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SAI International School
Subject- Biology, Class-VII
Topic- Transportation and Excretion
Subtopic- Transportation of substances in organisms
Module- 17
Lesson notes
Transportation in Organisms
Transportation in Unicellular Organisms: In unicellular organisms, such as, Amoeba
and Paramecium, transportation of substances happens through diffusion and osmosis.
Gases move in and out of the cell by diffusion. Other substances move by osmosis. No
specialised transportation system is present in such organisms.
Diffusion - movement of solutes/gas molecules from higher concentration region to lower
concentration region.
Transportation in Multicellular Organisms: In complex animals, there is a special
transport system to carry oxygen, carbon dioxide, nutrients, waste products, food and
various other substances from one part of the body to the other. This transport system
is called the circulatory system.
