Dog

The dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog was the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in human history. The word "dog" may also mean the male of a canine species,as opposed to the word "bitch" for the female of the species.Dogs were domesticated from gray wolves about 15,000 years ago.They must have been very valuable to early human settlements, for they quickly became ubiquitous across world cultures. Dogs perform many roles for people, such as hunting, herding,pulling loads, protection, assisting police and military, companionship, and, more recently, aiding handicapped individuals. This impact on human society has given them the nickname "Man's best friend" in the western world. In 2001, there were estimated to be 400 million dogs in the world.

Over the 15,000 year span the dog had been domesticated, it diverged into only a handful of landraces, groups of similar animals whose morphology and behavior have been shaped by environmental factors and functional roles. Through selective breedingby humans, the dog has developed into hundreds of varied breeds, and shows more behavioral and morphological variation than any other land mammal.For example, height measured to the withers ranges from a few inches in the Chihuahua to a few feet in the Irish Wolfhound; color varies from white through grays (usually called "blue'") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth. It is common for most breeds to shed this coat.

Physical characteristics

Coat

The coats of domestic dogs are of two varieties: "double" being common with dogs (as well as wolves) originating from colder climates, made up of a coarse guard hair and a soft down hair, or "single", with the topcoat only.Domestic dogs often display the remnants of countershading, a common natural camouflage pattern. A countershaded animal will have dark coloring on its upper surfaces and light coloring below,which reduces its general visibility. Thus many breeds will have an occasional "blaze", stripe, or "star" of white fur on their chest or underside.

Tail

There are many different shapes for dog tails: straight, straight up, sickle, curled, or cork-screw. In some breeds, the tail is traditionally docked to avoid injuries (especially for hunting dogs).In some breeds, puppies can be born with a short tail or no tail at all.This occurs more frequently in those breeds that are frequently docked and thus have no breed standard regarding the tail.

Types and breeds

While all dogs are genetically very similar, natural selection and selective breeding have reinforced certain characteristics in certain populations of dogs, giving rise to dog types and dog breeds. Dog types are broad categories based on function, genetics, or characteristics.Dog breeds are groups of animals that possess a set of inherited characteristics that distinguishes them from other animals within the same species. Modern dog breeds are non-scientific   classifications of dogs kept by modern kennel clubs. Purebred dogs of one breed are genetically distinguishable from purebred dogs of other breeds,but the means by which kennel clubs classify dogs is unsystematic. Systematic analyses of the dog genome has revealed only four major types of dogs that can be said to be statistically distinct.hese include the "old world dogs"(e.g., Malamute and Shar Pei), "Mastiff"-type (e.g., English Mastiff), "herding"-type (e.g.,Border Collie), and "all others" (also called "modern"- or "hunting"-type)

Health

Dogs are susceptible to various diseases, ailments, and poisons, some of which can affect humans. To defend against many common diseases, dogs are often vaccinated

.Some breeds of dogs are prone to certain genetic ailments such as elbow or hip dysplasia,blindness, deafness, pulmonic stenosis, cleft palate, and trick knees. Two serious medical conditions particularly affecting dogs are pyometra, affecting unspayed females of all types and ages, and bloat, which affects the larger breeds or deep-chested dogs. Both of these are acute conditions, and can kill rapidly. Dogs are also susceptible to parasites such as fleas, ticks, and mites, as well as hookworm, tapeworm, roundworm, and heartworm

Dogs are highly susceptible to theobromine poisoning, typically from ingestion of chocolate. Theobromine is toxic to dogs because although the dog's metabolism is capable of breaking down the chemical, the process is so slow that even small amounts of chocolate can be fatal, especially dark chocolate.

Dogs are also vulnerable to some of the same health conditions as humans, including diabetes, dental and heart disease, epilepsy, cancer, hypothyroidism, and arthritis.

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 Health risks to humans.

In the USA, cats and dogs are a factor in more than 86,000 falls each year.It has been estimated around 2% of dog-related injuries treated in UK hospitals are domestic accidents. The same study found that while dog involvement in road traffic accidents was difficult to quantify, dog-associated road accidents involving injury more commonly involved two-wheeled vehicles.

