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The living organisms are well-organised structures; they can have tissues, tissues have cells, cells have smaller components in them, and so on. Because of the effects of the environment, this organised, ordered nature of living structures is very likely to keep breaking down over time. If order breaks down, the organism will no longer be alive. So living creatures must keep repairing and maintaining their structures. Since all these structures are made up of molecules, they must move
Why are life processes needed?
Life processes are needed to maintain functions of living organisms like exchange of gases , assimilation of food, circulation of body fluids and removal of waste material
Life processes are:
(i) Nutrition (ii) Respiration
(iii) Transportation (iv) Excretion.
The life processes need to do:
(i) To provide food that provides energy and material required to sustain life. The process is called nutrition.
(ii) Respiration to supply oxygen to break down food (especially glucose) in the cells of organisms to release energy.
(iii) Transportation process for carrying food and oxygen from one place to another in the body. Also to transport wastes from body cells to excretory tissues.
(iv) Excretion process that removes the by-products produced during other life processes and carried to excretory tissues.
A single-celled organisms does not need specific organs for taking in food, exchange of gases or removal of wastes because the entire surface of the organism is in contact with the environment. Thus tha exchange of gases can take place by simple diffusion and there is no need of special organs.
An organism needs raw materials from outside are mainly.
(a) Food: Usually carbon based compounds to supply energy, materials like minerals, vitamins etc. for working and maintenance of cells/tissues.
(b) Water: To provide medium in the body to live and carry out all the metabolic reactions necessary for life.
(c) Oxygen: For respiration.
Processes essential for maintaining life are:
(i) Nutrition (ii) Respiration
(iii) Transportation (iv) Excretion.
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Autotroph |
Heterotroph |
|
1. They can make their own food from raw materials in presence of sunlight. |
1. They cannot make their own food. |
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2. They take in simple inorganic substances and change it into complex organic food. e.g., All green plants. |
2. They take in complex food and break it into simple food. e.g., All animals and fungi and non-green plants. |
(i) Energy and (ii) Nutrients.
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Give reasons for the following:
(a) Solar energy is available in plenty but animals cannot use it directly whereas the plants can.
(b) Life on earth depends on the sun.
(a) Animals do not have chloroplasts in the cells of their body. So, they cannot convert solar energy into chemical energy (food).
Plants have chloroplasts (containing chlorophyll pigment) in their cells which can trap solar energy for producing food during photosynthesis.
(b) All living things constantly need energy to be alive. They get the energy in the form of food. The food directly or indirectly comes from the green plants. The green plants trap light energy coming from the sun to produce food during photosynthesis.
Green plants also produce O2 during photosynthesis which is necessary for organisms for respiration.
A parrot is green in colour yet it is not an autotroph like green plants. What is the reason?
During photosynthesis the following events occur:
(i) Absorption of light energy by the chlorophyll pigment.
(ii) Conversion of light energy into chemical energy.
(iii) Splitting of water molecules into hydrogen and oxygen.
(iv) Reduction of carbon dioxide into carbohydrates.
State the part played by each of the following in photosynthesis:
(a) Water (b)Chlorophyll (c) Stomata.
(a) Water: Water (H2O) undergo photosynthesis in light reaction.
H2O → 2H+ + O + 2e–
O + O → O2 ↑
As a result ATP and NADPH are formed which are used in formation of carbohydrates from CO2. 
Water also releases O2 which is given out during photosynthesis.
(b) Chlorophyll: It traps solar (light) energy and utilises it in fixing oxides of carbon (CO2) and hydrogen (H2O) as carbohydrates.
(c) Stomata: They help in exchange of gases. Carbon dioxide needed in photosynthesis is taken in through stomata. Oxygen produced in photosynthesis is given out through stomata.
Cross-section of a leaf
The following activity can prove that chlorophyll is essential for photosynthesis.
Activity:
1. Take a potted plant with variegated leaves (leaves partly green and partly non-green), for example colens, croton, money plant.
2. Keep the plant in a dark place for 3 days. So that all the starch of leaves gets used
up.
3. Place the plant for 6 hours in sunlight.
4. Pluck a leaf from the plant. Mark the green areas of the leaf and trace them on a sheet of paper.
5. Boil the leaf first in water for a few minutes and then replace the leaf in a beaker containing alcohol. Place this beaker in a bigger beaker containing enough water. Heat till the alcohol begins to boil on a burner.
(Note: If you use a hot plate to heat the leaf in alcohol, there is no need to use water bath. Boil the leaf directly in alcohol on a hot plate. In case, you use burner, vapour of alcohol can catch fire from flame of the burner).
6. Boiling of the leaf in alcohol decolourizes the leaf.
7. Place decolourlized leaf in a petridish and pour .iodine solution on it.
To show that chlorophyll is necessary for photosynthesis
8. Take out the leaf and rinse off the iodine solution. Observe the colour of the leaf and compare this with the tracing of the leaf done in the beginning iodine solution on it. The portion of the leaf which was previously green has turned into dark blue colour while the non-green portion turns yellow (colour of iodine solution). The dark blue colour indicates the presence of starch (starch with idone turns blue black) while the yellow portion does not show any starch.
This proves that only chlorophyll containing cells synthesize starch. Hence chlorophyll is necessary for photosynthesis.
Structure of stomata-
The epidermis of the young shoot and leaves contains numerous minute pores called stomata. Each stomatal opening is surrounded by two cells known as the guard cells. The guard cells are living and contain chloroplasts. Their inner walls (wall towards opening) are thicker and outer walls thinner. The guard cells are surrounded by subsidiary cells or epidermal cells
Fig. 6.4. Structure of stomata. (A) Stomatal pour is open. (B) Stomatal opening is closed
Function of guard cells: The guard cells regulate the opening and closing of the stomatal pore. The unequal thickening of the outer and the inner layer of the guard cells allow the stomatal pore The guard cells swell when water flows into them causing the stomatal pore to open. Because inflow of water in guard cells causes the stretching and bulging of the walls leads to opening of the pore. When there is outflow of water from guard cells, the outer thin walls come to their original position resulting in closure of stomatal pore.
Major functions of stomata
(i) Stomata are essential for exchange of gases between the plant and the atmosphere— oxygen and carbon dioxide.
(ii) Normally, plants eliminate excessive water in the form of vapour through stomatal openings. The process is called transpiration.
(iii) Stomata regulate water loss.
The following activity proves that CO2 is essential for photosynthesis.
Activity:
1. Two potted plants of same species and of approximately of same size are taken . They are placed in a safe dark place for three days.
2. Each potted plant is placed on separate glass plates and a watch-glass/petridish containing KOH (potassium hydroxide solution) is kept by the side of one of the plants. The potassium hydroxide solution is used to absorb carbon dioxide.
3. Separate bell-jars are placed to cover both plants . The set-up is made air tight by applying vaseline to seal the bottom of the jars to the glass plates.
4. The plants are then placed in sunlight for 2–3 days.
5. After 2–3 hours, a leaf is plucked from each plant and boiledin water and then in alcohol separately to decolourize them.
6. Each decolourized leaf is placed in separate petridish and iodine solution is poured on each leaf.
7. The leaf of plant of set-up B which did not has potassium hydroxide turned deep blue black showing presence of enough starch. The leaf taken from set-up A either turned slightly blue or remains yellowish showing presence of a little amount of starch or no starch.
This activity proved that CO2 is essential for photosynthesis.
