 Yes, am I what able to you all? Good evening everyone. Good evening sir. Hello sir. Hello. Are we going good? Yes sir. Reading your textbook nicely because actually that is required the most if you will see that because they know everybody is not going to read the you can say biology at 11th standard. Okay. So need to understand that your textbook book is going to be the basis. So please read that. So just NCRT is enough. It is like see you will not be able to solve all the question but you will you will be able to solve you can say many questions. Okay, because if I will tell you that you have to do all the subject at 12th level 11th level that will not be possible that is not feasible actually agree because you people need to read other subject also. Yes, sir. So, you have to focus on the basics first. See, we are done with genetics now in the previous class. Here we will be discussing the cell biology. Cell is the structural and functional unit. Structural functional unit of life. Yes or no? Agreed? Everyone. You can add basic also in this definition. It is the basic structural and functional unit of life. Yes or no? Everyone. Yes, sir. Yes. It is there. What happens like your your room is there in the room there are two you can say bricks are there. Yes or no? Bricks brick is also a structural unit like what is the structure structure is the wall and wall is made up of which structure? The bricks. Bricks. So brick is the unit of structure as well as function like the function of wall is to stop the wind or sunlight or something. In that case, what happens? In that case, what happens? Tell me. It is the part of function also. No issues. I will say over here a few things. Robert Brown discovered nucleus. First we will see the cell. Discovered cell. Robert Hook was the name of scientist. Robert Brown as you can say discovered nucleus. Robert Hook discovered a dead cell. The 1665. Agreed? Next thing I will tell you and that cell was what? Dead cell. Okay. I will say over here that Leuvenhoek. Leuvenhoek discovered first living cell in 1674. What? In 1674. Next discovery was Robert Brown discovered nucleus in 1831. No issues? No issues? Let's see. Straight away I would like to start from here the cell theory. Cell theories. What? Rudolf Virchow. Can you people see the screen? Rudolf Virchow. He told omniscellular E cellula. Agreed dear? What is omniscellular E cellula? Means all the cells are getting formed from you can say pre-existing cell. That was known as modern cell theory. What was modern cell theory? If you will talk about modern cell theory, this is given by Rudolf Virchow himself. Am I available to you people? Yes sir. Rudolf Virchow only what he told first. Actually he has modified the original cell theory given by Sliden and so on. Agreed? Modern cell theory was given by Rudolf Virchow. I will talk about this like this is the modified form of this cell theory given by Sliden and so on. I will say the cell is the basic structural functional unit of life. Agreed? And all organisms are composed of cells. Let's see. Second thing is over here all the cells are produced by division of pre-existing cells. Here all basic chemical and physiological functions are carried out by cells and all. So you people will see this thing. Please see to it. Agreed? See over here. Straight way I would like to talk about types of cells. I would like to talk types of cells. There are two kind of cells and they are karyotic cells, two karyotic cells. Let's see. It is on the basis of presence of nucleus and other membrane bound structures. Okay. And eukaryotic cell on the basis of presence or absence of on the basis of absence of on the basis of presence or absence of cell wall. It is plant cells and animal cells. Agreed? No issues? Other things are also there in consideration. Everyone agrees to this point? Yes sir. No issues? Now, first read out some of the structures of prokaryotic and eukaryotic cell. Plant cell as well as animal cell. Then we will make some table, one table or two table to get to know about all these things. I will talk about prokaryotic cell. What? Agreed? Prokaryotic cells. What is there in this? Let's see. What is there in this? Let's see. I will say over here. Prokaryotic cell is going to lack the nuclear membrane and other membrane bound organally. Agreed? And other membrane bound organally. Yes or no? Like mitochondria, like mitochondria, chloroplast, etc. Agreed here? See what all structures are there in prokaryotic cell? What all structures are there in prokaryotic cell? You people can observe. Please observe. You people can observe over here. Observe for a minute. I am going to tell you. Observed? Do you people know any of the membrane? Let's see. One thing is flagella. You all can see over here. One thing is flagella. Flagella is there for locomotion. You all can see the cell wall. This structure. Can you see? It is a rigid structure outside plasma membrane. Okay. Let's see. Inside the cell wall. This inner one. Outside is cell wall and then inner one is known as plasma membrane. What? Plasma membrane. It is the membrane enclosing the site of plasma. Okay. There are many