Orientation in Space
Animal Orientation in Space
Plant Orientation in Space
Concept 2: Types of Environmental Stimuli
Success Criteria & Vocabulary
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I can describe the different types of stimuli for animal and plant responses.
I can state the prefix for each stimulus.
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Chemo-: Prefix for a chemical oriented response.
Environment: All the factors in an organism's surroundings that can potentially affect it.
Gravi-: Prefix for a gravity oriented response.
Hydro-: Prefix for a water/moisture oriented response.
Negative response: Response away from the stimulus.
Photo-: Prefix for a light oriented response.
Positive response: Response towards the stimulus.
Prefix: A group of letters added to the beginning of a word to make a new word.
Receptor: A structure that detects stimuli and sends a signal to another part(s) of the organism.
Stimulus: A change in an organism's environment to which it can respond.
Thermo-: Prefix for a temperature oriented response.
Thigmo-: Prefix for a touch/pressure oriented response.
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Task called '3.3 Concept 1, 2, & 3'.
Responses to the Environment
RECAP: Abiotic Factors
RECAP: Biotic Factors and Competition
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Concept 2: Support Notes
Types of Stimuli
Orientation responses can be categorised according to the type of STIMULUS drawing out the RESPONSE.
Stimuli are ENVIRONMENTAL changes that an organism can detect using sensory RECEPTORS (e.g. sensory receptors in the eyes detect light).
Most animals, being mobile, monitor the environment as they move through it, so sensory receptors are concentrated in the head region. Stimuli are described using PREFIXES (e.g. photo-).
At its simplest, a response to a response to a stimuli can be towards or away from the stimulus. Orientation responses towards the stimulus are identified as POSITIVE. Orientation responses away from the stimulus are identified as NEGATIVE.
Chemicals (i.e. CHEMO-) indicate the presence of substances that may be useful (food) or harmful (e.g. poisons) or may indicate the location of other individuals.
Plants are immobile (i.e. they can't move around) so the ability of roots to grow towards available water sources (i.e. HYDRO-) aids survival.
INVERTEBRATES (i.e. animals without a spine) that dry out easily are found in high water or moist (i.e. HYDRO-) environments to prevent desiccation.
Touch (i.e. THIGMO-) is an important stimulus. It may indicate the presence of a threat or something that will give support.
Light (i.e. PHOTO-) can give information about the orientation (up or down) and about the presence of others. Sudden changes in light can indicate movement, which may need to be avoided.
Gravity (i.e. GRAVI-) allows organisms to orientate themselves vertically. Most animals tend to orientate their back-side up, and belly side down. In plants, gravity is an important stimulus for the correct orientation of shoots and roots.
Detecting changes in temperature (i.e. THERMO-) helps organisms survive by adjusting physiology or behaviour to their surroundings. An increase in temperature beyond a certain limit indicates the need to find shade. A decrease in temperature beyond a certain limit indicates the need to find a source of heat.