Biology MCQ Quiz - Objective Question with Answer for Biology - Download Free PDF

The correct answer is 1, 2, and 4 only.

Key Points

• Taproot system  
  • It is the main root of the primary root system, which grows vertically downwards.
  • Most of the dicotyledonous plants like dandelions, produce taproots and some of the roots are edible like carrots and beets, specialized for the storage of food. Hence, pair 1 is correct.
  • Taproot is nearly straight, thicker and taper in size, in the taproot system roots grow directly downwards.
• Fibrous root system
  • It is composed of large numbers of roots nearly equal in size; root systems of this type are found, for example, in grasses.
  • It is the characteristic feature of monocotyledonous plants which include cereal, crops, corn, etc. Hence, pair 2 is correct.
  • It is a network of small thin roots extending not deep into the soil, mainly close to the surface.
• Prop root system
  • These roots develop from the branches of the tree, hang downwards, and penetrate into the ground thereby supporting the tree. Hence, pair 3 is incorrect.
  • Example: Roots of the Banyan tree and Rubber plant.
• Stilt root system
  • Stilt roots are adventitious roots that grow from lower stem nodes and join and become deeper in the soil.
  • Plants are covered by winds, such as maize, sugarcane, and screwpine. Hence pair 4 is correct.

The correct answer is pulses.

• Nitrogen-fixing bacteria make a combination with cells of the roots of pulses.

Concept-

• Microorganisms that are capable of transforming atmospheric nitrogen into fixed nitrogen(compounds usable by plants such as ammonia) are called nitrogen-fixing bacteria.
• The process of transforming atmospheric nitrogen into fixed nitrogen is called nitrogen fixation.
• They are commonly found in soil or in aquatic environments.

Key Points

• The nitrogen-fixing bacteria are found in the roots of legumes in special structures called root nodules.
• Leguminous plants belong to the family Fabaceae.
• These plants form a symbiotic association with the soil bacteria called the Rhizobium, which lives in their roots, forming root nodules and fixing atmospheric nitrogen into the nitrates and nitrites for the plants and the plants provide nutrition to the bacteria.

Phototropism:

• Phototropism is the ability of a plant or other photosynthesizing organism, to grow directionally in response to a light source.
• Light-induced growth response in plants is called phototropism.
• Positive phototropism is the response of a plant toward a light source, while negative phototropism causes growth in the opposite direction.​
• Shoots or above-ground parts of plants generally display positive phototropism.

Geotropism:

• Geotropism is the growth of the parts of plants in response to the force of gravity.
• The root of a plant growing down into the ground is an example of geotropism.
• The upward growth of plant parts, against gravity, is called negative geotropism.
• The downward growth of roots is called positive geotropism.

Chemotropism:

• Chemotropism is the growth of a plant navigated by chemical stimulus from outside.
• If the growth response is towards the stimulus it is called positive chemotropism.
• If the growth response is away from the stimulus it is called negative chemotropism
• Chemotropism can be observed during the growth of the pollen tube towards the ovule.

​Hydrotropism:

It is a directed growth in response to water or moisture gradients and begins in the root cap with the sensing of the moisture gradient.
​EXPLANATION:
From the above, it is clear that the option 3 pair was not correctly matched because​Hydrotropism is a plant growth response in which the direction of growth is determined by stimulus or gradient in water concentration.

The correct answer is Cytokinin.
Key Points

• Cytokinin:
  • Cytokinin is defined as a number of plant hormones that influence growth and the stimulation of cell division.
  • Cytokinins are synthesized in the roots and are usually derived from adenine.
  • They move upward in the xylem (woody tissue) and pass into the leaves and fruits, where they are required for normal growth and cell differentiation.
  • Cytokinins also act in conjunction with auxin (another plant hormone) to retard senescence, which, at least in its early stages, is an organized phase of metabolism and not just a breakdown of tissue.
  • An example of senescence is the yellowing of isolated leaves, which occurs as proteins are broken down and chlorophyll is destroyed.
  • Cytokinins prevent yellowing by stabilizing the content of protein and chlorophyll in the leaf and the structure of chloroplasts.

