Animal classification

Animal classification

Animals are classified in a variety of ways. This helps scientists to study the relationships in animal groups and to see the whole animal family tree as it has developed through time. The study of animal classification is called taxonomy.

The basic unit of an animal is the cell. A cell is the smallest unit of any animal or plant. Some animals are one celled, some consist of millions of cells. Each cell is filled with a living matter called protoplasm. It also has a nucleus that is the center of the cell and directs its activities. The cytoplasm is the area outside of the nucleus. Each cell is held together by a cell membrane which is like a very thin skin for the cell. Many cells have different jobs to do in an animal, whether they be bone, blood, skin cells.

A group of the same kinds of cells are called tissues. A group of tissues that work together to do a job in the animal's body is an organ. The stomach, heart, kidneys, lungs are examples of organs. A group of organs that do a number of jobs of the same kind are systems.

Animals are grouped together or classified in a variety of ways. Some of them are:

Whether an animals in one celled or many celled.

How an animal's bodily systems differ.

Animal groupings are similar to plants. The groupings are:

• Kingdom - There are two basic kingdoms, the plant and animal kingdoms. There is a third with animals that bridge the plant and animal kingdom.
• Phylum - Within the plant and animal kingdoms are big groupings called phylum or phyla. Animals are grouped into phyla that have broad similar characteristics.
• Classes - These are a finer division of a phyla.
• Orders - These are divisions of classes.
• Families - These are divisions of
• Genera - These are the divisions of families.
• Species - These are the divisions of genera.

Ecosystem

Ecosystem
An ecosystem is a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all the non-living physical factors of the environment.

An ecosystem is a natural system consisting of all plants, animals and microorganisms (biotic factors) in an area functioning together with all the non-living physical (abiotic) factors of the environment.

The term ecosystem was coined in 1930 by Roy Clapham, to denote the physical and biological components of an environment considered in relation to each other as a unit. British ecologist Arthur Tansley later refined the term, describing it as the interactive system established between biocoenosis (a group of living creatures) and their biotope (the environment in which they live).

Central to the ecosystem concept is the idea that living organisms are continually engaged in a set of relationships with every other element constituting the environment in which they exist. The human ecosystem concept is then grounded in the deconstruction of the human/nature dichotomy, and the emergent premise that all species are ecologically integrated with each other, as well as with the abiotic constituents of their biotope.

Ecosystems can be bounded and discussed with tremendous variety of scope, and describe any situation where there is relationship between organisms and their environment. A system as small as a household or university, or as large as a nation state, may then be suitably discussed as a human ecosystem. While they may be bounded and individually discussed, (human) ecosystems do not exist independently, but interact in a complex web of human and ecological relationships connecting all (human) ecosystems to make up the biosphere. As virtually no surface of the earth today is free of human contact, all ecosystems can be more accurately considered as human ecosystems.

Human

Humans

Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin: "wise man" or "knowing man") in the family Hominidae (the great apes). Compared to other living organisms on Earth, humans have a highly developed brain capable of abstract reasoning, language, and introspection. This mental capability, combined with an erect body carriage that frees their upper limbs for manipulating objects, has allowed humans to make far greater use of tools than any other species. DNA evidence indicates that modern humans originated in Africa about 200,000 years ago, and they now inhabit every continent, with a total population of over 6.6 billion as of 2007.

Like most primates, humans are social by nature; however, humans are particularly adept at utilizing systems of communication for self-expression, the exchange of ideas, and organization. Humans create complex social structures composed of cooperating and competing groups, ranging in scale from small families and partnerships to species-wide political, scientific and economic unions. Social interactions between humans have also established an extremely wide variety of traditions, rituals, ethics, values, social norms, and laws which form the basis of human society. Humans also have a marked appreciation for beauty and aesthetics which, combined with the human desire for self-expression, has led to cultural innovations such as art, literature and music.

Humans are also noted for their desire to understand and influence the world around them, seeking to explain and manipulate natural phenomena through science, philosophy, mythology and religion. This natural curiosity has led to the development of advanced tools and skills; humans are the only known species to build fires, cook their food, clothe themselves, and use numerous other technologies.

