RAT

 About Rat:

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus. Many members of other rodent genera and families are also referred to as rats, and share many characteristics with true rats.

Rats are typically distinguished from mice by their size; rats are generally large muroid rodents, while mice are generally small muroid rodents. The muroid family is very large and complex, and the common terms rat and mouse are not taxonomically specific. Generally, when someone discovers a large muroid, its common name includes the term rat, while if it is small, the name includes the term mouse. Scientifically, the terms are not confined to members of the Rattus and Mus genera, for example, the pack rat and cotton mouse.

 Species and description:

The best-known rat species are the Black Rat (Rattus rattus) and the Brown Rat (Rattus norvegicus). The group is generally known as the Old World rats or true rats, and originated in Asia. Rats are bigger than most Old World mice, which are their relatives, but seldom weigh over 500 grams (1.1 lb) in the wild.

The term "rat" is also used in the names of other small mammals which are not true rats. Examples include the North American pack rats, a number of species loosely called kangaroo rats, and others. Rats such as the Bandicoot rat (Bandicota bengalensis) are murine rodents related to true rats, but are not members of the genus Rattus. Male rats are called bucks, unmated females are called does, pregnant or parent females are called dams, and infants are called kittens or pups. A group of rats is either referred to as a pack or a mischief.

 The common species are opportunistic survivors and often live with and near humans, therefore they are known as commensals. They may cause substantial food losses, especially in developing countries. However, the widely distributed and problematic commensal species of rats are a minority in this diverse genus. Many species of rats are island endemics and some have become endangered due to habitat loss or competition with the Brown, Black or Polynesian rat.

Wild rodents, including rats, can carry many different zoonotic pathogens, such as Leptospira, Toxoplasma gondii, and Campylobacter. The Black Death is traditionally believed to have been caused by the micro-organism Yersinia pestis, carried by the Tropical Rat Flea (Xenopsylla cheopis) which preyed on Black Rats living in European cities during the epidemic outbreaks of the Middle Ages; these rats were used as transport hosts. Other zoonotic diseases linked to pest rodents include Classical swine fever and Foot-and-mouth disease.

The average lifespan of any given rat depends on which species is being discussed, but many only live about a year due to predation.

As pets:

Specially bred rats have been kept as pets at least since the late 19th century. Pet rats are typically variants of the species Brown rat, but Black rats andGiant pouched rats are also known to be kept. Pet rats behave differently than their wild counterparts depending on how many generations they have been kept as pets. Pet rats do not pose any more of a health risk than pets such as cats or dogs. Tamed rats are generally friendly and can be taught to perform selected behaviors.

CHIMPANGEE

 About Chimpangee:

Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:

§  Common Chimpanzee, Pan troglodytes (West and Central Africa)

§  Bonobo, Pan paniscus (forests of the Democratic Republic of the Congo)

Chimpanzees are members of the Hominidae family, along with gorillas, humans, and orangutans. Chimpanzees split from human evolution about 6 million years ago and the two chimpanzee species are the closest living relatives to humans, all being members of the Hominini tribe (along with extinct species of Hominina subtribe). Chimpanzees are the only known members of the Panina subtribe. The two Pan species split only about one million years ago.

Evolutionary relationship:

The genus Pan is considered to be part of the subfamily Homininae to which humans also belong. These two species are the closest livingevolutionary relatives to humans, sharing a common ancestor with humans six million years ago. Research by Mary-Claire King in 1973 found 99% identical DNA between human beings and chimpanzees, although research since has modified that finding to about 94%commonality, with some of the difference occurring in non-coding DNA. It has been proposed that troglodytes and paniscus belong with sapiensin the genus Homo, rather than in Pan. One of the arguments for this is that other species have been reclassified to belong to the same genus on the basis of less genetic similarity than that between humans and chimpanzees.

Fossils:

A lot of human fossils have been found, but chimpanzee fossils were not described until 2005. Existing chimpanzee populations in West and Central Africa do not overlap with the major human fossil sites in East Africa. However, chimpanzee fossils have now been reported fromKenya. This would indicate that both humans and members of the Pan clade were present in the East African Rift Valley during the Middle Pleistocene.

