Invertebrate: Earthworm & Crayfish Compare/Contrast

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Excretory system
The system in which eliminates wastes from the body.


Worm:  The location of the excretory system is down the digestive tract.  Its structure consists of a nephridun.
Crayfish:  The excretory system of the crayfish is located at the base of the antenna; also known as the green gland.  Mainly ammonia is removed from the body of the crayfish.


Reproductive organs
An organisms organs in which contribute to sexual or asexual reproduction: eg. Egg and sperm.


Worm:  Worms are hermaphrodites, which means they contain both male and female reproductive organs.  The sperm is located in the seminal receptacle and the eggs are located in the ovaries.  When two worms come together they both act as the male and exchange sperm.

Crayfish:   Unlike the earthworm, crayfish are not hermaphrodites, and each organism is either male or female.  Their gonads are located in the dorsal of the thorax.

Skeleton and Muscles
Skeleton-The structure that holds together an invertebrate.
Muscles-The contraction of the body that results in movement.


Worm:  The skeleton of the earthworm is called a hydro static, which means it is squishy.  Their body consists of two muscles, circular and longitudinal.  As the worm contrasts, its circular muscle decreases in diameter, but at the same time it gains strength to move.  The longitudinal muscle, when contracted, shortens and widens.


Crayfish:  The skeleton of the crayfish is called an exoskeleton, which is a hard shell.  It has two kinds of muscles, extensor and flexor muscles.  Extensor muscles extend the tail, while flexor muscles bend the tail.  Both of these muscle functions able the crayfish to swim.


Habitat/Respiration
Habitat- The home of the organism.
Respiration- The way in which the organism breathes.


Worm:  The earthworm lives in places where there is moist soil and its respiration happens through its skin.
Crayfish:  A crayfishs habitat is within all freshwater environments, which means it breathes through its gills. 

A picture of the earthworm and cray fish in their natural habitat is below:

An Earthworm and Crayfish in their natural habitats:
Earthworm-In soil
Crayfish-In freshwater