Exchange and Transport In Animals

Question 1

Features of an effective exchange surface

Answer 1

▪Thin layers so substances only have a short diffusion distance to diffuse making the process fast and efficient
▪ Good blood supply which ensures substances get into and out of the blood quickly which maintains a steep concentration gradient for diffusion
▪ Increased SA- provides the area needed for exchange so lots of substances can diffuse at once
▪ Good ventilation to maintain diffusion gradient

Question 2

Explain why single celled organisms do not need specialised exchange surfaces (3 marks)

Answer 2

Metabolic activity is relatively low(1) so relatively little oxygen needed or carbon dioxide produced (1) SA:V is large (1) so diffusion distance is small(1)

Question 3

Describe the main features of any effective exchange surface and explain how the structures relate to their functions (6 marks)

Answer 3

Large SA for exchange to overcome limitations of SA:V ratio of larger organisms (1); thin layers so distances substance have to diffuse short, making the process fast and efficient (1); Good blood supply so substances constantly delivered to and removed from exchange surface which maintains steep concentration gradient for diffusion (1) ventilation (for gaseous systems) maintains concentration gradients and makes the process more efficient (1)

Question 4

Why do insects need a gas exchange system?

Answer 4

1. They are extremely active organisms with a very high oxygen demand. Their gas exchange system has evolved to provide oxygen directly to the cells and remove CO2 the same way
2. They also have a protective exoskeleton through which little or no gas exchange can take place
3. They also don’t have any blood pigments that carry haemoglobin (the substance that carries oxygen)

Question 5

How does gas exchange take place in insects?

Answer 5

1. On the surface of the exoskeleton, there are small openings called spiracles which allows gases to diffuse in and out of the insect
2. Spiracles lead into a network of tubes called trachea, which are reinforced with chitin. Chitin is impermeable to gases so little or no gas exchange takes place in the trachea.
3. The trachea branches off to form tracheoles, which is a single elongated cell with no chitin so they are permeable to gases.

Question 6

Adaptations of the tracheoles for efficient gas exchange

Answer 6

1. The tracheoles are extremely close to the cells and this shortens the diffusion distance for gases between the cells and the tracheoles.
2. There is also a huge number of tracheoles which provide a very large SA for gas exchange
3. The ends of the tracheoles are filled with tracheal fluid which basically moves into the cell by osmosis when there’s a buildup of lactic acid, reducing the volume of the fluid and increasing the SA for the diffusion of oxygen and CO2

Question 7

What is an issue caused by the spiracles?

Answer 7

The spiracles allow water to leave the cell as well as allowing gases to diffuse. To minimize this water loss, insects have sphincters which keep the spiracles closed when the cell is inactive or has a low oxygen requirement

Question 8

What is the size of the trachea and tracheoles?

Answer 8

The trachea has a diameter of 1mm, and the tracheoles has a diameter of 1um or less

Question 9

Alternate methods of increasing the level of gaseous exchange

Answer 9

1. Mechanical ventilation of the tracheal system- muscular movement of the thorax and abdomen changes the volume of the thorax/abdomen which then changes the pressure in the trachea and tracheoles. As the pressure changes, air is forced in and out.
2. Air sacs which act as air reservoirs are used to increase the amount of air moved through the gas exchange system. They are usually inflated or deflated by the ventilating movement of the thorax and abdomen

Question 10

Why do bony fish need a gas exchange system?

Answer 10

1. Fishes are big and active organisms and so they have a very high oxygen demand
2. The oxygen concentration in water is lower than the oxygen concentration in the air so they need a way to get oxygen
3. They also have a low SA:V so they cannot just rely on diffusion to supply the oxygen their inner cells need
4. Bony fishes also have a scaly surface which do not allow gases to be exchanged

Question 11

How do bony fish exchange gases with the water?

Answer 11

They maintain a flow of water in one direction over the gills, which is where gaseous exchange takes place

Question 12

Structure of the gills

Answer 12

The gills are made up of thin plates called gill filaments which give a big SA for exchange of gases
The gill filaments are covered with lots of gill lamellae which increases the SA even more because of it’s large number
They also have a gill arch which supports the structure of the gills.

Question 13

Adaptations of the lamellae for efficient gas exchange.

