CBSE Class 9 Science Advanced Biology Fundamental Unit of Life MCQs Set 01

Answer: (c) Robert Hooke

Explanation:
1. In 1665 Robert Hooke looked at a thin slice of cork through a microscope and saw many tiny box-like compartments.
2. He called them cells. Schleiden and Schwann gave the cell theory much later, and Leeuwenhoek was the first to see living cells.
3. So the first person to observe a cell was Robert Hooke.

Teacher's Note:
1. Link each name with one fact: Hooke saw cork cells, Leeuwenhoek saw living cells, Schleiden and Schwann framed the cell theory.
2. The cork cells Hooke saw were dead, which is why he saw only empty walls.

Answer: (a) Robert Hooke

Explanation:
1. The name 'cell' comes from the Latin word cellula, meaning a small room.
2. Robert Hooke used it for the little compartments he saw in cork, and described them in his book Micrographia.
3. The answer is Robert Hooke.

Teacher's Note:
1. Remember the book name Micrographia together with Hooke.
2. Weismann, Cuvier and Darwin are known for other work in biology, not for naming the cell.

Answer: (c) Nucleoplasm + cytoplasm

Explanation:
1. Protoplasm is the entire living substance of the cell.
2. It consists of the nucleoplasm (inside the nucleus) together with the cytoplasm (outside the nucleus).
3. So protoplasm = nucleoplasm + cytoplasm, which is option (c).

Teacher's Note:
1. Protoplasm is the sum of the two parts, not their difference.
2. Cytosol is only the watery part of the cytoplasm, so it cannot be the whole protoplasm.

Answer: (b) Study of structure and composition of cell

Explanation:
1. The Greek word kytos means cell, so cytology is the study of cells.
2. It covers the structure and the chemical make-up of cells of both plants and animals.
3. The answer is study of structure and composition of cell.

Teacher's Note:
1. Cytology is wider than the study of the cytoplasm alone.
2. It is not limited to plant or animal cells.

Answer: (b) Felix Dujardin

Explanation:
1. In 1835 the French biologist Felix Dujardin saw the living jelly-like substance inside cells and named it sarcode.
2. Purkinje later introduced the word 'protoplasm' (1839). Robert Hooke discovered the cell and Robert Brown discovered the nucleus.
3. So protoplasm was discovered by Felix Dujardin.

Teacher's Note:
1. Keep the pairs straight: Hooke - cell, Brown - nucleus, Dujardin - protoplasm.
2. Purkinje introduced the word 'protoplasm' in 1839, but the living substance itself was discovered by Dujardin.

Answer: (c) Schleiden and Schwann

Explanation:
1. The botanist M. J. Schleiden and the zoologist Theodor Schwann put forward the cell theory.
2. Rudolf Virchow later added that new cells arise from pre-existing cells.
3. The answer is Schleiden and Schwann.

Teacher's Note:
1. Schleiden studied plants and Schwann studied animals, so together they covered all organisms.
2. Morgan and Haldane are famous for work in genetics.

Answer: (a) They synthesize components of living protoplasm from nonliving materials.

Explanation:
1. Autonomous means self-governing. A cell can build the components of its own living protoplasm from non-living raw materials, so it can work independently.
2. Options (c) and (d) name shapes of cells and say nothing about independence. Growing alone (b) is a feature of living things, not the reason for autonomy.
3. So the answer is option (a). The printed key gave (d), which is not a reason at all.

Teacher's Note:
1. The idea behind this question is that every cell is a self-contained working unit.
2. Look for the option that gives a reason; shapes cannot be a reason here.

Answer: (c) PPLOs

Explanation:
1. PPLOs (pleuropneumonia-like organisms), such as Mycoplasma, are only about 0.1 µm across.
2. Bacteria and blue-green algae are larger, and the human egg is a large cell.
3. The answer is PPLOs.

Teacher's Note:
1. Mycoplasma is the standard example of the smallest cell.
2. The largest cell is an ostrich egg, the smallest is a PPLO.

Answer: (b) Nerve cell

Explanation:
1. A nerve cell has a long fibre that may reach a metre or more in length.
2. Bacteria and viruses are microscopic, and muscle cells are much shorter than a long nerve cell.
3. The answer is nerve cell.

Teacher's Note:
1. Think of the nerve that runs from the spinal cord to the foot: it is a single cell.
2. In plants, the longest cell is the hemp fibre.