Set-up of apparatus to prove CO2 is essential for photosynthesis (A) with potassium hydroxide (B) without potassium hydroxide
Experiment to prove that sunlight is essential for photosynthesis
(i) A potted plant is taken and kept in dark for about 36 hours to destarch the leaves. Some portion of the leaf is covered with black strips on both the surfaces
(ii) The plant is then placed in sunlight for 6 hours.
(iii)The leaf is plucked, strips are removed and leaf is tested for starch by boiling it in water and alcohol for decolourizing it. The decolourized leaf is treated with iodine.
(iv) The part which was covered by black strips became yellow while the exposed part becames blue.
This shows that only lighted part synthesised food (starch). Hence we can conclude that light is necessary for photosynthesis.
To show that light is necessary for photosynthesis. (A) destarched leaf covered with light screen. (B) covered portion does not turn blue black while tested with iodine.
(i) Nitrogen.
(ii) Nitrogen is obtained by plants to take up it in the form of inorganic nitrates or nitrites. It may be taken up by plants as organic compounds which have been prepared by bacteria from atmosphere.
Internal structure of leaf chlorophyll;
The three modes of heterotrophic nutrition are:
(i) To break down of the food material outside the body and then absorb it. For example, bread moulds, yeasts and mushroom.
(ii) To take in whole material and break it down inside the body. For example, animals eating grass, fruits, insects, fish etc.
(iii) Parasitic nutrition - To derive nutrition from other plants or animals without killing them. For example, custuta (amar-bel), orchids, leeches, tape-worms etc.
The digestive system is different in various animals, so the food and the way nutrition is obtained differ.
In single celled-organisms, like amoeba, the food is taken in by the entire body surface and digested with the heklp of enzymes in the food vacuole. As the complexity in the body of animals increases, different parts specialised to perform different functions like ingestion, digestion, absorption digested food and utilisation.
Engulfing of Food: Amoeba obtains food by phagocytosis (a type of holozoic nutrition). Amoeba engulfs the food by forming pseudopodia.
Two pseudopodia start growing from opposite sides of food particle from amoeba. They completely encircle the food. The membranes of both the pseudopdia dissolve at the point of touching and the food is encaptured into the Amoeba (one cell body) in a bag known as food vacuole.
Digestion of Food: Inside the food vacuole, complex substances of the food are broken down into simpler one. The digested simple substances diffuse from food vacuole into cytoplasm.
The remaining undigested material is moved near the surface of the single-celled body of amoeba and thrown out.
Fig. 6.8. Engulfing of food by Amoeba
Paramoecium
Paramoecium takes in food at a specific point (through oral groove to mouth to gullet). Food such as bacteria or very small organisms are move to the specific spot (ingestion point) by the movement of cilia which are present on all over the single-celled body.
From the gullet a food vacuole is formed which start circulating in the endoplasm. During circulation food is digested by enzymes. The digested food diffuses into the cytoplasm and undigested food is thrown out through anal pore.
The process of mechanical and chemical break down of ingested complex food material into simpler soluble and absorbable molecules is called digestion. In man, it starts from mouth and continues uptill the small intestine.
The digestion of protein in man starts in stomach. The gastric juice of stomach contains pepsin enzyme. It converts complex protein molecules into smaller molecules–Peptones.
In duodenum, pancreatic juice enzyme Trypsin also acts upon protein molecules to convert it into Peptides and Peptones.
In ileum (a part of small intestine) intestinal juice enzymes convert simple molecules of proteins into amino acids. Proteins are absorbed as amino acids by the intestinal villi.
Differentiate between:
(i) Ingestion and digestion
(ii) Ingestion and egestion.
(i)
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Ingestion |
Digestion |
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1. The process by which organism takes in the food is called ingestion. |
The process by which complex food is mechanically and chemically broken down into simpler molecules, which can be absorbed, is called digestion. |
(ii)
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Ingestion |
Egestion |
|
1. The process by which organism takes in the food is called ingestion. |
The process of removal of undigested food from the body is known as egestion. In man, undigested food is removed through the rectum and the anus. |
Ingestion: The process of taking in of food is called ingestion.
Digestion: The process of breaking down of food mechanically and chemically into simpler and absorbable form is called digestion.
Absorption: The process of absorption of useful part of the digested food is called absorption.
Egestion: Removal of throwing out of the undigested food from the body is called egestion.
Liver is the largest gland present in our body. It does not secrete any digestive enzyme. It secretes bile juice which is very important for the digestion of food. Bile juice does two functions.
(i) Bile juice emulsifies fats and facilities digestion of fats.
(ii) It also helps to make the enzyme (semi-solid food coming from stomach into intestine) alkaline. In alkaline medium pancreatic and intestinal enzymes digest the food.
If liver does not secrete the bile juice, the digestion of food will not take place. That is why liver is called as largest digestive gland.
When digestion of food takes place within the cell it is called intracellular digestion e.g., amoeba.
When digestion of food takes place outside the cell body or in the alimentary canal, it is known as extracellular digestion e.g., man, frog etc.
Salivary glands secrete their secretion called saliva in the mouth cavity, There are three pairs of salivary glands located in the mouth.
Functions of saliva:
(i) Saliva moisten the food thus help in chewing of food by the teeth.
(ii) Human saliva contains an enzyme called salivary amylase that converts starch into simple sugar.
(iii) Saliva also helps in swallowing and easy passage of chewed food through the food canal.
Position of liver, gall bladder, bile duct, upper part of small intestine and pancreas
Function of hydrochloric acid are
(i) It makes the acidic medium which is necessary for the action of gastric enzymes like pepsin.
(ii) It kills most of the harmful bacteria present in the food.
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Functions of stomach
(i) The muscular walls of the stomach help in mixing the food thoroughly with more digestive juices.
(ii) The contraction of muscular walls also cause to break down comparative large food pieces into smaller pieces to expose larger surface of food for the action of gastric enzymes.
(iii) The exit of food from the stomach is regulated by a sphincter muscle which releases it in a small amounts into the small intestine for proper digestion.
(iv) Gastric glands present in the wall of the stomach release hydrochloric acid, pepsin enzyme and mucus.
(a) Hydrochloric acid kills bacteria and also makes the medium acidic for the action of pepsin enzyme.(b) Pepsin enzyme help in digesting proteins.(c) Mucous protects the inner lining of the stomach from the action of the HCl acid under normal conditions.
Activity to show action of saliva on starch
Procedure:
(i) 1 mL of 1% starch solution is taken in two test tubes and labelled as A and B.
(ii) 1 mL of saliva is added to test tube A. Nothing is added to test tube B (control).
(iii) The test tubes are left undisturbed in safe place and similar conditions for about 30 minutes.
(iv) After about 30 minutes, a few drops of dilute iodine solution is added to each test tube.
Observations:
(a) In test tube A there no change in iodine solution i.e., solution remain brownish that is the colour of iodine solution. It means that starch is not present.
(b) In test tube B, the solution turns blue black. It proves presence of starch.
Conclusion:
Saliva has enzyme which can digest starch and convert into other carbohydrate (sugars).
Conclusion
In test tube A the saliva acts on the starch and break them down. whereas in test tube B where no saliva is present the starch is not broken down.
Dental caries: Dental caries is the tooth decay that causes gradual sofetening of enamel and dentine.
It is caused when bacteria act on sugars and produce acids that softens or demineralises the enamel. It happens when masses of bacterial cells together with food particles stick to the teeth to form dental plaque. As plaque covers the teeth, saliva cannot reach the teeth surface to neutralise the acid.
Precaution:
to prevent tooth decay we should brush our teeth after eating to remove the plaque before the bacteria can produce acids.
