The correct answer is it always occurs in a predictable pattern.
Ecological successsion is defined as a <em>change in the structure of species of an ecological community over a period of tim</em>e. The succession that begins in a new environment by uninfluence of pre-existing species is called primary succession. The disruption of pre-existing community because of succession is called secondary succession. Ecological succession happens in a predictable pattern. The ecological communities undergoes predictable change which creates a disturbance or initial formation of new habitat. This changes occurs in an orderly manner and can be best explained by the example of trees how they grow bigger and bigger.
<span>Human skin color variations are primarily being determined by the type and amount of melanin pigment which is the skin.
The reason is the amount of melanin present, pigment present which determines the color of skin the more the melanin the more dark color they are.
Human skin color variation is likely evolved in response to differences in intensity of sunlight around the world. Reason being it has been developed because of different exposure of humans to the varied environment during migration. Human skin color variation evolved recently in hominid evolution.</span>
Answer:
Blood flows from the right atrium into the right ventricle through the open tricuspid valve, and from the left atrium into the left ventricle through the open mitral valve