Solved Exercise, Bio-11, Ch-12


(i) Plants absorb minerals in their ________ form, as found in the soil. (ionic)

(ii) In plants the most common nutrient deficiencies are of _______, ______ and _______. (nitrogen, phosphorus & potassium)

(iii) A plant requires ________ for holding its cell together. (cellulose)

(iv) Most of the organic material in a plant is ________. (carbohydrate)

(v) Chlorosis is usually caused by insufficient ________. (nitrogen)

(vi) In _________, the trapped insects are decomposed by bacteria. (pitcher plant)

(vii) The structure in the mouth that prevents food from entering the nasal cavities is the ________. (soft palate)

(viii) The stomach functions to _______ and _______ food and its ________. (store & digest, components)

(ix) ________ is the common example of detritivore. (earthworm)

(x) Pancreas produces ________ which stimulates the conversion of glycogen to ________. (amylase, maltose)

(xi) Vomiting occurs due to ________ movements. (antiperistalsis)


(i) A plant requires nitrogen and sulphur for its:

(a)   Cell wall

(b)   Enzymes

(c)   Starch deposits

(d)   DNA replications

EXPLANATION: Enzymes are made up of proteins which contain nitrogen in amino group of amino acids, and sulphur in sulphide bridges.

(iii) A plant requires potassium for its: 

(a)   Synthesizing protein

(b)   Synthesizing chlorophyll

(c)   Opening and closing of stomata

EXPLANATION: Stomata open due to active transport of potassium ions (K+) into the guard cells from the surrounding epidermis. The accumulation of K+ decreases the osmotic potential of guard cells. Water enters the guard cells by osmosis, which become more turgid and stretched and stomata are opened. The stoma closes by reverse process; involving passive diffusion of K+ from guard cells followed by water moving out by osmosis.

(iii) Carnivorous plants live in soils that are deficient in:

(a)   Water                                             

(b)   Oxygen

(c)   Nitrogen

(d)   Iron

EXPLANATION: Carnivorous plants live in soils that are deficient in nitrogen. That’s why these plants make up their nitrogen deficiency by eating insects and other small animals.

(iv) Most vitamins function as: 

(a)   Catalyst

(b)   High energy compound

(c)   Gastro vascular cavity

(d)   Mouth

EXPLANATION: Vitamins are involved in the formation of co-enzymes which are required for proper functioning of enzymes, the biocatalysts. 

(v) Digestion in hydra and planaria takes place within its: 

(a)   Coelom

(b)   Alimentary canal

(c)   Gastrovascular cavity

(d)   Transport molecules

EXPLANATION: Hydra and Planaria have sac-type digestive system which have only one opening called mouth. They have a single cavity which is called gastrovascular cavity because it is used for both digestion and transportation.

(vi) Mucus in saliva is made of: 

(a)   Glycolipids

(b)   Glycoproteins

(c)   Phospholipids

(d)   Saturated fatty acids

EXPLANATION: Mucus in saliva, as found in humans, is primarily composed of water, electrolytes, glycoproteins (notably mucins), enzymes, and antimicrobial agents.  

(vii) The structure in the mouth that prevents food from entering the nasal cavities is the:

(a)   Epiglottis

(b)   Soft palate

(c)   Tongue

(d)   Pharynx

EXPLANATION: The soft palate functions to close off the nasal passages during the act of swallowing, preventing food and liquid from entering the nasal cavities. It also plays a role in speech, helping to produce certain sounds.

(viii) A mammalian herbivore has: 

(a)   Fewer teeth than a carnivore

(b)   Flatter teeth than a carnivore

(c)   More teeth than a carnivore

(d)   More pointed teeth than a carnivore

EXPLANATION: Herbivores have flatter teeth to grind plant material, while carnivores have sharper teeth for cutting meat.

(ix) Many humans become ill from consuming milk and milk products because they lack: 

(a)   Bacteria in their intestines

(b)   Renin

(c)   Lactase

(d)   Hydrochloric acid

EXPLANATION: Many humans become ill from consuming milk and milk products because they lack lactase, the enzyme needed to digest lactose, the sugar in milk.

(x) Which of the following animals has no need for a gall bladder?  

