Gaseous Exchange

GASEOUS EXCHANGE IN A MAMMAL – HUMAN

GASEOUS EXCHANGE IN A MAMMAL – HUMAN
The breathing system of a mammal consists of a pair of lungs which are thin-walled elastic sacs lying in the thoracic cavity.
The thoracic cavity consists of vertebrae, sternum, ribs and intercostal muscles.
The thoracic cavity is separated from the abdominal cavity by the diaphragm.
The lungs lie within the thoracic cavity.
They are enclosed and protected by the ribs which are attached to the sternum and the thoracic vertebrae.

GASEOUS EXCHANGE IN AN AMPHIBIAN – FROG

GASEOUS EXCHANGE IN AN AMPHIBIAN – FROG
An adult frog lives on land but goes back into the water during the breeding season.
A frog uses three different respiratory surfaces.
These are the skin, buccal cavity and lungs.

GASEOUS EXCHANGE IN INSECTS

GASEOUS EXCHANGE IN INSECTS
Gaseous exchange in insects e.g., grasshopper takes place across a system of tubes penetrating into the body known as the tracheal system.
The main trachea communicate with atmosphere through tiny pores called spiracles.
Spiracles are located at the sides of body segments;
Two pairs on the thoracic segments and eight pairs on the sides of abdominal segments.
Each spiracle lies in a cavity from which the trachea arises.
Spiracles are guarded with valves that close and thus prevent excessive loss of water vapour.
A filtering apparatus i.e. hairs also traps dust and parasites which would clog the trachea if they gained entry.

GASEOUS EXCHANGE IN ANIMALS

GASEOUS EXCHANGE IN ANIMALS
All animals take in oxygen for oxidation of organic compounds to provide energy for cellular activities.
The carbon (IV) oxide produced as a by-product is harmful to cells and has to be constantly removed from the body.
Most animals have structures that are adapted for taking in oxygen and for removal of carbon (IV) oxide from the body.
These are called “respiratory organs”.

GASEOUS EXCHANGE IN LEAVES OF TERRESTRIAL PLANTS

GASEOUS EXCHANGE IN LEAVES OF TERRESTRIAL PLANTS
Gaseous exchange takes place by diffusion.
The structure of the leaf is adapted for gaseous exchange by having intercellular spaces that are filled.
These are many and large in the spongy mesophyll.
When stomata are open, carbon(IV)oxide from the atmosphere diffuses into the substomatal air chambers.
From here, it moves into the intercellular space in the spongy mesophyll layer.
The CO2 goes into solution when it comes into contact with the cell surface and diffuses into the cytoplasm.

GASEOUS EXCHANGE IN PLANTS AND ANIMALS

Necessity for Gaseous Exchange in Living Organisms

Living organisms require energy to perform cellular activities.
The energy comes from breakdown of food in respiration.
Carbon (IV) oxide is a by-product of respiration and its accumulation in cells is harmful which has to be removed.
Most organisms use oxygen for respiration which is obtained from the environment.
Photosynthetic cells of green plants use carbon (Iv) oxide as a raw material for photosynthesis and produce oxygen as a byproduct.