Our Environment Important Questions Class 10

SHORT ANSWER TYPE QUESTION[II] [3 Marks] – Year 2007

1. (a) What is ‘environmental pollution’?
(b) Distinguish between biodegradable and non-biodegradable pollutants.
(c) Choose the biodegradable pollutants from the list given below:
Sewage, DDT, radioactive waste, agricultural waste. [Delhi]
Answer. (a) Environmental pollution is an undesirable change in the physical, chemical or biological

characteristics of the natural environment, brought about by man’s activities. This pollution may affect the soil, rivers, seas or the atmosphere.


(c) Biodegradable pollutants are sewage and agricultural waste.

VERY SHORT ANSWER TYPE QUESTIONS [1 Mark] – Year 2008

2. How is the increase in demand for energy affecting our environment adversely?
Answer. The increase in demand for energy affects our environment adversely. Due to this increase, pollutants like CO,C02 , S02, etc., are released in to the atmosphere which leads to greenhouse effect.

3. Why is ozone layer getting depleted at the higher levels of the atmosphere? [Delhi (C)]
Answer. Ozone layer is getting depleted at the higher levels of the atmosphere due to effect of chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.

4. Name any two abiotic components of an environment. [Delhi (C)]
Answer. Two abiotic components of an environment are temperature and rainfall.

SHORT ANSWER TYPE QUESTION[II] [3 Marks] – Year 2008

5. Why are bacteria and fungi called decomposers? List any two advantages of decomposers to the environment. [Delhi]
Answer. Bacteria and fungi breakdown the dead remains and waste products of organisms. These micro organisms are called the decomposers as they breakdown the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants.

Two advantages of decomposers to the environment are as follows:

1. Decomposers feed, on the dead bodies of plants and animals. They return the simple components to soil and help in making the steady state of ecosystem by recycling of nutrients. They, therefore, create a balance in the environment.
2. They also act as scavengers or cleansing agents of the atmosphere.

VERY SHORT ANSWER TYPE QUESTIONS [1 Mark] – Year 2009

6. What are the two main components of our environment? [Delhi]
Answer. The two main components of our environment are the biotic or living components and abiotic or non-living components.

7. Why are green plants called ‘producers’? [All India]
Answer. Green plants are called ‘producers’ because they can produce food by photosynthesis in the presence of sunlight.

8. Which disease is caused in human beings due to depletion of ozone layer in the atmosphere? [Foreign]
Answer. Skin cancer is caused in human beings due to the depletion of ozone layer in the atmosphere.

SHORT ANSWER TYPE QUESTIONS [II] [2 Marks] – Year 2009

9. How is ozone formed in the upper atmosphere? Why is the damage of ozone layer a cause of concern to us? State a cause of this damage. [Delhi(C)]
Answer. Ozone is formed in upper atmosphere by the reaction of ultraviolet (UV) radiations on oxygen (02) molecule.

The damage to ozone layer is a cause of concern to us as due to its damage, more ultraviolet rays reach the earth’s surface causing various health hazards.


A cause of this damage is the presence of large amount of chlorofluorocarbons in the atmosphere.

10. State two problems caused by the non- biodegradable waste that we generate in our daily life. [All India (C)]
Answer. Two problems caused by non-biodegradable waste that we generate in our daily life are:

1. It clogs drains.
2. It causes water and soil pollution.

11. What are biodegradable and non- biodegradable substances? Select two biodegradable pollutants from the following: Agricultural waste, glass, plastic, sewage, DDT. [Ail India (C)]
Answer. Biodegradable substances are those substances which are broken down into simpler, harmless substances in nature in due course of time by the biological processes such as micro organisms like certain bacteria.

Non-biodegradable substances are those substances which cannot be broken down into simpler, harmless substances in nature.

Two biodegradable pollutants are agricultural waste and sewage.

