B3.4 Animal Behaviour & Plant Responses ANSWERS

Worksheet TwoOrientation Responses 2

  1. Taxis is an orientation response where the whole organism moves towards or away from a directional stimulus, a tropism is a growth response where part of the organism grows towards or away from the stimulus.

Taxes / Description / Example / Survival Advantage
Positive phototaxis / Organism moves towards higher light intensity / Chlamydomonas / More light for photosynthesis provides more energy.
Negative phototaxis / Organism moves away from higher light intensity / Slaters / Stays in cooler areas to prevent desiccation.
Positive hydrotaxis / Organism moves towards water/ moisture / Earthworm / To prevent desiccation.
Negative hydrotaxis / Organism moves away from water/ moisture / Periwinkle / Moves up shore as tide rises, maintaining position relative to water.
Positive chemotaxis / Organism moves towards a chemical / Bacteria / Moves towards higher glucose concentrations for respiration.
Negative chemotaxis / Organism moves away from a chemical / Bacteria / Moves away from poisons/ toxins to survive.
Positive thermotaxis / Organism moves towards heat / Mammalian sperm / Increased chance of fertilisation.
Negative thermotaxis / Organism moves away from heat / Nematode worm / Stays in a soil environment with less temp fluctuations to maintain efficient physiological processes.
  1. Both responses are taxes which mean the whole organism moves towards or away from a directional stimulus. Tropotaxis and klinotaxis refer to how many receptors detect the stimulus. Tropo- is two receptors such as a slater with two antennae. Klino- is one receptor such as a maggot. The survival advantage of tropotaxis is that the organism can detect the stimulus simultaneously on both sides and move directly to the preferred direction.
  1. Both are responses to a stimulus. Taxes are a response to a directional stimulus whereas kineses are responses to the intensity of the stimulus. For example, slaters show both responses. They are negative phototaxic and move away from light. They also show thigmokinesis and slow down when they are touched. Both responses reduce desiccation of the slater.

Kineses can be split into two groups, ortho- and klinokinesis. Orthokinesis is where the rate of movement or speed is changed as in the above example. Klinokinesis is a change in the rate of turning. Slaters also show hydrokinesis and will increase their rate of turning in drier conditions to be able to increase their chance of finding more humid conditions and avoid desiccation.

  1. The periodic mass movement of a population from one defined area to another. Discusses at least two advantages e.g. breeding grounds, better climate etc. Discusses at least two disadvantages, e.g. getting lost, exhaustion/death. Discusses at least two triggers, e.g. day length, temperature. Includes a named NZ example, e.g. Bar-tailed Godwits fly to Alaska and back.
  1. The inherent ability of an animal to navigate towards an original location through unfamiliar areas. For example, pigeons.
  1. Three methods described e.g. sun, landmarks, moon and stars, scent, magnetic field.

Geomagnetic Compass / The mechanism that allows an organisms to find its way by the location of the Earth’s magnetic field.
Homing / The inherent ability of an animal to navigate towards an original location through unfamiliar areas.
Innate / An inherited characteristic.
Kineses / A movement that is a response to a stimulus but is not oriented with respect to the source of stimulation, e.g. turning and rate of movement.
Learned / Obtained from experience.
Migration / The periodic mass movement of a population from one defined area to another.
Nastic / Movements are non-directional responses to stimuli.
Orientation / Position or alignment relative to points of the compass or other specific directions.
Ortho- / Klinokinesis / Is a movement or activity of a cell or an organism in response to a stimulus. Ortho- is the speed of the organism and klino- is the rate of turning of the organism.
Star Compass / The mechanism that allows an organisms to find its way by the location of the stars.
Sun Compass / The mechanism that allows an organisms to find its way by the location of the sun.
Taxes / A directional movement in response to a directional stimulus.
Tropo- / Klinotaxes / Tropotaxes refers to the organism detecting the stimulus with two receptors whereas klinotaxes is detecting with one receptor.