Class 9 Biology - MCQ Test (15-02-2017) - Class 9 MCQ

Water Pollution: Detailed Explanation

Water pollution refers to the contamination of water bodies, such as rivers, lakes, oceans, and groundwater, by the addition of undesirable substances. It has several negative impacts on the environment, human health, and aquatic life. The correct option is A, as it includes all the correct statements about water pollution.

Here is a detailed explanation of each option:

A. Addition of undesirable substances into water bodies:

• This refers to the introduction of harmful substances, such as chemicals, heavy metals, pesticides, fertilizers, sewage, and industrial waste, into water bodies.


• These substances can come from various sources, including industrial discharge, agricultural runoff, domestic sewage, and improper waste disposal.


• Water pollution occurs when these substances exceed the natural capacity of the water body to degrade, dilute, or absorb them, leading to adverse effects on the ecosystem and human health.

B. Removal of desirable substances from water:

• This option is incorrect, as water pollution is not about the removal of desirable substances.


• Water pollution focuses on the addition of harmful substances rather than the removal of beneficial ones.

C. Change of temperature:

• This option is incorrect, as water pollution is not specifically related to changes in temperature.


• While temperature changes can affect aquatic ecosystems, it is not the primary focus of water pollution.

D. Addition of desirable substance into water:

• This option is incorrect, as water pollution is concerned with the addition of undesirable substances rather than desirable ones.


• The addition of desirable substances, such as clean water or essential nutrients, would not be considered pollution.

In conclusion, water pollution involves the addition of undesirable substances into water bodies, such as rivers, lakes, and oceans. It is caused by human activities and has detrimental effects on the environment and living organisms. It is crucial to take measures to prevent water pollution and promote the conservation and sustainable use of water resources.

All form of life requires food, water, favourable temperature to sustain life. Food provides energy for carrying out various metabolic activities. Water and temperature provide optimal condition inside the body.

Cell-wall is made up of cellulose - a non-living substance. Hence, cell-wall is a non-living part of the cell. Mitochondria is known as the powerhouse of the cell. They contain enzymes for cellular respiration. During cellular respiration, energy is released in the form of ATP (Adenosine triphosphate). Photosynthesis is performed by chlorophyll pigments present in the Chloroplast (a plastid). Ribosomes are associated with the synthesis of proteins from amino acids. Proteins are required by a cell for functions such as repair or directing chemical processes.

Flightless birds are birds that through evolution lost the ability to fly.New ecological influences selectively pressured different taxon to converge on flightless modes of existence by altering them morphologically and behaviorally.it is believed that the loss of flight is an easier transition for birds rather than the loss and regain of flight, which has never been documented in avian history. The wings are large, and have eleven primary feathers and low wing loading pigeons have strong wing muscles  and are among the strongest fliers of all birds. Columbidae have unique body feathers, with the shaft being generally broad, strong, and flattened, tapering to a fine point, abruptly.

Plant cells have large-sized vacuoles. Swelling of cells happens when the concentration of solutes inside the cell is greater than the concentration of solutes outside the cell. The water enters the cell thorugh Endosmosis (absorption). The shrinkage of cytoplasm occurs due to exo-osmosis in a hypertonicmedium.

Good health is the condition of complete physical fitness, free from disease, perfect mental health and perfect social well-being. Health is a state of being well enough to function well physically, mentally and socially. It depends on the surroundings or the environment. Living in a clean environment under good economic conditions, and social equality and harmony are important for individual health.

Cow pox is a viral disease in which small blisters develops on the body of animals with high fever.

Blood is flood connective tissue that helps in transport of oxygen and carbon dioxide. Haemoglobin present in RBC is responsible for oxygen transport.

The passage of water from a region of higher water concentration to a region of lower concentration through a semi-permeable membrane is called osmosis. The movement of water across the plasma membrane is affected by the amount of substance dissolved in water.

According to Thomas Henry Huxley, the protoplasm is the physical basis of life. It is the living substance inside in the cell that contains all the cell organelles. It is a thick fluid or jelly-like substance.

The correct option for the use of a large amount of fertilizers and pesticides is option C, which states that they maintain the natural replenishment of the soil. Let's analyze each option in detail:
A. They are eco-friendly.
- This statement is incorrect. Fertilizers and pesticides are not considered eco-friendly as they can have harmful effects on the environment and surrounding ecosystems.
B. They turn the fields barren after some time.
- This statement is correct. The excessive use of fertilizers and pesticides can lead to soil degradation and loss of fertility. This, in turn, can make the fields barren and unsuitable for agriculture.
C. They maintain the natural replenishment of the soil.
- This statement is incorrect. Fertilizers and pesticides do not contribute to the natural replenishment of the soil. In fact, their overuse can disrupt the natural nutrient cycling processes and negatively impact soil health.
D. They destroy the soil fertility.
- This statement is correct. The use of excessive fertilizers and pesticides can harm beneficial soil organisms, degrade soil structure, and lead to nutrient imbalances, ultimately reducing soil fertility.
Therefore, the correct option is C: (a) and (c) are correct.

Nervous tissue consists of nerve cells or neuron. Dendrite present on cell body receive stimulus and cyton converts stimulus into nerve impulses and carries impulses through axon.

