Which of the following is not correct?
(a) Robert Brown discovered the cell.
(b) Schleiden and Schwann formulated the cell theory.
(c) Virchow explained that cells are formed from pre-existing cells.
(d) A unicellular organism carries out its life activities within a single cell.
(a) Robert Brown did not discover the cell. The cell was discovered by Robert Hook.
Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.
Multicellular organisms have division of labour. Explain.
What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.
Cell is the basic unit of life. Discuss in brief.
What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
Which of the following is correct:
(a) Cells of all living organisms have a nucleus.
(b) Both animal and plant cells have a well defined cell wall.
(c) In prokaryotes, there are no membrane bound organelles.
(d) Cells are formed de novo from abiotic materials.
Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
Describe the structure of the following with the help of labelled diagrams.
(i) Nucleus
(ii) Centrosome
What are nuclear pores? State their function.
How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
Mention the ploidy of the following:
protonemal cell of a moss;
primary endosperm nucleus in dicot,
leaf cell of a moss;
prothallus cell of a fern;
gemma cell in Marchantia;
meristem cell of monocot,
ovum of a liverwort, and
zygote of a fern.