Frogs

Frogs

The frog is an amphibian in the order Anura (meaning "tail-less", from Greek an-, without + oura, tail), formerly referred to as Salientia (Latin saltare, to jump). The name frog derives from Old English frogga,(compare Old Norse frauki, German Frosch, older Dutch spelling kikvorsch), cognate with Sanskrit plava (frog), probably deriving from Proto-Indo-European praw = "to jump".

Adult frogs are characterised by long hind legs, a short body, webbed digits, protruding eyes and the absence of a tail. Most frogs have a semi-aquatic lifestyle, but move easily on land by jumping or climbing. They typically lay their eggs in puddles, ponds or lakes, and their larvae, called tadpoles, have gills and develop in water. Adult frogs follow a carnivorous diet, mostly of arthropods, annelids and gastropods. Frogs are most noticeable by their call, which can be widely heard during the night or day, mainly in their mating season.

The distribution of frogs ranges from tropic to subarctic regions, but most species are found in tropical rainforests. Consisting of more than 5,000 species described, they are among the most diverse groups of vertebrates. However, populations of certain frog species are significantly declining.

A distinction is often made between frogs and toads on the basis of their appearance, caused by the convergent adaptation among so-called toads to dry environments; however, this distinction has no taxonomic basis. The only family exclusively given the common name "toad" is Bufonidae, but many species from other families are also called "toads," and the species within the toad genus Atelopus are referred to as "harlequin frogs."

Cats

Cats

The cat are known as the domestic cat or house cat to distinguish it from other felines, is a small carnivorous species of crepuscular mammal that is often valued by humans for its companionship and its ability to hunt vermin. It has been associated with humans for at least 9,500 years.

Physiology

Size

Diagram of the general anatomy of a male cat.
Cats typically weigh between 2.5 and 7 kg (5.5–16 pounds); however, some breeds, such as the Maine Coon, can exceed 11.3 kg (25 pounds). Some have been known to reach up to 23 kg (50 pounds) due to overfeeding. Conversely, very small cats (less than 1.8 kg / 4.0 lb) have been reported.

Skeleton

Cats have 7 cervical vertebrae like almost all mammals, 13 thoracic vertebrae (humans have 12), 7 lumbar vertebrae (humans have 5), 3 sacral vertebrae like most mammals (humans have 5 because of their bipedal posture), and, except for Manx cats, 22 or 23 caudal vertebrae (humans have 3 to 5, fused into an internal coccyx). The extra lumbar and thoracic vertebrae account for the cat's enhanced spinal mobility and flexibility, compared with humans. The caudal vertebrae form the tail, used by the cat as a counterbalance to the body during quick movements. Cats also have free-floating clavicle bones, which allows them to pass their body through any space into which they can fit their head.

Mouth

Cats have highly specialized teeth for the tearing of meat. The premolar and first molar together compose the carnassial pair on each side of the mouth, which efficiently functions to shear meat like a pair of scissors. While this is present in canids, it is highly developed in felines. The cat's tongue has sharp spines, or papillae, useful for retaining and ripping flesh from a carcass. These papillae are small backward-facing hooks that contain keratin which also assist in their grooming.

As facilitated by their oral structure, cats use a variety of vocalizations and types of body language for communication, including mewing ("meow" or "miaow"), purring, hissing, growling, squeaking, chirping, clicking, and grunting.

Ears

Thirty-two individual muscles in each ear allow for a manner of directional hearing: a cat can move each ear independently of the other. Because of this mobility, a cat can move its body in one direction and point its ears in another direction. Most cats have straight ears pointing upward. Unlike dogs, flap-eared breeds are extremely rare. (Scottish Folds are one such exceptional genetic mutation.) When angry or frightened, a cat will lay back its ears, to accompany the growling or hissing sounds it makes. Cats also turn their ears back when they are playing, or to listen to a sound coming from behind them. The angle of a cat's ears is an important clue to their mood.