ribosomes that are going to synthesize proteins. And what is the nucleus or bacteria is known as? Nucleoid. Agreed? There are structures known as fimbri, which is therefore attachment. Can you people observe? Ribosome is 70s type in prokaryotic cell. We will discuss that. Ribosome is the cell organelle which is present in prokaryotic as well as eukaryotic cell. Yes or no? Yes, sir. Yes or no? Please observe. Rest will be there in the difference part. Agreed? Yes, sir. Please see to it. Now, one typical animal cell. Please see to this. Please see to this. Let's see. What I want to tell you all? The plasma membrane is there in place. Can you see over here? So plasma membrane is another structure which is present in prokaryotic as well as eukaryotic cell. Yes or no? Yes, sir. Here is nucleus also. Nuclear membrane. Can you see this structure? This one? It is a nuclear membrane. Agreed? You all can observe. There are many pores inside the nuclear membrane. These pores are known as nuclear pore. What? Nuclear pore. Agreed? This structure inside is known as nucleolus. What? Nucleolus. Can you see this densest area in between in the center? Yes, sir. Can you all see? Nuclear pore. What is the function of nuclear pore? Can you explain it to me? Exchange of material between nucleus and cytoplasm. Yes, it is responsible for exchange of material between nucleus and cytoplasm. Let's see. I will say over here exchange of material between nucleus and cytoplasm. Agreed? Now you can see there are many filament like a structure radiating from nucleus. Many filament like a structure radiating from nucleus. Like this. Can you observe? What are they? They are chromatin fibers. What? Can you observe them? Because in the real diagram you are going to see like that only. Is it there? It is the nuclear double membrane enclosing the nucleus perforated by pores. Okay, that I have told you. Nucleolus. You people are getting or not? I am not able to understand. Yes, sir. Say yes or no. See over here. Nucleolus is a non-membrane structure. It is non-membrane bound structure involved in production of ribosomes. A nucleus has one or more nuclei. Agreed everyone? Are we done? And you can see on the surface nuclear pores are evident. Can you observe? Can you observe? Yes, sir. Agreed? Now, here is flagellum. It is the motility structure present in some animal cells. It is composed of a cluster of microtubules within an extension of plasma membrane. Agreed? Motility structure present in some animal cells composed of a cluster of microtubules within an extension of the plasma membrane. Yes or no? Everyone? Now, can you see in continuation with the nuclear membrane there are many? What are they? What are they? They are endoplasmic reticulum. You can observe. See, there are dots present on their membrane. That is rough endoplasmic reticulum. Yes or no? And they are a smooth endoplasmic reticulum. Agreed? Everyone? They are a smooth endoplasmic reticulum. Agreed, everyone? Tell me, dear. Can you people observe over here? Endoplasmic reticulum is a network of membranes, sacs and tubes active in membrane synthesis and other synthetic and metabolic process has rough ribosome studied and a smooth regions. It is there for ribosome. Endoplasmic reticulum. What is the, you can say function of a smooth endoplasmic reticulum? Lipid synthesis and its function is protein synthesis. Yes or no? Rough endoplasmic reticulum. Everyone? Agreed, everyone? If ribosome is there, that means? Rough. Now, you can see here is evolving a flagella. It is originating from below the membrane and it is going out. Yes or no? So, we have studied nucleus. In that nuclear envelope, nuclear pore, nucleolus, chromatin fiber. Chromatin, DNA is in the form of chromatin fiber over here. Then flagellum. Then centrosome, you can see over here. Isn't it? Centrosome. Can you see? Centrosome is there at this place? Is it visible here? Yes, sir. Yes, sir. What is the difference between centrosome and centriole? You can observe here. One centriole is there, another centriole is there. They are perpendicular to each other. Yes or no? They are perpendicular to each other. Agreed? Yes, sir. They are perpendicular to each other. Agreed? Yes, sir. See, this is paroxysome. Paroxysome. It is the organelle which you can say it is going to produce or perform a release hydrogen peroxide. Agreed, dear? Agreed, everyone? Now, so we have done nucleus, rough and smooth adenoplasmic reticulum. We have done centrosome. It is having role in cell division. There are two centrioles arranged to each other at 90 degree to form centrosome. Yes or no? Everyone? Everyone? Yes, sir. Just a minute, dear. I am a little busy now. I will call you at 8 o'clock. Agreed? You got it? Now you can observe mitochondria over here. Is it there? It is the seat of aerobic respiration, cellular respiration. There are two key processes that is going to run in mitochondria. You can say crepes cycle is there. Crepes cycle is going to run in mitochondria. Agreed, dear? This structure is microvilli. Microvilli is going to increase the cell surface area that we have done in digestion as well. Agreed, dear? We will repeat