Q 1 – What is the basic, functional and structural unit of life?
Ans. Cell
Q 2 – Which cell does not have a nucleus?’
Ans. Red blood cell
Q 3 – What is the name of the organism which can be seen only with the help of a microscope?
Ans. Microorganisms
Q 4 – What are the organisms which are composed of many cells packed together called?
Ans. Multicellular organisms
Q 5– What is the name of the powerhouse of the cell?
Ans. Mitochondria
Q 6 – Name one example of a prokaryotic cell.
Ans. Blue-green algae
Q 7 – Amoeba and Paramecium belong to which category of organisms?
Ans. Unicellular
Q 8 – Which instrument is used to observe cells?
Ans. Microscope
Q 9 – Why we do not sense any pain when we cut nails and hair?
Ans. Nails and hair are made up of dead cells.
Q 10 – What is the name of the living substance present in a cell?
Ans. Protoplasm
Q 11 – What is the other name of the cell membrane?
Ans. Plasma membrane
Q 12 – What is the name of the thread-like structure present in nucleoplasm?
Ans. Chromatin
Q 13 – What is the name of the cell which has a well-defined nucleus?
Ans. Eukaryotic cell
Q 14 – Name the two types of cells.
Ans. Prokaryotic cells and eukaryotic cells.
Q 15 – What is the function of cell wall?
Ans. A cell wall is a tough, rigid layer that surrounds some types of cells (plants and some bacterial cells). The major function of the cell wall is to provide rigidity, tensile strength, structural support, protection against mechanical stress and infection.
Q 16 – Name the parts of the nucleus and state their function.
Ans. The nucleus consists of three main parts nuclear membrane, nucleoplasm and nucleolus. The nucleus plays an important role during cell division. It also controls the activities of the cell.
Q 17 – What is an organ?
Ans. The structure that contains more than one type of tissue and is visible to the naked eyes are called organs
Q 18 – What do you mean by unicellular and multicellular organisms?
Ans. Organisms that consists of only one cell are called unicellular organisms while the organisms made up of more than one cell are called multicellular organisms.
Q 19 – Visit an agriculture extension centre in your area. Find out about genetically modified (GM) crops. Prepare a short speech for your class on this topic.
Ans. Genetically Modified (GM) crops have a great role to play in Indian agriculture when we need more from lesser resources. Transgenics have the potential to resist biotic and abiotic stresses and result in increased productivity in addition to better nutritional quality. The hue and cry on the impact of GM crops on biodiversity have created hypes regarding economic, social and ethical concerns. Though several workers have contradicted the fears expressed regarding the risks and hazards of GM crops, concerns on the safety of GM foods are still creating controversies. India must avoid taking extreme decisions and has to develop a symbiotic relationship between the public and private sectors, to use new technological inputs to complement the traditional methods for making an ‘Evergreen Revolution’.
Q 20 – Find out about Bt cotton from an agriculture expert (or from envfor.nic.in/divisions/csnrv/ btcotton/bgnote.pdf). Prepare a short note on its advantages/disadvantages.
Ans. Bt cotton is a Genetically Modified Organism (GMO) cotton variety, which produces an insecticide to bollworm. It is produced by Monsanto. Strains of the bacterium Bacillus thuringiensis produce over 200 different Bt toxins, each harmful to different insects. Most notably, Bt toxins are insecticidal to the larvae of moths and butterflies, beetles, cotton bollworms and ghtu flies but are harmless to other forms of life. The gene coding for Bt toxin has been inserted into cotton as a transgene, causing it to produce this natural insecticide in its tissues. In many regions, the main pests in commercial cotton are lepidopteran larvae, which are killed by the Bt protein in the genetically modified cotton they eat.
Advantages:
- It eliminates the need to use large amounts of broad-spectrum insecticides to kill these pests.
- It spares natural insect predators in the farm ecology.
- It kills only targeted pest.
Disadvantages:
- By cotton is ineffective against many cotton pests such as plant bugs, stink bugs, and aphids.
- GM seeds are expensive.
