Test 3 Resit

Question 1

The role of micro organisms

Answer 1

Micro organisms play the role of decomposers that recycle the carbon from dead organic matter. Decomposers respire to release carbon dioxide into the atmosphere. Carbon from the dead organic matter is left in peat and coal which can be combusted to release carbon dioxide back into the atmosphere.

Question 2

Gel electrophoresis- separating fragments

Answer 2

1. DNA is cut into fragments
2. Placed in a gel of agarose which provides the fragments can move. The gel are in wells loaded using a micro pipette
3. Submerged into a buffer solution connected to electrodes. Negative charged DNA moves towards positive electrode. Fragments migrate according to size, smaller fragments travel faster. DNA are separated into separate invisible strands
4. Reference sample is added to the gel, known as DNA markers. Fragments are measured in base pairs.

Question 3

Define gene pool

Answer 3

Consists of all the alleles of all genes present in a population

Question 4

What happens inside a host cell when it is infected by a virus

Answer 4

1. Virus attaches to a host cell
2. Virus inserts nucleic acid
3. Viral nucleic acids replicate
4. Viral protein coats synthesised
5. New virus particles are formed
6. Particles released due to cell lysis

Question 5

Events of speciation

Answer 5

Species become geographically isolated- prevents a group of individuals from breeding with the rest of the population
Respond to different selection pressure, mutations accumulate randomly. Pass on their advantageous alleles to the next generation, which increases the allele frequency. The two species eventually become reproductively isolated as they cannot interbreed to produce a fertile offspring.

Question 6

Formula for NPP

Answer 6

GPP-R

Question 7

Rigor mortis- series of events

Answer 7

1. Muscles become starved of oxygen and oxygen dependent reactions stop
2. Respiration in the cells become anaerobic and produces lactic acid
3. The pH of the cell falls inhibiting enzymes and anaerobic respiration
4. ATP needed for muscle contraction is no longer produced
5. Proteins can no longer move over one another to shorten the muscle, fixing the muscles and joints.