Unit 2- Section 5 Exchange And Transport Systems

Question 0

How do single-celled organisms exchange organs and mass transport systems?

Answer 0

There substances can diffuse directly into or out of the cell across the cell surface membrane. The diffusion rate is quick because of the small distances the substances have to travel

Question 1

How does surface area:volume ratio affect how quickly substances are exchanged?

Answer 1

They have a larger surface area so this increase the rate of diffusion

Question 2

How do multi-cellular organisms exchange substances?

Answer 2

The diffusion across the outer membrane is two slow because some cells are deep within the body so they are far away from the outside environment and larger animals also have a low surface area: volume ratio so it’s hard for substances to be exchanged over a small surface to a large body. So multi-cellular organisms do not just use diffusion to exchange, they need specialised exchange organs.

Question 3

What do multicellular organisms need to exchange substances?

Answer 3

Exchange organs
Efficient system to carry substances to and from their individual cells- this is mass transport. In mammals this normally refers to the circulatory system which uses blood to carry glucose and oxygen around the body. It also carries hormones, antibodies and waste like carbon dioxide

Question 4

How does body size affect heat exchange?

Answer 4

The rate of heat loss depends on it’s surface area, if it has a high surface area to volume ratio more heat is lost

Question 5

How does body shape affect heat exchange?

Answer 5

Animals with a compact shape have a small surface area relative to their volume, minimising heat loss from their substance. Animals with a less compact shape have a larger surface area relative to their volume, this increases heat loss

Question 6

Describe some other adaptations to affect heat loss?

Answer 6

Animals that have a large surface area to volume ratio that live in hot conditions loose more water so are designed to produce less urine

Smaller mammals in cold conditions have layers of fur

Question 7

What are two things that increase the rate of diffusion?

Answer 7

Large surface area
Thin-short diffusion pathway
Organism maintains steep concentration gradient

Question 8

Describe gas exchange in single celled organisms

Answer 8

Single celled organisms absorb and release gases by diffusion through their outer surface. They have a relatively large surface area, a thin surface and a short diffusion pathway. This means that there is no need for a gas exchange system

Question 9

Describe gas exchange in fish

Answer 9

There is a lower concentration of oxygen in water than air, so fish have special adaptations to get enough of it. In fish the gas exchange surface is the gills.

Question 10

Describe the structure of gills and how they increase diffusion

Answer 10

Water containing oxygen, enters the fish Through its mouth and passes out through the gills. Each gill is made up of lots of thin plates called gill filaments which give a large surface area for exchange surfaces. The gill filaments are covered in lots of tiny structures called lamellae which increase the surface area even more. The lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion between the water and blood

Question 11

Describe the counter-current system in the fish gills

Answer 11

In the lamellae water flows in one direction and blood flows in the opposite, this keeps a steep concentration gradient throughout the fish so therefore increases diffusion

Question 12

Describe gas exchange in dicotyledonous plants

Answer 12

Plants need carbon dioxide for photosynthesis, which produced oxygen as a waste gas. They need oxygen for respiration which produces carbon dioxide as a waste gas. The main gas exchange surface is the surface of the mesophyll cells in the leaf, they are well adapted for their function because they have a large surface area. The mesophyll cells are inside the leaf, gases move in and out through the special pores in the epidermis called stomata. The stomata can to allow exchange of gases, and close if the plant is losing too much water. Guard cells control the opening and closing of the stomata

Question 13

Describe gas exchange in insects

Answer 13

Terrestrial insects(live on land) back microscopic air filled pipes called trancheae which they use for gas exchange, air moves into the trancheae through pores on the surface called spiracles. Oxygen travels down the concentration gradient towards the cells. Carbon dioxide from the cells moves down it’s concentration gradient towards the spiracles to be released into the atmosphere. The trancheae branch off into smaller trancheoles which have a thin, permeable walls and go into individual cells. This means that oxygen diffuses directly into the respiring cells- the insects circulatory system does not transport oxygen. Insects use rhythmic abdominal movements to move air in and out of the spiracles

Question 14

How do plants control water loss?

Answer 14

Exchanging gases results in losing water.

• have stomata and guard cells to control the entry and exit of water and gas
• if it needs to lose water then the guard cells will let some escape
• water enters the guard cells making them turgid which opens the pore
• if the plant is dehydrated the guard cells will lose the water which closes the pore

Question 15

How to insects control water loss?

