Give scientific reasons.
1. Some of the characters of parents are seen in their offspring.
Ans.
(1) In sexually reproducing organisms, fusion of gametes from male and female parents occurs.
(2) Some of the genes of parents are transmitted to the next generation without any changes. Therefore, some of the characters of parents are seen in their offspring.
2. Peripatus is said to be the connecting link between Annelida and Arthropoda.
Ans.
(1) Peripatus is the connecting link between two different groups – Annelida and Arthropoda.
(2) It shows annelid-like characters such as segmented body, thin cuticle and parapodia-like organs.
(3) It also shows arthropod-like characters such as tracheal respiration and open circulatory system.
Therefore, Peripatus is said to be the connecting link between Annelida and Arthropoda.
3. Vertebrates have slowly originated from invertebrates.
Ans.
(1) The Carbon dating technique used to assess the age of fossils indicated that invertebrates were present on the earth much before the vertebrates.
(2) Fossils of invertebrates are found buried deep as they are very old and belong to the Palaeozoic era.
(3) The Cenozoic era showed presence of mammals and birds. Their fossils were seen in the upper strata of the earth’s crust.
(4) It was also observed that vertebrates are more complexed than invertebrates.
Therefore, it can be said that vertebrates have slowly originated from invertebrates.
4. Duck-billed platypus shows relationship with mammals.
Ans.
(1) The duck-billed platypus is a connecting link between mammals and reptiles.
(2) It shows similarity with mammals due to the presence of mammary glands and hairs.
Therefore, Duck-billed platypus shows relationship with mammals.
5. We feel tired after exercising.
Ans.
(1) While exercising the muscle cells perform anaerobic respiration.
(2) During anaerobic respiration in muscle cells, lactic acid accumulates in the body.
(3) Lactic acid accumulation is a result of the process of fermentation during which glucose is broken down by anaerobic respiration, forming organic acids.
(4) Also, the production of ATP is comparatively less during anaerobic respiration. Therefore, we feel tired after exercising.
6. Oxygen is necessary for complete oxidation of glucose.
Ans.
(1) A molecule of glucose is completely oxidized in aerobic respiration (i.e. in the presence of oxygen) to form CO?, H?0 and energy (38 ATP), via. three steps namely glycolysis, Krebs cycle and electron transfer chain.
(2) However, in anaerobic respiration (i.e. in absence of oxygen), glucose is incompletely oxidized via. glycolysis and fermentation, resulting in the formation of organic acids or alcohols and lesser amount of energy is obtained.
Hence, oxygen is necessary for complete oxidation of glucose.
7. Fibers are one of the important nutrients.
Ans.
(1) Fibers cannot be digested by humans, yet they are essential nutrients.
(2) Fibers are important as they promote movement of materials through the digestive system and thus aid in digestion of foodstuff.
(3) They also help in egestion of undigested substances from the body.
(4) Vegetables, fruits, cereals, etc. are sources of essential nutrients like fibers.
Hence, fibers are one of the important nutrients.
8. Cell division is one of the very important properties of cells and living organisms.
Ans.
(1) Cell division is the property due to which a new organism (unicellular) is formed from an existing one.
(2) In case of multicellular organisms, the growth of the organisms is dependent on cell division.
(3) It is also essential for restoration of emaciated body.
(4) Cell division is an important aspect of wound healing, formation of blood cells, and other such important life processes.
Hence, cell division is one of the important properties of cells and living organisms.
9. Some higher plants, animals and aerobic microorganisms also sometimes perform anaerobic respiration.
Ans.
(1) Respiration is an energy yielding process and takes place by the oxidation of foodstuffs.
(2) Higher plants and animals require oxygen in order to respire aerobically.
(3) However, in conditions where oxygen is depleted, these organisms perform anaerobic respiration to obtain energy.
(4) Glucose is incompletely oxidized and a comparatively lesser amount of energy is obtained through anaerobic respiration.
