Section 4 - Natural Selection and Genetic Modification

Question 1

What is natural selection?

Answer 1

Also known as survival of the fittest, the theory that suggests that organisms in a species with more advantageous traits survive longer and produce more offspring than weaker organisms, this means that the advantageous traits become more common within the species.

Question 2

What causes genetic variation?

Answer 2

Differences in the alleles between different organisms in a species.

Question 3

What causes new variations in a species?

Answer 3

Genetic mutations that create new alleles.

Question 4

What are selection pressures, what are some examples?

Answer 4

Things that affect an organism’s chance of survival, those whose variations allow them to survive longer pass on their genes and variations to their offspring. Examples include; predation, competition and disease.

Question 5

How do bacteria provide evidence for evolution?

Answer 5

Bacteria develop random mutations in their DNA like any other organism, this creates new alleles that can change the bacteria’s characteristics. If a bacteria develops resistance to a common antibiotic, it would gain an advantage other the other bacteria. this means it would generate more offspring and the drug resistant allele would become more common

Question 6

What is a fossil?

Answer 6

Any trace of an animal or plant that died a long time ago, generally found in rocks and often the older the rock, the older the fossil.

Question 7

How do fossils provide evidence for evolution?

Answer 7

By arranging fossils in chronological order, they show a gradual change in a species over time, as the species evolves.

Question 8

Who created the theory of evolution?

Answer 8

Charles Darwin and Alfred Russel Wallace.

Question 9

How did Darwin come up with his theory of evolution?

Answer 9

By going on a five year voyage, and investigating plants and animals, he took note of the variations between members in a species and that those with the most beneficial variations for their environment were more likely to survive. He concluded that these variations would gradually change the species over time as the variations were passed on to their children.

Question 10

How did Wallace come up with his own theory of evolution?

Answer 10

He observed various species and noted similarities such as warning colours and that such a characteristic had come about through natural selection.

Question 11

What is suggested by the theory of evolution about how other species evolved along side homo sapiens?

Answer 11

That all organisms have a common ancestor.

Question 12

From fossil evidence, how long ago did the common ancestor of humans and chimpanzees live?

Answer 12

Around 6 million years ago.

Question 13

What is the name given to humans and their ancestors and what are their fossil’s characteristics like?

Answer 13

Hominids, they are a mix of human and chimpanzee

Question 14

What is Ardi? Describe it.

Answer 14

The fossil of an Ardipithecus ramidus, found in Ethiopia, she is 4.4 million years old.
Ardi had a mix of chimpanzee and human features.
The structure of her feet suggested that she climbed trees, an ape-like big toe to grasp branches.
Long arms and short legs.
Similar brain size to a chimpanzee’s.
Structure of her legs suggests she walked upright and the shape of her hand bones suggest that she didn’t use her hands to help her walk.

Question 15

What is Lucy? Describe it.

Answer 15

The fossil of an Australopithecus afarensis, found in Ethiopia, she is 3.2 million years old.
Lucy’s features had a mixture of human and chimpanzee-like features, though was closer to human than earlier species.
Arched feet, more adapted to walking than climbing, and no ape-like big toe.
Arm and leg lengths were between that expected of humans and apes.
Larger brain than previous hominid species, but only a little bigger than a chimp’s.
Structure of her leg bones and feet suggested she walked upright, more efficiently than previous species.

Question 16

Who was Richard Leakey?

Answer 16

The scientist who researched and discovered many hominid fossils, including the Turkana Boy, leading many expeditions to search for these fossils.

Question 17

What is the Turkana Boy? Describe it.

Answer 17

The fossil of a Homo erectus, found in Kenya, he is 1.6 million years old.
He had a mixture of human and ape-like features but was much closer to human than previous species.
Short arms and long legs, in much closer to human proportions than an ape’s.
Brain size was larger than previous hominid species, similar to a human’s and much larger than a chimp’s.
Structure of his leg bones and feet suggest he was even better adapted to walking upright than previous hominid species.