Answer 15

Loosing too much water they close their spiracles using muscles
Waterproof waxy cuticle all over their body and hairs around their spiracles which reduce evaporation

Question 16

How are plants specially adapted to love in warm, dry or windy conditions?

Answer 16

• stomata sunk in outs to trap water vapour, reducing the evaporation by lowering the diffusion gradient
• curled leaves with the stomata inside, protecting them from the wind and therefore water loss
• layer of hairs on the epidermis to trap water vapour around the stomata reducing the diffusion gradient
• reduced number of stomata so there are fewer places for water to escape
• waxy, waterproof cuticles on leaves and stems to reduce evaporation.

Question 17

What is the function of the circulatory system?

Answer 17

Multicellular organisms, like mammals, have a low surface area to volume ratio so they need a specialised transport system to carry raw materials from specialised exchange organs to their body cells. This is the circulatory system

Question 18

What is the circulatory system made up of?

Answer 18

Heart and blood vessels. The heart pumps the blood through blood vessels to reach different parts of the body

Question 19

The pulmonary artery cArries blood from the what to the what

Answer 19

Heart to the lungs

Question 20

Pulmonary vein carries blood from… To…

Answer 20

From the lungs to the heart

Question 21

The aorta carries blood from the… To the…

Answer 21

Heart to the body

Question 22

The vena cava carries blood from the… To the…

Answer 22

Body to the heart

Question 23

The hepatic artery carries blood from the…to the…

Answer 23

Body to the liver

Question 24

The hepatic vein carries blood from the…to the…

Answer 24

Liver to the vena cava

Question 25

The hepatic portal vein carries blood from the…to the…

Answer 25

Gut to the liver

Question 26

The renal artery carries blood from the…to the…

Answer 26

Body to the kidneys

Question 27

The renal vein carries blood from the…to the…

Answer 27

Kidneys to the vena cava

Question 28

What does blood transport?

Answer 28

Respiratory gases, products of digestion, metabolic wastes and hormones around the body

Question 29

Describe the two circuits of blood around the body

Answer 29

Takes blood from the heart to the lungs then back to the heart
Other loop takes blood around the rest of the body

Question 30

How does the heart have it’s own blood supply?

Answer 30

Through the coronary arteries

Question 31

Describe arteries

Answer 31

They carry blood from the heart to the rest of the body. their walls are thick and muscular and have elastic tissue to cope with the high pressure produced by the heart beat. The inner lining (endothelium) is folded, allowing the artery to stretch. This also helps with it to cope with high pressure. All arteries carry oxygenated blood except for the pulmonary arteries, which take deoxygenated blood to the lungs

Question 32

Describe arterioles

Answer 32

Arteries divide into smaller vessels called arterioles. These form a network throughout the body. Blood is directed to different areas of demand in the body by muscles inside the arterioles, which contract to restrict blood flow or relax to allow full blood flow

Question 33

Describe veins

Answer 33

Veins take blood back to the heart under low pressure. They have a wider lumen than equivalent arteries, with very little elastic of muscle tissue. Veins contain valves to stop the backflow of blood. Blood flow through the veins is helped by the contraction of the body muscles surrounding them. All veins carry deoxygenated blood (because oxygen has been used up by the body cells) except for the pulmonary veins which carry oxygenated blood to the heart from the lungs

Question 34

Describe capillaries

Answer 34

Arterioles branch into capillaries, which are the smallest of the blood vessels. Substances are exchanges between cells and capillaries so they’re adapted for efficient diffusion. Capillaries are always found very near cells in exchange tissues so there is a short diffusion pathway. Their walls are only one cell thick which also shortens the diffusion pathway. There are a large number of capillaries to increase surface area for exchange. Networks of capillaries in tissue are called capillary beds

Question 35

What is tissue fluid?

Answer 35

Tissue fluid is the fluid that surrounds cells in tissues, it is made from substances that leave the blood (oxygen water and glucose and amino acids) cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it

Question 36

Describe the process of how substances leave the blood via tissue fluid

Answer 36

Substances move out of the blood capillaries into the tissue fluid by pressure filtration. At the start of the capillary bed, nearest the arterioles, the pressure inside the capillaries is greater than the pressure in the tissue fluid
The difference in pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid. As fluid leaves, the pressure reduces in the capillaries so the pressure is much lower at the end of the capillary bed that’s nearest to the veins
Due to the fluid loss, the water potential at the end of the capillaries nearest the veins is lower than the water potential on the tissue fluid so some water re enters the capillaries from the tissue fluid at the vein end by osmosis

Question 37

What does tissue fluid contain?