Legs

Cats, like dogs, are digitigrades: they walk directly on their toes, the bones of their feet making up the lower part of the visible leg. Cats are capable of walking very precisely, because like all felines they directly register; that is, they place each hind paw (almost) directly in the print of the corresponding forepaw, minimizing noise and visible tracks. This also provides sure footing for their hind paws when they navigate rough terrain.

Unlike dogs and most mammals, cats walk by moving both legs on one side and then both legs on the other side. Most mammals move legs on alternate sides in sequence. Cats share this unusual gait with camels, giraffes, some horses ('pacers'), and a select few other mammals. There is no known connection between these animals which might explain this.

Like all members of family Felidae except the cheetah, cats have retractable claws. In their normal, relaxed position the claws are sheathed with the skin and fur around the toe pads. This keeps the claws sharp by preventing wear from contact with the ground and allows the silent stalking of prey. The claws on the forefeet are typically sharper than those on the hind feet. Cats can extend their claws voluntarily on one or more paws at will. They may extend their claws in hunting or self-defense, climbing, "kneading", or for extra traction on soft surfaces (bedspreads, thick rugs, etc.). It is also possible to make a cooperative cat extend its claws by carefully pressing both the top and bottom of the paw. The curved claws may become entangled in carpet or thick fabric, which may cause injury if the cat is unable to free itself.

Most cats have five claws on their front paws, and four or five on their rear paws. Because of an ancient mutation, however, domestic cats are prone to polydactyly, and may have six or seven toes. The fifth front claw (the dewclaw) is in a more proximal position than those of the other claws. More proximally, there is a protrusion which appears to be a sixth "finger". This special feature of the front paws, on the inside of the wrists, is the carpal pad, also found on the paws of big cats and dogs. It has no function in normal walking, but is thought to be an anti-skidding device used while jumping.

Skin

Cats possess rather loose skin; this allows them to turn and confront a predator or another cat in a fight, even when it has a grip on them. This is also an advantage for veterinary purposes, as it simplifies injections. In fact, the life of cats with kidney failure can sometimes be extended for years by the regular injection of large volumes of fluid subcutaneously, which serves as an alternative to dialysis.

The particularly loose skin at the back of the neck is known as the scruff, and is the area by which a mother cat grips her kittens to carry them. As a result, cats tend to become quiet and passive when gripped there. This tendency often extends into adulthood, and can be useful when attempting to treat or move an uncooperative cat. However, since an adult cat is heavier than a kitten, a pet cat should never be carried by the scruff, but should instead have their weight supported at the rump and hind legs, and at the chest and front paws. Often (much like a small child) a cat will lie with its head and front paws over a person's shoulder, and its back legs and rump supported under the person's arm.

Senses

Cat senses are attuned for hunting. Cats have highly advanced hearing, eyesight, taste, and touch receptors, making the cat extremely sensitive among mammals. Cats' night vision is superior to humans although their vision in daylight is inferior. Humans and cats have a similar range of hearing on the low end of the scale, but cats can hear much higher-pitched sounds, up to 64 kHz, which is 1.6 octaves above the range of a human, and even one octave above the range of a dog. A domestic cat's sense of smell is about fourteen times as strong as a human's. To aid with navigation and sensation, cats have dozens of movable vibrissae (whiskers) over their body, especially their face. Due to a mutation in an early cat ancestor, one of two genes necessary to taste sweetness has been lost by the cat family.

Metabolism

A cat sleeping curled into a tight ball to conserve body heat.

Cats conserve energy by sleeping more than most animals, especially as they grow older. The daily duration of sleep varies, usually 12–16 hours, with 13–14 being the average. Some cats can sleep as much as 20 hours in a 24-hour period. The term cat nap refers to the cat's ability to fall asleep (lightly) for a brief period and has entered the English lexicon – someone who nods off for a few minutes is said to be "taking a cat nap".

Due to their crepuscular nature, cats are often known to enter a period of increased activity and playfulness during the evening and early morning, dubbed the "evening crazies", "night crazies", "elevenses" or "mad half-hour" by some.

The temperament of a cat can vary depending on the breed and socialization. Cats with "oriental" body types tend to be thinner and more active, while cats that have a "cobby" body type tend to be heavier and less active.