If left untreated microorganisms may invade the tooth pulp, causing inflammation and infection.
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Name of the gland |
Secretion |
Site of action |
Enzymes |
Food acted upon |
End product/other functions |
|
1. Salivary gland |
Saliva |
Mouth(buccal cavity) |
Salivary amylase |
Starch |
(i) Maltose (sugar) |
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(ii) Saliva helps in moisting of food, chewing and swallowing |
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2. Gastric gland |
Gastric juice Stomach |
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(i) HCl |
— |
— |
kills bacteria and make the medium acidic. |
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(ii) Mucus |
Stomach |
— |
— |
Protects the inner lining of the stomach from the action of the acid. |
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(iii) Pepsin |
Stomach |
Pepsin |
Protein |
Simplified proteins |
|
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3. Liver |
Bile juice |
Duodenum (upper part of small intestine) |
— |
Fats |
Emulsific ation of fats into tiny globules. |
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4. Pancreas |
Pancreatic juice |
Duodenum |
(i) Trypsin |
Proteins |
Digestion into simpler parts like peptones and peptides |
The main product of anaerobic respiration are:
Ethyl alcohol (C2H5OH) in yeast.
Lactic acid (C3H6O3) in muscles and in some bacteria.
The process of incomplete break down of glucose in absence of oxygen is called anaerobic respiration. In this process only a small amount of energy is released. The end product of anaerobic respiration are etyhl alcohol ( in yeasts) and lactic acid (in muscles).
Bacteria and yeast respire anaerobically i.e., in absence of oxygen. Muscles of our body also carry out anaerobic respiration during excessive exercise or during short supply of oxygen.
During anaerobic respiration glucose is incompletely oxidised and broken down into lactic acid or alcohol.
(i) In muscles during short supply of O2:
(ii) In yeast:
Differentiate between:
(i) Respiration and Combustion
(ii) Aerobic and Anaerobic respiration.
(i)
|
Respiration |
Combustion |
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1. Respiration being a biological process occurs in living cells. |
1. Combustion is a non-biological process and hence it is non-cellular. |
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2. Respiration is the slow oxidation of organic substances (glucose) which results in stepwise release of energy. |
2. Combustion is a rapid oxidation of a substrate (like coal) and results in the release of the energy abruptly. |
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3. The heat evolved during respiration is stepwise, hence it does not harm the cells and organelles. |
3. The heat evolved during combustion is abrupt hence it raises the temperature which results in fire. |
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4. The heat energy evolved is either made available to the cells or is stored as chemical energy in the form of ATP. |
4. The heat energy evolved is made use of at the time of evolution and is not stored. |
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5. Respiration reactions are catalysed by enzymes. |
5. Enzymes are not used in combustion. |
(ii)
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Aerobic respiration |
Anaerobic respiration |
|
1. Aerobic respiration takes place in the presence of oxygen. |
1. It takes place in the absence of oxygen. |
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2. In aerobic respiration complete oxidation of glucose takes place. |
2. In anaerobic respiration the glucose molecule is incompletely broken down. |
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3. End products of aerobic respiration are CO2, water and energy.
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3. End product of anaerobic respiration are ethyl alcohol (or lactic acid) CO2 and a little energy.
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4. Large amount of energy is released i.e., 38 molecules of A.T.P. per glucose molecule. |
4. Small amount of energy is released i.e., 2 A.T.P. molecules per glucose molecule. |
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5. First step of aerobic respiration (glycolysis) takes place in cytoplasm while second (Kreb’s cycle) and third (Electron transport chain) steps take place in mitochondria. |
5. Complete anaerobic respiration occurs in cytoplasm. |
Briefly explain the process of aerobic cellular respiration.
Aerobic Respiration: Break down of food and release of energy takes place in each and every cell of the body. Aerobic respiration takes place in the following two steps:
First step: The first step does not require oxygen (anaerobic phase). The glucose is only partially broken down into an intermediate compound (pyruvic acid). In this step only a small amount of energy is released.
Second step: This step requires oxygen and, therefore, known as aerobic (in air). The intermediate compound formed by incomplete break down of glucose undergoes complete oxidation into CO2 and H2O. A large amount of energy (38 ATP) is released in this step. The complete oxidation of glucose takes place in the Mitochondria.
Overall reaction of aerobic respiration
C6H12O6 +6O2 → 6CO2 + 6H2O + 2830 kJ (38 ATP).
During respiration organisms use oxygen and give out CO2. Therefore, the air breathed in contains more percentage of oxygen and less percentage of carbon dioxide. The air breathed out contains more percentage of carbon dioxide and water vapour and less percentage of oxygen. A comparison of composition of air breathed in and breathed out is given in the table below:
Composition of Respired Air
|
Content |
Air breathed in (Approx) |
Air breathed out (Approx) |
|
Nitrogen |
79% |
79% |
|
Oxygen |
21% |
17% |
|
Carbon dioxide |
0.04% |
4% |
|
Water vapour |
Varies |
Saturated |
One loses approximately 400 cm3 of water daily from the body by breathing.
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Breathing |
Respiration |
|
1. It is a mechanical process. |
1. It is a bio-chemical process. |
|
2. It occurs only in some animals which possess breathing organs like trachea, gills and lungs. |
2. It occurs in all animals and plants cells in the mitochondria. |
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3. During breathing atmospheric air is taken into the body to obtain O2 and the CO2 is given out of the body. |
3. In the process of respiration the food (mainly glucose) is oxidised in the cells producing CO2, water and energy. |
ATP stands for Adenosine triphosphate.
Formation of ATP: The energy released during respiration process is used to make an ATP molecule from ADP (adenosine diphosphate) and inorganic phosphate (P).
When the terminal phosphate linkage in ATP is broken using water, the energy equivalent to 30.5 kJ/mol is released.
Observe fish in an aquarium. They open and close their mouths and the gill-slits (or the operculum which covers the gill-slits) behind their eyes also open and close. Are the timings of the opening and closing of the mouth and gill-slits coordinated in some manner?
(ii) Whether the number of times the fish opens and closes its mouth in a minute is faster than to the number of times you breathe in and out in a minute?
The timing of the opening and closing of the mouth and gill-slits in a fish are coordinated.
Reason: The water engulfed from the mouth is immediately pushed to gills for absorbing oxygen dissolved in water, into blood. It is then removed by gill-slites.
(ii) The number of times the fish opens and closes its mouth in a minute is much faster than the number of times we breathe.
Reason: The amount of dissolved oxygen in water is very low. The fish opens and closes its mouth (to push water over the gills) more number times so that more and more water passes over the gills. So that sufficient oxygen can be absorbed by the blood in the gills to meet the body's requirement.
Common features of respiratory organs (gills, lungs and skin).
(i) A large surface area to absorb sufficient oxygen.
(ii) Thin walls for easy exchange of respiratory gases by diffusion.
(iii) Rich blood supply for transport of gases.
Functions of Nasal Cavity
(i) Nasal cavity has external nostrils through which air is drawn into nasal cavity.
(ii) The nasal cavity is separated from oral cavity by a bony palate. So that air can breathe in even while we eat.
(iii) In nasal cavity the air is warmed to match the body temperature, moistened to avoid friction, and dust particles are removed by mucous secreted by mucous glands.
(iv) The hairs present in the nasal cavity filters the air .
(v) It provides passage to air from external nostrils to pharynx through internal nostrils.