Answer 37

It doesn’t contain red blood cells or big proteins because they are too large to be pushed out through the capillary walls.

Question 38

What happens to excess tissue fluid?

Answer 38

It is drained into the lymphatic system which transports this excess fluid from the tissues and dumps it back into the circulatory system

Question 39

How does water enter a plant?

Answer 39

Water has to get from the soil, through the root and into the xylem, the system of vessels that transports water throughout the plant. The bit of the root that absorbs water is covered in root hairs, these increase the roots surface area speeding up water intake. Once it is absorbed the water has to get through the cortex, including the endodermis, before it can reach the xylem

Question 40

Describe the water potentials within the plant as water is getting absorbed

Answer 40

WAter always moves from areas of high water potential to areas of low water potential. Down the conc gradient. The soil around the roots generally has a high water potential and the leaves have a lower water potential. This creates a water potential gradient and keeps water moving through the plant in the right direction

Question 41

Describe the symplast pathway

Answer 41

The symplast pathway goes through the cytoplasm, the cytoplasm of neighbouring cells connect through plasmodesmata

Question 42

Describe the apoplast pathway

Answer 42

The apoplast pathway goes through the cell walls. The walls are very absorbent and water can simply diffuse through them, as well as passing through the spaces between them. When water in the apoplast pathway gets to the endodermis cells, it’s path is blocked by a waxy strip in the cell walls, called the casparian strip. Now the water has to take the symplast pathway. This is useful because it means water has to go through the cell membrane. cell membranes are able to control the entry and exit of the cell. So once past this Barrier, the water moves into the xylem

Question 43

How do cohesion and tension help water to move up plants?

Answer 43

1) water evaporates from the leaves at the top of the xylem
2) this creates tension which pulls more water into the leaf
3) water molecules are cohesive so when some are pulled into the leaf others follow which means the whole column of water in the xylem from the leaves down to the roots is moves upwards
4) water then enters the stem through the roots

Question 44

How does root pressure help to move water up through a plant?

Answer 44

When water is transported into the xylem in the roots, it creates a pressure and shoves water already in the xylem further upwards. This pressure is weak and couldn’t move water to the top of the bigger plants by itself but it is useful in small plants

Question 45

Describe transpiration

Answer 45

It is the evaporation of water from a plants surface, especially the leaves. Water evaporates from the moist cell walls and accumulates in the spaces between cells in the leaf. When the stomata open, it moves out of the leaf down the water potential gradient

Question 46

How does light affect transpiration rate?

Answer 46

The lighter it is, the faster the transpiration rate. This is because the stomata open when it gets light. When it is dark the stomata are usually closed so there is little transpiration.

Question 47

How does temperature affect transpiration rate?

Answer 47

The higher the temperature the faster the transpiration rate. Warmer water molecules have more energy so they evaporate from the cells inside the leaf faster. This increases the water potential gradient between the inside and outside of the leaf, making water diffuse out of the leaf faster

Question 48

How does humidity affect transpiration rates

Answer 48

The lower the humidity the faster the transpiration rate. If the air around the plant is dry, the water potential gradient between the lead and the air is increased, which increases transpiration

Question 49

How does wind affect transpiration rate?

Answer 49

The windier it is, the faster the transpiration rate. Lots of air movement blows away water molecules from around the stomata. This increases the water potential gradient, which increases the rare of transpiration

Question 50

How do you measure tanspiration?

Answer 50

By using a potometer. It is a special piece of apparatus that is used to estimate transpiration rates. It actually measures water uptake by a plant, but it’s assumed that waste uptake by the plant is directly related to water loss by the leaves

Question 51

How does a potometer work?

Answer 51

1) cut a shoot underwater to prevent air from entering the xylem. Cut it to a slant to increase the surface area.
2) assemble the potometer in water and insert the shoot under water, so no air can enter
3) remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water
4) check that the apparatus is water and air tight
5) dry the leaves, allow time for the short to acclimatise and then shut the tap
6) remove the end of the capillary tube from the beaker of water until one air bubble has formed, then put the end of the tube back in the water
7) record the starting position of the air bubble, then record the distance moved by the bubble per unit in time
8) repeat the experiment to increase the reliability of results