agnostic: A person who believes that the existence of a god or creator and the nature of the universe is unknowable.
algae: An umbrella term for various simple organisms that contain chlorophyll (and can therefore carry out photosynthesis) and live in aquatic habitats and in moist situations on land. Algae range from macroscopic seaweeds such as giant kelp, which frequently exceeds 30 m in length, to microscopic filamentous and single-celled forms such as Spirogyra and Chlorella. For example, if a gene determines the seed color of peas, one allele of that gene may produce green seeds and another allele produce yellow seeds.
acquired trait: A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation (for example, the large muscles of a weightlifter).
adaptation: Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment.
antibacterial: Having the ability to kill bacteria.