Take water in a flask and heat it. It is seen that water near the flame gets hot and it rises up. The cold water from the side moves down, towards the source of heat. This water also

gets hot and rises and more water moves down from the side. This process continues till the whole water gets hot. This mode of heat transfer is called convection. Similar process happens in gases.

(i) Inorganic impurities - nitrates, phosphates and metals.
(ii) Organic impurities - fruit and vegetable wastes, oil, urea, human faeces, animal waste, pesticides and herbicides

Various alternative arrangements for sewage disposal other than WWTP are septic tanks, chemical toilets and composting pits. Septic tanks are suitable for places where there is no sewage system, such as hospitals, isolated buildings or cluster of 4-5 houses. In other methods, the excreta flow through covered drains into a biogas plant. The biogas thus produced is used as a source of energy.

Cleaning of water is a process of removing pollutants from water before it enters a water body or is reused. This process of waste water treatment is commonly known as sewage treatment. It takes place in several stages.

Differences between distance and displacement:

(a) Plane mirrors are used as looking glasses. They are also used in solar cookers, periscopes and kaleidoscopes.
(b) Concave mirrors are used as reflectors in the headlights of automobiles. As these give erect and magnified images, these are used by doctors to examine parts of bodies, such as ear, nose, throat etc.
(c) Convex mirrors can be used to view a much larger area than is possible with a plane mirror. These are therefore used as rear view or side view mirrors in cars and scooters.

The animals which have a separate part of stomach (rumen) are called ruminants. In this part the food is partially digested and is called cud. But later the cud returns to mouth in small lumps and the animal chews it. This process is called rumination or chewing cud. These animals are called ruminants.

Polar regions present an extreme climate because:
(i)These regions are covered with snow and it is very cold for most part of the year.
(ii) For six months the sun does not set at the poles while for another six months it does not rise.
(iii) In winters, the temperature can be as low as - 37°C.

(a)

Fig. : Pitcher Plant showing lid and pitcher
(b) Autotrophic and Heterotrophic both.
(c) Partial heterotroph.

(i) Shearing
(ii) Scouring,
(iii) Sorting
(iv) Fibre spinning,
(v) Dyeing
(vi) Rolling intp the yarn

True, because photosynthesis is important for the existence of life on the earth. Photosynthesis is important process as it is provides food to all living organisms and maintains CO₂ - O₂ balance of nature.

Soil contains nitrogen in the form that is not usable by plants. Bacteria like Rhizobium converts nitrogen into soluble form that can be easily used Q. by plants. So, if plant has a requirement for nitrogen, then it will obtain that which the help of bacteria.

Ruminants such as cows and buffaloes swallow their food hurriedly and store it in a part of the stomach called rumen. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans. Later, this partially digested food is returned to the buccal cavity of the animals in small lumps and animal chews it to complete the process of digestion. This process is called rumination.

The various associated glands of digestive system and their role in digestion are as follows.
(i) Salivary gland digestion of starch in mouth.
(ii) Liver secretes bile juices which help in the digestion of fats.
(iii) Pancreas secretes pancreatic juices which act on carbohydrate, fats and proteins and change them into simpler compounds.

Glucose is a simple sugar or carbohydrate which is broken down in the presence of oxygen into CO₂ and H₂O and releases instant energy. Glucose is easily absorbed by the blood, hence provides instant energy to the body.

Cellulose is the carbohydrate that can be digested by ruminants but not by humans because ruminants have a large sac-like structure called rumen which is located between the small intestine and large intestine. Certain bacteria are present in rumen which helps in digesting cellulose.

Plants prepare their own food by the process of photosynthesis. Leaves of the plants have green pigment called chlorophyll, which helps them to capture the energy of the sunlight. The plants synthesise their food from carbon dioxide and water in the presence of sunlight. This process is called photosynthesis. The reaction for the process of photosynthesis can be shown as follows:

During photosynthesis, food is synthesised and oxygen is released in the process.

Differences between parasites and saprotrophs