Bachelor of Science (B.Sc.) - Life Science
Term-End Examination

Time: 2 hours
Maximum Marks: 50

Note: Answer Part I and Part II in seperate answer copies.

Answer all questions

PART I

SECTION A

A1. Distinguish between any five of the following pairs: (5)

(a) Monopodial and Sympodial branching

(b) Phylohormones and Phytochrome

(c) Intra-fascicular and intra-fascicular cambium

(d) Exine and intine

(e) Polygonum type and Adoxa type embryo sacs

(f) Homomorphic and Heteromorphic self-incompatibility

(g) Phellem and Phelloderm

SECTION B

B1. Describe the different types of seed appendages and explain their role in dispersal of seed. (5)

OR

Define polyembryony. Discuss the occurrence of polyembryony in Citrus.

B2. Trace the sequence of events from arrival of the pollen grain on the stigma to the discharge of male gametes from the pollen tube. What is double fertilization ?(5)

OR

What is meant by anomalous secondary growth ? Describe the phenomenon with Beta vulgaris root as an example.

PART C

C1. Describe the term senescence. Comment on the role of growth regulators in senescence.

OR

Name the hormones associated with abscission. Describe the anatomical changes associated with leaf abscission.

C2. Describe the Bergmann's method of plant cell culture.

OR

Distinguish between somatic hybridization and haploid production. Describe one method of plant protoplast fusion.

PART II

SECTION A

Answer all questions.

A1. Fill in the blanks.

(a) Thickening of epithelium prior to changes in epithelial sheet is known as ____ . (1)

(b) The spreading of one layer of embryonic cells over another during gastrulation is known as ____ . (1)

A2. Give one example each of complete and incomplete metamorphosis in insects.

A3. Answer in one or two lines :

(a) Why does gastrulation in frog begin on the dorsal side and not at the vegetal pole ? (1)

(b) Which germ layers give rise to central nervous system and digestive system in vertebrates ? (1)

SECTION B

B1. write short notes on any two of the following:

(a) Proto-oncogenes

(b) Morphological changes during metamorphosis in anuran amphibians

(c) Instructive and permissive induction

(d) Primary egg envelopes

(e) Intrinsic growth factors

B2. Define the terms totipotency and pluripotency. Describe an experiment to test the potency of blastula nuclei in frog.

B3. (a) Define congenital defects.

(b) What defects may be produced in the human foetus : if during early stages of pregnancy

(i) mother drinks alcohol.

(ii) mother gets German measlesdue to infection by Rubella virus ?

SECTION C

Answer the following questions in not more than 250 words.

C1. Define regeneration . Is this process universally found in the animal kingdom ? How is it different from embryonic development ? (1 +1 + 3)

OR

List the stages of metamorphosis in anurans. Describe briefly two external and two internal metamorphic changes. (5)

C2. where in the embryo do the primordial germ cells orginate ? Describe their migration to the genital ridge in frog embryo by suitable diagrams. (1 + 4)

OR

How is polyspermy prevented in organisms ? What could be the possible results of polyspermy ? (3 + 2)