This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page.

Program Mysteries of the Unseen World (logo height 65 pix)

    1. What is biological tropism?

      In biology, tropism refers to the growth or movement of an organism in response to environmental stimuli. Biological tropism is most commonly observed in plants.

    2. In addition to phototropism, or an organism’s response to light stimuli, what are at least two other types of tropism that exist in nature? 

      Answers vary but could include the following: chemotropism (response to chemicals), gravitropism/geotropism (response to gravity), hydrotropism (response to water), sonotropism (response to sound), thermotropism (response to temperature), or thigmotropism (response to touch).

    3. How is time-lapse photography different from high-speed, or slow-motion, photography?

      In time-lapse photography, individual frames are captured at a much slower rate than they are viewed. Then, when the frames are combined and played at normal speed (24 frames per second), time appears to be going faster. High-speed, or slow-motion, photography collects frames at a much faster rate (128 or more frames per second) than they are viewed, making time appear to slow down.

    • Dr. John Nash Ott’s work with time-lapse photography and plant growth led him to believe that exposure to different wavelengths of light could impact animal and human behavior. Ott discussed these views in his 1973 book, Health & Light
    • Auxins are the class of light-sensing hormones responsible for regulating phototropism in plants. 
    • In positive phototropism, organisms move or grow toward a light source. In negative phototropism, organisms move or grow away from a light source.
  • Term Part of Speech Definition Encyclopedic Entry
    high-speed photography Noun

    the science of taking pictures of very fast phenomena.

    photography Noun

    art and science of producing still or moving images using the chemical reaction of light on a sensitive surface, such as film or an electronic sensor.

    phototropism Noun

    growth or movement of a sessile organism toward or away from a source of light.

    time-lapse photography Noun

    photographing of a slow and continuous process at regular intervals, for projection at a higher speed.

    tropism Noun

    an orientation of an organism to an external stimulus, as light, especially by growth rather than by movement.

Tell us what you think

Funder

National Science Foundation Mysteries of the Unseen World

Partner

National Geographic Entertainment

Made Possible in Part By

Lockheed Martin