The presence of iron oxides in rocks, formed during a specific time period, can be used as evidence of oxygen in the atmosphere during that time period. question 18 options: true false

True

Explanation:

Iron oxides can only form naturally in the presence of oxygen as shown the formulae below:

2Fe(II) + O2 → 2FeO

4Fe(III) + 3O2 → 2Fe2O3

The presence of naturally occurring iron oxides can, therefore, be a significant indicator of the presence of oxygen in the atmosphere.

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.