An Introduction to Invertebrates

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Invertebrates
Invertebrates are the largest group of animals. They have no backbone or internal skeleton. Without the support and protection of bones, many invertebrates are smaller in size than vertebrates, although many large invertebrates can be found in the ocean.

Many invertebrates have soft, flexible bodies with a tough outer covering for protection and to reduce water loss. Most invertebrates reproduce sexually with the young hatching from eggs. The young often look very different from their parents. Some invertebrates, particularly arthropods, undergo changes in body form as they grow – a process called metamorphosis.

Aquatic invertebrates in the ocean can reach sizes much larger than invertebrates on land as the water they live in helps to support their bodies.

Sponges are some of the world’s oldest and simplest animals. They are multicellular organisms, but do not have body parts, tissues or organs. Their asymmetrical bodies consist of one or more tubes with an opening at the top. An asymmetrical body does not have any lines of symmetry. Most sponges live in the ocean, but some live in fresh water environments.

Cnidarians are animals that live in aquatic environments. Most can be found in the ocean, but some also live in fresh water. Jellyfish are cnidarians with soft jelly-like bodies. They spend the early stages of their life cycle attached to the sea floor and are free-swimming as adults. Jellyfish have tentacles that are used to catch prey.

Worm is the general name given to animals from three different groups – flatworms, roundworms and segmented worms. Worms are multicellular and typically have a long tube-like body and no limbs. All worms have bilateral symmetry. Organisms with bilateral symmetry have a body with a single plane of symmetry which divides it into two mirror images. Most worms reproduce sexually, although some can reproduce asexually.

Sea stars, brittle stars, sea urchins and sea cucumbers are echinoderms. All echinoderms live in the ocean, from warm tropical reefs to the icy arctic poles. Most echinoderms have radial symmetry and reproduce sexually. However, some can also reproduce asexually.

Echinoderms produce a hard internal structure called an endoskeleton which gives their outer covering a rough, spiny appearance.

Mollusks are animals with soft bodies, often with a hard outer covering called a mantle. Most mollusks live in the ocean, with some living on land or in fresh water. Common mollusks include octopus, squid, clams, snails and slugs.

The soft body of mollusks contains tissues and organs to carry out life processes. They have digestive, respiratory and circulatory systems. Most mollusks have a specialized mouth structure called a radula which is a series of tiny teeth used for scraping food particles into the mouth.

Arthropods are the most diverse and numerous group of animals. They make up over 80 percent of all known species of animals on Earth. They live in all areas of the Earth – from the deep ocean to hot, dry deserts and moist tropical rainforests.

Common aquatic arthropods include crustaceans such as crabs, shrimp and lobsters. Terrestrial arthropods include insects, spiders, ticks and millipedes.
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Incredible! We need these kind of videos for all biology topics!! Keep on!

oneofcrores