Differentiate between:
(i) Inhalation and Exhalation
|
Inhalation |
Exhalation |
|
1. It is the process of taking air into the lungs. |
1. It is the process of giving out the air from the lungs. |
|
2. The external intercostal muscles contract, raising the ribs forward and upwards. |
2. The internal intercostal muscles contract and the ribs take their normal position. |
|
3. The muscles of the diaphragm contract and make it straight. |
3. The muscles of the diaphragm relax and it comes to its original dome shaped position. |
|
4. The abdominal muscles relax and allow compression of the abdominal organs. |
4. The abdominal muscles contract and the diaphragm pushes upward. |
Diagram showing organs involved in exchange of gases i.e. alveoli and network of capillaries.
The conditions essential for effective respiration are:
1. Presence of thin and permeable respiratory surface thin and permeable respiratory surfaces.
2. Rich supply of blood to the respiratory surface.
3. Passage for bringing oxygen to the respiratory surface and removing CO2 through the same passage.
4. Moist respiratory surface.
5. Presence of a circulatory system.
6. Presence of a respiratory pigment to carry out the respiratory gases (CO2 and O2) .
Functions of Nostrils hair: (i) The air passing through nostrils is filtered by the fine hairs that line the passage. So that the air going into the lungs is free from dust and other impurities.
Under normal conditions, the rate of breathing of a normal person is 15 to 18 times per minute. During vigorous exercise, the rate of breathing increases by about 20 to 25 times per minute.
Reason: During vigorous exercise, the demand of oxygen increasesto release more energy for extra work. Hence, there is increase in breathing rate to supply the extra oxygen needed.
In tissues oxygen is used up in respiration and carbon dioxide is released. So, there is less concentration of O2 and more concentration of carbon dioxide. On the contrary, blood coming from lungs has more concentration of oxygen and less concentration of carbon dioxide.
Due to difference in concentration, Oxygen diffuses from blood into tissues and Carbon dioxide from tissues into blood.
Carbon monoxide (CO) binds very strongly with haemoglobin of red blood cells which is main carrier of O2 from lungs to the body cells. When all the haemoglobin of red blood cells gets bonded with carbon monoxide, there is none left for the transport of oxygen. Lack of oxygen in the body or cells can cause death.
Breathing comprises of inspiration and expiration of air.
1. Inspiration: During inspiration the volume of the thorax is increased by two movements, for intake of air.
(a) The muscles of the diaphragm contract and becomes flattenned.
(b) The lower ribs are raised upward and outwards by the contraction of the intercostal muscles which run obliquely from one rib to the next rib. The chest cavity enlarges, the air pressure in the lungs is decreased, air rushes into the lungs.
2. Expiration: Breathing out of air, results mainly from relaxation of muscles of the ribs and diaphragm. The chest cavity is reduced and air is forced outward through the nose and trachea.
The organisms that live in water use oxygen dissolved in surrounding water. Since air dissolved in water has fairly low concentration of oxygen, the aquatic organisms have much faster rate of breathing. Whereas the terrestial organisms take oxygen from the oxygen-rich atmosphere, through respiratory organs. So, they have much less breathing rate than aquatic organisms.
Different organisms oxidise glucose by different methods, some organisms use oxygen (Aerobic respiration) to break down the glucose into carbon-dioxide and water while others do not use oxygen ( Anaerobic respiration)to oxidise glucose
In both the process the first step of break down of glucose (6 carbon molecule) takes place in the cytoplasm of cells of all organisms and gives a three carbon molecule compound called Pyruvate.
Further break down of pyruvate takes place in different manners in different organisms.
(i) Anaerobic respiration: This process takes place in absence of oxygen e.g., in yeast during fermentation. In this case pyruvate is converted into ethanol and carbon dioxide.
(ii) Aerobic respiration: In aerobic respiration break down of pyruvate takes place in presence of oxygen to give rise 3 molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than anaerobic respiration.
(iii) Lack of oxygen: Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compound). Formation of lactic acid in muscles causes cramp.
Break down of glucose by various pathways during cellular respiration.
(a) Transport of oxygen: The oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. In human beings, the respiratory pigment, called haemoglobin present in the red blood corpuscles carries oxygen to different tissues of the body.
(b) Transport of carbon dioxide: Carbon dioxide is more soluble in water. Hence is mostly transported from body tissues in the dissolved form in our blood plasma to lungs. Where it diffuses from blood to air in the lungs.
The lungs of human beings are designed to maximise the area for the gaseous exchange in the following way
i. In the lungs, the air passage (wind pipe) is divided into smaller tubes, called bronchi which in turn form bronchioles.
ii. The bronchioles which terminate in balloon-like structures, called alveoli .
iii. The alveoli present in the lungs provide maximum surface for exchange of gases. The alveoli have very thin walls and contain an extensive network of blood vessels to falicitate exchange of gases.
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Blood is a connective tissue. It has the following components:
1. Plasma: It is a colourless fluid matrix. It contains water and proteins.
2. Red Blood Corpuscles (RBC).
3. White Blood Corpuscles (WBC).
4. Blood Platelets.
Explain the followings:
(i) Blood pressure.
(ii) Systole pressure and diastole pressure. How they are expressed.
(iii) Name of the instrument which is used to measure blood pressure.
(iv) Higher blood pressure and its harmful effects.
(i) Blood pressure: The force that blood exerts against the wall of a blood vessel is called blood pressure. The blood pressure is much greater in arteries than veins.
(ii) (a) Systole pressure: The blood pressure inside an artery during ventricular systole (contriction) is known as systole pressure.
(b) Diastolic pressure: The blood pressure in artery during ventricular diastole (relaxation) is known as diastolic pressure.
This is expressed as systolic pressure/diastolic pressure. The normal systolic pressure is 120 mm of Hg and the diastolic pressure is 80 mm of Hg. It expressed as 120/80.
(iii) Sphygmometer instrument is used to measure blood pressure. As shown in the figure for understanding.
Fig. 6.21. Measurement of blood pressure by sphygmometer
Note: Figure is given for enrichment.
(iv) High blood pressure: Higher blood pressure is also known as hypertension. Hypertension is caused by the constriction of arterioles. It results in increased resistance to blood. Harmful effects of high blood pressure: It can lead to rupture of an artery and internal bleeding. If untreated may cause death of the patient.
(i) What is the meaning of double circulation?
(ii) Draw representative line diagram of double circulation.
(ii) Representative line diagram of double circulation.
Double circulation of blood in man
|
Blood |
Lymph |
|
1. Blood is red due to presence of haemoglobin . |
1. The lymph is colourless because it does not have haemoglobin. |
|
2. Blood flows in blood vessels. |
2. The lymph bathes the body tissues. |
|
3. Blood flows from heart to body organs and returns to heart. |
3. The lymph flows from the tissues to the heart. |
|
4. Blood contains RBC, WBC, platelets and plasma. |
4. Lymph does not contains RBC. |
Blood consists of liquid medium called plasma. It contains several salts, glucose, aminoacids, proteins, hormones, digested and excretory products. Serum is blood plasma from which the blood clotting protein-fibrinogen is removed. In the plasma of blood the following three components are found:
(i) Red blood cells or erythrocytes.
(ii) White blood cells or leucocytes.
(iii) Thrombocyte (platelets).
(i) Red blood cells or spherical, disc shaped. Human RBC’s are biconcave and are devoid of nucleus. Their number is about 5 million per cubic mm of blood. Their red colour is due to the presence of a pigment haemoglobin. Main function of RBC’s is to transport oxygen with the help of haemoglobin.
(ii) White blood cells or leucocytes do not have a definite shape and possess a nucleus. These are bigger than RBC’s and are of five types. Main function of leucocytes is to protect the body from micro-organisms and provide immunity to body.