Intelligence:

Chimpanzees make tools and use them to acquire foods and for social displays; they have sophisticated hunting strategies requiring cooperation, influence and rank; they are status conscious, manipulative and capable of deception; they can learn to use symbols and understand aspects of human language including some relational syntax, concepts of number and numerical sequence; and they are capable of spontaneous planning for a future state or event.

Tool use:

One of the most significant discoveries was in October 1960 when Jane Goodall observed the use of tools among chimpanzees. Recent research indicates that chimpanzee stone tool use dates to at least 4,300 years ago. Chimpanzee tool usage includes digging into termite mounds with a large stick tool, and then using a small stick that has been altered to "fish" the termites out. A recent study revealed the use of such advanced tools as spears, with which Common Chimpanzees in Senegal sharpen with their teeth and use to spear Senegal Bushbabies out of small holes in trees. Before the discovery of tool use in chimps, it was believed that humans were the only species to make and use tools, but several other tool-using species are now known.

Social structure:

Chimpanzees live in large multi-male and multi-female social groups called communities. Within a community there is a definite social hierarchy which is dictated by the position of an individual and the influence the individual has on others. Chimpanzees live in a leaner hierarchy in which more than one individual may be dominant enough to dominate other members of lower rank. Typically there is a dominant male referred to as the Alpha male. The Alpha male is the highest-ranking male who controls the group and maintains order during any disputes. In chimpanzee society the 'dominant male' does not always have to be the largest or strongest male but rather the most manipulative and political male who can influence the goings on within a group. Male chimpanzees typically attain dominance through cultivating allies who will provide support for that individual in case of future ambitions for power. The alpha male regularly displays by making his normally slim coat puffed up to increase view size and charge to look as threatening and as powerful as possible. This serves to intimidate other members in an attempt to hold on to power and maintain authority, and it may be fundamental to the alpha male's holding on to his status. Lower-ranking chimpanzees will show respect by making submissive gestures in body language or reaching out their hand while grunting. Female chimpanzees will show deference to the alpha male by presenting their hind-quarters.

Female chimpanzees also have a hierarchy which is influenced by the position of a female individual within a group. In some chimpanzee communities, the young females may inherit high status from a high-ranking mother. The females will also form allies to dominate lower-ranking females. In contrast to males who have a main purpose of acquiring dominant status for access to mating privileges and sometimes violent domination of subordinates, females acquire dominant status for access to resources such as food. High-ranking females will often get first access to resources. In general, both genders acquire dominant status to improve social standing within a group.

GORILLA

 About Gorilla:

Gorillas are the largest species of primates. Gorillas are ground-dwelling, predominantly herbivorous apes that inhabit the forests of centralAfrica. Gorillas are divided into two species and (still under debate as of 2008) either four or five subspecies. The DNA of gorillas is highly similar to that of a human, between 95 and 99% depending on what is counted, and they are the next closest living relatives to humans after the two chimpanzee species.

Gorillas' natural habitats cover tropical or subtropical forests in Africa. Although their range covers a small percentage of Africa, gorillas cover a wide range of elevations. The Mountain Gorilla inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from 2,200–4,300 metres (7,200–14,100 ft). Lowland Gorillas live in dense forests and lowland swamps and marshes as low as sea level, with Western Lowland Gorillas living in Central West African countries and Eastern Lowland Gorillas living in the Democratic Republic of the Congonear its border with Rwanda.

Etymology:

The American physician and missionary Thomas Staughton Savage and naturalist Jeffries Wyman first described the Western Gorilla (they called it Troglodytes gorilla) in 1847 from specimens obtained in Liberia. The name was derived from the Greek word "Γόριλλαι" (Gorillai), a "tribe of hairy women" described by Hanno the Navigator, a Carthaginian navigator and possible visitor (circa 480 BC) to the area that later became Sierra Leone.

 Evolution and classification:

The closest relatives of gorillas are chimpanzees and humans, all of the Hominidae having diverged from a common ancestor about 7 million years ago. Human genes differ only 1.6% on average from their corresponding gorilla genes in their sequence, but there is further difference in how many copies each gene has.

