Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants. It is transported to the leaves through the xylem tissues.
Distinguish between a parasite and a saprotrophs?
Parasite
• A parasite takes readymade food from the organism on which it feeds.
• They feed on a living organism.
• The organism on which it feeds is called host.
• It deprives the host of valuable nutrients.
Saprotrophs
• They secrete the digestive juices on the matter they live and convert it into a solution and then absorb it.
• They feed on dead and decaying organism.
• They do not feed on a living organism.
• There is no host at all.
What is digestion?
The process of breaking down complex food substances into simple molecules is called as digestion.
What does the human digestive tract consists of?
Digestive system in human beings consists of alimentary canal and digestive glands.
Alimentary canal is made up of mouth, buccal cavity, pharynx, oesophagus, stomach, intestine, rectum and anus.
The digestive glands are the salivary glands, the gastric glands, the liver, the pancreas and the intestinal glands.
How do plants obtain carbon-dioxide for photosynthesis?
Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. Such pores are called stomata. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis. These pores are surrounded by ‘guard cells’. Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a function of the guard cells.
How do plants obtain nitrogen?
Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites. Or it is taken up as organic compounds which have been prepared by bacteria from atmospheric nitrogen. Atmospheric nitrogen is fixed by leguminous plants with the help of symbiotic bacteria present in the root nodules of these plants.
What is the role of stomach in digestion?
The stomach is divided into three compartments namely cardiac, fundus and pylorus. The junction of oesophagus and stomach is guarded by valve which does not allow the food to travel in backward direction.
• In the stomach, food is mixed with the gastric juices secreted by the gastric glands.
• Gastric juice is a combination of hydrochloric acid, enzymes like pepsin, lipase and mucous.
• Partially digested food in the stomach becomes acidic and is known as chyme.
What is the function of the small intestine?
The three main categories of nutrients that undergo digestion within the small intestine are proteins, lipids (fats) and carbohydrates. The small intestine is divided into duodenum, ileum and jejunum.
The intestinal enzymes such as invertase, maltase and lipase act upon partially digested proteins, carbohydrates and fats.
Proteins and peptides → amino acids
Lipids (fats) → fatty acids and glycerol
Some carbohydrates → simple sugars, or monosaccharides (e.g., glucose).
• Proteins, carbohydrates and fats are simplified into amino acids, glucose, fatty acids and glycerol in a liquid medium known as chyle.
• Specific structures called as villi in the small intestine increase its surface area to ensure efficient and rapid absorption of nutrients. Blood capillaries in the villi absorb nutrients and transport the food to all the cells in the body.
• Other carbohydrates pass undigested into the large intestine where they may, depending on their type, be broken-down by intestinal bacteria.
How do plants obtain nitrogen?
Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites. Or it is taken up as organic compounds which have been prepared by bacteria from atmospheric nitrogen. Atmospheric nitrogen is fixed by leguminous plants with the help of symbiotic bacteria present in the root nodules of these plants.
How will you prove that sunlight is essential for photosynthesis and the food prepared by green plants using photosynthesis is starch?
Let us do an activity to prove that sunlight is necessary for photosynthesis-
• We take a potted plant having green leaves and place it in a completely dark place for about three days to destarch its leaves. So, in the beginning of the experiment, the leaves do not have any starch in them.
• Take a thin strip of aluminium foil (or black paper) and wrap it in the centre of one leaf on both the sides (while the leaf is still attached to the plant). The aluminium foil should be fixed tightly to the leaf by using paper clips so that sunlight may not enter it from the sides. The aluminium foil should cover only a small part of the leaf so that the remaining part of the leaf remains uncovered and exposed to sunlight. We have covered the centre part of the leaf with aluminium foil so that sunlight may not fall on this covered part of the leaf.
• Keep this potted plant (with partially covered leaf) in bright sunshine for three to four days.
• Pluck the partially covered leaf from the plant and remove its aluminium foil. Immerse this leaf in boiling water for a few minutes. This will break down the cell membranes of leaf cells and make the leaf more permeable to iodine solution (so that it may reach the starch present inside the leaf cells).This leaf is now to be tested for the presence of starch. But before testing for starch, chlorophyll has to be removed from the leaf. This is because chlorophyll interferes in the test for starch due to its green colour.
