Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age. Absolute dating is used to determine the precise age of a fossil by using radiometric dating to measure the decay of isotopes.

(a) Pennsylvanian
(b) Mississippian

(a) Age of fishes - Devonian period
(b) Age of invertebrates - Cambrian period

(a) Precambrian era
(b) Paleozoic era
(c) Mesozoic era
(d) Cenozoic era

Genetic drift can have major effects when the population is reduced in size. When a small group of population splits from the main population to form a new colony. It is called founder's effect.

Stabilizing selection
Directional selection
Disruptive selection

Gene Mutation, Chromosomal mutation, Genetic recombination, Natural selection, Reproductive isolation.

Mesozoic era is divided into three periods namely Triassic, Jurassic and Cretaceous.
Dominating Fauna: Reptiles and Dinosaurs
Dominating Flora: Conifers, Ferns and Ginkgon.

The original hard parts such as bones, teeth or shells are preserved as such in the earth's atmosphere. This is the most common method of fossilization.

It is the study of prehistoric life through fossils

Hardened faecal matter are termed coprolites and occurs as tiny pellets. Analysis of coprolites enables us to understand the nature of the diet, on which the prehistoric animals thrived.

They argued that external conditions stimulate the somatic cells to produce certain 'secretions' which reach the sex cells through the blood and bring about variations in the offspring.

A slight change occurs over time in conserved molecules such as DNA, RNA, and protein. They are often called as molecular clocks and serve as molecular evidence of evolution.

Ernst Von Haeckel propounded the "biogenetic law or theory of recapitulation" which states that the life history of an individual (ontogeny) briefly repeats or recapitulates the evolutionary history of the race (phylogeny). In other words "Ontogeny recapitulates Phylogeny".

Sudden appearance of vestigial organs in highly evolved organisms is called atavistic organs. Eg: presence of tail in a human baby is an atavistic organ.