Male Ascaris differ from female Ascaris in different way. Female Ascaris are longer in size, male Ascaris have curved posterior end and contain penial setae. 
Ascaris worms are sexually dimorphic, which means that there are differences in body size, shape, color, and so forth between males and females. For example, the males are shorter in length than the females. Male Ascaris worms range from 15-31 cm in length, with the length of female Ascaris worms ranging from 20-49 cm, with an average length of 30 cm. Also, the males have a smaller diameter than females. one of the simplest ways to determine if an Ascaris worm ismale or female is the presence or absence of a spicule

Mammals are vertebrates (which means they have a backbone or spine). Also known as “warm-blooded,” endothermic animals regulate their own body temperate which allows them to live in almost every climate on Earth. Have hair on their bodies. Mammals are viviparous as they Produce milk to feed their babies

Vaccine for small pox was discovered by Edward Jenner. Small pox is a viral disease. Vaccine of small pox includes suspension of dead or killed virus that develops antibodies within the body. Robert Koch was the first pathologist who established that diseases are mainly caused by pathogens. Disease causing microbes are called pathogens. Robert Brown discovered the nucleus. Rudolf Virchow made contributions to the cell theory.

Movement in our body is mainly caused by muscular tissue. Skeletal muscular tissues are joined with bones that cause movement due to contractile nature.

Eukaryotic cells (Eu means true; karyon means membrane) have a distinct nucleus, nucleolus and a nuclear membrane. Nucleoid is a part of prokaryotic cells.

Poultry farming is undertaken to raise egg and chicken production. Poultry farming is the process of raising domesticated birds such as chickens, ducks, turkeys and geese for the purpose of farming meat or eggs for food. Poultry are farmed in great numbers with chickens being the most numerous.More than 50 billion chickens are raised annually as a source of food, for both their meat and their eggs Chickens raised for eggs are usually called layers while chickens raised for meat are often called broilers. Poultry Farming can be kept by enthusiastic individuals in a back garden or on an allotment, or intensive farming production systems with a large acreage and high turn-over.

The largest organelle in plants is the central vacuole. Up to about 90% can be filled by a vacuole in a plant cell.

The term protoplasm was coined by Johann Evangelist Purkinje in 1839. Protoplasm is the fluid medium inside a cell in which different cell organelles are present.

Method used to control pollution:
There are several methods that can be used to control pollution. Among the options given, the correct methods are:
1. Installation of gobar gas plant:
- Gobar gas plants, also known as biogas plants, convert animal waste (gobar) into biogas, which can be used as a clean and renewable source of energy.
- This helps in reducing the pollution caused by the burning of fossil fuels and also provides an alternative energy source for cooking and heating.
2. Conversion of organic waste and fecal material into compost:
- Organic waste and fecal material can be converted into compost through composting.
- Composting is a natural process where organic waste is broken down by microorganisms to produce nutrient-rich compost.
- Compost can be used as a soil conditioner, reducing the need for chemical fertilizers and preventing the pollution caused by their production and use.
Therefore, the correct answer is option B: (a) and (d) are correct.

Both Asthma and Diabetes are chronic diseases as they last for long duration and adversely affect the health of an individual. Diabetes is a group of metabolic disorders in which a person has high blood sugar levels over a prolonged period. Asthma is a common long-term inflammatory disease of the airways of the lungs.

Acute diseases such as common cold last only for a short duration.

Amphibians are more advanced than fishes because of three chambered heart and lungs for respiration in place gills. 
Amphibianshave three-chambered heart and lungs for respiration, while fishes have two-chambered heart and gills for respiration. Well they have limbs and lungs, which  consider to be more complex.fish,amphibians, and reptiles are water creatures, so when they beathe water cleans their air supply, which makes their imune system weak air beathers are used to pollution which means they have a stronger immune system.

The scientific name of organisms consists of two words, the genus and species name. biological name of wheat is Triticum aestivum. Solanum tuberosum is the biological name of potato.

Carbohydrate is present in rice and potato in large quantity. Carrots are rich in beta-carotene, which is converted into vitamin A in the liver. Groundnut contains larger quantity of fat. It is the major oilseed of India. 

Plasma membrane is called semi-permeable because it is selectively permeable and regulates the entry and exit of substances. It allows entry of selective substances into the cell and allows exit of selective substances from the cell.

Dietary requirement of protein increases during lactation. Protein is called as body building food. Protein is required in higher quantity during lactation period after the parturition (the action of giving birth to young). Milk contains all the nutrients required for the growth of a baby.

Beekeeping or apiculture is the maintenance of honey bee colonies, commonly in man-made hives, by humans. A beekeeper (or apiarist) keeps bees in order to collect their honey and other products that the hive produces (including beeswax, propolis, pollen, and royal jelly), to pollinate crops, or to produce bees for sale to other beekeepers. A location where bees are kept is called an apiary or "bee yard."

Lysosome is called as the suicide bag of the cell as it contain enzymes for hydrolysis of all cell components in case of injury. It plays a minor role in cell death. It was discovered and named by Belgian biologist Christian de Duve. De Duve had termed the organelles as the "suicide bags" or "suicide sacs" of the cells. He received the Nobel Prize in Medicine in 1974 for his discovery.

Plant cells can be larger than animal cells. Size of an animal cell varies from 10 to 30 micrometers while that of a plant cell ranges from 10 to 100 micrometers.