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R/K selection theory

r/K selection theory describes the way a species controls its number of offspring. r-selection species produce many offspring. K-selected species focus on a few. Neither method is in itself superior, and they may occur in the same habitat; e.g., ...

                                               

Raccoon Dog

The raccoon dog, also known as the mangut, tanuki, or neoguri, is a member of the canid family and is from east Asia. Despite being hunted by many people, a small island in Japan has been designated a protected area for raccoon dogs.

                                               

Radiated tortoise

The radiated tortoise is a type of tortoise. It has vibrant yellow streaks down its bumpy black shell. It lives in southern and hotter parts of Madagascar. It can stay alive up to about 50 years in the wild and about 100 years in captivity.

                                               

Rafinesques big-eared bat

Rafinesques big-eared bat is a type of vesper bat. It is sometimes called the southeastern big-eared bat. It is native to the southeastern United States.

                                               

Ragdoll

The ragdoll is a cat breed that is large, with blue eyes, and a semi-longhair soft and silky coat of fur. It is usually mostly white, with light to dark marks. The ragdoll was first bred by an American breeder named Ann Baker from a Persian-like ...

                                               

Rakali

The rakali, also known as the water-rat, is an Australian native rodent. The species lives in burrows on the banks of rivers, lakes and estuaries. It feeds on aquatic insects, fish, crustaceans, mussels, snails, frogs, birds eggs and water birds. ...

                                               

Random mating

Random mating is a term in population genetics. It describes an ideal situation in which all individuals on one sex are equally potential partners of all members of the opposite sex. The technical term for it is panmixia. Random mating is one of ...

                                               

Range (biology)

In biology, the range or distribution of a species is the geographical area or habitat where the species live. Sometimes, when species are found in different regions at different times of year, terms such as summer range and winter range can be u ...

                                               

Ranoidea chloris

For another species commonly known as the red-eyed tree frog, see Agalychnis callidryas Ranoidea chloris, commonly known as the red-eyed tree frog or orange-eyed tree frog, is a frog from eastern Australia. It lives in forests, wetlands and somet ...

                                               

Ranoidea serrata

Ranoidea serrata is a tree frog from Australia. The adult male frog is 3.7 to 5.4 cm long and the adult female is 5.8 to 8.0 cm long. This frog can be green, brown, orange or tan in color, and it often has a pattern on its back so it can look lik ...

                                               

Raspberry

A raspberry is an aggregate fruit, meaning it has many parts joined together. It is similar to a blackberry, but the fruit is hollow on the inside. There are many different species of raspberry plants, but only a few of them have fruit that are s ...

                                               

Raven

A raven is a big black bird. It may be called the common raven or the northern raven. It is similar to a crow but bigger. It and the thick-billed raven are the two largest birds in the crow family, and perhaps the heaviest perching birds. The rav ...

                                               

Ray

The rays are a group of Batoid cartilaginous fish containing more than 500 described species in thirteen families. The batoids include four orders. They are mostly flattened in shape, and usually demersal, living and eating at the bottom of the s ...

                                               

Reactive attachment disorder

Reactive attachment disorder is a severe condition which affects children and is represented by markedly disturbed or substandard ways of socially relating onto others. The problem may take the form of constant failure to initiate social interact ...

                                               

Rectum

The rectum is a part of the large intestine which forms a part of the gastrointestinal system. The rectum ends in the anus which is the end of the gastrointestinal system. It is where feces or stools are stored temporarily before coming out of th ...

                                               

Red Bellied Black Snake

The Red Bellied Black Snake is a dangerous snake species found in Australia. It is a red bellied snake, and black on top, hence the name. It lives mainly on the east coast of Australia, close to a source of water. They can grow up to 1.5 metres i ...

                                               

Red deer

The red deer is one of the largest deer species. The red deer lives in most of Europe, the Caucasus Mountains region, Asia Minor and parts of western and central Asia, in Kashmir as the state animal. They can also be found in the Atlas Mountains ...

