Exchange Surfaces

Question 1

Small organisms

Answer 1

Large surface area: volume ratio
Big surface area
Shorter distance from the outside of the organism to the middle of it
Simple diffusion

Question 2

Large organisms

Answer 2

Small surface area : volume ratio
Larger distance from the middle to the outside
Higher metabolic rate
Require adaptations to increase the efficiency of exchange across their surface

Question 3

What is the rate of diffusion affected by

Answer 3

Surface area eg folded membranes
Concentration gradient eg ventilation, good blood supply
Length of diffusion pathway eg alveoli is one thin layer of squamous epithelial cells

Question 4

Mammalian gas exchange system- trachea

Answer 4

• C shaped rings of cartilage for support
• ciliated epithelium (hair like structure help sweep away mucus) with goblet cells (make mucus)
• smooth muscles = muscles contract if there are harmful substances detected in the air
  Lumen of the trachea constrict and reduce airflow into the lungs
  When smooth muscles relax lumen dilates
  Stench and recoil of lumen is due to elastic fibres within tracheal wall

Question 5

Mammalian gas exchange system- bronchi and bronchioles

Answer 5

Bronchi- connect to right and left lung split into many smaller tubes to create a network of bronchioles
Both have cartilage within their walls for structural support and to keep the tubes open

Question 6

Mammalian gas exchange system- alveoli

Answer 6

Located at the end of the bronchioles and the site of gas exchange
Oxygen diffuses from the alveoli into the capillaries and carbon dioxide diffuses from the blood in the capillaries to alveoli
- large surface area= large number of alveoli provide
- short diffusion path = the alveoli walls are very thin
- maintains a steep concentration gradient = each alveolus is surrounded by a network of capillaries to quickly take away the oxygen and ventilation in the lungs is constant to quickly take away the carbon dioxide p

Question 7

What is ventilation

Answer 7

Mechanism of breathing which involves the diaphragm and antagonistic interactions between the external and internal intercostal muscles bringing about pressure changes in the thoracic cavity

Maintains a steep concentration gradient for gas exchange at the alveoli

Question 8

Inspiration- inhale

Answer 8

Results in an increased volume of the thorax and there is an increase in the air pressure within the thorax. Forces air to move out the lungs

Question 9

Expiration exhale

Answer 9

Decrease in the volume of the thorax increase in air pressure within the thorax forces air to move out the lungs.
Forced expiration- internal intercostal muscles contract
Relaxed- internal intercostal muscles relax

Question 10

What is a spirometer

Answer 10

Measures the volume of air inhaled and exhaled

Question 11

Vital capacity

Answer 11

Maximum volume of air an individual can inhale and exhale during a deep breath

Question 12

Tidal volume

Answer 12

The air inhaled (peaks) and exhaled ( troughs) when at rest

Question 13

Residual volume

Answer 13

Volume of air that always remains in the lungs so they don’t collapse

Question 14

Breathing rate

Answer 14

Number of breaths taken per minute

Question 15

Ventilation in fish

Answer 15

Swim with their mouths open so that water flows over the gills
Lower their buccal cavity- increases volume and decreases pressure which means water flows in buccal cavity
Operculum valve will shut the operculum cavity ( where the gills are located) will expand. Increases volume in operculum cavity- decrease in pressure
Then raise the floor of their buccal cavity forcing water over the gills within the operculum cavity.
Fish closes its mouth, opens the operculum ( bony flap covering the gills) - increases pressure in the operculum cavity and forces the water over the gills and out the side of the fishes head

Question 16

Gas exchange in fish

Answer 16

Exchange gases across their gills
Four layers of gills on both sides of their head - gills made of gill filaments and gill lamellae (gill plates)
- large surface area= there are many gill filaments and lamellae which are stacked at right angles to each other
- short diffusion distance = gill lamellae and filaments both thin and contain a capillary network
- maintain steep concentration gradient = countercurrent mechanism.

Question 17

Countercurrent flow mechanism

Answer 17

Water had a lower dissolved oxygen concentration compared to the concentration of oxygen in the atmosphere
For fish to maintain steepconcentration gradient- countercurrent flow mechanism is used
When water flows over the gill lamellae in the opposite direction to flow of blood capillaries
Ensures that a diffusion gradient is maintained across the entire length of the gill lamellae

Question 18

What does gas exchange in insects involve

Answer 18

Tracheal system made up of spiracles ( valve like structures that run across the abdomen) and trachea and tracheoles

Question 19

Gas exchange in insects process

Answer 19

Contract and relax abdominal muscles to move gasses on mass into and out of spiracles to the trachea
- Large surface area = many branching tracheoles
- short diffusion distance= when the cells respire, they use up oxygen and produce carbon dioxide. Abdominal muscles contract to pump air
- maintains a steep concentration gradient= when the cells respire use up oxygen and produce carbon dioxide. Abdominal muscles contact to pump air.

Question 20

Gas exchange when insects are in flight

Answer 20

Muscle cells start to respire anaerobically to produce lactate
Lowers water potential of the cells and therefore moves water from the tracheoles into the cell by osmosis. This decreases the volume of liquid in the tracheoles and causes more air from the atmosphere to move in.