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Q1. Cork is obtained from which part of a plant?
Cork is obtained from the bark of the cork oak tree (Quercus suber). The bark is the outermost protective layer of the tree. Cork is made of dead cells and is used for making bottle stoppers, insulation, and many other products.
Q2. The shape of a cell depends on its:
The shape of a cell depends on its function. For example, nerve cells are long and branched to transmit signals, muscle cells are spindle-shaped for contraction, and red blood cells are disc-shaped to carry oxygen. The shape is adapted to perform specific functions efficiently.
Q3. Which scientist discovered free-living cells in pond water?
Antonie van Leeuwenhoek discovered free-living cells in pond water. He observed tiny organisms (which he called “animalcules”) in pond water, rain water, and other samples. He is known as the “Father of Microbiology” for his work with microscopes.
Q4. Unicellular organisms are those which consist of:
Unicellular organisms are those that consist of only one cell. This single cell performs all life functions like nutrition, reproduction, and excretion. Examples include Amoeba, Paramecium, and Chlamydomonas. All activities of life occur within this single cell.
Q5. Who discovered the nucleus in the cell?
Robert Brown discovered the nucleus in the cell in 1831. He was studying orchid cells when he noticed a dark, distinct structure inside the cell. He named this structure the “nucleus.” This was an important discovery in understanding cell structure.
Q6. Cells seen in onion peels of different sizes appear:
Cells seen in onion peels of different sizes appear similar in structure. Onion peel cells are rectangular in shape with a distinct cell wall, nucleus, and vacuole. Even though the onion pieces may be of different sizes, the basic structure of the cells remains the same.
Q7. Why is onion peel placed in water during slide preparation?
Onion peel is placed in water during slide preparation to prevent it from folding and drying out. Water keeps the peel moist and flat, making it easier to observe under the microscope. It also helps in spreading the peel evenly on the slide.
Q8. The cell is called the structural and functional unit of life because:
The cell is called the structural and functional unit of life because all living organisms are made up of cells, and all life functions (nutrition, respiration, excretion, reproduction, etc.) occur within cells. Cells are the basic building blocks of all living things.
Q9. Which human cell is male gamete?
The male gamete in humans is the sperm cell. It is produced in the testes and is responsible for fertilizing the female gamete (ovum). Sperm cells are small, have a tail for movement, and contain the male genetic material.
Q10. The structures seen in onion peel are:
The structures seen in onion peel are cells. Onion peel is made up of a single layer of rectangular cells. Each cell has a distinct cell wall, a large central vacuole, and a nucleus. These cells are easily visible under a microscope.
Q11. Which instrument was used by Robert Hooke to observe cells?
Robert Hooke used a self-designed compound microscope to observe cells. He made his own microscope with a magnification of about 30x. Using this microscope, he observed thin slices of cork and saw small box-like structures, which he named “cells.”
Q12. Onion peel is first observed under which microscope power?
Onion peel is first observed under low power to get a general view of the cells and their arrangement. Then, a specific area is focused under high power to observe detailed structures like the nucleus, cell wall, and vacuole. This is the standard procedure for microscope observation.
Q13. Cells arise from:
Cells arise from pre-existing cells. This is a key principle of the cell theory, as stated by Virchow: “Omnis cellula e cellula” (All cells arise from cells). New cells are formed by cell division (mitosis and meiosis).
Q14. A cell can live and function because of its:
A cell can live and function because of its organelles. Organelles are specialized structures inside the cell that perform specific functions like energy production (mitochondria), protein synthesis (ribosomes), and waste removal (lysosomes). Without organelles, the cell cannot carry out life processes.
Q15. The nucleus was discovered in which year?
The nucleus was discovered by Robert Brown in 1831. He was examining orchid cells when he observed a distinct, dark structure inside the cell. He called it the “nucleus.” This discovery was significant in understanding the structure of plant cells.
Q16. Who suggested that all cells arise from pre-existing cells?
Rudolf Virchow suggested that all cells arise from pre-existing cells. He stated, “Omnis cellula e cellula” (All cells arise from cells). This was an important addition to the cell theory, emphasizing that new cells are formed only by division of existing cells.