Therefore, sometimes, higher plants, animals and aerobic microorganisms also perform anaerobic respiration.
10. Krebs cycle is also called a citric acid cycle.
Ans.
(1) Acetyl-CoA (2 carbon compound) enters the mitochondria to combine with oxaloacetic acid (4 carbon compound) and form a six-carbon compound i.e., citric acid.
(2) Since, citric acid is the first stable compound formed, Krebs cycle is also called citric acid cycle.
11. Flower is a structural unit of sexual reproduction in plants.
Ans.
(1) In flowers, androecium is male whorl and its members are called as stamens. Gynoecium is female whorl and its members are called as carpels.
(2) The male reproductive part i.e. anther is responsible for production of male gametes (pollen grains) and female reproductive part i.e. ovary is responsible for production of female gametes (ovules).
(3) Fertilization takes place by the union of male and female gametes present in flowers.
Therefore, flower is a structural unit of sexual reproduction in plants.
12. Older women are more likely to give birth to children with some abnormalities.
Ans.
(1) A female has millions of oocytes at the time of birth and new ova are not formed thereafter.
(2) Menopause occurs at approximately 40-50 years of age and hence fewer numbers of eggs are present with reduced fertility since the oocytes have aged.
(3) Their ability to divide diminishes and they may not be able to complete meiotic division properly.
(4) Fertilization of such oocytes may result in production of genetic abnormalities (like Down syndrome) in offsprings.
Hence, older women are more likely to give birth to children with some abnormalities.
13. Fertilization in plants is called double fertilization.
Ans.
(1) The pollen grain germinates over the stigma and gives rise to pollen tube.
(2) The pollen tube bursts and releases two male gametes in the embryo sac.
(3) One male gamete fuses with the egg cell to form zygote, whereas the second male gamete fuses with two polar nuclei in the embryo sac to form endosperm.
(4) Since, in flowering plants the process of fertilization occurs twice in the same embryo sac, by two male gametes, it is called as double fertilization.
14. There is a menopause when women are 45 – 50 years old.
Ans.
(1) The natural cessation of menstruation that occurs between the age of 45-50 years is known as menopause.
(2) Menopause occurs as the secretion of hormones controlling the functions of the female reproductive system either stops or becomes irregular.
15. The new individual produced by sexual reproduction always has the recombined genes of both the parents.
Ans.
(1) Sexual reproduction involves two parents i.e. male parent and female parent.
(2) The male gamete coming from male parent fuses with female gamete of female parent to form zygote which develops into embryo and then into a new individual.
Thus, the new individual always has the recombined genes of both the parents.
16. Pollution is a very broad concept.
Ans.
(1) We are aware of different kinds of pollution like pollution of air, water, noise, radiation, soil, thermal, light, plastic etc.
(2) All these types of pollution have adverse effects on health of human and other living organisms.
(3) Due to this conservation of environment also has become the need of an hour.
Hence, pollution is a very broad concept.
17. The role of human beings in environmental balance is important.
Ans.
(1) Human life is an integral part of nature and human survival is closely linked with environment.
(2) Due to rapid increase in human population and industrialization, humans have over utilized natural resources; leading to degradation of environment.
(3) The environment influences the life of human beings and also human beings modify their environment as humans are the apex predators in the food chain.
(4) Humans are capable of conserving and improving the quality of nature and thus, can play a major role in maintaining environmental balance. Humans therefore have an important place in the environment.
Hence, the role of human beings in environmental balance is important.
18. The various food chains in the ecosystem maintain the environmental balance.
Ans.
(1) Food chain is a definite sequence of interaction between producers, consumers and decomposers (saprophytes).
(2) Existence of producers, consumers and decomposers is interlinked.
(3) If number of any of these increases or decreases the ecological balance is disturbed.
Therefore, the various food chains in the ecosystem maintain the environmental balance.
19. Without the existence of nature, human existence is almost impossible.
Ans.