The normal body temperature of a cat is between 38 and 39 °C (101 and 102.2 °F). A cat is considered febrile (hyperthermic) if it has a temperature of 39.5 °C (103 °F) or greater, or hypothermic if less than 37.5 °C (100 °F). For comparison, humans have a normal temperature of approximately 36.8 °C (98.6 °F). A domestic cat's normal heart rate ranges from 140 to 220 beats per minute, and is largely dependent on how excited the cat is. For a cat at rest, the average heart rate should be between 150 and 180 bpm, about twice that of a human.

Genetics

Blue-eyed cats with white fur have a reputation for having greater incidence of genetic deafness.

A study by the National Cancer Institute published in the journal Science asserts that all house cats are descended from a group of self-domesticating desert wildcats Felis silvestris lybica circa 10,000 years ago, in the Near East. All wildcat subspecies can interbreed, but domestic cats are all genetically contained within F. s. lybica.

The domesticated cat and its closest wild ancestor both possess 38 chromosomes, in which over 200 heritable genetic defects have been identified, many homologous to human inborn errors. Specific metabolic defects have been identified underlying many of these feline diseases. There are several genes responsible for the hair color identified. The combination of them gives different phenotypes.

Features like hair length, lack of tail or presence of a very short tail (bobtail cat) are also determined by single alleles and modified by polygenes.

The Cat Genome Project, sponsored by the Laboratory of Genomic Diversity at the U.S. National Cancer Institute Frederick Cancer Research and Development Center in Frederick, Maryland, focuses on the development of the cat as an animal model for human hereditary disease, infectious disease, genome evolution, comparative research initiatives within the family Felidae, and forensic potential.

It is a common misconception that all white cats with blue eyes are deaf, leading to some people rejecting blue-eyed white cats as pets. This is not true, as there are many blue-eyed cats with perfect hearing. However, white cats with blue eyes do have slightly higher incidences of genetic deafness than white cats of other eye colors.

All felines, including the big cats, have a genetic anomaly that prevents them from tasting sweetness, which is a likely factor for their usual indifference to or avoidance of fruits, berries, and other sugary foods.

Space

SKY MAPS & NOTES

Sitting high across the faint Milky Way at this time of year are three bright stars that form the Summer Triangle. (Yes, they are still visible as winter approaches!) The top-left star of the trio is Deneb, the leading star of Cygnus, the Swan. Off to its right is the brightest member, Vega in Lyra, the Harp. Finishing off the triangle lower down is Altair, the main star of Aquila, the Eagle. If your skies are light-polluted then you may not see the Milky Way, even though it really is there.

The November full Moon occurs as it travels closest to the Earth on its monthly orbit - making it one of the largest full Moons this year.

Mercury
This month sees Mercury's best apparition of the year. Look for this elusive world low in the south-east at around 6am. The bright star to the lower-right is Spica, the leading star of Virgo, the Maiden.

As the days go by, Mercury climbs a little away from the Sun's dawn and brightens as it does so. After the 8th the planet begins its inevitable journey back into the glare. Mercury is never really around for that long and I'll be surprised if you can catch it after the 23rd when it sits near Zubenelgenubi, the main star in Libra, the Scales.
Venus
While Mercury sits low and faint, Venus sparkles much further up in the morning sky. It begins the month in the constellation of Leo, the Lion, not too far from Saturn. However, like Mercury, Venus can move quite quickly too. On the 2nd it moves into Virgo, the Maiden where it spends the rest of the month closing in on Virgo's main star, Spica.

The waning crescent Moon is to the right of Venus on the 5th, making for a fine duet in the morning skies.
Mars
Mars will rise at around 8pm at the start of the month, and about 6pm by the end, which will make it more of an easy evening object. It’s also getting brighter over this time, so it should become more noticeable, as the planet sits virtually stationary in Gemini, the Twins.

The evening of the 26th provides a good example of the ever-present movements in the sky. You can see the waning gibbous Moon above right of Mars, but it moves gradually towards the planet. Take a look at 8pm in the east then a couple of times through the evening, and finally just before dawn to see the Moon directly above Mars in the west.

