Cells and Tissues - Definition, Difference
Think about the different organisms we have read about.
Now let us list a few;
- Amoeba
- Rose plant
- Cockroach
- Crow
- Dog
- Mango tree
- Elephant
- Human being
What is common between all these organisms?
They are all living
And what is a common factor in all living organisms?
They are composed of cells .
In organisms like Amoeba, Paramoecium , Euglena etc. a single cell is responsible for all the life supporting processes like respiration, digestion, movement, excretion etc.
They are single celled or unicellular organisms .
On the other hand, organisms like animals, plants and human beings are made of multiple cells and are multicellular organisms .
Millions of cells work are responsible for the life supporting processes in multicellular organisms
They are grouped to perform specialised functions
For example:
In animals -
- Muscle cells contract and relax to cause movement
- Nerve cells carry messages
- Blood flows to transport oxygen, food, hormones and waste material
In plants-
- Vascular tissues conduct food and water from one part of the plant to other parts
Cells that are responsible for a particular function are grouped together.
A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue .
Example - Blood, Phloem, Muscles
This means, there is division of labour in multicellular organisms, as a group of cells called tissues are specialised for different activities .
So the levels of organisation in organisms are:
