The theory of evolution by Charles Darwin was sparked by his travels in South America especially but also was supported by his observations of plants and animals in England when he was writing his book. On aspect of evolution is the natural variety of types within a species, some of which are more adapted to the environment than others.

Evolution refers to the change in the structure of an organism with the passage of million of years.

Explanation:

Evolution is the change in the structure of an organism with the passage of million of years. Evolution occurs due to two reasons, first from genetically while the other from adaptation to the environmental conditions. In genetically, the change in structure of animal comes from their parents whereas changes occurs due to adaptation of an organism in order to survive in the harsh climatic condition of the environment.

i might be wrong but i think its a. let me know if i’m right and have a good rest of your day!

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.