(1) Human life is an integral part of nature and human survival is closely linked with environment.
(2) The environment influences the life of human beings and also human beings modify their environment as humans are the apex predators in the food chain.
(3) Humans are capable of conserving and improving the quality of nature. Irrational use of the natural resources leads to their depletion.
(4) Depletion of natural resources can affect human lives also.
Therefore, without the existence of nature, human existence is almost impossible.
20. The schematic of a turbine also varies according to the type of power generation.
Ans.
(1) In a power plant, a turbine is used to rotate the generator which produces the energy.
(2) To drive the turbine, we need an energy source.
(3) The construction of the turbine in a power plant depends on the type of energy source which is being used to rotate the turbine. For example: steam turbine is used in thermal power plant where steam is used to rotate the turbine while wind turbine with large fins is used in electricity generation using wind energy.
Hence, depending on the energy source the construction of turbine is different for different types of power plants.
21. It is essential to control the process of nuclear fission in a nuclear power plant.
Ans.
(1) Large amount of energy is generated in a matter of seconds in a fission reaction. If the fission reaction is not controlled, it can prove fatal.
(2) Uncontrolled fission reaction may lead to the emission of harmful radiations.
(3) It can also lead to the meltdown of the nuclear power plant.
Thus, it is absolutely necessary to control the fission reaction in nuclear power plants.
22. It is possible to produce energy from mW to MW using solar photovoltaic cells.
Ans.
(1) Solar photovoltaic cells which have energy producing capacity of mW, are connected in required series and parallel combinations to form a solar panel.
(2) Many solar panels are connected in series to form a solar string and many solar strings are connected in parallel to form a solar array which has energy producing capacity of MW.
(3) Thus, with the required series and parallel combination of solar photovoltaic cells to form solar panels, solar strings and solar arrays, it is possible to produce energy from mW to MW capacity.
23. Hydropower, solar energy and wind energy are called renewable energy.
Ans.
(1) The sources of energy which are being produced continuously in nature and are inexhaustible, i.e., they are always available for use are called renewable sources of energy.
(2) Hydropower, solar energy, wind energy are produced from energy sources like water, sunlight and wind respectively that are produced continuously in nature and will not get depleted.
Thus, hydropower, solar energy and wind energy are called renewable energy.
24. Energy saving is the need of the hour.
Ans.
(1) Due to high energy consumption, the existing sources of energy are depleting rapidly and will become scarce in the future.
(2) Saving energy will reduce the burning of fossil fuels, thus minimizing air pollution, water pollution and production of harmful gases that lead to environmental hazards such as global warming and acid rain.
Hence, energy saving is the need of the hour.
25. Earthworm is said to be farmer’s friend.
Ans.
(1) Earthworms loosen the soil by burrowing deep into it, thus they help to aerate the soil.
(2) This continuous digging of soil also helps the water to reach the roots quickly.
(3) Earthworms can decompose the organic matter from the soil and convert it into rich manure.
(4) This helps in increasing the fertility of soil, which ultimately increases the crop production.
Thus, earthworm is said to be farmer’s friend.
26. Body temperature of reptiles is not stable.
Ans.
(1) Reptiles are poikilotherms, i.e. cold blooded animals.
(2) Unlike homeothermic animals like mammals and birds, they are unable to regulate their body temperature internally.
(3) Their body temperature depends directly on the external surroundings.
(4) They can control their body temperature only by moving to an environment with a suitable ambient temperature.
Thus, the body temperature of reptiles is not stable.
27. Our body irritates if it comes in contact with a jellyfish.
Ans.
(1) The mouth of jellyfish is surrounded by tentacles.
(2) The tentacles possess cnidoblasts which are used for capturing prey or for defense.
(3) When our body comes in contact with the tentacles of jellyfish, these cnidoblasts penetrate our skin as a defensive action.
(4) Cnidoblast injects the toxin in our body and thus, our body irritates if it comes in contact with jellyfish.