(a)   Cat

(b)   Man

(c)   Lion

(d)   Goat

EXPLANATION: Goats have a continuous bile secretion into the digestive tract, eliminating the need for a gall bladder, as their diet is low in fat.


Tube-like or tubular digestive system as in cockroach is more efficient than sac-like digestive system as in hydra because it has specialized organs or partitions for efficient digestion and absorption of food.

Functions of Human Liver: Two amin functions of human liver are:

(1) Liver produces bile which may be temporarily stored in gall bladder to be released later into duodenum. Bile contains bile salts which emulsify fats so that lipase may digest them easily.

(2) Liver makes cholesterol and release it in blood stream so that they may be used for the formation of membranes, hormones and vitamin D.

Preventions from Food Poisoning: Food poisoning can be prevented:

(1) If we avoid unpasteurized milk and use only pasteurized milk.

(2) If we cook meat properly before eating.

(3) If we prevent our food and cooking utensils from coming in contact with the liquid escaping from defrosting meat because it contains the bacterium ‘Salmonella’.

We cannot get along without large intestine because in large intestine most of the water and salts are absorbed into blood. If it does not occur, the result will be diarrhoea and dehydration that may prove fatal. Also, the large intestine harbours useful bacteria that synthesize vitamins, especially vitamin K, which are very useful for man.


Consult textbook at page 234 — 235.


Saprophytic Nutrition:

Feeding on dead and decaying matter such as dead leaves in the soil or rotting tree trunks is called saprophytic nutrition and derives its nutrients from host plants. They produce extracellular enzymes, which digest the decaying matter and then absorb the soluble products back into their cells. Some bacteria break down the proteins of dead plants and animals and release nitrates which are taken up by the plant roots and then built into new amino acids and proteins, thus helping in nitrogen cycle.

Parasitic Nutrition:

Feeding by living in or on other organism (host) belonging to different species is called parasitic nutrition. Parasites attach themselves to living things or their host, for nourishment. For obtaining nourishment from higher plant the parasite penetrates its suckers in the conducting tissue of the host. Puccinia is a parasitic fungus that destroys the wheat plant. Dodder (Cuscuta)is a leafless plant that lives as a twining parasite.


i) Dodder (Cuscuta) is a leafless plant that lives as a twining parasite.

ii) Cuscuta, commonly known as Dodder, is a parasitic plant that lacks chlorophyll, preventing it from photosynthesis and normal nutrition. Instead, it relies on a specialized method of nutrition called parasitism. Dodder attaches itself to a host plant and forms haustoria, structures that penetrate the host’s vascular system. Through these haustoria, Dodder extracts water, nutrients, and carbohydrates directly from the host plant, bypassing the need for traditional methods of obtaining nutrients from soil and sunlight.

Heterotrophs are the organisms which cannot manufacture their organic compounds from simple inorganic nutrients. So, they obtain these organic molecules from their environment in the form of food.

Examples: Animals, fungi etc.

For different methods of nutrition in heterotrophs consult textbook at pages 235 — 236.


(1) Guaranteed Food Source: Parasites have direct access to a readily available food source in their host, eliminating the need for foraging or hunting.

(2) Protection: Some parasites may benefit from the host’s immune system or physical barriers, gaining protection from predators and harsh environments.

(3) Reproduction: Some parasites have complex life cycles that rely on specific hosts for reproduction, ensuring their offspring have a higher chance of survival.

(4) Reduced Energy Expenditure: By relying on the host for resources, some parasites minimize their own energy expenditure, allowing them to allocate more resources to reproduction.


(1) Dependence on Host: Parasites are entirely dependent on their host for survival, making them vulnerable to host death, immune response, or changes in the host’s environment.

(2) Competition: Many parasites share the same host, leading to intense competition for resources and potentially harming the host, which could endanger the parasite as well.

(3) Limited Niche: Parasites are restricted to specific hosts or environments, limiting their adaptability and evolutionary potential.

(4) Negative Effects on Host: Many parasites weaken or harm their hosts, reducing their lifespan and potentially attracting predators or further diseases. This can ultimately harm the parasite population as well.


(1) Independence: Free-living organisms are not reliant on another organism for survival, giving them more control over their environment and resources.

(2) Greater Flexibility: They can adapt to changing environments and move freely, potentially accessing a wider range of resources and mates.

