Fundamentals of evolution
Earth, the only known planet which harbor life and it does so in great quantity. The total number of variety of animals and plants is astonishing. The estimated number of different species vary from six million to a hundred million. Wherever you look there is life even we are carrying more bacteria in our cell rather than our total cell. There are often a multitude of variation on a single pattern. For example, nearly ten thousand species of bird, 6495 species of mammal, the total number of bat species in the world is presently cited at more than 1300, 10793 reptile species, 7924 species of amphibian, nearly 34000 fish species, and snake almost 3400 species. 350 thousand beetle species, 315 hummingbird, not to mention 400 thousand different kinds of flowering plants, etc. The variety is astounding. Why should there be such a dazzling variety?
This is because of evolution. You may hear the word quite often but unfortunately very few of us understand the meaning. The theory of evolution was given by Charles Robert Darwin in 1859 in his book ‘On the Origin of Species by Means of Natural Selection’. Now it has become a fact because now we can prove that evolution is true. All the life forms on this planet are evolved from a common ancestor.
So how the common ancestor was originated? In recent years this answer is taking its shape scientifically. From the Miller-Urey experiment, we found that amino acids which are called the building blocks were produced in the primitive earth when NH3(ammonia), CH4(methane), H2O(water), and H2(hydrogen) was abundant.
A recent study in 2018 indicated that these amino acids can form a protein-like structure and they have self-replicating property. So it can be assumed that over time RNA and DNA evolved and thus the common ancestor or primitive life forms. This is not fully solid science but we will get an answer very soon.
Now another question arises how one life form changes to another form. For this, we have to know about DNA and RNA. DNA carries genetic information and determines the protein sequence but some other factors like the environment have a significant impact on the protein sequence. DNA sequence can be changed by UV rays, X-rays, replication errors, etc. Changes in DNA or genetic material is called a mutation. Some viruses use RNA as their genetic material and RNAs are more susceptible to mutation.
Some mutations can bring change to protein sequence though many mutations don’t have any impact. Some mutations may give an organism some help to survive and reproduce and some can cause extinction. This is the fundamental truth about evolution and nature selects the adaptable one.
Think about us and our closest cousin chimpanzees. We share nearly 98.6% DNA with them out still look very different. We have a bigger brain than chimps because of differences in a single gene. Chimps are more muscular than us and their jaws are very powerful. Because of that powerful jaws, they have smaller brains. We have a common ancestor approximately 6 to 7 million years ago which is found by DNA marker analysis and very accurate estimation. There were more than a dozen human species excluding us some of them thought to be extinct because of the activity of Homo sapiens -us.
Polar bears are the descendants of the Alaskan bears. Once one of them produced a cub with a white fur coat because of a mutation in the egg cell and gave the offspring a slight advantage over others for hunting and raising cubs. At a time a population of white fur coated bear was evolved and brown coated bears were diminished from the arctic.
The most amazing fire adaptation is that some species require fire for their seeds to sprout. Some plants, such as the lodgepole pine, Eucalyptus, and Banksia, have serotinous cones or fruits that are completely sealed with resin. Because of the random mutation or mutations, these plants were able to encapsulate the seed with resin, and eventually, that small adaptation helped to survive against fire.
The arctic woolly-bear caterpillars are unique in their combination of fascinating adaptations to the polar extremes. They spend nearly 90% of their life frozen and only about 5% feeding on the tundra during the month of June; the remainder is spent in summer “hibernation” inside protective cocoons. It can take 14 years to become an adult. If they don’t have the beneficial mutation to survive against the freezing temperature they could not survive this long. Some fish has an anti-freezing gene which helps them to survive against freezing without the gene they would become extinct.
Evolution can be easily understood by studying finches in the Galapagos. Their beak shapes are different based on the food habit. Those beaks are more adaptable to feed on particular food habit are selected by nature. If they were unable to adapt they could become extinct. In the present earth, we see only a fraction of life forms compared to the total species evolved over the entire time of evolution. Dinosaurs were mighty beasts but because of the asteroid impact, they could not adapt to the changing environment that’s why they are extinct now. But one of their descendants are still with us, birds. Now, this earth is dominated by mammals, after the extinction of dinosaurs, they benefited most. They fill the niches left by dinosaurs. Change in DNA occurs randomly and that change may give one individual a boost. After that sexual selection can be a reason for their success. At first, the changes occur randomly and the surroundings decide the fate.
Ichthyosaur and Dolphin look very similar but one is a reptile and another is a mammal. This type of change is called convergent evolution. All the living things use the same type of genetic material so this type of similarity is possible.
Humans are responsible for the extinction of various plants and animals because they could not adapt to the rapid changes caused by humans. Some plants and animals were selected for the benefit of humans and become very different from their ancestors. This is called artificial selection. Artificial selection is a very similar process like natural selection but in artificial selection, humans hold the ultimate power of changes. There was no dog before the agriculture revolution 10–12 thousand years ago. Humans selected some wolf as their companions and selected breeding based on favorable traits has produced the astounding varieties of dogs we see today.
If we humans can do this then without any doubt nature is doing this for a long time.
Each individual locked in its life long fight for survival. Many animals and plants go to extremes to give themselves a chance. And some times nature only selects the adaptable one to survive and reproduce.
No animals can change its genetic material nature writes it fates nowadays humans are writing the fates of other species. Evolution occurs because of the random changes in the genetic material and some changes may benefit an individual to produce a population.