Animals are important 

               Or

Animals contribute to human existence.

                Or

How animals are important to humans?

                 Or

Why animals are important to human beings?

Answer:

( Introduction )

Humans started to rely on animals from the beginning of their existence which is evident from the cave paintings.

The earliest cave paintings in France, date back 30,000 years and depict rhinoceros, lions, Buffalo, mammoths and horses.
It is a fact that humans are also animals who have changed and adapted thousands of years to take on their current form and dominance over other animals.
About two million years ago, human primates started making and using stone tools and weapons, indicating the beginning of the Stone Age.
In 1995 archaeologists found three wooden spears in a cave near Helmstedt, Germany. They were supposed to be 400,000 years old. 
Humans were then hunter-gatherers. In those times, humans lived as nomads, depending on plants and animals in one area and then moving on to the next.
Scientists believe that large animals like mammoths and many others were driven to extinction around 10,000 BC because of climate changes, overhunting by humans or both. 
So humans turned to hunting smaller animals and then started cultivating plants, changing to a settled existence and domesticating animals for their needs.

The many ways in which humans rely on animals:

1. Food sources: Food which we get from animals includes many items such as fish, shellfish, meat, eggs, honey, dairy products, and exotic fare such as insects, grubs and highly relished palolo worms. 

Eggs and dairy products from animals

A good part of the food we eat is obtained from animals mostly cattle. They are raised to be eaten. Some are hunted for food in their natural habitat. For example, chicken( poultry), pork ( pig), mutton( lamb), venison( deer), beef( cows and buffaloes), and chevron ( goat meat). Also, seafood includes sea creatures like fish, crabs,  lobsters, oysters etc.

Dairy products like milk, curd, cream, cheese, butter etc also come from animals.

Honey is also obtained from animals cause we get it from bees, who work hard to collect it.

On a global basis animals ( including fish) provide approximately 17% of energy and more than 35% of dietary protein for humans.

 Animal source food( ASF) along with caloric ( energy) intake, also gives nutrients needed for the healthy functioning of the human body. ASF also contain a lot of micronutrients. They contain proteins which have amino acids ( the building blocks of proteins) that are well-matched to the human body's requirements. 

Thus animals make a good source of food for humans.

2. Non-edible economic products:

When an animal is slaughtered, it gives both, edible and inedible or non-edible parts. Around 55% is classified under edible by-products and 45% as inedible which are used in various industries like cosmetics, fabrics pharmaceuticals and more. Some are listed below:

(a) Plastic bags: Plastic industries use animal fat to reduce friction in materials.

Also, keratin protein from chicken feathers has been researched for making plastics, adhesives and non-woven materials.

(b) Tyres of cars and bikes:

 Many times animal-based stearic acid is used to help rubber in tyres to hold shape under steady surface friction.

(c) Natural leather: 

Natural leather is obtained from tanning or chemical treatment ( to prevent decaying) of animal skin and hides.

They are strong, flexible and durable materials. The skin of cattle, sheep, goats, horses, buffaloes, pigs, hogs and aquatic animals such as seals and alligators are used.

(d) Down:

Down is the soft layer of feathers on the skin of a duck or goose mainly in the chest or belly area.

These soft feathers are used in pillow-making companies. 

It is mostly obtained as a by-product of the food industry and collected after slaughter but there is also a practice of collecting them from live birds, which is cruel and unethical and condemned worldwide by animal lovers and animal welfare advocates.

(e) Fur: 

Fur is a thick growth of hair that covers the skin of mammals. Fur is obtained from certain mammals such as foxes, Mink, beavers, rabbits, raccoons, Otters, Seals and many more.

(f) Wool: 

Wool is made from the natural hair of various animals. To make wool, the hair of animals is harvested and spun into yarn. Then this yarn is weaved into the garment or another form of textile. 

Wool has the properties of durability and thermal insulation. While cotton consists of plant cellulose, wool consists of approximately 97% protein and, 3% fat.

(g) Ivory: 

Ivory is hard material from the tusks and teeth of animals.

Ivory has been valued since ancient times. Elephant ivory is the most important source but ivory from walruses, hippopotami, sperm whales, orcas and warthogs are also used. The trade of African and Asian elephants is illegal.

(h) Biogenic limestone:

Biogenic limestone is formed from the accumulation of shells and skeletal remains of calcareous marine organisms.

This limestone is a source of lime( calcium oxide) which has been further used in steel manufacturing, mining, paper production, water purification treatment and plastic production.

(i) Chalk:

It is a variety of limestone which is composed of shells of minute marine organisms such as foraminifera, coccoliths and rhabdoliths.

Chalk is mined for use in the industry such as bricks, quick lime and putty. It is also used in agriculture to raise the pH in soil with high acidity and education for writing and drawing. 

(j) Marble:

Marble is a crystallised form of limestone or dolomite. We, humans, use marble in architecture, sculpture, design and more.

3. Transport and labour:

Humans use animals in transportation and also to aid in physical labour. 

They are domesticated and trained to help humans.

Domesticated animals like oxen, camels, horses, donkeys etc are used in transport or for riding or pulling wagons and sledges. Even Asian Elephants are trained to do heavy-loading work.

