B4 - Organising plants and animals

Question 1

B4 - describe the structure and function of an artery

Answer 1

Structure:
Small lumen

Thick walls

Thick layer of elastic tissue

Function:
Carry blood at high pressure

Carry blood away from the heart.

Carry oxygenated blood

Question 2

B4 - describe the structure and function of a vein

Answer 2

Structure:
Large lumen

Thin walls

Valves to prevent backflow

Very little elastic tissue
Function:
Carry blood at low pressure

Carry blood towards the heart.

Carry deoxygenated blood

Question 3

B4 - describe the structure and function of a capillary

Answer 3

Structure:
Very thin single cell walls

Narrow lumen

No elastic tissue
Function:
To link arteries and veins.

To allow the diffusion of substances.

Question 4

B4 - Describe the structure of the heart

Answer 4

Two atria (top)

Two ventricles (bottom)

Valves to prevent backflow

Vena cava (blood from the body)

Pulmonary artery (blood to the lungs)

Pulmonary vein (blood from the lungs)

Aorta (blood to the body)

Question 5

B4 - Describe the structure of a leaf referring to each part and its specific function.

Answer 5

Upper/lower Epidermal tissues: cover and protect the plant.

Waxy cuticle: waterproofs the surface of the leaf.

Palisade mesophyll tissue: contains a lot of chloroplasts to carry out photosynthesis - found at the top of the leaf.

Spongy mesophyll tissue: contains large air spaces and a large surface to allow diffusion of gases in the leaf.

Question 6

B4 - Describe the process of transpiration.

Answer 6

Water evaporates and then diffuses out of the leaf. This is called transpiration.

This draws more water out of the xylem cells in the leaf to replace what has been lost.

The xylem cells make one long continuous tube from the leaves to the roots and they act like a drinking straw.

As water is lost from the leaves (transpiration) more water is naturally drawn up from the roots to replace it. This creates a continuous flow of water from the roots to the leaves.

Question 7

B4 - Describe the factors that affect transpiration.

Answer 7

Light intensity: lots of light = more photosynthesis

Temperature: if its hot = increased rate of photosynthesis and diffusion

Air movement: lots of wind = increased rate of diffusion

Humidity falls: reduced rate of diffusion