GAS EXCHANGE IN ANIMALSBiology ATAR Unit 2

Chapter 11275-277

Tracheal systemSpiracles

Lungs Air sacs Alveoli

Gills Diffusion Concentration

gradient Counter-current

system

All multicellular organisms need systems for gas exchange

The type of system an organism has is dependent its size and on the environment it lives in

All systems have common characteristics that increase the efficiency of gas exchange

Keywords Making connections

GAS EXCHANGE

Gas exchange in animals is by diffusion

The 2 main gases exchanged is O2 into the body and CO2 out of the body

A high concentration of CO2 is more dangerous to organisms than a low concentration of O2

Oxygen

Carbon dioxide

GAS EXCHANGE SURFACESCharacteristics of effective exchange surfaces:

1. Large surface area to volume ratio

2. Thin & permeable3. Moist – enables the

dissolution of O2 for diffusion into the blood stream

4. High concentration gradient is maintained across the membranes

TYPES OF GAS EXCHANGE SYSTEMS

System Animal ExampleMoist skin Adult amphibians

CnidariansFrogs Jellyfish

Tracheal system

Insects Arachnids

GrasshopperRedback spider

Lungs MammalsReptiles

HumansLizards

Lungs with air sacs

Birds Chickens

Gills FishCrustaceanJuvenile amphibians

GoldfishCrabsTadpoles

MOIST SKIN

CNIDARIANS

Cnidarians are aquatic animals

Gases continually diffuse across the membranes

AMPHIBIANS (FROGS)

Tadpoles have external gills

Frogs rely on their lungs and their moist skin for gas exchange

TRACHEAL SYSTEMS Insects have holes (spiracles) which lead

into tubes (tracheas) The O2 diffuses through these from the

outside air and CO2 leaves by diffusion in the opposite direction

GILLS The amount of

dissolved O2 in water is a lot less than it is in air

Therefore, gills have a greater surface area as compared to the lungs of a similarly sized mammal

Gills are highly convoluted structures with a very high surface area.

Blood flows in the opposite direction to the water (counter-current) increasing the efficiency of gas exchange

Gills rely on water flowing over them to ensure maximum O2 uptake

Gills are the most efficient gas exchange system out of all 3 types of systems

LUNGS WITH AIR SACS

Birds have lungs with air sacs

They are inflated and deflated by the muscles of the rib cage

The air sacs force air through very fine tubes where the gas exchange takes place

LUNGS Mammals and reptiles

have lungs. The air travels:1. In through the

nostrils2. Down the trachea3. Into the alveoli of

the lungs Gas exchange takes

place in the alveoli Alveoli dramatically

increase the surface area of the lungs