- The Big Bang Theory
According to this theory, about 15 billion years ago, Universe was a very small speck of mass. Everything in the Universe, all the galaxies, stars, planets, and even the matter making up our body, was squished up tightly in the tiny space.
After a very long time, this speck exploded. All of a sudden, in a giant flash of unimaginable heat and power, the Universe was born. Over a period of billions and billions of years, Universe became what we see today.
Slowly stars began to form, and around these planets were formed. In a quiet galaxy known as Milky Way, the Earth, a small rocky planet was formed. It is one of the eight planets, and is third in distance from the Sun.
- Primordial Earth
Initially, the Earth was a giant lifeless ball of fiery lava, too hot for liquid water to form. Finally, after 800 million years, our home planet cooled enough, enabling liquid water to form. Everywhere rain began to fall, that filled the lower portions of the Earth with water. This helped in forming lakes, oceans and rivers.
Still, there was no life. No fishes to fill these oceans, no plants to cover the rocky surface. Earth was just a barren wet rock, orbiting the Sun.
The Earth's atmosphere now contained a mix of very poisonous gases like carbon monoxide, carbon dioxide, nitrogen, hydrogen sulphide, methane, and cyanide. Breathing this air would cause death to most of present life forms.
- Origin of Life on Earth
What forces changed this barren land into a beautiful Eden of life that it is today?
Earth's ancient lifeless oceans, were filled with the chemicals needed for life. These chemicals were not alive, but they were there sloshing around. They call these chemicals “primordial soup” which mainly contained amino acids, proteins, lipids, and other basic components that are commonly found in life forms today
It is believed that life began in pools of water called tidal pools on the shores of these ancient oceans. These shallow pools were full of this “life soup”. Ingredients of life splashed around in these pools, possibly helped by lightning strikes, they formed the first living cells.
- Unit of Life
A cell is the basic unit of life. They are tiny entities of organelles (a specialized subunit within cell), needed for the cell to survive. A cell can eat, move around, and reproduce. These cells took the chemicals of life found in the soup and put them together inside protective sacks. These first cells were very simple and because there was little or no oxygen available, they probably did not need it to survive.
As strange as it may seem first cellular life forms on Earth probably ate the same soup that they formed in. It contained plenty of proteins, amino acids, and lipids. The first cells were probably all consumers, the ancestors of animals.
- Origin of Life in Water
Life in the ancient sea originated with a completely new cell structure: one that had a cell membrane or wall (or both) that enclosed a central nucleus. Today we call this a eukaryotic cell. These new cells could now join together to do specialized tasks, the kind of specialization needed to make the tissues of plants and animals.
Now species could exist, that can respond to the diversity of their watery environments. Some would live on the bottom sediments, burrowing with tube-shaped bodies or walking with many tiny legs. Others would live in the ocean column, developing fins for effective swimming.
- Life in the Oceans
It is believed that life first evolved in the oceans in the form of simple unicellular organisms. Today the complexity of life in the sea is more than any other biome. Variety of sea organisms ranges from jellyfish to coral to whales.
Plankton – microscopic plants and animals are major food source for many marine creatures. The evolution of heterotrophism (those that can't make their own food) in invertebrates is another important advancement in the evolution of life. Heterotrophs feed off other things to get their energy. Plants are autotrophic, means they make their own food. Being heterotrophic is one of the main characteristics of being an animal.
- Basis of Life
The first important advancement was the development of cells that use oxygen.
The first cells could not use oxygen because there was not enough of it in the air. However, as these first cells carried out the business of living, they released oxygen into the atmosphere. Over a very long period of time, our atmosphere changed from a poisonous and deadly mix of gases to the atmosphere we know and live today.
As the atmosphere changed, so did life. Cells evolved, which could use oxygen to carry out their bodily functions. Because oxygen is a much more efficient gas, this paved the way to the evolution of larger, faster, and more complex cellular life forms.