that. Now, cytoskeleton. You see, what is a skeleton? What is the meaning of a skeletal system? Tell me. It is going to form peroxide and all. There are many enzymes that are peroxidase and all. And peroxysome is involved in, you can say, photo respiration. Time will permit. I will discuss with you people later on in plant cell. Let's see. What I want to tell you all? Let's see. Cytoskeleton. What is a skeleton? It is going to reinforce the cell, meaning maintaining the shape of the cell. There are micro filament, intermediate filament and microtubules. Nothing. They are proteinaceous in nature and they are having only difference in diameter. Yes or no? They are having difference in diameter. Agreed, dear? Agreed? Yes, sir. Done. So, we are done with nucleus. In nucleus, we are done with nuclear envelope, nucleolus, chromatin, fibers. Yes or no? We are done with rough and smooth endoplasmic reticulum. We are done with peroxysome. Mitochondria, we are going to learn now. Microvilli, have we discussed? In GIT, increased surface area, microtubules, micro filament and intermediate filament are the part of cytoskeleton which is going to reinforce the cell shape or not. Which is going to reinforce the cell shape? Yes or no? And now, centrosome. Centrosome is the region where the cells, microtubules are initiated and it contains a centriole. Yes or no? Regions where the cells, microtubules are initiated? Getting my point. Contains a pair of centrioles. Ester ray formation will take place later on during the cell division. It is having role in cell division, everyone. Now, one more important structure is lysosome. It contains, actually it contains many hydrolytic enzymes. If it will burst, it will digest the cell. Because of that, it is known as suicidal bag of cell. What is the meaning of hydrolytic enzyme here? What is the process of hydrolysis? Let me know that first. Hydrolysis. What is the meaning of hydrolysis? Tell me. Breaking of water into hydrogen and oxygen? No, no. See, if you will see in biomolecule, in proteins, in carbohydrate, everywhere, the bond is formed due to dehydration. Because of what process? Dehydration. Agree, dear? Bond is formed due to dehydration because of loss of water. Then how? If some bond is going to be formed because of loss of water, will it break by addition of water? Tell me. If some bond is, yes, formation due to loss of water, then it will break due to addition of water. It is the breaking of bond in presence of water. Agree, dear? It is the breaking of bond in presence of water. Agree, dear? It is hydrolysis. Noisos? Noisos? Yes, sir. Nan, hydrolysis is the breaking of bond in presence of water. Please see to it. Noisos, lysosome. So that is all those enzymes that are going to bring about hydrolysis, they will be known as hydrolytic enzyme. Like all the digestive enzymes are what? Hydrolytic enzyme. Agree, dear? Agree it or not? Tell me that. Yes. Only few are going to agree. Let's see. What I am saying? Here, the green color structure. This is Golgi apparatus. What? It is the organally active in synthesis, modification, sorting, and secretion of cell product. It is the packaging center. Anything that is going to be secreted from the cell will be coming to this phase and through this phase it will be released outside by formation of vesicles. So Golgi apparatus is going to perform all the, you can say, going to perform all the packaging for the substances which are going to be secreted outside the cell. Agree, dear? Everyone? Yes, sir. If something has to be secreted, if something has to be secreted, it will be formed from, it will be formed inside which cell organelle? Golgi apparatus. Golgi apparatus. Now ribosome. It is a small brown dots complexes that makes protein. It is the protein factory of the cell. What? Protein factory of the cell. In eukaryotic, it is ATS type of, ATS type of, you can say, ribosome. Agree, dear? Do you people have any problem in nucleus? Do you people have any problem in endoplasmic reticulum? The rough endoplasmic reticulum is going to contain, is going to contain what? Ribosomes. Ribosomes. It is going to contain ribosomes. Agreed? No issues? And a smooth endoplasmic reticulum to not have ribosome. So it is responsible for lipid synthesis. Can you people explain me the function of nucleolus? Can you people explain me the function of nucleolus? Production of ribosomes. Production of ribosomes. Which is the structure that is responsible for microtubule formation during cell division? Tell me. Centrosome. Yes. Yes, centrosome. It is the reason where the cells, microtubules are initiated and it contains a pair of centrioles. How many centrioles are there? Two. Are they, are they situated at right angle? Are they situated at right angle? Yes, sir. Everyone. Which is the protein factory of the cell? Which is the protein factory of the cell? Ribosomes. Ribosome. Packaging center of the cell? Golgi apparatus. Golgi apparatus. No issues? What is the role of cytoskeleton to reinforce the shape of the cell? Agreed? And, and, and what is the function of microvilli to increase the surface area? Yes or no? Everyone. Do you people have