T
taste buds
Structures on the tongue that contain chemoreceptors, which respond to four main sensations—sour, salty, bitter, and sweet—to create the sense of taste.
taxonomy
The study of biological classification.
telophase
The final stage of mitosis before cytokinesis. In telophase, the nuclear envelope re-forms around separated sister chromatids and kinetochore microtubules disappear. Cell elongation also occurs during this phase. The final stage of the first meiotic division (meiosis I), during which chromosomes arrive at the poles of the cell and begin to recondense; the final stage of the second meiotic division (meiosis II), during which chromosomes arrive at the poles of the cell, the nuclear envelope begins to re-form, and the chromosomes begin to recondense.
tendon
Connective tissue between bones and muscles.
testes
The male gonads; sperm and testosterone are produced here.
testosterone
A hormone necessary for sperm production in men. Also responsible for developing and maintaining the secondary sex characteristics of males, starting at puberty.
thyroid
Gland that produces the hormone thyroxine, which increases the metabolism of most of the cells in the body. Located in the neck.
tissue
A group of closely connected and similar cells that cooperate to generate a specific structure or specialized function within an organism.
tracheophyte
A terrestrial plant with a vascular system.
trait
Any observable feature or  of an organism.
transfer RNA (tRNA)
An RNA molecule used in protein synthesis as a link helping to convert messenger RNA into amino acids.
transpiration
The process by which a plant loses water to its environment through evaporation.
trophic level
Steps on a food/biomass pyramid that are defined by organisms within a community that are the same distance from the primary producers in a food web.
tropism
Long-term growth of a plant toward or away from a stimulus.
tuber
Fleshy underground storage structure composed of an enlarged portion of the stem that has on its surface buds capable of producing new plants.


U
uterus
Structure in the female reproductive system in which the embryo develops.

V
vascular cambium
Tissue that produces new vascular cells; lies between the xylem and phloem in dicot stems.
vascular tissue
A conductive component (either xylem or phloem) of the vascular system that transports food and nutrients throughout the plant body.
vegetative propagation
A form of asexual reproduction in which plants produce genetically identical offshoots (clones) of themselves, which then develop into independent plants.
vein
A blood vessel that carries blood back to the heart. The blood in veins is not oxygenated, with the exception of the pulmonary vein.
vertebrate
An animal that has a skeletal rod of bone or cartilage running up its back, surrounding the nerve cord. Segments of this rod are called vertebrae. All vertebrate animals belong to subphylum Vertebrata, part of phylum Chordata.
vestigial structures
Bodily structures that developed in the past but no longer serve any function for an organism.
villi
Fingerlike projections in the small intestine that increase surface area and maximize the absorption of nutrients.
vitamins
Complex molecules that usually serve as coenzymes, assisting in physiological processes.

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