Answer 13

1. They have a good blood supply due to them having lots of blood capillaries
2. Blood flows through the lamellae in one direction and water flows in the opposite direction. This maintains a steep concentration gradient between the water and the blood

Question 14

Process of water flow over the gills

Answer 14

When the mouth opens:
• the floor of the buccal cavity is lowered which ⬆️ the volume inside the buccal cavity and ⬇️ the pressure inside the buccal cavity. This causes water to move INTO the buccal cavity down a pressure gradient (from high pressure in the lake to low pressure in the buccal cavity)
• the opercular cavity expands while the operculum is kept SHUT and this increases the volume but decreases the pressure inside the opercular cavity. Because the pressure in the opercular cavity is lower than that in the BC, water moves across the gills into the OC down the pressure gradient)
When the mouth closes:
• the floor of the BC is raised and the opercular cavity closes. This causes the operculum to OPEN, decreasing the volume and increasing the pressure so water moves out of the operculum.

Question 15

Extra adaptations of fishes for effective gaseous exchange

Answer 15

▪Countercurrent exchange system: This mechanism is the idea that water moving over the gills and blood in the gill filaments flow in opposite directions. This maintains a steep concentration for oxygen and so more gaseous exchange can take place

Question 16

What is the parallel system?

Answer 16

It is the idea that water flowing over the gills and blood in the gill filaments are moving in the same direction. This gives an initial steep oxygen concentration between blood and water as diffusion takes place, until the oxygen concentration in the blood and water are in equilibirum, the no net movement of oxygen in the blood occurs

Question 17

Why do mammals need a gaseous exchange system?

Answer 17

Mammals are relatively big - they have a small SA: V ratio and a very
large volume of cells. They also have a high metabolic rate because they are active and maintain their body temperature independent of the environment. As a result, they need lots of oxygen for cellular respiration and they produce carbon dioxide, which needs to be removed. This exchange of gases takes place in the lungs.

Question 18

Features of the nasal cavity

Answer 18

• A large SA with a good blood supply which warms the air to body temperatures
• a hairy lining which secretes mucus to trap dust and bacteria, protecting delicate lung tissue from irritation and infection
• moist surfaces which warms and moistens the air before it enters the lungs

Question 19

Features of the trachea

Answer 19

• It is supported by incomplete rings of cartilage and the purpose of this is to let food move easily down the oesophagus. The cartilage also prevents the trachea from collapsing
• The walls of the trachea are lined with ciliated epithelium cells and goblet cells.

Question 20

What is the function of Goblet cells?

Answer 20

Goblet cells secrete mucus which traps dust particles and pathogens.

Question 21

What is the function of ciliated epithelium cells?

Answer 21

The ciliated epithelium cells has cilia extending from it’s cell membrane and the beating of the cilia moves the mucus to the throat where it gets swallowed and digested by stomach enzymes

Question 22

Features of the Bronchus

Answer 22

It is similar in structure to the trachea in the sense it has goblet cells, ciliated epithelium cells and cartilage but it is smaller in size

Question 23

Features of the Bronchioles

Answer 23

• The walls of the Bronchioles are lined with smooth muscles. When the smooth muscles contract, the bronchioles close up. When the smooth muscles relax, the bronchioles open up. This changes the amount of air that gets to the lungs

Question 24

Features of the alveoli

Answer 24

• They are the main gas exchange of the body
• Each alveolus consists of a single layer of thin, flattened epithelial cells, along with some collagen and elastic fibres which is composed of elastin. The elastic tissue allows the alveoli to stretch as air is drawn in, when they return to their resting size, they help squeeze the air out. This is known as the elastic recoil of the lungs

Question 25

Adaptations of the alveoli for effective gaseous exchange

Answer 25

• Large SA • Thin layers- both the alveoli and the capillaries that surround them have walls that are only a single epithelial cell thick, so the diffusion distances between the air in the alveolus and the blood in the capillaries are very short • Good blood supply- The alveoli in each lung are surrounded by a network of capillaries and the constant flow of blood through these capillaries bring CO2 and carries of oxygen, maintaining a stepp concentration gradient for both CO2 and O2 between the air in the alveoli and the blood in the capillaries

Question 26

What two muscles are involved in ventilation of the lungs?

Answer 26

The intercostal muscles and the diaphragm (which separates the thorax from the abdomen)

Question 27

What effect does this have on the amount of air?

Answer 27

Either inhalation (bringing air into the lungs) or exhalation(expelling air out of the lungs)

Question 28

Describe the process of inhalation

Answer 28

The diaphragm contracts and flattens and the external intercostal muscles contract moving the ribs upwards and outwards. This increases the volume of the thorax and so the pressure in the thorax decreases. This causes air to move into the lungs as the pressure inside the thorax is lower than atmospheric air

Question 29

Is inhalation a passive or active process?

