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multicellular heterotrophs

Locker #349, Per.1
Summary of Science Notes

We are going to go onto a magical and awesome trip into the animal kingdom. Here, we will find animals that are multicellular heterotrophs whose cells lack cell walls. There are two types of phylums for the Animalia Kingdom- vertebrates which have backbones and invertebrates that have no backbone. Within these groups, they share common ancestors. We are going to venture into the far expanses of the creatures sponges and cnidarians, one of the simplest animals.

One animal, the sponge, is the simplest and most ancient of all animals. Even though it was considered to be a plant because it didnt move, these animals are very different from them. Some ways that they are different include that they are heterotrophs, they can reproduce sexually, and they have more complex cells. It mainly lives in seawater, but some live in freshwater. The phylum porifera means pore bearers and theyre covered with pores. Its body is made up of a layer of independently functioning cells, which are located around a central cavity.

When moving water goes into the sponge through the pores, food and oxygen are provided. The cells remove food and oxygen from the water and release waste products through a larger opening called the osculum. The thing especially special about these sponges is that they have the ability to reorganize their cells. For example, if the sponge passes through a fine filter so that it breaks it into clumps of cells, these cells reform into several new sponges. Usually, their skeletons are called spicules which are thin, interlocking, spiny structures made chalky or a glasslike substance. Other sponges have a fiber like, softer material as their skeleton.

Sponges reproduce both sexually and asexually. They reproduce sexually when one sponge produces eggs while another produces sperm. In some sponges, the eggs are squirted into the surrounding water, where they may be fertilized. In other sponges, the eggs are fertilized inside the body of the parent sponge. They reproduce asexually by budding, in which part of the sponge falls off the parent and begins growing into a new one. In addition to being the source of natural sponges, sponges are also an important source for powerful antibiotics and provide homes and food for certain worms, shrimps, and starfishes.
Another animal, the cnidarians, are from the phylum Cnidaria and are also invertebrate animals, like sponges. They have tentacles and live in the water. Also, they have nematocysts which are stinging cells. Cnidarians float in the water or swim by contracting and relaxing the body, sometimes jet propulsion. There are two types of cnidarians- medusas and polyps. The medusa is mushroom-shaped and can move from place to place by floating or swimming. The tentacles hang down and the mouth is at the bottom. The polyps are vase-shaped or tube-shaped and usually stay in one place. Their tentacles stream upward and the mouth is at the top of the organism. The mouth-like opening cnidarians have is the hollow central cavity. Cnidarians are radial symmetric and they have two cell layers- the ectotherm or the outer layer and the endotherm or the inner layer. There is also a jelly-like layer between the two.

One trait that makes cnidarians unique is that their ells are organized into specialized tissues for digesting, and muscle, nerve, and sense purposes. These tissues surround the central body cavity and also the cnidarians have a mouth that opens into it. The nerve net they have is a simple network of nerve cells and it controls the movements of the body and tentacles. In order to get food, cnidarians use tentacles with special coiled stingers. When something brushes against these tentacles, the stinging cells fire a barbed spear called a nematocyst and while releasing a paralyzing toxin. Waste products are released with the mouth, which also is a passageway for the food to enter through. Cnidarians have two ways of reproducing, like the sponges- sexually and asexually. They also have the same processes of budding and producing eggs with sperm.
The animals that make up the phylum of cnidarians include corals, jellyfishes, hydras, and sea anemones. Hydras spend their life as polyps and live in fresh water. They move around in a somersaulting motion and reproduce like other cnidarians. Corals are polyps that live with each other in colonies and live in shallow water. The reason for this is because the symbiotic relationship between an autotrophic alga provides the coral with food. These soft-bodied organisms use minerals in the water to build hard protective coverings of limestone that are left behind when they die. After many generations of this process, a coral reef forms where the top layer of coral is living and the bottom layer is from thousands of years before. Sea anemones are polyps that resemble underwater flowers and their tentacles contain nematocysts that look like the petals. An example of a friendly relationship is that of a sea anemone and a clownfish. The sea anemone protects the clownfish from other fishes that might attack it while the clownfish serves as living bait and attracts the sea anemones next meal. Finally, jellyfishes are medusas for most of its life and can be found floating in the ocean. Even when its nematocysts are broken up into small pieces, they remain active.

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