- GM crops cannot be use as fodder for cattles.
- Effectiveness up to 120 days, after that the toxin producing efficiency of the Bt gene drastically reduces.
Q 21 – Which organism is more efficient in its functioning—unicellular or multicellular? Why?
Ans. Multicellular organisms are more efficient in its functioning because labour is divided among the cells and have great capacity to survive than unicellular organisms.
Q 22 – Cells consist of many organelles, yet we do not call any of these organelles a structural and functional unit of living organisms. Explain.
Ans. Organelles cannot function outside the cell as an independent unit. They can perform their functions only when they are within the living cells
Q 23 – Talk to the senior biology teacher in your school or a neighbouring school. Find out if there are diseases that are passed on from parents to the offspring. Find out how these are carried out and also if these diseases can be treated. For this, you can also visit a doctor.
Ans. Diseases that are passed from parents to offspring are colour blindness, haemophilia, thalassemia, etc. Most of these diseases cannot be treated. (For more information search the internet).
Q 24 – What do you mean by unicellular and multicellular organisms?
Ans. Organisms that consists of only one cell are called unicellular organisms while the organisms made up of more than one cell are called multicellular organisms.
Q 25 – Give a brief description of the nucleus.
Ans. The nucleus is a dense round body found in the centre of an animal cell and mostly on the periphery of the plant cell. The nucleus controls all the activities in a cell.
Q 26 – What is nucleolus?
Ans. The aspherical body present at the centre of the nucleus is called the nucleolus.
Q 27 – What is the endoplasmic reticulum?
Ans. It is the system of a complex folded network of membranous tubes which connects the nuclear membrane with the plasma membrane. They allow the movement of substances within the cell.
Q 28 – What are cell organelles?
Ans. The tiny components present in the cytoplasm are called cell organelles.
Q 29 – What is a cell membrane?
Ans. The thin and delicate membrane surrounding the cell cytoplasm is called the cell membrane.
Q 30 – What are the main functional regions of a cell? Explain.
Ans. The main functional regions of a cell are:
- Plasma membrane: This is the membrane which makes the outer boundary of the cells. It is very thin, delicate and selectively permeable.
- Cytoplasm: Cytoplasm is viscous, transparent jelly-like substance of the cell. It contains cell organelles.
- Nucleus: Nucleus controls the working of the cell. It is a dense oval body lying in the protoplasm of the cell.
Q 31 – Define cell membrane and state its functions.
Ans. Cell membrane or plasma membrane is a thin, delicate membrane surrounding the cytoplasm.
Following are the functions of cell membrane:
- It separates the cells from one another and also separates the cells from the surrounding medium.
- It gives a definite shape to the cell.
- Being porous, it allows the movement of substances from both inside and outside the cells.
- Its porous structure helps in regulating the movement of materials through the cells.
Q 32 – Define the nucleus and state its major parts.
Ans. The nucleus is a dense round body found in the centre of an animal cell and mostly on the periphery of the plant cell. The nucleus controls all the activities in the cell-like digesting movement of substances within the cell. The nucleus also controls the process of cell division. This is the reason the nucleus is also known as the ‘brain of the cell’.
The nucleus consists of four major parts. They are:
- Nuclear membrane
- Nucleoplasm
- Nucleolus
- Chromatin
Q 33 – Which organism is more efficient in its functioning unicellular or multicellular? Why?
Ans. Multicellular organisms are more efficient in their functioning because labour is divided among the cells and have a great capacity to survive than unicellular organisms.
Q 34 – What would happen if animals have a cell wall?
Ans. All parts of the animal would become rigid which will make their movement of limbs and body parts difficult.
Q 35 – Cells consist of many organelles, yet we do not call any of these organelles a structural and functional unit of living organisms. Explain.
Ans. Organelles cannot function outside the cell as an independent unit. They can perform their functions only when they are within the living cells.
Q 36 – Why do plant cells need cell walls?
Ans. As plants cannot move, they need protection against variations in temperature, high wind speed, atmospheric moisture, etc.