Toxocara canis (dog roundworm) eggs in dog feces can cause toxocariasis. In the United States, about 10,000 cases of Toxocara infection are reported in humans each year, and almost 14% of the US population is infected.In Great Britain, 24% of soil samples taken from public parks contained T. canis eggs.Untreated toxocariasis can cause retinal damage and decreased vision.Dog feces can also contain hookworms that cause cutaneous larva migrans in humans.

The incidence of dog bites, and especially fatal dog bites, is extremely rare in America considering the number of pet dogs in the country.Fatalities from dog bites occur in America at the rate of one per four million dogs.A Colorado study found bites in children were less severe than bites in adults.The incidence of dog bites in the US is 12.9 per 10,000 inhabitants, but for boys aged 5 to 9, the incidence rate is 60.7 per 10,000. Moreover, children 

have a much higher chance to be bitten in the face or neck.Sharp claws with powerful muscles behind them can lacerate flesh in a scratch that can lead to serious infections.

In the UK between 2003 and 2004, there were 5,868 dog attacks on humans, resulting in 5,770 working days lost in sick leave

Health benefits for humans

A growing body of research indicates the companionship of a dog can enhance human physical health and psychological wellbeing.Dog and cat owners have been shown to have better mental and physical health than nonowners, making fewer visits to the doctor and being less likely to be on medication than nonowners. In one study, new pet owners reported a highly significant reduction in minor health problems during the first month following pet acquisition, and this effect was sustained in dog owners through to the end of the study. In addition, dog owners tookconsiderably more physical exercise than cat owners and people without pets. The group without pets exhibited no statistically significant changes in health or behaviour. The results provide evidence that pet acquisition may have positive effects on human health and behaviour, and that for dog owners these effects are relatively long term.Pet ownership has also been associated with increased coronary artery disease survival, with dog owners being significantly less likely to die within one year of an acute myocardial infarction than those who did not own dogs.

The health benefits of dogs can result from contact with dogs, not just from dog ownership. For example, when in the presence of a pet dog, people show reductions in cardiovascular, behavioral, and psychological indicators of anxiety.The benefits of contact with a dog also include social support, as dogs are able to not only provide companionship and social support themselves, but also to act as facilitators of social interactions between humans.One study indicated that wheelchair users experience more positive social interactions with strangers when they are accompanied by a dog than when they are not.

The practice of using dogs and other animals as a part of therapy dates back to the late 18th century, when animals were introduced into mental institutions to help socialize patients with mental disorders. Animal-assisted intervention research has shown that animal-assisted therapy with a dog can increase a person with Alzheimer’s disease’s social behaviours, such as smiling and laughing.One study demonstrated that children with ADHD and conduct disorders who participated in an education program with dogs and other animals showed increased attendance, increased knowledge and skill objectives, and decreased antisocial and violent behavior compared to those who were not in an animal-assisted program.

  

As pets

“The most widespread form of interspecies bonding occurs between humans and dogs” and the keeping of dogs as companions, particularly by elites, has a long history.However, pet dog populations grew significantly after World War II as suburbanization increased. In the 1950s and 1960s, dogs were kept outside more often than they tend to be today (using the expression “in the doghouse” to describe exclusion from the group signifies the distance between the doghouse and the home) and were still primarily functional, acting as a guard, children’s playmate, or walking companion.From the 1980s, there have have been changes in the role of the pet dog, such as the increased role of dogs in the emotional support of their owners. People and dogs have become increasingly integrated and implicated in each other’s lives,to the point where pet dogs actively shape the way a family and home are experienced.

There have been two major trends in the changing status of pet dogs. The first has been the ‘commodification’ of the dog, shaping it to conform to human expectations of personality and behaviour.The second has been the broadening of the concept of the family and the home to include dogs-as-dogs within everyday routines and practices.

There are a vast range of commodity forms available to transform a pet dog into an ideal companion.

