WHAT IS THE EVOLUTION?

 Evolution is a process through which organisms evolve new characteristics. 

Simply it is the study of history of life on earth 🌎 .  

   In early stage it is consider that there are nothing  in the universe and after a big explosion in our universe our solar system is formed which include the earth, sun and the other planets.

In early stage there are no atmosphere in earth, hydrogen and helium like gasses release from molten mass and cover the earth surface. O2(oxygen) Combine with CH4(methane) and NH3(ammonia) to form   H20(water) and CO2(carbon dioxide).

 The universe was formed about 20BYA(billions year ago) and the age of earth is about 4.5 BY  and the life is about 4 BY.

The origin of life is consider as a unique event in the history of universe.  The first form of life was non cellular and the cellular form of life with a membranous envelope didn't originate till about 2000mya(million years ago),without any doubt they are autotrophs. 

Still it was disappear that how first form of life came until 

Oparin of Russia and Haldane of England propose that the first form of life was come from pre-existing nonliving molecules such RNA and PROTEIN etc. 

EVOLUTION IS A STOCHESTIC PROCESS THAT DEPENDS ON CHANCE EVENT IN NATURE AND CHANCE MUTATION IN ORGANISMS.

The most popular theory about evolution was given by CHARLS DARWIN which is Natural selection.

Natural selection based on some observations that are -

1.Natural resources are limited

2. Population size are stable except seasonal fluctuations 

3.members of the populations are vary in characteristics though they look superficially similar to each other.

4.most of the variations are inheritant. 

Darwin on his ship HMS Beagle recognize around the world and propose his theory about evolution.

The two key concepts of this theory was  1. BRANCHING DESCENT and 2.NATURAL SELECTION. 

The essence of Darwin theory about evolution is Natural selection.  According to Darwin the organisms more fitted in nature produce more progeny and naturally selected.

There must be a genetic basis to get selected and evolve.

The evolution is mainly two types 1. Divergent and 2.convergent 

Divergent evolution reflects common ancestory that include homologous types organs, which perform different functions but having common origin.

Some homologous organs are -

1.forelimbs of whale,bat,cheetah and humans.

2.vertibrates brain and heart.

3.thorn of bougainvillea and tendrils of cucurbita.

They all have common origin but have different functions.

On the other hand convergent evolution reflects different ancestory that include analogous organs, which perform same function but have different origin.

Examples of analogous organs are -

1.eye of octopus and mammals.

2.flippers of dolphin and penguins.

3.wings of butterfly and birds.

They all perform same function but have different origin.

 SOME PHENOMENONS RELATED TO EVOLUTION ---

1.ADAPTIVE RADIATION--Adaptive radiation  is a process of evolution of different species in a given geographical area that start from a point and radiates to other areas(habitats).

Darwin's finches (a type of birds) are one of the best example of Adaptive radiation besides Australian marsupials and Australian placental mammals etc. 

2.BIOLOGICAL EVOLUTION-- Biological evolution is, simply the evolution occurs by the natural selection. Biological evolution have started with the origin of the cellular form of life on earth with different metabolic capabilities. 

In biological evolution more fitted characters are selected by the nature. One must remember that fitness based on characteristics which are inheritant. 

3.INDUSTRIAL MELANISM--

An interesting observation of evolution comes from England. In 1850 before industrialization there are no polluted areas in England,so there are several white moths but after industrialization in 1920 there are mostly dark moths are present and white moth are disappear.

This was because of industrialization, before industrialization there was no polluted areas and white-winged moths are hide from predators by camouflage with lichens ( which are also white in colour) but as lichens don't grow in polluted areas, after industrialization white moths are not able to camouflage and don't survive due to predators. 

WHAT IS THE CAUSE OF EVOLUTIONS---

What is the origin of evolution and how does speciation occur? Though Gregor Johann Mendel propose an idea about evolution talking on factors(now genes). In the first decade of twentieth century, Hugo de Varies propose the mutation(large difference arising suddenly in a population) theory of evolution based on his work on evening primerose . He said that it is the mutation that cause evolution not the minor  heritable variations. Mutations are small and directionless.  It cause speciation hence known as saltation (single step large mutation).

The remained hard part of living organisms found in rock 🪨 represents fossil that indicates the extinct organisms as dinasoures.

A study of fossils in different sedimentary layers indicate the geological periods in which they are exists. Dynasours are suddenly dissappear 65MYA(million years ago).

HARDY-WEINBERG PRINCIPLE----

Hardy-weinberg principle tells us about the gene frequency of alleles in a given population in algebric form.

In H-W principle p and q represents the allelic frequencies of allele A and allele a of a diploma organism. According to this principle sum total of all allelic frequency of a population is 1. Hence p2 +2pq+ q2=1 or in binomial form (p+q)2=1. This principle introduce us to genetic equilibrium (constent gene pool or all the alleles and their genes in a population). When frequency measured differ from expected value the differences indicate the extent of evolutionary change. Five factors that known to effect H-W principle are 1. gene migration 2. genetic drift (gene migration occur by chance) 3.mutation 4.genetic recombination and 5. Natural selection. If gene migration happens multiple times it is consider as gene flow. If a part of a population by change in gene frequency turn into a new species then the original drift population become founders and the effects known as founder effect.