Jellyfish. Pic of Jelly Fish. Classification & Evolution. Relationship to Human. Haeckel s Medusae. Taxonomy. About Terminology. Anatomy.

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3 Pic of Jelly Fish Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal. Medusa jellyfish are a life stage exhibited in some species of the phylum Cnidaria. Medusa jellyfish belong exclusively to Medusozoa, the clade of cnidarians which excludes Anthozoa (e.g., corals and anemones). This suggests that the medusa form evolved after the polyps.[32] The phylogenetics of this group are complex and still being worked out. The Medusozoa appear to be a sister group to Octocorallia.[33] Staurozoa The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp life-stage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transparent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scientists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zooplankton, when referring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not vertebrates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to Most jellyfish do not have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems. The manubrium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive.[citation needed] The body is composed of over 95% water; most of the umbrella mass is a gelatinous material the jelly called mesoglea which is surrounded by two layers of protective skin. The top layer is called the epidermis, and the inner layer is referred to as gastrodermis, which lines the gut. Most jellyfish alternate between polyp and medusa generations during their life cycle. Addi-

4 Pic of Jelly Fish Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal. Most jellyfish alternate between polyp and medusa generations during their life cycle. Additionally, there are several possible The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp lifestage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusaproducing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transparent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scientists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zooplankton, when Most jellyfish do not have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems. The manubrium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive.[citation needed] The body is composed of over 95% water; most of the umbrella mass is a gelatinous material the jelly called mesoglea which is surrounded by two layers of protective Medusa jellyfish are a life stage exhibited in some species of the phylum Cnidaria. Medusa jellyfish belong exclusively to Medusozoa, the clade of cnidarians which excludes Anthozoa (e.g., corals and anemones). This suggests that the medusa form evolved after the polyps.[32] The phylogenetics of this group are complex and still being worked out. The Medusozoa appear to be a sister group to Octocorallia.[33] Staurozoa appears to be the earliest diverging; Cubozoa and the coronate Scyphozoa form a clade that is the sister group of Hydrozoa plus discomedusan Scyphozoa. The Hydrozoa are the sister group of discomedusan Scyphozoa. Limnomedusae (Trachylina) is the sister group of hydroidolinans. This group may be the earliest diverging lineage among Hydrozoa. Semaeostomeae is a paraphyletic clade with Rhizostomeae. There are four major classes of medusozoan Cnidaria:

5 Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal. The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp life-stage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transparent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scientists include the phylum ctenophora when they are referring

6 Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp lifestage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusaproducing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, Most jellyfish do not have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems. The manubrium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navi-

7 Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp lifestage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusaproducing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, Most jellyfish do not have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems. The manubrium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navi-

8 Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal. The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp lifestage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusaproducing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transparent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scien-

9 Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal. The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp life-stage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transparent or translucent, freeswimming planktonic carnivores now known as comb jellies) were

26-3 Cnidarians Slide 1 of 47

26-3 Cnidarians Slide 1 of 47 1 of 47 What Is a Cnidarian? What is a cnidarian? 2 of 47 What Is a Cnidarian? What Is a Cnidarian? Cnidarians are soft-bodied, carnivorous animals that have stinging tentacles arranged in circles around