D. A keystone species existence keeps an ecosystem in balance.
Answer:
Hypotheses about the origins of life
Answer:
The nutrients in form of calories are fats and oils. The nutrients that regulate body processes and promote growth, development and maintenance of body tissues are Proteins.
Answer:
D. a wide variety of gradual and sudden changes to ecosystems
Explanation:
There have been different global climatic changes throughout the history of planet earth. The changes have been gradual or abrupt and have been due to various causes, such as those related to changes in orbital parameters, precession , variations in solar radiation, continental drift, periods of intense volcanism, meteorite impacts etc. Some changes to the ecosystems related to climatic changes are, for example,The Cretaceous-Tertiary extinction (which probably caused the extinction of the dinosaurs), the contraction of the forests during the last glacial maximum promoting biological diversification, the melting of the polar caps increasing sea level etc.
