Platyhelminthes- phylum consisting of acoelomate flatworms such as tapeworms, flukes, and planarians
Flatworm- simple animal with bilateral symmetry belonging to the phylum Platyhelminthes
Nematoda- phylum consisting roundworms
Roundworm- pseudocoelomate animal with a digestive system with two openings that belongs to the phylum Nematoda
Pharynx- muscular tubelike structure located at the back of the mouth that connects the mouth with the rest of the digestive tract
Flame Cells- structures that freshwater flatworms use to get rid of extra water
Ocelli- eyespots, or light sensitive organs
Scolex- the head of a tapeworm that attaches to the intestinal wall of the host
Carnivore- meat-eater
Scavenger- animal that consumes already dead organic life-forms. Scavengers are useful to the ecosystem by breaking down dead animal and plant remains
Hermaphrodite- an organism that possesses both male and female sex organs during its life
Schistosoma- A genus of trematodes, commonly known as blood-flukes
Proglottids- successive units posterior to the scolex. The sum of the proglottids is called a strobila, which is thin, resembling a strip of tape
Cyst- a closed sac having a distinct membrane and developing abnormally in a cavity or structure of the body (refer to a tapeworm’s stage of its lifecycle in a host’s muscles)
Tuesday, February 20, 2007
Feeding
Free-living flatworms may be carnivores or scavengers. They have a gastrovascular cavity with one opening at the end of a muscular tube called a pharynx that is used to suck food into the gastrovascular cavity, which forms an intestine with many branches along the entire length of the worm.
Parasitic flatworms (flukes) feed on blood, tissue fluids or pieces of cells inside the body of their host. Some of these parasites have a pharynx that pumps food into a pair of dead-end intestinal sacs where food is digested.
Tapeworms, which live within the intestines of their host, do not have any digestive tract at all. They have hooks and/or suckers with which they latch onto the intestinal wall of the host. Therefore, they can simply absorb the food passes by – food that has already been broken down by the host’s digestive enzymes.
Free-living roundworms are often carnivores that catch and eat other small animals. Some soil-dwelling and aquatic forms eat small algae, fungi, or pieces of decaying matter.
Parasitic flatworms (flukes) feed on blood, tissue fluids or pieces of cells inside the body of their host. Some of these parasites have a pharynx that pumps food into a pair of dead-end intestinal sacs where food is digested.
Tapeworms, which live within the intestines of their host, do not have any digestive tract at all. They have hooks and/or suckers with which they latch onto the intestinal wall of the host. Therefore, they can simply absorb the food passes by – food that has already been broken down by the host’s digestive enzymes.
Free-living roundworms are often carnivores that catch and eat other small animals. Some soil-dwelling and aquatic forms eat small algae, fungi, or pieces of decaying matter.
Digestion
In the intestines (blind-gut) of free- living flatworms, enzymes help break down the food into small particles. These particles are taken inside the cells of the intestinal wall where digestion is completed through. Because the intestine branches into almost all parts of the body, completely digested food can diffuse to other body tissues.
Parasitic flatworms have a simpler digestive tract than the free-living flatworms.
Tapeworms have no digestive tract at all (absorb the digested food from host).
All roundworms have a long tube-shaped digestive tract with openings at both ends. This system is efficient because food can enter through the mouth and continue straight through the digestive tract. Any material in the food that cannot be digested leaves through the anus.
Parasitic flatworms have a simpler digestive tract than the free-living flatworms.
Tapeworms have no digestive tract at all (absorb the digested food from host).
All roundworms have a long tube-shaped digestive tract with openings at both ends. This system is efficient because food can enter through the mouth and continue straight through the digestive tract. Any material in the food that cannot be digested leaves through the anus.
Excretion
Free-living flatworms expel undigested materials through the mouth as they have blind guts: only mouth, no anus. Metabolic wastes can diffuse out through their flat bodies. Freshwater flatworms such as planarians have structures called flame cells that help them get rid of extra water.
Parasitic flatworms excrete their wastes through diffusion.
Like flatworms, roundworms excrete their metabolic wastes through diffusion.
Parasitic flatworms excrete their wastes through diffusion.
Like flatworms, roundworms excrete their metabolic wastes through diffusion.
Respiration
All flatworms lack respiratory system. Because they are flat, oxygen can come in and carbon dioxide can come out through diffusion.
Roundworms breathe through their body walls.
Roundworms breathe through their body walls.
Circulation / Internal Transport
All flatworms lack any kind of specialized circulatory system. They depend on diffusion to transport nutrients to their tissues
Roundworms have no internal transport system and thus depend on diffusion to carry nutrients and wastes through their body.
Roundworms have no internal transport system and thus depend on diffusion to carry nutrients and wastes through their body.
Response to Environment
Free-living flatworms have a definite head in which a simple brain is located. This brain is the control center of a simple nervous system that stretches throughout the body. Many flatworms have one or more pairs of light-sensitive organs called ocelli, or eyespots, that detect light. Most flatworms have cells that are sensitive to chemicals found in food, and other cells that tell the worm which way the water is flowing. The nervous system helps a flatworm find food and dark hiding places.
Parasitic flatworms often do not have much of a nervous system because they are protected by their host, though the host may not want to.
The nervous system in tapeworms has completely disappeared as the worms have adapted to their parasitic lifecycle.
Roundworms have simple nervous systems. They have several ganglia in the head region, but lack a real brain. They possess several types of sense organs are simple structures that detect chemicals given off by prey or hosts. Several nerves extend from the ganglia in the head and run the length of the body. These nerves transmit sensory information and control movement.
Parasitic flatworms often do not have much of a nervous system because they are protected by their host, though the host may not want to.
The nervous system in tapeworms has completely disappeared as the worms have adapted to their parasitic lifecycle.
Roundworms have simple nervous systems. They have several ganglia in the head region, but lack a real brain. They possess several types of sense organs are simple structures that detect chemicals given off by prey or hosts. Several nerves extend from the ganglia in the head and run the length of the body. These nerves transmit sensory information and control movement.
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