AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions

AP State Board new syllabus 8th Class Biology Guide 1st Lesson Cell Structure and Functions Textbook Exercise Questions and Answers.

AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions

8th Class Biology 1st Lesson Cell Structure and Functions Questions and Answers (Exercise)

Question 1.
Indicate whether the following statements are True (T) or False (F).
a) Unicellular organisms have one-celled body. (T/F)
b) Muscle cells are branched. (T/F)
c) The basic living unit of an organism is an organ. (T/F)
d) Amoeba has irregular shape. (T/F)
Answer:
a) True
b) False
c) False
d) True

AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions

Question 2.
Make a sketch of the human nerve cell. What function do nerve cells perform?
Answer:
AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions 1

  • The nerve cell is also called neuron.
  • It receives and transfers message from brain to body parts and vice versa.
  • It helps in control and coordination of functioning of different body parts.
  • Neuron is the structural and functional unit of nervous system.

Question 3.
Write short notes on the following.
a) Cytoplasm
b) Nucleus of a cell
Answer:
a) Cytoplasm

  • It is the jelly like substance present between the cell membrane and the nucleus
  • Various other components or organelles of cells are present in the cytoplasm.
    Ex : Golgi, mitochondria, ribosomes etc.
  • It also contains basic elements like Carbon (C), Hydrogen (H), Oxygen (O) and Nitrogen (N) in the form of carbohydrates, proteins and lipids:
  • It is present in all types of cells.

b) Nucleus of a cell :

  • It is an important component of the living cell.
  • It is generally spherical and located in the centre of the cell.
  • Nucleus is separated from cytoplasm by a porous and selectively permeable membrane called nuclear membrane.
  • In the middle of the nucleus, a small spherical body is seen. It is called Nucleolus.
  • Nucleus contains thread like structures called chromosomes. These carry genes and help in inheritance.
  • It acts as control centre of all activities of the cell.

AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions

Question 4.
Which part of the cell contains organelles ?
Answer:
Cytoplasm of the cell contains cell organelles.

Question 5.
Make sketches of animal and plant cells. State three differences between them.
AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions 2
Answer:

Plant Cell Animal Cell
1) Cell membrane is covered by cell wall. 1) Cell wall is absent.
2) Plastids are present. 2) Plastids are not present.
3) A large vacuole is present. 3) Vacuoles are not seen (or) much
smaller vacuoles are seen.
4) Centrosomes are absent. 4) Centrosomes are present.

Question 6.
State the difference between eukaryotes and prokaryotes.
Answer:

Eukaryotes Prokaryotes
1) There is a well developed nucleus with nuclear membrane is present.

2) Well developed membrane are bound cell organelles are present.

3) All plant and animal cells are examples for eukaryotes.

1) There is not well developed nucleus is present.

2) Well developed membrane bound cell organelles are absent.

3) Bacteria and blue green algae are examples for prokaryotes.

Question 7.
Where are chromosomes found in a cell ? State their function.
Answer:

  • Chromosomes are found in the nucleus of the cell.
  • Chromosomes carry genes on them and help in transfer the characters from parents to the offspring.
  • These are seen only when the cell divides.

Question 8.
‘Cells are the basic structural units of living organisms’. Explain.
Answer:

  • All living organisms are made up of cells.
  • All the basic life functions of an organism occur in cell.
  • A group of cells to form a tissue to perform a specific function. Different tissue combine to form an organ and different organs together form an organ system which ultimately form an organism.
  • Cells → Tissue → Organ → Organ system → Organism
  • As bricks are put together to construct a building, similarly, the body of a living organism is made up of cells.
  • From this, we can say that cell is the basic structural unit of living organisms.

AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions

Question 9.
Explain why chloroplasts are found only in plant cells ?
Answer:

  • We can observe some coloured bodies in the cytoplasm of the cell of tradescantia or Elodea or Rhoeo leaf.
  • These are called plastids. Green coloured plastids are called chloroplasts.
  • Due to the presence of a pigment called chlorophyll, chloroplasts are green in cólour.
  • Chloroplasts are the sites of photosynthesis. These are also known as “food factories of the cell”.
  • Chloroplasts are present only in plant cells and absent in animal cells.

Question 10.
Complete the crossword with the help of clues given below.
Across:
1) This is necessary for photosynthesis.
3) Term for component present in the cytoplasm.
6) The living substance in the cell.
8) Units of inheritance present on the chromosomes.

Down :
1) Green plastids
2) Formed by collection of tissues.
4) It separates the content of the cell from the surrounding medium.
5) Empty structures in the cytoplasm.
7) A group of cells.
AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions 3
Answer:
AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions 4

AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions

Question 11.
A hen’s egg can be seen easily. Is it a cell or a group of cells ?
Answer:

  • The egg of a hen is a single cell.
  • It is big enough to be seen by the naked eye.

Question 12.
What advantage does amoeba derive by changing shape ?
Answer:

  • Amoeba forms pseudopodia (false feet) which can change it’s shape.
  • Pseudopodia of amoeba are helpful in its locomotion and also in capturing food.

Question 13.
Are the cells in an elephant larger than the cells in a rat?
Answer:

  • The size of the cells has no relation with the size of the body of the animal or plant.
  • It is not necessary that the cells in the elephant be much bigger than those in a rat.
  • The size of the cell is related to its function.
  • For example, nerve cells, both in the elephant and rat are long and branched they perform the same function, that is transferring mesages.

