Estivation
A physiological state characterized by slow metabolism and inactivity, which permits
survival during long periods of elevated temperature and diminished water supplies.
Estrogens
The primary female steroid sex hormones, which are produced in the ovary by the
developing follicle during the first half of the cycle and in smaller quantities by the corpus
luteum during the second half. Estrogens stimulate the development and maintenance of
the female reproductive system and secondary sex characteristics.
Estrous cycle
A type of reproductive cycle in all female mammals except higher primates, in which the
nonpregnant endometrium is reabsorbed rather than shed, and sexual response occurs only
during midcycle at estrus.
Ethology
The comparative study of patterns of animal behavior, with emphasis on their adaptive
significance and evolutionary origin.
Ethylene
The only gaseous plant hormone, responsible for fruit ripening, growth inhibition, leaf
abscission, and aging.
Etiolation
In plants, a condition characterized by stem elongation, poor leaf development, and lack of
chlorophyll; occurs in plants growing in the dark or with greatly reduced light.
Etioplasts
Etioplasts are chloroplasts that have not been exposed to light. They are usually found in
plants grown in the dark. If a plant is kept out of light for several days, its normal
chloroplasts will actually convert into etioplasts.
Euchromatin
The more open, unraveled form of eukaryotic chromatin, which is available for
transcription.
Eukaryotic cells
A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles,
present in protists, plants, fungi, and animals; also called eukaryote.
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