Coordination and Response in Plants and Animals Introduction

Response of Plants and Animals Syllabus Objectives Define ‘stimulus’ and ‘response’ Describe the response of: Green plants to unilateral stimuli of light and gravity Invertebrates to variations in light intensities, temperature and moisture Explain why the response to stimuli is important for the survival of organisms

Stimuli and response Plants and Animals receive information about changes in conditions both inside and outside their bodies Any information to which an organism reacts is known as a stimulus because it stimulates the organism to make a response

Stimuli and Response A stimulus could be an external event Change in direction of light Change in light intensity or Change in temperature Internal events include Arrival of food in the stomach Changes in blood glucose level Entry of foreign organisms in the body or change in water content of cells

Stimuli and Response Some changes can be Question positive or advantageous, unfavourable or harmful, unimportant Question Can you list 2 favourable stimuli, 2 unfavourable stimuli and 2 that are unimportant

Stimuli and Response Response can be through Response in plants the movement of the whole animal E.g. earthworm moving away from light the movement of part of the animal E.g. closing of the pupil of the eye to bright light Response in plants Movement through part of the organism E.g. tip of a plant grows in the direction of light

Response and Stimuli Can you list 3 examples of what a response to an internal stimulus could be? Secretion of enzymes in response to food Production of antibodies in response to foreign organisms Secretion of hormones in response to changes in blood glucose levels An increase in heart rate in response to an increase in CO2 content of the blood

The Importance of response Response to stimuli is important for the survival of organisms Shoots of green plants grow toward the light so that they could make food Roots grow in the direction of gravity. They grow towards moisture and provides stability for the plant Animals avoid unsuitable conditions by moving to suitable ones

The Importance of response Hunted animals avoid predators when they see, hear or smell their approach A male moth is attracted to a female moth by being able to detect and respond to chemical signals released by the female This response ensures that reproduction takes place and the species survives The Sensitive plant (Mimosa pudica) folds its leaves quickly when touched. This makes it more difficult for animals who eat them to see them.

Practice Investigative Questions How do the shoots of seedlings respond to receiving light from one direction only? Will roots grow downwards regardless of how the rest of the seed or seedling is positioned? How do millipedes, earthworms and/or woodlice respond to variations in light intensities? How do small invertebrates respond to temperature changes? How do small invertebrates respond to different levels of moisture?