- Multi-cellular Life forms
Over millions of years, food supplies began to dwindle. As a result, new types of cells had to form. These cells were called producers. Producers evolved the ability to actually create their own food, using the chemicals around them and the energy from the Sun. These producers would be ancestors to the plants.
The next major evolutionary advance was the development of multi-cellular life forms. Life was no longer limited to just one cell. Creatures began to arise that were made up of many cells ranging from two to billions in number. These cells began to specialize in different jobs, some acting as -- hearts, eyes, brains, allowing life to become very complex.
- Concept of Species
Scientists often classify living things into different kinds of groups. One classification of living things that we might sometimes hear about is “species.” Some scientists today define “a species” as a group of living things that are able to breed and produce offspring who can also breed.
Other scientists classify species in different ways, such as according to their genetic make-up. “Genetic make-up” basically refers to the characteristics that were inherited from its parents. Scientists also say that living things that have certain inherited genetic qualities in common are part of the same species!
- A Miraculous Advancement
Life started as a simple soupy mixture of chemicals and then on its own grew to form diverse life forms. It is evident that something directed the process of how an animal would look like. For instance, ears would be on the sides of an animal's head, eyes in front, and a nose in the very middle. Often, several ecological factors like availability of food, predators, surrounding habitat determines external appearance of a life form.
Biologists believe “Natural Selection” directed the process of Evolution of Life. This law says -- strongest life forms live to reproduce, while those that is weaker die. This phenomenon is often referred to as survival of the fittest.
- An Explosion of Marine Life
Consequently, an array of marine animals diversified after the development of multi-cellular organisms. This led to the evolution of Marine invertebrates, or animals that lack a backbone. They comprise many different groups such as sponges, jellyfish, corals, clams, crabs, lobsters, marine worms and sea stars. To make up for the lack of backbone, these animals have exoskeleton.
Ocean water was warm and teeming with life. At the edge of land and water, heaved great masses of algae. This helped first plants to move from water to land.
A diverse group of primitive jawless fish appeared over 500 million years ago in the ancient seas. However, jawless fish are today represented only by lampreys and hagfish.
- Metropolis under the Ocean
Corals are ancient animal colonies which evolved more than 500 million years ago! They are immobile life forms with hundreds and thousands of individual “polyps” forming huge colonies. The entire colony with associated marine life is generally referred to as ‘Coral Reef.’
Coral reefs are home to over 4000 species of fish, hundreds of coral varieties including innumerable marine plants and animals. Approximately a quarter of the total marine life is found in the coral reefs. ‘Corals’ includes many species like whip corals, black corals, soft corals etc. The greatest diversity of marine fishes can be found in the tropical coral reefs.
- Golden Age of Fishes
Diversification of fishes occurred during the Devonian period (about 420 million years ago). First fishes were small, jawless and finless. Over a period of time, some species of fish evolved jaws. The Devonian period saw the development of sturdy fins in various fishes. These increased efficiency of swimming and hunting. Soon most of the primitive fishes were displaced by more advance jawed and finned fishes.
Bony fishes have ruled earth's waters since Devonian period. By this time, life was well underway in its colonization of the land. Species had begun to branch out into both land and water habitats. However, Devonian Period ended with a mass extinction that resulted in a great loss of aquatic life.
- Invasion of the Land
Amphibians are the evolutionary step that happened when animals left the oceans and lakes and came on to the land. Some fish (lungfish) can survive out of the water for a while, but amphibians went further, by using their skin to absorb oxygen from the air. This allowed them to conquer terrestrial habitats.
Amphibians needed water in their early stages of development. One of the first amphibians was Ichthyostega, which lived during the late Devonian. Ichthyostega had four strong limbs and its head was clearly separated from its body by a neck. Its strong backbone and ribcage helped it to support the weight on land.