Answer 29

It is an active process because it requires muscle contractions which requires energy

Question 30

Describe the process of exhalation

Answer 30

The diaphragm relaxes returning to its resting dome shape. The external intercostal muscles relax and this moves the ribs downwards and inwards. This decreases the volume inside the thorax and increases the pressure inside the thorax. This causes air to move out of the lungs because the pressure in the thorax is greater than the atmospheric pressure

Question 31

Is normal exhalation a passive or active process?

Answer 31

It is a passive process because the muscles are relaxing so it doesn't require energy

Question 32

Describe the process of forced exhalation

Answer 32

The internal intercostal muscles contracts, pulling the ribs down head and fast and the abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly

Question 33

Is forced expiration a passive or active process?

Answer 33

It is an active process cause it requires energy

Question 34

What is the function of pleural fluid?

Answer 34

It acts as a lubricant as the volume of the lung changes

Question 35

What are the 3 different ways aspects of the lungs can be measured?

Answer 35

• A peak flow meter is a simple device that measures the rate at which air can be expelled from the lungs. People who have asthma often uses these to monitor how well their lungs are working. • Vitalographs are more sophisticated versions of the peak flow meter. The patient being tested breathes out as quickly as they can through a mouthpiece, and the instrument produces a graph of the amount of air they breathe out and how quickly it is breathed out. •A spirometer is commonly used to measure different aspects of the lung volume, or to investigate breathing patterns.

Question 36

What is the tidal volume?

Answer 36

It is the amount of air that passes in and out of the lungs during a resting breath

Question 37

How can tidal volume be measured?

Answer 37

It is measured by measuring the distance from a trough to a peak

Question 38

What is the inspiratory reserve volume?

Answer 38

It is the maximum volume of air you can breathe in

Question 39

What is the expiratory reserve volume?

Answer 39

It is the maximum amount of additional air that can be forced out of the lungs after a normal breath

Question 40

What is the vital capacity?

Answer 40

It is the maximum amount of air that can be breathed out after breathing in as much as possible

Question 41

What is the residual volume?

Answer 41

It is the volume of air that I'd left in your lungs after maximum exhalation. It cannot be measured directly

Question 42

What is the breathing rate?

Answer 42

It is the number of complete breaths taken per minute. The number of complete breaths is the distance from a peak/trough to the next

Question 43

What is the ventilation rate?

Answer 43

It is the total volume of air inhaled in one minute

Question 44

Equation for ventilation rate

Answer 44

Ventilation rate= tidal volume × breathing rate (per minute)

Question 45

Describe how you could investigate breathing rates in a school laboratory.(3 marks)

Answer 45

Record numbers of breaths for a timed period and repeat (1); calculate means of results under different conditions (1); use spirometer to observe breathing rate(1)

Question 46

Describe the relationships between tidal volume, breathing rate, and oxygen uptake.(4 marks)

Answer 46

Ventilation rate is tidal volume multiplied by breathing rate(1); VR=TD×BR(1), Oxygen uptake closely related to ventilation rate, the more air is moved into the lungs, the more oxygen can be taken up by haemoglobin in blood(1); so as ventilation rate increases oxygen uptake also increases(1)

Question 47

A dog is under stress during a visit to the vet and pants but the ventilation rate remains steady. Suggest a possible explanation for these observations. (2 marks)

Answer 47

VR=TD×BR dog under stress so pants, breathes rapidly but breathes shallowly so although breathing rate increases, tidal volume falls(1) so ventilation rate stays the same (1)

Question 48

Why do animals need a specialized transport system?

Answer 48

• waste products of metabolism need to be removed from the cells and transported to excretory organs • molecules such as hormones or enzymes may be made in one place but needed in another • the metabolic demands of most multicellular animals are high(they need lots of oxygen and food, they produce lots of waste products) so diffusion over the long distances is not enough to supply the quantities needed

Question 49

Types of circulatory systems

Answer 49

Open and closed circulatory systems

Question 50

Features of most circulatory systems

Answer 50

1. They have a liquid transport medium that circulates around the system 2. They have vessels that carry the transport medium 3. They have a pumping mechanism to move the fluid around the system

Question 51

What is an open circulatory system?

