Sensory Reception

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Internal and external stimuli are detected by organisms and lead to a response. 

Stimulus - detectable change in the internal or external environment of an organism that produces a response in the organism.

Ability to respond to stimuli increases the chance of survival for an organism.  

Organisms that survive have a greater chance of raising offspring and passing on their alleles to the next generation. 

Always a selection pressure favouring organism with more appropriate resopnses.

Stimuli are detected by cells or organs known as receptors. 

Receptors - transform the energy of a stimulus into some form of energy that can be processed by the organism and lead to response. Response is carried out by a range of cells, e.g. cells, tissue, organs. Known as effectors.

Measure of communication between effectors and receptors are hormones - relatively slow process found in both plants and animals. 

Animals have a more rapid means of connection. Nervous system has coordinator which is linked to receptors and effectors. 

stimulus --> receptor --> coordinator --> effector --> response 

TAXES 

Taxis - simple response whose direction is determined by the direction of the stimulus. 

A motile organism response directly to environmental…

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