Science [3 Mark Questions]

For nervous and hormonal systems to control and coordinate in human beings, hypothalamus plays an important role in receiving the neural/ nerve signals from brain and release hormones.
Example - In situation of iodine deficiency, hypothalamus releases hormones to stimulate pituitary gland, it further sends stimulating hormone to thyroid gland to secrete thyroxine that regulates carbohydrate metabolism.

Loss of water vapour through the stomatal openings of the leaves of a plant is termed as transpiration.

1. Following experiment can be performed to demonstrate transpiration in a plant:
2. Place a healthy growing plant on a horizontal and plane slab in the sun.
3. Place a glass bell jar over the potted plant and seal its end to the slab by applying vaseline at its edges.
4. Allow the set-up to remain in the sun for some time.
5. Observe the presence of water droplets on the inner surface of the glass bell jar.
6. This collection of water droplets is indicative of transpiration.

Three main types of blood vessels that are found in the human body are arteries, veins, and capillaries.
Arteries carry blood from the heart to different body parts. Veins bring blood from different body parts to the heart. Valves are present in veins to prevent backward flow of blood. Both arteries and veins divide in the organs to form arterioles and venules respectively. The arterioles sub-divide to form thin-walled capillaries which join to form venules. Venules join to form veins. The nutrients, hormones, gases can diffuse into the tissue cells through the walls of the capillaries and vice versa. Thus, arteries, arterioles, veins, venules, and capillaries are blood vessels.

The villi has a finger like structure and the microvilli acts as a hairlike on those fingers. Both of them expand to increase the surface area so more nutrients can be absorbed. They both are made up of a single layer of cells. the villi and the microvilli increase intestinal absorptive surface area approximately 30-fold and 600-fold, respectively, providing exceptionally efficient absorption of nutrients in the lumen. There are also enzymes (enterocyte digestive enzyme) on the surface for digestion.

He process by which oxygen rich air is taken up through the nostril into the body is known as inhalation. During inhalation, the chest cavity increases in size due to the downward movement of the diaphragm (dome shaped muscular sheet that separates chest from abdomen). As a result air from outside rushes into the lungs to fill the extra space.
Explanation: is the process by which carbon dioxide rich air comes out of the body. It occurs when the diaphragm moves up and the chest cavity becomes narrower. This creates a pressure on the air inside the lungs. As a result the air comes out of the lungs to the atmosphere due to lack of space inside. Both the process of inhalation and exhalation is commonly known as breathing.

Apart from water, plants excrete out a number of liquid waste products into the soil around them. It includes essential oils, organic acids, aromatic oils, tannins, resins, latex and sap.
They are stored in leaves dead cells and the leaves fall off. Some other waste products are stored as resins and gums in old xylem of the plant and other wastes Most of these wastes are useful to humans.

1. Herbivores: Those animals which eat only plants are called herbivores.

Example: Goat and cow.

2. Carnivores: Those animals which eat only other animals as food are called carnivores.

Example: Tiger and Lion.

3. Omnivores: Those animals which eat both plants and animals are called omnivores.

Example: Human Being and dog.

The mechanism by which an organism obtains oxygen from the air and releases carbon-dioxide is called breathing.Difference between breathing and respiration:Breathing:

1. Breathing is a simple process.
2. Breathing involves taking in oxygen from the air and releasing carbon dioxide into the air.
3. Breathing is a physical process.

Respiration:

1. Respiration is a complex process.
2. Respiration includes breathing as well as the oxidation of food in the cells of the organism to release energy.
3. Respiration is a bio-chemical process.

Xylem	Phloem
Xylem tissue helps in the transport of water and minerals.	Phloem tissue helps in the transport of food.
Water is transported upwards from roots to all other plant parts.	Food is transported in both upward and downward directions.
Transport in xylem occurs with the help of simple physical forces such as transpiration pull.	Transport of food in phloem requires energy in the form of ATP.

This diffusion pressure plays a major role in exchange of gases in plants and in smaller animals but fails in bigger animals. Multicellular organisms such as humans possess complex body designs. They have specialised cells and tissues for performing various necessary functions of the body such as intake of food and oxygen. Unlike unicellular organisms, multicellular cells are not in direct contact with the outside environment. Therefore, diffusion cannot meet their oxygen requirements.

Lymph is a light yellow liquid. It is a medium of circulation in human body which flows only in one direction – from body tissues to the heart. The functions of lymph are:

1. It takes part in the nutritive process of the body.
2. 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.
3. It helps in removing the waste products like fragments of dead cells etc.

The maximum pressure at which the blood leaves the heart through the main artery (Aorta) during contraction phase is called systolic pressure. The minimum pressure in the arteries during relaxation phase of the heart is called the diastolic pressure.
The normal blood pressure values are: Systolic pressure: 120mm Hg. Diastolic pressure: 80mm Hg.

The breathing rate of aquatic animals is faster than that of terrestrial animals because the amount of dissolved oxygen in the water in much less than the amount on land. Therefore, rate of breathing in aquatic organisms is much faster than in terrestrial organisms.

To get rid of excretory products, plants use the following ways:

1. Many waste products are stored in vacuoles of the cells. Plant cells have comparatively large vacuoles.
2. Some waste products are stored in the leaves. They are removes as the leaves fall off.
3. Some waste products such as resins and gums are stored, especially in non-functional old xylem.
4. Some waste products such as tannins, resins, gums are stored in bark, thereby removed as peeled off.
5. Plants excrete some waste products through roots into the soil around them.
6. Plants also get rid of excess water through transpiration.

The fish has a two chambered heart. Oxygenation of the blood takes place in the gills. The oxygenated blood from the gills is supplied to the body parts of the fish where oxygen is utilized and carbon-dioxide enters into it making it deoxygenated. The deoxygenated blood returns to the heart to be pumped into gills again.

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

1. Plant will not get oxygen for respiration.
2. Plant will not get carbon dioxide for photosynthesis, and.
3. Plant will not get water (and minerals) due to stoppage of transpiration.

Different respiratory adaptations of human beings are as follows:

1. All the respiratory organs have a large surface area to get enough oxygen.
2. All the respiratory organs have thin walls for easy diffusion and exchange of respiratory gases.
3. All the respiratory organs like skin gills, and lungs have a rich blood supply for transporting respiratory gases.

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

The circulatory system also serves to remove waste products from the body. Certain wastes such as water, urea, uric acid and carbon dioxide are transported from the liver to the kidneys, where the blood is filtered. The urea is produced in liver and released into the bloodstream. Blood flows round the body; it passes through the heart to replenish its oxygen content. Veins are the blood vessels that take oxygen depleted blood from the body to the heart while arteries take oxygen rich blood away from the heart to the body. Blood transports nutrients from the digestive system or storage sites to tissues that require them, and waste products from the tissues to the liver and then to the kidneys for disposal.

Mechanics of Breathing. The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside. This action is also known as external respiration. When we inhale the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity.

1. Decreases in morning but increases in the afternoon.
2. Decreases.
3. Decreases.

	Aerobic Respiration	Anaerobic Respiration
1.	Method: It is the common method of respiration.	It occurs permanetly only in a few organisms. In other it may occur as a temporary measure to overcome shortage of oxygen.
2.	Steps: It is completed in 3 steps- glycolysis, krebs cycle and terminal oxidation.	There are two steps- glycolysis and anaerobic breakdown of pyruvic acid.
3.	Oxygen: It requires oxygen.	Oxygen is not required.

The photosynthesis takes place in the following three steps:

1. Absorption of sunlight energy by chlorophy ll.
2. Conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen by light energy.
3. Reduction of carbon dioxide by hydrogen to form carbohydrates like glucose by utilising the chemical energy.

Functions of blood:

1. It carries oxygen from the lungs to different parts of the body.
2. It carries carbon-dioxide from the body cells to the lungs for breathing out.
3. It carries digested food from the small intestine to all the parts of the body.
4. It carries waste product called urea from the liver to the kidneys for excretion in the form of urine.
5. It protects the body from diseases.

The various types of Heterotrophic nutrition are:

1. Saprotrophic nutrition.
2. Parasitic nutrition.
3. Holozoic nutrition.

Respiration and fish: The fish has special organ of breathing called gills on both the sides of its head. The gills are covered by gill covers. The fish lives in water which contains dissolved oxygen. The fish breathes by taking in water through its mouth and sending it over the gills. When water passes over the gills, the gills extract dissolved oxygen from the water. The extracted oxygen is absorbed by the blood and carried to all the parts of the fish. The carbon-dioxide produced by respiration is brought back by the blood into the gills for expelling into the surrounding water.

The common features of all respiratory organs? skin, gills and lungs are:

1. All the respiratory organs have a large surface area to get enough oxygen.
2. All the respiratory organs have thin walls for easy diffusion and exchange of respiratory gases.
3. All the respiratory organs like skin, gills and lungs have a rich blood supply for transporting respiratory gases.

Non flowering plants includes ferns, mosses and gymnosperms (exception: they produce seeds from cones). Tracheids are the conducting elements in gymnosperms and pteridophyte. In bryophytes like mosses water and mineral conduction takes place by hydroid tissue and sugar conducting tissue is leptoid​.

The urine is stored in urinary bladder, which is a muscular sac composed of smooth muscles that are able to relax and contract. The pressure built inside the expanded bladder due to storage of urine leads to the urge to urinate. The urinary bladder is muscular, so it is under nervous control. As a result, we can usually control the urge to urinate.

There are various features among terrestrial organisms that aid in respiration. Some animals exchange gases through their moist skin surface, insects have tracheal systems for exchange of gases and higher animals have lungs. Common features of all these respiratory organs are as follows:

1. All the respiratory organs have a large surface area to transport/exchange enough oxygen.
2. All the respiratory organs have thin walls for easy diffusion and exchange of respiratory gases.
3. All the respiratory organs such as skin, gills and lungs, have a rich blood supply for transporting respiratory gases.

