Organisation of Life
All living things are highly organised and this organisation occurs in levels. The simplest structures are found at the lowest levels and they interact to build up more complex structures at the next level.
Levels of Organisation of Life
There are 4 levels of organisation of life in organism. These are;
1. Cells (first level): Cell can be defined as the smallest unit of living organism. It is the first level of organisation of life. All plants and animals are made up of cells.
2. Tissues (second level): A tissue is a group of similar cells performing a layer in an organism which performs a particular function. e.g. Xylem, Epidermal, bone, muscle, etc.
3. Organs (Third level): It is a group of similar tissues forming a layer in an organism which performs specific functions. Organs in animals are; skin, brain, etc.
4. System (Fourth level): It is a group of similar organs which work together to perform specific functions e.g. skeletal, reproductive and digestive system.
5. Complexity of organism in higher organism: It involves an increase in complexity from unicellular to multicellular organism.
1. It leads to cellular differentiation
2. It leads to internal and structural specialisation.
1. Inability of individual cells to exist on their own.
2. Difficulties in acquisition of oxygen and food materials.
Tests and Exercises
1. Amoeba belongs to which organism (a) Unicellular (b) Multicellular (c) Bicellular (d) Tri cellular. Answer: Unicellular
2. The 4 levels of organisation of life are (a) Cell, Nymph, System and Organs (b) Cell, Tissue, Organ and System (c) cell, Tissue, Egg, and System. Answer: Cell, Tissue, Organ, System
3. An example of system is (a) Kidney (b) Digestive (c) Skin. Answer: Digestive
4. ………….. is a group of similar organs which work together to perform specific functions (a) System (b) Organ(c) Cell (d) None of the above. Answer: System
5. An example of an organ includes (a) kidney (b) tissue (c) Cell (d) Egg. Answer: Kidney
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