The smallest living bird is the bee humming bird from Cuba, which is only 6 cm long and weighs 3 g. A long slim beak takes up nearly half of its length.
Hummingbirds use their long tongue to feed on flower nectar, which they sip while in hovering flight. Their wings beat 80 times per second while they are hovering.
Hummingbirds are able to fly backwards and sideways as they manoeuvre to
Picture credit: google
The largest living bird is the ostrich. It stands up to 2.5 m high and weighs 135 kg. Two extinct birds, the moa of New Zealand and the elephant bird of Madagascar, stood about 3 m high and would dwarf even the ostrich. The largest living bird capable of flight is the albatross, which has a wing span of 3.5 m. However, the largest-known flying bird lived about 2 million years ago. It was a condor-like bird with a 5 m wing span.
Picture credit: google
Birds’ bodies are very highly modified to give them the power of flight. Their bones are hollow to keep them light. Their bodies are extremely light too, allowing them to glide and to fly with the minimum of effort. For example, an eagle with a wing span of more than 2 m weighs less than 4 kg. Birds have air sacs linked to their lungs to provide extra oxygen as they flap their wings.
Flying is not just a matter of flapping wings up and down. It is usually a mixture of gliding and powered flight. When the wings are flapped they move in a complicated path, scooping air downwards and backwards. The wings twist so that the air is pushed back in the right direction to provide lift. The wings are twisted again on the forward stroke so that they slide easily through the air and do not slow down the bird’s flight.
Picture credit: google
Several birds have lost the ability to fly, because flight is unnecessary for their way of life. Penguins and ostriches have very small wings and cannot fly. The penguin uses its wings in underwater ‘flight’, while the ostrich uses its wings only when displaying to other ostriches. The extinct dodo and the modern kiwi are examples of flightless birds. A rare kind of parrot has also lost the power of flight.
Picture credit: google
The structure of a bird is very similar to that of a mammal. Birds differ from mammals in that their front limbs are modified as wings, and they possess feathers instead of hair. Birds do not have teeth but use their horny beak to cut, crush and tear their food, although much of it is swallowed whole. They use a muscular organ called the gizzard to grind their food after swallowing it. Many birds swallow stones which lodge in their gizzard and help this grinding process. Birds’ wings are based on heavily adapted forelimbs. On each wing a very small thumb is hidden beneath the feathers. The other fingers are fused together to provide a firm support for the wing.
Picture credit: google
We like to think that humans are the most successful animals, but it could be argued that rats are even more successful. Rats are found wherever people live, and they can adapt to live in most environments. The two common types are the brown rat and the black rat. Rats produce up to seven litters per year, each one containing between 6 and 22 young.
Rats are a source of disease, and their droppings frequently contaminate stored food. Black rats were responsible for the spread of the Black Death in the Middle Ages, which killed millions of people in Europe. Rats are very difficult to control because they quickly adapt to the effect of poisons and learn to avoid traps.
Rats are also highly intelligent and are able to exploit new food sources. They climb walls to enter food stores, or tunnel beneath walls, and can even bite through plastic or water pipes in order to drink. They are omnivorous, which means that they can live on almost any edible substance.
Picture credit: google
The largest living land animal is the African elephant, which reaches a weight of 7,500 kg and stands 3-4 m high at the shoulders when fully grown.
However, the African elephant is dwarfed by some extinct plant-eating dinosaurs, which may have weighed at least 80 tonnes, and reached a length of 30 m. It was thought that the weight of these huge creatures had to be supported by water. It is now known that they inhabited regions similar to those of elephants.
Picture credit: google
Mammals, like other animals, sometimes develop a body shape or lifestyle that is very similar to that of an unrelated animal living in exactly the same environment.
Dolphins, for example, have a very similar body shape to sharks and to the extinct marine reptile ichthyosaurus, because they inhabit the same environment and have a very similar way of life. In the same way, kangaroos have adapted to a similar lifestyle to antelopes and sheep, grazing in open grasslands. This process is called parallel evolution, and it demonstrates how animals develop in the same way, in order to fit in with the available living space and food supply.
Picture credit: google
Bats are the only mammals that are capable of true flight. Several other mammals are capable of gliding for considerable distances.
Bats are efficient flyers, although their wings have developed very differently from those of birds. A bat’s wing is like an outstretched hand with very long fingers, connected by thin skin. Other mammals, such as squirrels and marsupials, are able to glide by means of sheets of skin stretched between their front and back legs. They use these sheets to travel from tree to tree. These animals are not closely related and yet they have developed the ability to fly quite separately, so this is an example of parallel evolution.
Picture credit: google
Shrews are the smallest kind of mammal. Some weigh only 2.5 g. A shrew looks like a mouse with a long snout, but it is not closely related to rodents. Shrews feed on insects and other animals, and need to eat almost continuously in order to survive.
Picture credit: google