The cnidaria phylum consists of more than 10,000 species, all living in an aquatic habitat. Cnidarians are made up of hydroids, jellyfish, anemones, and corals. These organisms are radially symmetrical, and come in many different shapes, sizes, and in a rainbow of beautiful colours. Cnidarians come in two different types of body forms: polyp and medusa. Some cnidarian life cycles include both a medusa stage and a polyp stage, while some include only one of these stages. There organisms play a key ecological role. For example, corals make a habitat for additional organisms. Cnidarians can grow up to be as large as 40 meters, and can weigh up to several pounds.
MOVEMENT: Polyps are sessile, meaning that they do not move, and they are normally attached to rocks. Medusae move around bodies of water by swimming freely.
BODY COVERINGS: Cnidarians have two cell layers, separated by the mesoglea or mesohyl. The outer ectoderm, or epidermis, have stinging cells, which are known as nematocysts. These stinging cells are used to fight against predators, and are the main unique characteristic of cnidarians. These organisms have the tissue level of organization, which means that their cells are organized into true tissues. Cnidarians however do not have true organs such as a heart and lungs.
SUPPORT: While polyps have the shape of a cylinder with a long stock, medusae have the shape of an umbrella with a short stalk. Cnidarians are invertebrates, and are almost completely made up of water. In order to maintain their shape, these organisms must have fluid in their cavity. This will also provide body support to these organisms.
NUTRITION: To obtain food, cnidarians rely on filter feeding. The aquatic organisms wait for water currents to bring their prey close enough to sting them with their cnidocysts. Once they kill their prey, the cnidarians use their tentacles to put their food into their mouth. In order to intake food, cnidarians rely on gastrovascular cavity, which is their primary organ. In most cases, cnidarians rely on crustaceans as their primary food source. Once the food is inside the organism, it is broken down by enzymes. Cells lining the gastrovascular cavity then absorb the nutrients.
RESPIRATION: Since cnidarians lack lungs, the rest of the cells in the cnidarians’ body are heavily relied on to receive oxygen. The cells are able to absorb oxygen and then use diffusion to exchange carbon dioxide back into the water. These organisms intake water either through their mouths or through surface cells, and then releasing it in either locations. This is possible due to a cnidarian gastrovascular cavity.
CIRCULATION: Cnidarians do not have a circulatory system since it is unneeded. Instead, these organisms fill up with water, which then moves around itself. This is similar to what happens when a water balloon gets filled up with water.
EXCRETION: In order to get rid of soluble waste, cnidarians rely on their gastrovascular cavity. These organisms release their waste in the same location they intake it. This means that the location they intake food serves as both a mouth and an anus to cnidarians.
RESPONSE: Cnidarians have a central nervous system, and within this are nerve nets. The sensory neurons within the nerve net help these organisms sense things such as preadators and prey.
REPRODUCTION: Polyps reproduce asexually, while medusae reproduce sexually. Polyps reproduce by budding, which is when the new organism grows on its parent, and detaches once it is fully developed. Medusae have the ability to produce either eggs or sperm. Once the eggs are fertilized, it will develop into a swimming larva, and once mature, it will settle and grow into a polyp.
MOVEMENT: Polyps are sessile, meaning that they do not move, and they are normally attached to rocks. Medusae move around bodies of water by swimming freely.
BODY COVERINGS: Cnidarians have two cell layers, separated by the mesoglea or mesohyl. The outer ectoderm, or epidermis, have stinging cells, which are known as nematocysts. These stinging cells are used to fight against predators, and are the main unique characteristic of cnidarians. These organisms have the tissue level of organization, which means that their cells are organized into true tissues. Cnidarians however do not have true organs such as a heart and lungs.
SUPPORT: While polyps have the shape of a cylinder with a long stock, medusae have the shape of an umbrella with a short stalk. Cnidarians are invertebrates, and are almost completely made up of water. In order to maintain their shape, these organisms must have fluid in their cavity. This will also provide body support to these organisms.
NUTRITION: To obtain food, cnidarians rely on filter feeding. The aquatic organisms wait for water currents to bring their prey close enough to sting them with their cnidocysts. Once they kill their prey, the cnidarians use their tentacles to put their food into their mouth. In order to intake food, cnidarians rely on gastrovascular cavity, which is their primary organ. In most cases, cnidarians rely on crustaceans as their primary food source. Once the food is inside the organism, it is broken down by enzymes. Cells lining the gastrovascular cavity then absorb the nutrients.
RESPIRATION: Since cnidarians lack lungs, the rest of the cells in the cnidarians’ body are heavily relied on to receive oxygen. The cells are able to absorb oxygen and then use diffusion to exchange carbon dioxide back into the water. These organisms intake water either through their mouths or through surface cells, and then releasing it in either locations. This is possible due to a cnidarian gastrovascular cavity.
CIRCULATION: Cnidarians do not have a circulatory system since it is unneeded. Instead, these organisms fill up with water, which then moves around itself. This is similar to what happens when a water balloon gets filled up with water.
EXCRETION: In order to get rid of soluble waste, cnidarians rely on their gastrovascular cavity. These organisms release their waste in the same location they intake it. This means that the location they intake food serves as both a mouth and an anus to cnidarians.
RESPONSE: Cnidarians have a central nervous system, and within this are nerve nets. The sensory neurons within the nerve net help these organisms sense things such as preadators and prey.
REPRODUCTION: Polyps reproduce asexually, while medusae reproduce sexually. Polyps reproduce by budding, which is when the new organism grows on its parent, and detaches once it is fully developed. Medusae have the ability to produce either eggs or sperm. Once the eggs are fertilized, it will develop into a swimming larva, and once mature, it will settle and grow into a polyp.