Jupiter
Jupiter is low in the south-west after sunset. It's not at its very best in brightness or position, and you can only catch it from 5pm until around 6pm in the middle of the month.

Next month Jupiter will disappear totally behind the Sun to reappear in the morning skies in 2008. The waxing crescent Moon is low and to the left of the planet on the evening of the 13th.

Saturn
The famous ringed-planet is up by around 1am, meaning it is easily seen high in the south-east by dawn sitting in Leo, the Lion. The waning crescent Moon is below Saturn on the morning of the 5th.

Saturn, Regulus (the main star of Leo, the Lion) and the waning gibbous Moon are nicely lined-up on the morning of the 30th.

Meteor Showers
November is the time of the famous Leonids shower. The peak on the night of the 17th and the morning of the 18th only has the first quarter Moon to contend with. This should be setting way in the west by late evening - that's the opposite part of the sky from where the meteors will appear.

Plants

The Magic of Annual Vines
For the cost of a packet of seeds, you can quickly create a show stopping garden accent or a living hideaway for children, hide a rusty chain link fence or an unsightly garage wall, and turn an ordinary balcony into a private garden. Started from seeds, annual vines will scramble to heights of 20 feet or more, highlighting features you want to show off and covering eyesores.

Attracting Birds to the Garden
A gardener's relationship with birds is one of mutual benefit. The gardener provides for a few of the birds basic needs, and the birds help to keep down the insect population while treating us to an unending source of entertainment. Birds take their role as insect predator seriously. A single bird will gulp down 500 to 1,000 insects in an afternoon.

How to attract birds to your garden

Plants for the shade
Deciding what to plant under your shade trees is not a problem of finding something that will grow in reduced light, but of finding plants that will grow in the poor, dry soil present under trees. Your plants will be competing with the tree for nutrients and moisture, and the tree will usually win.

If the soil under the tree is dry and root-clogged to the point where you have difficulty digging a hole, you will have to improve the soil before you can plant. A layer of organic material several inches deep is the best remedy. The tree will provide you with an abundance of organic material in the form of leaves. Chop them to the size of fifty-cent pieces with a bagging lawn mower and spread them under the tree. Sprinkle them with compost activator and keep them moist. Repeat this procedure annually until the leaves have rotted into a deep humus. Earthworms will move in and loosen the subsoil, making it possible to plant the shade garden of your dreams.

Building the soil takes time and patience. To get a head start, use containers as temporary homes for your shade plants.

When selecting plants, choose those with white or pastel flowers and light or variegated foliage. Light colors will stand out in the shade, while dark colors such as reds and purples will recede into the background. I've listed some common shade-loving plants below. Some of them prefer a moist soil, and if your soil is dry you should grow them in containers.

Flower Garden Information - Popular Flowers

Flowers are usually the centerpiece of every garden, and in the Garden Guides Flowers section you will find all of the top flowering plants to make your flower garden complete. Select a top flower from the list on the right to locate a specific flower or flowering plant, or else browse through the flower categories below. Flowers from amaryllis to violet are identified by both common name and scientific name, including such perennial favorites as azalea, begonia, carnation, chrysanthemum, daisy, iris, jasmine, orchid, morning glory, marigold, tulip, rose, and many more.

Animals

Animals Index

Australian Animals
The Aquarium's Australian exhibit, Animal Planet Australia: Wild Extremes, depicts amazing stories of survival in an extreme environment.

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Amphibians
Frogs, toads, and salamanders are amphibians that most people are familiar with. Amphibians are cold-blooded (ectothermic), smooth-skinned vertebrates (animals with backbones) that are capable of living both on land and in water, usually in different stages of their lives.

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Birds
Birds are wonderfully varied creatures inhabiting all parts of the world. The most unique defining feature of these warm-blooded vertebrates is feathers. All have wings, and all but a few species fly.

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Fish
Fish are magnificently diverse in size, shape, color, and pattern. Cold-blooded, they live in both fresh and salt water, from cold regions to the tropics. Almost all have fins, gills, and scales. About 96 percent are bony fish. The rest are cartilaginous fish: sharks, skates, and rays.