Until recently there was considered to be a single gorilla species, with three subspecies: the Western Lowland Gorilla, the Eastern Lowland Gorilla and the Mountain Gorilla. There is now agreement that there are two species with two subspecies each. More recently it has been claimed that a third subspecies exists in one of the species. The separate species and subspecies developed from a single type of gorilla during the Ice Age, when their forest habitats shrank and became isolated from each other.

Primatologists continue to explore the relationships between various gorilla populations. The species and subspecies listed here are the ones upon which most scientists agree.

§  Genus Gorilla 

§  Western Gorilla (Gorilla gorilla)

§  Western Lowland Gorilla (Gorilla gorilla gorilla)

§  Cross River Gorilla (Gorilla gorilla diehli)

§  Eastern Gorilla (Gorilla beringei)

§  Mountain Gorilla (Gorilla beringei beringei)

§  Eastern Lowland Gorilla (Gorilla beringei graueri)

The proposed third subspecies of Gorilla beringei, which has not yet received a trinomen, is the Bwindi population of the Mountain Gorilla, sometimes called the Bwindi Gorilla.

Some variations that distinguish the classifications of gorilla include varying density, size, hair color, length, culture, and facial widths. There are now thought to be over 100,000 Western Lowland Gorillas in the wild, with 4,000 in zoos; Eastern Lowland Gorillas have a population of 4,000 in the wild and 24 in zoos. Mountain Gorillas are the most severely endangered, with an estimated population of about 620 left in the wild and none in zoos.

Physical characteristics: 

Gorillas move around by knuckle-walking, although they sometimes walk bipedally for short distances while carrying food or in defensive situations. Adult males also called as silverbacks range in height 1.65–1.75 metres (5 ft 5 in–5 ft 9 in), and in weight 140–200 kg (310–440 lb). Adult females are often half the size of a silverback, averaging about 1.4 metres (4 ft 7 in) tall and 100 kg (220 lb). Occasionally, a silverback of over 1.8 metres (5 ft 11 in) and 230 kg (510 lb) has been recorded in the wild. Obese gorillas in captivity have reached a weight of 270 kg (600 lb). Gorillas have a facial structure which is described as mandibular prognathism, that is, their mandibleprotrudes farther out than the maxilla.

The Eastern Gorilla is more darkly colored than the Western Gorilla, with the Mountain Gorilla being the darkest of all. The Mountain Gorilla also has the thickest hair. The Western Lowland Gorilla can be brown or grayish with a reddish forehead. In addition, gorillas that live in lowland forests are more slender and agile than the more bulky Mountain Gorilla.

Almost all gorillas share the same blood type (B) and, like humans, have individual finger prints. Their eye color is dark brown, framed by a black ring around the iris. 

Intelligence: 

Gorillas are considered highly intelligent. A few individuals in captivity, such as Koko, have been taught a subset of sign language (see animal language for a discussion). Like the other great apes, gorillas can laugh, grieve, have "rich emotional lives," develop strong family bonds, can make and use tools, and can think about the past and future. Some researchers believe that gorillas have spiritual feelings or religious sentiments. Gorillas have been shown to have cultures in different areas revolving around different methods of food preparation, and gorillas will show individual color preferences.

Tool use: 

The following observations were made by a team led by Thomas Breuer of the Wildlife Conservation Society in September 2005. Gorillas are now known to use tools in the wild. A female gorilla in the Nouabalé-Ndoki National Park in the Republic of Congo was recorded using a stick as if to gauge the depth of water whilst crossing a swamp. A second female was seen using a tree stump as a bridge and also as a support whilst fishing in the swamp. This means that all of the great apes are now known to use tools.

In September 2005, a two and a half year old gorilla in the Republic of Congo was discovered using rocks to smash open palm nuts inside a game sanctuary. While this was the first such observation for a gorilla, over 40 years previously chimpanzees had been seen using tools in the wild, famously 'fishing' for termites. Great apes are endowed with a semi-precision grip, and certainly have been able to use both simple tools and even weapons, by improvising a club from a convenient fallen branch.