(iii) Blood platelets or thrombocytes are small bodies numbering about 5,00,000 per cubic mm of blood. They perform an important function of forming a clot on the skin in the event of an injury and thus prevent excess flow of blood from the body.
Human blood cell
Blood performs the following important functions:
(i) Respiratory function: Blood transports oxygen from the lungs to body organs and CO2 from body organs to lungs.
(ii) Transport of food: Blood carries digested food to different cells of the body.
(iii) Transport of hormones: Hormones are transferred from their place of secretion to their place of action through blood.
(iv) Thermoregulation: Blood also maintains proper body temperature.
(v) Regulation of water and balance of acid and base: Blood brings about the balance of acid, base and regulates water contents of the body.
(vi) Removal of metabolic wastes: Blood carries various metabolic wastes to kidney, skin and intestines for excretion.
(vii) Besides the above functions blood also protects our body against micro-organisms.
(viii) Blood also helps in the formation of a clot in the event of an injury to prevent further loss of blood.
White blood corpuscles are called soldiers of the body because:
(i) They protect the body from infections.
(ii) They are capable of squeezing out of capillaries and disarm pathogens.
(iii) They also manufacture antibodies which are responsible for Immunity.
The four chambers of heart are:
(i) Left Ventricle.
(ii) Right Ventricle.
(iii) Left Atrium.
(iv) Right Atrium.
|
Artery |
Veins |
|
1. Arteries carry blood from the heart to the body organs. |
1. Veins carry blood from body organs to the heart. |
|
2. Arteries have thick walls. |
2. Veins have comparatively thin walls. |
|
3. Blood flows with a force in the arteries. |
3. Blood flow is very slow and without any force. |
|
4. There are no valves in the arteries. |
4. Veins have valves which allow the flow of blood in one direction only and check and back flow. |
A—T.S. of Artery. B—T.S. of Vein
The gaseous exchange takes place in the alveoli. Each alveolus is surrounded by a network of blood capillaries. Both alveoli and blood capillaries have a very thin single epithelial layer.
The blood contained in the capillaries of the lungs flows from the heart to the lungs. It contains very little oxygen and much of carbon dioxide. On the other hand air flowing into the alveoli contains much of oxygen (21%) and very little of CO2 (0.03%). Therefore, a two way diffusion takes place i.e., oxygen diffuses into the blood from alveoli and CO2 flows out from the blood into the alveoli. This gaseous exchange occurs within few seconds because of an extensive surface area provided by the alveoli in the lungs.
Gaseous exchange in the lungs
Human heart is a muscular organ situated in the centre of the thoracic cavity with its lower end tilted towards left. It consists of four chambers - two auricles which receive blood and
two ventricles which pump blood to different parts of the body.
Heart beat: The heart beats is a rhythmic pulsation of the heart, including one complete systole and diastole. The heart beat occurs due to contraction and relaxation of its atrium and ventricles at an average rate of 72 times per minute.
Cross-section of human heart
Blood is a fluid. It is a connective tissue.
Composition: Blood contains the following components:
(i) Plasma: It is a fluid matrix. It is colourless and contains a lot of water, many proteins and salts.
(ii) Red blood corpuscles (RBC): Blood looks red because of the red coloured pigment haemoglobin present in Red blood cells. RBCs are circular in shape and do not contain nuclei.
Blood cells
(iii) White blood corpuscles (WBC): These are lesser in number than the red blood cells. They are white or colourless cells. They protect from infection.
(iv) Blood platelets: Blood platelets are fragments of cells and they do not possess nuclei. They help in clotting of blood.
Lymph: Lymph is a circulatory fluid which also helps in transportation. This is also called tissue fluid. It is formed when some amount of plasma, proteins, inorganic salts and white blood cells pass through the pores present in the walls of capillaries into intercellular spaces in the tissues. The lymph similar to plasma except that tissue fluid is colourless and contains very less proteins.
From intercellular spaces, lymph goes into lymphatic capillaries. Lymphatic capillaries join to form large lymph vessels which finally open into larger veins. Lymph flows only in one direction, that is from tissues to heart through veins.
Arterial capillaries → Lymph in the intercellular spaces → Lymph capillaries → Lymph vessels → Larger veins → Heart
[Note: Lymphatic system consists of lymph capillaries, lymph vessels, lymph nodes and lymph glands (such as tonsils].
Functions of lymph
(i) Lymph carries digested and absorbed fats from small intestine to different tissues of the body.
(ii) It drains excess fluid from extra cellular space back into the blood.
(iii) Lymph protects tissues/cells from infection.
(iv) It also removes waste products from the body cells to drain into blood.
Artery: Arteries are the thick walled blood vessels. They carry blood from the heart to the different organs of body. They have no valve and blood flows with force in them.
Veins: Veins are thin walled blood vessels. They carry blood from different parts of body to heart. They have valves.
Capillaries: Capillaries are thin walled and extremely narrow. Exchange of food materials gases and wastes takes place through capillaries.
During photosynthesis in a leaf, the CO2 present in cells (cytoplasm) is being used up and fixed as carbohydrates. As a result, the concentration of CO2 in cell-cytoplasm falls. So CO2 present in intercellular spaces diffuses into cells. Consequently, a diffusion gradient between the air and the intercellular spaces set up and CO2 diffuses from the atmosphere into intercellular spaces and then into cells.
Movement of CO2 in green plant cells during day-light.
Cell → intercellular spaces → stomata → atmosphere.
1. Transpiration is the process of loss of water from the plant body through the stomata of the leaves. Transpiration causes movement of water and dissolved minerals from roots to leaves through xylem cells.
2. Translocation is the process of the movement of dissolved substances (prepared food) from leaves to roots and different parts of the plant body through Phloem cells.
Transport of water and mineral in plants:
Water and minerals are transported by the xylem tissue. Roots absorb water due to the difference in the concentration of the ions, mineral are dissolved in it. The water and the minereals move upto leaves from roots through tracheids and vessels which are types of xylem cells.
Transport of food: The food like sugar is synthesised in the leaf. The transport of food takes place through phloem from one part to the other parts in the plants. Food is transported in a dilute aqueous solution. This process is called translocation.
Name the two kinds of cells of xylem.
The two kinds of cells of xylem are:
(i) Trachieds
(ii) Vessels.
Transpiration is the process which causes movement of water and minerals from roots through xylem up to the top of a tall tree.
Transpiration mainly takes place through stomata in the leaves. The loss of water from the intercellular space of leaves tissue cause a drop in turgor pressure of cells. These cells in turn take water from xylem tissue. The xylem tubes act as single continuous column. When leaf tissues take water from xylem column there is drop in pressure at that point. Evaporation of water molecules from the cells of a leaf creates a suction pressure which pulls water from the xylem cells of roots. This leads to an uptake of water from the soil through roots.
The whole sequence occurs as shown below:
The whole event causes rise of water and dissolved minerals up to the top of a tall tree.
|
Diffusion |
Osmosis |
|
1. It is the movement of particles from the region of higher concentration to low concentration through the pores of medium. |
1. It is a special form of diffusion where water molecules move from its higher concentration to its lower concentration across a semi-permeable membrane. |
|
2. It is rapid in gases, slow in liquid and very slow in solids. |
2. It occurs onli in liquids. |
|
3. The rate of diffusion depends upon the intensity of gradient. Examples: |
3. Its rate does not depend upon the gradient. Examples: |
|
4. Exchange of O2 and CO2 in plants. |
4. Absorption of water and mineral solution |
|
2. Dispersion of CuSO4 and KMnO4crystal in water. |
Absorption of water from the soil by the root hairs. |
The lower side of plant leaf contains special holes or pores called stomata. They are formed between two guard cells. Light intensity and rate of loss of water are the two factors that control the stomatal opening. As photosynthesis proceeds rapidly the concentration of CO2 in the leaf drops while that of sugar increases. The increase in the sugar level causes a concentration difference due to which the guard cells take up water from surrounding cells . This causes the guard cells to curve due to uneven thickening of the inner and outer layer of gurad cells. This causes opening of the stomatal pore between them.
