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F214 definitions

lucy.wright73 Biology A2 revision A Levels Inglés 12 fichas

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1Negative feedbackProcess that reverses any change in the internal environment, to ensure that an optimum steady state can be maintained. Homeostasis is negative feedback system.
2Positive feedbackProcess that increases any change detected by the receptors. Tends to be harmful and does not lead to homeostasis.
3HomeostasisThe MAINTENANCE of the INTERNAL ENVIRONMENT in a CONSTANT state DESPITE external CHANGES.
4Endocrine glandDuctless gland that secretes hormones directly into the blood.
5Exocrine glandGland that secretes molecules into a duct that carries the molecules to where they are used.
6HormoneA molecule released into the blood (by an endocrine gland) that acts as a chemical messenger.
7Target tissueA tissue whose cells have receptors for a particular hormone. This is the tissue where the hormone has its effects.
8ExcretionThe removal of metabolic waste from the body
9AutotrophOrganism that uses light energy or chemical energy, and inorganic molecules to synthesise complex organic molecules (food).
10Photosynthetic pigmentSubstance that absorbs light energy. Found in thylakoid membranes, in photosystems. Each pigment absorbs energy associated with light of a specific wavelength. Examples include chlorophyll a and chlorophyll b.
11Respiratory substrateAn organic substrate that can be used for respiration.
12HeterotrophOrganism that ingests and digests complex organic molecules, releasing the chemical potential energy stored in them.