SHORT ANSWER TYPE QUESTIONS [I] [2 Marks] – Year 2010

12. Construct an aquatic food chain showing four trophic levels. [All India]
Answer. Food chain in aquatic ecosystem:

13. Explain ‘biological magnification’ with the help of an example. [All India]
Answer. Pesticides used in crops are washed down .into the soil. From soil these are absorbed by plants along with water and minerals and thus, they enter the food chain. While consuming the crops, human beings also consume these pesticides which get accumulated in our bodies. This phenomenon is known as biological magnification.

14. Describe how decomposers facilitate recycling of matter in order to maintain balance in the ecosystem. [Foreign]
Answer. Decomposers are micro organisms that obtain energy from the chemical breakdown of dead organisms of animals or plants. These micro organisms breakdown the complex organic substances of dead organisms into simple inorganic substances that go into the soil and are used up once more by the plants. Decomposers thus, help in recycling of matter.

15. Explain the phenomenon of “biological magnification” How does it affect organisms belonging to different trophic levels particularly the tertiary consumers? [Delhi]
Answer. The process in which harmful chemicals enter a food chain and get accumulated progressively at each trophic level is called biological magnification.

Harmful and toxic chemicals enter our bodies when they are added to soil and water. Use of pesticides to protect the food crops from diseases and pests and chemical wastes of factories are dumped in open or disposed off into rivers. These chemicals are washed down into the soil and ultimately to water table or get absorbed or taken up from the soil by the plants along with water and minerals and in this way harmful chemicals enter the food chain. The quantity of these harmful chemicals increase with increase in trophic level of the food chain because these substances are not degradable. Man is at the top of the food chain, so concentration is maximum in human beings.

Thus, accumulation of DDT has been maximum in man as DDT is used to destroy pests. DDT is accumulated in the following way in this food chain:

This is the reason why our food grains such as wheat and rice, vegetables and fruits and even meat contain varying amounts of pesticides residues. So, the highest trophic level at the extreme right of food chain has the maximum concentration of harmful chemicals in a food chain.

16. “Damage to the ozone layer is a cause for concern.” Justify this statement. Suggest any two steps to limit this damage. ‘ [Delhi]
Answer. Ozone layer prevents the harmful ultraviolet radiation to enter the atmosphere and reach the earth’s surface. Depletion of ozone layer has become a cause for concern because it can cause serious effects on human body and other organisms of the environment like fatal diseases such as skin cancer, changes in genetic material DNA, eye damage, etc.

Two steps to limit this damage are as follows:

1. Judicious use of aerosol spray propellants such as fluorocarbon and chlorofluorocarbons which cause depletion or hole in ozone layer.
2.  Control over large scale nuclear explosions and limited use of supersonic planes.

VERY SHORT ANSWER TYPE QUESTIONS [1 Mark] – Year 2011

17. What will happen if we kill all the organisms in one trophic level? [Delhi]
Answer. If we kill all the organisms in one trophic level, the following effects will take place:

1. The population of organisms in previous trophi’c level will increase.
2. The organisms in next trophic level will not be able to get the food, so they will migrate to some other ecosystem or die.
3. It will cause an ecological imbalance in the food chain.

18. Why did United Nations act to control the production of chlorofluorocarbons (CFCs) used in refrigerators? [Delhi]
Answer. CFCs deplete the ozone layer around the earth, hence their production is controlled by United Nations.

19. Which compounds are responsible for the depletion of ozone layer? [Delhi]
Answer. The compounds responsible for the depletion of ozone layer are chlorofluorocarbons (CFCs).

20. Define ‘trophic level’. [Delhi]
Answer. Trophic level is the position that an organism occupies in a food chain, where transfer of food or energy takes place.

21. What are the various steps in a food chain called? [Delhi]
Answer. The various steps in a food chain are called trophic levels.

22. What is the important function of presence of ozone in earth’s atmosphere? [Delhi]
Answer. The important function of presence of ozone in earth’s atmosphere is that it shields the surface of the earth from ultraviolet (UV) radiations of the sun.

23. Give an example to illustrate that indiscriminate use of pesticides may result-in the degradation of the environment. [All India]
Answer. The pesticides used in crop field are washed down into the water bodies. From water bodies, these are absorbed by aquatic plants and animals of a food chain and thereby degrades the environment.

24. Why is it necessary to conserve our environment? [All India]
Answer. It is necessary to conserve our environment to prevent depletion of natural resources and environmental damage, thereby sustaining life.

25. What is meant by a biodegradable waste? [All India]
Answer. Biodegradable wastes are those substances which are broken down into simpler, harmless substances in nature in due course of time by the biological processes such as action of micro organisms like certain bacteria.
Examples: Urine and faecal matter, sewage, agricultural residue, paper, wood, cloth and cattle dung.

26. What is the role of decomposers in the ecosystem? [Foreign]
Answer. Role of decomposers in the environment:

1. They return the nutrients to the nutrient pool.
2. They help in completing the different bio-geochemical cycles, thus they maintain the balance in the ecosystem.

27. What step is being taken to limit the damage to the ozone layer? [Foreign]
Answer.

1. Judicious use of aerosol spray propellants such as fluorocarbon and chlorofluorocarbons which cause depletion or hole in ozone layer.
2. Control over large scale nuclear explosions and limited use of supersonic planes.

28. Why are some substances non- biodegradable? [Foreign]
Answer. Some substances are non-biodegradable because they cannot be broken down into simpler harmless substances in nature.

29. Which class of chemicals is linked to the decrease in the amount of ozone in the upper atmosphere of the earth? [Delhi]
Answer. The chemical compound Chlorofluorocarbon is responsible for decrease of ozone in the upper atmosphere of the earth.

30. Name two decomposers operating in our ecosystem. [All India 2011; Delhi]
Answer. Bacteria and fungi.

31. Select two non-biodegradable substances from the following waste generated in a kitchen: spoilt food, paper bags, milk bags, vegetable peels, tin cans, used tea leaves. [Delhi]
Answer. Milk bags and tin cans.

32. What happens when higher energy ultraviolet radiations act on the oxygen at the higher level of the atmosphere? [All India]
Answer. When high energy ultraviolet radiations act on oxygen, ozone is produced:

33. In a food chain, 10,000 joules of energy is available to the producer. How much energy will be available to the secondary consumer to transfer it to the tertiary consumer? [All India ]
Answer. 10 J will be available to the secondary consumer to transfer to the tertiary consumer.

34. Write the name and formula of a molecule made up of three atoms of oxygen. [All India]
Answer. Ozone and its chemical formula is O3.

35. List two man-made ecosystems. [All India]
Answer. Garden and Pond are man-made ecosystems.

36. Consider the following food chain which occurs in a forest: Grass -> Deer -> Lion
If 10000 J of solar energy is available to the grass, how much energy would be available to the deer to transfer it to the lion? [Foreign]
Answer. 10 J energy would be available to deer to transfer to lion.

37. Which of the following belong to the first trophic level of a food chain? Grass, Grasshopper, Plants, Rat, Tiger [Foreign]
Answer. Grass and plants belong to the 1st trophic level of a food chain.

38. Name the phenomenon in which non-biodegradable chemicals get accumulated progressively at each trophic level of a food chain. [Foreign]
Answer. Biological magnification.

Other Important Questions 

1.Why is there a need to b an the use of poly then e bags?

Ans.Polythene bags are non- biodegradable, the y are not decomposed by micro- organisms hence, cause land pollution. 
2.What are the two functions of ecosystem?

Ans.Interactions of any ecosystem refers to it s functions these interactions are- 

(A) Biogeochemical cycles- The cyclic transfers between the living and non- living components. 

(B) Flow of energy- in a food chain, through various st eps of eating and being eaten food energy flow from one tropic level t o another. 


3.What percentage of solar energy is trapped and utilized by plants? 

Ans.Plants utilized only 1% of total sun’s ener gy, which is utilized by plants in the process of photosynthesis. 
4.Energy transfer is said to be unidirectional wh e r e as biochemical transfer is said be cyclic. Why? 