Answer: (d) Virus

Explanation:
1. A typical virus measures a few tens to a few hundred nanometres.
2. A mitochondrion is about a micrometre, a bacterium a few micrometres and a mammalian cell tens of micrometres.
3. So the smallest is the virus.

Teacher's Note:
1. Compare sizes in the same unit before choosing.
2. Remember that viruses are not true cells; they are smaller than the smallest cell, the PPLO.

Answer: (a) Protein

Explanation:
1. Aleuroplasts are a type of leucoplast.
2. Amyloplasts store starch, elaioplasts store oil and aleuroplasts store protein.
3. The answer is protein.

Teacher's Note:
1. Use the prefix: amylo - starch, elaio - oil, aleuro - protein (aleurone grains).
2. All three are colourless plastids found in underground or storage parts.

Answer: (b) Mitochondria

Explanation:
1. Mitochondria make and store energy in the form of ATP.
2. For this reason they are called the power house or the storage battery of the cell.
3. The answer is mitochondria.

Teacher's Note:
1. A battery stores energy, and ATP is the energy store of the cell.
2. Chloroplasts trap light energy but are not called the battery.

Answer: (a) SER

Explanation:
1. Smooth endoplasmic reticulum has enzymes that change harmful drugs and poisons into harmless forms.
2. This is why liver cells have plenty of SER.
3. The rough ER makes proteins and the Golgi body packages materials, so the answer is SER.

Teacher's Note:
1. Smooth = lipids, steroids and detoxification; rough = proteins.
2. This function is not listed in the chapter text, so learn it as an extra point.

Answer: (c) ER

Explanation:
1. The endoplasmic reticulum is a network of membranes that gives internal support to the cytoplasm.
2. Lysosomes digest, mitochondria release energy and plastids trap light energy.
3. The answer is ER.

Teacher's Note:
1. The chapter lists 'internal support to the cytoplasm' among the functions of ER.
2. Do not mix it up with the cytoskeleton, which is made of fibrous proteins.

Answer: (a) Golgi body

Explanation:
1. The phragmoplast makes the cell plate that divides a plant cell during cell division.
2. The material for the cell plate is supplied by vesicles of the Golgi body.
3. The answer is Golgi body.

Teacher's Note:
1. Remember: Golgi helps in forming the cell plate and the cell wall material.
2. Glyoxysomes and peroxisomes have no role in cell-plate formation.

Answer: (d) both (A) & (B)

Explanation:
1. Slide adjustment here means bringing the slide into focus. We first move the body tube with the coarse adjustment screw.
2. Then we sharpen the image with the fine adjustment screw.
3. The base only supports the microscope, so the answer is both (A) and (B).

Teacher's Note:
1. Coarse first, fine second, is the usual order of focusing.
2. The base carries the weight of the instrument and plays no part in focusing.

Answer: (a) Jansen and Janssen

Explanation:
1. The first compound microscope was made in 1590 by the Dutch spectacle makers Hans and Zacharias Janssen.
2. Hooke and Brown used microscopes later, but they did not invent it.
3. The answer is Janssen and Janssen.

Teacher's Note:
1. Note the year 1590 along with the name.
2. The electron microscope was designed much later (1932) by Knoll and Ruska.

Answer: (d) Ribosomes

Explanation:
1. Bacteria are prokaryotes. They have no true nucleus and no membrane-bound organelles such as the Golgi apparatus or mitochondria.
2. Ribosomes are present in every kind of cell, including bacteria (70S type).
3. The answer is ribosomes.

Teacher's Note:
1. Ribosomes are the only organelles found in all cells.
2. Prokaryotes lack every membrane-bound organelle.

Answer: (d) Loss of water from grapes by osmosis

Explanation:
1. A concentrated sugar solution is hypertonic to the grape cells.
2. Water moves out of the grapes through their semipermeable membranes by osmosis, from the dilute side to the concentrated side.
3. Losing water makes the grapes shrink, so the answer is loss of water from grapes by osmosis.

Teacher's Note:
1. A cell placed in a hypertonic solution loses water and shrinks.
2. The same happens to a raisin-making grape left in sugar syrup.

Answer: (a) Water molecules move from the more dilute solution to the less dilute solution

Explanation:
1. In osmosis only the solvent, water, crosses the semipermeable membrane.
2. It moves from the region with more water (the more dilute solution) to the region with less water (the less dilute, that is more concentrated, solution).
3. So the correct statement is option (a); options (b) and (d) are wrong because the solute cannot cross the membrane.