Answer 51

It is a system in which the transport medium is not held in vessels. The blood is pumped straight from the heart to the body cavity (haemocoel) of the insect

Question 52

What is the transport medium in insects?

Answer 52

Their transport medium is called hemolymph which transports nutrients but doesn't carry oxygen

Question 53

Disadvantage of an open circulatory system

Answer 53

1. The amount of the transport medium flowing to tissues cannot be controlled 2. Since the fluid is not carried in vessels, they cannot move rapidly around the insect

Question 54

What is a closed circulatory system?

Answer 54

It is a system where the blood is held within vessels and so it doesn't come in direct contact with the cells of the body

Question 55

Advantage of closed circulatory system

Answer 55

1.The amount of blood flowing to a particular tissue can be controlled by contracting and dilating blood vessels 2. The blood moves rapidly to the heart

Question 56

Types of closed circulatory systems

Answer 56

Single and double closed circulatory systems

Question 57

What is a single closed circulatory system?

Answer 57

Blood flows through the heart **once** in one complete circulation of the body

Question 58

Disadvantage of a single closed circulatory system?

Answer 58

Blood flows through two sets of capillaries which lower the blood pressure and so it moves slowly to the heart. This limits the efficiency of the exchange process so the activity level of the animal is relatively low

Question 59

What is a double closed circulatory system?

Answer 59

It is a system in which blood flows through the heart **twice** in one complete circulation of the body

Question 60

Features of some blood vessels

Answer 60

• Elastic fibres - these are composed of elastin and can stretch and recoil, providing the blood vessel walls with flexibility • Smooth muscle - contracts or relaxes which change the size of the lumen • collagen- provides structural support to maintain the shape and volume of the vessel

Question 61

What is the function of the arteries?

Answer 61

To carry oxygenated blood away from the heart to body tissues under high pressure

Question 62

What artery carries deoxygenated blood?

Answer 62

The pulmonary artery which carries deoxygenated blood away from the heart to the lungs

Question 63

Structure of the Arteries

Answer 63

1. It has thick walls to withstand the high pressure of the blood 2. Consists of smooth muscle which controls blood flow by changing the diameter of the lumen 3. Consists of elastic fibres which allows the arteries to expand to allow the surge of high pressure blood pass down and recoils when the heart relaxes. 4. Consists of a thin layer of endothelial cells which provide a smooth surface for blood flow and reduces friction

Question 64

Function of the arterioles

Answer 64

Delivers blood to the capillaries

Question 65

Structure of the arterioles

Answer 65

1. It has **thinner** elastic fibres and collagen because the blood pressure is lower than in the arteries so it has a weaker blood surge 2. It has **thicker** smooth muscle layer because they control the blood flow passing through the capillaries to individual organs

Question 66

What is vasoconstriction?

Answer 66

This is when the smooth muscles contract preventing blood flow to the capillaries

Question 67

What is vasodilation?

Answer 67

This is when the smooth muscles relax, allowing blood blood to the capillaries

Question 68

Function of the capillaries

Answer 68

It is the site of gas/substance exchange in tissues

Question 69

Structure of the capillaries

Answer 69

1. They have a thin wall consisting of a single layer of endothelial cells which shortens the diffusion distance between the blood and the cells near the capillary increasing diffusion rate of molecules between the blood and the cells 2. They also have an extensive branching of capillaries which provides a large SA for exchange of materials 3. It also has tiny gaps between the cells and this allows fluid to pass out of the blood- tissue fluid

Question 70

Function of the veins

Answer 70

Carries deoxygenated blood into the heart from the body cells

Question 71

What two veins carry oxygenated blood into the heart?

Answer 71

1. Pulmonary veins carry oxygenated blood from the lungs into the heart 2. Umbilical veins carry oxygenated blood from the placenta to the foetus

Question 72

Structure of the veins

Answer 72

1. They have thinner walls because they don't have to withstand the high pressure blood 2. They have a thin layer of endothelial cells which provide a smooth surface for blood flow. 3. They have a larger lumen because they carry a large volume of blood 4. Veins have **valves** which prevents the backflow of blood into the heart 5. They have thinner smooth muscle and elastic fibres because the blood does not travel in pulses so there's no elastic recoil

Question 73

Function of venules

Answer 73

They link the capillaries and the veins

Question 74

Structure of the venules

Answer 74

1. They have thin walls with little smooth muscles because they don't have to withstand any high pressure blood nor control blood flow