Stimuli and response

What is the sequence of events in a response to a stimulus?

Stimulus- a detectable change in internal/external environment

Receptor- detects specific stimulus

Coordinator- coordinates a suitable response

Effector- carries out response

Response- the action produced by effector

What is taxis?

An innate directional response to a stimulus

What is the difference between positive and negative phototaxis?

Positive phototaxis is when organisms move towards light such as for photosynthesis to synthesise food

Negative phototaxis is when organisms move away from light to prevent an earthworm drying out

What is positive chemotaxis?

The movement of an organism towards a region where a specific chemical is more concentrated like a phagocyte moving to a pathogen

What is kinesis and how does it increase an organisms chances of survival?

A kinesis is a non directional response where an adjustment of the movement speed and turning frequency of an organism occurs based on favourability of the environment. This increased turning or speed of movement increases the chances of the organism leaving unfavourable conditions. Such as woodlice increase their speed and turning frequency in dry conditions to increase the likelihood of them entering moist conditions

What is a tropism?

The growth of the part of an organism like a plant in response to a directional stimulus

How is a tropism different to a taxis?

Tropisms are growth of a part of an organism whereas taxis is whole movement of the organism