- Dinosaur Reproduction
Very little is known about dinosaur courtship, rivalry, pairing and mating. Dinosaurs’ eggs were round or elongated and had hard, brittle shells. Internally, these eggs were similar to those of reptiles, birds and primitive mammals; they contained a membrane that kept the embryo moist. Some Dinosaurs cared for their eggs; others simply laid and abandoned them.
Fossils of Dinosaurs' burrows and nests can reveal a lot about their behaviour. Nests vary from simple pits dug into the earth or sand to more complicated ones constructed with mud rims. Nests and the clutches of eggs reveal information about the dinosaur's nurturing behaviour.
- Tyrannosaurus rex
Tyrannosaurus rex was a huge meat-eating Dinosaur that lived during the late Cretaceous period about 85 million to 65 million years ago. It lived in a humid, semi-tropical environment, in open forests with rivers nearby and in coastal areas having forested swamps. At that time, seasons were mild.
Tyrannosaurus rex was a fierce predator that walked on two powerful legs. This meat-eater had a huge head with large, pointed, replaceable teeth and well-developed jaw muscles. It had tiny arms, each with two fingers. Each bird-like foot had three large toes, all equipped with claws (plus a little dewclaw on a tiny, vestigial fourth toe). It had a slim, stiff, pointed tail that provided balance and allowed quick turns while running. Tyrannosaurus rex's neck was short and muscular. Its body was solidly built but its bones were hollow.
Styracosaurus was a Dinosaur that walked on four short legs. This large plant-eater had a six-spiked frill projecting from the back of its skull. It also had an upward-pointing horn on its nose, and two small horns above its eyes. These spikes and the horn probably provided protection from predators, and were possibly used in mating rituals and rivalry.
It had a short, thick, pointed tail, a large, bulky body, a large skull and a beak. Styracosaurus hatched from egg was about 18 feet long, 6 feet tall, and weighed up to 3 tons. It lived in the late Cretaceous period, about 77-70 million years ago. It was among the last of the Dinosaur species to evolve before their extinction which took place about 65 million years ago.
Living near the end of the Dinosaur Age, Corythosaurus or Helmet Head was a large Hadrosaur. A “Hadrosaur “is a duck-billed Dinosaur. Like other Hadrosaurs, it had a toothless beak with rows of sharp teeth located in the back of its mouth.
The name Corythosaurus comes from its crest, which looks like a helmet worn by ancient soldiers.
This crest was probably used to make a loud horn noise. Air from the animal's nostrils was forced through the crest, making it vibrant loudly. Corythosaurus was named in 1914 by Barnum Brown. Since then, a large number of Corythosaurus fossils have been discovered throughout Western-North America.
This Late Jurassic Sauropod thrived in a time when the Earth's warm temperatures encouraged rapid plant growth. Diplodocus needed a lot of food to keep itself alive. Using rake-like teeth, this animal had an ability to strip an area of any vegetation very quickly, especially, considering that there is evidence that they travelled in herds.
Diplodocus' tail was about 45 feet (14m) long, which is one of the longest tails of any animal who have ever walked the Earth! Like most Sauropods, Diplodocus' nostrils were actually high up on its forehead instead of, at the end of its snout. A recently discovered fossil of a skin impression suggests that this animal had spines along its neck.
Triceratops is invariably one of the most famous of all the Dinosaurs. This large Ceratopsia or horned Dinosaur lived up until the very end of the Dinosaur age. That is around 65 million years ago.
Like other horned Dinosaurs, Triceratops had a large ridge that ran around the back of its skull. The use of this ridge is still debated today. Many believe that, it may have been used to make the animal look larger and more dangerous or perhaps it was used to anchor powerful jaw muscles to the skull. Triceratops probably used its powerful beak to crush food, such as vegetation.
Stegosaurus lived around 150 million years ago. Stegosaurus was the largest of the plated dinosaurs. It was just a little larger than a modern day elephant, and had a line of bony plates running down its backs. These plates were hollow and soft. For this reason, they were probably not used as protection.
