Single Celled Organism

Cells and Organism Structure

Year 7

What we will learn about..

​- unicellular vs multicellular organisms

​- differentiated cells

​- organism structure

Multiple Choice

How are multicellular and unicellular organisms different?

• Unicellular organisms have one cell and are smaller than multicellular organisms.

• Multicellular organisms have one cell and are larger than unicellular organisms.

Multiple Choice

Which best explains how a single-celled organism can survive without other cells?

• They do not need to perform more than one function to survive.

• They are able to perform all necessary functions within one cell.

• They do not need any substance from outside of the cell.

Multiple Choice

Every plant and animal starts out as a single cell. This one cell divides and multiples to form a more complex multicellular organism.

• true

• false

​Unicellular vs Multicellular?

• ​Unicellular = one cell

• ​Multicellular = many cells

• ​Many unicellular organisms have a different structure than plant or animal cells

• ​They are often MUCH smaller, and sometimes do not contain a nucleus, mitochondria, or other organelles

• ​They have everything they need to survive in ONE CELL

​Multicellular Organisms

• ​All started out as one cell

• ​As you grow, your cells DIFFERENTIATE to become different types of cells to carry out all the functions of the organism

  • ​e.g. brain, skin, heart cells. These are all different, and carry out different function to keep the organism alive

​Advantages and Disadvantages:

• ​MC takes more energy to be alive and to grow

• ​UC is quick to reproduce

• ​MC are more diverse

• ​MC are more resilient (i.e. one cell can die, but the whole organism if OK)

• Can you think of anymore?

​Structure of MC Organisms

• ​Same type of specialised cell --> Tissue --> Organ --> System --> Organism

• ​Example:

  • ​Brain cells --> Brain tissue (grey matter) --> Brain --> Nervous System --> Organism

Multiple Choice

Basic unit of life

• Cell

• Tissue

• Organ

• Organ System

Multiple Choice

Multicellular Organisms

• Made of 1 cell

• Made of more than 1 cell

Multiple Choice

Based on this image is the Euglena multicellular or unicellular?

• 1. Multicellular

• 2. Unicellular

Multiple Choice

Classify the following examples (pictures) as unicellular or multicellular

• 1. Unicellular

• 2. Multicellular