Evidences and Timeline of Evolution
பரிணாமத்தின் சான்றுகளும் கால வரிசையும்
Embryological support for evolution came from Ernst Haeckel — and it was disapproved by Karl Ernst von Baer. Students swap these two names every year.
The idea
Evidence that evolution has occurred comes from fossils, comparative anatomy, embryology and molecular biology. Fossils are remains of hard parts of life-forms found in rocks; rocks of different ages contain different life-forms, showing that organisms have changed over time. Embryological support was proposed by Ernst Haeckel, who noted features such as vestigial gill slits common to all vertebrate embryos, but Karl Ernst von Baer disapproved it, noting that embryos never pass through the adult stages of other animals. In the history of life, invertebrates were formed and active about 500 mya; jawless fish probably evolved around 350 mya; sea weeds and a few plants existed around 320 mya; reptiles dominated the earth about 200 mya; dinosaurs suddenly disappeared about 65 mya; and the first mammals were shrew-like.
Why it matters
Evolution happened over millions of years, so no one could watch it — scientists rely on independent lines of evidence that all point to the same history.
NEET lens
Two favourites: (1) Haeckel proposed embryological support; von Baer disapproved it. (2) Timeline matching — about 500 mya invertebrates, 350 mya jawless fish, 320 mya sea weeds and few plants, 200 mya reptiles dominate, 65 mya dinosaurs disappear. Fossil dating uses radioactive dating.
Clinical significance
Molecular evidence — similar proteins and genes across species — is why drugs and vaccines can be tested in animals before humans, and why insulin from pigs and cattle once worked in people.
Introduction
Evolution is supported by evidence from fossils, comparative anatomy and morphology, embryology and molecular biology, and by a timeline of how life-forms appeared on earth.
Core concept
Palaeontological evidence: fossils (hard parts in rocks); different-aged rock strata hold different life-forms; age by radioactive dating. Embryological evidence: proposed by Ernst Haeckel (e.g. vestigial gill slits in all vertebrate embryos including humans); disapproved by Karl Ernst von Baer — embryos never pass through the adult stages of other animals. Comparative anatomy: homologous organs (divergent evolution) and analogous organs (convergent evolution). Timeline (approx.): 500 mya — invertebrates formed and active; 350 mya — jawless fish; 320 mya — sea weeds and few plants; 200 mya — reptiles dominate; 65 mya — dinosaurs suddenly disappear; first mammals were shrew-like.
Go deeper
Fish with stout, strong fins could move on land and go back to water (about 350 mya) — the coelacanth, caught in 1938 in South Africa and thought extinct, belongs to the lobefins that evolved into the first amphibians.
From Class 10
Class 10 introduced fossils and homologous/analogous organs as evidence of evolution. NEET adds who proposed and who rejected embryological evidence, and the dates.