Animal Behaviour and Plant Responses. Year 13 Biology
Overview • Orientation • Tropisms • Nastic responses • Plant hormones • Taxes and Kineses • Migration and Dispersal • Homing
Overview • Timing • Environmental Cycles • Biological clocks • Biological rhythms
Revision • The environment • The environment includes all the factors, both living (biotic) and non-living (abiotic), that affect the lives of organisms. • Abiotic – The physical factors in an environment (non-living) • Biotic – The living factors in an environment.
Revision • Main Abiotic factors • Light (photo-) • Gravity (geo- or gravi-) • Temperature (thermo-) • Water (hydro-) • Chemicals (chemo-) • Touch (thigmo-) • Current (rheo-)
Revision • Abiotic Factors • are the physical parts of the environment to which organisms respond. For most organisms, the physical factors must be kept within quite a narrow optimum range that fits the tolerance for that species. • If the factor is extreme in either direction the organism suffers from physiological stress, and if the factor becomes too extreme it leads to death. (recall the zones of tolerance)
Niche • Niche - You could say that the habitat is an organism’s address, and that the ecological niche is its profession. The ecological niche is a description of; • the opportunities provided by the habitat; and • The adaptations of the organism that enable it to take advantage of those opportunities.
Adaptations • Most organisms are a combination of many adaptations that allow them to fit into their environment easily. Adaptations are grouped into three types; • Structural • Behavioural • Physiological
Detecting a stimulus • A stimulus is a change in the environment (external or internal) that causes a response in an organism. • A receptor is any cell or group of cells that can detect this change • A effector is a cell or group of cells that can respond to the change.
Detecting a stimulus Environmental stimulus Receptor detects Coordinating system Communicating system Effector responds Other information
Orientation responses of plants • Plants respond to light, gravity, water, chemicals and touch. They do this by a growth curve towards or away from a stimulus. • If the growth is towards the stimulus we say it is positive; if it is away from the stimulus we say it is negative. • The prefixes you learnt before tell us the type of stimulus e.g. photo = light.
Tropisms • A tropism is a GROWTH response towards or away from an environmental stimulus coming from one direction. • For example • If the shoot of a plant grows towards the light, we say it is positively phototropic • If the root of a seedling grows down, then we say it is positively geotropic
Nastic Responses • The response of plants to diffuse stimuli that do not come from any particular direction, such as the temperature, humidity and light that surround a plant, are called nastic responses. • For example • the opening and closing of flowers in response to different light intensities.
Nastic Responses • Nastic movements are classified according to the nature of the stimulus • For example • Photonasty is the response to alterations in the light intensity • Thermonasty is the response to changes in the temperature
Plant Hormones • Plants use hormones to regulate their growth and development. • Plant hormones (or phytohormones) are organic compounds produced in one part of the plant and transported to another part, where they produce a growth response.
Plant Hormones • There are 5 groups of plant hormones; • Auxins (indolacetic acid or IAA) • Cytokinins • Gibberellins • Ethene • Abscisic acid (ABA) • Together they control growth and development on the plant at various stages.
Auxin – indolacetic acid IAA • The effect of auxin on roots and shoots • The effect of auxin is different on the shoot, lateral buds (side buds found in the axis of the leaves where the leaf joins the stem), and the root. • It all depends on the concentration of the auxin
Auxin Concentrations • Low auxin concentrations stimulate root growth, and high concentrations inhibit root growth. • Low auxin concentrations stimulate growth of lateral buds; high concentrations inhibit this. • Low auxin concentrations do not stimulate the growth of shoots, but high concentrations do.
Apical dominance • Apical dominance • If you take a bean shoot and leave it to grow, the intact tip keeps the lateral buds from growing. • If, however you remove the apical bud (the bud at the tip of the main growing shoot) the two lateral buds start to grow within hours. • If you were to place a plug onto the apical bud that contained auxin you would find that the growth of the lateral buds is inhibited.
Other effects of auxin • Cell elongation • Encourages root development • Involved in the abscission (dropping of leaves and fruit). It appears to delay this. • Stimulates growth of the cambium when a tree stem is under stress • Suppression of root elongation • Initiations of flowering in some plants
Cytokinins • Produced mainly in the roots • Functions • Promote cell division • Slow down the process of aging (senescence) in plants. • If applied to leaves it can prevent the yellowing of mature leaves in autumn and their dropping (abscission)
Gibberellins • Originates from a fungus Gibberellafugikuroi . This caused a disease that made plants grow so tall they toppled over and rotted. Gibberellins have now been isolated from this fungus.
