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(a) How does excretion take place in plants? (b) Describe the role of the human skin in homeostasis.

      

(a) How does excretion take place in plants? (b) Describe the role of the human skin in homeostasis.

  

Answers


Alex
a ' Diffusion of Carbon (IV) Oxide; and
oxygen; through stomata and lenticels;
Some wastes are stored in tissues in non-
toxic form e.g. calcium oxalate;
Some of these tissues or organs drop off
from plants e.g. leaves,flowers, fruits and
bark of caffeine, nicotine, quinine;
Some wastes are released by transpiration
through stomata and lenticels such as water
vapour;
Others are released by guttation through
hydathodes as water;
Others are released by exudation. (max 4
marks)
When body temperature is lowered below
normal;
arterioles in the skin constrict;
blood is diverted to a shunt system;
less blood ?ows to the skin/less heat is lost;
when body temperature is raised above
normal;
arterioles in the skin dilate;
more blood ?ows to the skin;
more heat is lost by convection and
radiation;
when body temperature is lowered below
normal:
erector-pilli muscles contract, hair stands
erect;
more air is trapped, air is a bad conductor;
and insulates the body against heat loss;
when body temperature is raised above
normal:
erector-pilli muscles relax, hair lies on skin;
less air is trapped, more heat is lost;
when body temperature is lowered below
normal:
less fluids are absorbed by sweat glands;
less sweating, less vaporisation of water;
when body temperature is raised above
normal:
sweat glands are more stimulated and more
sweat is produced;
water in sweat evaporates and takes up heat
from the body;
body is cooled/body temperature is lowered;
alexis sadro answered the question on October 11, 2017 at 15:46


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