Exchange and Transport in Animals

Question 1

What substances need to be transported into and out of the body and why?

Answer 1

Oxygen for aerobic respiration, which produces carbon dioxide as a waste product. These gases move in/out of cells via diffusion
water-taken up by cells by osmosis. in animals dissolved food molecules and mineral ions diffuse along with it
urea- a waste product produced from proteins which is toxic to animals- diffuses from cells to blood plasma for removal by the kidneys.

Question 2

What are the adaptations of the lungs for gas exchange?

Answer 2

The lungs contain millions of little air sacs called alveoli where gas exchange takes place. The alveoli are specialised to maximise diffusion of oxygen and carbon dioxide. They have a moist lining for dissolving gases; a good blood supply to maintain concentration gradients of oxygen and carbon dioxide; very thin walls to minimise the distance that gases have to move and an enormous surface area (c.75m^2 in humans) so an enormous surface area to volume ratio.

Question 3

What is the importance of surface area:volume ratios in transport systems?

Answer 3

In single celled organisms substances can diffuse directly into/out of the cell as it has a large surface area to volume ratio (SA:V) so enough substances ca be exchanged across the membrane to supply the volume of the cell. multicellular organisms have a smaller SA:V so need an exchange surface for efficient diffusion and a mass transport system to move substances between the exchange surface and the rest of the body.

Question 4

What affects rate of diffusion?

Answer 4

Distance- less distance, more diffusion
Concentration gradient- higher gradient, more diffusion
Surface area- higher surface area, more diffusion

Question 5

What is Fick’s Law?

Answer 5

rate of diffusion∝ (surface area x concentration difference)/thickness of membrane

Question 6

What are the components and function of the circulatory system?

Answer 6

The circulatory system transports substances around the body in the bloodstream.
Blood, Blood vessels, heart

Question 7

What is the function of arteries and how are they adapted?

Answer 7

Arteries carry blood away from the heart. The heart pumps blood out at high pressure so the artery walls are thick compared to the size of the lumen (hole down the middle) and contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back.

Question 8

What is the function of capillaries and how are they adapted?

Answer 8

Arteries branch into capillaries, which are too small to detect with the naked eye. They are narrow, to be able to fit into gaps between cells, so they can carry blood to every cell in the body to exchange substances with them. They have permeable walls to allow substances to diffuse in and out. They supply food and oxygen and take away waste like carbon dioxide. Their walls are normally only 1 cell thick to increase rate of diffusion.

Question 9

What is the function of veins and how are they adapted?

Answer 9

Veins carry blood back to the heart. Capillaries join up to form them. Blood is at lower pressure than the arteries so the walls don’t need to be as thick. They have a bigger lumen so blood can flow despite low pressure. valves keep blood flowing in the right direction.

Question 10

What is the function of erythrocytes (red blood cells) and how are they adapted?

Answer 10

To carry oxygen from the lungs to the rest of the body.
Biconcave disc shape gives large surface area for absorbing oxygen. No nucleus- more space to carry oxygen. Contain haemoglobin, which binds to oxygen in the lungs to form oxyhaemoglobin and splits into haemoglobin and oxygen in body tissues to release oxygen to cells.

Question 11

What are the functions of phagocytes and lymphocytes and how are they adapted?

Answer 11

Phagocytes: white blood cells that can change shape to engulf unwelcome microorganisms (phagocytosis)
Lymphocytes: white blood cells that can produce antibodies against microorganisms. Some also produce antitoxins to neutralise toxins produces by the microorganisms.
When you have an infection, white blood cells multiply to fight it off so a blood test will show a high white blood cell count.

Question 12

describe the functions of blood platelets

Answer 12

small fragments of cell with no nucleus which help blood to clot at a wound to stop blood loss and infection. Lack of platelets causes excessive bleeding and bruising.

Question 13

What is the function of blood plasma?

Answer 13

Plasma- pale straw coloured liquid which transports substances: red &white blood cells & platelets, nutrients like glucose and amino acids which are the soluble products of digestion which are absorbed from the gut and taken to the body’s cells, carbon dioxide from organs to the lungs, urea from the liver to the kidneys, hormones, proteins, antibodies and antitoxins

Question 14

Describe the flow of blood through the heart

Answer 14

The right atrium of the heart receives deoxygenated blood from the body through the vena cava. Deoxygenated blood moves through to the right ventricle which pumps it to the lungs via the pulmonary artery. The left atrium receives oxygenated blood from the lungs via the pulmonary vein which then moves through to the left ventricle which pumps it out round the whole body via the aorta.

Question 15

What is a double circulatory system?

Answer 15

Mammals have it. The heart pumps blood around the body in two circuits- to the lungs to take in oxygen and around the rest of the body to deliver oxygen. Fish have a single circulatory system- deoxygenated blood from the fish’s body flows to the heart which pumps it around the body in a single circuit via the gills where it picks up oxygen

Question 16

How is the heart adapted to its function?

Answer 16

The left ventricle has a thicker wall than the right ventricle . It needs more muscle as it has to pump blood around the whole body at high pressure whereas the right ventricle only has to pump it to the lungs. valves prevent the backflow of blood in the heart.

Question 17

How do you calculate cardiac output?

Answer 17

cardiac output (cm^3 min^-1) =heart rate (bpm) x stroke volume (cm^3)

Question 18

Why do organisms need to respire?

Answer 18

Energy is needed for metabolic processes (e.g. making larger molecules from smaller ones); contracting muscles (in animals) and maintaining a steady body temperature (in mammals and birds).

Question 19

What is respiration?

Answer 19

the process of transferring energy from the breakdown of organic compounds (usually glucose).

Question 20

What is aerobic respiration?

Answer 20

Occurs when there is a plentiful oxygen supply. the most efficient way to transfer energy from glucose, occurs constantly in plants and animals.
Glucose + oxygen -> carbon dioxide + water
C6H12O6 + 6O2-> 6CO2 + 6H2O

Question 21

What is anaerobic respiration?

Answer 21

Oxygen not needed. Transfers less energy than aerobic so is less efficient. Glucose is only partially broken down and lactic acis is also produced in animals. A build up of lactic acid leads to cramp. 
Glucose->lactic acid
In plants (and fungi), ethanol and carbon dioxide is produces instead of lactic acid.

Question 22

Why is respiration exothermic?

Answer 22

Energy is transferred to the environment, some of it by heating