Cambrian Period: Explosion of Life on Earth | Causes & Consequences
From the beginning of time, human beings have wondered how the Earth came into existence. Different religions have different versions, while scientists too give many different explanations. Scientists claim that a vast, dark, very hot cloud of dust swirled around a newly formed sun.
Gradually, the cloud cooled, and the gas began to condense into billions of droplets. Slowly, these droplets were pulled together into clumps by their own gravity-and they carried on clumping until all the planets, including the Earth, were formed. In short, scientists and researchers have been arguing for centuries about how the Earth was formed, and the debate still continues.
The Cambrian Period lasted for nearly 53 million years, from about 543 million years ago, until 490 million years ago. The continents were still forming but were mostly barren rocks. The land had no plant or animal life on it yet. During the Cambrian Period, there was an explosion of life forms. Most of these were in the water.
Many animals with no backbones lived in the shallow seas. The most plentiful species during this period were trilobites. The species got its name from the three lobes in the hard skin. The trilobite was also one of the first animals to have eyesight. There were plenty of other species living during the Cambrian Period also. Molluscs, worms, sponges, and echinoderms filled the Cambrian seas.
The plants of the Cambrian were mostly simple, one-celled algae. The Cambrian period ended in mass extinction. Advancing glaciers would have lowered the temperature of the shallow seas where so many species lived. Changes in the temperature and the amount of oxygen in the water would have meant the end for any species that could not adapt.
Explosion of Life
The Cambrian Period marks an important point in the history of life on Earth. It is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the ‘Cambrian Explosion’, because of the relatively short time over which many life forms appeared. Many reasons have been suggested for this explosion. The first is that the increase in oxygen levels in the atmosphere led to the evolution of more complex body structures. Moreover, many species became extinct at the end of the Vendian Period, and this allowed new life forms to develop. It is also thought that a change in the ocean chemistry made possible the development of hard body parts such as teeth and skeletons. Animals could now swim, burrow, defend themselves, hide, and hunt. However, the sea was still the center of activity.
Evolutionary Findings from the Cambrian Period
Scientists work by studying the evidence collected, looking for new evidence by questioning existing theories, and trying to develop better ones. Traditional beliefs are a matter of faith. They are not open to question or to change, while scientific theories are. Scientific theories can be tested by using them to make predictions, and then checking whether these predictions come true. Some scientific theories include the theory of evolution, the theory of relativity, the atomic theory, and the quantum theory. All of these theories are well documented, and proven beyond a reasonable doubt. Yet, scientists continue to tinker with them in an attempt to make them more elegant and concise or to make them more all-encompassing.
The Cambrian explosion is a brief time when most major groups of animals that have bilateral symmetry first appear in the fossil record. Do you know what a bilateral animal is? It is one whose body has two mirror-image halves. Modern examples are lobsters, people, dogs, and butterflies. The event is referred to as an ‘explosion,’ because a rich diversity of species appeared in a relatively short amount of time. There is growing evidence that these different groups had a common ancestor that lived during the Cambrian Period. Evidence is growing to support this theory, at least from the fossils that date back to this period. After the Cambrian Period, very few additional animal phyla, or large animal categories, a rose.
Metazoans were the first multi-cellular animals. They could move, respond to their environment, and feed on other organisms. They developed organs, a nervous system, sensory organs, and a brain which led to the development of intelligence. The earliest forms were flat-bodied, like today’s flatworms. Direct fossils of metazoans from later periods have been found. These are fossils of animals that lived in the sea and the seabed, 680 to 570 million years ago. They bear some resemblance to the bodies of some of today’s invertebrates, including some types of jellyfish. These fossils are amongst the earliest discovered of distinct forms of animal life.
20 Mindboggling Fun Facts about Heart for Kids
Fun Facts about Heart
The heart is the hollow muscular organ located behind the sternum and between the lungs; its rhythmic contractions move the blood through the body. In all humans, other mammals, and birds, the heart has 4 chambers while in fishes it is divided into two chambers.
Did you know that heart-related diseases or CVD account for 32% of all human deaths around the globe as of 2015? Isn’t that scary? Here is a list of 20 Amazing Fun Facts about Heart, check it out!
#1 Xenographic transplants involve taking an organ from an animal and using it in a human being – a chimpanzee heart was transplanted into a man in Mississippi, the USA in 1964, but the patient died two hours later.
#2 Your right lung is larger than your left – this is because the left lung needs to make room for your heart. Did you know Your heart beats about 35 million times a year?
#3 The pressure created by your heart can squirt blood almost ten meters.
#4 The blue whale has the slowest heartbeat of any animal – it only beats four to eight times a minute.
#5 The heart is the only muscle that doesn’t take its signal from the nervous system – it has its own stimulator in the right atrium.
#6 The larvae of the pork tapeworm, hatched from eggs eaten in infected pork, can travel around the body and live in the brain, eyes, heart, or muscles.
#7 A giraffe has special valves in its arteries so that its blood can reach up to its head. Without them, it would need a heart as big as its whole body!