Question 18

How do stone tools provide evidence for human evolution?

Answer 18

Younger Homo species produced more advanced stone tools, this must have required more intelligence to create, so they must have evolved to have larger brains.

Question 19

Describe the relationship between brain size and the average intelligence of a species.

Answer 19

The larger the brain, the higher the average intelligence of a species.

Question 20

What were the stone tools created by the Homo habilis like? When did they exist?

Answer 20

They made simple stone tools called pebble tools by smashing rocks together to make sharp flakes that could be used to scrape meat from bones or crack bones open. The Homo habilis existed around 2.5-1.5 million years ago.

Question 21

What were the stone tools created by the Homo erectus like? When did they exist?

Answer 21

They sculpted rocks into shapes to produce more complex tools, like simple hand-axes. These could be used to hunt, dig, chop and scrape meat from bones. The Homo erectus existed 2-0.3 million years ago.

Question 22

What were the stone tools created by the Homo neanderthalis like? When did they exist?

Answer 22

They produced more complex tools, with evidence of some flint tools, pointed tools and wooden spears. The Homo neanderthalis existed 300000-25000 years ago.

Question 23

What were the stone tools created by the Homo sapiens like? When did they exist?

Answer 23

They created very complex flint tools, pointed tools including arrowheads, fish hooks and needles began appearing around 50000 years ago. The Homo sapiens evolved around 200000 years ago.

Question 24

How can stone tools be dated? What are the drawbacks associated with each method?

Answer 24

Structural features, older tools tend to be less complex than younger tools. Not all tools were created to the same degree of complexity to all the other tools created around the same time.
Stratigraphy, older tools tend to be found in older, lower rock layers. Rock layers can shift, so there is no guarantee on the accuracy of the assessment.
Carbon-14 dating, many tools can be found with carbon-containing material, e.g. a wooden handle. Many of the older tools may not have had handles, and those handles for those that had may have rotted or decomposed to the point that carbon dating would be wildly inaccurate.

Question 25

What is stratigraphy?

Answer 25

The study of rock layers.

Question 26

What is a pentadactyl limb?

Answer 26

A limb that has five digits.

Question 27

How do pentadactyl limbs provide evidence for evolution?

Answer 27

Many species have pentadactyl limbs, e.g. mammals, reptiles, amphibians. In each of these species, the joint has a similar structure, this similarity suggests that species with pentadactyl limbs have all evolved from a common ancestor. Since if they had all evolved from different species it’d be highly unlikely for them to so closely share their structures with other species.

Question 28

What is classification?

Answer 28

A method of organising organisms into groups.

Question 29

How were organisms traditionally classified?

Answer 29

By how close their observable characteristics were, such as appearance and cell structure.

Question 30

What is the Five Kingdoms System, and how does it work?

Answer 30

A classification system, in which all organisms are split into five main groups, called kingdoms; animals, plants, fungi, prokaryotes and protists, then into their phylum, class, order, family, genus and finally their species.

Question 31

How are organisms classified now?

Answer 31

By how closely related they are based on the similarities in their DNA sequences as well as their RNA sequences.

Question 32

What is the Three Domain System, and how does it work?

Answer 32

A classification system, in which all organisms are split into three main groups, called domains; archaea, bacteria and eukarya, before being split into their kingdom, phylum, class, order, family, genus and finally their species.

Question 33

What is the difference between the Five Kingdoms System and the Three Domains System?

Answer 33

In the Three Domains System, the prokaryotes kingdom of the Five Kingdoms System is split into two domains called the archaea and bacteria, and the other four kingdoms are part of the eukarya domain.

Question 34

What are archaea?

Answer 34

The organisms in this domain look similar to bacteria but they are genetically very different, often found in extreme environments such as hot springs and salt lakes, they are all single-celled and have no nucleus.

Question 35

What are bacteria?

Answer 35

The organisms in this domain are all true bacteria, which are genetically different from archaea, they are all single-celled and have no nucleus.