any doubt in this? Let's see. Dear, this is your plant cell. This is your plant cell. Rest we will discuss in the next section, common section. Let's see. The first thing that you people can observe in a plant that is a large central vacuole. What? A large central vacuole. No issues? No issues? You can say vacuole of this kind or this dimension is absent in, is absent in what? Animal cells. Animal cells. Agreed, dear? Everyone. Now, this is the nucleus. Similar will be, things will be there. With endoplasmic reticulum, similar things will be there. With Golgi apparatus, similar things will be there. With nucleus, similar thing will be there. One addition, mitochondria is similar, peroxidome is similar, everything is similar. Only one thing is extra over here that you people need to see is cytoskeleton is also. Although cytoskeleton is not that important in plant cell because it is having cell wall. Yes or no? Everyone. Everyone. But it's still there, sir. It is there. It may be there. They are nothing. They are a proteinaceous thing. Okay, this diagram I have taken from Campbell and Reese. So these books have to be followed. Getting my point? Let's see. What have I told you people? What have I told you people? This is a structure known as chloroplast. What? Chloroplast. Chloroplast. This is plasma membrane and outside plasma membrane you can see one more covering that is known as, that is known as what? Cell wall. What? Cell wall. Cell wall. Cell wall. Agree everyone? Agree everyone? One additional thing that is there in, let's see. See, I'm going to make one plant cell over here. This is one plant cell. It is the plasma membrane. Outside the plasma membrane is the cell wall. Is the cell wall? Do people know what is this? Yes, cell wall. Another cell wall. In between there are certain things that is known as middle lamella. What? Middle lamella. Have you heard about this? Middle lamella. Made up of calcium pactate. Agree? This is the cell wall. Now the plasma membrane. Let's see. Here, one communication is going to be developed. A pipe-like communication is going to develop. Agree everyone? A pipe-like communication is going to develop over here and that communication is going to be known as plasmo-desmata. What is this? What is this? Plasmo. Okay. I have muted myself. Am I audible now? I am saying, do you people, you can say, while I was discussing plasmo-desmata, are people there? Sir, you just labeled plasmo-desmata and then... See, what is the function? It helps in cell-to-cell communication in plant cell. What is there in animal cell? In animal cell, there is gap junction. In animal cell, animal cell, there is a corresponding structure. Gap junction helps in cell-to-cell communication. Agreed? No issues? Done, dear? Done? Yes, sir. Central vacuole is a prominent organelle in olden plant. Okay? You will see over here. It helps in storage, actually. It is the storeroom of the plant cell. Yes or no? Everyone? Now? Done? Have you people understood? Now we will discuss few cell organelles. Agree, everyone? First is plasma membrane. Let's see. First is plasma membrane. To describe the structure, you will know that plasma membrane is quasi-fluid, semi-fluid. And it is like protein, iceberg in the sea of lipids. Can you see? See. This is the lipid part which is going to form the plasma membrane. This is the polar head. This is non-polar tail. Agreed, dear? Now you see. Polar means it is hydrophilic. Polar means it is hydrophilic. And tail means hydrophobic. Agreed? Done, dear? No issues? Now? Now you see. What I want to tell you all? What I want to tell you all? It is going to form a bilayer. A lipid bilayer. Yes or no? This is a lipid bilayer. Agreed? You can see. This is a lipid bilayer. No issues? Head from both the sides is going to face the water and tail is going to be embedded inside. Agreed, dear? Agreed? So you can see. This part is hydrophobic. And this head is hydrophilic. Agreed? Everyone? The central part is hydrophobic. Yes or no? Everyone? Say yes or no? Yes. The head is hydrophilic, right? Tail is hydrophobic. Non-polar thing is hydrophobic because water is a polar molecule. And you have to follow the principle of like, dissolve, like. Yes or no? Yes, sir. No. You see. This is the plasma membrane. And this is the protein molecule. You see. Protein to protein molecule is of two types. This protein molecule is the integral protein. And there are many peripheral protein. Peripheral protein are situated in the superficial side. And transmembrane protein or tunnel protein that is there. It starts from one side. It starts from one side and it reaches the another side. Yes or no? This is known as integral protein. What? Integral protein. Protein. Getting my point? It act like channel. What? It act like channel. It act like a channel. Agreed? It act like a channel. And this is sugar. Sugar. This is sugar. It is present on the surface. Agreed, everyone? So, you have understood. And this model is given by, fluid mozak model was given by a scientist. Mozak model is given by Singer and Nicholson. What? Singer and Nicholson. Agreed? Noisos. So, it says protein icebergs in the sea of lipid. You