Class 12th Biology 2017 Set2 Delhi Board Paper Solution
How does the application of cyanobacteria help to improve agricultural output?
Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments. Most of these can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as important biofertiliser. Blue green algae also add organic matter to the soil, thus increasing the fertility. Thus, application of cyanobacteria helps in improving agricultural output.
Popular Questions of Class 12th biology
- Q:- What is spermatogenesis? Briefly describe the process of spermatogenesis.
- Q:- Why is reproduction essential for organisms? Answer
- Q:- Write a short note on
(a) Adaptations of desert plants and animals
(b) Adaptations of plants to water scarcity
(c) Behavioural adaptations in animals
(d) Importance of light to plants
(e) Effect of temperature or water scarcity and the adaptations of animals. - Q:- With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
- Q:- What is DNA fingerprinting? Mention its application.
- Q:- Describe the structure of a seminiferous tubule.
- Q:- What is oogenesis? Give a brief account of oogenesis.
- Q:- What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
- Q:- With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.
- Q:- Explain the Law of Dominance using a monohybrid cross.
Recently Viewed Questions of Class 12th biology
- Q:- Name important defence mechanisms in plants against herbivory.
- Q:- Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
- Q:- Do you think that reproductive health in our country has improved in the past 50 years? If yes, mention some such areas of improvement.
- Q:- Differentiate between gametogenesis from embryogenesis.
- Q:- Define ecological pyramids and describe with examples, pyramids of number and biomass.
- Q:- Suggest some methods to assist infertile couples to have children.
- Q:- Explain why meiosis and gametogenesis are always interlinked?
- Q:-
Fill in the blanks:
(a) Humans reproduce __________. (asexually/sexually)
(b) Humans are__________. (oviparous/viviparous/ovoviviparous)
(c) Fertilization is __________ in humans. (external/internal)
(d) Male and female gametes are __________. (diploid/haploid)
(e) Zygote is __________. (diploid/haploid)
(f) The process of release of the ovum from a mature follicle is called__________.
(g) Ovulation is induced by a hormone called the __________.
(h) The fusion of male and female gametes is called _____________.
(i) Fertilisation takes place in _____________.
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between fetus and uterus is called ____________. - Q:- How do ecologists estimate the total number of species present in the world?
- Q:- Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?