#8 About 70 milliliters (around 2.5 fluid ounces) of blood are spurted out of your heart with each beat.
#9 Your heart pumps around 182 million liters (48 million gallons) of blood in your lifetime – with an endless supply of blood, it could fill a swimming pool in less than a month!
#10 Nuttall’s poorwill is an American bird that hibernates in the winter, hiding in a crack in a rock. During this time, it uses only a thirtieth of the energy it uses in the summer and its heartbeat becomes so faint that it can’t be felt.
#11 When you sneeze, all your body functions stop – even your heart stops beating. A very long sneezing fit can cause a heart attack.
#12 Newts can re-grow body parts that are lost or damaged, including legs, eyes, and even hearts. Scientists who have studied how they do this think they might be able to persuade human bodies to do the same.
#13 In Vietnam, cobra hearts are a common snack. They can be eaten raw, even still beating, with a small glass of cobra blood or dropped into a glass of rice wine. The kidney is often included as an extra titbit.
#14 The Scottish dish haggis is made by cutting up the heart, lungs, liver, and small intestine of a calf or sheep and cooking it with suet, oatmeal, onions, and herbs in the animal’s stomach.
#15 During heart surgery in 1970, a patient with hemophilia (an inherited condition which stops the blood clotting) needed 1,080 liters of blood – nearly 15 baths full – as he kept bleeding.
#16 The poet Shelley drowned off the coast of Italy in 1822. His body was washed up, half-eaten by fish, and cremated on the beach by his friends. One of them cut his heart from the burnt body and gave it to Shelley’s wife who kept it all her life.
#17 The glass frog is lime green but has a completely transparent stomach. It’s possible to see the blood vessels, the heart, and even check whether it’s eaten recently or might like a snack.
#18 People who killed themselves used to be buried at a crossroads with a stake through their heart. It was thought that they couldn’t go to heaven, and the cross-roads would confuse their ghost so that it couldn’t find the way home to haunt anyone.
#19 A robotic caterpillar controlled by a joystick can be inserted through a small hole in the chest, and crawl over a person’s heart to inject drugs or install implants to heal any damage. Is it nanotechnology?
#20 Apart from the heart, an Egyptian mummy doesn’t have any internal organs left inside the body. The others were removed and put into separate canopic jars that were buried with it. You can continue reading 10 More interesting facts about the Human Digestive System.
Dinosaurs – Facts about the Ruling Reptiles & Their Types
Dinosaurs fossils were probably discovered by the ancient Chinese, Romans, and Greeks. However, no one really recognized them as belonging to an extinct animal. Much later in 1676, a huge thigh bone was found in England by Reverend Plot.
It was thought that the bone belonged to a ‘giant’ but was probably from a dinosaur. The first dinosaur to be described scientifically was Megalosaurus, named in 1824, by William Buckland.
The name ‘dinosaur’ which means ‘terrible lizard,’ was actually coined by Richard Owen. In 1838, William Parker Foulke found the first nearly complete dinosaur fossil remains in New Jersey, USA. Since Buckland’s original discovery in 1819, approximately 330 different dinosaur genera have been discovered thus far.
The Ruling Reptiles
The Jurassic Period started around 205 million years ago and is known as the time when dinosaurs, who were reptiles, ruled the Earth. Dinosaurs were now much larger, which clearly put them at the top of the food chain.
Some of the largest dinosaurs of the Jurassic age were the herbivore plant-eating sauropods. Thanks to the abundant plant life, massive herbivores such as the brachiosaurus, diplodocus, and apatosaurus had no shortage of food.
The fiercest among the carnivorous dinosaurs were extremely large theropods like the allosaurus and the ceratosaurus. The allosaurus was probably the top Jurassic predator of its time, and with the largest specimen coming in at a length of over 9 meters and its prey was most likely the large herbivores such as the sauropods.
Flying reptiles like the pterosaurs were still the dominant air species. It was the first feathered flying species, and clearly an evolutionary step towards the bird species.
Marine reptiles consisted mainly of the plesiosaurs, ichthyosaurs, large marine crocodiles, variations of modern-day sharks, as well as cephalopods which are relatives of today’s squid and octopus species.
Different Types of Dinosaurs
There were many different kinds of dinosaurs. The smallest types were about the size of a chicken, and the largest was over 100 feet, or 30 meters long.
- Some ate only meat and were known as ‘carnivores’.
- Some ate only plants and were herbivores.
- Others ate both plants and meats and were ‘omnivores’.
Herbivorous dinosaurs were usually larger in size and had longer necks than the others as they evolved to scare carnivorous dinosaurs who hunted them for food. They usually lived in herds and had short and blunt teeth for chewing on plants. They probably swallowed stones to aid them in their digestion.
Carnivorous dinosaurs were large in size, and they usually walked on their hind limbs. They had long and sharp teeth for killing their prey and ripping their flesh for food. Omnivorous dinosaurs were not as large as carnivorous dinosaurs. They usually walked on their hind limbs, but they did not have specific kinds of teeth as they consumed plants, animals, and even eggs.
