What is another word for ‘back of’ the animal?
What is another word for ‘front of’ the animal?

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The prefix “platy” in platyhelminthes means flat or
“ platelike ”.
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Flatworms are known as being unsegmented , meaning that their bodies are not segmented into parts.

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Flatworms exhibit bilateral symmetry .
With cephalization , flatworms have a definite anterior end to the body that has a concentration of sensory structures and nerve tissue.

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They have a one-way digestive system with two openings : a mouth and an anus.
– The two opening digestive system is more efficient in that material only moves one way.

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Disgusting!! Don’t look at the pictures online…
Make sure you cook your meat.

Dangerous
Roundworms
As an example, hookworm larvae in soil may bore into human feet, enter the bloodstream, and travel to the intestine, where they cause the disease
Trichinosis in humans.

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Compared with other worms, segmented worms have more complex digestive and circulatory systems and a more highly developed nervous system.

• there are gradual modifications to these segments that reflect the degree of specialization in their function

Annelid worms have much greater mass and size over the nematodes and flatworms.

An advance in evolution of the body plan first seen in annelid worms is the development of a coelom by the endoderm layer of cells that separates the body wall from the digestive tract.

The breath through the skin…

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used in medieval times in
Europe for certain illnesses anti-clotting chemical they secrete into a wound helps to stop a scab from forming, preventing the skim from sealing over too quickly. prevents the formation of a scar and promotes healing from the inside of the body outwards.

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• used in the treatment of heart disease. used in plastic reconstructive skin surgery.
There is a company in the U.K. that breeds leeches and sends them around the world to doctors for the use with patients.

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Flatworms are bilaterally symmetrical and have well-developed sensory structures and a collection of nerve cells in the anterior end that act as a control centre, a development known as cephalization.
Annelid worms have much greater mass and size over the nematodes and flatworms.
Because of this, gas exchange must be carried out by diffusion assisted by the circulatory system, unlike simple diffusion in nematodes and flatworms. Most annelids lack a rigid, external protective covering. The thin body wall serves as a surface for gas exchange, but this thin body surface restricts the animals to moist environments. Having a thin outer covering allows for the rapid loss of body fluids in dry air.
Roundworms show a major advance in evolution over the flatworms in that they possess a separate mouth and anus. This arrangement in the body plan is characteristic of nearly all complex animals and allows for an efficient, one-way passage of food through the digestive system.

4. The body plan of parasitic organisms is usually very simple. They usually lack organ systems to carry out digestion, circulation, and gas exchange. As parasites, the host pre-digests the food, which is then taken into the organism with a minimum of further breakdown. They usually have a thick cuticle produced by an epidermis that is formed by the ectoderm layer of cells in order to prevent being digested themselves by their host.
5. An advance in evolution of the body plan first seen in annelid worms is the development of a coelom by the endoderm layer of cells that separates the body wall from the digestive tract.
This fluid-filled cavity serves as a protective shield between the delicate internal organs and the outside environment, allowing activity, such as burrowing through soul. A body cavity segmented into compartments also allows an animal to alter its body in various ways to better control its movements.

6. Cephalization is thought to provide a selected advantage to animals that move because the anterior end typically encounters obstacles in its environment first. Since bilaterally symmetrical species include the development of a central control centre with sensory structures that are located near the mouth, they respond more quickly to environmental situations that possibly put them at risk.
7. Tapeworms lack both a mouth and a digestive sac compared to other flatworms. This is because tapeworms live in the digestive system of their host animal and absorb food directly through their body wall.
8. Annelid worms have much greater mass and size over the nematodes and the flatworms.
Because of this, gas exchange must be carried out by diffusion in nematodes and flatworms.
Most annelids lack a rigid, external protective covering. The thin body wall serves as a surface for gas exchange, but this thin body surface restricts the animals to moist environments. Having a thin outer covering allows for the rapid loss of body fluids in dry air.

9. Because earthworms exchange gases through a moist cuticle, after heavy rainfall many worms rise to the surface of their burrows to increase their exposure to air.
10. Division of the body into a series of repeating segments that contain identical copies of internal structures gives the animal an opportunity to increase in body size without a great problem of communicating one segment to another. Segmentation in the body plan is also an advantage over that of roundworms for locomotion since the body compartments, each controlled by different muscles, are capable of far greater complexity of movement over nonsegmented worms.
11. The flatworm Planaria is bilaterally symmetrical with few internal organs. Because it lacks the organs for transporting oxygen to internal tissues and only a few organs for excreting liquid wastes, all cells of the animal need to be near the surface. Because of this, the body plan is flattened and this animal is often called a flatworm. This flattened shape prevents the presence of a fluid-filled coelom. The digestive tract if a flatworm has a mouth opening into a dead-end sac. However, the digestive sac or gastrovascular cavity is often highly branched so as to increase the surface area for absorption of digested nutrients.

12. Although most roundworms are harmless, there are important exceptions. As an example, hookworm larvae in soil may bore into human feet, enter the bloodstream, and travel to the intestine, where they cause the disease Trichinosis in humans.

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• http://www.youtube.com/watch?v=mO44qj7evA4 http://www.youtube.com/watch?v=ckP8msIgMYE http://www.youtube.com/watch?v=cePKpt5nOJ0 http://www.youtube.com/watch?v=D3W4OCnHyCs http://www.youtube.com/watch?v=qxbuysNGLOM&feature=fvst

Phylum Mollusca

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mostly marine organisms, living along seashores or in shallow waters

Many snails and some clams inhabit freshwater, but others, including slugs, are terrestrial .

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They are all based on a body plan with three main components: the foot , the mantle, and a fleshy visceral mass that includes a rasping feeding structure that originally was the organ for locomotion.
In squids and octopuses , the foot is modified to form arms and tentacles on a head with complex sense organs.

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In other groups, such as clams , the foot was altered into a burrowing organ.

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The mantle is a strong membrane that covers the soft body and internal gills. A hardened shell is often secreted by the mantle for protection.

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Like sponges, most bivalves are sessile .
Bivalves capture food from the water using their large gills , which are also the organs of gas exchange.

Bivalves

oyster scallop clam

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Features Common to all Echinoderms radially symmetrical
The body plan of adult echinoderms is based on five equal parts radiating out from a central axis.
Sea Cucumber [www.keepvid.com].mp4
Sea Cucumber_s natural defenses.mp4
http://www.youtube.com/watch?v=aCxKFc3XtJs&NR=1

• do not demonstrate cephalization

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Almost all echinoderms have an endoskeleton
(meaning inside skeleton) that provides supports and protection to the animal.
The endoskeleton consists of calcium plates that extend within the body wall. Spiny projections connect to the plates and stick out through the skin.

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Mollusks (meaning soft bodied) are believed to have arisen from an annelid-like ancestor and have a moist, muscular body without a skeleton.
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Almost all echinoderms have an endoskeleton that supports and protects the animal.

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This Purple sea urchin from California has hundreds of pointy spines for protection.

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The Orange-footed sea cucumber lives in the North
Atlantic. It resembles a football with tentacles at one end for feeding.

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This sea cucumber is eviscerating a portion of its intestines to thwart an attack.

squid water is forced out of the mantle cavity through a funnel-shaped siphon – jet propulsion octopus

cuttlefish
Nautiluses
Only the nautilus retains an external shell

The giant squid can attain a length of over 60 feet.