The list of goods, services and places available is enormous: from dog perfumes, couture, furniture and housing, to dog groomers, therapists, trainers and care-takers, dog cafes, spas, parks and beaches, and dog hotels, airlines and cemeteries.While dog training as an organized activity can be traced back to the 18th century, in the last decades of the 20th century it became a high profile issue as many normal dog behaviors such as barking, jumping up, digging, rolling in dung, fighting, and urine marking became increasingly incompatible with the new role of a pet dog.Dog training books, classes and television programs proliferated as the process of commodifying the pet dog continued.

The majority of contemporary dog owners describe their dog as part of the family, 

although some ambivalence about the relationship is evident in the popular reconceptualisation of the dog-human family as a pack. A dominance model of dog-human relationships has been promoted by some dog trainers, such as on the television program Dog whisperer,however it has been disputed that "trying to achieve status" is characteristic of dog–human interactions.Pet dogs play an active role in family life; for example, a study of conversations in dog-human families showed how family members use the dog as a resource, talking to the dog, or talking through the dog, to mediate their interactions with each other. Another study of dogs’ roles in families showed many dogs have set tasks or routines undertaken as family members, the most common of which was helping with the washing-up by licking the plates in the dishwasher, and bringing in the newspaper from the lawn.Increasingly, human family members are engaging in activities centred on the perceived needs and interests of the dog, or in which the dog is an integral partner, such as Dog dancing and Doga.

Cat 
The cat also known as the domestic cat or housecat to distinguish it from other felines and felids, is a small furry
domesticated carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests. Cats have been associated with humans for at least 9,500 years, and are currently the most popular pet in the world.Owing to their close association with humans, cats are now found almost everywhere on earth.
Cats are similar in anatomy  to the other felids, with strong, flexible bodies, quick reflexes, sharp retractable claws, and teeth adapted to killing small prey.As nocturnal predators, cats use their acute hearing and ability to see in near darkness to locate prey. Not only can cats hear sounds too faint for human ears, they can also hear sounds higher in frequency than humans can perceive. This is because the usual prey of cats (particularly rodents such as mice) make high frequency noises, so the hearing of the cat has evolved to pinpoint these faint high-pitched sounds. Cats rely more on smell than taste, and have a much better sense of smell than humans.


Despite being solitary hunters, cats are a social species and use a variety of vocalizations,pheromones and types of body language for communication. These include meowing, purring,trilling, hissing, growling, and grunting.


Cats have a rapid breeding rate. Under controlled breeding, they can be bred and shown as registered pedigree pets, a hobby known as cat fancy. Failure to control the breeding of pet cats by spaying and neutering and the abandonment of former household pets has resulted in large numbers of  feral cats worldwide, with a population of up to 60 million of these animals in the United States alone

Effects of pets' health 

Keeping animals as pets may become detrimental to their health if certain requirements are not kept. An important issue is the inappropriate feeding, which may produce clinical effects (like the consumption of chocolate by dogs).Passive smoking is another recurring problem, aggravated by the fact that fur animals groom themselves, which means taking in extra harmful substances that have landed on their fur, not just those inhaled.

Effects of pets on their caregiver's health

Health benefits

Pets have the ability to stimulate their caregivers, in particular the elderly, giving people someone to take care of, someone to exercise with,and someone to help them heal from a physically or psychologically troubled past.Having a pet may help people achieve health goals, such as lowered blood pressure, or mental goals, such as decreased stress.There is evidence that having a pet can help a person lead a longer, healthier life. In a study of 92 people hospitalized for coronary ailments, within a year 11 of the 29 without pets had died, compared to only 3 of the 52 who had pets. A recent study concluded that owning a pet can reduce the risk of a heart attack by 2% and that pets are better than medication in reducing blood pressure. Owning a pet can also prolong survival of a heart attack.Dogs which are trained to be guide dogs can help people with disabilities

Pets in long-term care institutions

Even pet owners residing in a long-term care facility, such as a hospice or nursing home, experience health benefits from pets. Pets for nursing homes are chosen based on the size of the pet, the amount of care that the breed needs, and the population and size of the care institution.Appropriate pets go through a screening process and, if it is a dog, additional training programs to become a therapy dog.Different pets require varying amounts of attention and care; for example, cats have lower maintenance requirements than dogs.