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STUDY COURSE MATERIAL BIOLOGY SESSION-2020-21 CLASS-XII
TOPIC: REPRODUCTION IN ORAGANISM
DAY-1
TEACHING MATERIAL :- INTRODUCTION
Life Span: Each and every organism is capable to live only for a limited period of time. Lifespan refers to the life expectancy or longevity of an individual. The period from birth to the natural death of an organism known as its life span.
Reproduction: Reproduction is defined as a biological process in which an organism gives rise to young ones (offspring) similar to itself. The offspring grow mature and in turn produce new offspring. Thus there is a cycle of birth, growth and death.
The main purpose of reproduction are to: continue and preserve the specie pass species genetic identity keep the evolutionary chain going
Page 1 of 21 Types of reproduction: Based on whether there is participation of one organism or two in the process of reproduction, it is of two types. Asexual reproduction: When offspring is produced by a single parent with or without the involvement of gamete formation the reproduction is asexual. Sexual reproduction: When two parents (opposite sex) participate in the reproductive process and also involved fusion of male and female gametes it is called sexual reproduction.
ASSIGNMENT
Q.1. Why is reproduction essential for organisms? Q.2. Which is better mode of reproduction: sexual or asexual? Why?
MULTIPLE CHOICE QUESTIONS : -
Q.1. Which physiological process is necessary for birth, growth, death, production of offspring and for continuity of the species? (a) Digestion (b) Transportation (c) Reproduction (d) Nutrition
Q.2. Which of the following statement is correct? (a) all the individuals of a species have exactly the same lifespan (b) smaller organisms always have shorter lifespan and vice versa (c) lifespan of an organism is the time period from his birth to its natural death (d) no organism may have a lifespan of several hundred years Page 2 of 21 Q.3. Which of the following has the longest life span? (a) banyan tree (b) tortoise (c) parrot (d) elephant
Q.4 Identify the given organism and find its maximum lifespan. (a) sparrow, 25 years (b) crow, 30 years
(c) eagle, 40 years (d) crow,15 years
Q.5. The term "clone" cannot be applied to offspring formed by sexual reproduction because (a) offspring do not possess exact copies of parental DNA (b) DNA of only one parent is copied and passed onto offspring (c) offspring are formed at different times (d) DNA of parent and offspring are completely different
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DAY-2
TEACING MATERIAL : - MODES OF REPRODUCTION IN ( DETAIL)
ASEXUAL REPRODUCTION Asexual reproduction is without union of gametes are sex cells. The offsprings that are produced a sexually are not only identical to one another but also exact copies of their parent. Morphologically and genetically identical individuals produced by asexual reproduction is termed as clones. The characteristics of asexual reproduction are: No waste of time on searching for partners No production of gametes Rapid multiplication with same genetic material Descendants are similar to the parent
Page 3 of 21 Able to colonize a large surface rapidly.
Advantages and disadvantages of asexual reproduction: -
Types of Asexual reproduction
Asexual reproduction takes place by several methods like fees and fragmentation and regeneration is spore formation vegetative propagation. It is common among single celled organisms and in plants and animals with relatively simple organisations.
Page 4 of 21 Fission:
Fission is a kind of reproduction in which a cell or body divides into two or more parts and each part grows into a whole new individual.
. Binary fission Division of parent into two small nearly equal sized daughter individual . e.g., amoeba, bacteria, protozoans and planarians
NCERT MATERIAL
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VIDEO-LINKS
LINK 1
https://youtu.be/WPlMKKNsv9k Page 5 of 21
LINK 2
https://youtu.be/D3FN3jLlT54
PPT LINKS
https://www.slideshare.net/mobile/jcott5/asexual-reproduction-12686418
DOCUMENT LINK
https://schools.aglasem.com/18706
ASSIGNMENT
Q. With the help of labelled bdiagram explain binary fission in amoeba.
MULTIPLE CHOICE QUESTION
Q.1. Asexual reproduction is seen in members of Kingdom a. Monera b. Plantae c. Animalia d. All of these
Q.2. A few statements describing certain features of reproduction are given below: i. Gametic fusion takes place ii. Transfer of genetic material takes place iii. Reduction division takes place iv. Progeny have some resemblance with parents
select the options that are true for both asexual and sexual reproduction from the options given below a. i and ii b. ii and III c. ii and IV d. i and iii
Q.3. ______is the most common type of asexual reproduction.
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DAY-3
TEACING MATERIAL : - ASEXUAL REPRODUCTION
. Multiple fission
Division of parent into many small daughter individuals simultaneously. e.g., plasmodium
Difference between binary fission and multiple fission
Page 7 of 21 Budding: A new individual develops from a small projection on the bud arising from parent organism. The initial protuberance of proliferating cytoplasm or cells the buds, eventually develops into an organism duplicating the parent. The new individual may separate or exist independently or the buds may remain attached forming aggregates or colonies. e.g., Scypha , Hydra internal buds called gemmules are found in some freshwater sponges. e.g.,spongilla
NCERT MATERIAL
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VIDEO-LINKS
LINK 1
https://youtu.be/WPlMKKNsv9k
LINK 2
https://youtu.be/D3FN3jLlT54
LINK 3
https://youtu.be/T3_-5L0hB5o
PPT LINKS
Page 8 of 21 https://www.slideshare.net/mobile/jcott5/asexual-reproduction-12686418
DOCUMENTS LINKS
https://schools.aglasem.com/18706
ASSIGNMENT
Q.1. In yeast and amoeba. the parent cell device to give rise to to new individual cells how does the cell division different and these two organisms.
MULTIPLE CHOICE QUESTION
Q.1. During binary fission in amoeba which of the following organelles is duplicated? a. plasma membrane b. nucleus c. contractile vacuole d. all of these
Q.2. Which one of the following processes results in the formation of clone of bacteria? a. Regeneration b. Budding c. Binary fission d. Fragmentation
Q.3.Amoeba and yeast reproduce asexually by fission and budding respectively, because they are: a. Unicellular organisms b. Uninucleate organisms c. Heterotrophic organisms d. Microscopic organisms
DAY-4
TEACING MATERIAL : - ASEXUAL REPRODUCTION
Page 9 of 21 Fragmentation:
Fragmentation in multicellular organisms is a form of asexual reproduction in which an organism is split into fragments. Each of these fragments develop into matured, fully grown individuals that are identical to their parents. The splitting may or may not be intentional – it may or may not occur due to man-made or natural damage by the environment or predators. This kind of organism may develop specific organs or zones that may be shed or easily broken off. If the splitting occurs without the prior preparation of the organism, both fragments must be able to regenerate the complete organism for it to function as reproduction. Fragmentation, also known as splitting, as a method of reproduction is seen in many organisms such as filamentous cyanobacteria, molds, lichens, many plants, and animals such as sponges, acoel flatworms, some annelid worms and sea stars. In echinoderms, this method of reproduction is usually known as fissiparity.
Regeneration:
Page 10 of 21 Regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Many protists like amoeba that have been cut in half can grow back into complete organisms so long as enough of the nuclear material is undamaged. Several cell parts such as flagella, can also be regrown in protists. Multicellular organisms like sponge, hydra ,planaria etc possess great regenerating capacity. There is a closed correlation between regeneration and reproduction. The methods by which organisms reproduce themselves have much in common with regenerative processes.
Spore Formation:
Spore formation is a method of asexual reproduction. Plants like ferns, moss, fungi reproduce by this method. Spores are unicellular reproductive bodies present in sac called sporangia. When spores mature sporangia burst and spores are carried to different location by air, wind, water. When spores fall on a suitable ground, they germinate and develop new individuals. Among the fungi, spores serve a function similar to that of seeds. They are produced and released by specialised fruiting bodies. Fungi produce two major types of asexual spores: sporangiopores and conidia.
. Sporangiospores:
Fig; Sporangiophores of Rhizopus
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Endogenius form and contained within a sporangium. Formed as a result of the cleavage of protoplasm around nuclei. Followed in some cases by formation of a wall around each nucleate portion of protoplasm. Characteristic of enjoy belonging to the phycomycetes, oomycetes and hyphochytriomycetes. Two main types - zoopores (motile) and aplanospores ( non- motile).
Page 12 of 21 . Conidia: A conidium (plural conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (plural chlamydoconidia), is an asexual, non-motile spore of a fungus. Exogenous often formed at the tip of supporting hyphae called conidiophores. Develop in a variety of ways.
Fig; Conidia of Penicillium
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VIDEO-LINKS
LINK 1 https://youtu.be/e3aEjXdYPH4
LINK 2 https://youtu.be/T3_-5L0hB5o
LINK 3 https://youtu.be/8huFa4yrqjg
PPT LINKS
https://www.slideshare.net/mobile/jcott5/asexual-reproduction-12686418
https://www.learnpick.in/prime/documents/ppts/details/1049/class-12th-biology-cbse- chapter-1-reproduction-in-organisms-
DOCUMENTS LINKS
https://schools.aglasem.com/18706
https://mycbseguide.com/blog/reproduction-organisms-class-12- notes-biology/
ASSIGNMENT
Q.1. With the help of a well labelled diagram explain the following: a. Fragmentation b. Regeneration c. Spore formation
Q.2 Name the the respective asexual reproductive structures of yeast and sponge.
Q.3. Draw the sketches of zoospores and conidium. Mention two dissimilarities between them and at least one feature common to both structures.
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DAY-5
TEACING MATERIAL : - ASEXUAL REPRODUCTION
. Vegetative Propagation: Vegetative propagation is the production of new plants from the vegetative parts of the plant. Roots, stems and leaves are called the vegetative parts of a plant. It does not involve flowers,pollination and seed production.
. Methods of vegetative propagation
1: natural method 2: artificial method
. Natural Methods of Vegetative Propagation
In these, vegetative propagules (somatic parts) of the plant detach from the parent body. These develop into new plants under suitable condition
. By roots
Page 15 of 21 Buds develop in thick, fleshy roots which later, when put into soil develop into new plants
e.g., Guava, sweet potato, dahlia
. By stem Vegetative propagation occurs through stems when new plants arise from the nodes. This is where buds are formed, which grow into new plants.
Stems that grow horizontally on the ground are called runners. As these runners grow, buds are formed at the nodes, which later develop the roots and shoots, resulting in the formation of a new plant. Example – Cyanodon; Mint etc.
The round, swollen part of the underground stem is called a bulb. Within the bulb lies the organ for vegetative propagation such as the central shoot that grows into a new plant. Bulbs have a bud surrounded by layers of fleshy leaves. A few examples include Onions, Garlic, and Tulips etc.
In plants like potatoes, stem tubers are found. This part is the swollen apical part containing many nodes or eyes. Every eye has buds. New plants originate from these buds.
Page 16 of 21 Strawberries produce an above-ground branch (shoot) with very tiny leaves. These almost- leafless branches are called stolons. These develop a tiny plantlet, the crown at the tip (apical bud). This crown grows and weighs down the end of the stolon. As the crown bends the stolon toward the earth, it accumulates auxin (because of the horizontal position) and roots begin to develop. When it touches down on the ground, the roots penetrate and root the crown into the soil.
Rhizomes are root-like stems that grow horizontally under the ground. New roots and shoots form at the nodes with shoots growing upwards to form new plantlets. Lateral buds grow out to form new rhizomes. Examples include iris and root ginger.
. By leaf
Vegetative propagation by leaves is when a leaf roots in water or soil. Either when a branch or stem is covered in soil or water or when a leaf is broken or cut off and deposited/planted in water or soil and allowed to root. A common example is with house plants like the green pathos.
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. Horticulture or Artificial Methods of Vegetative Propagation
This is a type of vegetative reproduction carried out by humans on the fields and laboratories. the most common types of vegetative reproduction occurring artificially include:
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. Cutting
In this, a part of a plant, specifically a stem or leaf is cut and planted in the soil. These cuttings are sometimes treated with hormones to induce root development. The new plant is formed from the adventitious roots developing from the cutting.
. Grafting
In this, the cutting from some other plant is attached to the stem of plant rooted in the ground. The tissues of the graft become integrated with the tissues of the rooted plant and develop as a single plant over time.
. Layering
Page 19 of 21 In this, the stem of the plant is bent to the ground and covered with soil. Adventitious roots emerge from the plant parts covered with the soil. This attached stem with developing roots is known as a layer.
. Tissue Culture/ Micropropagation
In this, the plant cells from different parts of a plant are cultured in the laboratory to develop a new plant. This technique is helpful in increasing the number of rare and endangered plant species that are unable to grow under natural conditions.
. Benefits of Artificial vegetative propagation The new plants produced by artificial vegetative propagation will be exactly like the parent plant. Any desirable features (like fruits, flowers, height, etc)of the parent plant will be replicated in the new plants. The fruit trees grown from seeds may take many years before they start to bear fruit. But the fruit trees grown from cuttings or by grafting start to bear fruits much earlier (only after a few growing seasons). The plants grown by vegetative propagation usually need less attention in their early years that the plants grown from seeds. Many plants can be grown from just one parent plant by artificial propagation. We can also get seedless plants by artificial propagation.
NCERT MATERIAL
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VIDEO-LINKS
LINK 1
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LINK 2
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LINK 3
https://youtu.be/TdiibRXXJ6g
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DOCUMENTS LINKS
https://schools.aglasem.com/18706
https://mycbseguide.com/blog/reproduction-organisms-class-12- notes-biology/
ASSIGNMENT
Q.1. What is vegetative propagation? Give two suitable examples.
Q.2. Why is vegetative reproduction also considered as a type of asexual reproduction?
MULTIPLE CHOICE QUESTION
Q.1. Which of the following cannot serve as vegetative propagule? a. A piece of potato tuber with eyes b. A middle piece of sugarcane internode c. A piece of ginger rhizome d. A marginal piece of Bryophyllum leaf
Q.2. It is a common method of vegetative propagation in which 20-30 cm long pieces of 1 year old stems are cut, their lower ends are dipped in root promoting hormones and are then planted in the soil which then develop adventitious roots. This method of vegetative propagation is performed in a. Rose and sugarcane b. Lemon and orange c. Begonia and bryophyllum d. All of these
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