Exchange and Transport

Question 1

Smaller animals have a … SA:V ratio

Answer 1

Higher

Question 2

Larger animals have a …. SA:V ratio

Answer 2

Lower

Question 3

How to calculate SA:V ratio

Answer 3

Divide the SA by the volume

Question 4

In single celled organisms how do substances move into cells and at what speed

Answer 4

Diffusion directly into the cell across cell surface membrane, this occurs quickly due to the small distances the substances have to travel

Question 5

Why are multicellular organisms unable to use diffusion

Answer 5

• Some cells are too deep in the body
• Larger animals have a lower SA:V so is difficult to exchange enough substances to supply an organism
• They have a higher metabolic rate than single-celled organisms so use up oxygen and glucose faster

Question 6

How do multicellular organisms exchange substances

Answer 6

Using specialised exchange surfaces such as the alveoli in the lungs.

Question 7

How are root hair cells specialised to improve their efficiency

Answer 7

• They grow into long hairs which stick out giving a large SA
• And increased rate of absorption of water and mineral ions from the soil

Question 8

How are the alveoli specialised to improve their efficiency

Answer 8

• Thin walls
• Short diffusion distance
• Good blood supply = capillary network
• Moist lining
• Good ventilation so air in alveolus is constantly replaced

Question 9

How are fish gills specialised to improve their efficiency

Answer 9

• Large network of capillary’s
• Well ventilated as fresh water is constantly passing over them

Question 10

What is the passage of air in the body

Answer 10

1) As you breathe in air enters the trachea
2) The trachea splits into two bronchi - one bronchus leading to each lung
3) Each bronchus then branches off ino bronchioles
4) The bronchioles end in small ‘air sacs’ called alveoli where gases are exchanged
5) The ribcage, intercostal muscles and diaphragm all work together to move air in and out

Question 11

Function of goblet cells

Answer 11

Lines the airways and secretes mucus trapping microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli

Question 12

Function of cilia

Answer 12

On the surface of cells lining he airways and beats the mucus moving it upward away from the alveoli towards the throat, where it is swallowed preventing lung infections.

Question 13

Function of elastic fibres

Answer 13

Found in walls of trachea, bronchi, bronchioles and alveoli and help with process of breathing out. When breathing in, the lungs inflate and the elastic fibres are stretched. Then the fibres recoil to help push air out when exchanging

Question 14

Function of smooth muscle

Answer 14

In the walls of the trachea, bronchi, bronchioles allows their diameter to be controlled. During exercise the smooth muscle relaxes, making the tubes wider, so less resistance to airflow and air can move in and out of the lungs more easily.

Question 15

Function of rings of cartilage

Answer 15

In the walls of the trachea and bronchi provide support. It’s strong but flexible it stops the trachea and bronchi collapsing when you breathe in and the pressure drops.

Question 16

What happens during inspiration

Answer 16

1) External intercostal and diaphragm muscles contract
2) Causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax
3) As the volume of the thorax increases the lung pressure decreases
4) This causes air to flow into the lungs

Question 17

What happens during expiration

Answer 17

1) The external intercostal and diaphragm muscles relax
2) The ribcage moves downwards and inwards and the diaphragm becomes curved again
3) The thorax volume decreases causing air pressure to increase
4) Air is forced out of the lungs

Question 18

Define tidal volume

Answer 18

The volume of air in each breath

Question 19

Define vital capacity

Answer 19

The maximum volume of air that can be breather in or out

Question 20

Define breathing rate

Answer 20

How many breaths are taken usually in a minute

Question 21

Define oxygen consumption or oxygen uptake

Answer 21

The rate at which an organism uses up oxygen

Question 22

How does a spirometer machine work

Answer 22

1) Has an oxygen-filled chamber with a movable lid
2) The person breathes through a tube connected to the oxygen chamber
3) As the person breathes in and out, the lid of the chamber moves up and down
4) These movements can be recorded by a pen attached to the lid of the chamber this writes on a rotating drum, creating a spirometer trace. Or the spirometer can be hooked up to a motion sensor using movements to produce electronic signals, picked up by a data logger
5) Soda lime in the tube the subject breathes into absorbs carbon dioxide.

Question 23

Why does the total volume of gas in the chamber decrease over time

Answer 23

The air that’s breathed out is a mixture of oxygen ad carbon dioxide. The CO2 is absorbed by the soda lime - so there’s only oxygen in the chamber which the subject inhales from. As this oxygen gets used up by respiration, the total volume decreases.

Question 24

How do fish use a counter-current system for gas exchange

Answer 24

1) Water, containing oxygen, enters the fish through its mouth and passes out through the gills
2) Each gill is made of lots of thin branches called gill filaments or primary lamellae, which give a large SA for exchange. The gill filaments are covered in lots of tiny structures called gill plates or secondary lamellae, which increase the SA even more. Each gill is supported by a gill arch.
3) The gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion.
4) Blood flows through the gill plates in one direction and water flows over in the opposite direction called counter-current. It maintains a large concentration

Question 25

How are fish gills ventilated

Answer 25

1) The fish opens its mouth, which lowers the floor of the buccal cavity. The volume of the buccal cavity increases, decreasing the pressure inside the cavity. Water is the sucked in to the cavity.
2) When the fish closes its mouth, the floor of the buccal cavity is raised again. The volume inside the cavity decreases, the pressure increases, and water is forced out of the cavity across the gill filaments.
3) Each gill is covered by a bony flap called the operculum. The increase in pressure forces the operculum on each side of the head to open, allowing water to leave the gills.

Question 26

How to dissect fish gills

Answer 26

1) Place fish in a dissection tray or cutting board
2) Push back the operculum and use scissors to carefully remove the gills. Cut each gill arch through the bone at the top and bottom
3) Draw an label the gill

Question 27

How is the tracheae used to exchange gases in insects

Answer 27

1) Air moves into the tracheae through pores on the insect’s surface called spiracles
2) Oxygen travels down the concentration gradient towards the cells. CO2 from the cells moves down it own concentration gradient towards the spiracles to be released into the atmosphere.
3) The tracheae branch off into smaller tracheoles which have thin, permeable walls and go to individual cells. The tracheoles also contain fluid which oxygen dissolves in.
4) The oxygen the diffuses from this fluid into body cells. CO2 diffuses in the opposite direction

Question 28

What do insects use rhythmic abdominal movements to change in ventilation of insects

Answer 28

To change the volume of their bodies and move air in and out of the spiracles. When the larger insects are flying, they use wing movements to pump their thoraxes too.

Question 29

How to dissect an insects gaseous exchange system

Answer 29

1) Fix the insect to a dissecting board. You can put dissecting pins through its legs o old it in place
2) Cut and remove a piece of exoskeleton from along the length of the abdomen
3) Use syringe to fill the abdomen with saline solution. And now see a network of thin silvery-grey tubes (tracheae).
4) Then can examine the tracheae under a light microscope using a wet mount slide

Question 30

Why do insect tracheae look silvery

Answer 30

They are filled with air

Question 31

Why are walls of tracheae contain rings of chitin

Answer 31

Support