C7- Exchange surfaces and Breathing

Question 1

2 reasons why simple diffusion alone is enough to supply the needs of a single celled organism

Answer 1

The metabolic activity of a single celled organism is usually low, so oxygen demands and CO2 production of the cell are usually low

The surface area to volume ratio of the organism is large

Question 2

4 common features of specialised exchange surfaces

Answer 2

Increased surface area

Thin layers

Good blood supply

Ventilation to maintain diffusion gradient

Question 3

Why do specialised exchange surfaces have an increased surface area?

Answer 3

Provides area needed for exchanges

Overcome limitations provided by lowered SA:V in larger organisms

Question 4

Why do specialised exchange surfaces have thin layers

Answer 4

Shortens the diffusion pathway

This makes the process fast and efficient

Question 5

Why do specialised exchanged surfaces have a good blood supply and ventialtion

Answer 5

Maintains concentration gradient for diffusion

Makes the process of exchange more efficient

Question 6

Adaptations of the nasal cavity

Answer 6

Moist – reduces evaporation from
exchange surfaces

Good blood supply – warms the air

Hairs – traps bacteria and dust

Mucus – traps bacteria and dust

Question 7

Adaptations of the trachea

Answer 7

Carries warm moist air
- Greater kinetic energy of particles in air then increases rate of diffusion

C-shaped rings of cartilage
– prevents collapse

Lined with:
Ciliated epithelial cells
Goblet cells

Question 8

Adaptations of Bronchus

Answer 8

Rings of cartilage in the walls of the bronchi provide support

It is strong but flexible

It stops the trachea and bronchi collapsing when pressure drops

Question 9

Adaptations of bronchioles

Answer 9

Small (1mm)

No cartilage

Thin layer of epithelial cells – some
gaseous exchange

Walls contain smooth muscle so can
constrict and dilate

Question 10

Adaptations of alveoli

Answer 10

Good ventilation- Oxygen and carbon dioxide are moved efficiently into and out of the alveoli so that concentration gradients are maintained

Thin layers –single cell thick Less distance for oxygen to diffuse across

Large surface area- Greater efficiency of diffusion

Good blood supply –Takes oxygen away quickly so maintains a high concentration gradient

Question 11

Ventilation

definition

Answer 11

Breathing

where air is constantly moving in and out of the lungs

Question 12

Inspiration

Answer 12

Inhalation

occurs when air pressure in the atmosphere is greater than that of the lungs

forcing air into the alveoli

Question 13

Expiration

Answer 13

exhalation

occurs when air pressure in the lungs is greater than the air pressure in the atmosphere

Forcing air out of the alveoli

Question 14

2 sets of muscles involved in ventialltion

Answer 14

Diaphragm

Intercostal muscles

Question 15

2 types of intercostal muscles

effects of contraction

Answer 15

internal = contraction leads to expiration

external= contraction leads to inspiration

Question 16

antagonistic pair of muscles

definition

Answer 16

One muscle of the pair contracts to move the body part, the other muscle in the pair then contracts to return the body part back to the original position

Question 17

Boyles law

Answer 17

P1V1= P2V2

Decreasing volume increases collisions, increasing pressure

Question 18

Inspiration process

Answer 18

External intercostal muscles contract, internal relax

diaphragm contracts

Air pressure in thorax decreases

lung volume increases

air moves in

Question 19

Expiration process

Answer 19

Internal intercostal muscles contract, external relax

Diaphragm relaxes

Air pressure in thorax increases

Lung volume decreases

Air moves out

Question 20

Adaptation of gills

Answer 20

Large surface area

Gill filaments overlap – so resist water
flow (slows water down for more
efficient oxygen uptake)

Counter-current exchange – allows 80%
of oxygen to be taken up (cartilaginous
fish have a parallel system which only
allows 50% uptake)

Question 21

Fish gills

Operculum

Answer 21

Skin flap over the gills

Protects gills

Directs flow of water

Question 22

Fish Gills

Counter current system

Answer 22

Water flows against the direction of blood

Means there is always a concentration gradient

Blood can be more oxygenated at the gills than parallel system

The water with the lowest oxygen concentration is found adjacent to the most deoxygenated blood

Question 23

Why will fish die if left for a long time out of the water

Answer 23

In air gill filaments all stick together

SA for gas exchange is greatly reduced and so fish dies from lack of oxygen

Question 24

Structure of gills in fish

Answer 24

Series of gills on each side of the head

Each gill arch is attached to two stacks of filaments

On the surface of each filament, there are rows of lamellae

The lamellae surface consists of a single layer of flattened cells that cover a vast network of capillaries

Question 25

Ventilation mechanism in fish

Inspiration of water

Answer 25

The ventilation mechanism in fish constantly pushes water over the surface of the gills and ensures they are constantly supplied with water rich in oxygen (maintaining the concentration gradient)

When the fish open their mouth they lower the floor of the buccal cavity. This causes the volume inside the buccal cavity to increase, which causes a decrease in pressure within the cavity

The pressure is higher outside the mouth of the fish and so water flows into the buccal cavity

Question 26

Ventilation mechanism in fish

expiration of water

Answer 26

The fish then raises the floor of the buccal cavity to close its mouth, increasing the pressure within the buccal cavity

Water flows from the buccal cavity (high pressure) into the gill cavity (low pressure)

As water enters pressure begins to build up in the gill cavity and causes the operculum (a flap of tissue covering the gills) to be forced open and water to exit the fish

The operculum is pulled shut when the floor of the buccal cavity is lowered at the start of the next cycle

Question 27

Function of gill rakers in fish

Answer 27

By preventing food particles from exiting the spaces between the gill arches, they enable the retention of food particles in filter feeders