B14 - Variation And Evolution

Question 1

What is variation?

Answer 1

Variation is the differences in the characteristics of individuals in a population
Variation may be due to differences in inherited genes (genetic causes), the conditions in which organisms develop (environmental causes) or a combination of both
• in sexually reproducing populations there are many different combinations of alleles. This means that genetic variation is high

Question 2

Nature - genetic variation

Answer 2

• basic characteristics are a result of genes inherited from our parents
• eye colour, nose shape, dimples

Question 3

Nurture - environmental variation

Answer 3

• conditions in which it develops
• genetically identical plants can be grown under different conditions or with different mineral ions, and the resulting plants do not look identical
• plants deprived of light, CO2 or mineral ions do not make as much food as plants with everything

Question 4

How can mutations lead to human evolution?

Answer 4

• most mutations do not affect the phenotype if a mutation creates a new phenotype that is better adapted to environmental changes, the mutation is likely to spread throughout the population over generations

Question 5

Evolution and speciation

Answer 5

• Evolution is the gradual change of inherited characteristics of biological populations over time
• speciation happens when two animal populations diverge a lot

Question 6

Why does speciation happen?

Answer 6

• result of evolution
• natural mutations can create new alleles and two populations can begin to diverge

Question 7

What is speciation?

Answer 7

• when the average phenotypes of two populations have diverged so much that the two populations can no longer breed to produce fertile offspring
• two different species have been formed

Question 8

Evolution

Answer 8

• discovery of genes is crucial to understanding - provides clear mechanism by which traits are inherited and varied within populations
• resistance results from random genetic mutations favoured by natural selection

Question 9

Natural selection

Answer 9

• proposed by Charles Darwin in 1859
•‘genetic variation, survival of the fittest (individuals possessing genes that make them better adapted to the environment will have a greater chance of survival), breeding, best characteristics survive

Question 10

Selective Breeding

Answer 10

• when humans choose animals and crops to breed, based on their genetic characteristics
• promotes genetic characteristics seen as desirable

Question 11

Steps for selective breeding

Answer 11

• choose parents who most strongly display the desired characteristic
• breed chosen parents
• from the resultant offspring, choose their offspring that best display the desired characteristic
• breed these chosen offspring
• repeat this process of breeding and reselection over many generations, until all the offspring show the desired characteristics
• it is artificial selection
•

Question 12

Examples of selective breeding

Answer 12

• disease resistance in crops is a useful characteristic because it improves yield
• gentle natured domestic dogs
• crops, dogs, flowers, farm animals
• yield = food production

Question 13

Dangers of selective breeding

Answer 13

• reduced variation - makes it harder for species to adopt to environmental changes
• inbreeding - some breeds become particularly susceptible to disease or inherited defects (reproduction of animals that are related to each other)
• e.g. French bulldogs have breathing problems due to flat faces

Question 14

What is a peat bog?

Answer 14

• semi-decomposed plant matter often used for fuels.
• preservation of matter due to limited oxygen to the matter as they have been water logged
• when oxygen is removed, bacteria is no longer able to respire therefore reducing the rate of decomposition
• bodies found preserved because there is a lack of microorganism breaking it down
• Destroying them means more CO2 is released if peat is burnt or from microbial respiration during decomposition.
• habitat destruction

Question 15

Why is deforestation a problem?

Answer 15

• tropical rainforests contain the most biodiversity on the planet. When we lose these forests, we reduce biodiversity and species become extinct, which could have contributed to medicine and food resources for the future

Question 16

How does deforestation increase the amount of CO2?

Answer 16

• burning trees = combustion = release of CO2
• dead vegetation after decomposes and the microorganisms use up oxygen and release more CO2 as they respire
• reduces the rate at which CO2 is removed because there is less photosynthesis - lose vital carbon dioxide ‘sink’

Question 17

Why are the number of peat bogs and peatlands decreasing?

Answer 17

• massive carbon store - therefore they are burnt and destroyed for fuel and used as garden compost
• this is a cause for concern because the organism that depend on peat bogs are destroyed, therefore more loss of biodiversity

Question 18

Gardeners using peat

Answer 18

• peat is widely used by gardeners to improve the properties of the soil and provide an ideal environment for seed germination, which helps to increase food production
• however when peat is used in gardens CO2 is released into the atmosphere and the carbon store is lost - biodiversity loss
• UK government wants gardeners to use ‘peat-free’ composts
• this will reduce CO2 emissions and conserve peat bogs/peat lands as habitats for biodiversity
• compost can be made from bark, garden waste, coconut husks - problem is persuading gardeners to use them

Question 19

Government action against gardeners using peat

Answer 19

• want gardeners to use peat free compost
• this will reduce CO2 emissions and conserve peat bogs/peatlands as habitats for biodiversity
• compost can be made from bark, garden waste, coconut husks - problem is persuading gardeners to use them

Question 20

Carbon sinks

Answer 20

• forests - absorb CO2 via photosynthesis
• oceans - CO2 dissolves in water and phytoplankton use carbon for their skeleton and shells
• peat bogs - lock away CO2, when burnt - CO2 released back into the atmosphere

Question 21

The theory of evolution

Answer 21

Discovered by Charles Darwin - 1859 book

The theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed over 3 billion years ago.
• Mutations occur continuously. Very rarely a mutation leads to a new phenotype. If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species.

