The microorganisms was unicellular and had a well - defined nucleus.
The three germ layers are the endoderm, the ectoderm, and the mesoderm. Cells in each germ layer differentiate into tissues and embryonic organs. The ectoderm gives rise to the nervous system and the epidermis, among other tissues. The mesoderm gives rise to the muscle cells and connective tissue in the body.
Answer:
D. marks transformation of nitrogen (N₂) from the atmosphere to ammonium (NH₄ plus) by bacteria.
Explanation:
The nitrogen cycle is a biogeochemical cycle which involves transformation of atmoshperic nitrogen into many chemical forms including nitrite (NO2), nitrates (NO3) and ammonium (NH4).
The process of nitrogen cycle starts with the process of nitrogen fixation. In this process several nitrogen fixation bacteria such as cyno bacteria converts the atmospheric nitrogen into ammonium (NH4) in the soil. The resultant ammonium (NH4) can be directly used by plants or transform into nitrites or nitrates through nitrification process.
Hence, the correct option is D.