                                               

Red junglefowl

The red junglefowl is a tropical member of the family Phasianidae. They are the ancestors of all our domestic chickens. They were first domesticated in Asia, where they are native. Some of the less specialized domestics, such as the brown leghorn ...

                                               

Red wolf

The red wolf is a subspecies of wolf. It is an endangered species of wolf from Eastern North America. Red wolves were declared extinct in the wild in 1980 after the few remaining wild wolves were placed in a captive breeding program. Reintroduced ...

                                               

Red-and-green macaw

The red-and-green macaw, is a large mostly-red macaw of the Ara genus. This is the largest bird of the Ara genus. It is commonly found in the forests and woodlands of northern and central South America. They are found in flocks of 30 or more bird ...

                                               

Red-whiskered bulbul

The red-whiskered bulbul is a species of bird. It belongs in the family Pycnonotidae. It is found mainly in tropical Asia. It has been introduced in many tropical areas of the world. It feeds on fruits, nectar and small insects. Their calls are a ...

                                               

Redwood

The redwoods are a subfamily of conifers, the Sequoioideae. They are in the Cypress family Cupressaceae. It is most common in the coastal forests of Northern California and is possibly the largest tree in the world. There are three living genera ...

                                               

Reed (plant)

Reed is the general botanical term used for tall, grass-like plants of wet places. They occur in reed beds. They are all members of the order Poales. Reeds are many polyphyletic species, which have all adapted to this wet habitat by convergent ev ...

                                               

Remora

Remora sometimes called a suckerfish or sharksucker, is an elongated, brown fish in the order Perciformes and family Echeneidae. They are small fish that live on and around sharks. They eat stray bits of food left by the shark and tiny shrimp-lik ...

                                               

Renal cell carcinoma

Renal cell carcinoma is a type of renal cancer. Often, if it is found early, it can be cured. However, if the cancer has already spread to other parts of the body metastasized by the time it is diagnosed, it is much more difficult to treat succes ...

                                               

Reptiliomorpha

Reptiliomorpha is a clade of the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians. Unfortunately, different experts have used the term in several different ways. It has even been used ...

                                               

Respiration

Respiration is the process in which nutrients are converted into useful energy in a cell. During respiration, energy is released in a form that can be used by cells. All living things respire. Both plant and animal cells use the process of respir ...

                                               

Restless legs syndrome

Restless legs syndrome is a serious neurological disorder. It involves an irresistible urge to move certain regions of the human body to stop odd or uncomfortable sensation. This condition often involves the legs, torso, the head or the arms. Mov ...

                                               

Rete testis

The rete testis have concentrated sperm and fluid in them, and they help the epididymis to absorb this fluid. If the fluid is not absorbed, the person can be infertile.

                                               

Reticulated python

The reticulated python is a species of Python found in Southeast Asia. Adults can grow to 22.8 feet in length but average is 9.8-19.7 feet. They are the worlds longest snakes and longest reptile, but not the most heavily built. They usually weigh ...

                                               

Retina

The retina is the thin layer of cells that lines the back of the eyeball in humans and in many animals. It is made mainly of neurons and its role is to sense the light which gets into the eye and send information about it to the brain. Most infor ...

                                               

Retinal migraine

Retinal migraine is a medical condition that affects the eyes by causing vision loss in one eye for less than 1 hour, usually for about 10–20 minutes. When these retinal migraines happen they can also cause a headache, either a diffuse headache w ...

                                               

Revealed frog

The revealed frog, orange-thighed tree frog or whirring tree frog is a frog from Australia. It is related to the brown tree frog. It lives in three different places in Queensland and New South Wales, but scientists think the frogs living in diffe ...

                                               

Rhesus macaque

The rhesus macaque, often called the rhesus monkey and Indian monkey, is one of the best known species of Old World monkeys. It lives in a wide area, and has an unknown but quite large population. It lives in a broad range of habitats. Native to ...