• Put the plucked leaf in a beaker containing some alcohol. Place the beaker containing alcohol and leaf in a water bath. A water bath is being used here for heating alcohol because alcohol is a highly inflammable liquid.
• Heat the water in the bigger beaker (or water bath). Now, the alcohol in the smaller beaker will also get heated and start boiling soon. This boiling alcohol will extract (or remove) chlorophyll from the green leaf.
• Boil the green leaf in alcohol till all its green pigment 'chlorophyll' is removed. The leaf will now become almost colourless or pale (and the alcohol will turn green).
• Remove the colourless leaf from alcohol and wash it thoroughly with hot water to soften it and remove any chlorophyll which may be sticking to it.
• Place the colourless leaf in a petri-dish. Drop iodine solution over the decolourised leaf with the help of a dropper. Observe the change in colour of leaf.
• The middle part of leaf which was covered with aluminium foil does not turn blue-black on adding iodine solution showing that no starch is present in this middle part of the leaf. This is because sunlight could not reach the covered 'middle part' of the leaf due to which the covered 'middle part' of leaf could not do photosynthesis to make starch.
• The uncovered part of leaf (on both sides of the aluminium foil) which was exposed to sunlight turns blue-black on adding iodine solution showing that starch is present in this part of leaf. This means that the part of leaf which was exposed to sunlight could do photosynthesis to make starch.
Since the part of leaf which was covered and hidden from sunlight does not contain starch but the part of leaf which was exposed to sunlight contains starch, therefore, we conclude that sunlight is necessary for photosynthesis (to make food like starch).
From the above experiment, we actually get two conclusions-
(i) Sunlight is necessary for the process of photosynthesis, and
(ii) Leaves make starch as food by photosynthesis.
How do plants obtain carbon-dioxide for photosynthesis?
Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. Such pores are called stomata. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis. These pores are surrounded by ‘guard cells’. Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a function of the guard cells.
What are the important events that occur during the process of photosynthesis?
The following events occur during this process -
(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
(iii) Reduction of carbon dioxide to carbohydrates.
These steps need not take place one after the other immediately. For example, desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.
What is meant by photosynthesis?
It is the process by which autotrophs (green plants) make their own food from carbon dioxide and water which is converted into carbohydrates in the presence of sunlight and chlorophyll. During this process, oxygen gas is released.
What are the raw materials for photosynthesis?
The raw materials and other necessary items required for photosynthesis are Sunlight, Water, CO2 and Chlorophyll.
What are the two types of heterotrophic nutrition?
Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.
Saprophytic Nutrition: In saprophytic nutrition, the organism secretes the digestive juices on the food. The food is digested while it is still to be ingested. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Some insects like houseflies also follow this mode of nutrition.
Holozoic Nutrition: In holozoic nutrition, the digestion happens inside the body of the organism, i.e. after the food is ingested. Most of the animals follow this mode of nutrition. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.
What are the types of nutrition?
Types of Nutrition:
Autotrophic Nutrition: The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.
Heterotrophic Nutrition: The mode of nutrition in which an organism takes food from another organism is called heterotrophic nutrition. Organisms; other than green plants and blue-green algae follow heterotrophic mode of nutrition.
What are nutrients?
Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.
What is meant by life processes?
Various functions carried out by living beings; which are necessary to maintain and continue life are called life process. Following are the life processes in living beings:
• Nutrition
• Respiration
• Transportation of substances
• Excretion
• Movement
• Reproduction
What is the need for nutrition?
Organisms need energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.
When we are asleep we are not performing any activity still our life processes are going on. Why?
The maintenance functions of living organisms must go on even when they are not doing anything particular. That is why the life processes are going on even while we are asleep or not performing any activity.
What is meant by nutrition?
Nutrition is the process by which an organism obtains the food from its environment and utilizes it for various life processes like growth, replacement of tissues, energy etc.
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