Question 36

What is selective breeding?

Answer 36

When humans artificially select the plants or animals that are going to breed because of prefered characteristics in the organisms.

Question 37

Why is selective breeding carried out?

Answer 37

It allows particular characteristics to remain in the population, as well as developing features which are useful or attractive, such as animals that produce more meat or milk.

Question 38

Describe the basic process of selective breeding.

Answer 38

From the existing stock, choose the organisms with the desired characteristics.
Breed them together.
Select the best of the offspring and breed them together.
Continue to repeat the process, this strengthens the desirable traits and eventually, all offspring will have the desired characteristics.

Question 39

How is selective breeding useful for agriculture?

Answer 39

Genetic variation means some cattle will have better characteristics for producing meat than others. To improve meat yields a farmer may select cows and bulls with these characteristics and breed them together. After doing this for several generations the farmer should get cows with very high meat yields.
This approach can be followed for other agricultural produces, like milk, fruits and other crops.

Question 40

How is selective breeding useful for medical research?

Answer 40

In several studies investigating the reasons behind alcoholism, rats have been bred with either a strong preference to alcohol or a weak preference to alcohol, this has allowed researchers to compare the differences between the two different types of rats, including their behaviour and how their brains work, which has assisted in developing methods to rehabilitate alcoholics. This approach can be followed for other ailments, including mental health disorders and learning disabilities.

Question 41

What are the disadvantages of selective breeding?

Answer 41

It reduces the number of different alleles in the population since the “best” offspring are always used for breeding and since they are often all closely related, it leads to inbreeding.
Inbreeding causes health problems, there’s a higher chance of offspring inheriting harmful genetic disorders, some dog breeds are susceptible to certain defects due to inbreeding, e.g. pugs often have breathing difficulties. This leads to ethical issues, especially when the negative characteristic is promoted in the population for research purposes.
It makes the entire population susceptible if a serious new disease appears, the lack of variation makes them all more at risk.

Question 42

What is a tissue culture?

Answer 42

Where tissue from an individual is reproduced from a by growing it from a sample.

Question 43

How are plants grown by tissue cultures?

Answer 43

The desired plant is chosen based on its desired characteristics.
Pieces of tissue are removed from the parent plants, normally the tips of fast-growing roots or shoots due to the meristems.
The tissues are then grown in a growth medium, which contains nutrients and growth hormones to support the growing plant- this is done in an aseptic environment to prevent the growth of microbes which may harm the plant.
Once the culture produces roots and shoots it can be moved to potting compost to grow naturally.

Question 44

Why are plants grown from a tissue culture clones?

Answer 44

Because they are genetically identical to the original plant.

Question 45

What is an aseptic environment?

Answer 45

An environment in which everything is sterilised to prevent the growth of harmful organisms.

Question 46

Why are plants cloned?

Answer 46

To produce more crop plants quickly, without the use of selective breeding.
Because whole plants can be grown all year round in very little space.
It saves money when buying genetically modified plants since instead of buying lots of disease resistant plants, a small number can be bought, grown and cloned for a much lower price.

Question 47

What is the main use of animal tissue cultures?

Answer 47

Medical research to carry out experiments in isolation to the rest of the body.

Question 48

How are animal tissue cultures produced?

Answer 48

A sample of the desired tissue is extracted from the animal.
The cells are then separated from each other using enzymes.
They are then placed in a culture vessel and bathed in a growth medium, which contains all the nutrients they need so that they can grow and multiply.
After several rounds of cell division, they can be split up again and placed into separate vessels to encourage further growth.
Once the culture has been grown, it can be stored ready for use.

Question 49

What is genetic engineering?

Answer 49

The modification of an organism’s genome to introduce desirable characteristics.

Question 50

How are enzymes used in genetic engineering?

Answer 50

Restriction enzymes can recognise specific sequences in DNA and cut the DNA at these points, leaving sticky ends where it has been cut.
Ligase enzymes can join two pieces of DNA together by their sticky ends.

