The process which planetesimals combine with other planetesimals is called Accretion.
There are other names which refer to as accretion. For example, Accretion geology is termed as the increase in the size of a tectonic plate by addition of materials which convergent boundary.
Accretion atmosphere is termed as the process by which water vapor which is in clouds forms water droplets around nucleation sites.
Accretion astrophysics is termed as the formation of planets and other bodies through a collection of material through gravity.
Answer:
Due to presence at early days of the planet.
Explanation:
We only find the remains of single celled organisms in the oldest fossils because the single celled organisms are the organisms that were present in the early days of this planet. These single celled microbes were present about 3.7 billion years ago while on the other hand, the oldest rocks are only a little older i. e. 3.8 billion years so these single celled organisms are considered as oldest fossils on this planet.
From what i know, the feet of an animal should always be on the table. This is due to the fact that aside from health reason's, the animal usually feels more comfortable not on it's back.