phylum nematoda
Nematodes are among the most abundant animals on earth and inhabit virtually every environment and living thing. They can be found in soil, oceans, ice and hot springs. They occur as parasites in animals and plants or as free living creatures in soil, freshwater and marine environments.
ECOLOGICAL ROLE
Many nematodes play vital ecological roles as decomposers and predators on microorganisms. But there are also parasitic species that are harmful to humans and animals.
Many nematodes play vital ecological roles as decomposers and predators on microorganisms. But there are also parasitic species that are harmful to humans and animals.
MOVEMENT STRUCTURES/TYPE
Nematodes move by contraction and of the longitudinal muscles. They move by thrashing back and forth. No cilia or flagella are present.
Nematodes move by contraction and of the longitudinal muscles. They move by thrashing back and forth. No cilia or flagella are present.
BODY COVERING; CELL LAYERS; LEVEL OF ORGANIZATION; PROTECTION
Nematodes are unsegmented roundworms that are bilaterally symmetrical, elongated and tapered at both ends. They have three cell layers, with their cuticle secreted by and covers a layer of epidermal cells. Under the epidermal cells and near the body wall are the muscle cells that run in a longitudinal direction. They have a pseudocoelom formed directly from the cavity of the blastula. The cavity of the pseudocoel is mostly filled with an intestine and oviducts or testes.
Nematodes are unsegmented roundworms that are bilaterally symmetrical, elongated and tapered at both ends. They have three cell layers, with their cuticle secreted by and covers a layer of epidermal cells. Under the epidermal cells and near the body wall are the muscle cells that run in a longitudinal direction. They have a pseudocoelom formed directly from the cavity of the blastula. The cavity of the pseudocoel is mostly filled with an intestine and oviducts or testes.
SUPPORT; MAINTAINING BODY SHAPE
Roundworms do not have a skeletel structure or any external support. They have a strong, flexible noncellular called a cuticle, and hydrostatic pressure maintains their body shape.
Roundworms do not have a skeletel structure or any external support. They have a strong, flexible noncellular called a cuticle, and hydrostatic pressure maintains their body shape.
OBTAINING NUTRIENTS
The oral cavity is lined with cuticle and may have a number of teeth present. Their mouths often have a sharp stylet which they can thrust into its prey. The oral cavity opens up into a sucking pharynx which transfers the food into the digestive glands, that begin to produce enzymes that start to break down the food. Nematodes do not have stomachs, which is why the pharynx is connected to the intestine, which absorbs the nutrients.
The oral cavity is lined with cuticle and may have a number of teeth present. Their mouths often have a sharp stylet which they can thrust into its prey. The oral cavity opens up into a sucking pharynx which transfers the food into the digestive glands, that begin to produce enzymes that start to break down the food. Nematodes do not have stomachs, which is why the pharynx is connected to the intestine, which absorbs the nutrients.
RESPIRATION & CIRCULATION
They do not possess a respiratory system, but rely on diffusion. Diffusion is when molecules move from an area of higher concentration into an area of lower concentration. Nematodes do not have a circulatory system but its pseudocoelom (body cavity) transfers fluids, oxygen and nutrients through the process of diffusion.
They do not possess a respiratory system, but rely on diffusion. Diffusion is when molecules move from an area of higher concentration into an area of lower concentration. Nematodes do not have a circulatory system but its pseudocoelom (body cavity) transfers fluids, oxygen and nutrients through the process of diffusion.
EXCRETION
Their intestine is lined by cuticle that forms a rectum, which then expels food waste through the anus, which is located at the end of the roundworm’s tail. Nitrogenous waste is expelled in the form of ammonia through the nematodes body wall.
RESPONSE
They have a simple nervous system that consists of a ring of nervous tissue around the pharynx that gives rise to dorsal and ventral nerve cords running the length of the body. Four peripheral nerves run the length of the body on the dorsal, ventral, and lateral surfaces. The dorsal nerve is responsible for motor control, while the lateral nerves are sensory, and the ventral combines both functions. At the anterior end of the animal, the nerves branch from a dense, circular nerve (nerve ring) round surrounding the pharynx, and serving as the brain. Smaller nerves run forward from the ring to supply the sensory organs of the head. The bodies of nematodes are covered in numerous sensory bristles and papillae that together provide a sense of touch.
They have a simple nervous system that consists of a ring of nervous tissue around the pharynx that gives rise to dorsal and ventral nerve cords running the length of the body. Four peripheral nerves run the length of the body on the dorsal, ventral, and lateral surfaces. The dorsal nerve is responsible for motor control, while the lateral nerves are sensory, and the ventral combines both functions. At the anterior end of the animal, the nerves branch from a dense, circular nerve (nerve ring) round surrounding the pharynx, and serving as the brain. Smaller nerves run forward from the ring to supply the sensory organs of the head. The bodies of nematodes are covered in numerous sensory bristles and papillae that together provide a sense of touch.
REPRODUCTION
Most species have separate male and female sexes, although there are some species that are hermaphrodites. Roundworms reproduce sexually, however hermaphrodites are capable of self fertilization. Fertilization takes place when males use special copulatory spines to open the female's reproductive tracts and inject sperm into them. The eggs develop in the uterus and then hatch into larvae.