Organisms exchanges substances with their environment

Question 1

Why does a high SA:V ratio benefit small organisms?

Answer 1

It allows efficient diffusion of gases and nutrients.

Question 2

How does size affect SA:V ratio in organisms?

Answer 2

Larger size decreases SA:V ratio, affecting exchange efficiency.

Question 3

Why do alveoli in lungs increase for gas exchange?

Answer 3

Alveoli increase surface are for effective gas exchange.

Question 4

Why do larger organisms need circulatory systems?

Answer 4

They transport substances to compensate for lower SA:V.

Question 5

What shape adaptation helps flatworms in gas exchange?

Answer 5

Their flattened shape increases surface area to volume ration.

Question 6

What is a key adaptation of the small intestine?

Answer 6

Microvilli provide a large surface area for nutrient absorption.

Question 7

Why do organisms lose heat faster with a high SA:V ratio?

Answer 7

More surface are leads to greater heat loss to the environment.

Question 8

What role does concentration gradient play in gas exchange?

Answer 8

It enhances diffusion; maintained by systems like blood flow.

Question 9

How do adaptations help larger organisms with SA:V?

Answer 9

They develop specialised structures for efficient exchange.

Question 10

How might larger organisms adapt to compensate for for its small SA:V ratio?

Answer 10

Changes that increase surface area e.g. folding; body parts become larger e.g. elephants ears; elongating shape; developing a specialised gas exchange surface.

Question 11

Explain an insects gas exchange.

Answer 11

Insects have evolved an internal network of tubes called tracheae. The tracheae are supported by strengthened rings to prevent them from collapsing. The tracheae divide into smaller dead-end tubes called tracheoles.
The tracheoles extend throughout all the body tissues of the insect. In this way atmospheric air, with the oxygen it contains, is brought directly to the respiring tissues, as there is a short diffusion pathway from a tracheole to any body cell.

Question 12

State three ways respiratory gases move in and out of the tracheal system.

Answer 12

• Along a diffusion gradient
• Mass transport
• The ends of the tracheoles are filled with water

Question 13

Describe the 3 ways respiratory gases move in and out of the tracheal system.

Answer 13

Diffusion gradient- Oxygen is used up in respiring cells concentration decreases towards the end of tracheoles, creating a diffusion gradient. Carbon dioxide is also produced by respiring cells this creates a diffusion gradient in the opposite direction.

Mass transport - Contraction of muscles in squeezes trachea enabling mass movement of air in and out.

Ends of the tracheoles are filled with water - Muscle cells around tracheoles carry out some anaerobic respiration, this produces lactate (soluble), which reduces the water potential of muscle cells. Water moves into cells by osmosis from tracheoles. So, water in the end of the tracheoles decrease in volume and draw more air into them.

Question 14

Describe how gases enter and leave the tracheae.

Answer 14

Through pores called spiracles.
Water vapour + CO2 is lost when spiracles open, Oxygen is taken in
(insect circulatory system doesn’t transport oxygen. delivered to cells by tracheoles)

Question 15

What is a limitation of the tracheal system in insects for gas exchange?

Answer 15

Relies on diffusion. Diffusion pathway needs to be short, so insects must be small. Limiting the size insects can attain.

Question 16

Describe the surface area to volume ratio of a single-celled organism.

Answer 16

Single-celled organisms are small, and therefore have a large surface area to volume ratio.

Question 17

What are spiracles?

Answer 17

External openings of the tracheal system on the exoskeleton along the abdomen and thorax.

Question 18

How are tracheae adapted for insect gas exchange?

Answer 18

-Reinforced with spirals of chitin - This prevents collapsing.
-Multiple tracheae - This increases surface area.

Question 19

How are tracheoles adapted for insect gas exchange?

Answer 19

-Penetrate directly into tissues - This reduces the gas diffusion distance.
-Thin walls - These reduce the gas diffusion distance.
-Highly branched - This maximises the surface area.
-Not reinforced with chitin - This allows gas exchange to occur.
-Fluid at the ends of the tracheoles (tracheal fluid) - This allows oxygen to dissolve to aid diffusion and reduces water loss.

Question 20

How are spiracles adapted for insect gas exchange?

Answer 20

-Can open and close - This allows them to control gas exchange with the atmosphere and minimise water loss.

Question 21

Describe gas exchange in insects.

Answer 21

1) Air enters the tracheal system through open spiracles.
2) Air moves into larger tracheae and diffuses into smaller tracheoles.
3) Tracheoles branch throughout the body, transporting air directly to cells.
4) Oxygen dissolves in water in tracheal fluid and diffuses down its concentration gradient from tracheoles into body cells.
5) Carbon dioxide diffuses down its concentration gradient out of body cells into the tracheoles.
6) Air is then carried back to the spiracles via the tracheae and released from the body.

Question 22

Why do insects need efficient systems for exchanging gases?

Answer 22

• To deliver oxygen to cells - (This allows aerobic respiration to occur to release energy for cellular processes).
• To remove carbon dioxide from cells - (The build up of carbon dioxide produced as a waste product of respiration reduces pH, which can denature enzymes).