Question 51

What is the name for where two different pieces of DNA have been stuck together?

Answer 51

Recombinant DNA.

Question 52

What is a vector?

Answer 52

Something that is used to transfer DNA into a cell.

Question 53

What are the two types of vector?

Answer 53

Plasmids and viruses.

Question 54

How do plasmids work as vectors?

Answer 54

The small circular molecules of DNA are passed between bacteria, so one bacteria will give the desired gene to additional, unmodified bacteria.

Question 55

How do viruses work as vectors?

Answer 55

Viruses insert DNA into the cells they infect.

Question 56

How is genetic engineering carried out?

Answer 56

The desired gene for insertion is cut out using a restriction enzyme, and the vector DNA is also cut open using the same enzyme.
The vector DNA and the desired DNA are mixed together with ligase enzymes.
The ligases join the pieces of DNA together forming recombinant DNA.
The recombinant DNA is inserted into other cells by the vector.
The cell can now use the gene you inserted, to display the desired characteristic.

Question 57

How is genetic engineering used in agriculture?

Answer 57

Crops are being engineered to be more resistant to herbicides and pests as well as to increase crop yield.

Question 58

How is genetic engineering used in medicine?

Answer 58

human genes can be inserted into other animals to produce useful proteins, such as insulin-producing bacteria, or animals the produce antibodies used in the treatment of arthritis, cancer and multiple sclerosis. These can be extracted from the animal, e.g. from their milk. Animals may also be able to grow transplant organs, such as hearts or kidneys in the near future.

Question 59

What are some of the concerns around genetic engineering?

Answer 59

Many people believe it is unethical as many genetically engineered animals don’t survive as embryos and those that do often develop more health problems in later life.
Some believe the modified genes in crops may get out into the environment and may be picked up by weeds to produce “Superweeds”, or that the crops may adversely affect food chains or even human health.

Question 60

How are crop plants genetically engineered to be resistant to insects?

Answer 60

The bacterium Bacillus thuringiensis (Bt) produces a toxin that kills many of the insect larvae that harm crops.
The gene for the Bt toxin is inserted into crops, such as corn and cotton, which then produce it in their stems and leaves making them resistant to insect pests.
Since the toxin is harmless to humans, and other animals it is safe to use but the long-term effects of Bt crop exposure are unknown.
To prevent insect pests from becoming resistant to the toxin other pesticides are used alongside it.

Question 61

What is currently happening to the global population level?

Answer 61

It is rising and doesn’t show signs of slowing down.

Question 62

What effect does the trend in population levels have on food production?

Answer 62

The level of food production must increase to maintain food security.

Question 63

What is food security?

Answer 63

Where everyone has access to enough food that is safe to eat and has the right balance of nutrition.

Question 64

How are genetically engineered organisms being used to improve food security?

Answer 64

GM crops can be made more resistant to disadvantageous environments, such as droughts and high pest levels, which increases crop yield.
Some crops can be engineered to produce necessary vitamins which may not be easily available locally which combats deficiency diseases.

Question 65

Why might the use of GMOs not help in some areas?

Answer 65

The food is too expensive for many in some places, so to combat hunger in these areas poverty must be tackled first.
Many fear that poorer countries may become entirely dependent on large companies, which may affect their way of life.
Some countries have poor soil to the point that GM crops wouldn’t survive either so there would be no point.

Question 66

What are other non-GMO methods of increasing crop yields?

Answer 66

Fertilisers, they contain necessary vitamins and minerals essential for plant growth, which can make poor soil usable. However, excessive use of fertilisers, especially near lakes and rivers can lead to eutrophication in these bodies of water.
Pests can be controlled biologically through the use of other organisms, such as cane toads in Australia which eat beetles responsible for damaging a variety of crops. This tends to have a longer lasting effect but can be less harmful to wildlife. However the introduction of new organisms can cause problems, and the cane toad is now a pest itself since they poison native species.