Page 101 - NCERT Science Class 10 English Medium

energy. Material like sucrose is transferred into phloem tissue using
energy from ATP. This increases the osmotic pressure of the tissue
causing water to move into it. This pressure moves the material in the
phloem to tissues which have less pressure. This allows the phloem to
move material according to the plant’s needs. For example, in the spring,
sugar stored in root or stem tissue would be transported to the buds
which need energy to grow.

Q U E S T I O N S

1. What are the components of the transport system in human beings?
What are the functions of these components?
2. Why is it necessary to separate oxygenated and deoxygenated blood in
mammals and birds? ?
3. What are the components of the transport system in highly organised
plants?
4. How are water and minerals transported in plants?
5. How is food transported in plants?

EX
5.5 EXCRETIONCRETION
5.5 EXCRETIONCRETION
5.5
5.5 EX
5.5 EXCRETION
We have already discussed how organisms get rid of gaseous wastes
generated during photosynthesis or respiration. Other metabolic activities
generate nitrogenous materials which need to be removed. The biological
process involved in the removal of these harmful metabolic wastes from
the body is called excretion. Different organisms use varied strategies to
do this. Many unicellular organisms remove these wastes by simple
diffusion from the body surface into the surrounding
water. As we have seen in other processes, complex
multi-cellular organisms use specialised organs to
perform the same function.

5.5.1 Excretion in Human Beings

The excretory system of human beings (Fig. 5.13)
includes a pair of kidneys, a pair of ureters, a urinary
bladder and a urethra. Kidneys are located in the
abdomen, one on either side of the backbone. Urine
produced in the kidneys passes through the ureters
into the urinary bladder where it is stored until it is
released through the urethra.
How is urine produced? The purpose of making
urine is to filter out waste products from the blood.
Just as CO is removed from the blood in the lungs,
2
nitrogenous waste such as urea or uric acid are
Figure 5.13 removed from blood in the kidneys. It is then no
Excretory system in human beings
surprise that the basic filtration unit in the kidneys,

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