can see over here. Do you people have any doubt in this? There are many others but you need to know this only. This is your chloroplast. What? This is your chloroplast. Agreed? You can say they contain a green color pigment chlorophyll. You can see what happens. What happens? See. This area. Can you see? It looks like many coins are kept on one another. Can you see it like that? Many coins are kept on one another. Can I say that? This region is known as graina. What? Graina. Agreed? One coin is known as thylakoid. One coin is known as thylakoid. Agreed? You can say connecting to graina is known as stroma lamellae. They are the structure which is interconnected to each other. And you see this area between them. This area between them is known as, this area between them is known as what? The stroma. The stroma. Yes or no? Say yes or no? Sir, what is the graina again? Graina? Yes, sir. What is graina? Let's see. Graina is the reason where, see. Observe this thing. This is one thylakoid. This is one thylakoid. Many thylakoids are kept on each other like this to form a region known as graina. Yes, actually how they are connected? I'm going to tell you. See. See. Actually, they are connected like this. They are connected like this. Can you see? See. This is one thylakoid. This is another thylakoid. This is another thylakoid. They all are thylakoid. And what is this? This is a stroma lamellae or a granule thylakoid. This is a stroma lamellae or a granule thylakoid. And you can see they all are granule thylakoid. If I will talk about this, this is a granule thylakoid. Agree, dear? A stroma lamellae or a granule thylakoid are the same. And you can see they all are connected. You can see they all are connected. So a stroma is there and all. A stroma is the seat of dark reaction. We will discuss this thing. Please read it nicely. One more thing. DNA is there in the nucleus usually. But DNA and 70s, 70s type of ribosome is present in mitocondria and chloroplast. Agree, dear? Agree, everyone? No issues? No issues? Tell me, everyone? Significance everywhere it is there for protein synthesis only. Hence this organelle is also known as semi-autonomous organelle. Which organelle? Semi-autonomous. Now I am taking one more photograph. That is of mitocondria. This is known as mitocondria. Let's see. This is known as mitocondria. Let's see. Have you understood this? Mitocondria. It is another double membrane-bound structure. How many double membrane-bound structures that I have told you people? One is the chloroplast. It is having two membranes. One is outer and one is inner. One is chloroplast. One is the outer membrane and another is the inner membrane. Agree? Here mitocondria. Mitocondria have two types of membrane. Outer and inner. Outer and inner. Agree? And between the membrane, this space is known as this space that you people can see. Can you see this space? Between the two membranes, can you see this space? These spaces? They are known as intermembrane space. Can you see this finger-like projection that is present in the mitocondria inner membrane? Known as Krista. Projections formed from inner membrane. Agree? And bound by inner membrane, this is the mitocondrial matrix. This is the mitocondrial matrix. Yes or no? So how many double membrane-bound structures that you people know? It is nucleus. Let me take the attendance otherwise I will forget. It is a nucleus. It is a mitocondria and it is done, everyone. Are we done? Say yes or no? Just a minute. Can you observe the mitocondria and all? Okay, mitocondria, chloroplast and all. Can you observe these structures? Please observe. Krista is going to increase the surface area in this case. Anybody having doubt? Chloroplast is known as kitchen of the cell. What? Kitchen of the cell. No issues. If you will see, rather I should use the word plastid over here. I should use the word plastid first. Okay, or let me make some space so that I can adjust things. Let's sit here. I will write like plastids over here. What? Plastids. Actually, plastids are of two types. Plastids are of three types rather. Let us read all the three. Okay. One is leukoplast. Another is chromoplast. Okay. One more is chloroplast. Read. One is leukoplast. One is chromoplast and another is chloroplast. Leukoplast is a colorless plastid. What? It is of three types. One is it is there for a storage. It is alluroplast. It is ilioplast. Okay. One is amyloplast. Alluroplast is going to store protein. Allioplast is going to store fats. It is going to store carbohydrates. Chloroplast is going to is going to contain pigments other than chlorophyll and chloroplast is going to contain fill. Agreed? No issues? Everyone? You people can read rest of the structures as it is. We will be discussing cell division now. Are we there? Yes. We will be discussing cell division now. You all know cell division is of two types. One is mitosis, another is meiosis. No issues? Everyone? Phases of cell cycle. Okay. What is cell cycle first? Cell cycle is the sequence of event by which cell duplicates its genome. Duplicates its genome, synthesize the other constraint of the cell and eventually divide into two