28. Though tortoise lives on land as well as in water, it cannot be included in class -Amphibia.
Ans.
(1) Tortoise creeps on land as it cannot lift its body up.
(2) Unlike amphibians, the skin of tortoise is dry and scaly.
(3) Neck is absent in amphibians but in tortoise, neck is present between the head and trunk.
(4) The digits of tortoise have claws, which are absent in amphibians.
Thus, tortoise cannot be included in class- Amphibia, though it lives on land as well as in water and is included in class Reptilia.
29. Probiotics have got more importance in recent times.
Ans. Probiotics have got more importance in recent times due to the following reasons:
(1) Probiotics are healthy foodstuffs which contain active bacteria such as Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium bifidum, etc.
(2) These microbes form colonies of useful microbes in the alimentary canal and maintain the balance of beneficial intestinal microorganisms that help in digestion, and decrease the population of harmful microbes such as Clostridium.
(3) They also improve resistance and lower the ill effects of harmful substances formed during metabolic activities.
30. Bread and other products made using commercial yeast are nutritious.
Ans. Bread and other products produced using commercial yeast (baker’s yeast) are nutritious because compressed yeast used in bakery industry contains various useful contents like carbohydrates, fats, proteins, various vitamins and minerals.
31. Microbial enzymes are eco-friendly.
Ans.
(1) Corrosion is a common problem in chemical industries. Using anti-corrosive instruments increases the production cost. However, while using microbial enzymes costly anti-corrosive instruments are not required.
(2) Microbial enzymes are active at low temperature, pH and pressure. Thus, they save energy.
(3) Enzymes carry out specific processes due to which unnecessary by-products are not formed. Thus, expenses on purification are minimized.
(4) In microbial enzymatic reactions, elimination and decomposition of waste material is avoided and enzymes can be reused. Thus, microbial enzymes are eco-friendly.
32. A biofuel is an important tool in renewable energy sources.
Ans.
(1) Biofuels are renewable sources of energy.
(2) They are available in solid (dung, crop residue), liquid (vegetable oils, alcohol) and gaseous (gobar gas) forms.
(3) Biofuels are easily available in sufficient amounts.
(4) They are reliable fuels of the future.
33. The landfill pit is lined with plastic sheets.
Ans. Landfill pits are lined with plastic sheets to prevent soil pollution caused by leaching of toxic and harmful substances into the soil.
34. Microorganisms are used to control the effects of sea oil spills.
Ans.
(1) Oil spills of rivers and oceans can be cleaned by bacteria such as Pseudomonas spp. and Alcanivorax borkumensis, that have the ability to destroy pyridines and other chemicals.
(2) These hydrocarbonoclastic bacteria (HCB) decompose hydrocarbons and bring about the reaction of carbon with oxygen to form CO2 and water.
Thus, microorganisms are used to control the effects of sea oil spills.
35. Herbicide tolerant crop plants are beneficial for agriculture.
Ans.
(1) Unwanted weeds adversely affect the growth of crop plants.
(2) Unwarranted use of herbicides to kill these weeds may also affect the crop plants.
(3) For better agricultural outputs, selective destruction of only weeds is essential.
(4) Hence, in order to target only unwanted weeds and protect the crops from ill-effects of herbicides, herbicide tolerant crop plants are beneficial in agriculture.
36. Recently made vaccines are safe.
Ans.
(1) Recently made vaccines produced by biotechnology are comparatively safer than using completely or partially killed pathogens as vaccines.
(2) Vaccines produced using biotechnology contain only pure proteins that are used as antigens to develop immunity and do not actually contain the complete pathogen, hence making them safer than conventional vaccines.
37. Concepts of body donation and organ donation have come forward.
Ans.
(1) In recent times people have a more liberal view behind the concept of organ and body donation and believe that after death our body should be useful to other needful persons so that their miserable life would become comfortable.
