Explanation: The shape of a river's stream bed affects the speed and eroding power of a river by influencing the amount of friction between the water flowing through the river and the stream bed below. Friction is the force that opposes the motion of one surface as it moves across another surface. In a river, there is friction between the flowing water and the stream bed beneath it. Where a river is deep, less water comes into contact with the stream bed, so there is less friction. The reduced friction means there is less opposition to the water's motion, so the river flows at a greater speed and has more kinetic energy for erosion. On the other hand, where a river is shallow, more water comes into contact with the stream bed, so there is more friction. The increased friction means there is more opposition to the water's motion, so the river flows at a lesser speed and has less kinetic energy for erosion. Also, the roughness of a stream bed covered with boulders and other obstacles causes the water to flow through the river in a turbulent fashion. This could cause the river to move slower in some cases or erode more in other cases.
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Answer:
d. Epithelial tissues are nourished by blood vessels in adjacent tissues, thus diffusion is limited to thin tissues.
Explanation:
Epithelial tissues have tightly packed cells and have no space for blood vessels to be present between adjacent epithelial cells. The cells of the epithelial tissues get nutrients from the blood vessels of neighboring connective tissues.
Since the exchange of nutrients between the cells of the epithelial and connective tissues occurs through diffusion, epithelial tissues are only one to few cells layers thick to allow nutrient supply to all of its cells.
1.they are capable of dividing and renewing themselves for long peroids
2. they are unspecialized
3.they can give rise to specialized cell types
Protozoans, bacteria, fungi... viruses are not organisms