Ans.Energy flow is unidirectional because as it transfers from one trophic level to next trophic level, it reduces only 10% is available at Successive level from previous level. Nutrient flow is cyclic because nutrients re turned back into nutrient pool from the dead bodies of plants and animals by the d ecomposition of micro- organisms from nutrient pool. They are utilized aga in by plants. 
5.Give difference between produc es and consumers. 

Ans.

6.There are no predators for tiger or lion. Why? 

Ans. Lions and tigers are at the highest trophic level. They are largest animals which feed upon the secondary carnivores like wolves etc. they are not killed and eaten by other animals. 
7.What are the measures to protect ozone depletion?

Ans..Measure to protect ozone layer- 

(A) Concern over increasing global ozone depletion led to international restrictions in the use and manufacture of CFCS and halons. 

(B) International concern over the seriousness of the problems associated with ozone layer depletion led to the adoption of Vienna convention for the protection of the ozone layers in 1985.

(C) Promotion of an international treaty know

Our Environment for class 10 sec_2

Introduction

→ Everything that surrounds us is environment. It includes both living (biotic) and non-living (abiotic) components.

→ Interaction between these biotic and abiotic components form an ecosystem.

→ In an ecosystem living components depend on each other for their food which give rise to food chains and food webs in nature.

→ Human activities lead to environmental problems such as depletion of ozone layer and production of huge amount of garbage.

Ecosystem

→ All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem. E.g., forest, pond etc.

Types of ecosystem

It is of two types

(i) Natural ecosystem: The ecosystem which exist in nature on its own.

Example: forest, lake, ocean.

(ii) Artifical ecosystem: Man-made ecosystems are called artificial ecosystem. 

Example: crop field, aquarium, garden.

(i) Abiotic Components: All the non-living components such as air, water, land, light, temperature etc. form the abiotic components.

(ii) Biotic Components: All the living components such as plants, animals, bacteria, fungi etc. form the biotic components.

• On the basis of nutrition biotic components are further divided into:

→ Producers: All green plants and blue-green algae can produce their own food using abiotic components (photosynthesis), hence called producers.

→ Consumers: Include all animals which depend on producers directly or indirectly for their food.

Division of Consumers

(i) Herbivores: Plant eaters. Example:  goat, deer.

(ii) Carnivores: Flash eaters. Example: tiger, crocodile.

(iii) Omnivores: Eats both plants and animals. Example: human.

(iv) Parasites: Live on the body of host and take food from it. Example: lice, cascuta.

Decomposers: Include organisms which decompose the dead plants and animals. Example: bacteria, fungi. These help in the replenishment of natural resources.

Food Chain

→ Food chain is a series of organisms in which one organism eats another organism as food. For example:

• Grass → Deer → Lion

→ In a food chain various steps where transfer of energy takes place is called a trophic level.

Flow of energy between trophic levels

→ Flow of energy in a food chain is unidirectional.

→ Green plants capture 1% of sunlight and convert it into food energy.

→ 10 percent law : Only 10% of energy is transferred to the next trophic level. The remaining 90% energy is used in life processes (digestion, growth, reproduction etc.) by present trophic level.

→ Due to this gradual decrease in energy, food chains contain 3-4 trophic levels.

Trophic levels

• Decrease in energy

1 kJ ↣ 10 kJ ↣ 100 kJ ↣ 1000 kJ

• Biological magnification: The concentration of harmful chemicals increases with every next trophic level in a food chain. This is called biological magnification.

→ Maximum concentration of such chemicals get accumulated in human bodies as human occupy the top level in any food chain.

Food web

→ In nature large numbers of food chains are interconnected forming a food web.

• Environmental problems: Changes in the environment affect us and our activities change the environment around us. Human activities leads to pollution, deforestation etc.

Ozone layer

→ Ozone layer is a protective blanket around the earth which absorbs most of the harmful UV (ultraviolet) radiations of the sunlight, thus protecting living beings from many health hazards such as skin cancer, cataract, destruction of plants etc.

