Biology · Evolution · NEET
Bigger mya = older. 'mya' means million years ago, so 500 mya is 500 million years back in time, which is much older than 65 mya. Many students flip this. Read the timeline from the biggest number (oldest life, like invertebrates at 500 mya) down to the smallest number (most recent event, like dinosaurs disappearing at 65 mya).
By 500 mya invertebrates were formed and active. Jawless fish probably evolved around 350 mya. Seaweeds and few plants existed around 320 mya. About 65 mya the dinosaurs suddenly disappeared from earth. These four numbers are the ones NEET matches in questions, so lock them exactly as written in NCERT.
After. Invertebrates were active around 500 mya, and jawless fish came later, around 350 mya. So the order in time is: invertebrates (500 mya) first, then jawless fish (350 mya). A common trap is to think fish are 'primitive' so they came first, but invertebrates like early sea animals appeared earlier.
NCERT says the first cellular forms of life appeared about 2000 mya. Single-celled forms slowly became multi-cellular. Fish with strong fins (lobefins, like the Coelacanth) evolved into the first amphibians that lived on both land and water; amphibians then evolved into reptiles. The exact numbers tested are the 500/350/320/65 set, but know 2000 mya for first cellular life.
Because 65 mya is the smallest mya value in this NCERT list, it is the most recent event. Even though dinosaurs feel 'ancient,' 65 million years is much closer to today than 500 million years. So in a chronology from oldest to youngest, the dinosaur extinction sits at the end of these four items.
Match List I with List II with respect to chronology of evolution of life forms. List-I: A. About 65 mya, B. About 500 mya, C. About 350 mya, D. About 320 mya. List-II: (I) Jawless fish probably evolved, (II) The dinosaurs suddenly disappeared from the earth, (III) Seaweeds and few plants probably existed, (IV) Invertebrates were formed and became active. Choose the correct answer.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is a timeline that places each major life form at a certain number of million years ago (mya), based on the ages of fossils found in different rock sediments. NCERT uses it to show when invertebrates, fish, plants, reptiles, dinosaurs and mammals appeared or disappeared.
First cellular life ~2000 mya, invertebrates ~500 mya, jawless fish ~350 mya, seaweeds and few plants ~320 mya, dinosaurs disappeared ~65 mya. The 500/350/320/65 set is the one NEET matches most often.
By radioactive dating. Fossils sit in dated rock sediments, and radioactive-dating of the rock tells us the geological period in which those life forms existed. This is part of the paleontological evidence for evolution.
NEET regularly sets match-the-column and correct-sequence questions using these exact mya values (for example, NEET 2026). If you memorise the four NCERT numbers and their order, these become quick, certain marks.
