People often wonder what is alive and what is not. Animals are multicellular, living organisms in the Kingdom Animalia. With few exceptions, all animals breathe air, eat organic matter, can move, reproduce sexually, and have sensory organs that are on their skin. Because an animal’s tissues are made up of billions of cells, it is impossible to determine whether something is alive or dead without dissecting the animal. The definition of life is ” Everywhere living things are present”.
One of the greatest examples of animal species being wiped out by a mass extinction event is the dinosaur age. dinosaurs were indeed widely hunted by early man and many species disappeared from the Earth at the same time. One of the biggest fossils found so far is the aforementioned T-Rex. Just as the massive asteroid that wiped out the dinosaurs is now considered a disaster for the earth, similar a extinction event may happen again some day. It is possible that future generations will be able to observe Earth-based animals through the use of satellites or remote-controlled vehicles.
There is a possibility that all nonavian mammals will become extinct during a mass extinction event, which is due to a collision with another large object or comet. Evidence of this will be found in carbonated shells of ancient oceans and seas. Evidence that animals reproduce differently than plants or even bacteria has been found in their fossilized tissues. Animals with a highly developed reproductive system, such as mammals such as humans, have a relatively short time before they expire, while the less developed animals tend to live longer because they have a higher rate of reproduction.
Some types of reptiles, including dinosaurs, were flightless. Many modern day reptiles have evolved into very complex and efficient creatures with complex nervous systems, eyeight, and complex muscles. Many amphibians (insects) are capable of breathing both under water and above water. Some types of insects such as dragonflies and aphids have wings and can fly, although not in the same way as birds.
The age of the earth’s oldest fossils is estimated to be about two million years ago, and the majority of these fossils are from dinosaurs. In addition, it is believed that reptiles and amphibians have also survived the last two million years since the mass extinction event. Most animals reproduce somewhat sexually, although asexual reproduction is more common in certain animals, such as ants and bees.
Since the beginning of agriculture, there have been natural cycles that have occurred that can result in extinctions of some species. Changes in atmospheric oxygen levels and changes in precipitation patterns over long periods can wipe out some types of mammals. Extinction events are natural, but can be prevented if careful planning is put into place and if people care for wild living organisms. Some scientists believe that human interference might be one of the leading causes of extinction of wild animals in our planet’s history.