Fig. 6.29. Opening and closing of stomata
The transport system (called circulatory system) in human beings mainly consists of heart, blood and blood vessels.
Functions of component of circulatory system:
(i) Heart: The heart is a muscular organ which pumps blood to the different parts of the body. It receives deoxygenated blood from the body parts and pump it to lungs which enriches it with oxygen. It receives purified blood from lungs and pumps it to all the parts of the body.
(ii) Blood: Blood is fluid connective tissue it consists of a fluid known as plasma in which the cells are suspended, such as white blood cells and red blood cells. Plasma transports food, carbon dioxide and nitrogenous wastes (urea and uric acid) in dissolved form. Red blood cells transport oxygen. Blood also transport many other substances like hormones, salt etc. Platelets present in the blood stop bleed from injuries by forming blood clots.
(iii) Blood vessels: Blood vessels form a closed network of tubes to reach all the tissues. Thus, the blood pushed by the heart flows in the blood vessels (arteries) and also comes back to the heart in the blood vessels (veins).
The transport system in highly organised plants consists of two components:
(i) Xylem: Consists of vessels, tracheids and other xylem tissues. The interconnected vessels and tracheids form a continuous system of water conducting channels reaching all parts of the plant. Xylem conducts water and dissolved minerals absorbed from the soil.
(ii) Phloem: Consists sieve tubes and companion cell which conduct soluble products of photosynthesis from leaves to different parts of the plant body. This transportation of prepared food material through pholem is called translocation.
The water and minerals is transported by xylem in the plants. the process of transpiration also plays a major role in the tranportation of water and mineral.
Xylem vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant.
At the roots, cells in contact
with the soil actively take up ions. This creates a difference in the concentration of these ions between the root and the soil. Water, therefore, moves into the root from the soil to eliminate this difference. There is steady movement of water into root xylem, creating a column of water that is steadily pushed upwards.
|
Excretion |
Egestion |
|
Removal of waste products formed in the body due to its metabolic activities is called excretion. |
Elimination of undigested material through the rectum and the anus is called egestion. |
From the glomerulus filterate glucose, salts, vitamins, water and other useful substances are selectively reabsorbed by the tubule and sent back into the blood.
If these useful substance are not reabsorbed from the filtered liquid, they may pass out of the body in the urine. Constant elimination of water, glucose and other useful substances may health related issues and may cause death of the person in severe cases.
Function: The nephron performs two functions:
(i) Filtration: In the glumerulus, the blood plasma called serum gets filtered under pressure. The filterate contains water, glucose, salts and nitrogen containing compounds. It gets collected in the Bowman’s capsule. The blood cells and large molecules like proteins remain in the blood. From Bowman’s capsule the filterate passes into nephron long tubule.
(ii) Selective reabsorption: From the filterate, filtered by the glomerulus, useful substances like glucose, salts, vitamins, water etc. are reabsorbed by the tubule and passed back into the blood.
The remaining filterate forms the urine and taken to urethera. The urethera carries urine to urinary bladder for disposal.
The urinary system of man is concerned with the excretion of nitrogenous wastes. It consists of:
(a) a pair of kidneys (b) ureters (c) urinary bladder and urethera.
Kidneys are bean shaped and are located in the abdominal region on either sides of vertebral column. From each kidney a tubular structure emerges which is called ureter. The ureter travels downwards and open, the sac like structure in the urinary bladder, which stores urine. Besides the two openings of ureters in this bladder it has another opening which opens in the urethera. Urethera forms the passage of urine outside.
Excretory system in human beings
The two-vital functions of human kidney are:
(i) Kidneys act as a excretory organ in human body to remove toxic wastes from the body.
(ii) Kidneys also control and maintain water levels in the body.
Artificial kidneys consists of a number of tubes with semi-permeable lining (selective permeable membrane). These tubes are suspended in a tank filled with dialysing fluid. The dialysing fluid has the same osmotic pressure as blood. This fluid does not contain nitrogenous wastes.
Working: The blood of the patient is passed through dialysing tubes. As blood passes through tubes, the waste products (e.g., urea) from the blood pass into dialysing fluid by diffusion. The purified blood is pumped back into the patient artificial kidney does filtration but no reabsorption, like kidney.
Fig. Dialysis
Structure of Nephron: Nephron is the functional unit of kidney. It consists of a tubule which is connected with collecting duct at one end and a cup shaped structure at the other end. This cup-shaped structure is called Bowman’s capsule. Every Bowman’s capsule contains a cluster of capillaries, called Glomerulus, within the cup-shaped structure. The blood enters into glomerulus through afferent arteriole of renal artery and leaves it through efferent arteriole.
Fig. Structure of nephron
Functioning of nephron:
Filtration of blood takes in Bowman’s capsule from the capillaries of glomerulus. The filterate passes into the tubular part of the nephron. This filterate contains glucose, amino acids, urea, uric acid, salts and a major amount of water. Reabsorption: As the filterate flows along the tubule useful substances such as glucose, amino acids, salts and water are selectively reabsorbed into the blood by capillaries surrounding the nephron tubule. The amount of water reabsorbed depends on the need of the body and also on the amount of wastes to be excreted. The filterate which remained after reabsorption is called urine. Urine contain dissolved nitrogenous waste i.e., urea and uric acid, excess salts and water. Urine is collected from nephrons by the collecting dust to carry it to the ureter.
To get rid of excretory products plants use the following ways:
(i) Excess water is lost by Transpiration.
(ii) Many plants waste products are stored in vacuoles of the cells.
(ii) Some waste products are stored in the leaves. They are removed as the leaves fall off.
(iii) Some waste products such as resins and gums are stored, especially in nonfunctional old xylem.
(iv) Some waste products such as tanins, resins, gums are stored in bark, thereby removed as the peeled off.
(v) Plants also excrete some waste substances through roots into the soil around them.
(vi) Oxygen is lost while the stomata opens for taking in carbon-dioxide.
The amount of urine largely depends on the amount of water reabsorbed. The amount of water reabsorbed by the nephron tubule depends on.
(i) The amount of water in the body .
When water is abundant in the body tissues, large quantities of dilute urine is excreted out. When water is less in quantities in the body tissues, a small quantity of concentrated, with less water content, is excreted.
(ii) The amount of dissolved wastes, especially nitrogenous wastes, like urea and uric acid and salts in the body. When there is more quantity of dissolved wastes in the body, more quantity of water is required to excrete them. So, the amount of urine produced increases. When the amount of these substances in the body is less then less urine is produced.
(iii) The amount of urine produced is also regulated by certain hormones which control the movement of water and Na+ ions into and out of the nephrons.
The process of intake as well as utilisation of nutrients by an organism is called nutrition.
Mouth helps in breaking the food into smaller molecules mechanically by teeth( chewing). It also breaks the food into simpler forms , as saliva acts on the the food it breaks down starch by the action of enzyme salivary amylase.