→ Ozone (O₃) layer is present at higher levels of atmosphere (i.e. stratosphere). It is a deadly poison at ground level.

Formation of ozone molecule

(i) The high energy UV radiations break down the O₂ molecules into free oxygen (O) atoms.

O →(UV)  O + O (atoms)

(ii) These oxygen atoms then combine with oxygen (O₂) molecule to form the ozone molecule.

O₂ + O → O₃ (ozone)

Depletion of ozone layer

→ The decrease in the thickness of ozone layer over Antarctica was first observed in 1985 and was termed as ozone hole.

→ This decrease was linked to excessive use of synthetic chemicals like chlorofluorocarbons (CFCs) which are used in refrigerators, ACs, fire-extinguishers, aerosols sprays etc.

→ United Nations Environment Programme (UNEP) succeeded in forging an agreement to stop CFC production at 1986 levels (KYOTO PROTOCOL) by all countries.

Garbage disposal

→ Improvements in lifestyle have resulted in accumulation of large amounts of waste materials.

Types of materials in Garbage

(i) Biodegradable: Substances which can be decomposed by the action of micro-organisms are called biodegradable wastes.

Example:  fruit and vegetable peels, cotton, jute, dung, paper, etc.

(ii) Non-biodegradable wastes:Substances which cannot be decomposed by the action of micro-organisms are called non-biodegradable wastes.

Example: plastic, polythenes, metals, synthetic fibres, radioactive wastes, pesticides etc.

→ Micro-organisms release enzymes which decompose the materials but these enzymes are specific in their action that’s why enzymes cannot decompose all the materials.

Methods of waste disposal

(i) Biogas plant: Biodegradable waste can be used in biogas plant to produce biogas and manure.

(ii) Sewage treatment plant: The drain water can be cleaned in sewage treatment plant before adding it to rivers.

(iii) Land fillings: The wastes are buried in low lying areas and are compacted by rolling with bulldozers.

(iv) Composting: Organic wastes are filled in a compost pit and covered with a layer of soil, after about three months garbage changes to manure.

(v) Recycling: Non-biodegradable wastes are recycled to make new items.

(vi) Reuse: It is a conventional technique to use an item again. Example: newspaper for making envelops.

Our Environment sec_1

1. Environment : The physical, chemical and ‘ biological conditions of the region in which an organism lives is called its Environment. It includes air, light, soil, temperature, water and the presence or absence of other organisms, i.e., the conditions for development or growth.
Environment has three main components, viz :
(a) Physical surroundings [soil, air and water bodies]
(b) Living organisms [plants, animals, decomposers (bacteria and fungi)]
(c) Meteorological factors (or climatic factors) . [sunlight, temperature, rainfall, humidity, pressure and wind speed].

2. Physical environment: It is also called as abiotic or non-living environment. It includes :

1. Soil, water bodies and air on the surface of the earth.
2. Meteorological factors.

Physical environment is essential for :

(a) Supply of nutrient elements to the living beings.

(b) Providing space to the organisms for living.

(c) Controlling weather of a place.

3. Biotic (or biological) environment : It includes :

1. Plants.
2. Animals (including human beings).
3. Decomposers (bacteria and.fungi).

Other important constituent of biotic environment includes : Kites and vultures as they feed on dead organisms and act as scavengers (cleansing agents) of the environment.

4. Ecosystem : A community of organisms, interacting with each other, plus the environment in which they

live and with which they also interact. The examples of ecosystem are : a pond ; a desert; a forest; a lake ; a river ; a mountain ; the sea.

All the above ecosystems are made-up of two main components.

5. Autotrophs (Producers) and Heterotrophs (consumers):

6. Food chain: The sequence of living organisms in a . community in which one organism.e^ts other and is

itself eaten by another organism to transfer energy is called a food chain. It is also defined as, “chain of organisms, existing in any natural community, through which energy is transferred”.