Question 14.
I want to know why plant cells need cell walls ?
Answer:

  • Plant cells have cell wall surrounding the cell membrane, is required by the plants for protection.
  • Plant cells need protection against variations in temperature, high wind speed, atmospheric moisture etc. They are exposed to these variations, because they can not move.
  • Hence plant cells have cell wall for their protection.

Question 15.
In order to compare a plant cell and animal cell. Complete the table.

S.No. Part Plant cell Animal cell
1 Cell membrane Present Present
2 Cell wall Present Absent
3 Nucleus
4 Nuclear membrane
5 Cytoplasm
6 Plastids
7 Vacuole

Answer:

Part Plant cell Animal cell
1 Cell membrane Present Present
2 Cell wall Present Absent
3 Nucleus Present Present
4 Nuclear membrane Present Present
5 Cytoplasm Present Present
6 Plastids Present Absent
7 Vacuole Present Present


Extended Learning – Activities And Projects

Question 1.
Visit a laboratory for senior secondary students in your school or in a neighbouring school. Learn about the functioning of a microscope in the laboratory. Also observe how a slide is observed under the microscope.
Answer:
Student activity.

Question 2.
Talk to the senior biology teacher in your school or a neighbouring school. Find out if there are diseases which are passed on from parents to the offspring. Find out how these are carried and also if these diseases can be treated. For this you can also visit a doctor.
Answer:
1. Haemophilia (blood clotting doesn’t occur) and colourblindness (can’t recognise red and green colours) are the diseases that are passed from parents to the offspring.
2. It is because these disease causing genes are located on sex chromosomes. Hence they are inherited to the offspring.
3. These diseases can be prevented by using genetic engineering methods.

Question 3.
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.
Answer:
1. Scientists developed pest resistant and drought resistant crop varieties by making genetic modifications in their genes (GM). Hence these crops are called Genetically Modified crops (GM crops).
2. Scientists use genetic engineering methods to produce GM crops. By introducing a new trait to the plant which does not occur naturally in the species.
3. As GM crops are friendly to farmers they are eager to grow these crops. But, some environmentalists objected GM crops to grow on many grounds including ecological concerns.
4. GM crops pose no greater risk to human health than conventional crops.
5. But in recent times, agitations against cultivation of GM crops have taken place on environmental concerns.

Question 4.
Find out about’Bt cotton from an agriculture expert. Prepare a short note on its advantages / disadvantages.
Answer:
1. Bt cotton is a genetically modified variety of natural cotton.
2. Bacillus thuringiensis (bacteria) is introduced in cotton by genetic engineering techniques and hence it is called Bt cotton. The aim to produce Bt cotton is to produce pest resistant variety of cotton.

Advantages of Bt cotton :

  • It is resistant to boll weevil larvae, the main predators of cotton crop.
  • Reduce the use of chemical pesticides.
  • Reduce the agricultural costs.
  • Minimises environmental pollution.
  • Matures early when compared to normal cotton crop.

Disadvantages of Bt cotton :

  • Bt cotton seeds are very expensive.
  • Ineffective against sucking pests.
  • People employed in pesticide industries will lose their employment.
  • It can disrupt the natural process of gene flow.
  • The pests might become resistant to the toxins produced by these crops and the crop production might decline.

8th Class Biology 1st Lesson Questions and Answers (Lab Activities)

Activity – 1

How do you observe Amoeba and Paramecium in your school laboratory?
Answer:
AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions 5

1. We can observe amoeba and paramecium with the help of permanent slides under a microscope.
2. We can grow protozoa in our school lab by doing the following steps.

  • Soak hay in pond water to prepare a decoration of hay.
  • After 3 – 4 days, take a drop of water and observe it under compound microscope.
  • We can observe protozoans like Amoeba, Paramecium etc in the slide.

AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions

Activity – 2

How do you observe a cell without any magnifying device ?
Answer:

  • Take a hen’s egg and boil it.
  • Remove the shell. A white material surrounds the yellow part.
  • The white material is albumin which solidifies on boiling.
  • The yellow part is yolk. It is part of the single cell.
  • Like this way, we can observe the single cell without any magnifying device.

Activity – 3

How do you observe the cells In an onion peel in your biological science laboratory?
Answer:
AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions 6

  • Peel an onion and cut a small portion from bulb.
  • Break this piece into two small parts and try to separate them.
  • Take out the translucent membrane which is holding the pieces.
  • Cut the small piece from it and spread it on a slide.
  • Make sure that membrane is not fold.
  • Add 1 – 2 drops of stain like methylene blue solution on the layer.
  • Cover the membrane with coverslip and leave it for about 5 minutes.
  • Observe the slide under microscope.

Activity – 4

Write the procedure to observe human cheek cells in your science laboratory.
Answer:
AP 8th Class Biology 1st Lesson Questions and Answers Cell Structure and Functions 7

  • Take a clean tooth pick or a matchstick with the tip broken.
  • Scrape inside of your cheek without hurting it.
  • Place it on a drop of water on a glass slide.
  • Add a drop of iodine and place a cover slip over it.
  • Alternatively, add 1 – 2 drops of methylene blue solution. Observe it under microscope.
  • We can identify the cell membrane, cytoplasm and nucleus. A cell wall is absent in animal cells.

 

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