TRANSPORTATION, CIRCULATION & EXCRETION IN ORGANISMS - II : BRIEF ANSWERS

ANSWER IN BRIEF

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1. Describe : Ascent of sap.
   

   ANS:
   

   
   
   • Plants absorb water and minerals from the soil through root hairs.
     
   • Water along with minerals then moves through root cortex and endodermis to reach the root xylem.
     
   • From root xylem they enter the interconnected stem xylem which branches into leaves.
     
   • This transportation of water and minerals from the roots to the leaves is known as the ascent of sap.
     

   
   

   
   
2. Explain : Rhesus factor.
   

   ANS:
   

   
   
   • Blood contains an antigen called Rh factor (Rhesus factor).
     
   • A person with Rh antigen in blood is called Rh +ve and one lacking it is called Rh -ve.
     
   • Incompatibility of Rh factor causes problems.
     
   • If an Rh +ve man marries an Rh -ve woman, the birth of the first child is normal. But mother's blood forms antibodies against Rh antigen.
     
   • If the second child is Rh +ve, the antibody in mother's blood reacts with the Rh antigen of the foetus and causes problems, sometimes leading to the death of the child.
     

   
   

   
   
3. Describe excretion and osmoregulation in amoeba.
   

   ANS:
   
   

   
   
   • Amoeba is a fresh water unicellular organism.
     
   • It has a contractile vacuole for excretion and osmoregulation.
     
   • The waste produced in the cell enters contractile vacuole along with water.
     
   • The size of the contractile vacuole gradually increases and then it moves closer to the plasma membrane.
     
   • It bursts after touching the plasma membrane and releases the excretory substances into the surrounding water by diffusion.
     

   
   

   
   
4. Give reason : An Rh(-ve) woman should not marry an Rh(+ve) man.
   

   ANS: [Refer to last two points mentioned in the answer about Rhesus factor].
   

   
   
5. Distinguish between xylem and phloem.
   
   ANS:
   
   
6. Distinguish between blood and lymph.
   
   ANS :
   
   
7. Distinguish between artery and vein.
   
   ANS :