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Answer:
1. Internal fertilization: Internal fertilization takes place when sperm is introduced into the female body. Fertilization of eggs takes place inside her body. Internal fertilization is considered the more efficient method. It is used by most land animals.
External fertilization: External fertilization occurs when a female deposits eggs outside her body and the male releases sperm onto them. External fertilization usually requires a watery environment and is used by most fish and amphibians.
2. The Adam's apple, or laryngeal prominence, is a feature of the human neck, and is the lump or protrusion formed by the angle of the thyroid cartilage surrounding the larynx seen especially in males.
3. Neurons are nerve cells, or cells found in the nervous system. These are specialized cells designed to stimulate other cells in the body in order to communicate. Neurons are excitable, which means they function by using electrical stimulation.
4. Effects of deforestation on wild animals:
One of the most important effect of deforestation in wild animals is the Loss of species. 70% percent of the world's plants and animals live in forests and are losing their habitats to deforestation, according to National Geographic. Loss of habitat can lead to species extinction.
5. No rusting cannot be called as a combustion process.
Whereas rusting is a redox reaction between a metal and oxygen in the presence of moisture. Combustion produces energy in the form of heat. No energy is obtained in a rusting process.
6. The advantages of using compressed natural gas (CNG) and liquefied petroleum gas (LPG) as fuels are:
- They give a lot of heat energy when burnt.
- They can be transported easily through pipelines.
- They are clean fuels and do not give smoke when burnt.
7. Answer: Nylon fibres are very strong. It is used for making ropes, used for climbing rocks and for making parachutes. Their usage shows that nylon fibres have high tensile strength.
8. Microorganisms and its uses:
- Production of dairy products
- Bread Baking
- Alcoholic Drinks
- Organic acids
- Enzymes
- Steroid production
- Help in sewage treatment
- Used as insecticides
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Answer:
ii) Manure is decomposed organic matters. Fertilizer is man made and contains harmful chemicals.
Manure contains nitrogen, one of the most beneficial substances for soil. Fertilizer may or may not contain nitrogen.
Manure can be used as fertilizer. A fertilizer may not act as a manure but as a pesticide.
iii) Petroleum is formed by dead organic matters underground which turned into liquid over millions of years.
iv) a. Copper is a less reactive metal and cannot displace the more reactive zinc.
b. Aluminum foil is used to wrap food because it protects the food from light, bacteria, etc.
c. Thermosetting plastics are bad conductors of heat and hence used to cover handles of saucepans to prevent our hands from getting burnt.
v) Sex hormones like oestrogen or testosterone are steroid hormones which are naturally produced in the body. These hormones help the growth of the reproductive organs and reproduction.
vi) Asexual reproduction means the reproduction without the combination of two different organisms.
Examples: (1) By fragmentation, when parts of the body break off from the parent body.
(2) By Budding, when a new adult is formed on the parent body.
vii) By planting more trees, by preventing others from cutting down trees. By spreading awareness on environmental conservation and preservation. By reducing all forms of pollution of land, air and water.
viii) Weeds are the fast growing but unwanted plants which prevent healthy growth of garden plantation and field crops.
Weeds can be controlled by
(1) Mechanical method which involves the use of farm equipment.
(2) Biological method which involves the use of natural enemies of weed.
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