Search this website:
Phylum Rotifera, indeterminate growth, Epithelial tissue, Rotifers, Arctic tundra
Deeper web pages:
no cell walls
heterotrophic - get organic carbon by eating other organisms
ingestive nutrition - bring large chunks of food into body, digest the food chemically and mechanically in digestive tube, and cells lining the digestive tract absorb nutrients and conduct them to circulatory system
Animal, multicellular organism that obtains energy by eating food. With over 2 million known species, and many more awaiting identification, animals are the most diverse forms of life on earth. They range in size from 30-m (100-ft) long whales to microscopic organisms only 0.05 mm (0.002 in) long. They live in a vast range of habitats, from deserts and Arctic tundra to the deep-sea floor. Animals are the only living things that have evolved nervous systems and sense organs that monitor their surroundings. They are also the only forms of life that show flexible patterns of behavior that can be shaped by past experience. The study of animals is known as zoology.
Animals are multicellular organisms, a characteristic they share with plants and many fungi. But they differ from plants and fungi in several important ways. Foremost among these is the way they obtain energy. Plants obtain energy directly from sunlight through the process of photosynthesis, and they use this energy to build up organic matter from simple raw materials. Animals, on the other hand, eat other living things or their dead remains. They then digest this food to release the energy that it contains. Fungi also take in food, but instead of digesting it internally as animals do, they digest it before they absorb it.
Most animals start life as a single fertilized cell, which divides many times to produce the thousands or millions of cells needed to form a functioning body. During this process, groups of cells develop different characteristics and arrange themselves in tissues that carry out specialized functions. Epithelial tissue covers the body's inner and outer surfaces, while connective tissue binds it together and provides support. Nervous tissue conducts the signals that coordinate the body, and muscle tissue–which makes up over two-thirds of the body mass of some animals–contracts to make the body move. This mobility, coupled with rapid responses to opportunities and hazards, is one feature that distinguishes animals from other forms of life.
Some kinds of animal movement, such as the slow progress of a limpet as it creeps across rocks, are so slow that they are almost imperceptible. Others, such as the attacking dive of a peregrine falcon or the leap of a flea, are so fast that they are difficult or even impossible to follow. Many single-celled organisms can move, but in absolute terms, animals are by far the fastest-moving living things on earth.
Animal life spans vary from less than 3 weeks in some insects to over a century in giant tortoises. Some animals, such as sponges, mollusks, fish, and snakes, show indeterminate growth, which means that they continue to grow throughout life. Most, however, reach a pre-defined size at maturity, at which point their physical growth stops.
Rotifer, any of a phylum of multicellular, generally microscopic, aquatic animals that are abundant worldwide, and are most frequently found in freshwater bogs, ponds, and puddles. Rotifers vary in shape but always have retractable, hairlike crowns of cilia that, in motion, resemble turning wheels. (Among the first microscopic life forms to be studied, they were commonly known as wheel animalcules.) The animals can attach themselves temporarily to surfaces by means of a cementing secretion from the “foot” of the body. They reproduce sexually, but males are rare; except under severe conditions, the eggs develop parthenogenetically. Rotifers feed on other microorganisms; a few species are parasitic.
Scientific classification: Rotifers make up the phylum Rotifera.
Article key phrases:
Search this website: