LIFE PROCESSES-II Ca aa REPRODUCTION OBJECTIVE Studying (a) binary fission in Amoeba and (b) budding in yeast with the help of prepared slides, Rly MATERIALS REQUIRED Compound microscope, prepared slides of binary fission in Amoeba and budding in yeast and hydra. = THEORY Binary Fission. It is the process of asexual reproduction found in unicellular organisms such as amoeba, paramoecium and yeast. In this process, the parent cell divides to give rise to two daughter cells. Each daughter cell has a nucleus and gradually grows into an adult organism. During binary fission, the nuclear division takes place first, followed by the division of the parent cell cytoplasm. Thus, two daughter organisms are formed. The nuclear division is amitotical. le eet DAUGHTER ae 44 AMOEBAE INS A 8 c DIMISION oF NUCLEUS Fig. 12.1. Binary fission in amoeba, 122IMENTS — eit LYCOGEN ITOCHONDRION Fig. 12.2, One yeast cell (magnified) showing the nuclear vacuole. 1. Binary Fission in Amoeba. The nucleus of an adult Amoeba divides amitotically into two nuclei, It is followed by the appearance of a constriction in the cell membrane. It gradually deepens and divides the cytoplasm into two parts. Thus, forming two daughter Amoebae. . Budding in Yeast. In budding yeasts (Z)gosaccharomyces), a small protuberance appears on the upper part of an adult yeast cell. This gradually grows in size. The nucleus divides amitotically and one passes onto each outgrowth. The budding may be repeated resulting in the formation of one or more chains of bud cells. YEAST. CELL r) a (0)~ (@-(@) - A Fig. 12,9. Budding in yeast 3, Budding in Hydra. Budding is a mode of reproduction in which one or more organism develop from the body of an organism which then separate to form new individuals. Hydra multiples by budding under favourable condition.PROCEDURE Set-up a compound microscope. Observe the slides of Amoeba, Yeast and Hydra under com microscope, first under low power and then high power. Bs OBSERVATION Locate the different stages in each case. Compare the stages with the diagrams ory. Draw diagrams in your practical notebook and label them properly. Observe difference between budding (in yeast and hydra) and binary fission (in amoeba). gD INFERENCE Binary fission and budding are asexual methods of reproduction. PRECAUTIONS ota 1, Focus the slide under low power, Locate stage/stages by moving the slide very slowly : (left and right). Only then observe the slide under high power, ee 2. Always lower the lens of microscope very slowly and gradually, looking into eye piece. ii\_VIVA VOCE Q 1. What is asexual reproduction? Ans. In this type of fission, the parent m1 Ans. Asexual reproduction is the mode of divides several times to form reproduction in which a single parent daughter nuclei. The daughter n Produces two or more new individu arrange alone the «due Re Rt i) Qt Ans,LIFE PROCESSES — {1 re ee aaa ©) OBJECTIVE Identific i nuification of the different parts of an embryo of a dicot seed (pea, gram or red. hidney bean). n. [Rly MATERIALS REQUIRED Seeds (gram/pea/bean), beakers, water, needle, forceps, blade, slides, notebook, pencil, ete, wa THEORY Ww Seed is a matured fertilized ovule and is borne in a fruit. Seeds are the means of propagation and ontinuation of race, Seed encloses embryo within, which gives rise to a new plant. The seed may have e ie one cotyledon or two cotyledons and accordingly, the seeds are called as monocot and dicot seeds, Dicot Seed. Seeds like gram, pea, red kidney bean seeds have two food laden cotyledons but to not have endosperm, Seeds have seed-coats which consist of two layers or integuments. Outer cr is called tecta and the inner is called tegmen. They are provided with hilum (the point of achment with stalk), micropyle (a minute opening above the hilum) and raphe (a ridge formed lying within consists of an axis between two fleshy d of the axis is the radicle and the feathery the radicle gives rise to the root and the by the funicle or stalk in many seeds). Embryo pointed enc germination, cotyledons laden with food material. The or leafy end is the plumule. After the seed plumule to the shoot. TESTA RAPHE CHALAZA, HILUM ‘ YI Mae, RADICLE ‘gram seed (over arientum). RADICLE Fig. 15.1. Structure ofPRACTICAL SCIE eg 8 “ » ES f i u EA H fj R iN * ¢ mirooyle; 0, emboli Fig. 15:2. Poa seed (Pisum sativum). A, entre seed: B, seectcoat with hilum and 5: C, r of the seodcoa) and D, embry withthe co¥ledons uniolded. $, ssedcoattesa (tenses a ihn ‘mombraneus tegmen); M, micropye: H, hilum: R, radicle; C, cotyledons: F plumule. M S S H Fig. 15.3. Country bean seed (Dolichos lablab). M, micropyle; S, seed-coat; H, hilum; R, radicle; C, cotyledons; P. plumule. PROCEDURE by Take some dicot seed (say gram) and put them in water in a beaker for about 24 hour safe place. Select a well soaked seed and place it on a slide. 3. Make a slit in the seed coat using a blade and a forceps. Remove the seed coat consi testa and tegmen. Take care cotyledons are not damaged. 4, Add a drop of water and pull apart the two cotyledons with the help of fore observe. OBSERVATION Structure of gram seed (cicer arientum) (Dicot). Tt. is broad and rounded! aieteae pointed at the other. It is covered by a thick brownish coat called testa. There is a pore pointed end, known as micropyle. A little above the micropyle is an oval sear hilum ( the point of attachment with the seed stalk). From the hilum a ridge like structure runs up middle of testa towards the broad round end, known as raphe. A triangular patch called as occurs on the raphe, a little away from hilum. On removing testa, a white papery membrane ¢ seen and is known as tegmen. The embryo of seed consists of two fleshy cotyledons: reserved food material and are connected to a small axis called the axis of embryo. One e1 axis of embryo is pressed between the two cotyledons, and known as plumule while the o projects out of cotyledons at the pointed end and appears as a small pointed structure, radicle. 3JP mA A 8 c Oo ig, 15.4. Gram seed (Cicer arietenum). A, / ed-coat C. embryo with the cotyledons gail felotece of cieners beset oe raonee pe M, micropyle; C, cotyledons; F, radicle; and, pumule. = }y INFERENCE A seed of dicot angiospermic plant is covered with a seed coat which consists an outer and an inner er. Inside the seed coat two cotyledons are present which are attached to an embryonic axis. The ser leafy part, called plumule, remains pressed between the two cotyledons while the other pointed ¢ projects out of cotyledons known as radicle. PRECAUTIONS 1. Select only healthy seeds for the study. 2. Soak seeds properly in water. Place seeds at a safe place at least for 24 hours. 3. Do not allow the embryo—cotyledons, embryonic axis to get dry. 4. While dissecting the soaked seed, take care that cotyledons do not get damaged. VIVA VOCE Q. 1. Name the different parts of a carpel. Q. 6. Name two dicot seeds which do not have endosperm. Ans. Ovary, d stigma. se style and stigma. ‘Ans. Pea, gram/red kidney shaped beams. Q. 2. What is a seed botanically? ce eat te eee @. 7, Name two dicot seeds which have atan endosperm. ferif a fertilization. 2 ‘Ans. (i) Castor seed