Teacher's Note:
1. Water always moves toward the more concentrated solution.
2. The semipermeable membrane stops the solute but lets water pass.

Answer: (b) The cell membrane disintegrates

Explanation:
1. Plasmolysis needs a living, selectively permeable cell membrane so that water can leave by osmosis.
2. Boiling kills the cells and breaks down the cell membrane, which then no longer controls the passage of water.
3. So the answer is the cell membrane disintegrates.

Teacher's Note:
1. Only living cells can show osmosis and plasmolysis.
2. The cell wall is fully permeable in any case, so it is not the cause.

Answer: (c) suction pressure

Explanation:
1. Suction pressure = osmotic pressure − turgor pressure.
2. When a cell is fully turgid, the turgor pressure (and the equal and opposite wall pressure) becomes equal to the osmotic pressure.
3. Then suction pressure = 0, so it is suction pressure that is zero. Osmotic pressure still remains. (The printed key gave (d), which is wrong.)

Teacher's Note:
1. Suction pressure is the pull of a cell for water. A completely full cell cannot take in more water.
2. Remember the formula SP = OP − TP.

Answer: (b) hypotonic solutions

Explanation:
1. In a hypotonic solution the outside is more dilute than the cell contents.
2. Water enters the liver cells by osmosis and they swell. An animal cell has no cell wall, so it may even burst.
3. The answer is hypotonic solution.

Teacher's Note:
1. Hypo means less: less solute outside, so water flows in.
2. 'Isothermal' is not a term for a type of solution concentration.

Answer: (d) All of the above

Explanation:
1. The matrix of a mitochondrion holds the enzymes of the Krebs cycle.
2. It also contains a circular DNA, RNA and 70S ribosomes, because mitochondria make some of their own proteins.
3. So the answer is all of the above.

Teacher's Note:
1. This is why mitochondria are called semi-autonomous.
2. The cristae and oxysomes are on the inner membrane, while these items are in the matrix.

Answer: (d) All of the above

Explanation:
1. A mitochondrion has its own circular DNA, its own 70S ribosomes and the machinery to make some of its proteins.
2. Because it can do part of its own work but still depends on the nucleus for the rest, it is called semi-autonomous.
3. So the answer is all of the above.

Teacher's Note:
1. Semi means partly: partly independent of the nucleus.
2. Plastids are semi-autonomous for the same reasons.

Answer: (d) Both A and B

Explanation:
1. When tomatoes and chillies ripen, their green chloroplasts lose chlorophyll and change into red or yellow chromoplasts.
2. The carrot root grows underground, so its chromoplasts do not come from chloroplasts.
3. The answer is both A and B.

Teacher's Note:
1. Chromoplasts can arise from chloroplasts when green fruit ripens.
2. Think of a green tomato turning red.

Answer: (b) Prokaryotes

Explanation:
1. The ER is present in all eukaryotic cells: animals, plants, protists and fungi.
2. Prokaryotes have no membrane-bound organelles, so they have no ER.
3. The answer is prokaryotes.

Teacher's Note:
1. Mammalian red blood cells also lack the ER.
2. Prokaryotes lack all membrane-bound organelles.

Answer: (d) Endoplasmic reticulum

Explanation:
1. The network of the endoplasmic reticulum acts as a supporting framework for the cytoplasm.
2. Ribosomes make proteins, Golgi bodies package materials and lysosomes digest.
3. The answer is endoplasmic reticulum.

Teacher's Note:
1. Match each organelle with its job: ER - support and transport, ribosome - protein, Golgi - packaging, lysosome - digestion.
2. This is one of the listed functions of the ER.

Answer: (b) Nucleolus

Explanation:
1. The nucleolus makes ribosomal RNA and puts together the two ribosomal subunits, which leave through the nuclear pores.
2. It is the store house of RNA.
3. The answer is nucleolus.

Teacher's Note:
1. The nucleus contains the nucleolus, but the specific site for ribosome making is the nucleolus.
2. The ER only carries ribosomes on its surface.

Answer: (c) Ribosomes

Explanation:
1. Ribosomes read the instructions carried by mRNA and join amino acids into proteins.
2. This is why ribosomes are called protein factories.
3. The answer is ribosomes.

Teacher's Note:
1. Ribosomes may lie free or on the rough ER.
2. The Golgi apparatus only modifies and packages proteins.

