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Biology

Answer the following questions briefly :

(i) How are the cytons and axons placed in the brain and the spinal cord ?

(ii) Which part of the human ear gives 'Dynamic balance' and 'Static balance' to the body ?

(iii) Explain how the human eye adapts itself to bright light and dim light.

(iv) What is Parthenocarpy ? Give one example.

(v) Mention any two objectives of 'Swachh Bharat Abhiyan'.

Chemical Coordination in Plants

ICSE 2019

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Answer

(i) In the brain, outer portion contains cyton which gives a grayish colour hence called as gray matter, while axon is inside forming the white matter.
In spinal cord, cyton is inside forming the gray matter and axon is outside forming white matter.

(ii) Dynamic balance — semicircular canal
     Static balance — utriculus and sacculus (vestibule)

(iii) When we move from dark or dim lit area to a brightly lit area, visual purple of rods is bleached reducing their sensitivity and pupil constricts to reduce the amount of light entering the eyes. This is light adaptation.
When we move from brightly lit area to dark area, visual purple of rods which were earlier broken due to bright light regenerates and pupil dilates to allow more light to enter. This is dark adaptation.

(iv) Parthenocarpy refers to the development of fruits without prior fertilization.
Examples — Apple, Grapes, Tomato.

(v) Two objectives of Swachh Bharat Abhiyan are:

  1. To clean the streets, roads and infrastructure of the country's cities and towns.
  2. To eliminate open defecation through the construction of individual, cluster and community toilets.

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