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6.5.4: Key Terms

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    Acclimatory adjustments: Processes by which an individual organism adjusts to maintain homeostasis in response to environmental challenges.

    Activated melanogenesis: Increase in melanin production in response to ultraviolet radiation (UV) exposure.

    Adaptation: alteration in population-level gene frequencies related to environmentally induced selective pressures; leads to a greater level of fitness for a population related to a specific environment.

    Adjustment: Non-genetic-based ways in which organisms adjust to environmental stressors.

    Allen’s Rule: Due to thermal adaptation, homeothermic animals have body volume-to-surface ratios that vary inversely with the average temperature of their environment. In cold climates, the anticipated ratio is high and it is low in warm climates.

    Basal melanogenesis: Genetically-mediated, non-environmentally influenced base melanin level.

    Behavioral adjustments: An individual’s culturally mediated responses to an environmental stressor in an effort to maintain homeostasis.

    Bergmann’s Rule: For a broadly distributed monophyletic group, species and populations of smaller size tend to be found in environments with warmer climates and those of larger size tend to be found in ones that are colder.

    Cline: A continuum of gradations (i.e., degrees or levels) of a specific trait.

    Conduction: Mechanism of heat transfer between objects through direct contact.

    Convection: Movement of heat away from a warm object to the cooler surrounding fluid (i.e., gas or liquid).

    Convergent evolution: Evolutionary process where organisms that are not closely related independently evolve similar traits as a product of adaptation to similar evolutionary parameters.

    Erythrocyte: Red blood cell; most common form of blood cell—principle means of transporting oxygen throughout the circulatory system.

    Evaporation: Mechanism of heat transfer where liquid is transformed into a gas utilizing energy (e.g., heat).

    Folic acid: Form of B complex vitamin necessary for proper fetal development.

    Gloger’s Rule: For mammals of the same species, those with more darkly pigmented forms tend to be found closer to the equator and those with lighter forms are found in regions further from the equator.

    Hematocrit: Volume percentage of red blood cells within the blood.

    Homeostasis: Condition of optimal functioning for an organism.

    Hyperpnea: Increased depth and rate of respiration.

    Hypothalamus: Small portion of the human brain responsible for body temperature regulation.

    Lactase persistence: Genetic mutation permitting the continued production of lactase-phlorizin hydrolase enzyme in the small intestine past the weaning period.

    Melanin: Black-brown pigment produced by melanocytes; one of the primary pigments in skin.

    Melanocytes: Specialized cells that produce melanin.

    Phenotypic plasticity: Ability of one genotype to produce more than one phenotype dependent on environmental conditions.

    Polyphenism: Multiple discrete phenotypes from an organism’s genotype in response to the environment; a special form of phenotypic plasticity.

    Radiation: Mechanism of heat transfer involving electromagnetic energy being emitted from an object.

    Sickle cell disease: A group of genetically inherited blood disorders characterized by an abnormality in the shape of the hemoglobin within erythrocytes (red blood cells).

    Stressor: Any stimulus resulting in an imbalance in an organism’s homeostatic balance.

    Vasoconstriction: Narrowing of the blood vessels due to contractions of the muscular vessel walls.

    Vasodilation: Dilation of the blood vessels due to relaxation of the muscular vessel walls.

    6.5.4: Key Terms is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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