Class 12th Biology 2017 Set3 Delhi Board Paper Solution
Question 17
Describe how do ‘flocs’ and ‘activated sludge’ help in sewage treatment.
Answer
Flocks are masses of bacteria associated with fungal filaments to form mesh like structure. It helps in aerobic decomposition as well as filament help in traping particles.
Activiated sludges is used as inoculum to produce flocks during secondary treatment. Process for treating sewage and in industrial waste water using air and a biolgical floc composed of bacteria and protozoa.
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:- What is oogenesis? Give a brief account of oogenesis.
- Q:- Describe the structure of a seminiferous tubule.
- 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:- Define population and community.
- Q:- Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers?
- Q:- What are the major causes of species losses in a geographical region?
- Q:- Differentiate between:
(a) Hypocotyl and epicotyl
(b) Coleoptile and coleorrhiza
(c) Integument and testa
(d) Perisperm and pericarp - Q:- Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?
- Q:- Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in F1 generation for a dihybrid cross?
- Q:- What are sacred groves? What is their role in conservation?
- Q:- Which one of the following has the largest population in a food chain?
(a) Producers
(b) Primary consumers
(c) Secondary consumers
(d) Decomposers - Q:- What is bagging technique? How is it useful in a plant breeding programme?
- Q:- Most living organisms cannot survive at temperature above 45°C°. How are some microbes able to live in habitats with temperatures exceeding 100°C?