1. differentiate between nastic and tropic movement.( 3 points)

2. differentiate between receptors and effectors.(3 points)

plz help...



Tropic  movement

Nastic  movement

A tropic movement is the type of biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant induced by some external stimuli. This response is dependent on the direction of the stimulus.

Nastic movement is that type of movement that is not governed by the direction of the stimulus. Whatever be the direction of stimulus, the movements always occur in a particular direction.







Receptors are special structures located on the different parts of the body that are capable of recognizing and receiving messages.

Those cells which produce response after receiving a particular stimulus are known as effectors.

For example - olfactory receptors for detecting smell, gustatory receptors for detecting taste, etc.

For example- contraction of muscles for movement of different body parts, release of hormones from glands etc.

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 Receptor cells and organs

The cells and organs that receive internal and external stimuli are called receptors. These receptors vary in complexity from single cells to complex organs. Their function is to receive information from the external and internal environment and to convey that information to the nervous system. One way to classify sensory receptors is to consider them as biological transducers......meaning they take one form of energy and convert it to another. They are constructed to receive certain kinds of stimuli and are categorized by this feature. One can divide them according to their sensitivity to various forms of energy. Thus we have mechanoreceptors that respond to touch, pressure, tension, sound and motion. Photoreceptor respond to light; thermoreceptors respond to heat; pain receptors respond to tissue damage; osmoreceptors that respond to changes in water volume; and chemoreceptors that respond to chemicals and result in taste or smell sensations.
Mechanoreceptors vary greatly. The skin contains specialized mechanoreceptor cells that react to touch and muscles have stretch receptors. The ear has the ability to process sound waves and to detect acceleration and orientation of the body. It is a very complex receptor organ, has two distinct functions, balance and hearing. Both functions, however, rely on mechanoreception. The sound is transmitted by air pressure changes to the eardrum, the inner ear ossicles (hammer, anvil and stirrup), and finally the oval window of the cochlea. The movement of the oval window causes the fluid inside the cochlea to move and, depending on the frequency of the sound, specialized ciliated cells are stimulated. The inner ear also contains three fluid filled canals (vestibular apparatus) which also contains ciliated cells. The stimulation of these cells signals the adjacent sensory neurons to let us know which direction we are moving and how fast.

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 tropisms and Nastic Movements

Unlike animals, plants cannot move to more favorable locations. Instead, plants survive by adjusting their growth to their local environment. A major way this is done is by sensing the directions of environmental signals such as light and gravity. This sensory information is then used to orient the direction of growth toward or away from a stimulus in a process called a tropism. By these mechanisms, shoots grow up from the ground and into the light. This enhances photosynthesis and biomass by increasing the amount of sunlight absorbed by chlorophyll. The raised stature of the plant also promotes pollination and seed dispersal, and increases plant competitiveness.
Tropisms are different from nastic movements. Like tropisms, these plant movements are influenced by environmental cues. But the direction of a nastic movement is independent of where the signal comes from, and most such movements are temporary. Nastic movements are more specialized in function and distribution than tropisms. For example, some insectivorous plants capture prey by moving trap organs together.
Tropisms should not be confused with tactic movements found in many microorganisms, such as a unicellular green alga that moves toward the light (phototaxis). Because plants are not motile, only part of their body grows in the direction of a stimulus.


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 thumbs up plz

this will help u

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 copy n  paste  and  want  thumbs up 

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reply in simple lang with small font....... and i want 3 points.....

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  in tabular form yaar please 


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 your answer is                                                                                                                                                                                                                                                     

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do you know what question are coming in question paper

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