Exchange and transport systems: Gas exchange - fish, insects, plants, and single celled organisms

Question 1

State what gas exchange occurs over

Answer 1

A gas exchange surface

Question 2

What is a gas exchange surface

Answer 2

A boundary between the outside environment and internal environment of an organism

Question 3

What do most gas exchange surfaces have in common that increases the rate of diffusion

Answer 3

• They have a large surface area
• They are thin (providing a short diffusion pathway)
• Steep concentration gradient maintained across the exchange surface

Question 4

Why do single celled organisms not need a specialised gas exchange system

Answer 4

They have a large surface area to volume ratio and a short diffusion pathway

Question 5

Where does gas exchange occur in fish

Answer 5

In the gills

Question 6

What do the gills consist of

Answer 6

A series of bony gill arches, each with two stacks of gill filaments

Question 7

How do single celled organisms exchange gases

Answer 7

Substances diffuse across their outer body surface

Question 8

What system do fish use for gas exchange

Answer 8

Counter current system

Question 9

What are the adaptation fish have to increase gas exchange

Answer 9

• Gills are made of gill filaments providing a large surface area for exchange of gases that contains lamellae
• This increases the surface area further
• Counter current system - Blood flows through Lamella in one direction and water flows over in the opposite direction
• This maintains a large concentration gradient between the water and the blood
• Capillaries that are found in the gill lamellae are one cell thick - providing a short diffusion pathway

Question 10

What circulatory system do fish have

Answer 10

Single circulatory system

Question 11

How does the counter current system increase gas exchange

Answer 11

• It maintains a steep concentration gradient between water and blood
• So the concentration of oxygen in the water is always higher that that in the blood, meaning as much oxygen as possible diffuses from the water into the blood

Question 12

Name and describe features of the gill filaments that increases the rate of gas exchange

Answer 12

• Protruding rows of very thin lamellae - increases surface area

Question 13

How does the addition of lamellae in gill filaments increase surface area

Answer 13

• Each lamella consists of a network of capillaries covered by a single layer of epithelium (thin diffusion pathway)

Question 14

What is the operculum in fish

Answer 14

A flap of tissue covering the gills of the fish

Question 15

What is the counter-current system in fish

Answer 15

When blood flows through the gills in the opposite direction as the water flowing over the gills

Question 16

What do insects use to exchange gases

Answer 16

The tracheal system

Question 17

Name the organisation of the features of the tracheal system

Answer 17

Spiracle → Tracheae → Tracheoles

Question 18

What are the walls of the tracheae reinforced with in fish

Answer 18

Chitin

Question 19

What does the addition of chitin do to the tracheae

Answer 19

It prevents the tracheae from collapsing when the insect

Question 20

What is a spiracle

Answer 20

A pore on the surface of insects which are respiratory openings found on the thorax and abdomen, connected to the trachea

Question 21

What is a tracheae in insects

Answer 21

Internal network of tubes of tubes

Question 22

What is a tracheole in insects

Answer 22

Smaller internal network of tubes that branches from the tracheae

Question 23

What is an exoskeleton

Answer 23

An external supportive covering on the outside of the body

Question 24

What are the problems when the spiracle in insects are closed

Answer 24

Carbon dioxide can build up in the insect creating and increased gradient for outward diffusion when they open

Question 25

What are the problems when the spiracle in insects are open

Answer 25

Water vapour can evaporate from the insect and humidity can be lost

Question 26

How does the abdomen support gas exchange in insects

Answer 26

• Rhythmic abdominal movements a mass flow of air into the tracheal systems by creating pumping movement for ventilation

Question 27

Are tracheoles supported by chitin

Answer 27

No

Question 28

Name features of the tracheole that are beneficial to its function

Answer 28

• They are have a narrow diameter
• They are are extremely close to cells
• They are thin and permeable

Question 29

How does gas exchange occur in the tracheal system in insects

Answer 29

• Air move into tracheae through pores on the surface called spiracles
• Oxygen travels down the concentration gradient towards the respiring cells
• The tracheae branch off into smaller tracheoles , which have a thin, permeable wall and go to individual cells meaning that oxygen diffuses directly into the respiring cells
• CO2 diffuses from the cells, moving down its conc gradient, into tracheal tubes, towards spiracles and released into the atmosphere.
• Insects use rhythmic abdominal movements to move air in and out of spiracles

Question 30

When anaerobic respiration takes place, lowering the water potential of the cell what feature of the insect can increase oxygen intake and how

Answer 30

• The tracheal fluid within the tracheoles moves into the cells of the insect allowing for more intake of oxygen
• This is due to the decrease of pressure and within the tracheal system
• This also means more tracheole surface is available for the exchange of substances to occur between

Question 31

How does an insect limit water loss (and when)

Answer 31

• It closes its spiracle when there is a high concentration of oxygen in the thorax - preventing water vapor from escaping into the environment
• It has a waterproof, waxy cuticle all over their body, and tiny hairs around the spiracle - reducing evaporation

Question 32

What is the main exchange surface in dicotyledonous plants

Answer 32

The surface of mesophyll cells in the leaf

Question 33

How are mesophyll cells adapted for their function

Answer 33

They have a a large surface area which increases the rate at which the exchange of CO₂ and O₂

Question 34

What cells controls the opening and closing of the stomata

Answer 34

Guard cells

Question 35

What is the stomata (and state what it does)

Answer 35

They are special pores in the epidermis (mostly the lower epidermis) where gases move in and out of

Question 36

Why does the stomata open + why does it close

Answer 36

• It opens to allow exchange of gases to occur
• It closes if the plant is losing too much water

Question 37

What is a singular stomata

Answer 37

Stoma

Question 38

What are plants that live in conditions where water loss is a problem called

Answer 38

Xerophytes

Question 39

List and describe xerophytic adaptations

Answer 39

• Sunken stomata in pits: traps water vapour, which reduces the conc gradient of water between leaf and the air - reducing evaporation
• Layers of hair on the epidermis: trap water vapour
• Curled leaves: protects plant from the wind (wind increases rate of diffusion and evaporation
• Reduced number of stomata: leaves fewer places for water to escape
• Thick waxy, waterproof cuticles on leaves and stems: reduce evaporation