Q17. What did the cork structure resemble according to Hooke?
According to Robert Hooke, the cork structure resembled a honeycomb. He observed many small, box-like chambers arranged in rows, which reminded him of the cells (rooms) in a monastery. He named these structures “cells.”
Q18. In which year was cell theory expanded by Virchow?
Cell theory was expanded by Rudolf Virchow in 1855. He added the principle that all cells arise from pre-existing cells. This completed the cell theory, which was originally proposed by Schleiden and Schwann in 1838-39.
Q19. All living organisms are made up of:
All living organisms are made up of cells. Cells are the basic structural units of life. Some organisms are unicellular (made of one cell), while others are multicellular (made of many cells). Cells form tissues, tissues form organs, and organs form organ systems.
Q20. All cells have:
All cells have different organelles that perform specific functions. Different types of cells have different organelles depending on their function. For example, muscle cells have more mitochondria for energy, and plant cells have chloroplasts for photosynthesis.
Q21. Do all cells look alike in shape and size?
No, all cells do not look alike in shape and size. Cells vary greatly in shape and size depending on their function. For example, nerve cells are long and branched, red blood cells are disc-shaped, and muscle cells are spindle-shaped. Size also varies from tiny bacteria (few micrometres) to large ostrich eggs.
Q22. Which cell has a changing shape?
Amoeba has a changing shape because it does not have a fixed cell wall. It moves and feeds by extending pseudopodia (false feet), which causes its shape to change continuously. This is why Amoeba is called an irregular-shaped cell.
Q23. Which precaution is necessary while placing the cover slip?
While placing the cover slip, it is necessary to avoid air bubbles. Air bubbles can interfere with the observation by distorting the image under the microscope. To avoid bubbles, the cover slip should be placed gently at an angle and lowered slowly.
Q24. Which cell has a typical elongated shape?
Nerve cells (neurons) have a typical elongated shape with long extensions called dendrites and axons. This elongated shape helps them transmit signals over long distances in the body. They can be up to a metre long in some cases, making them the longest cells in the human body.
Q25. Which organism is an example of a unicellular organism?
Amoeba is an example of a unicellular organism. It consists of a single cell that performs all life functions. Frogs, mango plants, and humans are all multicellular organisms made up of many cells.
Q26. Who coined the term ‘protoplasm’?
Purkinje coined the term ‘protoplasm’ in 1839. He used this term to describe the living substance inside the cell. Protoplasm includes the cytoplasm and the nucleus. It is the fluid-like substance where all life activities take place.
Q27. What is the thin outer layer of onion peel called?
The thin outer layer of the onion peel is called the epidermis. It is a single layer of cells that covers the surface of the onion scale leaf. This layer is easily peeled off and used for microscope observation.
Q28. The word ‘cell’ is derived from which language?
The word ‘cell’ is derived from the Latin word “cellula,” which means “a little room.” Robert Hooke used this term because the cork cells he observed reminded him of the small rooms (cells) in a monastery.
Q29. Which tool helps in transferring onion peel to the slide?
A camel hair paintbrush helps in transferring the onion peel to the slide. The thin and delicate onion peel can be easily lifted and placed on the slide using a wet brush. This prevents damage to the peel.
Q30. Waste removal in a cell is carried out by:
Waste removal in a cell is carried out by cell organelles. Lysosomes are responsible for digesting and removing waste materials from the cell. Other organelles like the vacuole also store waste temporarily before it is expelled.
Q31. The specific components inside a cell are called:
The specific components inside a cell are called cell organelles. Organelles are specialized structures that perform specific functions within the cell. Examples include mitochondria, ribosomes, and the nucleus.
Q32. Who observed cork cells for the first time?
Robert Hooke observed cork cells for the first time in 1665. He used a self-designed microscope to examine thin slices of cork and saw small, box-like structures. He named these structures “cells.”
Q33. Every multicellular organism starts life from a:
Every multicellular organism starts life from a single cell. In humans, this cell is the fertilized egg (zygote). This single cell undergoes repeated divisions and differentiation to form a complex multicellular organism.
Q34. In which year were cells first discovered?
