Lesson 31Survival 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 organismsare 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.

https://www.youtube.com/watch?v=N8oP0eKVboc

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.

https://www.youtube.com/watch?v=IRbBSlMTSlg

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!