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Invertebrates
No bones about it! Most of the world’s animal species - up to 99% - are invertebrates! These diverse creatures have one common characteristic: they lack the backbone and accompanying skeleton of vertebrates. Some invertebrates are very soft, but most have some support structure.

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Mammals
Mammals are warm-blooded vertebrates that can nourish their young with milk-producing mammary glands. Marine mammals have adapted to a lifestyle dependent on rivers or oceans.

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Reptiles
Most people think of snakes when they hear the word reptiles, but reptiles also include chelonians (turtles and tortoises), crocodilians (crocodiles, alligators, caiman, gavials), lizards and tuataras. They are air-breathing vertebrates with tough, waterproof skin that retains moisture.

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Cells

Cell (biology)

The cell is the structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is sometimes called the building block of life. Some organisms, such as bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion or 10¹⁴ cells; a typical cell size is 10 µm; a typical cell mass is 1 nanogram.) The largest known cell is an ostrich egg. In 1837 before the final cell theory was developed, a Czech Jan Evangelista Purkyňe observed small "granules" while looking at the plant tissue through a microscope. The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells. All cells come from preexisting cells. Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

The word cell comes from the Latin cellula, meaning, a small room. The descriptive name for the smallest living biologial structure was chosen by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in.

Preamble

Each cell is at least somewhat self-contained and self-maintaining: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities.

Mouse cells grown in a culture dish. These cells grow in large clumps, but each individual cell is about 10 micrometres across

All cells have several different abilities:

• Reproduction by cell division: (binary fission/mitosis or meiosis).
• Use of enzymes and other proteins coded for by DNA genes and made via messenger RNA intermediates and ribosomes.
• Metabolism, including taking in raw materials, building cell components, converting energy, molecules and releasing by-products. The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic molecules. This energy is derived from metabolic pathways.
• Response to external and internal stimuli such as changes in temperature, pH or nutrient levels.
• Cell contents are contained within a cell surface membrane that contains proteins and a lipid bilayer.

Some prokaryotic cells contain important internal membrane-bound compartments,but eukaryotic cells have a highly specialized endomembrane system characterized by regulated traffic and transport of vesicles.

Anatomy of cells

There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells are usually found in multicellular organisms.

Prokaryotic cells

Main article: Prokaryote

Prokaryotes are distinguished from eukaryotes on the basis of nuclear organization, specifically their lack of a nuclear membrane. Prokaryotes also lack most of the intracellular organelles and structures that are characteristic of eukaryotic cells (an important exception is the ribosome, which are present in both prokaryotic and eukaryotic cells). Most functions of organelles, such as mitochondria, chloroplasts, and the Golgi apparatus, are taken over by the prokaryotic plasma membrane. Prokaryotic cells have three architectural regions: appendages called flagella and pili — proteins attached to the cell surface; a cell envelope consisting of a capsule, a cell wall, and a plasma membrane; and a cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions. Other differences include:

• The plasma membrane (a phospholipid bilayer) separates the interior of the cell from its environment and serves as a filter and communications beacon.
• Most prokaryotes have a cell wall (some exceptions are Mycoplasma (a bacterium) and Thermoplasma (an archaeon)). It consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from "exploding" (cytolysis) from osmotic pressure against a hypotonic environment. A cell wall is also present in some eukaryotes like plants (cellulose) and fungi, but has a different chemical composition.
• A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi, which causes Lyme disease). Even without a real nucleus, the DNA is condensed in a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Plasmids can carry additional functions, such as antibiotic resistance.

Eukaryotic cells

Eukaryotic cells are about 10 times the size of a typical prokaryote and can be as much as 1000 times greater in volume. The major difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Most important among these is the presence of a cell nucleus, a membrane-delineated compartment that houses the eukaryotic cell's DNA. It is this nucleus that gives the eukaryote its name, which means "true nucleus". Other differences include:

• The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
• The eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins. All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles also contain some DNA.
• Eukaryotes can move using cilia or flagella. The flagella are more complex than those of prokaryotes.