The answer is 'Cambrian' explosion. This took place approximately 541 million years ago. 'Explosion' refers to the evolution of a large range of new major animal phyla. Scientists know this by the large number of diverse fossils from this period. Prior to this period, organisms were single-celled, but over the Cambrian Explosion, lasting about 80 million years, life forms diversified rapidly to resemble the life forms existing today.
The cornea is the only part of the eye that touches air.
Answer:
The main purpose of the circulatory system is to transport blood, oxygen, nutrients and hormones to and from different cells and tissues throughout the body.
Explanation:
This system works hand-in-hand with the respiratory system to facilitate the exchange of oxygen and carbon dioxide within the blood per the alveoli in the lungs.
Mitochondria since it’s the power house of the cell where the energy for this one is produced