BY5-June2012

Question 1

The total level of carbon dioxide due to the actions of an individual, mainly through their energy use, over a period of one year.

Answer 1

Carbon footprint.

Question 2

A natural process which results from the build up of nitrates in lakes and rivers.

Answer 2

Eutrophication/algal bloom.

Question 3

A technique whereby trees are cut down close to the ground then left for several years to re-grow shoots.

Answer 3

Coppicing.

Question 4

The simultaneous growth of a large number of crop plants of similar age and type within a defined area.

Answer 4

Monoculture.

Question 5

Define the term pollination.

Answer 5

The transfer of pollen from the anther to the stigma.

Question 6

Name the part of the reproductive tract in which the nucleus of an animal sperm enters the cytoplasm of the egg.

Answer 6

Oviduct/fallopian tube.

Question 7

Explain the role of the acrosome in the process of transferring the nucleus from the animal sperm into the cytoplasm of the egg.

Answer 7

Acrosome contains enzymes.

These enzymes hydrolyse/break down the zona pellucida/jelly coat.

Question 8

State two similarities between the process in an animal and in a plant when the male nucleus enters the ovule/egg.

Answer 8

Formation of a growth tube.
Nucleus travels along a tube into egg/ovule.
Enzymes are produced which digests a path, allowing the tube to grow.
Both are chemotropic.
Membranes burst to release male gametes.

Question 9

The pentadactyl limb is a characteristic of extinct and present day mammals.

Answer 9

Fossil record and classification.

Question 10

A wide range of bacteria are now resistant to penicillin.

Answer 10

Survival of the fittest-the individual most suited to the conditions survive or breed more successfully.

Question 11

Over 500 species of plants have been recorded on the Galápagos Islands and 180 of these are not found anywhere else in the world.

Answer 11

Isolating mechanism-separating of a population into two or more sub-groups which could be caused by the environment.
Divergence-If conditions facing the two sub-groups are different they will gradually show divergence.

Question 12

Two species of pine trees are found in Monterey Bay, California. P.radiata produces pollen in February and P.attenuata in April.

Answer 12

Isolating mechanism and divergence.

Question 13

What is meant by the term ‘gene therapy’?

Answer 13

Replacing defective genes with copies of a non-defective genes.

Question 14

Somatic cell therapy.

Answer 14

Targets cells in affected tissues.

Not inherited.

Question 15

Germ line therapy.

Answer 15

Introduces genes into the egg.

Inherited.

Question 16

Explain how the presence of the altered protein CFTR, results in the production of thick, sticky mucus and how this accounts for the respiratory symptoms of cystic fibrosis.

Answer 16

CFTR is a channel protein.
Blocks transport of chloride ions out of cells into mucus.
Water retained in cell/no osmosis.
Unable to remove mucus in lungs.
Infection/more susceptible to disease.
Narrowing of air passages, so reduced air flow.
Increased diffusion distance/ reduced SA for gas exchange, insufficient oxygen received.

Question 17

Describe on technique that could be used to introduce functional CFTR genes into someone with cystic fibrosis.

Answer 17

Modified/correct genes are inserted into liposomes(as a vector).
Liposomes fuse with cell membrane/infects cell.
Modified gene passes trough membranes into cell.
Applied by inhaler/aerosol.

Question 18

Explain why the replication of DNA is described as semi-conservative.

Answer 18

Each new DNA molecule consists of one original strand and one new strand of DNA.

Question 19

Explain why during a PCR the DNA is first heated to 95 degrees?

Answer 19

To break bonds between DNA strands or bases to deprecate original DNA into two single strands.

Question 20

Explain why during the second stage of PCR the temperature is reduced to 55 degrees.

Answer 20

Allows primers/short pieces of RNA to bind to single stranded DNA.

Question 21

Explain why during the third stage of PCR the temperature is increased to 70 degrees.

Answer 21

DNA polymerase catalyses the synthesis of a complementary strand.

Question 22

About 20% of DNA produced by PCR is copied inaccurately. Suggest and explain why it is not safe to use PCR to clone the CFTR gene for use in treating cystic fibrosis.

Answer 22

Percentage risk too high for human application.
Incorrect mRNA.
Different tRNA/brings incorrect amino acid.
Structure of protein synthesised unknown/sequence altered.
Protein non-functional/chloride ions not transported, thick mucus still produced.

Question 23

Name the enzyme involved in the transcription stage of protein synthesis.

Answer 23

RNA polymerase.

Question 24

Explain how tetracycline stops protein synthesis in bacteria.

Answer 24

Prevents translation.
Tetracycline inhibits mRNA triplet/codon.
Anticodon/tRNA triplet cannot pair with mRNA triplet/codon.
Amino acid not added to polypeptide chain.

Question 25

Explain what is meant by succession.

Answer 25

Change in composition of a species in a community over time, due to change in natural environment.

Question 26

What is meant by the term climax community?

Answer 26

A stable community which undergoes no further change/reaches equilibrium.

Question 27

The rate at which consumers accumulate energy in the form of cells or tissue.

Answer 27

Secondary productivity.

Question 28

Define the terms conservation and extinction. Discuss the importance of conservation of genetic sources. Describe the steps conservationists have taken to prevent the extinction of endangered species.

Answer 28

Extinction is the loss of species.
Conservation is the planned preservation of wildlife.
To ensure the survival of the species.
Conservation of existing gene pools.
To conserve potentially useful genes for future generations.
Use of plants/animals as a gene bank to cross with highly cultivated varieties. Conservation of plants with medicinal purposes.
Planned preservation of habitat eg wetlands.
Seed/sperm banks.
Re-introduction programmes eg Red kite.
Protection/breeding of endangered species in specialised zoos.
Trade restrictions on endangered species.
National parks, CCW etc.
Legislation eg prevent over-fishing.

Question 29

Give an account of the principles involved in cloning of mammals, including the use of stem cells.

Answer 29

Embryo cloning-in vitro fertilised egg divides/undergoes mitosis to form embryo.
Embryo is split into separate cells.
Before differentiation.
Nuclear transplant-nucleus may be removed from diploid/somatic cell.
Nuclear transplant-nucleus may be removed from egg/ovum.
Donor and recipient cells fused together.
The embryo is allowed to develop in a surrogate.
Animal born is genetically identical to the original donor.
Cells are able to differentiate into more than one cell type.
Eg tissue containing stem cells-bone marrow.
Human stem cells could be use to grow into a required organ or tissue.
Less likelihood of rejection.

Question 30

Discuss the possible objections to the use of stem cells.

Answer 30

Embryos have to be destroyed to provide the stem cells/Pro-life issues-embryos have the potential for independent life in the future.
Unknown long term side affects of stem cells.
Genetic modification of humans for non-medical reasons.