The de-oxygenated blood received into the right atrium is then made to go into the right ventricle after the heart's contraction and then that blood goes into the pulmonary artery from the ventricle and goes to the lungs where the carbon-dioxide is then diffused into the alveoli and then the oxygen recieved in the lungs again gets diffused in the blood and then again goes to the heart from the pulmonary vein.

Almost all the organisms the breathing surface is very fine and delicate for easy and fast exchange of gases. Since they are very delicate they must be protected from external environmental conditions. So for protection these structures are covered well in a layer of tissues. Like in human beings the exchange of gases take place through alveoli which are present in the lungs which are further protected from environment by ribs and diaphragm.

There are two ways in which glucose is oxidized to provide energy in various organisms:

1. Anaerobic respiration? The respiration which takes place without oxygen is called anaerobic respiration.

Example: Yeast and some bacteria break down glucose into ethanol and carbon-dioxide.

2. Aerobic respiration? The respiration which uses oxygen is called aerobic respiration.

Example: Plants and animals break down glucose completely into carbon-dioxide and water to release energy.

The components of xylem tissue (tracheids and vessels) of roots, stems, and leaves are interconnected to form a continuous system of water-conducting channels that reaches all parts of the plant. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the plant parts through the interconnected water conducting channels.

Conditions necessary for autotrophic nutrition are:

1. Light.
2. Chlorophyll.
3. Water and,
4. Carbon dioxide.

By-products are:

1. Oxygen and,
2. Water.

Transpiration is the loss of water from a plant in the form of water vapor. Water is absorbed by roots from the soil and transported as a liquid to the leaves via xylem. In the leaves, small pores allow water to escape as a vapor. Of all the water absorbed by plants, less than 5% remains in the plant for growth.

Respiration on the basis of presence or absence of oxygen can be of two type. aerobic respiration and anaerobic respiration. Aerobic respiration occurs in the presence of oxygen while anaerobic occurs in the absence of oxygen.
Site of aerobic respiration is mitochondria.
During aerobic respiration 38 ATPs get released in complete oxidation of one glucose molecule.

Various outside raw materials used by an organism are as follows:

1. Food as source of supplying energy and materials.
2. Oxygen for breakdown of food to obtain energy.
3. Water for proper digestion of food and other functions inside the body.

The raw materials required by an organism will vary depending on the complexity of the organism and its environment.

	Artery	Vein	Capillary
i.	It is a thick walled blood vessel.	It is a thin walled blood vessel.	It is an extremely narrow blood vessel having very thin walls.
ii.	It carries blood from the heart to different parts of the body.	It brings blood from the different parts of the body to the heart.	They form an extensive network throughout all living cells in the body and connect arteries and veins.
iii.	It can dilate or constrict depending on the regulatory requirement of the body.	It cannot dilate or constrict.	It can dilate or constrict according to the requirement of the tissue.
iv.	It does not contsin any valve.	It contains simple valves which permit blood flow only towards the heart.	It does not contain any valves.

The formation of small cavities (or holes) in the teeth due to the action of acid forming bacteria and improper dental care is called dental caries. This happens as follows:
When we eat sugary food, the bacteria in our mouth act on sugar to produce acids. These acids dissolve the calcium salts from the tooth enamel and then from dentine forming small cavities in the tooth over a period of time in our mouth act on sugar to produce acids. These acids dissolve the calcium salts from the tooth enamel and then from dentine forming small cavities in the tooth over a period of time.

Yes, of course.
We have an equilibrium between gases dissolved in our blood and gases in our alveolae. The law is Henry’s law. The amount of dissolved gases in a fluid is directly proportional to the partial pressure of gases above the fluid. When you breathe in, partial pressure of oxygen is 1/5 of an atmosphere and nitrogen is 4/5 of an atmosphere. Our bodies use oxygen so it goes out of blood, hence out of alveolae. Carbon dioxide our bodies produce hence its concentration goes up in the blood and subsequently in alveolae. Nitrogen is neither consumed not produced so it stays approximately the same. After expiration you have in your lungs only residual volumen and oxygen continues to go down and carbon dioxide goes up. Now, after several seconds, maybe even a minute, you will feel a strong urge to breathe in. That’s because the level of carbon dioxide becomes very high in your blood and in your alveolae. It stimulates the centres in your medulla oblongata and you will have that urge to breathe in. It’s possible to overcome that urge. That’s what all breath-hold divers do. However, oxygen continues to go down. When it reaches very low levels you simply fall unconscious. That’s obviously not a desired outcome and, if underwater, you drown and die.

Phloem fibres are the dead element of phloem.

High blood pressure is called hypertension. It is caused by the constriction of very small arteries which results in increased resistance to blood flow. Very high blood pressure can lead to rupture of artery and internal bleeding.

Autotrophic Nutrition: It is that mode of nutrition in which an organism makes its own food from the simple inorganic materials like carbon dioxide and water present in the surroundings (with the help of sunlight energy)Example: Green Plants
Heterotrophic Nutrition: It is that mode of nutrition in which an organism cannot make its own food from simple inorganic materials like carbon dioxide and water, and depends on other organisms for its food.
Example: Animals.

1. Cellulose.
2. Water, glucose, salts in similar concentration to those in normal blood.
3. Urea.