the part of the Earth, including air, land, surface rocks, and water, within which life occurs, and which biotic processes in turn alter or transform
a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the non-living physical factors of the environment
a group of interacting organisms sharing an environment
the collection of inter-breeding organisms of a particular species
an individual living system (such as animal, plant, fungus, or micro-organism)
A group of related organs
a group of tissues that perform a specific function or group of functions
a cellular organizational level intermediate between cells and a complete organism
the structural and functional unit of all known living organisms
Cell structures and viruses
An organelle, or the layout of organelles of the biological cell itself
Living and nonliving organic molecules
a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds
the smallest unit of an element that retains the chemical properties of that element
an elementary or composite particle smaller than an atom
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