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mammal, fish, insect

Animal Group 1: Mammal
Brief Description of type of system

Terrestrial vertebrates, i.e mammals use internal lungs, which are a pair of breathing organs located in the chest and are the site in which gaseous exchange occurs.

Animal Group 1: Mammal
How the system works in this group:
What organs/structures are involved and how do they work?

Water diffuses from the alveoli cells into the alveoli so that they are constantly moist. Oxygen dissolves in this water before diffusing through the cells into the blood, where it is taken up by haemoglobin in the red blood cells. The water also contains a soapy surfactant which reduces its surface tension and stops the alveoli collapsing. The alveoli also contain phagocyte cells to kill any bacteria that have not been trapped by the mucus.

Animal Group 1: Mammal
Adaptations for the environment

the vicinity in which gas exchange takes place
microscopic air sacs which form clusters, like tiny bunches of grapes.
Each lung contains approximately 150 million- total surface area in an adult human= 70m². this is more necessary for gas exchange in mammals to occur because since they are larger than fish or insects, and they use more energy, more oxygen is needed to sustain them.
Surfaces are covered in network of fine blood capillaries.

Animal Group 2: Fish
Brief Description of type of system

Fish make use of a paired respiratory organ called gills, which are used to extract oxygen from water flowing over surfaces within the walls of the pharynx.

Animal Group 2: Fish
How the system works in this group:
What organs/structures are involved and how do they work?

Fish make use of gills in order to complete gas exchange. The gills are on the outside of their body. They lie free in the water, and are made up of many thin filaments. These filaments are further divided into thin foldings called lamellae, which greatly increases the surface area for gas exchange. This is because water contains much less oxygen than air. To further enhance gas exchange fish gulp in water, and then, by closing their mouth, force the water to exit over the gills.

Animal Group 2: Fish
Adaptations for the environment

Fish have gill filaments which are made of many parallel lamellae, each folded to increase surface area.
each filament is composed of delicate plates containing many capillaries, so they look dark red

Gas exchange

gaseous exchange is the movement of gases across a membrane. all things carry out respiration- the release of energy from food. they take in oxygen and give out carbon dioxide. oxygen has to be recieved across a membrane and carried to the cells. in the cells, mitochondria take it in, release energy, and give out carbon dioxide. this is then carried to the surface where it can be eliminated.

respiratory surface must be:

>moist- gases have to be dissolved in water in order to pass across a membrane.
>large enough- for the requirements of the animal (this leads to complicated folding or branching of the surface)
>thin enough- for the gases to diffuse across. this also supposes that surfaces are delicate and easily broken, so have to be protected. in the larger land animals they are internal, to prevent water loss and for protection

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