My Science School

‘Survival of the fittest’ describes the evolution theory of Charles Darwin. In the struggle to survive, the species that are healthy, strong, and have adapted themselves best to their environment will win. They ensure their survival through healthier genetic material that is passed on to their offspring. Thus, a giraffe with a longer neck can reach leaves high on the trees to feed himself. While a giraffe with a shorter neck may stay hungry, since he has access only to the leaves lower on the tree. Eventually, the hungry giraffe may become so weak that he falls prey to lions. 

Charles Darwin (1809-1882) was a British naturalist. At a time, when people still believed that each living creature was created by God, he began his research on finches on the Galapagos Islands to the west of South America. He found that all finches originated from a single species. This turned the prevalent picture of nature as God’s creation upside down and he faced a lot of opposition from the Church. However, his theory was accepted quickly by his colleagues, and when he published his ‘theory of evolution’, the book was quickly sold out. 

Dinosaurs existed on Earth 65 million years ago. Today, the scientists believe that their mass extinction was triggered by a huge meteorite hit to the east of Mexico. The meteorite impact caused blasts and flood waves. Huge quantities of poisonous gases filled the Earth’s atmosphere. Then there was acid rain that polluted the seas and the plants died. Huge dust clouds blocked the heat from the sun and it became cold. The cold-blooded dinosaurs became sluggish and starved. Young ones did not hatch from their eggs. Only the small animals, which adapted themselves quickly and did not need a lot of food, survived.

 

The grey whale lived around 300 years ago in the Atlantic and Pacific Oceans. The giant animals were hunted extensively for their meat and oil. They became extinct in the Atlantic by the end of the 17th century, but can still be found in the Pacific Ocean. Around 20,000 animals migrate every year in October from Alaska in the north to the coast of Mexico, where they give birth to their young ones in winter. In west pacific, there are at most 200 grey whales at present and they are listed as critically endangered. These animals are sensitive to noise and are being displaced from their habitat because of the construction of drilling rigs for the crude oil industry.

Elephants are hunted for their tusks. These are made of ivory and were used to make jewellery sold at high prices. Many elephants were shot for their tusks, and even today they have to be protected from poachers in wildlife parks. Other animals are also hunted for their body parts. The Asian black bear is hunted for its gall bladder, rhinos for their horns, seals and big cats for their skin. A few wild species of crocodiles are killed because their skin is used for making bags and shoes. Hunting is also done for the thrill of the chase and a greed for the trophy, such as a bear or tiger skin. 

Since the time animals have evolved species continue to become extinct. The most well-known example of extinct species is that of the dinosaurs. Often the species cannot adjust fast enough to the changing environmental conditions, or new species arise and displace the existing ones. Today, many species are becoming extinct because of the actions of humans. Elephants, big cats, and rhinos are hunted ruthlessly, forest areas are cleared, and the grey whales are endangered. These are only a few of the species mentioned in the ‘Red List’. On a positive note, new animal species are also being discovered.

 

Amphibians such as frogs and newts are more dependent on the aquatic habitat than reptiles. Their eggs are protected only by a thin membrane and are laid in water. Many of them go through several developmental stages, till they become adults. Unlike amphibians, reptiles such as tortoises, crocodiles or snakes have a scaly skin. Their eggs are covered by a hard calcite shell and are laid on land. 

Female fish lay eggs—they spawn. The male fish eject their semen on the eggs, and thus fertilize them. Many fish like the salmon return to their place of birth for laying eggs. The salmon eggs hatch in streams and from freshwater fish turn into saltwater fish in 1-3 years. Then, they remain in the sea up to 4 years. When they wish to reproduce, they return to their birthplace covering a distance of as much as 6000 km. They have to swim against the current and overcome all the obstacles in their way. Once at the destination they spawn. It is a mystery how the salmons find their birthplace. Scientists assume that they are guided by the magnetic field of the Earth. 

Insects have the largest number of species among animals on the Earth. Out of ten different animal species, eight are of insects. They can survive in almost all types of habitats regardless of temperature. Many can survive only in specific environmental conditions, while others are found in all parts of the world. The reason for this difference within the species is not known. Insects have six legs and a body divided into three parts with a solid outer covering called the armour. Many insects are useful (bees which pollinate fruit tree flowers), while others are harmful (plant louse on indoor plants). 

‘Mammal’ is derived from the word ‘mammary’. The young ones of mammals suckle milk from the teats of the mother. This milk contains all the essential nutrients for growth. Except for the monotremes, all mammals are born as young ones and are not hatched from eggs. Contrary to almost all other animal species, mammals nurture and train their young ones for a considerable time. Mammals have a constant body temperature of 36-40°C, so they need a hide (like an elephant) or a thick layer of fat (like a whale) as protection against extreme heat or cold.

Biologists have classified the animals according to their common features. Animals that share a lot of common features are known as species. For instance, all members of the dog species have similar body structures and group behaviour. Similar species are grouped together in one family, similar families are grouped in orders, and orders are further combined to form classes. The fox, wolf, and dog species combine to make one ‘family’ of canine predators. Together with the cat and bear families, they belong to the ‘order’ of predators in the ‘classes of mammals, which in turn belong to the vertebrates in the ‘kingdom’ of animals. 

There are more than 1.5 million animal species. Ranging from simple animals like sponges and jellyfish, the invertebrates include the arthropod phylum with over 1 million species of insects. The higher- level vertebrates include fish with about 35,000 species. Around 350 million years ago, when aquatic animals moved to land, they adapted to the new environment and amphibians were born. They adapted some more and became reptiles. From reptiles came the birds and around 4000 known species of mammals. 

A lot of things that are commonly used in commercial farming are prohibited in ecological agriculture. In ecological agriculture, fields are not sprayed with chemical pesticides, and artificial fertilizers are not added to the soil. Animals are raised in ways appropriate for maintaining the health of the species. For example, hens are not crammed inside cages for their entire lives. They mostly feed on grains grown organically. Moreover, all animals are fed with ‘organic food’. All these measures require a lot of space and time to be completely successful. Hence, organic products are mostly expensive. 

The 19th century saw the emergence of a general concern to protect the wonders of nature. The first protected areas were set up. The Yellowstone National Park, the world’s first protected area, was established in 1872 in the middle of the Rocky Mountains. Here, an attempt was made to retain the unique landscape along with the diverse flora and fauna. This idea was soon adopted by Canada, Australia, and New Zealand, who also converted extraordinary habitats into national parks or wildlife sanctuaries. Today, there are around 2200 national parks in 120 countries. 

The United Nations Educational, Scientific and Cultural Organization (UNESCO) is a unit of the United Nations that has taken up the task of protecting the natural wonders of the world. World heritage is classified into cultural and natural heritage. Cultural heritage signifies important cultural sites, such as the pyramids in Egypt; natural heritage signifies natural wonders such as the Great Barrier Reef in Australia. Along with the places of extraordinary beauty and natural wonder that are worthy of protection, the UNESCO World Heritage list also includes those areas that tell us about the evolution of life on the Earth, such as Wadi al-Hitan (valley of whales) in Egypt, where many fossilized skeletons of whales were found.