7. Ozone layer : Ozone (O3) is a molecule formed by three atoms of oxygen unlike oxygen which is required for respiration by aerobic forms, ozone is a deadly poison. However, at the higher levels of the atmosphere,

ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings.

Ozone at the higher levels of the atmosphere is a product of UV radiation, acting on oxygen (O2) molecule. The higher energy UV radiations split apart some molecular

oxygen (02) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone as shown:

Depletion of ozone layer: Ozone layer gets depleted – due to the use of chemicals called aerosol, spray propellants like chlorofluorocarbons. Depletion of ‘ ozone layer would cause skin cancer in men and animals and severe damage to the plants.

8. Biological magnification : It means accumulation of non-biodegradable chemicals (like pesticides) in the living organisms (like plants, animals, including man) in a food chain. “The increase in concentration of harmful chemicals in the body of living organisms at each trophic level of a food chain is called biological magnification”.

9. Biodegradable wastes and Non-biodegradable wastes:

10. A generalised food chain:

11. Food web: A food web is a network of food chains which establish a network of relationships between various species. Food web showing 8 interlinked food chains.

13. The flow of energy between various components of the environment:

1. Green plants capture about 1 % of the energy and convert it into food energy.
2. About f % of the food eaten is turned into the body of an organism and made available for the next level of consumers.
3. About 10% of organic matter is present at each step and reaches the next level of consumers.
4. Since so little energy is available for the next level of consumers, food chains generally consist of only three or four steps. The loss of energy at each step is so great that very little usable energy remains after four trophic levels.
5. There are generally a greater number of individuals at the lower trophic levels of an ecosystem, the greatest number is of the producers.

PHOTOSYNTHESIS FOR CLASS 11

Question of plant reproduction

HAPPY DIWALI TO ALL LEARNERS

Board Based Questions from heredity and Evolution

Q. Why did Mendel chosen pea plant for his experiments?

Answer:   Mendel chose pea plant for his experiments because it is:

(a) Easy to grow (b) Short lifespan (c) Easily distinguishable characters (d) Larger size of flower  (e) Self-pollinated.


Q. What is heredity?

Ans:- Heredity refers to the transmission of characters or traits from the parents to their offspring.

Q. What do you understand by evolution?

Ans:-Evolution is the sequence of gradual changes which takes place in the primitive organisms over million of years in which new species are produced.

Q. What is  a gene?

Ans:- Gene is a small segment of DNA on a chromosome occupying specific position in which is a hereditary determinant or unit of a biological function.

Q. With the help of suitable examples, explain why certain traits cannot be passed on to the next generation. What are such traits called? 

Solution:      The traits which are acquired during the lifetime of a person are called acquired traits. These traits involve changes in non reproductive cells (somatic cells) which are not transferred to germ cells. So, these traits cannot be passed on to the next generation. For example: Learning skills like swimming, dancing, cooking, body building, etc are acquired traits and cannot be passed on to the next generation.

Q. "A trait may be inherited, but may not be expressed." Justify this statement with the help of a suitable example.

Ans: When a tall plant was crossed with a short plant, the first (F1) generation plants were all tall. But when the F1 generation plants were crossed, the second (F2) generation plants were not all tall: there were both tall and short plants. 

 This shows that the F1 plants had inherited their trait from the short plants but did not express it in the presence of the tallness, and had transferred it to the next generation.

Q. 'It is a matter of chance whether a couple will give birth to a male child or a female child." Justify this statement with the help of a flow chart showing the fusion of sex chromosomes.

 Ans: Sex is determined at the time of fertilization and the two sexes are produced in approximately equal numbers. A human male has XY sex-chromosomes and produces two types of sperms (heterogametic). Either with X-chromosome or with Y-chromosome.

A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with X-chromosomes.

Parents Male                                   Female

Gametes         X Y                                X

Progeny          XX                                XY

                     Female (50%)           Male (50%)
Q.What are homologous organs? How do they provide evidence in support of evolution?

Ans:- Homologous organs are those organs which have the same basic structure and developmental origin but have different functions and appearance.

