1. Evolution of Organ Systems
As organisms evolved their body systems became more complex

2. Body Symmetry
Complex animals tend to have high levels of cell specialization and internal body organization, bilateral body symmetry, a front end or head with sense organs, and a body cavity.
With the exception of sponges, every kind of animal exhibits some type of body symmetry in its anatomy, or body structure.

3. Body Symmetry Asymmetry radial symmetry bilateral symmetry
no planes can be drawn through the body and create equal halves
radial symmetry
similar to that of a bicycle wheel, in which any number of imaginary planes can be drawn through the center, each dividing the body into equal halves.
bilateral symmetry
a single imaginary plane can divide the body into two equal halves.

4. Body Symmetry
Radial
Bilateral

5. Body Cavity
Most complex animal phyla have a true coelom that is lined completely with tissue derived from mesoderm.

6. Body Cavity Acoelomates Pseudocoelomates Coelomates
meaning that no coelom, or body cavity, forms between the germ layers.
Pseudocoelomates
body cavity lined partially with mesoderm (roundworms)
Coelomates  
completely with tissue derived from mesoderm.

7. Body Cavity Comparison

8. Skeletal System
Usually one of three main kinds of skeletal systems: hydrostatic skeletons, exoskeletons, or endoskeletons.

9. Skeletal System No skeleton Hydrostatic skeleton Exoskeleton
instead spicules (sponge) or some other form of support (muscles)
Hydrostatic skeleton
muscles surround a fluid-filled body cavity that supports the muscles. When the muscles contract, they push against fluid in the body cavity, causing the body to change shape.
Exoskeleton
external skeleton, is a hard body covering made of chitin.
Endoskeleton
structural support located inside the body.

10. Skeletal system
Hydrostatic skeleton
Endoskeleton

11. Respiratory System
Respiratory organs have large surface areas that are in contact with the air or water. Also, for diffusion to occur, the respiratory surfaces must be moist.

12. Respiratory System Diffusion Gills Book lungs Spiracles Lungs
respire through their skins
Gills
feathery structures that expose a large surface area to the water. Gills are rich in blood vessels that bring blood close to the surface for gas exchange.
Book lungs
parallel, sheetlike layers of thin tissues that contain blood vessels.
Spiracles
in insects, air enters the body through openings called spiracles. It then enters a network of tracheal tubes, where gases diffuse in and out of surrounding body fluids.
Lungs
Inhaling brings oxygen-rich air from outside the body through the trachea (TRAY-kee-uh) and into the lungs. The oxygen diffuses into the blood inside the lung capillaries.

13. Respiratory System
Gills
Book Lungs

14. Respiratory System
Spiracles
Lungs

15. Excretory System
Most animals have an excretory system that rids the body of metabolic wastes while controlling the amount of water in the tissues.

16. Excretory System Diffusion Nephridia Malpighian Tubes Kidneys
ammonia diffuses from their body tissues into the surrounding water.
Nephridia
annelids and mollusks, urine forms in tubelike structures called nephridia. Fluid enters the nephridia through openings called nephrostomes. Urine leaves the body through excretory pores.
Malpighian Tubes
saclike organs that convert ammonia into uric acid.
Kidneys
urea is removed from the bloodstream along with other metabolic wastes
Cloaca- frogs only one tube for solid and liquid waste
Humans- two tubes one for solid waste the other for liquid waste

17. Excretatory System
Cloaca
Malpighian Tubes

18. Most vertebrates reproduce sexually
Reproductive System
Most invertebrates reproduce sexually during at least part of their life cycle. Depending on environmental conditions, however, many invertebrates may also reproduce asexually.
Most vertebrates reproduce sexually

19. Reproductive System Asexually Sexually only need one need two Internal
eggs are fertilized inside the female's body.
External
eggs are fertilized outside the female's body

20. Circulatory System
Most complex animals move blood through their bodies using one or more hearts and either an open or closed circulatory system.

21. Circulatory System Diffusion Open system Closed system
blood is only partially contained within a system of blood vessels. Instead, one or more hearts or heartlike organs pump blood through blood vessels into a system of sinuses, or spongy cavities. The blood comes in direct contact with the tissues and eventually makes its way back to the heart.
Closed system
a heart or heartlike organ forces blood through vessels that extend throughout the body. The blood stays within these blood vessels. Materials reach body tissues by diffusing across the walls of the blood vessels.
Frog
three chamber heart
Human
four chamber heart

22. Circulatory System
Open System
Closed System

23. Circulatory System
Single and Double Loop 23

24. Human Circulatory System
How Does Blood flow?

25. Digestive System
The simplest animals break down food primarily through intracellular digestion, but more complex animals use extracellular digestion.

26. Digestive System Intracellular Extracellular
food is digested inside cells
Simple animals such as cnidarians and most flatworms ingest food and expel wastes through a single opening.
filter feeders
Extracellular
food is broken down outside the cells in a digestive cavity or tract and then absorbed into the body.
More-complex animals digest food in a tube called the digestive tract. Food enters the body through the mouth, and wastes leave through the anus.
One way track
Mouth/anus
characteristic of roundworms, mollusks, arthropods, and echinoderms
Two way track
Mouth and anus

27. Digestive System
One way track
Two way track

28. Nervous System
Invertebrates show three trends in the evolution of the nervous system: centralization, cephalization, and specialization.
Nonvertebrate chordates have a relatively simple nervous system with a mass of nerve cells that form a brain. Vertebrates have a more complex brain with distinct regions, each with a different function.

29. Nervous System Centralization Cephalization Specialization Nerve Nets
consist of individual nerve cells that form a netlike arrangement throughout the animal's body.
Cephalization
concentration of nerve tissue and organs in one end of the body
Vertebrates display a high degree of cephalization, or concentration of sense organs and nerve cells at the front of the body. The head contains a well-developed brain
The cerebrum is the “thinking” region of the brain.
Specialization
specialized sense organs that detect light, sound, chemicals, movement, and even electricity to help them discover what is happening around them.

30. Comparison and Complexity of Nervous Systems

31. Human Body Exhibit 31

32. THE END