4TAXIS (plural Taxes)Orientation and movement of whole animal towards or away from external stimulus that is coming from one side onlyDescribed as positive (toward) or negative (away from) a stimulusMoving toward light = positive photo–taxis
5Examples of animal taxes Earthworms and slaters move away from sunlight back down into the soil= Negative phototaxisSnails move away when their feelers touch something ….= Negative thigmotaxisFlatworms and sharks move towards meat= Positive chemotaxis
7What’s the advantage? Puts the animal in a more favourable position Avoids unfavourable conditions (hot, cold etc)Increased survival and reproduction
8How 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 timeDifferences 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
9KINESIS (pl. kineses)= Non-directional response to a change in stimulus intensity ….. It is not orientatingAnimal may simply turn randomly or change its rate of movementSlater moves morewhen it is hot= thermokinesis
10More terms to knowOrthokinesis = the stimulus intensity determines the organism’s speed of movementKlinokinesis = the stimulus intensitydetermines the organism’srate of turning
11Examples of KinesesSlaters move faster in bright light and slower in dim light= photo-orthokinesisWoodlice: move faster and turn more in high humidity vs. low humidity (hygro-)= hygro-orthokinesis, hygro-klinokinesisHuman body lice turn more at 35°C than at lower temps= thermo-klinokinesisPositive photo-orthokinesis,
12What’s the advantage? Puts the animal in a more favourable position Eg. Slaters will end up in dark, damp places which prevents dessicationAvoids unfavourable conditions (hot, cold etc)Increased survival and reproduction
13BIOZONE questionsTaxes and KinesesDo all the questions on page
14NCEA 2006 questionMuch 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.
15Plant Orientation Responses Plants are capable of a number of movements in response to environmental stimuli.eg. Temperature, humidity, light, touch, chemicals1. NASTIC RESPONSES: non-directional responses to stimuli2. TROPISMS: Directional growth responses towards or away from a directional stimulus
16Nastic ResponsesThe 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 stimuliEg. Photonasty, thigmonasty
17Examples on you tube Mimosa pudica: the sensitive plant Venus fly traps – jaws of death
18Eg. Mimosa plantWhen the sensitive leaves are touched, they droop down and fold up rapidlyThigmonastyAdvantage: why?Reduces the plant’sSurface area for grazingAnd abiotic stress.
19Venus Fly Trap PlantWhat happened?What was the stimulus?Advantages?
20Other examplesOpening/closing of tulip flowers due to changes in air temperatureCalled?Opening of evening-primrose flowers at dusk
21PLANT TROPISMSDirectional growth response that occurs in response to an external directional stimulusMay be positive (towards stimulus) or negative (away from stimulus)Tropism comes from a Greek word ‘tropos’ meaning “to turn” or “to change”
23Why?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
24PHOTOTROPISM= 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)
25GRAVITROPISM= the directional growth response of a plant in response to gravity.Roots exhibit positive gravitropism (towards)Stems and leaves exhibit negative gravitropism.
26THIGMOTROPISMThigmotropism is the growth response of a plant to physical contact (touch).Plants that cling to physical structures such as sticks exhibit positive thigmotropism.
27HYDROTROPISMDirectional growth in response to presence of water in the soilRoots = positive hydrotropism(grow toward water)Note: stronger than gravitropism
28CHEMOTROPISM 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)
29THIGMOMORPHOGENESIS !!An alteration in growth patterns caused by touch(eg. wind, rain)
30Type of tropism? Positive or negative? One Advantage? 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…
31Control of Plant Growth Plant growth is controlled by HORMONESThese are chemicals produced in one part of the plant and transported to where they produce a growth response.
32Terminology… Coleoptile (co – le – op – tile) is the protective sheath covering the emerging shoot in plants such as oats and grasses.
33Auxins A group of hormones that regulate plant growth Indole Acetic Acid, IAA(the first auxin isolated)Causes cell elongation in stems
34Phototropism in Coleoptiles…. Tip of shoot detects light stimulus, auxin is producedAuxin causes cell elongation in the stemIf light comes from an angle:Auxin moves to shaded side of stem, cells elongateShoot bends towards light
35Auxin moves to shaded side and causes cell elongation - stem bends towards light source
36More auxin on the shaded side Cells elongateStem bends toward light over time
37TROPISMS….. You tube clip: Plant Physiology: Phototropic Response
39Gravitropism in rootsIn roots, perception of gravity appears to depend on the settling of specialised organelles called statoliths in root-cap cells.When the plant is turned, within minutes the statoliths sink toward the source of gravity, to the side that is down.Auxin builds up on the lower side of the root cap, causing cell elongation and downwards growth of the root
40THIGMOTROPISM Growth is inhibited on the side of stem being touched Cells elongate on the non-touching side due to auxinCauses the stem to coil around the object being touched
43Terminology time!COLEOPTILE = the protective sheath covering tip of the first new shoot from a seedDarwin 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