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1.c. Gives safety against dental carries.

2.b. Ptyalin

3.b. Sublingual gland

4.d. All of the above

5.c. Hydrochloric acid

During summer season, we lose a good amount of water through perspiration to keep our body temperature normal. While in winter, there is no perspiration. That is why, in summer season we drink a lot of water and pass urine fewer times

Monozygotic twins:

1. Two children developing from only one zygote are called monozygotic twins.

2. Monozygotic twins develop from same oocyte. 

3. Gender of both the twins is same.

4. The monozygotic twins are genetically exactly alike.

Dizygotic twins:

1. Two children developing from two different zygotes are called dizygotic twins. 

2. Dizygotic twins develop from two different oocytes. 

3. Gender of both the twins can be same or can be different. 

4. The dizygotic twins are genetically not exactly alike.

In the single circulation the deoxygenated blood from the whole body of the animal spammed into the heart. From the heart it goes to the gills and the oxygenated blood is pumped back into the body. This kind of circulation takes place in fishes. Whereas in double circulation the deoxygenated blood is collected from the body, goes to the lungs for the process of oxygenation and then this oxygenated blood comes back to the heart. The heart pumps back this oxygenated blood into the body tissues. In this type of circulation, as the blood passes through the heart two times, it is known as double circulation. It takes place in birds & mammals like human beings.

Digestive juice contains different enzymes. Enzymes act as catalysts and bring about the chemical reactions at faster pace. The digestive juices of stomach make pH of digestive tract acidic while that of intestinal juice make it alkaline.

1. The gametes that take part in the sexual reproduction should be haploid.

2. Otherwise the chromosome number will not be maintained at constancy. E.g. Parents have 2n = 46 chromosomes in their cells.

3. If meiosis does not take place in them, the gametes formed will also contain 46 chromosomes.

4. The resultant offspring will have 46 + 46 = 92 chromosomes.

5. Such skewed number will produce large scale abnormalities.

6. But due to meiosis, the gametes formed are haploid and thus the chromosome number is maintained constant for every species. Gametes are haploid cells, this is the most important fact.

The valves present between the auricles and ventricles and between the ventricles and pulmonary artery and aorta prevent backflow of blood. Bicuspid or mitral valve is present in between left auricle and left ventricle. Tricuspid valve is present in between right auricle and right ventricle. Semilunar valves are present in between right ventricles & left ventricle and pulmonary artery & aorta respectively.

(a) The raw materials for photosynthesis are carbon dioxide and water. The green plants take carbon dioxide from air for photosynthesis. The carbon dioxide gas enters the leaves of the plants through the stomata present on their surface. The water required by the plants for photosynthesis is absorbed by the roots of the plants from the soil through the process of osmosis. The water absorbed by the roots is transported upwards through the xylem vessels to the leaves where it reaches the photosynthetic cells and utilized in photosynthesis. 

(b) The conditions for photosynthesis are sunlight, chlorophyll, carbon dioxide and water. 

(c) Factors affecting the rate of photosynthesis are 

(i) Light 

(ii) Carbon dioxide 

(iii) Water 

(iv) Temperature 

(v) Mineral elements.

All the cells in multicellular organisms may not be in direct contact with the surrounding environment. Thus, simple diffusion will not meet the O₂ requirements of all the cells.

This plant will not remain healthy for a long time because :

(i) It will not get oxygen for respiration.

(ii) It will not get carbon dioxide for photosynthesis.

(iii) Upward movement of water and minerals would be hampered due to lack of transpiration.

(a) This plant will not remain healthy for long because vaseline coating closes the stomatal pores on the leaves due to which 

(i) plant will not get oxygen for respiration 

(ii) plant will not get carbon dioxide for photosynthesis, and 

(iii) plant will not get water (and minerals) due to stoppage of transpiration. 

(b) (i) Decreases in morning but increases in the afternoon 

(ii) Decreases. 

(iii) Decreases.

(a) No, this plant will not remain healthy for long. The plant will begin to die because 

(i) Gaseous exchange will not take place. 

(ii) No absorption of CO₂, hence no photosynthesis. 

(iii) Transpiration will not occur; hence no transportation of water.

(b)

Air is present in between the particles of the soil. The roots take the oxygen by the process of diffusion. Oxygen first diffuses into the root hairs and reaches all other cells of the root for respiration. CO₂ produced in the cells moves out through the root hairs by the process of diffusion. For respiration, in older roots, where root hair is not present, the exchange of gases takes place through lenticels (tiny openings in the protective layer) by the process of diffusion.

Capillaries.

If humans also had gills then the deep sea divers could remain under sea water even without carrying oxygen cylinders for breathing as they would be able to extract the dissolved oxygen from water for breathing purpose just like a fish does.

Plants do not move. In a large plant body there are many dead cells like sclerenchyma as a result it requires less energy as compared to animals.

Capillaries are smallest vessels which have one cell thick wall. The exchange of material between the blood and the surroundings take place through capillaries.

Starch breaks down in the mouth, salivary glands present in the mouth secrete saliva. Saliva contains an enzyme called salivary amylase that breaks down starch to give sugar (maltose).

The process of photosynthesis involves a few events that may not occur immediately after one another. There might be a time lag between them. 

•The chlorophyll present in chloroplasts absorbs energy from sunlight. 

•This light energy is then converted into chemical energy which is used for making food. 

•The water molecules split to give hydrogen and oxygen. 

•Finally, CO₂ absorbed is reduced to form glucose (carbohydrate).

Because plant bodies have a large proportion of dead cells.

(a) Lymphatic system: A system of tiny tubes called lymph vessels (lymphatics) and lymph nodes (lymph glands) in the human body which transports the liquid called lymph from the body tissues to the blood circulatory system is called lymphatic system. Functions of lymphatic system: 

(i) It takes part in the nutritive process of the body. 

(ii) It protects the body by killing the germs drained out of the body tissues with the help of lymphocytes contained in the lymph nodes, by making antibodies. 

(iii) It helps in removing the waste products like fragments of dead cells etc. 

(b) Blood pressure: The pressure at which the blood is pumped around the body by the heart is called blood pressure. The two factors which expresses the blood pressure a person are systolic pressure and diastolic pressure. 

(c) Urea is the main nitrogenous waste in human blood. It is removed from the body in the  form of urine through the kidneys.

Lymph is a colorless liquid which is released out of the tissues. It is so because lymph contains only WBCs and not RBCs. Since the WBCs are colorless, lymph is also colorless. It has the same mineral composition as that of the plasma.

The following events occur during photosynthesis:

1. Absorption of light energy by chlorophyll.

2. Conversion of light energy to chemical energy and splitting of water molecule into hydrogen and oxygen.

3. Reduction of carbon dioxide to carbohydrates.

Because they do not maintain their own body temperature, therefore they do not require separation of oxygenated and deoxygenated blood. 

Animals and Fungi.

Functions :

(i) Carry digested fat/absorption of fat.

(ii) Drains excess fluid from extracellular space back into the blood.

Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood.

Lymph is colourless and contains less protein than plasma.

Lymph a colourless fluid containing white blood cells.

Thick walls of arteries help them to resist the pressure of flow of blood in them. Arteries are elastic so as to produce enough pressure to push the blood and help it flow.

Main function of valve is to prevent backflow of blood. Since the blood pressure in veins is very low they have valves that prevent back flow of blood.

Veins have thin walls because veins collect the blood from different organs and bring it back to the heart. The blood is no longer under pressure and blood flows only in one direction.

A. Renal artery – It supplies oxygenated blood from the heart to the kidney. 

B. Renal vein – It carries deoxygenated blood from the kidney back to the heart. 

C. Ureters – Paired tubes connecting kidneys to the urinary bladder. They transport urine from the kidneys to the bladder.

Different respiratory adaptations of human beings are as follows: 

• The respiratory surface, which helps in exchange of gases must be very thin for easy and fast exchange of gases. 

• The respiratory surface must be richly supplied with blood vessels for exchange of gases. 

• The thin and delicate respiratory structures must be well protected under layers of tissues so as to protect them from the external environment.

(i) Trypsin + Proteins→ Amino acids

(ii) Amylase + Carbohydrates→ Simple Sugars

(iii) Lipase + Fats→ Fatty acids +Glycerol.

Following are the two proteases in pancreatic juice: 

•Trypsin: It helps in the digestion of proteins. 

•Chymotrypsin: It helps in the breakdown of proteins into smaller molecules.

Pancreatic juice contains digestive enzymes ? Pancreatic Amylase, trypsin and lipase. 

Functions:

(a) Pancreatic amylase: The enzyme amylase breaks down the starch.

(b) Trypsin: trypsin digests the proteins.

(c) Lipase: Lipase breaks down the emulsified fats.

Chemical digestion takes place in small intestine. It secretes chemicals which break down the food and take away nutrients to blood stream. The maximum absorption of digested food occurs in the small intestine part of the alimentary canal. It begins from the pyloric part of stomach and ends up into large intestine. Small intestine has 3 partsduodenum, jejunum and ileum. The undigested food is passed to the large intestine where maximum water is reclaimed before egestion of solid faeces.

The answer is  (b)small intestine.

• The small intestine is made up of duodenum, jejunum, and ileum. 
• It receives the bile from the liver which helps in the breakdown of fats. 
• Bile juice is produced in the liver and stored in gall bladder.

Bile is secreted by the liver, stored in gall bladder and released into the small intestine where it breaks down lipids into fatty acids, helps in absorption of fat soluble vitamins and neutralization of gastric acid.

Bile salts are a component of bile, a fluid secreted from the gallbladder during the digestion of lipids. The presence of bile salts gives bile the ability to emulsify, or mix, lipid in the aqueous environment of the intestine.

Platelets help in clotting of blood in the event of a cut.

The walls of the arteries are found to be thicker than that of a Vein because the blood that is carried from the heart to the capillaries has more high pressure. As tire blood flowing through the veins does not have much pressure as in that of the arteries their walls are thinner as compared to artery walls.

Three types of blood vessels in human circulatory system are: Arteries, Veins and Capillaries. Their functions are tabulated below:

The four chambers of heart are Right atrium, Left atrium, Right Ventricle and Left ventricle.