single human being. Single people, looked at separately from others.

Hard; not easy; you need to work hard to do it.

aquatic or terrestrial annelid worm with suckers at both ends. Freshwater worm that sucks blood. habitually exploit or rely on.

certainly.

group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. Subsections of a genus (of plants, animals).

separate or respective. more than two but not many. More than two but not a large amount.

Protecting the environment or a species.

To turn something on.

particular order in which related things follow each other. To arrange things in an order they should happen.

consequence, effect, or outcome of something. Final scores of competitions, elections or games. occur or follow as consequence of something.

used for emphasis with following adjective functioning as adverb. Thing that is not yet known or named.

(of phone call) paid for by person receiving it. in way that is paid for by person receiving call. To gather things, people together in one place.

of, on, or relating to earth. inhabitant of earth. Concerning the earth; not of, in the air or space.

To establish the facts about; discover.

warm-blooded vertebrate animal of class that is distinguished by possession of hair or fur, females that secrete milk for nourishment of young. Animals which drink milk from its mother.