Multicellular Organization

Why go multicellular?



A9.2 The pygmy marmoset is one of the smallest animals on Earth.
In the previous lesson, you learned cells need to find the ideal balance between surface area and volume. They need to be large enough to house all their organelles and perform the functions of life but small enough that they can transport materials into and out of the cell efficiently. When a cell gets too large, it divides into two cells to stay within this ideal ratio.

Multicellular organisms have come up with a way around this limitation. Instead of staying as one cell, they are a grouping of millions of cells that work together. This way they can create systems to transport materials around the organism and do not have to rely on the cell membrane. Most cells within the multicellular organism still find this ideal ratio, but the organism as a whole does not have to.

Multicellular organisms have many advantages over single-celled organisms:

  • They can grow larger than the surface area to volume ratio allows a single cell to.
  • They can live in a broader range of environments.
  • They can specialize their cells so each cell has a specific job that benefits the entire organism.

A9.3 The blue whale is the largest animal on Earth.


Some advantages of being multicellular can become disadvantages depending on the situation. For example, if a few cells do not function properly or become diseased, the multicellular organism still has many healthy cells to perform their tasks. However, if dysfunction spreads to too many cells, such as a group of cancerous cells, the whole organism could suffer. In a single-celled organism, each cell must perform all the life functions, but it relies on itself, and not other cells, to survive.

To combat some of these disadvantages, there must be some type of organization in multicellular organisms. Just like in a company, the cells must each have a specific job and certain cells must work together to complete their function.

  • Cells that have similar functions create tissues.
  • Tissues that have similar functions create organs.
  • Organs that have similar functions create systems.
  • Systems perform the life functions of the multicellular organism.

A9.4 Multicellular organization

  Read This

Please read pages 296 and 297 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the reasons why an organism becomes multicellular and the two systems in a plant. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions

Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. Draw a flow chart that shows how cells are organized into systems in a multicellular organism.


A9.5 Flowchart showing multicellular organization


  1. Name two advantages and two disadvantages to being a multicellular organism.
Advantages:
  • They can grow larger than the surface area to volume ratio allows a single cell to.
  • They can live in a broader range of environments.
  • They can specialize their cells so each cell has a specific job that benefits the entire organism.
Disadvantages:
  • The organism must rely on each cell to do its job properly.
  • One cell could cause the whole organism to suffer.