Questions & Answers

Documented microfossils have been found that are as old as
(A) 2.5 billion years.
(B) 3.5 billion years.
(C) 1.5 billion years.
(D) 2.5 million years.

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Hint: Fossils have been visible and ordinary throughout most of natural history, and so documented human interaction with them goes back as far as recorded history, or earlier. The collection of fossils is known as the fossil record.

Complete step-by-step answer:
Palaeontology is defined as the study of the history of life on Earth as based on fossils. The fossils are the dead and preserved left over of plants, animals, fungi, bacteria, and single-celled living things that have been replaced by rock material or impressions of organisms preserved in rock.
Palaeontologists use fossil left over to understand different aspects of extinct and living organisms. Individual fossils may contain details about an organism's life and environment.
Though palaeontology came into existence around 1800, earlier thinkers had observed aspects of the fossil record. The ancient Greek philosopher Xenophanes (570-480 BC) gathered from fossil sea shells that some areas of land were once under water.
Fossils (Bauer, 1546) Fossils (L. fossils-dug up) are remains, traces and impressions of past organisms. They occur in sedimentary rocks, peat, amber, asphalt, lava and snow. Branch of biology that deals with the study of fossils is called palaeontology. Fossils provide direct evidence of evolution. They are often called written documents of evolution. Fossil record shows that different types of organisms appeared at different times. Many of them became Extinct later on but some continue to live in the same or modified form. Trilobites are paleozoic (500-600 million years) arthropods with rilobed dorsal plates, a pair of antennae and jointed appendages. Ammonites are spirally coiled shelled molluscs which appeared about 200 million years and underwent mass scale extinction along with Dinosaurs (eg Rajasaurus Fossil history of some animals like horse has been discovered.
Microfossils are defined as fossils that have size in the range of 0.001nm to 1nm.
The oldest microfossil that was found was of bacteria in Quebec, Canada ago 3.5 billion years.

Our required option is B that is 3.5 billion years.

Note: How birds arose from reptiles had also been found out with the discovery of fossil Archaeopteryx. Earlier to Archaeopteryx, feathers had already evolved in dromaeosaurs for protecting them from cold. In Archaeopteryx feathers connected to forelimbs were used for gliding and possibly flying. Archaeopteryx lived about 180 million years ago.