Additional Information

• Insulin:
  • Insulin is a kind of hormone that regulates the level of sugar (glucose) in the blood and that is produced by the beta cells of the islets of Langerhans in the pancreas.
  • Insulin is secreted when the level of blood glucose rises after a meal.
  • When the level of blood glucose falls, the secretion of insulin stops, and the liver releases glucose into the blood.
  • Insulin was first reported in pancreatic extracts in 1921, having been identified by Canadian scientists Frederick G. Banting and Charles H. Best and by Romanian physiologist Nicolas C. Paulescu, who was working independently and called the substance “pancreatin.”
  • After Banting and Best isolated insulin, they began work to obtain a purified extract, which they accomplished with the help of Scottish physiologist J.J.R. Macleod and Canadian chemist James B. Collip. Banting and Macleod shared the 1923 Nobel Prize for Physiology or Medicine for their work.
• Thyroxin:
  • Thyroxine is one of the two major hormones secreted by the thyroid gland.
  • Thyroxine’s principal function is to stimulate the consumption of oxygen and thus the metabolism of all cells and tissues in the body.
  • Thyroxine is formed by the molecular addition of iodine to the amino acid tyrosine while the latter is bound to the protein thyroglobulin.
  • Excessive secretion of thyroxine in the body is known as hyperthyroidism, and the deficient secretion of it is called hypothyroidism.
• Estrogen:
  • Estrogen is a group of hormones that primarily influence the female reproductive tract in its development, maturation, and function.
  • There are three major hormones estradiol, estrone, and estriol, among the estrogens, and estradiol is the predominant one.
  • The major sources of estrogens are the ovaries and the placenta (the temporary organ that serves to nourish the fetus and remove its wastes); additional small amounts are secreted by the adrenal glands and by the male testes.
  • It is believed that the egg follicle (the saclike structure that holds the immature egg) and interstitial cells (certain cells in the framework of connective tissue) in the ovaries are the actual production sites of estrogens in the female.
  • Estrogen levels in the bloodstream seem to be highest during the egg-releasing period (ovulation) and after menstruation when tissue called the corpus luteum replaces the empty egg follicle.

The correct answer is More than one of the above.

Key Points

• The main role of the phloem tissue is to transport carbohydrates from sources to sinks through the sieve elements.
• Xylem is the tissue of vascular plants that transports water and nutrients from the soil to the stems and leaves.

Additional Information

• The plant vascular system is a complicated network of conducting tissues that interconnects all organs and transports water, minerals, nutrients, organic compounds, and various signaling molecules throughout the plant body.
• The vascular system is comprised of two main types of tissue - the xylem and the phloem.
  • The xylem distributes water and dissolved minerals upward through the plant, from the roots to the leaves.
  • The phloem carries food downward from the leaves to the roots.

Concept:

Photosynthesis: 

• The leaves have a green pigment called chlorophyll.
• It helps leaves to capture the energy of the sunlight.
• This energy is used to synthesise (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis.

In the presence of sunlight Carbon dioxide + water → Carbohydrate + oxygen.

• Some plants, green algae, and cyanobacteria can perform photosynthesis.
• The process of photosynthesis is commonly written as

                   6CO2 + 6H2O + Sun-Light → C6H12O6 + 6O2

Plant cells have a cell wall to protect them and make them rigid structure.

Explanation:

1. Plants convert energy from sunlight into food stored as carbohydrate’s - Correct

2. Plants have chlorophyll. - Correct

3. Plant cells do not have cell walls. - Incorrect.

Additional Information

In the plant cells, there are different components and organelles for specific functions-

• Cell Wall – It is a rigid layer composed of cellulose. It is the outermost layer of the cell, below this cell membrane is present. The primary function of the cell wall is to protect and provide structural support to the cell.
• Cell Membrane – It is a semi-permeable membrane that helps in regulating and the substance for entry and exit inside and outside the cell.
• Nucleus – It is a vital part of the cell as it contains all the information or DNA of the cell and their heredity information for growth and cell division.
• Vacuole – Most of the part of the plant cell is occupied by the vacuole. It is surrounded by Tonoplast. The vital role of the vacuole is to provide support again the pressure of the cell wall.
• Golgi apparatus – They act as a transport system in the cell, as they transport various molecules to a different part of the cell.
• Ribosomes – They are the sites of protein synthesis, also termed as the protein factory of the cell.
• Mitochondrion – They break the complex molecules and produce energy and hence called the powerhouse of the cell.
• Lysosomes – They are termed suicidal bags as they hold the enzymes that are capable to digest the whole cell itself.

The correct answer is Protein synthesis.

Key Points

• Ribosomes are membranous granular structures present in the cytoplasm.
• They were first observed under an electron microscope as dense particles by George Palade in the year 1953.
• Ribosomes are the site for ''protein synthesis'' so they are also called the ''protein factory'' of the cell.
• There are two types of ribosomes

1. Eukaryotic ribosomes - 80s - occurs in the cytoplasm of eukaryotic cell
2. Prokaryotic ribosomes - 70s - occur in the cytoplasm as well as are associated with the cell membrane of prokaryotic cell.

• The subunits of the ribosomes are:
  • 80s ribosomes - are made of 60s and 40s subunits.
  • 70s ribosomes - are made of 50s and 30s subunits.

Important Points

• Composition of the structure of ribosome:
• They are composed of ribonucleic acid (RNA) and proteins

Additional Information

• Photosynthesis: It is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. In this process, plant the chlorophyll, carbon dioxide, water, sunlight, and release oxygen.
• Synthesis of Fatty acids occurs in the cytoplasm.

