EVERYDAY SCIENCE

Detailed explanation-1: -The first fossils of prokaryotic (bacterial) cells are known from 3.5 and 3.4 billion years ago. These bacteria were photosynthetic (although non-oxygen producing) so it is likely that simpler non-photosynthetic bacteria evolved prior to this (Schopf, 1987; Beukes, 2004).

Detailed explanation-2: -We now know that prokaryotes were likely the first forms of cellular life on Earth, and they existed for billions of years before plants and animals appeared. The Earth and its moon are dated at about 4.54 billion years in age.

Detailed explanation-3: -Some of the oldest cells on Earth are single-cell organisms called bacteria. Fossil records indicate that mounds of bacteria once covered young Earth. Some began making their own food using carbon dioxide in the atmosphere and energy they harvested from the sun.

Detailed explanation-4: -The eukaryotes developed at least 2.7 billion years ago, following some 1 to 1.5 billion years of prokaryotic evolution.

Detailed explanation-5: -Eukaryotes contain cells that have a volume of around 10, 000 times greater than the single cell of organisms known as prokaryotes, such as bacteria. Emerging as far back as four billion years ago, prokaryotes are the most ancient forms of life on Earth.