B2.2

Question 1

Surface are to volume ratio is important because

Answer 1

The larger the organism the lower the surface area becomes

This means diffusion will occur over a large distance, which will take too long for the organism to stay alive

Question 2

Alveoli

Answer 2

Exchange surface for the diffusion of oxygen in the lungs

Question 3

Circulatory system

Answer 3

A closed system consisting of the heart and blood vessels, which has the purpose of pumping blood around the body to supply oxygen

Question 4

Double circulatory/pump system

Answer 4

Blood flows through the heart twice during each circuit of the body

The blood is under a higher pressure than a single circulatory system as the blood does not have as far to travel

Higher pressure means that materials are transported quickly around the body

Question 5

Capillaries

Answer 5

Very small lumen

Wall made of a single layer of cells

Question 6

Arteries

Answer 6

Thick outer wall

Thick layer of muscle and elastic fibres

Small lumen

Smooth lining

High pressure, pumping blood away from the body

Question 7

Veins

Answer 7

Fairly thin outer wall

Thin layer of muscle and elastic fibres

Large lumen

Smooth lining

Low pressure, returning blood to the heart (low pressure so the heart doesn’t burst)

Question 8

What’s in blood

Answer 8

Red blood cells - fit through the lumen of the capillary one cell at a time

White blood cells - large cells that contain a nucleus. They fight disease by making antibodies or engulfing microorganisms

Plasma - 90% water. Many materials are transported by being dissolved in it

Platelets - tiny structures that help the blood clot

Question 9

Heart Structure

Answer 9

Top chambers: Atria
Bottom chambers: Ventricles

De-oxygenated blood -> right atrium -> right ventricle -> heart beats -> pulmonary artery -> lungs -> oxygenated blood -> pulmonary vein -> left atrium -> left ventricle -> heart beats -> aorta -> rest of the body

Question 10

Xylem

Answer 10

Transport system that transports water and mineral ions from the roots to the stem, leaves, and flowers

Water diffuses via the roots, mineral ions are taken in via active transport

Made from dead xylem cells which have no cell walls at the ends of the cell so they can form tubes

The rest of the xylem cellulose is thickened to provide support

Water and minerals travel in one direction only

Question 11

Phloem

Answer 11

Transport system that transports dissolved sugars from photosynthesis and other soluble food molecules from the leaves to all other areas of the plant (translocation)

Sugars are taken into meristems to make new plant cells

Phloem vessels are made of live cells

They have sieve plates, small holes in the end of the wall which allow dissolved sugars to pass through

Sugars and food molecules can travel in both directions

Question 12

Vascular bundles provide support in the…

Answer 12

Leaf - form a network to support the softer leaf tissue

Stem - around the outer edge, providing the stem with strength to resist bending in the breeze

In the root at the centre - enable the root to act as an anchor

Question 13

Transpiration

Answer 13

The loss of water from a plant’s leaves via the stomata

The stomata open to allow CO2 in for photosynthesis

Question 14

Transpiration Stream

Answer 14

The constant flow of water from the roots, through the xylem, and out of the leaves

Question 15

Why is water lost when the stomata open

Answer 15

Water evaporates from the cells within the leaf into the leaf’s air spaces.

This creates a concentration gradient between the air inside the leaf and the air on the outside

Water vapour then diffuses out of the leaf (high conc.) and into the air (low conc.)

Question 16

How do leaves prevent uncontrolled water loss

Answer 16

The upper surface is covered in a waxy waterproof layer (cuticle)

In hot environments it’s normally very thick and shiny to minimise evaporation

Most stomata are found on the underside of the leaf

Question 17

Factors affecting the rate of transpiration: light intensity

Answer 17

Stomata open more the brighter it is, increasing the rate of transpiration until the stomata are fully open

Question 18

Factors affecting the rate of transpiration: temperature

Answer 18

The greater the temperature the more water will evaporate, increasing the rate of transpiration

Question 19

Factors affecting the rate of transpiration: air movement (wind)

Answer 19

Wind moves evaporated water away from the leaf

This increases the concentration gradient between the leaf and air, meaning water will diffuse more quickly out of the leaf

Question 20

Humidity

Answer 20

The higher the humidity, the more water

This decreases the rate of transpiration