Solution :

(i) Rudolf Virchow (1855) He was the first to explain that the cells divide and new cells are formed from the pre-existing cells (omnis cellula-e-cellula). He demonstrated that the cell theory applies to diseased tissue as well as to healthy tissue. He also engaged his research in the fields of archaeology and anthropology.
(ii) Schleiden and Schwann They observed the animal and plant cells. They also proposed the cell theory. This theory explains that all animals and plants are composed of cells, which serve as the units of structure and function.

Solution :

Structure of a Nucleus :

(i) Nuclear membrane - encloses nucleus in the eukaryotes. The nuclear membrane is penetrated by large nuclear pore complexes, which selectively transport molecules into or out of the nucleus.
(ii) Nucleoplasm - It is the protoplasm in the nucleus and contains genetic material (DNA), chromosomes and nucleolus.
• Chromatin is thin thread-like structure made up of DNA and proteins.
• It condenses during cell division to form a thick rod-like structure called chromosome.
• Each chromosome consists of two similar halves called chromatids.
(iii) Nucleolus It is the most important site of RNA synthesis.

Solution :

The body of a multicellular organism contains cell as a basic structural unit.
• The cells are organised to form tissues such as blood, bone, etc.
• The tissues are organised to form organs such as heart, kidney, etc.
• The organs are further organised to form organ systems such as digestive system, reproductive system, respiratory system, etc.
Hence, various organ systems of organism get arranged to form a complete individual, showing division of labour.

Solution :

The features common to both animal and plant cells are:
(i) Organelles like-nucleus, mitochondria, endoplasmic reticulum, plasma membrane, cytoplasm, ribosomes and Golgi apparatus
(ii) Both types of cells undergo cell division.
(iii) Cellular respiration occurs in both type of cells.

Solution :

(i) Odd term–Cytoplasm
Other terms are related with structure of nucleus.
(ii) Odd term–Protoplasm
Other terms are related with plastids of plant cell.
(iii) Odd term–Hydra (a multicellular organism)
Other terms are unicellular organisms.
(iv) Odd term–Mushroom (multicellular)
Other terms are unicellular organisms.

Solution :

(i) Plasma membrane - It acts as a semipermeable membrane and allows only selective substances to pass through it.
(ii) Nucleus - Control centre of the cell. It contains the cells DNA (genetic information) in the form of genes.
(iii) Mitochondria - The main function of mitochondria in aerobic cells is the production of energy by synthesis of ATP.
(iv) Chloroplasts - These are the sites of photosynthesis within plant cells.
(v) Lysosomes - The breakdown of unwanted macromolecules into micro molecules is the main function of these organelles.

Solution :

Solution :

(i) A. Cell membrane B. Nucleus B. Golgi body D. Mitochondrion
(ii) The structure absent in plant cell - Centriole
(iii) The Nucleus - Controls cellular activities.
(iv) It is the powerhouse of a cell and produces energy by respiration.