The three types of blood vessels are:
(i) Arteries
(ii) Veins
(iii) Capillaries.
C.
excitation of chlorophyllB.
excitation of chlorophyllA.
Bile juice secreted by liverB.
hypertensionD.
Small intestine.B.
herbivoresC.
cytoplasmA.
increase in the transpirationA.
higher conc. of water molecules to its lower conc.D.
availability of soil water.A.
transpiration exceeds water absorptionD.
valves to control direction of flow of blood.D.
passive absorption.It contains fewer corpuscles per unit volume
C.
It has a lower concentration of crystalloidsA.
glomerular Alteration, tubular reabsorption, tubular secretionD.
a part of uriniferous tubule and is a site of Alteration of various blood constituents during the formation of urine.B.
dental carriesD.
nitrogenous waste products which on accumulation become poisonous.simple sugar
pancreas
acid
respiration
,muscles
photosynthesis
,no
nitrogenous
mineral
,water
After a vigorous exercise you may experience cramps in your leg muscles. Why does it happen?
What do the following transport?
(i) xylem (ii) phloem (iii) pulmonary vein (iv) vena cava.
(i) Transports water and dissolved minerals implants.
(ii) Transports prepared food in plants.
(iii) Transports oxygenated blood from lungs to left ventricle of hearts.
(iv) Transports deoxygenated blood from body to right ventricle.
Alveoli are designed to maximise the exchange of gases in the following way:
(i) The alveoli are thin walled and richly supplied with a network of blood vessels to facilitate exchange of gases between blood and the air filled in alveoli.
(ii) Alveoli have balloon like structure. Thus, provide maximum surface for exchange gases.
A.
transport of waterD.
all of the above.Digestion of fat takes place in the small intestine.
Digestion of Fat: The fats are present in the form of large globules in the small intestine. Fats digesting enzymes are not able to act upon large globules efficiently. Bile juice secreted by the liver is poured in the intestine along with pancreatic juice. The bile salts present in the bile juice emulsify the large globules of fats and break them down into fine globules to provide larger surface area to act upon by the enzymes.
Lipase enzyme present in the pancreatic juice causes break down of emulsified fats. Glands present in the wall of small intestine secrete intestinal juice which contains lipase enzyme that converts fats into fatty acids and glycerol. Small Intestine: Region of digestion of fats:
Role of saliva in digestion of Food:
(i) The saliva contains salivary amylase enzyme that breaks down starch which is a complex molecule to simple sugars.
(ii) The saliva moisten the food that help in chewing and breaking down the big pieces of food into smaller ones. So, that salivary amylase can digest the starch efficiently.
Necessary conditions for autotrophic nutrition:
(i) Presence of chlorophyll in the living cells.
(ii) Supply of water to green parts or cells of the plant either through roots or by surrounding environment.
(iii) Availability of sufficient of sunlight to provide light energy required to carry out photosynthesis.
(iv) Sufficient supply of carbon dioxide which is one of the important component for the formation of carbohydrates during photosynthesis.
|
Aerobic respiration |
Anaerobic respiration |
|
1. Aerobic respiration takes place in the presence of free oxygen. |
1. It takes place in the absence of oxygen. |
|
2. In aerobic respiration complete oxidation of glucose takes place. |
2. In anaerobic respiration the glucose molecule is incompletely broken down. |
|
3. End products of aerobic respiration are CO2, water and energy. |
3. End product of anaerobic respiration are ethyl alcohol (or lactic acid) CO2 and a little energy. |
|
|
|
|
4. Large amount of energy is released i.e., 38 molecules of ATP per glucose molecule. |
4. Small amount of energy is released i.e., 2 ATP molecules per glucose molecule. |
|
5. First step of aerobic respiration (glycolysis) takes place in cytoplasm while second (Kreb’s cycle) and third (Electron transport chain) steps take place in mitochondria. |
5. Complete anaerobic respiration occurs in cytoplasm. |
Organisms which use anaerobic respiration are yeasts, bacteria and parasites like tape worm (Taemia), Ascaris etc.
The alveoli are designed to maximise the exchange of gases in the following way:
(i) The alveoli are thin walled and richly supplied with a network of blood vessels to facilitate exchange of gases between blood and the air filled in alveoli.
(ii) Alveoli have balloon like structure. Thus, provide maximum surface for exchange gases.
Double circulation: In human beings the blood goes through the heart twice during each cycle i.e., the blood passes through the human heart two times to supply once to the whole body. So, it is called double circulation of blood.
The double circulation of blood includes
(i) Systemic circulation and
(ii) Pulmonary circulation
(i) Systemic circulation: It supplies oxygenated blood from left auricle to left ventricle. Thereby pumped to various body parts. The deoxygenated blood is collected from the various body organs by the veins to pour into vena cavae and finally into right atrium (auricle). Right atrium transfers the blood into the right ventricle.
(ii) Pulmonary circulation: The deoxygenated blood is pushed by the right ventricle into the lungs for oxygenation. The oxygenated blood is brought back to left atrium of the human heart. From left atrium the oxygenated blood is pushed into the left ventricle. The left ventricle pumps oxygenated blood into arota for systemic circulation.
Double circulation is necessary : The right side and the left side of the human heart is useful to keep deoxygenated and oxygenated blood from mixing. This type of separation of oxygenated and deoxygenated blood ensures a highly efficient supply of oxygen to the body. This useful in case of humans which constantly energy to maintain their body temprature.
Double circulation of blood in human heart
Transport of materials
|
S.No. |
Xylem |
Phloem |
|
1. |
Xylem conducts water and dissolved mineral from roots to leaves and other parts. |
Phloem conducts prepared food material from leaves to other parts of plant in dissolved form. |
|
2. |
In xylem, the transport of material take place through vessels and tracheids which are dead tissues. |
In phloem, transport of material takes place through sieve tubes with the help of companion cells, which living cells. |
|
3. |
In xylem, upward movement of water and dissolved minerals is mainly achieved by transpiration pull. It is caused due to suction created by evaporation of water molecules from the cells of a leaf. |
In translocation, material is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure that moves the material in the phloem to tissues which have less pressure. |
|
4. |
Movement of water is achieved by simple physical forces there is no expenditure of energy. So ATP molecules are not required. |
The translocation in phloem is an active process and requires energy. This energy is taken from ATP. |
Comparison between Alveoli and Nephron
|
S.No. |
Alveoli |
Nephron |
|
1. |
Alveoli have thin walled balloon like structure. Surface is fine and delicate. |
Nephron have thin walled cup shaped structure attached with thin walled tubule. |
|
2. |
Alveoli are supplied with extensive network of thin walled blood vessels i.e., capillaries for exchange of gases. |
Bowman’s capsule is supplied with a cluster of capillaries, called glomerulus for filtration A network of blood vessels around the tubular part of nephron for reabsorption of useful substances and water. |
|
3. |
Alveoli increase surface area for diffusion of CO2 from blood to air and O2 from air to blood. |
Nephrons also increase surface area for filtration of blood and reabsorption of useful substances and water from, filtrate leaving behind urine. |
|
4. |
Alveoli only provide surface for exchange of gases in the lungs. |
Tubular part of nephron also carries the urine to collecting duct. |
|
5. |
Alveoli are very small and a large number of them are present in each lung. |
A large number of nephron, basic filtration unit, are present in each kidney. |
(i) Light energy
(ii) Chemical energy.
Curve A — Anaerobic respiration.
Curve B — Aerobic respiration.
(i) Draw the diagram of heart and label its four chambers.
(ii) Construct a table to show the functions of these four chambers.
