Mutations occur in nature. It also occurs in pathogens. Some of these mutations caused adaptations to resist the attack of antibiotics.

(p + q)2 =p2+2pq+q2=1

Oparin-Haldane theory of chemical evolution states that life originated from pre-existing, nonliving organic molecules.
In 1953, S.L. Miller observed formation of amino acids from CH₄ ,H₂, NH₃ and water vapour at 800°C. It states that life originated from pre-existing non-living organic molecules (e.g., RNA, protein, etc.). When the meteorites were analysed, it was observed that presence of similar compounds was confirmed which conclude that similar process is' going on elsewhere in the space.

The increasing order of evolution in plants is Zosterophyllum-Ferns-Ginkgo-Gnetales.

Earth was supposed to have been formed about 4.5 billion years back in the solar system of our milky way galaxy. Its surface was covered with water vapour,
methane, carbon dioxide and ammonia released from molten mass and had no atmosphere. The lighter hydrogen gas cscaped from the surface while oxygen combined with ammonia and methane to form water, CO₂ and others substances.

The existence of analogous organs can be explained on the concept of evolution. These organs have developed in the course of evolution as adaptation of different organisms to a similar mode of life.

Tyrannosaurus rex was the largest of the dinosaurs.
(i) It was about 20-feet in height.
(ii) It had huge fearsome dagger-like teeth.

These are analogous organs, doing the same function.
Analogous organs are those organs, in different groups of organisms, which perform the same function, but are dissimilar in their basic structural plan and developmental origin. 

1. Ernst Haeckel proposed embryological support for organic evolution.
2. It was disapproved by Ernst Von Baer.
3. He noted that embryos never pass through the adult stage of other animals.

1. Brachiosaurus and Stegosaurus lived early in the history.
2. Tyrannosaurus and Triceratops lived later.

Origin of Universe:
The universe is about 20 billion years.
The Big Bang theory explains that the universe arose from a huge explosion (unimaginable in physical terms), of a very large entity.
As the universe expanded, the temperature decreased; hydrogen and helium were formed sometime later.
The gases condensed under gravitation and formed the galaxies of the present day universe.
Earth was supposed to have been formed about 4.5 billion years back.

Survival of the fittest means that those individuals which survive and reproduce successfully in their given environment or habitat, are called fit.
Such individuals produce more progeny (with more fit individuals), than the others who are less-adapted to survive and reproduce in that environment.

1. convergent evolution is the evolutionary process, where anatomically different structures in different groups of organisms evolve towards the same function, in similar habitats.
2. Such structures in different groups of organisms which perform similar function, but are anatomically different, are called analogous organs.
3. The wings of a butterfly and those of bird are anatomically different, but perform the same function (flying); hence they are said to be analogous organs.

1. Divergent evolution is the evolutionary process, where the same structure develops along different directions in different groups of organisms adaptions to different needs.
2. All the different structures evolved are homologous structures, as they all have a similar anatomical structure, though they perform different functions, e.g. the thorn of Bougainvillea and tendril of Cucurbita are homologous organs, as both of them are modified stems, which perform different functions.