Human Health and Disease — BIOLOGY STD 12 Science — Question

(a) Write the features that a biomolecule must fulfill to be able to act as a genetic material.
(b) DNA and RNA are both genetic materials. Which one of the two is more stable and why?
Or
Stability of DNA is higher than that of RNA. How?

Define linkage and linkage group. Discuss the effect of linkage and its importance.###What is linkage? Who coined the term? Write the name of the insect used for this study.

What is ecological pyramid? Write its types and give a diagrammatic representation of the pyramid of biomass in the ocean.

Study the following flow chart. Name the hormones involved at each stage. Explain their functions.

In a pond, we see plants which are free-floating; rooted–submerged; rooted emergent; rooted with floating leaves. Write the type of plants against each of them.

	Plant Name	Type
a.	Hydrilla	____________
b.	Typha	____________
c.	Nymphaea	____________
d.	Lemna	____________
e.	Vallisnaria	____________

Show that Darwin’s natural selection is based on natural observation, with an example for each.

1. Following are the responses of different animals to various abiotic factors. Describe each one with the help of an example.

1. Regulate.
2. Conform.
3. Migrate.
4. Suspend.

2. If 8 individuals in a population of 80 butterflies die in a week, calculate the death rate of population of butterflies during that period.

Explain the role of lactose as inducer in lac Operon.###What is lac operon concept? Describe its mechanism.###In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?###Define the operon and name its Constituent Genes.

Draw only well labelled diagram of 8-nucleate angiospermic embryosac.