Lesson 31 Survival Part 2

In our last lesson we learned that some living things are unicellular and some are multicellular.

An amoeba is a unicellular organism. This one and only cell can perform all the life functions.

The amoeba can carry out eating, digestion, locomotion, breathing and removal of waste all in one single cell.

Unicellular organisms develop functions that will help them survive and they develop structure that will support those functions.

All unicellular organisms must be small so the organism’s surface area is greater than or equal to the organism’s volume. This allows the organism to ventilate.

If a cell’s surface area is less than its volume, it will die. Cells can not be too big.

All unicellular organisms must be small. Larger organisms must be multicellular so the organism can survive.

Multicellular organisms are organisms that consist of more than one cell and have differentiated cells that perform specialized functions in the organism.

Multicellular organisms have division of labor, which means cells specialize in certain functions. Cells do not do all the functions of the body. They only do a certain function.

For example, brain cells are cells specialized for only performing functions related to the brain.

Multicellular organisms are dependent on each other for the organism to survive, but if one cell dies the organism can keep living.

P0eKVboc P0eKVboc What are multicellular organisms?

Many organisms – including humans – are multicellular.

In multicellular organisms, cells perform certain specialized functions. They create specialized structure to meet the needs of that function.

BSlMTSlg BSlMTSlg Let’s learn how multicellular organisms form.

In complex multicellular organisms, only the surface cells are in contact with the external environment. Only surface cells are able to exchange substances with external environment.

Cells within the organism are too far away from the environment for direct exchange

If an elephant did not have a transport system to bring oxygen to the cells deep on the inside of the elephant, it would die.

That is why larger organisms have transport systems to reach the needs of all cells in the body.

A ventilation system would help get the oxygen in to the elephant and a circulatory system would make sure all the cells inside the elephant receive the oxygen.

In our next lesson we will look at the circulatory system and the respiratory system in multicellular organisms.

Let’s review what we have learned about survival of unicellular and multicellular organisms. Answer the attached questions on the worksheet entitled L#31 Survival part 2.

Good Job Today! And remember to….

See you next time!