Biology · Evolution · NEET
Single-celled organisms first, then multicellular life forms, then invertebrates (about 500 mya), jawless fish (about 350 mya), seaweeds and few plants (about 320 mya), amphibians (from lobefins), then reptiles, then dinosaurs, then birds and mammals. Remember the ORDER; NEET rarely needs every exact date.
By about 500 mya (million years ago) invertebrates were formed and became active. This is the number NEET asks most, so fix it: 500 mya = invertebrates. It came AFTER single cells became multicellular.
Fish came first. Jawless fish evolved around 350 mya. Later, fish with stout strong fins (lobefins) could move on land and go back to water; these evolved into the first amphibians. So the order is fish then amphibians, never the reverse.
About 65 mya the dinosaurs suddenly disappeared from Earth. NCERT says the true reason is not known (climate change, or some evolved into birds). After reptiles and dinosaurs declined, mammals took over the Earth.
The first mammals were like shrews (small, with small fossils). Mammals were viviparous (gave birth to live young) and protected the unborn young inside the mother's body, and were more intelligent at sensing danger. They rose after reptiles came down.
The 'brief account' is NCERT's story-style ordering of life forms with a few key mya values. The geological time scale is the formal chart of Eras and Periods (Palaeozoic, Mesozoic, Cenozoic) with exact age ranges. Same events, but the time scale is the organised table version. See the next concept page.
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
Try the real previous-year questions from this chapter — each with the answer and a full solution.
About 500 mya. By this time invertebrates were formed and became active. This is the most commonly tested date in this topic.
NCERT states the first organisms that invaded land were plants. They were already widespread on land when animals invaded land.
A Coelacanth is a lobefin fish caught in South Africa in 1938, once thought extinct. Lobefins (fish with strong fins that could move on land and return to water) evolved into the first amphibians about 350 mya.
Because of continental drift and lack of competition from other mammals. In South America, mammals were overridden by North American fauna when the continents joined, but Australia's marsupials survived in isolation.
Related but not the same. This 'brief account' is the story order with a few mya values; the geological time scale is the formal Era and Period table. Study both together for NEET.
