In morning and evening times except red light all colours scatter more
and vanish before they reach our eye. Since scatering of red light is
very small, it reaches us. So sun appears red in colour during sun
rise and sun set.
Q: How do you appreciate the working of ciliary muscle in the eye? (4 Marks)
A: The ciliary muscle to which eye lens is attached helps the eye lens
to change its focal length by changing the radii of curvature of the
eye lens.
When the eye is focussed on a distant object, the ciliary muscles are
relaxed so that the focal length of the eye lens has its maximum value
which is equal to its distance from the retina. The parallel rays
coming into the eye are then focussed on to the retina and we see the
object clearly. When the eye is focussed on a closer object, the
ciliary muscles are strained and focal length of eye-lens decreases.
The ciliary muscles adjust the focal length in such a way that the
image is formed on retina and we see the object clearly. This process
of adjusting focal length is called "accommodation". This is a
wonderful arrangement the nature provided in the eye. If this is not
provided we would not have lead the present comfortable life with
regard to our vision.
Q: Explain briefly the reason for the blue of the sky. (2 Marks)
A: When we look at the sky in a direction perpendicular to the
direction of the Sun rays the sky appears blue. If our angle of view
is changed, the intensity of blue colour also changes. Molecules of N2
and O2 are the causes for the blue colour of the sky.
The sizes of these molecules are comparable to the wavelength of blue
colour light. So these molecules act as scattering centres for the
blue colour of light. So the sky appears blue.
Q: How can you correct the defect 'hypermetropia'? (2 Marks)
A: Eye lens can form a clear-image on the retina when any object is
placed beyond near point. To correct the defect of hypermetropia, we
need to use a lens which forms an image of an object beyond near
point, when the object is better near point and least distance of
distinct vision. This is possible only when a double convex lens is
used.
Q: Explain the basic process in scattering of light. (1 Mark)
A: Scattering of light is a complex phenomenon. Atoms or molecules
which are exposed to light absorb light energy and emit some part of
the light energy in different directions. This is the basic process
happens in scattering of light.
Junior Inter Zoology - Essay Question from Ecology and Environment
Q: Give an account of energy flow in ecosystem.
A: Except for the deep sea ecosystem, sun is the only source of energy
for all ecosystems on earth. Of the incident solar radiation, less
than 50% of it is photosynthetically active radiation. The producers
(i.e., green plants) fix the solar energy to synthesise food materials
from CO2 and H2O. They trap 2 to 10% of PAR and it sustains the entire
living world.
The heterotrophs depend on producers for their food either directly or
indirectly. The first law of thermodynamics (law of conservation of
energy) states that energy is neither created nor destroyed, but is
transformed from one form to another. Thus the solar energy that is
traped by the producers is converted into chemical energy. Further,
ecosystems also follow the second law of thermodynamics, which states
that no process involving energy transformation will spontaneously
occur unless there is degradation of energy.
As per this law energy dispersed is in the form of unavailable heat
energy, and constitutes the entropy. The organisms need a constant
supply of energy to synthesise molecules they need. The transfer of
energy through a food chain from one trophic level to the next is
called energy flow. The amount of energy available decreases at
successive trophic levels.
When organism dies, the energy in it becomes source of energy for
decomposers. According to 10% law (proposed by Lindeman), during the
transfer of energy from one trophic level to the next, only about 10%
of the energy is stored. The remaining is lost during transfer. The
energy transfer in a food chain can be illustrated as shown below.
A: Except for the deep sea ecosystem, sun is the only source of energy
for all ecosystems on earth. Of the incident solar radiation, less
than 50% of it is photosynthetically active radiation. The producers
(i.e., green plants) fix the solar energy to synthesise food materials
from CO2 and H2O. They trap 2 to 10% of PAR and it sustains the entire
living world.
The heterotrophs depend on producers for their food either directly or
indirectly. The first law of thermodynamics (law of conservation of
energy) states that energy is neither created nor destroyed, but is
transformed from one form to another. Thus the solar energy that is
traped by the producers is converted into chemical energy. Further,
ecosystems also follow the second law of thermodynamics, which states
that no process involving energy transformation will spontaneously
occur unless there is degradation of energy.
As per this law energy dispersed is in the form of unavailable heat
energy, and constitutes the entropy. The organisms need a constant
supply of energy to synthesise molecules they need. The transfer of
energy through a food chain from one trophic level to the next is
called energy flow. The amount of energy available decreases at
successive trophic levels.
When organism dies, the energy in it becomes source of energy for
decomposers. According to 10% law (proposed by Lindeman), during the
transfer of energy from one trophic level to the next, only about 10%
of the energy is stored. The remaining is lost during transfer. The
energy transfer in a food chain can be illustrated as shown below.
Jr Inter Zoology SA Questions from Ecology and Environment
Q: Explain Vant' Hoff rule
A: i. Van't Hoff stated that "with the increase of every 10°C, the
rate of metabolic activities doubles". It was popularly called Vant'
Hoff rule.
ii. It also states that with the decrease of every 10°C, the Naction
rate is halved.
iii. The effect of temperature on rate of a reaction is expressed in
terms of temperature coefficient or Q10
iv. In the living systems the Q10 value is about 2.0
Q: Describe green house effect.
A: Under normal conditions the temperature at the surface of earth is
maintained by the energy balance of sun rays that strike the earth and
heat that is radiated back into space. However, when there is an
increase in concentration of green house gases (like CO2, methane
etc.) in the atmosphere prevents the heat from being reradiated out.
The thick layer of green house gases acts like the glass panels of a
green house, allowing the sun light to filter through but preventing
the heat from being re-radiated into outer space. This is so called
green house effect. Thus most heat is absorbed by the green house
gases and water vapour adds to the heat already present.
The net result is the heating up of the earth's atmosphere (global
warming). As a result, meeting of ice caps in polar regions resulting
in rise of sea levels, causing submersion of certain islands and
coastal areas.
A: i. Van't Hoff stated that "with the increase of every 10°C, the
rate of metabolic activities doubles". It was popularly called Vant'
Hoff rule.
ii. It also states that with the decrease of every 10°C, the Naction
rate is halved.
iii. The effect of temperature on rate of a reaction is expressed in
terms of temperature coefficient or Q10
iv. In the living systems the Q10 value is about 2.0
Q: Describe green house effect.
A: Under normal conditions the temperature at the surface of earth is
maintained by the energy balance of sun rays that strike the earth and
heat that is radiated back into space. However, when there is an
increase in concentration of green house gases (like CO2, methane
etc.) in the atmosphere prevents the heat from being reradiated out.
The thick layer of green house gases acts like the glass panels of a
green house, allowing the sun light to filter through but preventing
the heat from being re-radiated into outer space. This is so called
green house effect. Thus most heat is absorbed by the green house
gases and water vapour adds to the heat already present.
The net result is the heating up of the earth's atmosphere (global
warming). As a result, meeting of ice caps in polar regions resulting
in rise of sea levels, causing submersion of certain islands and
coastal areas.
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