Anwser to First Final Question of Biology 11 - Animal Kingdom

The five animals we dissected were: A roundworm, an earthworm, a grasshopper, a starfish, and a grass frog.

I will be discussing how each of these organisms meet the requirements for a living thing.

Roundworm:



Feeding/Digestion: Roundworms have a complete, one-way digestive system that runs from mouth to anus. They have a mouth that has 3-6 rows of teeth, which they use to feed. The food then enters the pharynx, and then, the extremely long intestine. This extends all the way to the anus, where the food is excreted.

You can see the intestine sticking out of the roundworm I dissected.

Reproduction: Male roundworms have testes, a long, thin tube, where sperm is produced. The sperm is stored in the coiled vas deferens. When reproduction occurs, the sperm cells enter the seminal vesicle. They pass out of the male tract during copulation, and a spicule holds the female's reproductive organ in place while the sperm cells go into the female. A female roundworm produces egg cells within the very thin, coiled ovary, which then enter the oviduct, and finally into the uterus. Fertilization takes place in the female, but the eggs are laid outside of her body, into soil or another environment. 

The spaghetti-looking things in the roundworm are its testes.

Nervous System: Roundworms have two nerve cords that transmit impulses to various cells and tissues of their bodies. One is called the dorsal nerve cord and the other is calle the ventral nerve cord.

Respiration/Circulation: Roundworms do not have a proper cirulatory or respiratory system. This is instead done by diffusion through the body wall.

Roundworms are more advanced than flatworms because roundworms have these complete digestive systems and nervous systems, which flatworms do not.

Earthworm:
 

Feeding/Digestion: Earthworms have long digestive tracts that run the length if their bodies from mouth to anus. They get food into their mouth because of the sucking action of the pharynx. After the food passes the esophagus it goes into the crop. It is stored here before it goes onto the gizzard, where grinding action breaks it into small pieces. Then the food goes to the long intestine.

Reproduction: An earthworm as a clitellum which is involved in its reproduction.

Respiration: Diffusion through body wall.

Circulation: Earthworms have complex, closed circulatory systems. An earthworm has a series of muscular vessels called hearts. It has a dorsal vessel and a ventral vessel for blood transport. 

Nervous System: An earthworm has a primitive brain, basically an accumulation of brain cells. It also has a ventral nerve cord, which connects the brain to other parts of the body. 

Earthworms are more advanced than roundworms because they have closed circulatory systems, and proper muscles that actually help them move.

  

Grasshopper:


Feeding/Digestion: A grasshopper has a mandible and two pairs of maxillae for feeding. 

Reproduction: Female grasshoppers have ovipositors on the last segment of the abdomen, which are specialized for the deposit of the insect's eggs.

Respiration: A grasshopper has openings along the wall of the abdomen called spiracles, which lead to tubes that make up the respiratory system of the grasshopper. 

Circulation: Grasshoppers have open circulatory systems, which means that they do not have any blood vessels for transport of blood. The blood is simply present in the body cavity. Also, it has a heart.

Nervous System: A grasshopper has a brain, nerve cord, and it had sensory organs, such as the compound eye and its antennae. 

Here you can see the antennae and compound eyes of the grasshopper I dissected.

Grasshoppers are more advanced than earthworms because a grasshopper has an outer skeleton called an exoskeleton, and their segments do not simply repeat themselves, they are specialized for things like feeding, walking, sensing, and reproducing.

Starfish:


Feeding/Digestion: A starfish has a proper digestive system consisting of a mouth on the oral surface, two stomachs, an intestine, and an anus on the aboral surface. For feeding, a starfish everts its stomach onto its prey, squirts digestive juice on it, and sucks in the partially digested food. It has digestive glands called "pyloric caeca" in its arms.

Here you can see the mouth of the starfish that I dissected.

Here you can see the digestive glands in its arm.

Reproduction: A starfish has reproductive organs calles gonads in its arms. For reproduction eggs and sperm are released into the water and external fertilization takes place. 

The brown stuff on the end of the probe is the gonad.

Respiration: A starfish has ampulla, which are bulbs on the inside of its arms, for respiration.

The orange thing on both sides of the white line has ampulla on it.

Circulation: A starfish has a closed circulatory system.

Nervous System: A starfish does not have a brain, but it has an eyespot at the end of each arm.

Grass Frog:

Feeding/Digestion: Grass frogs feed on insects. They have a digestive system consisting of a stomach, small intestine, large intestine, and anus. They are very similar to humans.

These are the organs I took out of the frog I dissected. This is the stomach.

This is the small and large intestine. The arrow on the top is pointing to the small intestine, and the arrow on the bottom is pointing to the large intestine.

Reproduction: Female grass frogs have oviducts, that look like thin string. Grass frogs can survive in water and on land, but the eggs must be laid in water, because tadpoles can only swim.

Respiration: A grass frog has lungs for respiration. 

Circulation: A grass frog has a closed circulatory system. It has a heart, and many blood vessels.

Nervous System: A grass frog has a brain, and a similar nervous system to that of a human.

A grass frog is far more advanced than all the other animals we dissected because it has lungs, which none of the other animals had. It has a small and a large intestine. It even has a spinal chord, or back bone.