Organisms and Populations — BIOLOGY STD 12 Science — Question

What is secondary productivity? What is annual net primary productivity of biosphere?

Name the kind of organisms which constitute the pioneer community of xerarch and hydrarch succession, respectively.

As a senior biology student you have been asked to demonstrate to the students of secondary level in your school, the procedure(s) that shall ensure cross-pollination in a hermaphrodite flower. List the different steps that you would suggest and provide reasons for each one of them.

Describe the inter-relationship between productivity, gross primary productivity and net productivity.

Identify A, B, C, D, E and F in the table given below:

S. No.	Component-I	Component-II	Chemical linkage bonding the two components	Product
(i)	A	B	C	Nucleotide
(ii)	Nucleotide	D	E	Nucleotide
(iii)	Nucleotide	Nucleotide	F	Dinucleotide

Using a Punnett Square, workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.

Draw a labelled diagrammatic sectional view of a human seminiferous tubule.
OR

1. Draw a sectional view of seminiferous tubule of a human. Label the following cells in the seminifferous tubule:

1. Cells that divide by mitosis to increase their number
2. Cells that undergo meiosis I
3. Cells that undergo meiosis II
4. Cells that help in the process of spermiogenesis.

2. Mention the role of leydig cell.

The following is the flowchart highlighting the steps in DNA fingerprinting technique. Identify A, B, C, D, E and F.

Can a person with blood group O Rh+ve donate blood to a patient with blood group O Rh-ve? Why?

1. Name the enzyme that catalyses the transcription of hnRNA.
2. Why does the hnRNA need to undergo changes? List the changes hn RNA undergoes and where in the cell such changes take place.