Scientists believe that the hollow plates were used to help the animal regulate or control its temperature. Blood could flow into the bony plates, and either cool down or heat it up. This is one of the ways that such a large cold-blooded animal could survive. The Stegosaurus' tail-end had long sharp spikes that were no doubt used to protect it against large meat-eaters.
- The Era of Dinosaurs
The word Dinosaur comes from the Greek language and means ‘Terrible Lizard’. While Dinosaurs came into existence long time before humans, fossils and modern technology have helped us piece together what Dinosaurs may have looked like and even how they might have behaved.
Dinosaurs ruled the Earth for over 160 million years. Which date back, from the Triassic period around 230 million years ago, through the Jurassic period, and until the end of the Cretaceous period around 65 million years ago.
It is believed that Dinosaurs lived on the Earth until around 65 million years ago when a mass extinction occurred. Scientists believed that the event leading to the extinction may have been a massive asteroid impact or huge volcanic activity. Events such as these could have blocked out sunlight and significantly changed the Earth’s ecology.
- Conquering New Habitats
Some amphibians evolved into reptiles that were better adapted to the drier climate. Reptiles laid eggs with hard shells made of calcium, so they did not need water to lay their eggs in. Reptile babies were born with arms and legs, so water was not required to swim in like tadpoles. Reptiles also developed better hearts that gave them more energy than frogs. These changes were a big success. By 250 million years ago there were lots of reptiles all over the dry land, and swimming in shallow water as well.
About 240 million years ago, the land was all still together in one continent, but it began to get much warmer. New kinds of reptiles like turtles evolved. Snakes evolved about 150 million years ago from earlier lizards, later than most of the other reptiles. Around the same time, some of the smaller Dinosaurs evolved into birds.
- Modern Reptiles
Snakes, crocodiles, lizards, turtles and tortoises represent the modern day reptiles that outlived the mighty Dinosaurs. Reptiles also have scales to keep in moisture and help avoid skin damage, though the scales are sometimes too small to be seen. Living on land means limited access to drinking water, so reptiles' kidneys are adapted. They conserve water by producing less urine in more concentrated forms.
For cold-blooded creatures on land, survival requires more than just physical changes. Since a reptile's temperature depends on its surroundings, it basks on rocks to warm its blood for hunting. Not all reptiles have legs now, but they all needed them to become land-dwelling creatures. Though scientists knew that snakes once had legs, they could not determine whether they lost it before or after migrating to land.
Many scientists believe that the group Aves or the birds, such as raptors evolved from Dinosaurs. Archaeopteryx is regarded as the ancestor of all modern birds. For now, Archaeopteryx is credited as being the earliest known true bird. Yet, this strange animal had many Dinosaur-like features.
Archaeopteryx had feathers, beak, and feet like those of modern birds. But it also had fingers, claws, and teeth like many of the Dinosaurs. Archaeopteryx could fly, but not very well. It probably flew like a modern day peacock, running a lot, and only flying short distances.
- Winged Wonders of Evolution
Birds probably evolved from meat-eating (Theropod) Dinosaurs during the Mesozoic Era. Birds are warm-blooded vertebrate animals (can regulate their body temperature in relation to the surrounding environment). They have wings, feathers, a beak, no teeth, a skeleton in which many bones are fused together or are absent, and an extremely efficient one-way breathing system. Flying birds have strong hollow bones and powerful flight muscles.
Most birds can fly. Flying birds' wings are shaped to provide lift, allowing them to fly. These light-weight animals have adapted to their environment by flying. This makes them efficient hunters, lets them escape from hungry predators (like cats), and takes them away from harsh weather.
- Kingdom of Birds
Since the catastrophe that wiped out the Dinosaurs - birds have taken total command of the skies. For a time, when the early mammals were still quite small, birds effectively ruled the planet. Huge flightless "terror-birds" stalked the land. Mighty vultures cruised the skies. One had a wingspan of over twenty feet - bigger then that of the Andean Condor, and probably the biggest flying bird that has ever existed.
