Answer:
Sun
Sun is the main source of energy on earth. About 40% light reach to the atmosphere some of which is filtered by ozone layers, water vapours and other gases. only 1% light is used in photosynthesis.
Photosynthesis
Producers contain chloroplast filled with chlorophyll molecules. when sunlight falls on leaves process of photosynthesis occurs which convert light energy into chemical energy in the form of glucose.
Respiration
Respiration occurs both in producers and consumers. in this process chemical energy (glucose) is converted into ATP, NADH and FADH2.
Decomposition
there are some organisms known as decompose s. they decompose dead bodies of plants and animals and convert complex molecules into simple nutrients with help of energy. in this way sun light energy is transferring in ecosystem in different forms.
Diagram
Answer: The correct answer is-
C.They replaced carbon dioxide with oxygen in the atmosphere.
Cyanobacteria ( also known as blue green algae) is a large phylum of bacteria that is capable of synthesizing its own food using carbon dioxide and water in the presence of sunlight ( photosynthesis).
They contain a green pigment called chlorophyll that absorbs energy from sunlight and helps in the formation of food ( glucose). They release oxygen as a byproduct in the atmosphere.
As these organisms utilize carbon dioxide ( that is present in the atmosphere) to give oxygen in return, therefore, they affected early atmosphere of Earth by replacing carbon dioxide with oxygen.
Thus, option C) is the right answer.