CBSE Board Students Helpline

Management of Natural Resources Our Environment Sources of Energy Magnetic Effects of Electric Current Electricity Human Eye and Colourful World Light – Reflection and Refraction Heredity and Evolution How do Organisms Reproduce? Control and Coordination Life Processes Periodic Classification Carbon and its Compounds Metals and Non-metals Acids, Bases and Salts Chemical Reactions and Equations

1.Why do asexually reproducing organisms shows very little variation and what is cause of this variation?2.Do the survival of variants have equal chances? If not explain the factors on which survival depends.3.How the creation of variation in certain species promotes survival?4.Why did Mendel select pea plant for his experiment?5.What are the seven contrasting character observed by Mendel in pea plant?6.With schematic figure show inheritance of any trait over two generations?7.With schematic figure show independent inheritance o0f two separate traits.8.What experiment confirms that the F2 generation did in fact have a 1:2:1 ratio. Show this giving an example.9.A man with blood group A marries a woman with blood group O and their daughter has blood group O. With schematic figure explain how this could be possible?10.Briefly describe sex determination in human beings.11.How did Mendel’s experiment show that traits might be dominant or recessive?12.Give an example in which adaptation in t...

1.Define environment. What are the two components of environment? 2.What is biogeochemical cycle? Name four nutrients, which are recycled? 3.Differentiate biodegradable and non-biodegradable substances with examples. 4.Define ecosystem and what are the components of ecosystem? 5.Give example of abiotic component of ecosystem. 6.Give two artificial and two natural system of ecosystem. 7.Define trophic level. Write the trophic level of carnivores, herbivores and producers. 8.How are consumers classified? Give example of two organisms of each group. 9.How do microorganisms help in nutrient cycling? 10.Give two functions of ecosystem. 11.Why should not be a food chain more than four steps? 12.Define ten percent law of energy transfer. 13.What percent of light energy do producers capture? 14.If 2000 calories of solar energy falls on earth surface, calculate the amount of energy received at producer, herbivore and carnivore level. 15.Which type of food habit provides more energy - vegetarian...

MANAGEMENT OF NATURAL RESOURCES 1.What do you mean by natural resources? Give examples.2.What are various laws and organisations that protect our environment?3.Name the microorganisms whose presence indicates water contamination?4.Write one way how to measure contamination of water.5.Explain three R’s to save environment.6.What is sustainable development? 7.What is the necessity to manage our resources?8.Why forest is called ‘biodiversity hot spots’?9.Who are the stakeholders of forest?10.Out of the four stakeholders which one is preferred to take care of forest?11.Why do forest development and industrialists are not preferred to forest conservation?12.What is ‘chipko movement’? Why this movement became so popular?13.What are the various reasons of non-availability of water in arid and semi-arid zones of our country?14.What are the advantages of dam?15.Why dam construction is a matter of controversy and criticism?16.Define water harvesting? What are the various ways of water harvesting...

1. What is reflex action? Explain with an example along with the diagram of the stated example. Define reflex arc. A. It is an accurate, unconscious, involuntary and instantaneous response to a stimulus. e.g.: Hand is withdrawn on being picked. The pathway taken by a stimulus to travel from receptor organ to effector organ is known as reflex arc. Schematic pathway: STIMULUS------->RECEPTOR ORGAN-----(sensory neuron)----->SPINAL CORD---(motor neuron)----->EFFECTOR ORGAN------->RESPONSE See text book for diagram. 2. Distinguish between nastic and tropic movement? -----------NASIC--------------------------TROPIC----------- 1. Growth is not involved.--------1. Growth is involved. 2. Movement is not directional.-2. Movement is directional. 3. Stimulus is diffused.------------3. Stimulus is unilateral. 3. How is hormone secretion is regulated by feedback means? A. Feedback system is a regulatory mechanism in which presence of certain level of substance promotes or inhibits its fu...