Question 22

What is genetic engineering?

Answer 22

Genetic engineering involves modifying (changing) the genetic material of an organism. The gene for a desirable characteristic is cut out of one organism and transferred to the genetic material in the cells of another organism. This gives the genetically engineered organism a new, desirable characteristic. For example, plant crops have been genetically engineered to be resistant to certain diseases, or to produce bigger, better fruits.

Question 23

Process of genetic engineering

Answer 23

Enzymes are used to isolate and ‘cut out’ the required gene from an organism, for example, a person.
• The gene is then inserted into a vector using more enzymes. The vector is usually a bacterial plasmid or a virus.
• The vector is then used to insert the gene into the required cells, which may be bacteria, animal, fungi, or plants
• Genes are transferred to the cells at an early stage of their development (in animals, the egg, or very early embryo). As the organism grows, it develops with the new desired characteristics from the other organism. In plants, the desired genes are often inserted into meristem cells which are then used to produce identical clones of the genetically modified plant.

Question 24

Example of genetic engineering with bacteria

Answer 24

The human insulin gene can be inserted into bacteria to produce human insulin:
1. The insulin gene is first cut out of human DNA using enzymes.
2. The same enzymes are then used to cut the bacterial DNA and different enzymes are used to insert the human insulin gene.
3. The bacteria are then allowed to multiply. The insulin they produce while they grow is purified and used by people with diabetes.

Question 25

Downsides of using bacteria in genetic engineering

Answer 25

There is a limit to the proteins bacteria can make

Question 26

How animals are used in genetic engineering

Answer 26

Scientists have now found that genes can be transferred to animal and plant cells as well as bacteria and fungi. New techniques are making genetic modification of a wide range of organisms easier all the time.
For example, genes from jellyfish have been used to produce crops that glow in the dark when lacking water. This shows where irrigation is needed.

Other examples:
• mice have been modified to model human diseases, such as Alzheimer’s, cancer and diabetes
• some animals have been engineered to make complex human proteins in their milk

This allows scientists to see how diseases work and see how new treatments might work

Question 27

What are genetically modified crops?

Answer 27

• Crops that have had their genes modified by genetic engineering techniques are known as genetically modified crops

Question 28

Benefits of GM crops

Answer 28

• can increase yield and make more crops
• GM crops can have nutritious value needed by individuals in developing nations, eg golden rice which contains beta-carotene

Question 29

Concerns about GM crops

Answer 29

• reduce farmland biodiversity, because it affects number of wildflowers and therefore insects
• might not be safe/don’t fully understand, so may develop allergies
• transplanted genes may get out into the natural environment - e.g. herbicide resistance gene may be picked up by weeds and create a ‘super weed variety’

Question 30

GM crop examples

Answer 30

• corn and soybean in the US
• golden rice

Question 31

Ethics of genetic technologies - for

Answer 31

• GM can help improve plants resistance to pests and diseases and cut the use of chemicals that harm the environment
• The overwhelming majority of scientific research over the last 20 years finds GM technologies safe to use
• GM can be good for both humans and animals as it can lead to the treatment of illnesses caused by defective genes
• the development of GM can lead to improvements in other areas, such as cloning and IVF to help treat infertility
• climate change is threatening humanity. We urgently need more drought resistant crops to help feed the world.
• GM crops can be used to help solve the worlds food problems by creating crops and animals that have higher yields
• foods can be genetically modified to improve flavour - chilies made spicier, corn made sweeter

Question 32

Ethics of genetic technologies - against

Answer 32

• a GM crop could cross fertilise with another plant and create a super weed
• genetic engineering violate animal rights because it involves manipulating animals for humans ends
• G M. Technologies have led to companies patenting their discoveries which have pushed out up the price for the farmer.
• transferring genes from one species to another, could create dangerous reactions to people with allergies
• we are unsure of the effects it may have on other species, for example, insects that eat the plants
• some believe that life has been given to us by God, and it is therefore not our right to play God by changing this
• GM is bad for biodiversity as it messes with evolution and natural selection
• GM can cause harm by forcing them to grow too fast, leading to physical problems and abnormalities