FROGS

 About Frogs:

Frogs are amphibians in the order Anura (meaning "tail-less", from Greek an-, without + oura, tail), formerly referred to as Salientia (Latinsalere (salio), "to jump"). Most frogs are characterized by a short body, webbed digits (fingers or toes), protruding eyes and the absence of a tail. Frogs are widely known as exceptional jumpers, and many of the anatomical characteristics of frogs, particularly their long, powerful legs, are adaptations to improve jumping performance. Due to their permeable skin, frogs are often semi-aquatic or inhabit humid areas, but move easily on land. They typically lay their eggs in puddles, ponds or lakes, and their larvae, called tadpoles, have gills and develop inwater. 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 decliningsignificantly.

A popular distinction is often made between frogs and toads on the basis of their appearance, but this has no taxonomic basis. (Members of the anuran family Bufonidae are called true toads, but many species from other families are also called toads.) In addition to their ecological importance, frogs have many cultural roles, such as in literature, symbolism and religion, and they are also valued as food and as pets.

 Call:

Some frog calls are so loud, they can be heard up to a mile away. The call of a frog is unique to its species. Frogs call by passing air through the larynx in the throat. In most calling frogs, the sound is amplified by one or more vocal sacs, membranes of skin under the throat or on the corner of the mouth that distend during the amplification of the call. The field of neuroethology studies the neurocircuitry that underlies frog audition.

Some frogs lack vocal sacs, such as those from the genera Heleioporus and Neobatrachus, but these species can still produce a loud call. Their buccal cavity is enlarged and dome-shaped, acting as a resonance chamber that amplifies their call. Species of frog without vocal sacs and that do not have a loud call tend to inhabit areas close to flowing water. The noise of flowing water overpowers any call, so they must communicate by other means.

The main reason for calling is to allow males to attract a mate. Males call either individually or in a group called a chorus. Females of many frog species, for example Polypedates leucomystax, produce calls reciprocal to the males', which act as the catalyst for the enhancement of reproductive activity in a breeding colony. A male frog emits a release call when mounted by another male. Tropical species also have a rain call that they make on the basis of humidity cues prior to a rain shower. Many species also have a territorial call that is used to chase away other males. All of these calls are emitted with the mouth of the frog closed.

A distress call, emitted by some frogs when they are in danger, is produced with the mouth open, resulting in a higher-pitched call. The effectiveness of the call is unknown; however, it is suspected the call intrigues the predator until another animal is attracted, distracting them enough for its escape.

Many species of frog have deep calls, or croaks. The English onomatopoeic spelling is "ribbit". The croak of the American bullfrog (Rana catesbiana) is sometimes spelt "jug o' rum". Other examples are Ancient Greek brekekekex koax koax for probably Rana ridibunda, and the description in Rigveda 7:103.6 gómāyur éko ajámāyur ékaħ = "one has a voice like a cow's, one has a voice like a goat's".

Etymology and terminology:

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 fromProto-Indo-European praw = "to jump".

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".

Taxonomy:

The use of the common names "frog" and "toad" has no taxonomic justification. From a taxonomic perspective, all members of the order Anura are frogs, but only members of the family Bufonidae are considered "true toads". The use of the term "frog" in common names usually refers to species that are aquatic or semi-aquatic with smooth and/or moist skins, and the term "toad" generally refers to species that tend to be terrestrial with dry, warty skin. An exception is the fire-bellied toad (Bombina bombina): while its skin is slightly warty, it prefers a watery habitat.

Frogs and toads are broadly classified into three suborders: Archaeobatrachia, which includes four families of primitive frogs; Mesobatrachia, which includes five families of more evolutionary intermediate frogs; and Neobatrachia, by far the largest group, which contains the remaining 24 families of "modern" frogs, including most common species throughout the world. Neobatrachia is further divided into the Hyloidea and Ranoidea. This classification is based on such morphological features as the number of vertebrae, the structure of the pectoral girdle, and the morphology of tadpoles. While this classification is largely accepted, relationships among families of frogs are still debated. Future studies of molecular genetics should soon provide further insights to the evolutionary relationships among anuran families.

Some species of anurans hybridise readily. For instance, the Edible Frog (Rana esculenta) is a hybrid of the Pool Frog (R. lessonae) and the Marsh Frog (R. ridibunda). Bombina bombina and Bombina variegata similarly form hybrids, although these are less fertile, giving rise to a hybrid zone.