The correct answer is Bile juice, Pancreatic juice.

Key Points

• Bile juice, Pancreatic juice secreted by the organs plays an important role in the digestion of fats.
• Bile juice is secreted by the liver.
  • It does not contain any types of enzymes.
  • The bile juice helps to make the food alkaline and break down the fat molecules.
• Pancreatic juice is secreted by the pancreas.
  • It contains enzymes like amylase, trypsin, pancreatic lipase, nucleases, amylase, and lipase.
  • Secretion of the Pancreatic juice is regulated by the hormones secretin and cholecystokinin.
• Lipase is the digestive enzyme of fat.
• Ptyalin is the digestive enzyme of the Saliva.
• Hydrochloric acid is produced naturally in the human stomach to help the digestion of food.

Concept:

Theory of endosymbiosis

• Symbiotic relationship, where one organism lives inside the other, is known as endosymbiosis. 

• The theory proposed that mitochondria and chloroplasts evolved from engulfed prokaryotes.

• A large anaerobic bacteria engulfed an aerobic prokaryote, which then formed an endosymbiotic relationship with the host, gradually developing into a mitochondrion.

• It is believed that chloroplasts originated from a cyanobacterial endosymbiont.

Explanation:

Similarities between Prokaryotic cells, Mitochondria, and Chloroplast:

• Mitochondria and chloroplast are of the same size as prokaryotic cells.

• Mitochondria and prokaryotic cells both have their own circular DNA.

• The ribosome of bacteria, mitochondria, and chloroplasts have a 70S type of ribosome.

• Divides by binary fission.

The correct answer is Whale.

Key Points

• Gills are respiratory organs found in most aquatic organisms.
• Gills can extract dissolved oxygen from water and excrete carbon dioxide.
• Gills can be found in Octopus, Squid, Clownfish, Tadpole, Prawn, etc.
• Lungs are the breathing organ of Whales.

Additional InformationRespiratory organs of different Animals:

• Vitamin K is a vitamin found in leafy green vegetables, broccoli, and Brussels sprouts.
• In the body, vitamin K plays a major role in blood clotting. So it is used to reverse the effects of “blood-thinning” medications when too much is given; to prevent clotting problems in newborns who don’t have enough vitamin K, and to treat bleeding caused by medications.

Tricks:

The correct answer is Calyx.

Key Points

• Flowers contain the plant’s reproductive structures.
• A typical flower has four main parts - or whorls - known as the calyx, corolla, androecium, and gynoecium.
• The outermost whorl of the flower has green, leafy structures known as sepals.
  • The sepals, collectively called the calyx, help to protect the unopened bud.

Important Points

• The second whorl is comprised of petals - usually, brightly coloured - collectively called the corolla.
• The number of sepals and petals varies depending on whether the plant is a monocot or dicot. 
  • In monocots, petals usually number three or multiples of three; in dicots, the number of petals is four or five, or multiples of four and five.
  • Together, the calyx and corolla are known as the perianth.
• The third whorl contains the male reproductive structures and is known as the androecium.
  • The androecium has stamens with anthers that contain the microsporangia.
• The innermost group of structures in the flower is the gynoecium, or the female reproductive component(s).
• The carpel is the individual unit of the gynoecium and has a stigma, style, and ovary.
  • A flower may have one or multiple carpels.

The correct answer is Cellulose.

• Plant cell walls are primarily made of cellulose.

Key Points

• Cellulose is the most abundant macromolecule on Earth.
  • Cellulose fibers are long, linear polymers of hundreds of glucose molecules.
  • These fibres aggregate into bundles of about 40, which are called microfibrils.

Additional Information

• Carbohydrates are the sugars, starches, and fibres found in fruits, grains, vegetables, and milk products.
  • A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H), and oxygen (O) atoms.
• Lipids are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells.
  • A lipid is a biomolecule that is soluble in nonpolar solvents.
• A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid also known as fat molecules in water, as in blood plasma or other extracellular fluids.
  • It consists of a Triglyceride and Cholesterol centre, surrounded by a phospholipid outer shell, with the hydrophilic portions oriented outward towards the surrounding water and lipophilic portions oriented inward toward the lipid centre.

The correct answer is jointed legs.

Arthropoda - 

• The word ‘arthropod’ means ‘jointed legs’.
• Ex: houseflies, spiders, scorpions, prawns, butterflies and crabs.

The Hierarchy of Classification of living organisms - 

• Living organisms are classified into five kingdoms, by Whittaker, i.e. 
  • ​Kingdom Monera,
  • Kingdom Protista,
  • Kingdom Fungi,
  • Kingdom Plantae,
  • Kingdom Animalia.
• Further classification is done by the following scheme: Kingdom, Phylum (for animals) / Division (for plants), Class, Order, Family, Genus, Species.
• Kingdom Animalia is further classified based on the extent and type of the body design differentiation found, as below: