The document discusses why multicellular organisms require organ systems. It explains that single-celled organisms can carry out all life processes within a single cell by directly exchanging substances with the external environment. However, the cells of multicellular organisms are not all in direct contact with the environment and cannot independently obtain nutrients, oxygen, or remove wastes. Therefore, multicellular organisms have developed organ systems that work together to provide nutrients, oxygen, remove wastes, and perform other necessary functions for the organism. The main human organ systems listed are the digestive, circulatory, respiratory, excretory, reproductive, nervous, muscular and skeletal systems.

1. FUNCTIONING ORGANISMS.
01. Body systems.
Ian Anderson
Saint Ignatius College Geelong

2. MULTICELLULAR ORGANISMS.
Why do complex multicellular organisms like humans
need organ systems?
Source: http://www.bodymotsystems.com/

3. SINGLE-CELLED ORGANISMS.
 Single-celled organisms
can carry out all their life
processes within the one
cell.
 Organisms are able to
exchange substances
directly with their external
environment.
 Nutrients & oxygen can
be collected from the
surrounding water.
 Wastes can be got rid of
directly into the water.
Source: http://www.microscopy-uk.org.uk/mag/art97b/prointro.html

4. MULTICELLULAR ORGANISMS.
 The cells of multicellular
organisms are not all in
direct contact with their
external environment.
 Not all body cells are
able to exchange
substances with the
external environment.
 They are therefore unable
to obtain their own
nutrients, oxygen & other
substances needed for life
processes, nor get rid of
wastes.
Source: http://www.wrecksite.eu/marine-
species.aspx

5. MULTICELLULAR ORGANISMS.
 In order to obtain
nutrients, oxygen & other
substances and be able
to get rid of wastes the
cells of multicellular
organisms need a
helping hand.
 They need organ
systems which together
work to provide nutrients,
oxygen, get rid of waste
and lots more.
Source: http://cartoons-
picture.blogspot.com.au/2012/12/cartoon-coyote-pictures.html

6. LEVELS OF ORGANISATION.
Cells • form
Tissues • form
Organs • form
Organ
systems
• form
Organism
Source: http://encyclopedia.lubopitko-bg.com/

7. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
Source: http://www.cakechooser.com/

8. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
 Circulatory system.
Source: http://www.cakechooser.com/

9. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
 Circulatory system.
 Respiratory system.
Source: http://www.cakechooser.com/

10. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
 Circulatory system.
 Respiratory system.
 Excretory system.
Source: http://www.cakechooser.com/

11. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
 Circulatory system.
 Respiratory system.
 Excretory system.
 Reproductive system.
Source: http://www.cakechooser.com/

12. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
 Circulatory system.
 Respiratory system.
 Excretory system.
 Reproductive system.
 Nervous system.
Source: http://www.cakechooser.com/

13. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
 Circulatory system.
 Respiratory system.
 Excretory system.
 Reproductive system.
 Nervous system.
 Muscular system.
Source: http://www.cakechooser.com/

14. ORGAN SYSTEMS.
What are our main organ
systems?
 Digestive system.
 Circulatory system.
 Respiratory system.
 Excretory system.
 Reproductive system.
 Nervous system.
 Muscular system.
 Skeletal system.
Source: http://www.cakechooser.com/

15. BIBLIOGRAPHY.
Cash, S., Quinton, G., Tilley, C., & Craven, E. (2013).
Oxford Big Ideas. Science 8: Australian
Curriculum. Melbourne: Oxford University Press.

16. http://sickscience8.wikispaces.com/