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ORIENTATION RESPONSES How organisms position themselves in relation to their surroundings Animal Behaviour • Innate behaviours: also known as instinctive. These are genetically determined, not modified by experience. They are inflexible and stereotyped, “hard-wired”. • Learnt behaviours: These change as a result of experience. They are flexible and not rigid. What are the abiotic stimuli? STIMULUS Light Gravity Temperature Water (or Humidity) Chemicals Touch Current (in water) PREFIX PhotoGraviThermoHydro- (or Hygro-) ChemoThigmoRheo- Simple Animal Orientation Responses • Taxis • Kinesis TAXIS (plural Taxes) – Orientation and movement of whole animal towards or away from external stimulus that is coming from one side only – Described as positive (toward) or negative (away from) a stimulus – Moving toward light = positive photo-taxis Examples of animal taxes • Earthworms move away from light back down into the soil = Negative phototaxis • Snails move away when their feelers touch something …. = Negative thigmotaxis • Flatworms and sharks move towards meat = Positive chemotaxis Mosquito moves toward warm skin What’s the advantage? • Puts the animal in a more favourable position • Avoids unfavourable conditions (hot, cold etc) • Increased survival and reproduction How do animals determine the direction of the stimulus? • Two sense organs: By comparing the input from receptors on each side of the animal at the same time • Differences between sides show the direction of the stimulus (eg. Snail antennae) • OR One sense organ: Compare the change from a single sensor over time, using its body orientation to determine stimulus direction KINESIS (plural kineses) = Non-directional response to a change in stimulus intensity ….. It is not orientating – Animal may simply turn randomly or change its rate of movement – Slater moves more when it is hot = thermokinesis More terms to know Orthokinesis = the stimulus intensity determines the organism’s speed of movement Klinokinesis = the stimulus intensity determines the organism’s rate of turning Examples of Kineses • Slaters move faster in bright light and slower in dim light = photo-orthokinesis (or photokinesis) • Woodlice: move faster and turn more in high humidity vs. low humidity (hygro-) = hygro-orthokinesis, hygro-klinokinesis (or hygrokinesis) • Human body lice turn more at 35°C than at lower temps = thermo-klinokinesis (or thermokinesis) What’s the advantage? • Puts the animal in a more favourable position by moving faster or randomly turning • Eg. Slaters will end up in dark, damp places which prevents drying out (dessication) • Avoids unfavourable conditions (hot, cold etc) • Increased survival and reproduction BIOZONE questions • Taxes and Kineses • Do all the questions on page 5 NCEA 2006 question • Much of animal behaviour is innate, or inborn. Such behaviour patterns may be quite simple, or are produced in response to simple stimuli. They include kineses and taxes. • (a) Describe an example of kinesis in a named animal. • (b) Explain why this behaviour would be an advantage to your named animal in its normal environment. Plant Orientation Responses Plants are capable of a number of movements in response to environmental stimuli. eg. Temperature, humidity, light, touch, chemicals 1. NASTIC RESPONSES: non-directional rapid responses to stimuli 2. TROPISMS: Directional slower growth responses towards or away from a directional stimulus Nastic Responses Rapid, reversible, non-directional movement responses by parts of a plant to changes in abiotic factors such as: – Light intensity – Heat – Touch – chemicals – Water – gravity • Non-directional, so they do not have a positive or negative aspect to the movement. • They occur due to changes in the intensity of the stimulus. • Generally: the rate or frequency of these responses increases as intensity of the stimulus increases. • They are named with the suffix "-nasty" and have prefixes that depend on the stimuli • Eg. Photonasty: response to changing light intensity Examples of plant responses • Mimosa pudica: the sensitive plant • https://www.youtube.com/watch?v=BLTcVNy OhUc • Venus fly traps – jaws of death https://www.youtube.com/watch?v=O7eQKSf0L mY Caused by… • Generally they are caused by rapid changes in osmotic pressure in certain cells. • This leads to a sudden loss of turgor pressure – Eg. mimosa leaves folding up What’s the adaptive purpose? • A nastic response removes a plant, or part of a plant, from unfavourable environmental conditions…. Placing it in favourable environmental conditions. Eg. Mimosa plant • When the sensitive leaves are touched, they droop down and fold up rapidly • = Thigmonasty • Advantage: why? • Reduces the plant’s Surface area for grazing And abiotic stress. Venus Fly Trap Plant What happened? What was the stimulus? Advantages? Photonasty • The collapse of leaves when exposed to high light intensity. • Eg. the leaves of the Oxalis plant, which are normally horizontal, collapse and droop downwards when light increases. • Why? May prevent damage to the leaf’s cells from exposure to high light intensities. Other examples • Opening/closing of tulip and crocus flowers due to changes in air temperature – Called? PLANT TROPISMS • Directional growth response that occurs in response to an external directional stimulus • May be positive (towards stimulus) or negative (away from stimulus) • Tropism comes from a Greek word ‘tropos’ meaning “to turn” or “to change” Why? • Plants can alter their growth so they can grow towards