Homologous organs support evolution:

(i) The similarities of structure and origin of organs indicate that all vertebrates had common ancestors. For example, the forelimbs of humans, whale and bat show structural similarities but functional dissimilarities. Forelimbs in humans used for grasping or holding the things, in whale for swimming and in bat for flying.
(ii) All the organs and systems of the vertebrates show fundamental similarities i.e. homology, which indicate towards common ancestry. Thus, homologous point that organic evolution has taken place.  

Q. What is a retrovirus?

Ans:- A virus having RNA (Ribonucleic acid) as genetic (heredity) material is called Retrovirus. For example, Human immunodeficiency virus (HIV) is a retrovirus.

Q. Who provided the evidence of DNA as a genetic material? Write the names of components of DNA?

Ans:- Griffith, Avery , McLeod and McCarty established that DNA is the genetic material.
Components of DNA: A DNA molecule consists of two polynucleotide chains. Each nucleotide consists of (a) nitrogenous base (Adenine/guanine/Thymine or Cytosine) ,a pentose sugar(deoxyribose) and a phosphate group.

Q.How many types of nitrogenous bases are present in DNA?Name them.

6
Ans:-In DNA two types of nitrogenous bases are present. These are 
(i)PURINES which are adenine and guanine (ii)PYRIMIDINES which are Thymine and cytosine.


Q.How do embryological studies provide evidence for evolution?

Ans:- The similarities in embryonic development reinforce the idea of evolution from common ancestors. The sequence of embryonic development in different vertebrates shows striking similarities. Notochord and gill clefts appear in the embryos of all vertebrates.

Q.Define evolution. And Describe the contribution of Lamarck?

Ans:- Evolution is the sequence of gradual changes which takes place in the primitive organisms over millions of years in which new species are produced.

Contribution of Lamarck:
(i) Lamarck proposed a theory called “The Theory of inheritance of Acquired Characters” to explain the origin and evolution of species.
(ii) The theory was explained in his book ‘Philosophic Zoologique.

Q. What are transgenic organisms? Which property of DNA is used as a tool in genetic engineering?

Ans:-The organisms that contain a segment of foreign DNA are known as transgenic organisms.The complimentary property of the nucleotides of DNA.is the most powerful tool in genetic engineering.

Q.Name the two homologous structures in vertebrates. Why are they so called? How do such organs help in understanding an evolutionary relationship?

Ans:  Limbs of birds, reptiles and humans are all the examples of homologous structures in the vertebrates.  They are called so as the basic structure of the limbs is similar. Though it has been modified to perform different functions in various vertebrates.

These are organs which are inherited from a common ancestor. Such a homologous characteristic helps to identify an evolutionary relationship between apparently different species.

Q. What are the different ways in which individuals with a particular trait may increase in a population? 

Ans : The different ways in which individuals with a particular trait may increase in a population, are :

Genetic drift ; Geographical isolation ; Natural selection and Artificial selection

Q.  Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics? 

Ans : If they all die out became extinct, tiger gene will be lost forever and the coming generation will not be able to see tiger at all.

Q. Will geographical isolation be a major factor in the speciation of a self-pollination plant species? Why or why not?

Ans: No, In asexually reproducing organisms pass on the parent DNA to offspring that leaves no chance of speciation

Q. What is the evolutionary significance of the fossil archaeopteryx?

Ans: Archaeopteryx serves as a connecting link between birds and reptiles. It is the fossil evidence to show that birds have evolved from reptiles.

Q. Give the evidence that bird have been evolved from reptile?

Ans: They both lay eggs, have scales on feet and soft anatomy such as musculature, brain, heart.  

Q. What are vestigial organs? Name any two vestigial organs in man and name organ which is vestigial in man but not in birds.
Ans: Organs that are well developed and functional in many organisms and are very much reduced and functionless in other organisms is called vestigial organs. Nictitating membrane in the eye and vermiform appendix attached to the intestine are two such examples of vestigial organs in man.
Nictitating membrane provides protection of eyes in birds, but in humans it remains as a small fold of skin.

