BY2 June 2013

Question 1

State 2 practical measures which should be taken when setting up the apparatus to ensure the photometer functions correctly. Give reasons for answers.

Answer 1

Shoot cut under water - prevent air entering.

Shoot with large number of leaves - ensure measure able rate of transpiration.

Question 2

Name the original source of energy that moves water through a plant.

Answer 2

Sunlight.

Question 3

Explain how water moves up the xylem.

Answer 3

Molecules of water moving together pulled up because of cohesion of molecules.
Adhesion to walls of xylem(hydrophilic lining).
Root pressure forces water upwards.

Question 4

Explain the difference between the position of the xylem and phloem in the stem and root.

Answer 4

Xylem/vascular tissue is at the centre.

No vascular bundles/peripheral vascular bundles in stem.

Question 5

Describe and explain the process of inspiration in a mammal.

Answer 5

Intercostal muscles contract and ribs move up and out.
Diaphragm contracts and flattens.
Internal volume of thorax increases.
Pressure in thorax decreases.
Difference in air pressure outside draws air into lungs.

Question 6

Explain how the countercurrent flow works in the gills of bony fish.

Answer 6

Blood flows across gills in opposite direction to water.
Oxygen diffusion gradient maintained across entire gill surface.
Oxygen passes from water to blood.
Higher saturation of blood with oxygen.

Question 7

Explain why parallel flow is less efficient than counter current flow.

Answer 7

Equilibrium is reached part way across the gill plates, diffusion gradient is not maintained.
Lower % saturation with oxygen(only 50%), less oxygen uptake.

Question 8

Suggest why gill filaments would not provide an efficient gas exchange surface on land.

Answer 8

Gills wouldn’t remain moist/dry out, preventing oxygen from dissolving on surface of gills.
Gills may collapse, decrease in SA.

Question 9

Which I the most acidic region in the alimentary canal?

Answer 9

The stomach.

Question 10

In which two areas are proteins, carbohydrates and lipids digested together?

Answer 10

Duodenum and ileum.

Question 11

Where does the process of digestion begin?

Answer 11

The stomach.

Question 12

Where is the main site of lipase production?

Answer 12

The pancreas.

Question 13

What is the section of the alimentary canal where water is absorbed?

Answer 13

Large intestine - colon.

Question 14

Explain how the jaw and teeth of a sheep is adapted for it’s adapted to it’s mode of nutrition.

Answer 14

Large, ridged molars for grinding.
Gap between teeth to assist with chewing/tongue to manipulate food cud.
Well developed incisors for cutting vegetation.
Jaw moves in a circular plane.
Very small/ no canines.

Question 15

Explain how the guy of the sheep is adapted for digestion.

Answer 15

Has a four cambered stomach.
Contain cellulose digesting bacteria.
Long gut to allow extra time for digestion of cellulose.
Cud is regurgitated for further chewing.

Question 16

State what is meant by the term parasite?

Answer 16

Organism which lives on or in another organism(the host)obtaining nourishment at the expense of the host, causing harm to the host.

Question 17

Describe how the tapeworm is adapted to obtain it’s nutrients.

Answer 17

Attaches to gut wall by hookers and suckers.
Large SA to volume ratio.
Digested products in host guy absorbed into tapeworm.
Thin/flat-short diffusion distance.

Question 18

Explain how the technique of ringing causes an accumulation of sucrose in a plant.

Answer 18

Sucrose is produced in photosynthesising leaf.
Sucrose travels in phloem.
Phloem removed by the ringing process.
Sucrose can’t flow to roots.

Question 19

Name one other type of organic molecule likely to accumulate with sucrose.

Answer 19

Amino acids.

Question 20

If the growing points of the shoot of the plant is removed there is a greater accumulation of sucrose. Explain why this is the case.

Answer 20

Sucrose used for cell division.
Less/no sucrose used by growing areas as they have been removed.
Therefore more will pass down the stem.

Question 21

Explain fully the likely effect of the removal of the ring of tissue on the concentration of sucrose below the ring.

Answer 21

Sucrose not replaced from above the ring.
So concentration decreases;
As movement towards root continues;
And sucrose used in respiration for growth.

Question 22

Describe how the reproductive strategies of vertebrates show a gradual adaptation to the colonisation of land.

Answer 22

Fish/amphibians show external fertilisation.
Fertilised egg develops outside body of parent.
Many eggs produced.
Ensure some survive.
Reptiles/birds/mammals internal fertilisation.
This allows gametes to be independent of water.
Increased chance of fertilisation.
Reptiles/birds evolution of an amniote egg.
Eggs surrounded by protective shell.
Birds incubate eggs outside mothers body.
Mammals - development inside mother’s body.
Nutrients/O2 via planceta.
Young are born well developed.
Birds/mammals exhibit parental care.
Relationship between parental care an number of offspring produced.

Question 23

State what is meant by the term transpiration.

Answer 23

Evaporation of water from surface of leaf through stomata.