Class 10 Science Chapter 5 MCQ

Heterotrophs are those organisms which cannot make their own food from inorganic substances like CO2 and water as they do not have chlorophyll to trap solar energy, e.g., all animals, most bacteria and fungi. They depend on other organisms for their food. Autotrophs synthesize their own food through photosynthesis by utilising solar energy. e.g., green plants.

It is incorrect as; autotrophs can convert carbon dioxide and water into carbohydrates only in the presence of sunlight. The autotrophs contain the green pigment called chlorophyll which is capable of trapping sun energy. This trapped energy is utilised by them to make food by combining inorganic materials like CO2 and H2O by the process of photosynthesis. The food that is not used immediately, is stored in the form of starch. These autotrophs constitute the first trophic level in food chains.

The blood leaving the tissues becomes richer in Carbon Dioxide. Because tissues receive the oxygenated blood from arteries and used up the oxygen to take energy and release the carbon dioxide.

Here, all the statements are correct. Hence your answer will be option [D].

Fermentation is a form of anaerobic respiration. Pyruvate can be converted into ethanol and CO, in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration. It takes place in cytoplasm. Break down of pyruvate using oxygen, i.e., aerobic respiration takes place in the mitochondria.

The solution turned blue-black in colour just because of starch.

Organisms which can make their own food from carbon dioxide and water are called autotrophs. Carbon dioxide and water are inorganic substance. So, we can say that, those organisms which can make their own food from the inorganic substances present in the environment are called autotrophs. All the green plants are autotrophs.

Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites. Sometimes it is taken up as organic compounds i.e., urea, which have been prepared by bacteria from atmospheric nitrogen.

Large number of tiny pores called stomata are present on the surface of the leaves of plants. The gaseous exchange as well as transpiration takes place through these pores. The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pores to open. Similarly, the pore closes if the guard cells shrink or losses water in them.

Here, all the statements are correct. Hence your answer will be option [D].

Nostrils → pharynx → larynx → trachea → alveoli. The alveoli provide a surface where the exchange of gases can take place.

Alveoli of lungs. The walls of the alveoli contain an extensive network of blood-vessels. When we breathe in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli. The blood brings carbon dioxide from the rest of the body for release into the alveoli, and 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.

A cell is the basic structural and functional unit of a living being. Each cell is made up of molecules. The molecules exhibit movement during cellular reactions that lead to life activities but their movements of molecules do not take place in the cells. The growth of a living organism starts with the division of its cells. All living things have an organised structure, which if breaks down leads to various diseases, disorders and even death. Therefore, the living things have to repair and maintain their structures through various processes. These life processes require energy which is obtained from food.

The blood leaving the tissues becomes richer in CO2. The main artery (aorta) carries oxygenated blood to all the organs of the body from the heart. When the oxygenated blood passes through the capillaries of the body organs/tissues, it gives oxygen to the body cells. At the same time, carbon dioxide produced during respiration enters into blood. Thus, deoxygenated blood (carrying CO2) leaves the tissues and enters the vena cava, from where they are again passed to the lungs for oxygenation.

Here, all the statements are correct. Hence your answer will be option [D].

Pisces have only two chambers to their hearts, and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body. Thus, blood goes only once through the heart in the fish during one cycle of passage through the body.

Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls.

The following events occur in photosynthesis (i) Absorption of light energy by chlorophyll. (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates.

During the photosynthesis, the following steps take place: (i) Absorption of light energy by chlorophyll. (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates.

Non-living things which are not alive cannot move by themselves. For example, a stone is a non-living thing which cannot move by itself from one place to another or show any other type of movement. We will have to move it by applying force from outside.

Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites.

Mitochondria are the sites of aerobic respiration in the cells. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondria.

Aerobic respiration uses oxygen for respiration. It takes place in the mitochondria. After glycolysis, pyruvate (from cytoplasm) enters the mitochondria and is oxidised in a series of reactions, to form considerable amount of energy (ATP), CO2 and H2O.

Carbon dioxide gas turns limewater milky. When air is blown from mouth into test, the lime water turns milky because the air we breathe out has more CO2.

Pancreas secretes pancreatic juice which contain following: Digestive enzymes amylases, lipases, trypsin. Amylase breaks down the starch, trypsin digests the proteins and lipase breaks down the emulsified fats.