Cells were first discovered by Robert Hooke in 1665. He observed cork cells under a microscope and described them in his book “Micrographia.” This was the first recorded observation of cells.
Q35. Cell organelles help in:
Cell organelles help in performing specific functions within the cell. Each organelle has a specific role—mitochondria produce energy, ribosomes make proteins, and the nucleus controls cell activities. Together, they keep the cell alive and functioning.
Q36. The basic building units of an onion bulb are called:
The basic building units of an onion bulb are cells. An onion bulb is made up of thousands of cells organized into tissues. The cells of onion peel are rectangular with distinct cell walls, nuclei, and vacuoles.
Q37. Division of labour in multicellular organisms means:
Division of labour in multicellular organisms means that different parts of the organism perform different functions. For example, the heart pumps blood, the lungs exchange gases, and the brain controls activities. This specialization allows the organism to function efficiently.
Q38. Which of the following is a unicellular organism mentioned in the text?
Chlamydomonas is a unicellular organism mentioned in the text. It is a type of green algae that consists of a single cell. It has flagella for movement and chloroplasts for photosynthesis. Earthworms, hydra, and dogs are all multicellular organisms.
Q39. In which year did Leeuwenhoek discover free-living cells?
Antonie van Leeuwenhoek discovered free-living cells in 1674. He observed these cells in pond water using his simple microscope. This was a significant discovery as it revealed the existence of microscopic life forms.
Q40. The electron microscope was discovered around:
The electron microscope was discovered around 1940. It uses a beam of electrons instead of light to magnify objects. This allows much higher magnification and resolution, making it possible to see cell organelles clearly.
Q41. Which microscope made it possible to see cell organelles clearly?
The electron microscope made it possible to see cell organelles clearly. It provides much higher magnification and resolution than light microscopes. With electron microscopy, detailed structures of organelles like mitochondria, ribosomes, and the endoplasmic reticulum can be observed.
Q42. In which year was the term ‘protoplasm’ coined?
The term ‘protoplasm’ was coined by Purkinje in 1839. He used this term to describe the living substance inside the cell. Protoplasm includes the cytoplasm and the nucleus and is considered the “living matter” of the cell.
Q43. The meaning of the word ‘cell’ is:
The word ‘cell’ means “a little room.” Robert Hooke used this term because the cork cells he observed looked like small rooms or chambers, similar to the cells (rooms) in a monastery. The Latin word “cellula” means “a little room.”
Q44. Robert Hooke observed cells in which material?
Robert Hooke observed cells in cork. He examined thin slices of cork under his self-designed microscope and saw small, box-like structures, which he called “cells.” This was the first recorded observation of cells.
Q45. Division of labour also occurs within a:
Division of labour also occurs within a cell. Different organelles inside the cell perform different functions—mitochondria produce energy, ribosomes make proteins, lysosomes digest waste, and the nucleus controls activities. This division of labour within the cell is essential for its survival.
Q46. The cell theory was presented in the years:
The cell theory was presented in 1838 and 1839. Matthias Schleiden (1838) proposed that all plants are made of cells, and Theodor Schwann (1839) proposed that all animals are made of cells. Together, they formulated the cell theory.
Q47. Who presented the cell theory?
The cell theory was presented by Matthias Schleiden and Theodor Schwann. Schleiden stated that all plants are made of cells, and Schwann stated that all animals are made of cells. Together, they proposed that the cell is the basic unit of life.
Q48. Multicellular organisms are made up of:
Multicellular organisms are made up of many cells. These cells are organized into tissues, organs, and organ systems. Examples include humans, animals, plants, and fungi. The cells in multicellular organisms are specialized for specific functions.
Q49. New cells are formed by the process of:
New cells are formed by the process of cell division. Cells divide to produce new cells for growth, repair, and reproduction. The two main types of cell division are mitosis (for growth and repair) and meiosis (for reproduction).
Q50. Which human cell is responsible for carrying messages?
Nerve cells (neurons) are responsible for carrying messages (signals) in the body. They have long extensions (axons and dendrites) that allow them to transmit electrical impulses over long distances. This enables communication between different parts of the body and the brain.