Gas Exchange In Small Organisms

Question 1

What are the processes by which substances are exchanged?

Answer 1

Diffusion
Active transport

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.

Question 2

What is an exchange surface?

Answer 2

A surface on/inside an organism over which exchange of gases, nutrients, and waste can take place

Exchange surfaces are critical for maintaining homeostasis in organisms.

Question 3

What is a respiratory surface?

Answer 3

The site of gas exchange in/on an organism

Respiratory surfaces are essential for the uptake of oxygen and the release of carbon dioxide.

Question 4

What is gas exchange?

Answer 4

The diffusion of gases down their concentration gradient across a respiratory surface, between the organism and its environment

Gas exchange is vital for cellular respiration.

Question 5

List the features of a specialised exchange surface.

Answer 5

• Large surface area: Volume ratio
• Thin - small number of plasma membranes
• Permeable / semi-permeable
• 1 cell thick walls of organs/tissues or cells
• Movement of external and internal environment to maintain a concentration gradient

These features enhance the efficiency of gas exchange.

Question 6

True or False: All plasma membranes are the same thickness.

Answer 6

True

The thickness of plasma membranes is consistent, but the number of membranes that need to be crossed can vary.

Question 7

Fill in the blank: The walls of organs/tissues or cells in exchange surfaces are usually _______.

Answer 7

1 cell thick

This characteristic minimizes the distance for diffusion.

Question 8

What maintains a concentration gradient in exchange surfaces?

Answer 8

Movement of external and internal environment

Maintaining a concentration gradient is essential for effective diffusion.

Question 9

What is the gas exchange system of fish?

Answer 9

The gill apparatus

The gill apparatus is essential for oxygen uptake and carbon dioxide release in aquatic environments.

Question 10

Why do fish need gas exchange systems?

Answer 10

• Small surface area: volume ratio
• Higher oxygen requirement
• Waterproof skin (gas-proof)

These factors necessitate an efficient system for gas exchange in fish.

Question 11

What are the two types of fish based on their skeletal structure?

Answer 11

• Cartilaginous fish
• Bony fish

Cartilaginous fish have skeletons made of cartilage, whereas bony fish have skeletons made of bone.

Question 12

Give examples of cartilaginous fish.

Answer 12

• Shark
• Sting ray

Cartilaginous fish are characterized by their flexible skeletal structure.

Question 13

Give examples of bony fish.

Answer 13

• Carp
• Catfish
• Tuna
• Seahorses

Bony fish have a rigid skeletal structure made of bone.

Question 14

How many gill pouches do cartilaginous fish have?

Answer 14

Five full pouches on each side

These pouches open to the outside at gill slits.

Question 15

What are the two main reasons the ventilation system of cartilaginous fish is less efficient than that of bony fish?

Answer 15

• They lack a ventilation mechanism to force water over the gills
• Blood flows in parallel with the water in the gill

This leads to less effective oxygen absorption compared to bony fish.

Question 16

What happens to the blood flow in cartilaginous fish during gas exchange?

Answer 16

Blood moves in parallel flow with the water

This means both the blood and water flow in the same direction, limiting oxygen concentration in the blood.

Question 17

What is the maximum oxygen concentration of the blood compared to the water in cartilaginous fish?

Answer 17

50% compared to the water

This occurs because equilibrium is reached between the water and blood oxygen concentrations.

Question 18

True or False: Gas exchange in parallel flow occurs continuously across the whole gill lamellae.

Answer 18

False

Gas exchange can only occur until the oxygen concentration in the blood and water is equal.

Question 19

What is the function of gill filaments?

Answer 19

Each gill has many of these stacked on top of each other. They increase the surface area of the gills.

Question 20

What is the function of gill lamellae?

Answer 20

These are found on the gill filaments, perpendicular to their surface. They increase surface area of the gills.

Question 21

What is the function of gill rakers?

Answer 21

These seive water of harmful grit and particles before the water is passed over the delicate gills.

Question 22

What is the function of gill arches?

Answer 22

These support the gills behind the head and offer an attachment point.

Question 23

What are spiracles?

Answer 23

Allows air to enter/exit the body

Spiracles contain valves and paired holes to prevent water loss

Question 24

What is the function of the trachea?

Answer 24

Brings air to tracheoles

The trachea is strengthened by rings of chitin

Question 25

What do tracheoles do?

Answer 25

Bring respiratory gases to and from body tissues ## Footnote Thin, moist walls improve gas exchange and they penetrate all body tissues maintaining short diffusion distance

Question 26

List some adaptations insects have towards preventing water loss.

Answer 26

* Valves in spiracles

Question 27

How does the insect exchange system obey Fick's Law to ensure rapid diffusion of gases?

Answer 27

* Maximises surface area by small diameter and large comparative surface area * Minimises diffusion distance by thin moist walls of tracheoles * Maintains diffusion gradient by low oxygen and high carbon dioxide at one end of tracheoles compared to outside atmosphere

Question 28

How does the fluid at the tips of the tracheoles enhance gas exchange?

Answer 28

Gases dissolve in water and diffuse down concentration gradient

Question 29

Why are insects so small?

Answer 29

Air can only travel so quickly in tiny spaces by diffusion, limiting growth without a different respiratory system ## Footnote Examples of different respiratory systems include lungs and gills

Question 30

In which phase does diffusion take place in leaves?

Answer 30

Gas phase ## Footnote Diffusion occurs faster in the gas phase.

Question 31

What are stomata?

Answer 31

Tiny pores on leaves which gases diffuse through ## Footnote Stomata can be opened and shut by guard cells.

Question 32

What controls the rate of gas exchange in leaves?

Answer 32

Guard cells ## Footnote Guard cells regulate stomatal opening and closing.

Question 33

What happens when guard cells lose water?

Answer 33

They become flaccid and close the stomata ## Footnote This prevents excessive water loss.

Question 34

When are stomata usually closed?

Answer 34

At night ## Footnote There is no sunlight for photosynthesis.

Question 35

What is the effect of very bright light or drought on stomata?

Answer 35

They stay closed to minimize water loss ## Footnote Preventing complete water loss is impossible.

Question 36

What happens during the day concerning photosynthesis and respiration?

Answer 36

Photosynthesis rate is higher than respiration rate ## Footnote This leads to oxygen diffusion out of the plant.

Question 37

What is the photosynthesis equation?

Answer 37

6CO2 + 6H2O = C6H12O6 + 6O2 ## Footnote This represents the process of converting carbon dioxide and water into glucose and oxygen.

Question 38

What is the respiration equation?

Answer 38

C6H12O6 + 6O2 = 6CO2 + 6H2O ## Footnote This represents the process of converting glucose and oxygen back into carbon dioxide and water.

Question 39

What is needed for both photosynthesis and respiration?

Answer 39

Energy ## Footnote Energy is required for the chemical reactions in both processes.

Question 40

What occurs at night regarding gas exchange in plants?

Answer 40

Respiration rate is higher than photosynthesis rate ## Footnote This leads to carbon dioxide diffusing out of the plant.