SKELETAL

SKELETAL SYSTEM: the system in which bones or shell are present in the body to create structure.

Overall importance and information of the skeletal system:

• the skeletal system is the bodies most important feature, it provides stability and structure.
• made up of calcium and proteins
• endo-skeleton, hydro-skeleton, exo-skeleton 
• protects the internal organs and reduces impact
• large sums of calcium and minerals are stored within the organisms bones
• blood formation of both red and white are formed in the marrow.
• you start off with 270 bones in your body and then in maturity you loose 64

evolutionary advantage/disadvantage:

• EARTHWORM: the skeletal structure of the earthworm is an advantage in several ways; having the luxury of a hydro static body means that the organisms movements are more fluid therefore giving it the advantage of using less energy and needing less food. another way in which this body structure is at an advantage to this animal is that it can move quickly to avoid predators or to move quickly for food. Disadvantages to having this type of body is the skin of the animal is very thin therefore making it far more susceptible to being squashed and damaged. another disadvantage is that it must always maintain a moisture friendly environment around it, if it doesn't have any water it cant move or function.
• CRAYFISH: Having an exo-skeleton (having its skeletal system act like a shield on the outside of its body) has the obvious reasons for an advantage; it is tough against predators and can effectively protect its insides from harms way. The crayfish's movements are limited because of its skeleton though causing it to have a big disadvantage. Unlike the earthworm it cannot move fluidly without a great surge of energy and power with its propulsion with water. Evolutionary the cray fish and its exo-skeleton was second in line in the evolution steps and has helped it survive past expiration date.
• GRASS FROG: The frog's endo-skeleton (containing its skeletal system within its integumentary system) gives it another layer alongside its skin to provide protection of its organs giving it an advantage in survival letting its traits get passed on to offspring in a survival of the fittest. Disadvantage to having this is that the frog can easily break bones because they are so light and fragile.
• WHITE RAT: Like the frog the rat also has a endo-skeleton also giving it the advantage of another layer of protection for its organs. the rats traits of both thick skin and dense flexible bones give it the advantage of moving quickly and bending its spinal cord to fit within small places to get away from predators or to retrieve food. Disadvantages is the movement of the rat can cause it to break its spinal cord or get injured easily because of having more bones in its body to be aware about.

Similarities and differences between animals:

EARTHWORM: 

• hydrostatic
• moves easily no bones
• segmented acts as support
• stays circular and big with water
• movement is up and down
• no back bone

CRAYFISH:

• no back bone
• no bones
• shell holds organs inside
• shell acts as bones
• stability and tough outer layer
• no nerves within shell

GRASS FROG:

• back bone
• chest plate
• hollow bones easy movement
• vulnerability to broken bones
• flexibility

  WHITE RAT:

• structure similar to human
• has backbone
• chest plate
• flexibility 
• contains marrow and calcium