Class 8 Science Chapter 8 MCQ

The organisms which are made of single cell are called unicellular organisms. The single cell behaves as a complete organism performing basic functions such as respiration, reproduction, nutrition, movement etc.

A cell is the smallest and basic unit of life which has definite structure and performs a specific function. Most of them cannot be seen with naked eyes because they are microscopic (i.e., very-very small).

Here, all the statements are correct. Hence, your answer will be option [D].

The correct combination of terms with reference to an animal cell is cell membrane, mitochondria, ribosome and chromosome. An animal cell does not have a cell wall, plastic and chloroplast, but these are present in plant cells.

Bacteria Mycoplasma is the smallest cell. The size of this cell is 0.0001 mm or 0.1 micrometre.

Various components of cells are called cell organelles. Tissue is a group of similar cells which work together to perform a particular function. An animal cell is cell membrane, mitochondria, ribosome and chromosome. An animal cell does not have a cell wall, plastic and chloroplast, but these are present in plant cells.

Cytoplasm is the transparent jelly like fluid which fills the cell between nucleus and cell membrane. Most of the chemical reactions which keep the cell alive takes place here. i)Protoplasm is the living substance of the cell. It includes the cytoplasm and nucleus. ii)Chromoplasts are coloured plastids present in plant cell. iii)Chromosomes are thread like structures present in nucleus.

Chromosome and genes are related to inheritance of characters. Chromosomes are present in nucleus. They contain genes, which are unit of inheritance.

The pigment chlorophyll present in the chloroplasts, which is responsible for green colour of leaves. It can absorb solar energy for photosynthesis.

Here, all the statements are correct. Hence, your answer will be option [D].

Nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring.

Red blood cell does not have a nucleus.

Here, all the statements are correct. Hence, your answer will be option [D].

Micrometre is the unit of measurement used for expressing dimension of cell.

Nails and hair are made up of dead cell. They do not have protoplasm and nerve cells, hence one does not feel pain, when they are clipped or cut.

Cell membrane is the common part of every cell. It encloses the protoplasm, protects the cell, gives the cell its shape and control the entry and exit of substances.

Here, all the statements are correct. Hence, your answer will be option [D].

Chromosomes are the thread-like structures present in the nucleus. They contain genes that functions to transfer the characteristics from the parents to the offsprings.

A unicellular organism consists of a single cell that is capable of performing all the functions. The other statements in true form are: i)Cells cannot be seen easily with naked eyes. ii)Insect’s egg is a single cell. iii)The shape and size of a cell are different in multicellular organisms.

Virus is not considered a cell. It is an exception to the cell theory and cannot survive on its own.

A cell wall is the distinguishing feature between a plant cell and animal cell. It is thick wall made up of cellulose around cell membrane that exclusively present only in plant cell.

The cell observed by Paheli is a bacterial cell. It is a prokaryotic cell that has a cell wall (like plants) but no distinct nucleus. A plant cell has a cell wall and a well-defined nucleus, whereas in an animal cell, the former is not present. A nerve cell is an animal cell that is long and branched to function as transmitter between brain and other parts.

Cheek cells are animal cells. So, there will be no plastids. All other cell organelles such as the nucleus, GA, ribosomes, etc., are enclosed in the cell membrane of cell.

The cells having well defined nucleus containing nuclear material, enclosed by a nuclear membrane are called eukaryotic cells. Example cheek cells. Blue green algae are prokaryotic cells that do not have a nuclear membrane.

Mitochondria are the tiny-rod shaped organelles which are found in all the cells. Mitochondria provide energy for all the activities of the cell. This energy is produced by the process of respiration in which food is broken down by oxygen. So, mitochondria use glucose and oxygen to produce energy. And in the other hand, nucleus contains thread like structure called chromosomes. Chromosomes contain genes which are the units of inheritance.