Llamas of South America can carry a load of 25 to 30% of their body weight. 

Nowadays, animal carts used for loading and transportation are very rare but still used in some rural or remote areas.

4. Biomedical uses:

(a). Research:

Animal use for research in the biomedical field is for several different purposes as follows:

(i). Study of disease:

To study the evolution, symptoms and treatment of diseases, animals (mammals) are deliberately given the disease and conditions to research for the wellness of humans.

(ii). Development of new drugs:

For developing new drugs, tests are done on animals.

Animals are used as models to study diseases and develop and test potential forms of treatments.

New medicines require testing because researchers must measure the useful and harmful effects of a drug on the whole organism.

 

The most common animals used in biomedical experiments are mice, rats and guinea pigs as they are biologically similar to humans and susceptible to most of the health issues as humans. Also, they have a short lifecycle so can be easily studied for their whole life.

(b) Products and extracts:

(i) Venom:

Animal venom is mostly a complex mixture of peptides and proteins. This complex mixture varies according to the species that produce it.

Mostly it is from bees, snakes, scorpions and spiders.

Venomous animals are valuable resources in therapeutics.

(ii) Insulin: 

Animal insulin is derived from the pancreas of cows and pigs. It is purified to reduce the chances of developing a reaction in the user.

But nowadays human insulin is preferred to animal insulin

(iii) Pigs or Cow's heart valves:

Biological valves also called bioprosthetic valves obtained from cows or pigs. These valves last between 10-15 years.

Pig heart valves are actual pig heart valves, whereas cow valves are not actual valves but are tissues surrounding the cow's heart. It can undergo calcification but pig valves don't calcify, instead have more chance of tearing off.

(iv) Antibodies for protective inoculations:

Example:Tetanus anti-toxin is obtained from the blood serum of horses previously inoculated with tetanus toxoid.

Tetanus antitoxin is given to the person at risk of infected wounds.

Example:Equine( horses) hyper-immune serum is used as an antivenom to treat poisonous bites or stings from various snakes, spiders, jellyfish, stone fish and Scorpions.

Example: Horses are also used to produce diphtheria antitoxin by injecting them with diphtheria-causing bacteria.

5. Ecological value:

(a). Essential links in the Food chains:

In the open sea, diatoms are considered the major photosynthesizers but since they are so minute that only extremely tiny animals can feed upon them.

Copepods are too small to be directly collected for consumption by humans.

They are in turn food for infant fishes and other small zooplankton. Thus, passing through several levels of consumption, the energy and the mass trapped in the diatoms eventually benefits us, humans, in the form of tuna, cod and other fish.

 Should the human-origin pollutants (anthropogenic pollutants) decimate the key species of zooplankton, which can feed on diatoms, the higher level of the oceanic food chain will collapse even if diatoms are abundant. 

(b) Essential for pollination of most flowering plants:

Animals are essential for the pollination of most flowering plants. 

The use of pesticides in an unwise manner can result in widespread crop failure, ultimately leaving only one option but only living on grains ( which are wind-polluted).

 If the pollinator species, most of which are insects, die off globally, the world will be depleted of most types of higher vegetation thus leaving no option for our survival.

(c) Bio-controlling agents ( the maintenance of natural checks on detrimental population balance of plants and animals).

(Question: what are biocontrol, or bio-controlling agents?)

 Biocontrol is the process where natural predators are used to control the population of pests or invasive species. So mostly the organisms which prey on these pests are called biocontrol agents.

Example: To avoid possible chemical insecticide injury to its valuable animal collection, the San Diego Zoo, is said to rely entirely on biocontrol to protect its equally valuable plant collection. For instance, the release of laboratory-raised insectivorous ( insect eating). Insects such as ladybird beetles. 

Example: Hippopotamuses in Africa and manatees in Florida are important agents in clearing waterways of obstructing vegetation such as water Hyacinth.

 

6. Psychological benefits:

(a). Esthetic value: 

(i) Subjects and inspiration for works of art, from cave paintings to present-day creations.

(ii) some cultures revere totem animals and cultivate in themselves the positive attributes they perceive in animals.

(b). Affectional bonds:

(i) Pets and residents in wildlife parks, fulfilling various uneconomic human needs.

(ii) Used by some psychiatrists in their work with patients.

Psychological bonding of humans and animals 

Example:

The tremendous popularity of pets and wildlife parks indicates that they provide some positive psychological reinforcement that may be of incalculable significance to the mental health of humanity as a whole. It has been seen that suicide rates are lower among pet owners.

Even in regions where there are fewer sources of food available for humans, and extreme deprivation circumstances, people of some cultures and religions consider animals sacred and endowed with an inherent right to share the earth with humans. 

We humans are so vastly benefited and thus dependent on other animals that we started studying their lives to get the utmost benefit and still not harm them and maintain the ecosystem. 

Zoology is the branch of science that deals with the scientific study of animal life. Which is further subdivided into subdivisions or Branches of Zoology so that a detailed study of this diversified animal kingdom can be achieved benefiting both equally.