Answer: (c) Mitochondria as powerhouse and Golgi as a cargo sorting facility

Explanation:
1. Mitochondria supply energy, so they are the power house of the city.
2. The Golgi apparatus sorts, packs and dispatches products, like a cargo sorting facility.
3. In (a) ribosomes are protein factories, not slaughter houses, in (b) the nucleus is the control centre, and in (d) the nucleus is not a slaughter house. The answer is (c).

Teacher's Note:
1. Lysosomes are the better analogy for waste disposal.
2. Check both halves of each statement before choosing.

Answer: (a) nucleus, mitochondria, chloroplast, cytoplasm

Explanation:
1. Nucleic acids are DNA and RNA. The nucleus has DNA, mitochondria and chloroplasts have their own DNA, and the cytoplasm has RNA (mRNA, tRNA and ribosomes).
2. Glyoxysomes, peroxisomes and Golgi bodies have no nucleic acid.
3. So the right set is nucleus, mitochondria, chloroplast, cytoplasm.

Teacher's Note:
1. Remember the three places where DNA is found: nucleus, mitochondria and plastids.
2. Single-membrane organelles do not contain nucleic acids.

Answer: (c) Eukaryotes

Explanation:
1. Microtubules make up spindle fibres, centrioles, cilia and flagella of eukaryotic cells.
2. Bacteria, viruses and Mycoplasma do not have this system.
3. The answer is eukaryotes.

Teacher's Note:
1. Microtubules need a cytoskeleton, which prokaryotes lack in this form.
2. They help in movement inside the cell.

Answer: (c) centriole

Explanation:
1. Plant cells have a large vacuole and a nucleus.
2. Centrioles are absent from plant cells (they occur only in some lower plants). Vitamin D is a vitamin, not a cell structure, so it is not a candidate here.
3. The structure not found in plant cells is the centriole.

Teacher's Note:
1. Centrioles belong to the animal cell and take part in cell division.
2. Read 'structure' carefully: it rules out the vitamin.

Answer: (b) Plastids

Explanation:
1. Cell membrane and nucleolus are present in both plant and animal cells.
2. Vacuoles are present in both too, though they are small in animals. Plastids occur only in plant cells.
3. The answer is plastids.

Teacher's Note:
1. Cell wall, plastids and a large central vacuole are the three typical plant features.
2. Among the choices given, only plastids are completely absent from animal cells.

Answer: (c) Ribosome

Explanation:
1. Mitochondria and plastids are bounded by two membranes, and lysosomes by one unit membrane.
2. Ribosomes are non-membranous granules of RNA and protein.
3. The answer is ribosome.

Teacher's Note:
1. Non-membranous organelles: ribosomes, centrosome and microtubules.
2. 'Unit membrane' means a single membrane.

Answer: (b) Metaphase

Explanation:
1. In prophase the chromosomes coil up and become visible.
2. In metaphase they line up on the equator of the cell; in anaphase the chromatids separate and move to the poles.
3. So chromosomes reach the equator in metaphase. (The printed key gave (c), which is wrong.)

Teacher's Note:
1. Memory aid: Metaphase - Middle.
2. The order of mitosis is prophase, metaphase, anaphase, telophase.

Answer: (d) DNA, mRNA, tRNA

Explanation:
1. DNA is the longest, because it carries the genes of the entire chromosome.
2. mRNA is a copy of one gene, so it is shorter than DNA, and tRNA is the smallest, only about 75 to 90 nucleotides long.
3. So the decreasing order is DNA, mRNA, tRNA.

Teacher's Note:
1. DNA > mRNA > tRNA is the order to remember.
2. tRNA is small enough to carry just one amino acid.

Answer: (c) G₁, S, G₂

Explanation:
1. The interphase of the cell cycle has three phases. In G₁ the cell grows, in S the DNA is copied and in G₂ it prepares to divide.
2. There is no G₃ phase.
3. So the sequence is G₁, S, G₂.

Teacher's Note:
1. G stands for gap and S for synthesis of DNA.
2. After G₂ the cell enters mitosis (M phase).

Answer: (c) leads to formation of parental type of daughter cells

Explanation:
1. In mitosis each cell divides into two daughter cells with the same number of chromosomes and the same genes as the parent.
2. Recombination and reduction of chromosome number happen in meiosis, which forms gametes.
3. The answer is leads to formation of parental type of daughter cells.

Teacher's Note:
1. Mitosis is called equational division.
2. Meiosis is the one with crossing over and reduction.