Category Zoology

Which is the smallest and lightest bone in the human body?

The stapes is the smallest and lightest bone in the human body at 3mm x 2.5 mm in size. The shape of a stirrup, it is one of three tiny bones in the middle ear, collectively known as the ossicles, that convey sound waves from the outer ear to the inner ear. The other two are the malleus (hammer) and the incus (anvil).

The stapes develops from the second pharyngeal arch during the sixth to eighth week of embryological life. The central cavity of the stapes, the obturator foramen, is due to the presence embryologically of the stapedial artery, which usually regresses in humans during normal development.

The stapes is one of three ossicles in mammals. In non-mammalian four-legged animals, the bone homologous to the stapes is usually called the columella; however, in reptiles, either term may be used. In fish, the homologous bone is called the hyomandibular, and is part of the gill arch supporting either the spiracle or the jaw, depending on the species. The equivalent term in amphibians is the pars media plectra.

The stapes appears to be relatively constant in size in different ethnic groups. In 0.01–0.02% of people, the stapedial artery does not regress, and persists in the central foramen. In this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all. Rarely, the stapes may be completely absent.


Picture Credit : Google

How do people work with Animals?

People Who Work with Animals

Do you love animals? There are many kinds of jobs for people who do. A few of those jobs are listed here.

Veterinary surgeons, or vets, keep animals healthy. City vets deal mostly with pets, giving them injections to keep them well. Country vets take care of farm animals, such as cows and horses.

Zoologists study animals to find out where and how they live, how they get along with people and other animals, and how they change over time. Zoologists work in laboratories, zoos, or museums. Or they work at wildlife refuges in the jungle, at sea, or wherever animals live.

Naturalists study nature by watching it carefully. They hike in the country to watch birds, or they visit museums, parks, and zoos. Many naturalists keep notes, sketches, and photographs of everything they see. You don’t have to wait to be a grown-up to be a naturalist! Many areas have nature-study programmes for children.

Game wardens and rangers help protect wild animals in National parks and game preserves. They rescue animals stranded by floods or fire and make sure people obey fishing, hunting, and camping laws.

Farmers and ranchers raise livestock that provide food for people all over the world. Farmers raise such livestock as chickens, pigs, and dairy and beef cattle. Ranchers raise sheep and cattle on huge farms.

Picture Credit : Google

How do people rescue animals?

People to the Rescue

Many people around the world are doing all they can to help save animals from becoming extinct. Zoos used to be just a collection of animals kept in cages to amuse people. Today, zoos try to keep the animals happy, too. Many animals are given large areas to live in that feel just like their homes in the wild. Zoos also breed and take care of endangered animals to save them from extinction.

Wildlife reserves and national parks are areas of land where animals and plants can live safely. There are reserves and national parks all around the world.

People help animals in other ways, too. In many countries, laws ban the hunting or catching of certain animals. Often, when animals are put in danger by a crisis, such as an oil spill, people work around the clock to save them.

Picture Credit : Google

What is excessive hunting?

Too Much Hunting

Hyenas and hawks, foxes and frogs, spiders and snakes, lions and lizards, dolphins and dragonflies – all these, and many more animals, are hunters. They hunt and kill other creatures for food. Some people think such killing is cruel, but it keeps nature in balance.

People are hunters, too. They hunt for sport and for food. In many cases, hunting does not upset the balance of nature. In many countries, people are allowed to hunt only animals that are plentiful.

But some hunters kill tigers, leopards, otters, alligators, and other rare animals for their fur or skin. They sell the fur or skin to companies that make coats, shoes, belts, and bags from them. Hunters kill rhinoceroses for their horns and elephants for their tusks. They kill as many of these animals as they can for money. In many parts of the world these animals are being wiped out by hunting!

Many governments around the world have passed hunting laws to try to save animals. Hunters who break these laws and are caught have to pay huge fines – or go to prison.

Picture Credit : Google

How do people affect animals?

All around the world, every day, and more people are being born. All these people need somewhere to live and work, and they need food. People take up space. They need space for their farms, their factories, their houses, and their roads. They cut down forests to make room for crops, houses, and roads. Whenever this happens, animal habitats and homes are destroyed. Habitats are also destroyed when people pollute rivers, lakes, and forests with harmful chemicals or other waste.

Tropical rain forests are home to many kinds of animals and plants. But large areas of tropical rain forests are being destroyed each year as people gather lumber, minerals, and other materials. Scientists and other people worry that if much more of the rain forests are destroyed, thousands of species of plants and animals will become extinct.

Picture Credit : Google

What types of elephants are extinct?