daughter cells. Two daughter cells is termed cell cycle. Agreed? No issues? The sequence of event by which a cell duplicates its genome, synthesize the other constraint of the cell and eventually divide into two daughter cell is termed cell cycle. Now, it is, if you will talk about duration, if you will talk about duration, cell cycle varies from organism to organism. This yeast is going to, you can say, perform the cell cycle in 90 minutes only. And the human cell it is 24 hours. In that mitosis or meiosis, the phase containing mitosis, either mitosis or meiosis, not both. It is either mitosis or meiosis. That is only one hour and interface is going to contain 23 hours. So which is going to be the, which is going to be the longest phase in this case? Is it, is it interface? The cell is there in interface most of the time if I would like to tell you. Agreed? Everyone? Now, now, mitosis. Actually, your M phase is going to, you can say, consists of two phases. One is karyokinosis, one is cytokinosis. Karyokinosis, it is the division of nucleus and cytokinosis is division of cytoplasm. Karyokinosis is division of nucleus and cytokinosis is the division of cytoplasm. Agreed? No issues? Now, we'll talk about mitosis. Karyokinosis. Do you people know a structure of, you can say, structure of DNA? Do you people know that? What happened? It stopped just a minute, just a minute here, just a minute. My screen building has stopped. Yes. Let's see. Let's see here. Human cell, 24 hours, it is M phase and interface. M phase is consisting of karyokinosis and cytokinosis. Am I audible to you? Just a minute. Just a minute. Let's see. What I want to tell you all, the duration of cell cycle varies from organism to organism and all. After that, do you people know what is the structure of DNA? Am I audible to you? Yes. See, it is like chromatin fiber like this. Chromatin fiber like this. This is one. Okay. So, one chromatin fiber will condense. It will form one chromatid. What? Chromatid. It is the centromere. It is one chromatid and these are the two arms. These are the two arms. This is the short arm. This is the long arm. This is the short arm. This is the long arm. Yes or no? So, this is one chromatid. Now see. In S phase, what happens? S phase, everyone. This is one chromatid. Another one is formed like this. This is one. Two chromatids are there. Now you see. After S phase, your nucleus is going to, after condensation, you can say your chromosome is going to be formed like this. Yes or no? Just a minute. Let me make with another color. Let's see. Do you know? They are known as sister chromatids. What? Sister chromatids. What? So, sister chromatids. This is a, you can say, this is the structure that is known as a chromosome after S phase. Before S phase, it is like this. This is a chromosome with one chromatid. This is a chromosome with two chromatids. And you all know that you people are diploid organisms. Yes or no? And we all are there. We are diploid organisms. Agreed? So, we have a pair of similar chromosomes. We have a pair of similar chromosomes. And they are known as what? Homologous zone. They are known as homologous chromosome. Noisos. And if I will talk like, talk about them, talk about them like this and this. Do you know what are they? This and this. They are known, sorry, non-sister chromatids of homologous chromosome. Yes or no? Have you people understood the difference between sister and non-sister chromatids? If you will understand that, then only you are going to get, this is the centromere. But then only you will understand the cell division properly. Have you understood this thing? For you, for us, for me, for everyone, which is a diploid organism, getting my point. There is a similar set of chromosomes. You can say two similar chromosomes are there. They are known as homologous chromosomes. Agreed? Everyone? Before S phase, it is there. In S phase, only DNA doubles. DNA doubles. In S phase only. Agreed? Noisos? Noisos? Everyone? So, here the growth phase. You can say interphase consists of three phases and they are growth phase, S phase and G2 phase. The growth phase, the S phase and G2 phase. Agreed? Growth phase, one is G1 phase and one is this is growth one phase. In this phase, actually, cell is preparing itself for what? Preparing itself for what? Division. So, you see over here, the cell growth occurs in this place. Cell is metabolically very active. Cell continuously grows, mitochondria, chloroplast, etc. are produced. Structural and functional proteins are formed. Neucleolus produces RNA and messenger RNA. Means, cell is trying to accumulate everything for what? Cell division. Now, you see, what is this? See here, how many DNA you can look for? 1, 2, 3 and 4. Agreed, dear? How many DNAs are there? 1, 2, 3, 4. DNA content is 4N. Number of chromosome is 4 also. Okay, only 4 chromosome and DNA content is 4N only. Let's see. One thing. Here you see, how many chromosomes you can see in S phase? How many chromosomes you can see and how many DNAs there? DNA content is there? How many chromosomes are there? How many chromosomes are there? 