The power of flight gave birds the edge over most other creatures. They could travel farther and wider in search of food, and live where no other creature could go. Millions of years of evolution have adapted each bird species to fit into its own little niche. It also pre-programmed it to feed, to migrate, to nest and breed in its own particular place and manner. Birds have adapted so well that they are one of the most successful creatures on earth.
- Primitive Mammals
Mammals have existed for the past 200 million years. According to fossil evidence, they evolved from a mammal like reptile group. These reptile ancestors were small, but active carnivores. They were equipped with several specialized types of teeth. Their limbs were positioned more directly under the trunk as opposed to spreading out to the sides
The earliest known mammals were tiny shrew-size creatures that lived in the shadows of the Dinosaurs about 210 million years ago. When Dinosaurs became extinct some 65 million years ago, mammals got the most important evolutionary opportunity they would ever have. With dinosaurs gone, mammals could exploit the planet's resources themselves. Within a few million years there was an explosion in mammalian diversity.
- A Prehistoric Cat
Sabre-toothed cat was one of the three species of cats belonging to the genus Smilodon. It was, only, distantly related to the modern lions, tigers and cheetahs. The huge curving canines are a characteristic feature of this species. Strangely enough, these monstrous teeth were surprisingly fragile and easily broken.
Despite their imposing bulk, Saber-tooth Tigers (even hunting in packs) would not have been capable of taking down large prey with massive bodies. Paleontologists believe that Smilodon pounced on its prey from the low branches of trees, dug its "Sabers" into the neck of its unfortunate victim, and then withdrew to a safe distance living the animal bleed to death. The Saber-tooth Tiger went extinct 10,000 years ago. It was probably, because of combination of climate change and the disappearance of its large-sized and slow-witted prey.
- Rise of the Mammals
Different groups of mammals became widespread throughout the world after the extermination of Dinosaurs. They were not only diversifying on land but also, some of them were returning back to the sea. The present day whales, dolphins and seals are examples of mammals which re-colonised the ocean habitat.
The trend towards a cooler global climate that occurred during the Oligocene epoch (33.7 - 23.8 million years ago) saw the appearance of the grasses. This change in vegetation drove the evolution of plant-eating animals such as modern horses, which had teeth that could deal with the high silica content of the grasses. The cooling climate trend also affected the oceans with a decline in the number of marine plankton and invertebrates.
- Evolutionary Adaptations of Mammals
There are about 4000 different kinds of living mammals in the world. Mammals have successfully adapted to and colonized a wide variety of habitats including land, air, and water. Their widespread success is largely due to their ability to regulate their own body temperature. But mammals have also evolved many other unique adaptations to help them succeed in numerous environments.
Mammals are the only animals with true hair. Mammals are vertebrates -which mean that they all have backbones (spines). They are also the only animals with a placenta for nourishing the embryo. Milk is secreted from the mammary glands of the female to feed the new born young.
- Biodiversity through Evolution
Charles Darwin postulated that individual species were the result of the process called Natural Selection - by which the healthiest, strongest, and most well-adapted organisms flourished and went on to reproduce.
Darwin further theorized that the diversity of species could be attributed to the adaptations of organisms to environmental factors. These adaptations are based on mutations -- which are random genetic changes that are passed on to offspring. Some mutations cause harm to the organism; other mutations result in changes that are beneficial to the survival of the organism in that particular environment. Organisms with these novel features out-compete other species members, or survive where others perish. Over time, the surviving organisms reproduce and perpetuate these new characteristics.
The first primate like creatures evolved by the end of the Mesozoic era around 65 million years ago from the group of mammals which were similar in form to squirrels or tree shrews. They probably adapted to warm, moist climates and living on trees (arboreal in nature).
Many species of monkey evolved ranging in size from that of fat squirrels to a large cat, and they probably fed on fruit and seeds in the forests. Monkeys had fewer teeth, less pronounced snouts, larger brains and more forward looking eyes than their ancestors Approximately six million years ago the early hominids, later to become Homo sapiens, diverged from the chimpanzees.
