The ultimate source of energy for starting the food chain is:

The correct answer is- Sun

Explanation:

The sun is the ultimate source of energy for starting the food chains because the energy from the sun is used by plants to make food and this food is consumed by herbivores and then the herbivores are consumed by a carnivore.

Therefore sun energy is required to make start a food chain and to run a food chain and without sun energy no food chain can occur because all living organism is dependent on solar energy directly or indirectly.  

Even in the ocean planktons and algae use sunlight to make food and start the food chain. Therefore the correct answer is Sun.

a time line cause it goes from 685 to 978

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.