4 chromosomes and 8 DNA content. Means, you can see in S phase, the DNA doubles itself. Agreed? Everyone? Everyone? Yes. Now, G2 phase. See, in S phase, replication of DNA takes place. Stones are synthesized and Centrosome replicates in late S phase. Now only I have told you people about the Centrosome. In G2 phase, ATP is formed and all. Now, this cell is ready to enter the M phase. What? Enter the M phase. M phase is divided into prophase, metaphase, anaphase and telophase. You all can say early prophase, late prophase. You see, I have told you the condensation process. Can you people see or observe condensation happening over here? Can you people see condensation happening over here? It is the initial condensation, initiation of condensation. Here, the centriole has started moving towards the opposite pole and initiation of mitotic and spinel, the microtubules. You see, initiation of assembly of microtubules. Now, late prophase. Do not show Golgi complexes, endoplasmic reticulum, nucleolus and nuclear envelope. You see, nuclear envelope has started dissolving over here. Noisos and condensation is taking place continuously and Centrosome has moved to opposite pole. Yes or no, everyone? Yes or no? Here you see, tubulin protein synthesis. This protein is going to work over here. Now see, what happens? Late prophase. Do not show Golgi complex, endoplasmic reticulum, nucleolus and nuclear envelope. Means they all are dissolved in the cytoplasmic, agreed? Because now cell has stored enough for the division, it do not require any ATP, nothing from outside now. It will first divide, then it will reform everything now. You people can see, these cells started, these chromosomes, they are homologous pair of chromosomes. They are homologous pair of chromosomes. Agreed here? Homologous pair of chromosomes. They started arranging themselves on equator. Equator is this plane, center of the cell. Equator is the center of the cell. Agreed? Now, transition to metaphase. You can see, chromosome is arranging itself to equator. chromosome is arranging itself to equator. chromosome is arranging itself to equator. This is the centrosome. Here you see, this is the spindle fiber. This is the equatorial plate. Can you see, it is a chromosome with two chromatids now, attached to each other at centromere, attached to each other at centromere. Yes or no? Everyone? Say yes or no? Yes sir. Yes. Now see, what will happen? It will be pulled like this, and the chromosome is going to break from here, will break from here. One chromatid will move to this pole, another chromatid will move to this pole. Yes or no? One chromatid will move to this pole, another chromatid will move to this pole. Yes or no? And here, complete disintegration of nuclear envelope marks the start of metaphase. Once nuclear envelope is completely dissolved, you see, you can study the morphology of chromosome best in the metaphase. Yes or no? And all the chromosomes has aligned themselves on equatorial plate. All the chromosomes has aligned themselves on equatorial plate. Yes or no? Which one dear? This one. You people can ask me, because I do not see chat very frequently. It will be done. Let me know. Done everyone? Let's see. Let's see. I will say, it is the transition to metaphase. This is metaphase. Complete disintegration of nuclear membrane. Now, these things are done. Now you see, they have broken from the center, and now they have started moving. Now, they are one chromosome, no more chromatids. They are chromosome with one chromatid. They are chromosome with one chromatid. So you can see, what is the number of chromosomes in the metaphase? Is it 8? And DNA content is also 8n. Naphase, each chromosome arranged at the metaphase is split simultaneously. Centromere at the leading edge, you see, if you will pull anything, centromere will lead and arms is going to lag behind. And approximately 30 ATP are required to carry a chromosome to pull. Cytokinesis starts at Naphase. Now cytokinesis, division of cell wall. You see, in the animal cell, what happens? A furrow get formed. See, a depression is getting formed over here. It is forming, and eventually it will form two cells. Because in animal cells, what happens? Cell wall is not there. So cytokinesis takes place by furrow formation. All the things will reverse. That has dissolved. Now, in animal cell, it happens like this. In centripetal order, it starts from the outside and reaches center. And in plant, it starts from the center and reaches outside by, you can say, cell pregmoplast or cell plate formation. You can see, there are pipes over here. They are known as, these pipes are known as plasmo-desmata. These pipes are known as plasmo-desmata. Agreed? And somebody will ask you, cytokinesis starts in which phase? I will say, late Naphase. Agreed? Done, everyone? Done, everyone? Do people have any doubt? Yes, I can go up. This one here? Done? If done with this, please let me know. If done with this, please let me know. Done, everyone? Yes. Now, I will talk about, are you done about this? This one, please read all these things. Done? Tell me, dear. Now, meiosis. Meiosis is consisting of prophase. Likely, it is there. The only meiosis is, first