Evolution — BIOLOGY STD 12 Science — Question

(a) Explain the process of DNA replication in prokaryotes.
(b) Name the phase in the cell cycle in which DNA replication takes place in the cell. What if after DNA replication there is no cell division in a cell?

What role does pituitary gonadotropins play during follicular and ovulatory phases of menstrual cycle and also explain the shift in steroidal secretions.

1. Work out a cross upto F, generation between two pure-bred pea plants, one bearing violet flowers and the other white flowers.
2.  

1. Name this type of cross.
2. State the different laws of Mendel that can be derived from such a cross.

Explain the following terms with examples: Co-dominance

Describe the roles of pitutary and ovarian hormones during the menstrural cycle in human female.###Explain the various phases of menstrual cycle. Give a diagrammatic representation of various events during a menstrual cycle.

Explain the components of Ecosystem.###What do you understand by an ecosystem? Describe the structure and components of an ecosystem.

Write the differences in following-
(a) Write the causes of cancer.
(b) Explain Cancer detection
(c) Write the characters of cancer cells
(d) Write the types of cancer

Describe the components of an ecosystem.

The graph given below shows the variation in the levels of ovarian hormones during various phases of menstrual cycle:

Specify the source of the hormone marked in the diagram.

Name the type of cells attacked by AIDS virus in the human body. Also, explain the events in sequence undertaken by virus to increase its progeny.