(a) Describe the parts of our tooth with the help of a labelled diagram.
(b) What is meant by dental caries ? How are they caused ?
(c) What is dental plaque ? What harm can it do ? How can the formation of plaque be prevented ?
(a) The tooth has hard outer covering called enamel. The part of tooth below enamel is called dentine inside which is the pulp cavity. The pulp cavity contains nerves and blood vessels.
(b) The formation of small cavities (or holes) in the teeth due to the action of acid forming bacteria and improper dental care is called dental caries. This happens as follows: When we eat sugary food, the bacteria in our mouth act on sugar to produce acids. These acids dissolve the calcium salts from the tooth enamel and then from dentine forming small cavities in the tooth over a period of time in our mouth act on sugar to produce acids. These acids dissolve the calcium salts from the tooth enamel and then from dentine forming small cavities in the tooth over a period of time.
(c) If the teeth are not cleaned regularly, they become covered with the sticky, yellowish layer of food particles and bacteria cells called dental plaque. It causes tooth decay. It can be prevented by brushing the teeth regularly as it neutralises the acids.
What is the name of tiny projections on the inner surface of small intestine which help in absorbing the digested food ?
Draw a neat diagram of excretory system of human beings and label on it:
(i) Left kidney (ii) Urinary bladder
(a) What criteria can be used to decide whether something is alive ?
(b) What is meant by life processes ? Name the basic life processes common to all living organisms which are essential for maintaining life.
What are the different ways in which glucose is oxidised to provide energy in various organisms ? Give one example of each.
Draw a diagram of human excretory system and label renal artery and urethra.
State in brief the function of :
(a) Draw a diagram of human respiratory system and label the following:
(i) part where air is filtered by fine hair and mucus
(ii) part which terminates in balloon – like structures
(iii) balloon – like structures where exchange of gases takes place. (iv) part which separates chest cavity from abdominal cavity.
(b) Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?
In the experiment "Light is essential for photosynthesis", why does the uncovered part of the leaf turn blue-black after putting iodine solution?
What is the name of the opening in the human body through which undigested food is thrown out ?
Fill in the following blanks with suitable words :
(a) All green plants are…………..
(b) All non-green plants and animals are…………
(c) Heterotrophs depend on…….. and other……………… for food,
(d) Green plants use……… ,………… and………… to make food.
(e) Iodine turns blue-black on reacting with………………
(a) Define a nutrient. Name four important nutrients present in our food.
(b) What are the various types of heterotrophic nutrition ?
(a) Which part of the body secretes bile ? Where is bile stored ? What is the function of bile ?
(b) What is trypsin ? What is its function ?
(a) What is common for Cuscuta, ticks and leeches ?
(b) Name the substances on which the following enzymes act in the human digestive system :
(i) Trypsin (ii) Amylase (iii) Pepsin (iv) Lipase
(c) Why does absorption of digested food occur mainly in the small intestine ?
(a) Why is small intestine in herbivores longer than in carnivores ?
(b) What will happen if mucus is not secreted by the gastric glands ?
(c) What causes movement of food inside the alimentary canal ?
In the lungs :
(a) what substance is taken into the body ?
(b) what substance is removed from the body ?
"All plants give out oxygen during day and carbon dioxide during night". Do you agree with this statement? Give reason.
A Give one reason why multicellular organisms require special organs for exchange of gases between their body and their environment. :
(a) Name the pigment in leaves which absorbs sunlight energy.
(b) What is the colour of this pigment ?
Apart from carbon dioxide and water, name four other raw materials which are needed by the plants.
All the animals can be divided into three groups on the basis of their eating habits. Name the three groups.