meiosis is divided into two phases. Meiosis one and meiosis two. Meiosis one is the reductional division. Meiosis two is similar to what? Just a minute. Meiosis is divided into two. It is known as a reductional division. Division. Because it makes two N, two N. It makes two N, two N. A deployed cell will become haploid after this. A deployed cell will become haploid after this. Agreed, dear? Now, meiosis is divided into two parts. One is meiosis one. Another is meiosis one and meiosis two. Done. Meiosis one is actually, it is actually a reductional division. Only this is going to make a deployed cell. Cell, a haploid cell. Done. Yes. Meiosis two is similar to mitosis. Now, meiosis one. Meiosis one is going to have five stages. The meiosis one, prophase. prophase one is the, is for meiosis one. See, lepto-teen, gygo-teen, pectine, diplo-teen and dikinesis. Lepto-teen, in lepto-teen, chromosome become gradually visible under light microscope. See, the similar thing is there. Propase is there. So, it will condense. Chromosome is going to condense. So, it will become gradually visible under light microscope. Lepto-teen. Gygo-teen is there. You see. What happened? These, this is a chromosome. This is another chromatin. This is one chromosome and here is another chromosome. Let's see. What happens between them? Certain synapto-nemal complexes are, are formed. Done. And this is known as synapses. Okay. And you can say the chromosome that is going to, now you tell me this blue one and this black one. Are sister chromatids or non-sister chromatids? Are they sister chromatids or non-sister chromatids? Please let me know. Non-sister. They are non-sister chromatids. So, if I will ask over here that synapses is going to occur between, occur between non-sister chromatids of homologous pair of chromosome. Agreed? This is the gygo, gygo-teen. So, gygo-teen is characterized by formation of synapto-nemal complex. And this chromosome is known as bivalent, bivalent or tetrad. This chromosome is known as bivalent or tetrad. Bivalent or tetrad are in, you know, if you will see over here, here they will look like two. And in the next state, you can say, a stress they will separate and all the four chromatids will be visible and it will look like tetrad. Agreed here? No issues. So, chromosome starts pairing together. This is known as synapses. No issues. Gygo-teen, now. Packeting. So, if somebody will ask you, what is the characteristic of gygo-teen, what will you say? It is characterized by formation of synapses or synapto-nemal complex. Yes or no? And bivalent. Now you see, if you have 46 chromosomes, how many bivalents are there in this? How many bivalents are there in this? Let's see. Packeting. In packaging, what is going to happen? Let's see. I will see. Where they are fused? At that place only, there are, there is certain exchange of genetic material is going to take place. Agreed? Agreed here? Done. Done. Now you see over here. In packaging, tetrad will be visible and here, certain recombination nodules are formed and genetic material is going to be exchanged. How you see? That genetic material will be exchanged between what? Non-syster chromatids of homologous chromosome. Yes or no? Agreed? That is known as crossing over. So, crossing over takes place in packaging. Okay. Now, diplotene. This synapto-nemal complex that is formed will dissolve, but it will remain attached at certain places. It will remain attached at certain places. Like, see, this kind of a structure will be formed. This accept structure will be formed. This is known as chaismata. This is known as chaismata. Okay? Chaismata. Getting my point? So, formation of chaismata is going to take place in diplotene. Means, synapto-nemal complex will separate from everywhere apart from some area that is going to form chaismata. Now, dikinesis is the final stage in which chaismata will be terminated. Okay? Then, now meiosis 2. Meiosis 1 metaphase, sorry. You can see. These are the homologous chromosomes. Pair is formed over here. And you see, each of them is moving towards opposite pole, like this. So? Yes. So, what about dikinesis? Dikinesis? Chaismata will be terminated. Yes or no? Chaismata will be terminated and all these things are getting to be there on the equator. Now, you see, metaphase 1. All the homologous chromosomes are bivalent equatorial. Now, see, they are moving on opposite. Can you see homologous pair are getting separated? Can you see any division of centromere is there? Can you see any division of centromere in metaphase 1? So, can I say that centromere division is not going to take place in metaphase 1? Agreed? Done? Done? Agreed? Say yes or no. Centromere division is taking place or not? What happened? Now, in phase 1, homologous pair get separated. And two of them are formed. Interkinesis is a small phase between meiosis 1 and meiosis 2. And now, what will take place? The meiosis 2 part. Agreed here? The meiosis 2 part. Meiosis 2 is exactly similar to mitosis only. Agreed here? So, is the division of centromere is going to take place in meiosis 1? Done, everyone? Sir, we can't see the notes screen. Yes. Done? Yes or no? Are we done? