Reproduction in Organisms Essay Sample
1. Reproduction in Organisms
Biology in kernel is the narrative of life on Earth. While single beings die without fail. species continue to populate through 1000000s of old ages unless threatened by natural or anthropogenetic extinction. Reproduction becomes a critical procedure without which species can non last for long. Each single leaves its offspring by nonsexual or sexual agencies. Sexual manner of reproduction enables creative activity of new discrepancies. so that survival advantage is enhanced. This unit examines the general rules underlying generative procedures in life beings and so explains the inside informations of this procedure in blooming workss and worlds as easy to associate representative illustrations. A related position on human generative wellness and how generative ailment wellness can be avoided is besides presented to finish our apprehension of biological science of reproduction. Born in November 1904 in Jaipur ( Rajasthan ) Panchanan Maheshwari rose to go one of the most distinguished phytologists non merely of India but of the full universe.
He moved to Allahabad for higher instruction where he obtained his D. Sc. During his college yearss. he was inspired by Dr W. Dudgeon. an American missionary instructor. to develop involvement in Botany and particularly morphology. His instructor one time expressed that if his pupil progresses in front of him. it will give him a great satisfaction. These words encouraged Panchanan to ask what he could make for his instructor in return. He worked on embryological facets and popularised the usage of embryological characters in taxonomy. He established the Department of Botany. University of Delhi as an of import Centre of research in embryology and tissue civilization. He besides emphasised the demand for induction of work on unreal civilization of immature embryos. These yearss. tissue civilization has become a landmark in scientific discipline. His work on trial tubing fertilization and intra-ovarian pollenation won world-wide acclamation. He was honoured with family of Royal Society of London ( FRS ) . Indian National Science Academy and several other nstitutions of excellence. He encouraged general instruction and made a important part to school instruction by his leading in conveying out the really first text edition of Biology for Higher Secondary Schools published by NCERT in 1964.
Chapter 1: Reproduction IN ORGANISMS
Each and every being can populate merely for a certain period of clip. The period from birth to the natural decease of an being represents its life span. Life spans of a few beings are given in Figure 1. 1. Several other beings are drawn for which you should happen out their life spans and compose in the infinites provided. Analyze the life spans of beings represented in the Figure 1. 1. Isn’t it both interesting and challenging to observe that it may be every bit short as a few yearss or every bit long as a few thousand old ages? Between these two extremes are the life spans of most other life beings. You may observe that life spans of beings are non needfully correlated with their sizes ; the sizes of crows and parrots are non really different yet their life spans show a broad difference. Similarly. a Mangifera indica tree has a much shorter life span as compared to a peepal tree. Whatever be the life span. decease of every single being is a certainty. i. e. . no person is immortal. except one-celled beings. Why do we state there is no natural decease in one-celled beings? Given this world. have you of all time wondered how huge figure of works and animate being species have existed on Earth for several 1000s of old ages? There must be some procedures in life beings that guarantee this continuity. Yes. we are speaking about reproduction. something that we take for granted.
Reproduction is defined as a biological procedure in which an being gives rise to immature 1s ( offspring ) similar to itself. The offspring grow. mature and in bend produce new offspring. Therefore. there is a rhythm of birth. growing and decease. Reproduction enables the continuity of the species. coevals after coevals. You will analyze subsequently in Chapter 5 ( Principles of Inheritance and Variation ) how familial fluctuation is created and inherited during reproduction. There is a big diverseness in the biological universe and each being has evolved its ain mechanism to multiply and bring forth offspring. The organism’s home ground. its internal physiology and several other factors are jointly responsible for how it reproduces. Based on whether there is engagement of one being or two in the procedure of reproduction. it is of two types. When offspring is produced by a individual parent with or without the engagement of gamete formation. the reproduction is nonsexual. When two parents ( opposite sex ) participate in the generative procedure and besides affect merger of male and female gametes. it is called sexual reproduction. 1. 1 ASEXUAL REPRODUCTION
In this method. a individual person ( parent ) is capable of bring forthing offspring. As a consequence. the progeny that are roduced are non merely indistinguishable to one another but are besides exact transcripts of their parent. Are these offspring probably to be genetically indistinguishable or different? The term ringer is used to depict such morphologically and genetically similar persons.
Let us see how widespread nonsexual reproduction is. among different groups of beings. Asexual reproduction is common among one-celled beings. and in workss and animate beings with comparatively simple administrations. In Protists and Monerans. the being or the parent cell divides into two to give rise to new persons ( Figure1. 2 ) . Therefore. in these beings cell division is itself a manner of reproduction. Many one-celled beings reproduce by binary fission. where a cell divides into two halves and each quickly grows into an grownup ( e. g. . Amoeba. Paramecium ) . In barm. the division is unequal and little budsare produced that remain affiliated ab initio to the parent cell which. finally gets separated and maturate into new barm beings ( cells ) . Members of the Kingdom Fungi and simple workss such as algae reproduce through particular nonsexual generative constructions ( Figure 1. 3 ) .
The most common of these constructions are zoospores that normally are microscopic motile constructions. Other common nonsexual generative constructions are conidia ( Penicillium ) . buds ( Hydra ) and gemmules ( sponge ) . You have learnt about vegetive reproduction in workss in Class XI. What do you believe – Is vegetive reproduction besides a type of nonsexual reproduction? Why do you state so? Is the term ringer applicable to the progeny formed by vegetive reproduction? While in animate beings and other simple organisms the term nonsexual is used unequivocally. in workss. the term vegetive reproduction is often used. In workss. the units of vegetive extension such as smuggler. rootstock. chump. tuber. beginning. bulb are all capable of giving rise to new progeny ( Figure1. 4 ) . These constructions are called vegetive propagules. Obviously. since the formation of these constructions does non affect two parents. the procedure involved is nonsexual.
You must hold heard about the flagellum of the H2O organic structures or about the ‘terror of Bengal’ . This is nil but the aquatic works ‘water hyacinth’ which is one of the most invasive weeds found turning wherever there is standing H2O. It drains O from the H2O. which leads to decease of fishes. You will larn more about it in Chapters 13 and 14. You may happen it interesting to cognize that this works was introduced in India because of its beautiful flowers and form of foliages. Since it can propagate vegetatively at a phenomenal rate and spread all over the H2O organic structure in a short period of clip. it is really hard to acquire rid off them. Are you cognizant how workss like murphy. sugar cane. banana. ginger. Dahlia pinnatas are cultivated? Have you seen little workss emerging from the buds ( called eyes ) of the murphy tuber. from the rootstocks of banana and ginger?
When you carefully seek to find the site of beginning of the new plantlets in the workss listed supra. you will detect that they constantly arise from the nodes present in the modified root of these workss. When the nodes come in contact with moist dirt or H2O. they produce roots and new workss. Similarly. adventitious buds arise from the notches present at borders of foliages of Bryophyllum. This ability is to the full exploited by nurserymans and husbandmans for commercial extension of such workss. It is interesting to observe that nonsexual reproduction is the common method of reproduction in beings that have a comparatively simple administration. like algae and Fungi and that they shift to sexual method of reproduction merely before the oncoming of inauspicious conditions. Find out how sexual reproduction enables these beings to last during unfavorable conditions? Why is sexual reproduction favoured under such conditions? Asexual ( vegetive ) every bit good as sexual manners of reproduction are exhibited by the higher workss. On the other manus. merely sexual manner of reproduction is present in most of the animate beings. 1. 2 SEXUAL REPRODUCTION
Sexual reproduction involves formation of the male and female gametes. either by the same person or by different persons of the opposite sex. These gametes fuse to organize the fertilized ovum which develops to organize the new being. It is an luxuriant. complex and slow procedure as compared to nonsexual reproduction. Because of the merger of male and female gametes. sexual reproduction consequences in offspring that are non indistinguishable to the parents or amongst themselves. A survey of diverse organisms– workss. animate beings or fungi–show that though they differ so greatly in external morphology. internal construction and physiology. when it comes to sexual manner of reproduction. surprisingly. they portion a similar form. Let us foremost discourse what characteristics are common to these diverse beings. All beings have to make a certain phase of growing and adulthood in their life. before they can reproduce sexually. That period of growing is called the juvenile stage. It is known as vegetive stage in workss. This stage is of variable continuances in different beings. The terminal of juvenile/vegetative stage which marks the beginning of the generative stage can be seen easy in the higher workss when they come to bloom.
How long does it take for marigold/rice/wheat/coconut/ Mangifera indica workss to come to bloom? In some workss. where blooming occurs more than one time. what would you name the inter-flowering period – juvenile or mature? Detect a few trees in your country. Do they bloom during the same month twelvemonth after twelvemonth? Why do you believe the handiness of fruits like Mangifera indica. apple. Artocarpus heterophyllus. etc. . is seasonal? Are at that place some workss that flower throughout the twelvemonth and some others that show seasonal blossoming? Plants –the one-year and two-year types. show clear cut vegetive. generative and aging stages. but in the perennial species it is really hard to clearly specify these stages. A few workss exhibit unusual blossoming phenomenon ; some of them such as bamboo species flower merely one time in their life clip. by and large after 50-100 old ages. bring forth big figure of fruits and dice. Another works. Strobilanthus kunthiana ( neelakuranji ) . flowers one time in 12 old ages. As many of you would be cognizing that this works flowered during September-October 2006. Its mass blossoming transformed big paths of hilly countries in Kerala. Karnataka and Tamil Nadu into bluish stretches and attracted a big figure of tourers. In animate beings. the juvenile stage is followed by morphological and physiological alterations prior to active generative behavior.
The generative stage is besides of variable continuance in different beings. Can you name the alterations seen in human existences that are declarative of generative adulthood? Among animate beings. for illustration birds. do they put eggs all through the twelvemonth? Or is it a seasonal phenomenon? What about other animate beings like toads and lizards? You will detect that. birds populating in nature ballad eggs merely seasonally. However. birds in imprisonment ( as in domestic fowl farms ) can be made to put eggs throughout the twelvemonth. In this instance. puting eggs is non related to reproduction but is a commercial development for human public assistance. The females of placental mammals exhibit cyclical alterations in the activities of ovaries and accessary canals every bit good as endocrines during the generative stage. In non-primate mammals like cattles. sheep. rats. cervids. Canis familiariss. tiger. etc. . such cyclical alterations during reproduction are called oestrus rhythm where as in Primatess ( monkeys. apes. and worlds ) it is calledmenstrual rhythm. Many mammals. particularly those populating in natural. wild conditions exhibit such rhythms merely during favorable seasons in their generative stage and are hence called seasonal breeders.
Many other mammals are reproductively active throughout their generative stage and hence are called uninterrupted breeders. That we all grow old ( if we live long plenty ) . is something that we recognise. But what is meant by turning old? The terminal of generative stage can be considered as one of the parametric quantities of aging or old age. There are attendant alterations in the organic structure ( like deceleration of metamorphosis. etc. ) during this last stage of life span. Old age finally leads to decease. In both workss and animate beings. endocrines are responsible for the passages between the three stages. Interaction between endocrines and certain environmental factors regulate the generative procedures and the associated behavioral looks of beings.
Events in sexual reproduction: After attainment of adulthood. all sexually reproducing organisms exhibit events and procedures that have singular cardinal similarity. even though the constructions associated with sexual reproduction are so really different. The events of sexual reproduction though luxuriant and complex. follow a regular sequence. Sexual reproduction is characterised by the merger ( or fertilization ) of the male and female gametes. the formation of fertilized ovum and embryogenesis. For convenience these consecutive events may be grouped into three distinguishable phases viz. . the pre-fertilisation. fertilization and the post-fertilisation events. 1. 2. 1 Pre-fertilisation Events
These include all the events of sexual reproduction prior to the merger of gametes. The two chief pre-fertilisation events are gametogenesis and gamete transportation. 1. 2. 1. 1 Gametogenesis
As you are already cognizant gametogenesis refers to the procedure of formation of the two types of gametes – male and female. Gametes are monoploid cells. In some algae the two gametes are so similar in visual aspect that it is non possible to categorize them into male and female gametes. They are therefore called homogametes ( isogametes ) ( Figure 1. 5a ) . However. in a bulk of sexually reproducing organisms the gametes produced are of two morphologically distinguishable types ( heterogametes ) . In such organisms the male gamete is called the spermatozoid or sperm and the female gamete is called the egg or egg cell ( Figure1. 5 b. degree Celsius ) . Sex in beings: Sexual reproduction in beings by and large involves the merger of gametes from two different persons. But this is non ever true. From your remembrance of illustrations studied in Class XI. can you place instances where self-fertilization is observed? Of class. mentioning such illustrations in workss is easy. Plants may hold both male and female generative constructions in the same works ( bisexual ) ( Figure 1. 6 c. vitamin E ) or on different workss ( unisexual ) ( Figure 1. 6d ) .
In several Fungis and workss. footings such as homothallic and monecious are used to denote the bisexual status and heterothallic and dioecian are the footings used to depict unisexual status. In blooming workss. the unisexual male flower is antheral. i. e. . bearing stamens. while the female is carpellate or bearing pistils. In some blossoming workss. both male and female flowers may be present on the same person ( monecious ) or on separate persons ( dioecian ) . Some illustrations of monecious workss are cucurbits and coconuts and of dioecian workss are papaya and day of the month thenar. Name the type of gametes that are formed in staminate and pistillate flowers. But what about animate beings? Are persons of all species either male or female ( unisexual ) ? Or are there species which possess both the generative variety meats ( bisexual ) ? You likely can do a list of several unisexual animate being species. Earthworms. ( Figure 1. 6a ) sponge. cestode and bloodsucker. typical illustrations of bisexual animate beings that possess both male and female generative variety meats. are intersexs. Cockroach ( Figure 1. 6b ) is an illustration of a unisexual species.
Cell division during gamete formation: Gametes in all heterogametic species are of two types viz. . male and female. Gametes are monoploid though the parent works organic structure from which they arise may be either haploid or diploid. A monoploid parent produces gametes by mitotic division. Does this mean that miosis ne’er occurs in beings that are haploid? Carefully analyze the flow charts of life rhythms of algae that you have studied in Class XI ( Chapter 3 ) to acquire a suited reply. Several beings belonging to monera. Fungis. algae and nonvascular plants have haploid works organic structure. but organisms belonging to nonflowering plants. gymnosperms. flowering plants and most of the animate beings including human existences. the parental organic structure is diploid. It is obvious that miosis. the decrease division. has to happen if a diploid organic structure has to bring forth monoploid gametes. In diploid beings. specialised cells called meiocytes ( gamete mother cell ) undergo miosis. At the terminal of miosis. merely one set of chromosomes gets incorporated into eachgamete. Carefully study Table 1. 1 and make full in the diploid and monoploid chromosome Numberss of beings. Is at that place any relationship in the figure of chromosomes of meiocytes and gametes? 1. 2. 1. 2 Gamete Transportation
After their formation. male and female gametes must be physically brought together to ease merger ( fertilization ) . Have you of all time wondered how the gametes run into? In a bulk of beings. male gamete is motile and the female gamete is stationary. Exceptions are a few Fungi and algae in which both types of gametes are motile ( Figure1. 7a ) . There is a demand for a medium through which the male gametes move. In several simple workss like algae. nonvascular plants and nonflowering plants. H2O is the medium through which this gamete transportation takes topographic point. A big figure of the male gametes. nevertheless. neglect to make the female gametes. To counterbalance this loss of male gametes during conveyance. the figure of male gametes produced is several thousand times the figure of female gametes produced. In seed workss. pollen grains are the bearers of male gametes and ovule have the egg.
Pollen grains produced in anthers hence. hold to be transferred to the stigma before it can take to fertilization ( Figure 1. 7b ) . In bisexual. self-fertilising workss. e. g. . peas. transportation of pollen grains to the stigma is comparatively easy as anthers and stigma are located near to each other ; pollen grains shortly after they are shed. come in contact with the stigma. But in cross pollinating workss ( including dioecian workss ) . a specialized event called pollinationfacilitates transportation of pollen grains to the stigma. Pollen grains germinate on the stigma and the pollen tubes transporting the male gametes reach the ovule and dispatch male gametes near the egg. In dioecian animate beings. since male and female gametes are formed in different persons. the being must germinate a particular mechanism for gamete transportation. Successful transportation and coming together of gametes is indispensable for the most critical event in sexual reproduction. the fertilization. 1. 2. 2 Fertilization
The most critical event of sexual reproduction is possibly the merger of gametes. This procedure called syngamy consequences in the formation of a diploid fertilized ovum. The term fertilization is besides frequently used for this procedure. The footings syngamy and fertilization are often used though. interchangeably. What would go on if syngamy does non happen? However. it has to be mentioned here that in some beings like rotifers. Apis melliferas and even some lizards and birds ( Meleagris gallopavo ) . the female gamete undergoes development to organize new beings without fertilization. This phenomenon is called parthenogeny. Where does syngamy happen? In most aquatic beings. such as a bulk of algae and fishes every bit good as amphibious vehicles. syngamy occurs in the external medium ( H2O ) . i. e. . outside the organic structure of the being. This type of gametic merger is called external fertilization.
Organisms exhibiting external fertilization show great synchronism between the sexes and let go of a big figure of gametes into the environing medium ( H2O ) in order to heighten the opportunities of syngamy. This happens in the bony fishes and toads where a big figure of offspring are produced. A major disadvantage is that the progeny are highly vulnerable to marauders endangering their endurance up to adulthood. In many tellurian beings. belonging to fungi. higher animate beings such as reptilians birds. mammals and in a bulk of workss ( nonvascular plants. nonflowering plants. gymnosperms and flowering plants ) . syngamy occurs inside the organic structure of the being. hence the procedure is called internal fertilization. In all these beings. egg is formed inside the female organic structure where they fuse with the male gamete. In organisms exhibiting internal fertilization. the male gamete is motile and has to make the egg in order to blend with it. In these even though the figure of sperms produced is really big. there is a important decrease in the figure of eggs produced. In seed workss. nevertheless. the non-motile male gametes are carried to female gamete by pollen tubings. 1. 2. 3 Post-fertilisation Events
Events in sexual reproduction after the formation of fertilized ovum are called post-fertilisation events. 1. 2. 3. 1 The Zygote
Formation of the diploid fertilized ovum is cosmopolitan in all sexually reproducing beings. In organisms with external fertilization. fertilized ovum is formed in the external medium ( normally H2O ) . whereas in those exhibiting internal fertilization. fertilized ovum is formed inside the organic structure of the being. Further development of the fertilized ovum depends on the type of life rhythm the being has and the environment it is exposed to. In organisms belonging to fungi and algae. fertilized ovum develops a midst wall that is immune to dessication and harm. It undergoes a period of remainder before sprouting. In organisms with haplontic life rhythm ( As you have read in Class XI ) . fertilized ovum divides by miosis to organize haploid spores that grow into monoploid persons. Consult your Class XI book and happen out what sort of development takes topographic point in the fertilized ovum in beings with diplontic and haplo-diplontic life rhythms. Zygote is the critical nexus that ensures continuity of species between beings of one coevals and the following. Every sexually reproducing being. including human existences begin life as a individual cell–the fertilized ovum. 1. 2. 3. 2 Embryogenesis
Embryogenesis refers to the procedure of development of embryo from the fertilized ovum. During embryogenesis. fertilized ovum undergoes cell division ( mitosis ) and cell distinction. While cell divisions increase the figure of cells in the underdeveloped embryo ; cell distinction helps groups of cells to undergo certain alterations to organize specialized tissues and variety meats to organize an being. You have studied about the procedure of cell division and distinction in the old category. Animals are categorised into oviparous and live-bearing based on whether the development of the fertilized ovum take topographic point outside the organic structure of the female parent or interior. i. e. . whether they lay fertilised/unfertilised eggs or give birth to immature 1s. In oviparous animate beings like reptilians and birds. the fertilised eggs covered by difficult chalky shell are laid in a safe topographic point in the environment ; after a period of incubation immature 1s hatch out.
On the other manus. in live-bearing animate beings ( bulk of mammals including human existences ) . the fertilized ovum develops into a immature one inside the organic structure of the female being. After achieving a certain phase of growing. the immature 1s are delivered out of the organic structure of the female being. Because of proper embryologic attention and protection. the opportunities of endurance of immature 1s is greater in live-bearing beings. In blooming workss. the fertilized ovum is formed inside the ovule. After fertilization the sepals. petals and stamens of the flower wither and autumn away. Can you call a works in which the sepals remain attached? The pistil nevertheless. remains affiliated to the works. The fertilized ovum develops into the embryo and the ovules develop into the seed. The ovary develops into the fruit which develops a midst wall called seed vessel that is protective in map ( Figure 1. 8 ) . After dispersion. seeds germinate under favorable conditions to bring forth new workss.
Reproduction enables a species to populate coevals after coevals. Reproduction in beings can be loosely classified into nonsexual and sexual reproduction. Asexual reproduction does non affect the formation or merger of gametes. It is common in beings that have a comparatively simple administration such as the Fungi. algae and some invertebrate animate beings. The progeny formed by nonsexual reproduction are indistinguishable and are referred to as ringers. Zoospores. conidiospore. etc. . are the most common nonsexual constructions formed in several algae and Fungis. Budding and gemmule formation are the common nonsexual methods seen in animate beings. Prokaryotes and unicellular beings reproduce asexually by cell division or binary fission of the parent cell. In several aquatic and tellurian species of flowering plants. constructions such as smugglers. rootstocks. chumps. tubers. beginnings. etc. . are capable of giving rise to new offspring. This method of nonsexual reproduction is by and large referred to as vegetive extension.
Sexual reproduction involves the formation and merger of gametes. It is a complex and slower procedure as compared to nonsexual reproduction. Most of the higher animate beings reproduce about wholly by sexual method. Events of sexual reproduction may be categorised into pre-fertilisation. fertilization and post-fertilisation events. Pre-fertilisation events include gametogenesis and gamete transportation while post-fertilisation events include the formation of fertilized ovum and embryogenesis. Organisms may be bisexual or unisexual. Sex in workss is varied. peculiarly in flowering plants. due to the production of diverse types of flowers. Plants are defined as monecious and dioecian. Flowers may be bisexual or unisexual flowers. Gametes are haploid in nature and normally a direct merchandise of meiotic division except in haploid beings where gametes are formed by mitosis.
Transportation of male gametes is an indispensable event in sexual reproduction. It is comparatively easy in bisexual beings. In unisexual animate beings it occurs by sexual intercourse or coincident release. In flowering plants. a particular procedure called pollenation ensures transportation of pollen grains which carry the pollen grains to the stigma. Syngamy ( fertilization ) occurs between the male and female gametes. Syngamy may happen either externally. outside the organic structure of beings or internally. inside the organic structure. Syngamy leads to formation of a specialised cell called fertilized ovum. The procedure of development of embryo from the fertilized ovum is called embryogenesis. In animate beings. the fertilized ovum starts developing shortly after its formation. Animals may be either oviparous or live-bearing. Embryonic protection and attention are better in live-bearing beings. In blooming workss. after fertilization. ovary develops into fruit and ovules mature into seeds. Inside the mature seed is the primogenitor of the following coevals. the embryo. Exercise
1. Why is reproduction indispensable for beings?
2. Which is a better manner of reproduction: sexual or nonsexual? Why? 3. Why is the offspring formed by nonsexual reproduction referred to as ringer? 4. Offspring formed due to sexual reproduction have better opportunities of endurance. Why? Is this statement ever true?
5. How does the offspring formed from nonsexual reproduction differ from those formed by sexual reproduction?
6. Distinguish between nonsexual and sexual reproduction. Why is vegetive reproduction besides considered as a type of nonsexual reproduction? 7. What is vegetive extension? Give two suited illustrations. 8. Specify
( a ) Juvenile stage.
( B ) Reproductive stage.
( degree Celsius ) Senescent stage.
9. Higher beings have resorted to sexual reproduction in malice of its complexness. Why? 10. Explain why miosis and gametogenesis are ever interlinked? 11. Identify each portion in a blossoming works and compose whether it is monoploid ( n ) or diploid ( 2n ) .
( a ) Ovary ———————————
( B ) Anther ———————————
( degree Celsius ) Egg ———————————
( vitamin D ) Pollen ———————————
( vitamin E ) Male gamete ———————————
( degree Fahrenheit ) Zygote ———————————
12. Define external fertilization. Mention its disadvantages. 13. Differentiate between a zoospore and a ten fertilized ovum.
14. Differentiate between gametogenesis from embryogenesis.
15. Describe the post-fertilisation alterations in a flower.
16. What is a bisexual flower? Collect five bisexual flowers from your vicinity and with the aid of your instructor happen out their common and scientific names. 17. Analyze a few flowers of any cucurbit works and seek to place the staminate and pistillate flowers. Do you cognize any other works that bears unisexual flowers? 18. Why are offspring of oviparous animate beings at a greater hazard as compared to offspring of live-bearing animate beings? Multiple-choice Question
1. A few statements depicting certain characteristics of reproduction are given below: i. Gametic merger takes topographic point
two. Transportation of familial stuff takes topographic point
three. Reduction division takes topographic point
four. Progeny have some resemblance with parents
Choose the options that are true for both nonsexual and sexual reproduction from the options given below:
( a ) I and two ; ( B ) two and three ; ( degree Celsius ) two and four ; ( vitamin D ) I and three. 2. The term ‘clone’ can non be applied to offspring formed by sexual reproduction because: a. Offspring do non possess exact transcripts of parental Deoxyribonucleic acid
b. Deoxyribonucleic acid of merely one parent is copied and passed on to the offspring c. Offspring are formed at different times
d. Deoxyribonucleic acid of parent and offspring are wholly different.
3. Amoeba and Yeast reproduce asexually by fission and budding severally. because they are: a. Microscopic organisms
b. Heterotrophic beings
c. Unicellular beings
d. Uninucleate beings.
4. A few statements with respect to sexual reproduction are given below: I. Sexual reproduction does non ever necessitate two persons ii. Sexual reproduction by and large involves gametic merger
three. Meiosis ne’er occurs during sexual reproduction
four. External fertilization is a regulation during sexual reproduction Choose the right statements from the options below:
( a ) I and four ( B ) I and two ( degree Celsius ) two and three ( vitamin D ) I and four
5. A multicellular. filiform alga exhibits a type of sexual life rhythm in which the meiotic division occurs after the formation of fertilized ovum. The grownup fibril of this alga has a. monoploid vegetive cells and diploid gametangia
b. diploid vegetive cells and diploid gametangia
c. diploid vegetive cells and haploid gametangia
d. haploid vegetive cells and monoploid gametangia.
6. The male gametes of rice works have 12 chromosomes in their karyon. The chromosome figure in the female gamete. fertilized ovum and the cells of the seedling will be. severally. a. 12. 24. 12
B. 24. 12. 12
c. 12. 24. 24
d. 24. 12. 24.
7. Given below are a few statements related to external fertilisation. Choose the right statements. I. The male and female gametes are formed and released at the same time two. Merely a few gametes are released into the medium
three. Water is the medium in a bulk of beings exhibiting external fertilisation four. Offspring formed as a consequence of external fertilisation have better opportunity of endurance than those formed inside an being
( a ) three and four ( B ) I and three ( degree Celsius ) two and four ( vitamin D ) I and four
8. The statements given below describe certain characteristics that are observed in the pistil of flowers. i. Pistil may hold many carpels
two. Each carpel may hold more than one ovule
three. Each carpel has merely one ovule
four. Pistil have merely one carpel
Choose the statements that are true from the options below:
( a ) I and two ( B ) I and three ( degree Celsius ) two and four ( vitamin D ) three and four
9. Which of the undermentioned state of affairss right describe the similarity between an angiosperm egg and a human egg? i. Eggs of both are formed merely one time in a life-time
two. Both the flowering plant egg and human egg are stationary
three. Both the flowering plant egg and human egg are motile transported four. Syngamy in both consequences in the formation of fertilized ovum
Choose the correct reply from the options given below:
( a ) two and four ( B ) iv merely ( degree Celsius ) three and four ( vitamin D ) I and four
10. Appearance of vegetive propagules from the nodes of workss such as sugar cane and ginger is chiefly because: a. Nodes are shorter than internodes
B. Nodes have meristematic cells
c. Nodes are located near the dirt
d. Nodes have non-photosynthetic cells
11. Which of the undermentioned statements. back up the position that luxuriant sexual generative procedure appeared much later in the organic development. I. Lower groups of beings have simpler organic structure design
two. Asexual reproduction is common in lower groups
three. Asexual reproduction is common in higher groups of organisms four. The high incidence of sexual reproduction in flowering plants and craniates Choose the correct reply from the options given below:
( a ) I and three ; ( b ) I and three ( degree Celsius ) two and four ( vitamin D ) two and three
12. Offspring formed by sexual reproduction exhibit more fluctuation than those formed by Asexual reproduction because: a. Sexual reproduction is a drawn-out procedure
b. Gametes of parents have qualitatively different familial composing c. Genetic stuff comes from parents of two different species d. Greater sum of DNA is involved in sexual reproduction. 13. Choose the right statement from amongst the followers: a. Dioecious ( intersex ) being
are seen merely in animate beings b. Dioecious beings are seen merely in workss
c. Dioecious beings are seen in both workss and animate beings
d. Dioecious beings are seen merely in craniates
14. There is no natural decease in individual celled beings like Amoeba and bacteriums because:
a. They can non reproduce sexually
B. They reproduce by binary fission
c. Parental organic structure is distributed among the progeny
d. They are microscopic
15. There are assorted types of reproduction. The type of reproduction adopted by an being depends on:
a. The home ground and morphology of the being
b. Morphology of the being
c. Morphology and physiology of the being
d. The organism’s home ground. physiology and familial make-up
16. Identify the wrong statement.
a. In nonsexual reproduction. the progeny produced are morphologically and genetically indistinguishable to the parent b. Zoospores are sexual generative constructions
c. In nonsexual reproduction. a individual parent produces offspring with or without the formation of gametes d. Conidia are nonsexual constructions in Penicillium
17. Which of the followers is a post-fertilisation event in blooming workss? a. Transportation of pollen grains
b. Embryo development
c. Formation of flower
d. Formation of pollen grains
18. The figure of chromosomes in the shoot tip cells of a corn works is 20. The figure of chromosomes in the microspore female parent cells of the same works shall be: a. 20
Very Short ANSWER TYPE QUESTIONS
1. Mention two built-in features of Amoeba and barm that enable them
to reproduce asexually. 2. Why do we mention to offspring formed by nonsexual method of reproduction as ringers? 3. Although potato tuber is an belowground portion. it is considered as a root. Give two grounds. 4. Between an one-year and a perennial works. which 1 has a shorter juvenile stage? Give one ground. 5. Rearrange the undermentioned events of sexual reproduction in the sequence in which they occur in a blossoming works: embryogenesis. fertilization. gametogenesis. pollenation. 6. The chance of fruit set in a self-fertilized bisexual flower of a works is far greater than a dioecian works. Explain. 7. Is the presence of big figure of chromosomes in an being a hinderance to sexual reproduction? Justify your reply by giving suited grounds. 8. Is at that place a relationship between the size of an being and its life span? Give two illustrations in support of your reply. 9. In the figure given below the works bears two different types of flowers marked ‘A’ and ‘B’ . Identify the types of flowers and province the type of pollenation that will happen in them. 10. Give grounds as to why cell division can non be a type of reproduction in multicellular beings. 11. In the figure given below. tag the ovule and seed vessel.
12. Why do gametes produced in big Numberss in organisms exhibit external fertilization? 13. Which of the followerss are monecious and dioecian beings. a. Earthworm ______________
b. Chara ______________
c. Marchantia ______________
d. Cockroach ______________
14. Match the beings given in Column-’A’ with the vegetive propagules given in column ‘B’ .
Col. A Col. B i. Bryophyllum a ) beginning
two. Agave B ) eyes iii. Potato degree Celsius ) foliage buds four. Water hyacinth vitamin D ) bulblets
15. What do the undermentioned parts of a flower develop into after fertilization? a. Ovary ______________
b. Ovules ______________
Short ANSWER TYPE QUESTIONS
1. In monoploid beings that undergo sexual reproduction. call the phase in the life rhythm when miosis occurs. Give grounds for your reply. 2. The figure of taxa exhibiting nonsexual reproduction is drastically reduced in higher workss ( flowering plants ) and higher animate beings ( craniates ) as compared with lower groups of workss and animate beings. Analyse the possible grounds for this state of affairs. 3. Honeybees produce their immature 1s merely by sexual reproduction. Inspite of this. in a settlement of bees we find both haploid and diploid persons. Name the haploid and diploid persons in the settlement and analyze the grounds behind their formation. 4. With which type of reproduction do we tie in the decrease division? Analyse the grounds for it.
5. Is it possible to see vegetive extension observed in certain workss like Bryophyllum. H2O jacinth. ginger etc. . as a type of nonsexual reproduction? Give two/three grounds. 6. ‘Fertilisation is non an obligatory event for fruit production in certains plants’ . Explain the statement. 7. In a underdeveloped embryo. analyze the effects if cell divisions are non followed by cell distinction. 8. List the alterations observed in an flowering plant flower subsequent to pollenation and fertilization. 9. Propose a possible account why the seeds in a pea cod are arranged in a row. whereas those in tomato are scattered in the juicy mush. 10. Pull the studies of a zoospore and a conidiospore. Mention two unsimilarities between them and atleast one characteristic common to both constructions. 11. Justify the statement ‘Vegetative reproduction is besides a type of nonsexual reproduction’ . LONG ANSWER TYPE QUESTIONS
1. Enumerate the differences between nonsexual and sexual reproduction. Describe the types of nonsexual reproduction exhibited by unicellular beings. 2. Make all the gametes formed from a parent being have the same familial composing ( indistinguishable DNA transcripts of the parental genome ) ? Analyse the state of affairs with the background of gametogenesis and supply or give suited account. 3. Although sexual reproduction is a long drawn. energy-intensive complex signifier of reproduction. many groups of beings in Kingdom Animalia and Plantae prefer this manner of reproduction. Give atleast three grounds for this. 4. Differentiate between ( a ) heat and catamenial rhythms ; ( B ) ovipary and vivipary. Cite an illustration for each type. 5. Rose workss produce big. attractive bisexual flowers but they seldom produce fruits. On the other manus a tomato works produces plentifulness of fruits though they have little flowers. Analyse the grounds for failure of fruit formation in rose. Both these workss – rose and tomato – both selected by human existences for different features. the rose for its flower and tomato for its fruit. Roses. being vegetatively propagated do non necessitate to bring forth seeds.