Directions: In the following questions, a statement of assertion is followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.
Q.1. Assertion: Organisms are made up of cells.
Reason: Cells are structural unit of living organisms. A cell keeps its chemical composition steady within its boundary.
AnswerAnswer: (a) Cells are the basic structural and functional unit of organism.
Q.2. Assertion: Specialization of cells is useful for organism.
Reason: It increases the operational efficiency of an organism.
AnswerAnswer: (a) Specialization of the cell increases the efficiency of the cell for a particular function.
Q.3. Assertion: The number of cells in a multicellular organism is inversely proportional to size of body.
Reason: All cells of biological world are alive.
AnswerAnswer: (d) The size and shape of the cell in multicellular organism depends upon the location and function performed by them.
Q.4. Assertion : Living organisms possess specific individuality with the definite shape and size.
Reason : Both living and non living entities resemble each other at the lower level of organisation.
AnswerAnswer: (b) All living organisms have definite shape and size and all show specific individuality with an orderly mannered organisation whereas at the lower level of organisation, both the living and non living are made up of atoms.
Q.5. Assertion : It is important that the organisms should have cell.
Reason : A cell keeps its chemical composition steady within its boundary.
AnswerAnswer: (a) Metabolic reactions of a living organism can occur only in a delicately balanced environment in the non-living organisms. The cells are the life supporting chambers which have such a special environment. A living cell keeps its chemical composition steady within its boundary.
Q.6. Assertion: The number of cells in a multicellular organism is inversely proportional to the size of
Reason: All the cells in the biological world are of same size.
AnswerAnswer: (d) Number of cells in a multicelluar organism are directly proportional to the size of the body. On the other hand, it is a fact that cell vary greatly in their size. Mycoplasma cells are the smallest, ranging from 0.1 to 0.3μm, whereas human cells, generally range from 20 to 30μm. Nerve cells are the longest.
Q.7. Assertion: Cell is an open system.
Reason: Cell receives a number of materials including energy containing nutrients from outside.
AnswerAnswer: (a) Cell is an isothermal open system as all the parts of the cell at any given time maintains the same temperature and pressure. Cell is an open system in which materials and energy are transferred between organisms and the exterior environment.
Q.8. Assertion: Smaller cells are usually metabolically active cells.
Reason: Smaller cell nucleocytoplasmic ratio and surface volume ratio is higher.
AnswerAnswer: (a) Metabolically active cells are usually smaller due to higher nucleocytoplasmic ratio and higher surface volume ratio. The former will allow the nucleus to have better control of metabolic activities, while the latter will allow quicker exchange of materials between the cells and its outside environment.
Q.9. Assertion: Rudolf Virchow modified the hypothesis of cell theory given by Schleiden and Schwann.
Reason : Cell theory says that all cells arise from pre-existing cells.
AnswerAnswer: (b) Schleiden and Schwann together formulated the cell theory. The theory however, did not explain as to how new cells were formed. Rudolf Virchow (1855) first explained that cells divided and new cells are formed from pre-existing cells (Omins cellua e cellua). He modified the hypothesis of Schleiden and Schwann to give the cell theory a final shape. The present cell theory states that: (i) all living organism are composed of cells and products of cells. (ii) all cells arise from preexisting cells.
Q.10. Assertion: Schleiden and Schwann were the first to observe the cells and to put forward cell theory.
Reason: The cells are always living unit.
AnswerAnswer: (d) They are credited with cell theory but the cells are not always the living unit. Cells die and still remain functional such as horny cells in animal and xylem vessels in plants.
Q.11. Assertion: As per Schwann, cell wall is a unique character of the plant cell.
Reason: Body of plants and animals are composed of cells and products of cells.
AnswerAnswer: (b) Based on his studies, Schwann proposed the hypothesis that the bodies of animal and plants are composed of cells and products of cells. Schleiden and Schwann together formulated the cell theory. Cell theory as understood is (i) All living organism are composed of cells and products of cells and (ii) all cells arise from pre-existing cells.
Q.12. Assertion: Eukaryotic cells have membrane bound organelles.
Reason: Prokaryotic cells lack membrane bound organelles.
AnswerAnswer: (b) Eukaryotic cells which have membrane bound distinct structures called organelles like nucleus, endoplasmic reticulum (ER), Golgi complex, lysosomes, mitochondria, microbodies and vacuoles. These are found in all protists, plants, animals and fungi. Prokaryotic cells lack such membrane bound organelles. Prokaryotic cells occur in bacteria, archaea, blue-green algae, mycoplasma and PPLO. Genetic material in these cells lies naked in the cytoplasm.
Q.13. Assertion: Ribosomes are non-membrane bound organelles found in the prokaryotic cells only.
Reason: These are present only in the cytoplasm.
AnswerAnswer: (d) Ribosomes are non-membrane bound organelles found in eukaryotic as well as prokaryotic cells. Within the cell, ribosomes are found not only in the cytoplasm but also within the two organelles – chloroplasts (in plants) and mitochondria and on rough ER.
Q.14. Assertion: Eukaryotic cells have more DNA than prokaryotic cells.
Reason: Eukaryotes are genetically more complex than prokaryotes.
AnswerAnswer: (a) Eukaryotic cells have more DNA than prokaryotic cells because in eukaryotic cells complex chromosomes are composed of DNA and histone proteins. But in prokaryotic cells, histone protein is absent.
Q.15. Assertion: Prokaryotes have a one envelop system.
Reason: There is not even a single membrane that surrounds the prokaryotic cell.