Evolution — BIOLOGY STD 12 Science — Question

Himani while watching a TV programme based on life in polar region observed that all animals in polar regions possess larger size. Also, smaller animals are not found in that region. She asked about this surprising fact to her teacher.

1. Why smaller animals (e.g. humming birds) are rarely found in polar regions?
2. What are the adaptations shown by polar animals?
3. What are the chief characteristics of polar region animals?
4. What values are shown by Himani?

Give a genetic explanation for the following cross. When a tall pea plant with round seeds was crossed with a dwarf pea plant with wrinkled seeds then all the individual of F₁-population were tall with round seeds. However selfing among F₁-population led to a 9:3:3:1 phenotypic ratio.

Give the technical terms for the following:

1. Molecular Scissors.
2. Molecular Sieve.
3. Molecular Glue.
4. Autonomous replicating circular DNA.
5. First isolated restriction endonuclease.
6. Extraction of DNA fragments from gel.

Answer the following questions:
State and explain the law of dominance as proposed by Mendel.

Answer the following questions:

Given below is the T.S. of human ovary. Identify the following in the diagram:

1. Corpus luteum.
2. Secondary oocyte.
3. Antrum.
4. Primary follicle.
5. Blood vessels.

With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.

Study the flow chart given below. Name the hormones involved at each stage and explain their role.

Explain the efforts for the conservation of biodiversity at international level.

Describe the disease 'Typhoid' under the following headings :
(i) Name of the pathogen
(ii) Name of the test to confirm the disease
(iii) Mode of infection
(iv) Four main symptoms of the disease
(v) Diagram of the structure of an antibody molecule.

Answer the following questions:
Endosperm development precedes embryo development. Why?