Receptors detect changes in the environment. For a stimulus to elicit a response, certain cells must have an appropriate receptor. Stimulation of the receptor initiates a specific signal pathway.
The fundamental unit among them (not derived) is :
Answer:
a. Biomagnification
Explanation:
Biomagnification is the name given to the progressive accumulation of substances from one trophic level to another along a food chain. Thus, the substance will have its highest concentration in individuals who occupy trophic levels furthest from producers.
For biomagnification to occur, substances must be fat soluble (lipid soluble) and thus adhere to living tissues. Another feature of substances that undergo biomagnification is that they are generally not biodegradable or metabolized by the body.
The phenomenon is quite common with heavy metals (lead; mercury) and certain chlorinated and aromatic organic compounds with higher molecular mass, such as the insecticide DDT.
Answer:
There are three main types of blood vessels:
1)Artery ---
i) It is a blood vessel having a thick wall.
ii) It carries blood from the heart to different parts of the body.
iii) On regulatory demand of the body it can dilate or constrict.
iv) It doesn't contain any valve.
v) All arteries carry oxygenated blood except the pulmonary artery.
2)Vein ---
i) It is a blood vessel having a thin wall.
ii) It brings blood from different parts to the heart.
iii) It can't dilate or constrict under normal conditions.
iv) It contains valves that allow the blood to flow in one direction towards the heart.
v) All veins carry deoxygenated blood except the pulmonary vein.
3)Capillary ---
i) It is a very narrow blood vessel that has very thin walls.
ii) It forms a network throughout the body in all living cells connecting arteries to veins.
iii) It can dilate or constrict according to the requirement of tissue.
iv) It doesn't have any valve.
v) It contains mixed blood as it connects arteries and veins
