Taxonomy of invertebrates, Biology tutorial


Taxonomy or classification is a system in which information on organisms are collected and stored in a systematic manner for simple retrieval. The feature of Biology which deals with the categorization of organisms is generally termed as taxonomy. It comprises the naming of organisms or nomenclature and the methodical assignment of organisms to groups termed taxa; this is termed to as systematics. Systematics and Taxonomy are very frequently interchanged. 

Classification of Invertebrates:

1) Protozoa:

Protozoa are very simple, single-celled animals. They are the smallest of the entire animals. Most protozoa are microscopic in size and can merely be seen beneath a microscope. Though, they do breathe, move and reproduce similar to multicellular animals.

There are quite a few kinds of protozoa. The amoebas are clear, shapeless cells. Flagellates encompass a body shape looking similar to a hair.

However we cannot view them, protozoa do a lot for us. Protozoa play a valuable role in the food chain as a source of food for the fish and other animals. A few protozoa are useful to humans by eating dangerous bacteria. Unluckily, other protozoa are parasites and can be injurious to humans by transmitting the disease.

2) Echinoderms: Starfish, Sea Urchin and family

Echinoderms are marine animals which live in the ocean. Common echinoderms comprise the sea urchin, sea star, sand dollar and sea cucumber. Most of the echinoderms encompass arms or spines which radiate from the center of their body. The central body includes their organs and their mouth for feeding.

Sea stars, generally termed as the starfish, have 5 or more arms joined to their body. On the bottom of the Starfish are small tube feet to aid with the movement and feeding. The starfish's mouth is beneath, and is capable of eating other sea life like mussels and clams.

The other kind of echinoderm is the sea urchin. Sea urchins contain lots of spines joined to their body. Such spines aid to protect them from predators.

3) Annelids: Worms and Leeches

There are around 9,000 species of Annelids known nowadays, comprising leeches and worms. They can be found nearly anywhere in the world. Annelids have existed on Earth for over 120 million years.

Annelids have bodies which are categorized into segments. They have extremely well-developed internal organs. One common feature of annelids is that they do not have any limbs.

Some annelids might have long bristles. Others have shorter bristles and seem smooth, similar to the earthworm.

There are numerous kinds of worms. Generally known worms comprise roundworms, earthworms and flatworms. Most of the worms are small, measuring fractions of an inch to some inches long. Other worms like the ribbon worm, can grow up to 100 feet in length. Several worms are considered parasites, in that they live within the human body.

4) Mollusks:

Mollusks were the first inhabitants of the Earth. Fossils of mollusks have been discovering in rocks and date back over 500 million years. Mollusk fossils are generally well preserved since of their hard shell.

Most of the mollusks encompass a soft, skin-like organ covered by a hard outside shell. Some mollusks live on land, like the slug and snail. Other mollusks live in water, like the oyster, clam, mussel, squid and octopus.

5) Arthropods:

Arthropods make up over 75% of the world's animal species. Arthropods comprise animals like insects, arachnids and crustaceans. The largest group of Arthropods is the insects. The next largest group is the crustaceans, comprising crabs and lobsters. The arachnids comprise spiders and ticks. Other Arthropods comprise millipedes and centipedes.

Arthropods encompass limbs with joints which let them to move. They as well encompass an exoskeleton, which is a hard, external skeleton. Their body cavity includes the nervous system, circulatory system, digestive system and reproductive system.

6) Crustaceans:

Crustaceans are a kind of Arthropod. The name might not sound well-known, however you probably know them. You might even have eaten one.

Crustaceans live generally in the ocean or other waters. Most generally known crustaceans are the lobster, crab and barnacle.

Crustaceans contain a hard, external shell that protects their body. Crustaceans encompass a head and abdomen. The head consists of antennae which are part of their sensory system. The abdomen comprises the heart, digestive system and reproductive system.

7) Arachnids: Spiders, Ticks and Scorpions

Arachnids are a kind of arthropod. You are familiar with most of them as spiders. Common arachnids are scorpions, spiders, ticks and mites.

Similar to other arthropods, the arachnids encompass a hard exoskeleton and jointed appendages for walking. Most of the arachnids encompass four pairs of legs. In some, the first pair of legs might be employed for holding their prey and feeding. Dissimilar other arthropods, arachnids don't have antennae.

8) Insects:

Insects are the biggest group of arthropods. There are around 800,000 different kinds of insects. Insects are very adaptable, living almost all over the world. Common insects comprise the fly, butterfly, beetle, moth, dragonfly, bee, wasp and praying mantis.

Insects encompass an exoskeleton which covers their whole body. An insect's body comprises of three parts - the head, thorax and abdomen.

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