Gibberellins • Functions • Increases the internode length • Promotes the germination of a wide variety of seeds that would otherwise be hard to germinate • Causes flowering on biennials that normally need a period of chilling (vernalisation)
Gibberellins • Which plant received gibberellin treatment?
Ethene • The saying that ‘one rotten apple will spoil the barrel’ is actually true – a ripening apple gives off a gas called ethylene that ripens adjacent fruit, even a fruit of a different type! • Functions • Accumulates in mature fruit to induce ripening • Promotes leaf fall
Abscisic Acid (ABA) • Generally abscisic acid functions as an inhibiting hormone acting against auxin, gibberellins and cytokinins all of which tend to promote growth • Functions • growth inhibitor made in the leaf chloroplasts in response to water stress. Acts on guard cells causing stomatal closure • Induces leaf fall (only in a few selected species) • Promotes seed dormancy
Biological orientation responses in animals • In this case the term orientations means a behaviour by which the animals positions itself in a certain way in relation to its surroundings. • These include taxes and kinesis, homing and migration.
Taxis • This is the movement of the whole animal, towards or away from a stimulus which is coming from one side only. • As with tropisms, movement towards a stimulus is positive and away from a stimulus is negative. • The stimulus is also denoted by the same prefixes.
Taxis • Examples • Flatworms moving towards a pieces of raw meat are showing positivechemotaxis • Moths flying to a light are positivelyphototactic • Trout will line themselves up in an upstream direction, so they are positivelyrheotactic
Taxis • Taxes often involve moving the head (which carries the sensory receptors) from side to side. • If there are two sensory organs then the animal can move directly towards or away from the stimulus as it can constantly check the position of the stimulus. • If there is only one sensory organ, the animal must move around to get information about the stimulus. E.g. a maggot must move its head from side to side to keep in position. It performs a zigzag ‘direct’ line.
Taxis • Task • Identify the environmentalcue involved and the adaptivevalue of the behaviour • Chemotaxis • Thermotaxis • Phototaxis • Thigmotaxis • Gravitaxis • Hydrotaxis
Kinesis • This is a non-directional response to a stimulus. • It is the change in activity rate in response to a change in the intensity of the stimulus. • Example • If woodlice are placed in a wet/dry choice chamber, the animals in the dry side increases their random movements and rate of turning compared with those on the wet side.
Kinesis • Orthokinesis – the speed of the movement is related to the intensity of the stimulation • Klinokinesis – the amount of randomturning is related to the intensity of the stimulation. • See diagrams for summary.
Pheromones • A pheromone is a chemical produced by an animal and released into the external environment where it has an effect on the physiology or behaviour of members of the same species. • Task • Outline the many ways animals use pheromones.
Migration • Refers to regular, annual or seasonal mass movements made by animals from their breeding area to another area.
Advantages of Migration • Animals remain in a favourable temperature • They grow larger • They leave more offspring • They have a constant supply of food • It may lead to the colonisation of a new area • Reduces predation/parasitism disease • Greater genetic mixing • Better breeding conditions
Disadvantages of Migration • They may get lost or caught in a storm • They may get eaten by a predator • The may use up too much energy in the migration, leading to exhaustion • They may starve • It is a huge investment in energy
Trigger to migration • The behavioural trigger that sets off migratory behaviour varies. • Some trigger include • Maturation – some animals migrate as the sex organs mature and there is a need or desire to reproduce • Environmentalcues – such as drop in temperature, shortening of the length of the day e.g. migratory birds (migratory restlessness) • Genetic Drive – The trigger may be inbuilt (innate) e.g star patterns for navigation are learned, but how to learn then is innate • Endogenous circadian rhythm – internal biological clock.
Methods of Migration • Piloting – An animal moves from one landmark that it is familiar with to another landmark, until it reaches its destination • Generally used over short distances and uses visual cues.
Methods of Migration • Compass Orientation – an animal can detect a compass direction, and travels in a straight-line path until it reaches its destination. This can be accomplished using the magnetic field lines of the earth, chemical cues and sound.
Methods of Migration • Navigation – is the process by which an animal uses various cues to determine its position in reference to a particular goal.
Methods of Navigation • Visual • Solar • Magnetic fields • Stellar (stars) • Chemical • Sonar (sound)
Homing • This is the ability of an individual to return to the home site after it has been away to look for food, sometimes over considerable distances.
Timing Responses • Timing • Environmental Cycles • Biological clocks • Biological rhythms
Environmental Cycles • The astronomical cycles • The motions of the Earth, moon and sun result in complex and interdependent cycles. • These create environmental changes that range from short term to long term.