Q.Variation is useful for the survival of species overtime but the variants have unequal chances of survival. Explain the statement.

Ans: If organisms are suited to a particular environment there is chances of survival but  drastic changes in environment could wipe out that population
(i) If some variations are there, few individuals might survive  
(ii) Depending on whether the variations are useful to the change in the environment some variants survive whereas others do not

Q. a) Why do we see different variety of organisms around us?  b) In which type of reproduction   
(i) Off springs are identical? (ii) Exact similar offspring‘s are not produced?    

Ans: (a) Due to inaccuracies in DNA copying (i) asexual (ii)sexual reproduction

Q. How do species of two isolated sub populations become two different species?

Ans: Together, the processes of genetic drift and natural selection will result in these two isolated sub-populations and thus species of two isolated sub populations become two different species

Q. How does sexual reproduction leads to similarities as well as variations ? 

Ans: Similarities and variations are dependent on the type of allele combination an offspring will get from their parents. If a child get dominant alleles from  father then he will look quite similar to his  father and quit different from his mother. If he got a combination of dominant alleles from both the parents then he will be quite different from both the parents.  

Q.All dead organisms do not leave their fossil records, but in some cases their fossils are formed. How do these fossils records form a direct evidence of past happenings?

Ans:  There are two components to this estimation. One is relative. If we dig into the earth and start finding fossils, it is reasonable to suppose that the fossils we find closer to the surface are more recent than the fossils we find in deeper layers. The second way of dating fossils is by detecting the ratios of different isotopes of the same element in the fossil material.

Q. Evolution is a process in which simple life forms change into complex life forms by gradual changes. But, there is a difference between chemical and organic evolution. Differentiate by giving three points.

Ans: The formation of organic molecules from inorganic molecules is known as chemical evolution. Around four billion years ago, earth’s atmosphere consisted of chemicals such as water vapour, methane, ammonia, hydrogen,  Sunlight, heat from volcanoes and lightning caused these molecules to combine in the shallow seas and produce various organic molecules such as sugars. Slowly, these organic molecules combined to form big molecules which include proteins and simple RNA and DNA molecules.
The enzymes, proteins, RNA and DNA once formed constituted a self-replicating system enclosed in a selectively
Permeable, protective lipid sphere which further evolved into membrane bound proto cells and finally into living
Cells. This is known as organic evolution. It includes the changes from the simplest unicellular forms of life to the most complex multicellular forms.

Q. There are a number of ways by which the genes enter a population. Explain briefly the three ways
Ans: Gene flow refers to the transfer of alleles from one population to another as a result of interbreeding between members of two populations.
Mutation: are the sudden changes that take place in the DNA sequence of an organism.
Migration: Migration will change gene frequencies by bringing in more copies of an allele already in the population or by bringing in a new allele that has arisen by mutation.  

Q. why more complex organisms cannot give rise to new individuals through regeneration? 
Ans:   Complex organisms have highly differentiated tissues and organs. In this case regeneration of complex individual organism is difficult from a small piece. 

Q.Why are the small number of surviving tigers a cause of worry from the point of view of genetics?
Ans: Decrease in population; decreases the chances of recombination and variation which impacts the gene pool. As a result, there is a loss of genes. Thus they become extinctQ: shibu's father is a wrestler and has a robust body. His son was thin

(a) Is it true that a wrestles son should also have heavy muscles

(b) What type of character is it - acquired or inherited?

(c) If you are shibu's friend how will you convinced him that he is normal

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Answer: (a) It is not true that wrestlers son also have heavy muscles.

(b) Having heavy muscles is an acquired trait. Heavy muscles can be made by regular exercising.

(c) As Shibu's friend can convince him by telling him that traits like heavy muscles are not inherited but are acquired in the lifetime. So he can start exercising on a regular basis to be like his father. If he is not as strong as his father, there is also a possibility that he may have more traits from her mother .