Question 23

What maintains the concentration gradients between the tissues and air in the tracheal system?

Answer 23

• Cells using up oxygen for respiration - This keeps oxygen concentration low in cells.
• Cells producing carbon dioxide in respiration - This keeps carbon dioxide concentration high in cells.
• Continuous ventilation - Fresh air is supplied to the tracheal system via spiracles.

Question 24

Do fish have a large or small surface area to volume ratio? Explain why and what does this mean for its gas exchange system?

Answer 24

Small surface area to volume ratio as there bodies are not adequate to supply and remove their respiratory gasses therefore they have a specialised gas exchange surface: Gills

Question 25

Gill filaments.

Answer 25

Finger-like projections through which gases enter and leave the blood system-used for respiration and they are stacked up in a pile.

Question 26

Gill lamellae.

Answer 26

Gill lamellae. At right angle to gill filaments, which increase the surface area of the gills.

Question 27

What is it called when water and blood flow in opposite directions?

Answer 27

Counter-current flow.

Question 28

Why does the opposite flow of blood and oxygen maintain a concentration gradient?

Answer 28

Blood that is well loaded with oxygen meets water. Water has a maximum concentration of oxygen. Therefore diffusion of oxygen from water into the blood takes place along a concentration gradient. Blood with little oxygen meets water which has the most but not all oxygen removed. Again diffusion of oxygen from water to blood takes place. Therefore diffusion concentration of oxygen is maintained across the entire width of the gill lamellae.

Question 29

Explain how the relationship between the direction of flow of the water and of the blood is useful to the fish.

Answer 29

As there is a counter-current flow which maintains the concentration gradient across the whole gill so more oxygen will enter the blood so there is more aerobic respiration.

Question 30

Explain how the gills of a fish are adapted for efficient gas exchange?

Answer 30

Gills have lamellae which increase surface area for increased diffusion of oxygen. Thin epithelium walls which decreases diffusion distance into capillaries which increases the rate of diffusion. Water and blood flow in opposite directions which maintains a concentration gradient as blood always has a lower oxygen concentration. Circulation of blood by capillaries replaces saturated blood with oxygen.

Question 31

How are leaves well adapted for gas exchange?

Answer 31

- Air spaces allow carbon dioxide to diffuse. - Irregular spongy mesophyll layer increases the SA:V ratio. - Stomata allow gases to diffuse in and out.

Question 32

How does the waxy cuticle help to reduce water loss?

Answer 32

Thick waxy cuticle means there is an impermeable layer which reduces evaporation from the surface. Its thickness also increases the distance for diffusion.

Question 33

Adaptations of leaves to reduce water loss in xerophytes (plants that live in environments with little water).

Answer 33

- Thicker leaves or needles so there is a smaller surface area for water loss. - Thick waxy cuticle which is impermeable increases diffusion distance and reduces evaporation from the surface. - Hairs on the surface of leaves trap a layer of moisture so the water potential gradient is reduced. - Sunken stomata are surrounded by a trapped layer of moisture which reduces the water potential gradient. - Curled leaves traps air saturated with water vapour which reduces the water potential gradient. - Fewer stomata so there is a reduced surface area for water loss.

Question 34

How do hairs on the leaves help to reduce water loss?

Answer 34

Hairs on leaves trap a layer of moisture around the leaf which reduces the water potential gradient so less water is lost by osmosis.

Question 35

How does leaf size affect the rate of water loss?

Answer 35

Smaller leaves or needles mean that there is a smaller surface area so less evaporation can take; rate of water loss is decreased.

Question 36

How do rolled leaves affect the rate of water loss?

Answer 36

Rolling up leaves protects the underside of the leaf and traps a layer of air within the leaf. This air becomes saturated with water vapour, thus reducing the water potential gradient and therefore decreases the rate of water loss.

Question 37

How does sunken stomata help to reduce water loss?

Answer 37

Stomata are in pits i.e. sunken, so moist air is trapped close to stomatal aperture (opening) so the water potential gradient is reduced; reduces water loss.

Question 38

How are insects adapted to limit water loss?

Answer 38

- Small surface area to volume ratio. - Waterproof coverings. - Spiracles.

Question 39

How are insects waterproof?

Answer 39

Rigid outer skeleton of chitin covered in a waterproof covering.

Question 40

How do spiracles reduce water loss in insects?

Answer 40

Close when insect is at rest so to not limit oxygen intake.

Question 41

Why can't pants have a small SA:V ratio to limit water loss?

Answer 41

Need a large leaf SA to capture light and exchange of gases for photosynthesis.

Question 42

How are plant leaves adapted to reduce water loss?

Answer 42

- Stomata open and close. - Thick cuticles. - Rolled up leaves. - Hairy leaves. - Stomata in pits and grooves. - Reduced SA to vol ratio.

Question 43

How does gas exchange contrast with water loss?

Answer 43

Gas exchange requires thin permeable membranes with large SA to maximise diffusion. This allows a lot of water to diffuse out the cells of an organism.