Dinosaurs were not the only prehistoric animals to become extinct. Millions of years ago, many elephant-like animals roamed the earth. Over the years, these creatures adapted to their changing environment. For example, they developed different kinds of trunks and tusks depending on what kind of food was available. Sometimes the animals could not adapt quickly enough to changes in their environment. When this happened, the animals became extinct.

The moeritherium was among the first elephant-like animals. It lived about 60 million years ago. The moeritherium had neither trunk nor tusks and was about as large as a pig.

The deinotherium lived between 24 million and 2 million years ago. It had backward-curving tusks that grew down from its lower jaw. Platybelodons lived during the same time as the deinotherium. They had huge scoop-shaped teeth in their lower jaws, which were probably used to pull up water plants.

Mammoths lived from at least 4 million to 10,000 years ago. They were enormous animals with teeth like those of modern-day elephants. Mammoths that lived during the Ice Age had long hair on their bodies, which helped protect them from the extreme cold.

Today, there are two kinds of elephants – the African elephant and the Indian elephant, also called the Asian elephant. In a million years, these and many of today’s animals will be gone. There may be many new kinds of animals.

Picture Credit : Google

How do we know about dinosaurs and other animals of long ago?

Of course, there were no people on the earth when dinosaurs were alive. So how do we know about dinosaurs and other animals of long ago?

Sometimes, when a dinosaur died, its body lay on the muddy ground. The soft parts rotted away, but mud covered the bones and kept them from rotting. Over millions of years, the bones and the mud turned into rock. This helped keep them whole. Over many more millions of years, sun and rain wore away the rock around it, leaving the rocky skeleton. These rocky bones and skeletons are called fossils.

Scientists look for fossils such as this and dig them out of the ground. By studying fossils, the scientists can tell what the animal looked like. They can tell what it ate by the shape of its teeth. Often, they can even tell how well the animal could see and hear and smell things.

Some creatures living in the world today look very much like some of the fossils of ancient animals. By studying these creatures, scientists can get an even better idea of life on the earth millions and millions of years ago.

Picture Credit : Google

Why did dinosaurs go extinct?

Why Are They Gone?

Just as you change while you grow, the world and the things that live on it change, too. Most scientists believe that the earth has changed many times in the past, and that many kinds of animals have lived on our planet.

Once, there were scaly reptiles as big as houses. Once there were horses no bigger than cats. And, very long ago, no animals of any kind lived on land. All the animals lived in the ocean.

Dinosaurs were very important animals. They ruled the earth for more than 100 million years. They wallowed in great swamps and prowled through hot, damp forests.

Then something happened, and all the dinosaurs died. We don’t know why dinosaurs became extinct.

Some scientists think dinosaurs became extinct slowly. Swamps began drying up. New plants were taking the place of old ones. Perhaps dinosaurs could not live with these changes. Other scientists think Earth was struck by a huge asteroid. The air then filled with dust that blocked out the sun’s rays. Eventually, this changed the climate and led to the death of the dinosaurs.

Perhaps all these things, and others that we don’t know about, caused the dinosaurs to die out. It’s a great mystery.

Picture Credit : Google

Why are animals in danger?

Animals in Danger 
Hundreds of years ago, thousands of birds called dodos lived on the earth. But people overhunted them for food and introduced new animal enemies to their habitats. Now there are no dodos. Today, the numbers of polar bears, rhinoceroses, tigers, and many other animals are going down. These animals are in danger. Why? 
• Their homes are being destroyed. 
• People hunt them for their fur, horns, skins, and meat. Some are hunted for sale as pets and some because people think they are pests. 
• Pollution kills them. 
• Growing numbers of people crowd out animals and use up all the land and food. 
• People introduce new animals to a habitat, upsetting the balance of nature. 
Unless people work hard to save them, many other animals will become extinct like the dodo. 

Picture Credit : Google

What do we mean by food chain?

Food Chain

A field of green grass waves in the wind. A furry rabbit hops by and nibbles the grass. As the rabbit scurries around, an owl perches overhead. The owl swoops down, grabs the rabbit, and flies away to eat it. When it has eaten its fill, the owl leaves part of the rabbit’s body in another field of grass. The rabbit’s body feeds the soil.

It may seem cruel that animals kill and eat one another. But this is just one way in which wild creatures help each other and keep nature in balance. The grass, the rabbit and the owl are part of an important system in nature called a food chain.

All food chains begin with sunlight. Sunlight provides food for plants. Plants are the primary producers in a food chain. They use sunlight, water, and air to produce food to live and grow.

Animals that eat plants are another link in the food chain. They are consumers. Animals that eat the plant-eating animals are also consumers. The rabbit and the owl are consumers.

Tiny living things called decomposers are also part of the food chain. They break down dead plants and animals into parts. These parts nourish the soil in which the plants grow.

Picture Credit : Google