more favourable conditions (eg. More light, more water etc) • Must detect where the conditions are better then alter their growth to "move" in the appropriate direction PHOTOTROPISM = the directional growth response of a plant in response to a light stimulus. • Different parts of a plant exhibit different reactions to light. • Stems and shoots exhibit positive phototropism (grow toward light) • Most roots exhibit negative phototropism (grow away from light) GRAVITROPISM = the directional growth response of a plant in response to gravity. • Roots exhibit positive gravitropism (towards) • Stems and leaves exhibit negative gravitropism. THIGMOTROPISM • Thigmotropism is the growth response of a plant to physical contact (touch). • Plants that cling to physical structures such as sticks exhibit positive thigmotropism. HYDROTROPISM • Directional growth in response to presence of water in the soil • Roots = positive hydrotropism (grow toward water) Note: stronger than gravitropism CHEMOTROPISM • Directional growth in response to a chemical stimulus • eg. Roots can grow towards or away from chemicals in the soil (copper pipe) • eg. Growth of pollen tube towards ovary in flowers (ovary releases chemicals) THIGMOMORPHOGENESIS !! An alteration in growth patterns caused by touch (eg. wind, rain) Type of tropism? Positive or negative? One Advantage? 1. 2. 3. 4. 5. 6. 7. 8. Roots of a seedling grow down …………………….. Stem of vine winds around a branch……………….. Leaves of pot plant turn toward window……….. Roots of willow grow sideways toward water…… Roots grow away from copper pipes in soil…. Shoots of seedling grow upward in dark lab… Pollen tube in flower grows toward ovary….. Tree grows sideways on an exposed mountain… Control of Plant Growth • Plant growth is controlled by HORMONES • These are chemicals produced in one part of the plant and transported to where they produce a growth response. Terminology… Coleoptile (co – lee – op – tile) is the protective sheath covering the emerging shoot in plants such as oats and grasses. Auxins • A group of hormones that regulate plant growth • Indole Acetic Acid, IAA (the first auxin isolated) • Made in the tips of the shoots and roots, and can diffuse to other parts of the shoots or roots. • Causes cell elongation in stems Phototropism in Coleoptiles…. • Tip of shoot detects light stimulus, auxin is produced • Auxin causes cell elongation in the stem If light comes from an angle: • Auxin moves to shaded side of stem, cells elongate • Shoot bends towards light Auxin moves to shaded side and causes cell elongation - stem bends towards light source • More auxin on the shaded side • Cells elongate • Stem bends toward light over time The diagram shows the typical results shown by oat seedlings grown in a box with a light from one side Seedlings Results and explanations A The tips have been removed. No auxin is produced and the shoots do not grow longer. B The tips have been covered so light cannot reach them. Auxin is in the same concentration on both sides of the shoots, so they grow evenly and longer on both sides. C One side of the tips are in more light than the other side. Auxin is in a greater concentration on the shaded side, causing the cells there to grow longer than the cells on the lit side. Shoot bends towards the light. TROPISMS….. You tube clip: Plant Physiology: Phototropic Response http://www.youtube.com/watch?v=zctM_TWg5Ik Experiments with Grass/Oat Coleoptiles • Shoots and roots respond differently to high concentrations of auxins: • cells in shoots grow more • cells in roots grow less. Gravitropism in roots • In roots, perception of gravity appears to depend on the settling of specialised organelles called statoliths in root-cap cells. Statoliths are denser than cytoplasm. • When the plant is turned, within minutes the statoliths sink toward the source of gravity, to the side that is down. • This signal causes redistribution of auxin streams in the root cap and root as a whole. Statoliths sink towards the source of gravity (down) Auxin and root growth • Auxin builds up on the lower side of the root cap, causing inhibition of cell elongation and downwards growth of the root. (note – auxin causes an opposite effect in roots compared to shoots) • Pea shoot time lapse…. https://www.youtube.com/watch?v=eDA8rmUP 5ZM THIGMOTROPISM • Growth is inhibited on the side of stem being touched • Cells elongate on the nontouching side due to auxin • Causes the stem to coil around the object being touched Worksheet • Have a go at all the questions Terminology time! COLEOPTILE = the protective sheath covering tip of the first new shoot from a seed Darwin studied phototropism in canary grass and oat coleoptiles. The coleoptile is a hollow sheath of tissue which surrounds the apical axis (stem) of these and other grasses. Darwin demonstrated that these coleoptiles are phototropic in that they bend toward a light source. When he covered the tips of the coleoptiles, they were not phototropic but when he covered the lower portions of the coleoptiles, they were phototropic. Darwin concluded from these and other experiments that (a) the tip of the coleoptile is the most photosensitive region; (b) the middle of the coleoptile is responsible for most of the bending; and (c) an influence which causes bending is transmitted from the top to the middle of the coleoptile. Read more: Phototropism - History Of Phototropism Research - Coleoptile, Darwin, Coleoptiles, Plant, Agar, and Light http://science.jrank.org/pages/5197/Phototropism-History-phototropismresearch.html#ixzz10OQbtO20