Question

The oldest fossil record of blue- green algae is 2.9 billion years old. It is?
A. Stromatolites
B. Archaeopteryx
C. Archaeospheroides
D. Chlamydomonas

Answer 1

Hint: Cyanobacteria were traditionally described as algae and mentioned as 'Cyanophyta' or 'Blue chlorophyte’. Blue-green algae are literally sorts of bacteria referred to as Cyanobacteria. They normally look green and occasionally may turn bluish when scums are dying.

Complete answer:
Let's discuss the choice and find the right answer.
A. Stromatolites : They are described as laminated accretionary structures that have synoptic relief. Stromatolite-building communities include the oldest known fossils, dating back some 3.5 billion years when the environments of Earth were too hostile to support life as we all realize it today. Hence option A is wrong.
B. Archaeopteryx: A particularly major and still contentious discovery is archaeopteryx. It is found within the Jurassic Solnhofen Limestone of southern Germany, which is marked by rare but unexpectedly preserved fossils. Archaeopteryx is taken into account by many to be the primary bird, being of about 150 million years aged. Hence option B is wrong.
C. ArchaeoSpheroides :The oldest sort of life was discovered here, a bacterial micro fossil Archaeospheroides barbertonis and has been identified as being 3.2 billion years old. The oldest fossil record from India is of a blue chlorophyte which is 2.9 billion years old. It's Archaeo Spheroides. Hence option C is correct.
D. Chlamydomonas: Chlamydomonas could also be a genus of chlorophyte which contain about 325 species of all unicellular flagellates. It is found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". Chlamydomonas reinhardtii may be a unicellular green alga whose lineage separate from land plants over 1 billion years ago. Hence option D is wrong.
Hence option C: Archaeospheroides is the correct answer.

Note: However, one particular group of bacteria, the cyanobacteria or "blue-green algae," have left a fossil record that extends far back to the Precambrian. The oldest cyanobacteria-like fossils are practically 3.5 billion years old, amid the oldest fossils currently known.