Skip to main content
Biology LibreTexts

25.6: Glossary: F

  • Page ID
  • facilitated diffusion

    diffusion with the help of transport proteins

    Fallopian tube

    one of two female reproductive organs that carry eggs from an ovary to the uterus and are the site where fertilization usually takes place

    fast-twitch muscle fiber

    type of skeletal muscle cell that is mainly responsible for anaerobic activities such as weight lifting

    fatty acid

    simple lipid molecule that consists mainly of chains of carbon and hydrogen atoms and that may exist alone or as a monomer of larger lipid molecules


    solid waste that remains after food is digested and that is eliminated from the body through the anus


    type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to one or more other compounds and the formation of NAD+

    fertility awareness method

    contraceptive method in which a woman monitors signs of ovulation and avoids unprotected vaginal intercourse around the time of ovulation when fertilization is most likely to occur

    fertility rate

    average number of livebirths per woman by the end of the childbearing years


    union of two haploid gametes (egg and sperm), resulting in a diploid zygote

    fetal viability

    point in fetal development at which a fetus is likely to be able to survive outside the uterus


    prenatal human organism between the embryonic stage and birth (weeks 8 through 38 after fertilization)


    indigestible carbohydrates such as cellulose that is needed in the human diet for normal bowel movements, among other functions

    fibrous connective tissue

    type of connective tissue that is found in skin, tendons, and ligaments and that is composed of parallel bundles of collagen fibers, making it tough and elastic

    fibrous joint

    immovable joint in which bones are connected by collagen fibers; also called a suture

    fight-or-flight response

    involuntary human body response mediated by the nervous and endocrine systems that prepares the body to fight or flee from perceived danger


    in the context of evolution by natural selection, the relative ability of an organism to survive and produce fertile offspring

    flexibility exercise

    any physical activity that stretches and lengthens muscles

    folic acid

    micronutrient needed for good health and reproduction; also called vitamin B9


    anatomical structure that consists of a small cluster of cells, surrounding a central cavity

    follicle-stimulating hormone (FSH)

    pituitary gland hormone that stimulates the ovaries to secrete estrogen and mature follicles


    “soft spot” on an infant’s skull that gradually ossifies after birth


    organic molecules that organisms use for energy, building materials, and other purposes

    foodborne disease

    any disease that is transmitted via food; also called food poisoning

    food chain

    diagram that represents a single pathway by which energy flows through organisms an ecosystem

    food web

    diagram that represents multiple interacting pathways by which energy flows through organisms in an ecosystem

    foramen ovale

    temporary opening between the right and left atria of the fetal heart that allows blood to bypass the pulmonary (lung) circulation until the fetus starts breathing air after birth

    force of evolution

    any one of four factors (mutation, gene flow, genetic drift, and natural selection) that changes allele frequencies in a population’s gene pool


    preserved remains or traces of an organism that lived in the past

    fossil fuel

    nonrenewable energy resource that forms over millions of years from dead plants and produces pollutants and greenhouse gases when it burns; coal, petroleum, or natural gas

    fossil record

    record of life on Earth as told by the discovery and analysis of fossils

    frameshift mutation

    deletion or insertion of one or more nucleotides that changes the reading frame of the genetic code

    free radical

    highly reactive chemical such as OH- that can damage DNA and contribute to diseases such as cancer

    freshwater biome

    aquatic biome such as a pond, lake, stream, or river in which the water contains little or no salt

    frontal lobe

    part of each hemisphere of the cerebrum that controls executive functions such as reasoning and language

    frontier science

    science undertaken in new areas at the frontier of knowledge in a particular field


    tissue destruction, usually in the extremities, that occurs when tissue freezes

    fungi (singular, fungus)

    organisms in the Fungus Kingdom that includes molds, mushrooms, and yeasts, some of which cause human disease