MODEL PAPER 3 — BIOLOGY STD 12 Science — Question

The evidence for organic evolution are as follow:
i. Fossils/Paleontology evidence: Fossils of earliest life are scanty and only of prokaryotes mostly. Eukaryotes developed later
оп.
ii. Disparity between fossils: Present-day organisms seem to be related to the fossils of the quaternary period but differ from those of the tertiary period. Fossils of the quaternary period are similarly related to the tertiary period but differ from the ones
of the Cretaceous period. These differences are due to changes in the form, structure, and habits of organisms due to evolution.
iii. Extinct organisms: Lots of organisms existed on earth for some time and then got extinct like dinosaurs, toothed birds, pteridosperms, giant horsetails, ancestors of man, etc. Extinction happened due to many factors. Some of the extinct forms have left their modified descendants (Man, modern-day Horse) while others have perished without leaving any descendants (Pteridosperm, Dinosaurs).
iv. Missing Links: These are transitional or intermediate forms between two groups of organisms which occur only in the fossil state. E.g., Seymouria, a missing link between amphibia and reptilia.
v. Plant vs Animal Fossils: Ancestral animals have left more fossils as compared to plants evidently due to the presence of slow decaying harder structures in their exoskeleton and endoskeleton.