(2) Also, awareness about these concepts is increasing in our country and people are voluntarily donating their bodies.
(3) Life of many people can be saved by organ and body donation. Blinds can regain their vision. Life of many people can be rendered comfortable by donation of organs like liver, kidneys, heart, heart valves, skin, etc. Similarly, body can be made available for research in medical studies.
(4) Many government and social organizations are working towards increasing the awareness about body donation.
Hence, the concepts of body donation and organ donation have come forward.
38. Stem cells are extremely important in regenerative therapy.
Ans.
(1) In case of medical conditions like myocardial infarction, diabetes, Alzheimer’s disease, Parkinson’s disease, etc., stem cells are used to replace dead cells.
(2) In conditions like anemia, thalassemia and leukemia, where blood count is affected, stem cells are used to produce new blood cells. This is known as regenerative cell therapy.
(3) Advances in research may make it possible to produce organs like liver or kidney from stem cells to be used for transplantation in case of organ failure.
Hence, stem cells are extremely important in regenerative therapy.
39. Sewage should not be discarded into the river without treatment.
Ans.
(1) Sewage is rich in organic matter.
(2) Releasing such sewage into natural water bodies like rivers would increase its organic content.
(3) The organic matter would get oxidized using the dissolved oxygen in water.
(4) This reduces the levels of dissolved oxygen and adversely affects the aquatic life in the water body.
Hence, sewage should not be discarded into the river without treatment and should be released in rivers only after oxidation by microbial techniques.
40. Genetically modified crops are beneficial to farmers.
Ans.
(1) Genetically Modified crops (GM crops) are developed by altering the DNA of natural crops.
(2) These new varieties possess useful characters that can withstand adverse environmental stresses like frequently changing temperature, famines, changing climate, etc.
(3) GM crops with resistance to insect pests, pathogens and chemical weedicides can also be developed. This enables the farmers to reduce the use of harmful pesticides.
(4) There is an improvement in the nutritive value of crops and a decrease in crop losses due to the use of genetically modified or hybrid seeds.
Hence, genetically modified crops are beneficial to farmers.
41. Some of the organs in the human body are precious.
Ans.
(1) Organs like the eyes, heart, lungs, pancreas, liver, bone, kidney and skin play significant roles in various physiological (metabolic) activities and maintaining a healthy human life. A person will not be able to lead a normal life if these valuable organs are damaged or absent.
(2) These organs can also be donated to save the life of individuals in need.
(3) During the life of an individual, certain organs like kidney, skin, etc. can be donated to people who have lost the function of these organs due to aging, accidents, infections, disorders, etc.
(4) After death (posthumous), organs like liver, heart and eyes can be donated.
Hence, some of the organs in the human body are precious.
42. Nowadays school children have to deal with mental stress.
Ans. Nowadays school children have to face the problem of mental stress due to the following reasons:
(1) Nuclear families and parents staying outdoors due to job.
(2) Bindings on girls and excessive freedom for boys in some families.
(3) Boys enjoy the concession from their domestic duties whereas girls have compulsion for the same on the pretext that they should be used to it.
(4) Adolescent girls have to face the problems like teasing and molestation.
(5) Increased competition in opportunities for education, further employment and business.
43. The importance of outdoor sports is incomparable.
Ans. The importance of outdoor sports is incomparable since it confers the following benefits:
(1) Causes physical exercise
(2) Improves discipline, interaction and tendency of unity
(3) Drives away loneliness
(4) Makes the person more social
44. Alcoholism is always bad.
Ans. Alcoholism is always bad due to the following reasons:
(1) Excessive consumption of alcohol/ liquor leads to decrease in efficiency of nervous system (especially brain) and liver.
(2) Alcoholism reduces the lifespan of the person.
(3) In adolescents, alcohol affects brain development and reduces ability of memorization and learning.
(4) An addictive person cannot think rationally and faces social, menial, familial illness along with physical illness.