What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
The sequential inter- linking of organisms involves the transfer of food in the form of energy from producers by the series of organisms with repeated eating and being eaten is referred to as the food chain. And, these sequential steps in the food chain are referred as different tropic levels.
Example:- Grassland ecosystem food chain and their different tropic levels
Grasses ← Insects ← Frogs ← Snake ← Predatory birds
Producers Herbivores Primary Secondary Tertiary carnivores
carnivores carnivores
Trophic levels are the nutritional levels in which food energy is transferred from one level to another level. In this above example, producers are the green plant (grasses) which is first trophic level; herbivores (insects) are the secondary trophic levels which are the plant eaters also called primary consumers belongs to secondary trophic level; then came primary carnivores (frogs) also called secondary consumers which feeds on primary consumers. And, then secondary carnivores (snake) which are the flesh eaters as like primary carnivores also called tertiary consumers; And then quaternary consumer (predatory birds) level came which are the tertiary carnivores. The maximum step in the food chain is 4 or 5.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Give any two ways in which biodegradable substances would affect the environment.
Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
If all the waste we generate is biodegradable, will this have no impact on the environment?
Why are some substances biodegradable and some non-biodegradable?
Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
How can you help in reducing the problem of waste disposal? Give any two methods.
What is ozone and how does it affect any ecosystem?
What is the role of decomposers in the ecosystem?
What will happen if we kill all the organisms in one trophic level?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Give an example of a metal which
(i) is a liquid at room temperature.
(ii) can be easily cut with a knife.
(iii) is the best conductor of heat.
(iv) is a poor conductor of heat.
State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field.
Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic Table.
(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
(a) A convex lens of focal length 50 cm.
(b) A concave lens of focal length 50 cm.
(c) A convex lens of focal length 5 cm.
(d) A concave lens of focal length 5 cm.
State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire of an electric supply.
Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
List the properties of magnetic field lines.
List two methods of producing magnetic fields.