Question 44

Define the term breathing.

Answer 44

The movement of air into and out of the lungs.

Question 45

Define the term ventilation.

Answer 45

The scientific word for breathing.

Question 46

Define the term respiration.

Answer 46

Chemical reaction to release energy in the from of ATP.

Question 47

Define the term gaseous exchange.

Answer 47

Diffusion of O₂ from the air in the alveoli into the blood and of CO₂ from the blood into the alveoli.

Question 48

What makes up the human gas exchange system?

Answer 48

- Alveol - Bronchioles - Bronchi - Trachea - Lungs

Question 49

What are the two key muscles involved in ventilation?

Answer 49

- Diaphragm. - Antagonistic interaction between the external and internal intercostal muscles.

Question 50

What does the contraction of the external intercostal muscles lead to?

Answer 50

Inspiration.

Question 51

What does the contraction of the internal intercostal muscles lead to?

Answer 51

Expiration.

Question 52

What happens to the ribcage when the external intercostal muscles contract?

Answer 52

This pulls the ribcage up and outwards.

Question 53

What happens to the ribcage when the internal intercostal muscles contract?

Answer 53

Pulls the ribcage in and downwards.

Question 54

Describe the lung volume during inspiration.

Answer 54

Increases (to decrease pressure).

Question 55

How does air move (down the concentration gradient), during inspiration?

Answer 55

Air moves into the lungs, from atmosphere into lower pressure.

Question 56

What happens to the diaphragm during expiration?

Answer 56

Relaxes (returns to domed position).

Question 57

What happens to the diaphragm during inspiration?

Answer 57

Contracts (and moves downwards).

Question 58

What happens to the volume in the lungs during expiration?

Answer 58

Decrease (to increase pressure).

Question 59

How does air move (down the pressure gradient), during expiration?

Answer 59

Air moves out lungs, from high pressure to atmosphere pressure.

Question 60

What is an alevoli?

Answer 60

Tiny air sacks.

Question 61

What adaptations in the alveoli allow for a large surface area?

Answer 61

There are 300 million in each human lung which creates a very large surface area for gas exchange.

Question 62

What adaptations in the alveoli allow for a thin diffusion distance?

Answer 62

The alveoli epithelium cells are very thin, to minimise diffusion distance.

Question 63

What adaptations in the alveoli allow for a maintenance of concentration gradient?

Answer 63

Each alveoli is surrounded by a network of capillaries to remove exchanged gases, and therefore maintains a concentration gradient.

Question 64

Once the gases are in the alveoli, what do the gases exchange between?

Answer 64

Epithelium and the blood.

Question 65

Explain how inspiration happens.

Answer 65

- The external intercostal muscles contract, while the internal intercostal muscles relax. - The ribs are pulled upwards and outwards, increasing the volume of the thorax (upper part of the body). - The diaphragm muscles contract, causing it to flatten, this also increases the volume of the thorax. - The increased volume of the thorax results in the reduction of pressure in the lungs. - Atmospheric pressure is now greater than pulmonary pressure (lung pressure), so air is forced into the lungs.

Question 66

Explain how expiration happens.

Answer 66

- The internal intercostal muscles contract, while the external intercostal muscles relax. - The ribs move downwards and inwards, decreasing the volume of the thorax. - The diaphragm muscles relax and it is pushed up again by the contents of the abdomen that were compressed during inspiration. The volume of the thorax is therefore further decreased. - The increased volume of the thorax increases the pressure in the lungs. - This increased pressure means that external air pressure is lower than the pulmonary pressure, so air is forced out of the lungs.

Question 67

Comment on the energy required for both inspiration and expiration.

Answer 67

- Inspiration is an active process, it needs energy to work. - Expiration is a largely passive process, although it requires some energy to contract the internal intercostal muscles, most of the muscles are relaxed in this process.

Question 68

What is the diaphragm?

Answer 68

A sheet of muscle that separates the thorax from the abdomen.

Question 69

What are the intercostal muscles?

Answer 69

These are the muscles between the ribs that allow for the expansion/compression of the thoracic cavity.

Question 70

How do you calculate the pulmonary ventilation rate?

Answer 70

Pulmonary ventilation rate = tidal volume (volume of air which is taken in on each breath) x breathing rate dm^3 min^-1 = dm^3 x min^-1

Question 71

Describe how oxygen in the alveoli enters the blood capillaries.

Answer 71

- Oxygen diffuese through the epithelium of the alveoli. - and through the endothelium of the blood capillaries.

Question 72

Circulation of the blood helps to maintain this difference in oxygen concentration. Explain how.

Answer 72

Replaces blood with a high concentration of oxygen with blood with a low concentration of oxygen.

Question 73

In healthy lungs, a gradient is maintained between the concentration of oxygen in the alveoli and the concentration of oxygen in the lung capillaries. Describe how ventilation helps to maintain this difference in concentration.

Answer 73

- Air with a higher oxygen concentration drawn into lungs upon inspiration - Air with a lower oxygen concentration removed from lungs upon expiration.