<em>Primary</em> succession is the type of succession which occurs in an area which was previously unoccupied and thus, has no formed soiled substratum.
A <em>pioneer</em> species is the one which are the first to colonise an area.
Now, when the primary succession has to take place, species like orchids, pineapple trees and sugar cane cannot be pioneer species as they require a nutrient rich and well developed soil substratum for their growth.
However, species like algae are very <em>hardy</em> and can begin their growth on nutrient deficient place with the available moisture. These can easily survive in a hostile environment and further pave the way for higher species and increase the diversity of a region.
Thus,<em> in areas where lava no longer flows and primary succession has to take place, only algae can be the pioneer species.</em>
Gravitational attraction provides the centripetal force needed to keep planets in orbit around the Sun and all types of satellite in orbit around the Earth. This means gravity makes the Moon accelerate all the time, even though its speed remains constant.
Homeostasis is the maintenance of a stable internal environment. Homeostasis is a term coined to describe the physical and chemical parameters that an organism must maintain to allow proper functioning of its component cells, tissues, organs, and organ systems.
