Lesson 3: Orientation in Animals

Vocabulary

• Innate behaviour - behaviours that are inherited and automatic responses, not learned

• Taxis - directional response to a stimulus

• Kinesis - non-directional response to a stimulus

• Effector - muscle and glands that respond to stimulu based on signals received from the CNS

• Environmental cue/ stimulus - a change in an organism’s environment to which it can respond

• Klinokinesis - change in the speed movement depending on the intensity of stimulus

• Orthokinesis - change in the frequency or rate of turning

• Sensory receptor - detect and convert environmental stimulus into electric signals

Types of Responses

The types of responses an organism has to the environment can be described using prefixes based on the stimuli.

• light → photo

• temperature → thermo

• chemicals → chemo

• gravity → geo/gravi

• current → rheo

• touch → thigmo

• water → hydro

• food → tropho

Taxes

Taxes are directional response to a stimulus. The organism can either move towards (positive taxis) or away (negative) from the stimulus.

Types of Taxes

1. Phototaxis - movement caused by the light either towards a source or away from it

2. Thermotaxis - response of animals to temperature

3. Chemotaxis - animal’s response to chemical substance

4. Geotaxis - animal’s response to gravity

5. Rheotaxis - response to current of air or water

6. Thigmotaxis - response to contact or touch

Kinesis

Kinesis is a non-directional response to a stimulus. The rate of movement of an organism is affected by the intensity of the stimulus.

Types of Kinesis

1. Orthokinesis - refers to a change in the speed movement.

For example in higher humidity, slaters will move slower that they would move in lower humidity.

2. Klinokinesis - refers to a change in the frequency or rate of turning

For example, Flatworms turn rapidly in the light than the dark areas.