They are also classified as being lizard-hipped or bird-hipped. Some common dinosaurs are the Acrocanthosaurus, tyrannosaurus rex, spinosaurus, brachiosaurus, and diplodocus. Till now, more than 700 different species of dinosaurs have been identified.
Popular evolution theories before Charles Darwin
Early scientists were not interested in any theories of evolution or not even aware of such concepts. At first, they were even reluctant to accept the idea that some animals had become extinct. According to the Bible, even when a great flood covered the Earth, Noah had managed to save a male and female of all species to ensure that no animal would become extinct. When the first fossils of unknown animals were discovered, it was believed that these animals still existed in some unexplored regions of the Earth.
However, the discovery of fossils of giant animals like the mastodon shook this belief, as it was unlikely that there were unexplored regions large enough to hide such animals. French scientists were the first to accept that these giant animals might have roamed the Earth thousands of years ago, and become extinct due to a variety of causes. Slowly, this idea came to be accepted worldwide. Scientists began their work on evolution theories, and Lamarck was first among them. Later among all these evolution theories, Theory of Evolution by Charles Darwin became popular and most accepted to date by the scientific community.
Jean Baptiste Lamarck
Jean Baptiste Lamarck was a French scientist who developed a theory of evolution at the beginning of the 19th century. His theory involved two ideas. The first was the law of use and disuse, which stated that a characteristic which is used more and more by an organism becomes bigger and stronger, and one that is not used, eventually disappears. The second law was the law of inheritance of acquired characteristics. It stated that any feature of an organism that is improved through use is passed to its offspring.
However, Lamarck’s theory cannot account for all the observations made about life on Earth. For instance, his theory would predict that all organisms gradually become complex, and simple organisms disappear. But we know that this is not the case, and those simple organisms still exist. So today, Lamarck’s theory of evolution is largely ignored.
Jean Baptiste Lamarck believed that all bodies had ‘subtle fluids’. These were weightless fluids pervading all space and bodies. Two good examples of eighteenth-century subtle fluids were electricity and heat. Lamarck believed that subtle fluids were responsible for both movement and change.
For example, he pointed out that snails have poor vision because feelers on their head acted as their eyes. According to him, the ancestors of snails did not have feelers. They groped about with their heads to find their way around. This groping sent subtle fluids to the front of the head, and the constant presence of moving subtle fluids eventually brought about the development of feelers, and these feelers were passed from generation to generation.
Charles Willson Peale
Charles Willson Peale founded a museum in Philadelphia, Pennsylvania, in 1786. It contained a collection of natural history specimens, portraits of admirable historical figures, and human artifacts from various countries. His purpose was to show the place of human beings as part of the animal kingdom. His most famous display, however, was the mastodon skeleton he obtained in 1801.
Measuring 3.35 meters high at the shoulder, and 4.5 meters from chin to rump, it was huge and strange and confusing. Was it a man or beast, an elephant, or some unknown animal? The fossil had been discovered in swampy ground and had been excavated with great difficulty. Man or beast, this ‘monstrous creature’, as it was called, would soon become celebrated as the unknown species or the ‘incognitum’.
For many years, scientists refused to accept that some animals had become extinct. When remains were found that were unlike anything living at the time, they argued that they were unusual examples of living creatures, or that animals known only from fossils must still survive in some unexplored part of the world.
It was only at the end of the 18th century that the great French paleontologist and anatomist Georges Cuvier was able to demonstrate convincingly that extinctions were real. Cuvier was convinced that plants and animals of all types were created for their particular roles and places in the world’s environment and that they were unchanging throughout their existence.
According to him, catastrophic events in the course of history had killed off all members of some species, and their fossils would no longer be seen in the rocks. Subsequently, his evolution theory suggests, the old species were replaced by new ones that repopulated Earth.
Cuvier had an almost uncanny ability to reconstruct animals from only fragments of fossil remains. With elegant studies of the anatomy of large mammals such as elephants, Cuvier showed that fossil mammoths differed from any such creatures presently living. His many examples of fossils telling the stories of animals that lived and then disappeared were taken as incontrovertible proof of extinctions.
Hugh Miller was a 19th-century geologist. He put forward the theory that there had been several successive creations, and that each had been destroyed by a catastrophe. According to him, the Bible dealt with only the last creation. Miller’s theory of evolution explained the presence of fossils as being the remains of animals from an earlier creation.
Louis Agassiz was a Professor of Zoology and Geology. He did landmark work on glacier activity and extinct fishes. He encouraged learning through direct observation of nature. Agassiz put forward the theory of a new catastrophe the Ice Age.
He believed that a sudden intense Ice Age gripped the Earth for ages, and wiped out all the existing animals and plants. His concept of the Great Ice Age brought him much fame, as he was able to present evidence in the field, especially the scratched surfaces of bedrock where rocks in the moving ice had gouged out deep marks.
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