Compare And Contrast Rat And Fish Disection

                                                   
 Reproductive System
Rats:

The Male reproductive system has of a pair of testis that are enclosed in scrotal sacs, then a pair of vasdefferens , a seminal vesicle, and penis. The female reproductive system consists of a pair of ovaries, a pair of fallopian tubes, a uterus, and a vagina. (or birth canal). Fertilization and development  are internal.
Fertilization takes place in the fallopian tube. The zygote undergoes an initial development and then reaches the limb (uterus). The attachment of the embryo to the uterine wall is called implantation. The entire duration of development inside the uterus, is called gestation period. After completing development, the rat is born.




Fish:
 The two main organs in fish that are involved in the reproductive process are testes and ovaries. The general reproductive method for most fish involves the release of the unfertilized eggs from the female’s body, which usually then settle on the bottom of the water. Then, the male fish is able to pass by and fertilize the eggs when they are outside of the female’s body. The eggs reach maturity after they are fertilized.

The Fish and rat both Reproduce sexually, except fertilization happens inside the rat compared to outside the fish.  


Muscular System
Rat:
  During the evolution from fish to tetrapod mammals, lots of changes happened in the muscular system.  Some of these
some changes are correlated with changes in the mode of support and locomotion that occurred with the move from an aquatic to a terrestrial environment.  Still other changes parallel changes in the mode of respiration, and the development of a moveable tongue.  Most of the axial musculature of tetrapod mammals has lost its segmentation.  The dorsal musculature moves and supports the vertebral column and head while most of the ventral musculature has differentiated into thin broad layers of muscle.  These layers support the thoracic and abdominal walls and are important in breathing movements.  Some ventral muscles of tetrapods function to transfer body weight to the pectoral girdle and appendages. 
fish:The biggest portion of the body of most fishes consists of muscles. Most of the weight is trunk musculature, the fin muscles are relatively small. The caudal fin is usually the most powerful fin, with the largest amount of direct musculature. Its musculature a structural and functional continuation of the main musculature of the body. The body musculature is usually arranged in two rows of chevron-shaped segments on each side. Contractions of these segments, each of them bend the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and causing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.


Digestive System:
Rat: The Digestive system consists of an alimentary canal and associated structures.
The buccal cavity contains teeth, which are of three different types : incisors, premolars and molars. Canines are absent. The long self sharpening chisel shaped incisors grow throughout the life of a rat.
Salivary glands in the buccal cavity, gastric glands in the stomach, intestinal glands in the small intestine, liver and pancreas situated outside the alimentary canal, are the associated structures. Liver is not only the largest gland in the body, but is also a versatile gland involved in a large number and variety of functions. Pancreas serves both as an exocrine and an endocrine gland. As an exocrine gland it produces digestive juices and as an endocrine gland it produces the hormone insulin.


Fish: They have an esophagus, and areas for the absorption of food components (fore and midgut) and compaction of indigestible waste material (hindgut). In adaptation to diet, the major differences are seen in the structure of the mouth and the teeth, the gill rakers, the pharynx, the stomach and the length of the intestine . In carnivorous diet there is a definite stomach (foregut) but  herbivorous or plant-orientated omnivores have no stomach but rely on a much extended midgut area.

Compare and Contrast ( Earthworm and Crayfish)

     Movement
                                                                               
Earthworm :
 Earthworms move with their sete                   
which are tiny feet like things that help them to move.  
the earthworm has a hydro static skeleton meaning it   
absoultly needs moisture.
Crayfish: The crayfish have an external skeleton.
To move around they use their swimmeretes and tail called the
telson to move.

Reprouduction:
Earthworm: Earthworms are hermaphrodites meaning
they are both male and female, they can mate with eachother, but not themselves.
Crayfish: crayfish reprouduce sexually, the male attaches a sperm pack on the underside of the females belly, she then curls up her tail and attaches the eggs to her swimmeretes.

Habitat:
Earthworm: they live in the soil, and are commonly found in gardens
because of the nutrients. They prouduce mucus to breath through their skin and transfer sperm.
Crayfish: Crayfish are found in fresh water, salt water, and ponds.
They hide from predators in grass and mud. They breath by extracting o2 from water using their gills
,gills provide a large surface between blood and water so o2 can diffuse from water into blood well.


Nervous System:
Earthworm:
The earthworms brain is connected to the vertral nerve cord which runs down its body, at each segment segmental ganglionnbranch from vertral nerve cord which connects every segment to the earthworm.
Crayfish: Crayfish nervous system is made up of a ganglion connected by a circumoral commissures with the post -oesophageal ganglia. these together constitute the brain. from the brain backwards streches the ganglionated cord.