(3) Reduced Risk of Immune Response: They don’t face the constant threat of rejection or attack from a host’s immune system.

(4) Less Negative Impact: They generally have less impact on the health and survival of other organisms in the ecosystem.


Parasitism offers a guaranteed food source and protection, but at the cost of dependence, competition, and limited evolutionary potential. Free-living organisms have greater independence and flexibility, but need to find their own resources and face environmental challenges. Both strategies have their own advantages and disadvantages, and the “better” option depends on the specific organism and its environment.


All animals have almost similar requirements. They must have the supply of water, oxygen, simple sugars, amino acids, fatty acids, vitamins and many other inorganic and organic substances. These substances, except oxygen and water, are rare in the natural environment and are not directly available to the organisms. In nature, these substances are available in the form of proteins, starches, fats, vitamins and minerals. As such, these molecules except vitamins and minerals are of no use unless they are broken down or digested into simple molecules such as amino acids, sugars and fatty acids so that they many pass through the cell membrane and be used by the body. Digestion is the breakdown of complex organic compounds of food into simpler diffusible molecules by the action of enzymes e.g. proteins (meat, fish, eggs etc.) into amino acids. That’s why digestion is necessary.


For detail consult the textbook at page 247 — 249.


“Holozoic nutrition is a type of nutrition in which an organism ingests and digests solid or liquid organic matter to obtain energy and nutrients for its survival.” This type of nutrition is observed in most animals, including humans. Holozoic nutrition involves following stages or processes:

(1) Ingestion_ The taking in of complex food.

(2) Digestion_ The breakdown of complex organic compounds of food into simpler diffusible molecules by the action of enzymes.

(3) Absorption_ The uptake of the diffusible food molecules from the digestive region across the membrane in to the cell or into the blood stream.

(4) Assimilation_ The utilization of the products of digestion for production of energy or synthesis of cellular material.

(5) Egestion_ The elimination of undigested matter from the body.


For detail answer consult textbook at page 246, 249, 250.

A pair of salivary glands is present in the thorax region of the animal. They secrete saliva, which is poured into the mouth cavity. The digestive enzymes of saliva hydrolyze the starchy matter contained in food.

Short finger like hollow tubes, the hepatic caecae open into the anterior end of the midgut. The enzymatic secretions of hepatic caecae and midgut digest the food completely.

Consult textbook at page 247 —249.

The digestive tract of herbivores is adapted for processing plant material, featuring longer digestive tracts, specialized teeth for grinding, and complex stomachs for cellulose digestion. Carnivores have shorter digestive tracts, sharper teeth for tearing meat, and simpler stomachs for efficient protein and fat digestion.

Mucus (glycoprotein) is a thick secretion that covers the inside of the stomach. It prevents the underlying walls from being digested by the gastric juice.

Consult textbook at page 250 —251.


Liver secretes bile, which may be temporarily stored in the gall bladder and released into the duodenum through the bile duct. The bile is green, watery fluid. It contains no enzymes, but its green colour is due to the bile pigments, which are formed from the breakdown of hemoglobin in the liver. The bile also contains bile salts, which act on fats, and emulsifies them. It means that they break them up into small globules, which are then easily digested by water-soluble lipase.


Pancreas is a large gland whose exocrine tissue secretes a juice that lows through pancreatic duct into the duodenum. Included in this juice are enzymes that digest all principal components of food i.e. carbohydrates, fats and proteins. Carbohydrate- digesting enzyme is pancreatic amylase also called amylopsin, which digests starch into maltose. Fat digesting enzyme is lipase, that hydrolyzes a small percentage of fats into fatty acids and glycerol. Like pepsin, trypsin is also secreted as inactive trypsinogen, which is activated by enterokinase, an enzyme secreted by the lining of the duodenum.

We can control obesity if we stop eating surplus food that may be stored as adipose tissue to make us obese. If we eat according to our body needs and take regular exercise and walk, we can avoid obesity.

Normally, the secretion of the gastric juice is regulated by smell, sight and quality of food. If more protein is present in the food reaching the stomach, it stimulates the production of gastrin hormone from the gastric endocrine lining, which is carried by blood to the gastric glands and stimulates them to produce more gastric juice. Thus, more proteins more gastrin and more gastric juice for digestion.

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