Adaptations of gas exchange in animals

Question 1

How does gas exchange work in different size organisms

Answer 1

• how much oxygen needed depends on an organisms volume
• the rate that oxygen is absorbed depends on the surface area available for gas exchange
• as organism increase in size their surface area to volume ratio decreases so specialised respiratory surfaces are needed

Question 2

What does the surface area to volume ration of an organisms affect

Answer 2

• the surface adapted for use for gas exchange
• the level of activity of the organism

Question 3

Describe gas exchange in insects

Answer 3

• insects cannot use their external surface for gas exchange as they are covered in an impermeable cuticle to reduce water loss by evaporation
• pairs of spiracles on segments of the thorax and absdomen
• these holes lead to tubes called tracheae leading to traecheoles
• tracheoles enter muscle cells directly they have fluid at the end for dissolving and diffusion of oyxgen
• during flight when oxygen requirements increase fluid in tracheoles decreases to shorten diffusion path and whole body contractions ventilate the tracheal system by speeding up air flow through spiracles

Question 4

Why do fish require a gas exchange surface

Answer 4

• they have a smaller surface area to volume ratio
• there are relativley active so have high metabolic rates making oxygen requirements high
• require a ventilation mechanisms to maintain concentration gradients for gas exchange

Question 5

How does ventilation occur in fish

Answer 5

• mouth opens and floor of buccal cavity lowers so volume increases pressure decreases and water rushes in
• mouth closes floor of buccal cavity raises increasing pressure pushing water over the gills
• pressure in gill cavity increases and water forces operculum open and leaves through it

Question 6

Why do fish equire a ventilation mechanism

Answer 6

• fish require a ventilation mechanism to puh water a dense medium with lowoxygen content over high surface area gill filaments
• removal from water causes these gill filaments to collapse stick together and the gas exchange surface becomes too small for survival

Question 7

What are gills made up of

Answer 7

• the gills have gill filaments made of gill lamellae (gas exchange surface across whcih water flows)
• gill rakers prevent large particulates entering and blocking the gills

Question 8

What do gas exchanges surfaces must have

Answer 8

• be moist in terrestrial animals
• be thin (short diffusion pathway)
• have a large surface area
• be permaeble to gases
• have a good supply to maintain concentration gradeints (larger organims only)

Question 9

What is parallell flow

Answer 9

• water and blood flow in same direction
• equilibrium is reached
• oxygen diffusion reaches no net movement halfway across the gill plate

Question 10

What is counter current flow

Answer 10

• water and blood flow in opposite directions across the fill plate
• concentration gradient is maintaines and oxygen diffuses into the blood
• across entire gill plate

Question 11

How are amoebas adapted for gas exchange

Answer 11

• single cell
• large surface area to volume ration
• rate of oxygen diffusion through external surface meets demand
• a low metabolic rate means oxygen demand is low
• there is a short diffussion distance to the middle of the cell

Question 12

Describe the adaptations for gas excahnge in flatworms

Answer 12

• multicellular
• smaller surface area to volume ration
• flattened body to reduce diffusion distance so rate of oxygen diffusion through body surface meets demand

Question 13

How are earthworms adapted for gas exchange

Answer 13

• multicellular
• even smaller surface area to volume ratio
• body surface still used for gas exchange but circulatory system needed to distribute oxygen
• blood vessels are close to skin surface and blood has haemoglobin with high addinity for oxygen
• mucus secreted to moisten surface and slow moving to reduce oxygen demand

Question 14

Describe inpiration in humans

Answer 14

• external intercostal mucles contract and pull the rib cage up and out
• outer pleural membrane is pulled out this reduces pressure in pleural cavity and inner pleural membrane is pulled outwards
• this pulls on surface of the lungs cause an increase in the volume of the alveoli
• alveolar pressure decreases below atmospheric pressure and air is drawin into the lungs

Question 15

Describe has exchange in amphibia

Answer 15

• have aquatic tadpoles that have feathey gillss
• they don’t ventilate like fish but movement of gills through water maintains a concentration gradient
• tadpoles devlop in adults ampibia live on land and in water but return to water to mate and lay eggs
• amphibia have soft, moist skin and exchange gases over their surface at rest
• oxygen and carbon dioxide circulate through a closed circulation system containing haemofglobin
• when active movements of buccal cavity ventilate lungs which are simple with few alveoli