- The Early Humans
Around 3 million years ago, the higher primates, including apes and early man first appeared. Human-like hominids could stand upright while apes could not do so. Their hands were different too. Ape hands were made for climbing and clinging. Early man's hands were jointed differently, which allowed them to not only use tools, but also to make tools.
No one knows if these very early human-like people actually made tools, but remains of polished bones found in South Africa, suggests that they might have made simple digging tools from bone! Their diet was mostly vegetarian, along with some meat, probably obtained by scavenging.
- The Stone Age
This was the beginning of the Stone Age, and the dawn of early man. This period of time is called the Stone Age because these very early men created tools made of stone. The Stone Age ran from about 2 million years ago to about 10,000 years ago, which was the end of the last Ice Age. As far as we know, true humans first appeared in Africa.
This group of early humans were credited with inventing stone tools to help live more comfortably, and to better protect themselves against the many carnivore (meat eating) animals. Although this group made stone tools and weapons, these weapons were still pretty basic. They hunted game and also scavenged fat-rich marrow from bones. They were always on the move, in search of food.
- The Art of Making Fire
When early man first succeeded in making fire, he was probably a bit startled when he saw what he had created, little knowing that the invention of fire would change life dramatically! Most animals were afraid of fire, so a noisy campfire gave protection to the group or tribe. They are also started eating cooked meat using fire as opposed to raw meat.
Because of their fire making skills, a nightly campfire became a possibility and a routine. What was once created for comfort and safety was now transformed to a social occasion. People collected around the fire each night to share stories of the day's hunt and activities, to laugh, and to relax.
- Chenchu Tribes
The Chenchus are an aboriginal tribe of the central hill ranges of Andhra Pradesh. Considerable numbers of this tribe make their living in the dense forests of Nallamala. They specialise in collecting forest products for sale to non-tribal people.
The Chenchus are referred to as one of the Primitive Tribal Groups that are still dependant on forests and do not cultivate land but hunt for a living. They are dark complexioned and mostly short and lean in physical appearance. But they have very good stamina for trekking great distances in the forest. The male members carry bow and arrow for self-protection and for killing small game.
- Life in a Forest
Traditionally, Chenchus followed a hunter-gatherer life style. Typical Chenchu family belongings include bows and arrows, a knife, an axe, a digging stick, some pots and baskets. They usually own a thatched hut in one of the small settlements where they live during the monsoon rains and in the cold weather. The huts are small and circular with about 10 feet diameter made of bamboo or thatch.
But in the hot season communities split up and individual family groups camp in the open, under overhanging rocks or in temporary leaf-shelters. A basic family group of Chenchu comprises man, his wife, and their children. They also subsist on tubers, edible roots and seeds. Over the years, there has been a change in the life style and food habits of Chenchus.
- Modern Man
The species that all living human beings on this planet belong to is Homo sapiens. During a time of dramatic climate change about 200,000 years ago, Homo sapiens (modern humans) evolved in Africa. Like other early humans that were living at this time, they gathered and hunted food, and evolved behaviours that helped them respond to the challenges of survival in unstable environments.
Anatomically, modern humans can generally be characterized by the lighter build of their skeletons compared to earlier humans. Modern humans have very large brains, which vary in size from population to population and between males and females. Housing this big brain involved the reorganization of the skull. Our jaws are also less heavily developed, with smaller teeth.
- The Journey of Life
From very simple cells, to multi-cellular human beings, life had a very long way to go. A number of very important and astounding advances in evolution, allowed life to become what it is today.
Evolution continues even today. Guided by survival of the fittest, life forms are continuing to change and evolve constantly. The plants and animals we know today will be very different in the future. Who knows what creatures will evolve in the coming years? Who knows how humans will evolve? Even our own descendants may look very different millions of years from now.