of finishing a course of drugs to prevent the spread of resistant bacteria and the need to develop new antibiotics to fight newly evolved resistant bacteria.

Question 15

What is the pentadactyl limb and how does it provide evidence for evolution?

Answer 15

A pentadactyl limb is a limb with five digits found in many species. In each of these species the pentadactyl limb has a similar bone structure but different function e.g. human’s hand and bat’s wing. Similarity in bone structure suggests species with a pentadactyl limb have all evolved from a common ancestor that had one.

Question 16

How are species classified into smaller and smaller groups based on characteristics?

Answer 16

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

Question 17

What are the five kingdoms?

Answer 17

Animals, Plants, Fungi, Prokayotes (single-celled organisms without a nucleus), Protists (eukaryotic single-celled organisms e.g. algae.

Question 18

What is genetic analysis?

Answer 18

determining the sequence of DNA bases in different organism’s genes and comparing them

Question 19

Why do biologists classify organisms into 3 domains?

Answer 19

Carl Woese used RNA sequencing to find that some members of the prokaryote kingdom were not as closely related as first thought and proposed this kingdom be split into 2 groups, Archaea and bacteria. In fact, he suggested all organisms should first be divided into 3 domains then subdivided into the other groups.

Question 20

What are the 3 domains?

Answer 20

Archaea- appear similar to bacteria but are actually very different as shown by their DNA and RNA sequences
Bacteria- true bacteria e.g. E. coli & Staphylococcus
Eukarya- all other organisms

Question 21

Why are new breeds and varieties created?

Answer 21

to select for more useful and attractive qualities, such as animals which produce more meat or milk

Question 22

What is meant by a genetically modified organism (GMO)?

Answer 22

An organism whose genome has been modified to introduce desirable characteristics.

Question 23

How is selective breeding carried out?

Answer 23

select organisms with desired chracteristics from existing stock. breed them. select the best offspring and breed them. continue this process over several generations.

Question 24

Describe advantages of selective breeding

Answer 24

Agriculture: cattle have higher meat yields, better meat; sheep have more wool; crops are more productive
Medicine: rats bred with strong or weak alcohol preference to allow researchers to compare differences between these 2 different types including differences in behaviour and the way their brains work.

Question 25

Describe disadvantages of selective breeding

Answer 25

reduces the gene pool and causes inbreeding, which can cause health problems

Question 26

How is tissue culture carried out in plants?

Answer 26

Small pieces of tissue are taken from the meristems of parent plants. The tissue is grown in agar growth medium which contains nutrients and growth hormones. This is done under aseptic conditions to prevent growth of harmful microbes. As tissues produce roots and shoots they are moved to potting compost to continue growing.

Question 27

Why does tissue culture produce many identical cells?

Answer 27

the tissue samples grow by mitosis and plants produced by tissue culture are clones of each other.

Question 28

How is tissue culture carried out in animals?

Answer 28

A sample of the required tissue is extracted from the animal. Cells in the sample are separated using enzymes. They are then placed in a culture vessel and bathed in a growth medium containing nutrients necessary for growth . After several rounds of cell division cells are split up again to encourage further growth. Tissue cultures can be stored for later use.

Question 29

What are the advantages of using tissue culture in medical research?

Answer 29

Experiments can be carried out on tissues in isolation to look at effects of a substance on the cells of a single tissue without complications from the rest of the organism.

Question 30

What are the advantages of using tissue culture in plant breeding programs?

Answer 30

It’s easy
Plants can be grown quickly, in little space and all year round.
Plants are genetically identical clones so lines of clones can be created with the same beneficial features e.g. pesticide resistance.

Question 31

What are the main stages of genetic engineering?

Answer 31

Restriction enzymes recognise specific sequences of DNA and cut the DNA at these points leaving sticky ends. The vector DNA is cut open with the same enzyme. Ligase enzymes join the two pieces of DNA together at their sticky ends forming recombinant DNA. which is inserted into other cells e.g. bacteria if using a plasmid vector.

Question 32

What are vectors?

Answer 32

Something that can be used to transfer DNA into a cell. There are two sorts:

• Plasmids are small circular DNA molecules that can be transferred between bacteria
• Viruses insert DNA into organisms they infect.

Question 33

What are the advantages of genetic engineering?

Answer 33

Crops can be modified to be resistant to herbicides (e.g. Roundup-resistant crops which are resistant to glyphosate)
Bacteria can be genetically modified to produce human insulin. Human genes producing useful proteins can be transferred into sheep and cows (e.g. antibodies used in therapy for arthritis, some cancers and multiple sclerosis) and then extracted from the animal (e.g. from their milk).
Animals with organs suitable for organ transplantation into humans could potentially be produced in future.

Question 34

What are the disadvantages of genetic engineering?

Answer 34

It can be hard to predict the effect of genome modification on an organism- many GM embryos don’t survive and some GM animals have health problems in later life.
There are concerns about growing GM crops. Transplanted genes may get out into the environment (e.g. a herbicide resistance gene could be picked up be weeds, creating a new ‘superweed’ variety). An insect resistant plant could decimate insect populations. GM crops could adversely affect food chains or human health.

Question 35

How are GM crops modified to make them resistant to insect pests?

Answer 35

A bacterium called Bacillus thuringiensis (Bt) produces a toxin that kills harmful insect larvae. The Bt toxin gene is inserted into crops (e.g. corn and cotton) which then produce the toxin in stems and leaves so are resistant to insect pests. This increases crop yields and reduces need for chemical pesticides. The toxin is specific to insect pests so humans and other animals are unaffected. However long-term effects of exposure to the Bt toxin are unknown. There is a danger of insect pests developing resistance which is avoided by the use of other insecicides as well.

Question 36

How can GMOs be used to provide more food?

Answer 36

Crops that are genetically engineered to be resistant to pests or to grow better in drought conditions can increase crop yields. Some crops can be engineered to combat deficiency diseases. For example Golden Rice is genetically engineered to produce a chemical converted to Vitamin A in the body. GMO animals and livestock can be bigger and/or requiring less space or food.

Question 37

What are the disadvantages of using GMOs to increase food security?

Answer 37

Many people argue that poverty not lack of food is a main reason for hunger so more food will not solve the problem. There are fears that companies may become dependent on companies selling GM seeds. Sometimes crops fail due to poor soil so even GM crops will be unable to survive.

Question 38

What is biological control?

Answer 38

Other organisms including predators and parasites are introduced to combat pests e.g. cane toads were introduced to Australia to eat beetles which damaged crops. This decreases damage to crops so increases crop yields and reduces need for chemical pesticides. Biological control can have longer-lasting effects than chemical pesticides and be less harmful to wildlife.

Question 39

What are the issues associated with biological control?

Answer 39

Introducing new organisms may result in the spread of invasive species which out-compete native species. For example, cane toads are now a pest in Australia as they poison native species which eat them.

Question 40

Why do we need to produce more food?

Answer 40

The world’s population is rapidly increasing. Therefore the global food production must increase too so we all have access to enough food that is safe to eat and has the right balance of nutrition (food security).

Question 41

How do fertilisers increase crop yield?

Answer 41

Fertilisers contain minerals essential for plant growth, e.g. nitrates and phosphates, which replace those lost from the soil to previous crops.

Question 42

How can fertilisers damage the environment?

Answer 42

river and lake pollution and eutrophication.