(i)
Cross-section of human heart
|
S. No. |
Name of chamber |
Function |
|
1. |
Left Atrium |
Receives oxygenated blood from lungs through pulmonary vein and pours it into left ventricle. |
|
2. |
Right Atrium |
Receives deoxygenated blood from various body parts through vena cava and pours it into right ventricle. |
|
3. |
Left Ventricle |
Pumps oxygenated blood to various parts of body through aorta. |
|
4. |
Right Ventricle |
Pumps deoxygenated blood into lungs through pulmonary artery. |
Transpiration is the evaporation of water from the stomata of the leaves. It is a process which causes movement of water and minerals from roots through xylem up to the top of a tall tree.
Transpiration mainly takes place through stomata in the leaves. The loss of water from the intercellular space of leaf tissue cause a drop in turgor pressure of cells. These cells in turn take water from xylem tissue. The xylem tubes act as single continuous column therefore when leaf tissues take water from xylem column there is drop in pressure at that point. Evaporation of water molecules from the cells of a leaf creates a Suction which pulls water from the xylem cells of roots. This leads to an uptake of water from the soil through roots.
The whole sequence occurs as shown below:
The whole event causes rise of water and dissolved minerals up to the top of a tall tree.
In test tube A—carbon dioxide and alcohol because anaerobic respiration will take place as the oil layer will not allow air to enter the solution.
In test tube B—carbon dioxide and water formed due to aerobic respiration.
Write one feature which is common to each of the following pairs of terms/organs.
(i) glycogen and starch (ii) chlorophyll and haemoglobin
(iii) gills and lungs (iv) arteries and veins
(i) Glycogen and starch both are storage carbohydrates.
(ii) Both are pigments.
(iii) Both are respiratory organs.
(iv) Arteries and veins are vessels that transport blood.
What are the differences between autotrophic nutrition and heterotrophic nutrition?
|
Autotrophic nutrition |
Heterotrophic nutrition |
|
1. Food is synthesized from simple inorganic raw materials like CO2, sunlight and water. |
1. Food is obtained and broken down into simple molecules. |
|
2. It is mainly of two types – photoautotrophic and chemo autotrophic nutrition. |
2. It may be holozoic, saprozoic, parasitic, etc. |
|
3. They depend on solar energy directly. |
3. They depend on solar energy indirectly. |
|
4. Presence of pigment like chlorophyll is necessary. |
4. Presence of pigment is not necessary. |
|
5. Example – plants and certain bacteria. |
5.Examples- All animals |
Where do plants get each of the raw materials required for photosynthesis?
The raw materials for photosynthesis are carbon-dioxide, water and light energy. Plants get these raw materials in the following ways:
Carbon-dioxide is obtained from the air through the stomata.
Water is absorbed from the roots.
Light energy is obtained from the Sun and absorbed by the chlorophyll pigment of the leaves.
What is the role of the acid in our stomach?
The hydrochloric acid in our stomach provides the necessary acidic conditions for the enzyme pepsin to work. The inactive pepsinogen is converted to active pepsin by the acid. The acid in the stomach also provides protection from harmful micro-organisms.
What is the function of digestive enzymes?
Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. help in the breaking down of complex food particles into simple ones. These simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.
How is the small intestine designed to absorb digested food?
The small intestine has numerous finger-like projections called villi on its inner lining. The villi increase the surface area for absorption. They are richly supplied with blood vessels and the absorbed food and nutrients are transferred to blood, which takes the absorbed food to each and every cell of the body. Thus, small intestine eficiently absorbs digested food.
How are water and animals transported in plants?
In plants the water is transported through the xylem tissue system. The xylem tissue, vessels and tracheids of the roots stems and leaves are interconnected to form a continuous system of water-conducting channels that transports water to all parts of the plant. The water and minerals are taken up from the soil by the roots. The uptake of ions at the roots creates a difference in the concentration of these ions between the root and the soil. Thus, water moves into the root from the soil to eliminate this difference. This ensures that there is a steady movement of water into root xylem, creating a continuous column of water. The root pressure is not enough to transport the water to the high parts of the plant. The transpiration from the leaves creates a Transpiration Pull, which helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves and ensure water and minerals transport even to the highest part of the plant.
Dry raisins were soaked in water for 2 hours, to determine the percentage of water absorbed by raisins. Before final weighing of swollen raisins, the extra water left on the surface of soaked raisins was removed by:
gently rubbing with cotton cloth
hot air blower
dry cotton wool
filter paper
D.
filter paper
In order to remove the excess water, raisins are dried on a piece of filter paper after being soaked in water.
While performing the experiment with raisins to determine the percentage of water absorbed by them, a student made following measurements:
Mass of water in the beaker = 40 g
Mass of raisins before soaking = 5 g
Mass of raisins after soaking for 2 hours = 8 g
Mass of water left in the beaker after the experiment = 35 g
The percentage of water absorbed by raisins is:
D.
The percentage of water absorbed by raisins is calculated by using the formula
where, W2 is the weight of wet resin and W1 is the weight of dry resin.
Name the life process of an organism that helps in the growth of its population
Reproduction is the life process which helps in the growth of the population.
During the course of an experiment, 'to determine the percentage of water absorbed by raisins', raisins are weighed
every half an hour.
every hour.
once - only after completing the experiment.
two times - before soaking and after soaking for three hours
C.
once - only after completing the experiment.
Name one gustatory receptor and one olfactory receptor present in human beings.
One gustatory receptor: Tongue
One olfactory receptor: Nose
Name the hormones secreted by the following endocrine glands and specify one function of each :
(a) Thyroid
(b) Pituitary
(c) Pancreas
Following are the hormones secreted by the given endocrine glands:
(a) The thyroid gland secretes thyroxine hormones. The thyroid hormones are responsible for regulating many of our body function, such as our breathing, heart rate, temperature, etc.
(b) Pituitary gland secretes growth hormone. It regulates growth and development of the body.
(c) Pancreas secretes insulin. It regulates blood sugar level in body.
Mention any two components of blood
Components of blood:
Blood consists of blood cells and a fluid medium called plasma in which the cells (R.B.C, W.B.C and platelets) are suspended.
Trace the movement of oxygenated blood in the body.
The deoxygenated blood comes to the heart through veins. It is oxygenated in the lungs and comes back to the heart. From heart oxygenated blood is distributed to all parts of the body.
Mechanism of blood moment:
The oxygenated blood leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. This blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. Left The ventricle pumps oxygenated blood to different parts of the body.
Write the function of valves present in between atria and ventricles.
The valves in the heart are to prevent the backflow of blood when the atria or ventricles contract.
Define excretion.
The biological process involved in the removal of the excess of water, salts and toxic wastes (like urea and uric acid) from the body is called excretion.
Name the basic filtration unit present in the kidney.
The nephron is the filtration units present in the kidney
List the steps of preparation of temporary mount of a leaf peel to observe stomata.
The following are the steps of preparation of temporary amount of a leaf peel to observe stomata.
(i) Remove a healthy leaf from the potted plant.
(ii) Remove a part of the peel from the lower surface of the leaf by folding the leaf over and gently pulling the peel apart using forceps.
(iii) Put a few drops of safranin stain in a watch glass.
(iv) After 2-3 minutes take out the peel and place it on a clean glass slide.
(v) Put a drop of glycerin over the peel and place a clean coverslip gently over it.
(vi) Remove the excess stain and glycerin with the help of blotting paper.
(vii) Observe the slide under the low-power and high-power magnifications of the compound microscope.
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