                                               

Rheumatic fever

Rheumatic fever is an inflammatory disease that happens in children and young adults as a result of becoming infected by group A streptococci bacteria. The first attack usually happens between the ages of 5 and 15. It affects the heart, skin, joi ...

                                               

Rib cage

The ribcage is a part of the skeleton of humans and some animals. It is made up of curved bones called ribs. The rib cage is found in the chest area. It protects a persons internal organs from damage. Most humans have 12 pairs of rib bones with o ...

                                               

Ribonuclease

Ribonuclease is a type of enzyme that chops RNA into smaller parts. There are many different versions of the enzyme. All organisms studied contain many RNases of many different sorts. This shows that RNA degradation is a very ancient and importan ...

                                               

Richea

Richea is a genus of shrubs or trees in the family Ericaceae. The number of species is 10 - 12. The genus is very close with genus Dracophyllum. Richea grows in island Tasmania and also in Australia; many species grows in mountains. It is evergre ...

                                               

Ricin

Ricin is a poison. It is a highly toxic, naturally occurring protein. It is produced in the seeds of the castor oil plant Ricinus communis. A dose the size of a few grains of table salt can kill an adult human. The median lethal dose LD 50 of ric ...

                                               

Right upper quadrant (abdomen)

The right upper quadrant, is an anatomical area of the human body, this area may also be called the epigastrium. The RUQ extends from the median plane to the right of the patient, and from the umbilical plane to the right ribcage. Pain localized ...

                                               

Right whale

The right whales, also known as the black whales are baleen whales with bow-shaped lower jaw and a head that is up to one-quarter of the body length. The head is hairier than most whales; up to 300 hairs are found on the tip of the lower jaw and ...

                                               

Rigor mortis

Rigor Mortis, the first sign of post-mortem decomposition, literally translates to stiffness of death’ in Latin. As the name suggest, rigor mortis is the process in which a body stiffens after death. During this process, all the muscles in the bo ...

                                               

Ring-tailed lemur

The ring-tailed lemur is a primate from the group of lemurs. It lives in the dry regions of southwest Madagascar. This lemur weighs between 2 to 3.5 kilograms 4.4 to 7.7 lb. It can live up to 20 years. It is a mid-sized lemur. The striped tail ma ...

                                               

Riodinidae

Riodinidae is a family of butterflies. They are commonly known as riodinids or metalmarks. Metalmarks get their name from the bright, metallic markings found on the wings of most species. The family has nearly 2.000 species in it. The metalmarks ...

                                               

Rockhole frog

The rockhole frog, Australian cross-banded tree frog or skipping frog is a small frog from Australia. It lives in Western Australia and the Northern Territory. Male adult frogs are about 2 cm long and females are 2.2 cm long. They have webbed hin ...

                                               

Rockhopper penguin

The rockhopper penguins are closely related crested penguins that were thought to be a single species. They are now usually split into two or three species. Not all experts agree on the classification of these penguins. Some think all three are d ...

                                               

Rockjumper

Rockjumpers are a genus and family of small birds. They are found in southern Africa, around the Lesotho highlands and South Africa. The birds are omnivorous, meaning that they eat both plants and animals. There are two species: the Cape Rockjump ...

                                               

Rosaceae

Rosaceae is a large family of plants. There are about 100-120 genera with between 3.000 and 4.000 species in them. Well-known plants from the family include: Roses Peaches, Cherries, and Apricots Raspberries Strawberries Apples, and Pears Plants ...

                                               

Rose-ringed parakeet

The rose-ringed parakeet also known as the ring-necked parakeet, is a tropical species of bird, with a wide range in Africa and south Asia. The rose-ringed parakeet is sexually dimorphic. The adult male has a red or black neck ring and the hen an ...

                                               

Roths tree frog

Roths tree frog or northern laughing tree frog is a frog from Australia. It lives in Western Australia, the Northern Territory and Queensland. This frog can be 5.0 cm long. Each frog can change colour from very light brown during the day to dark ...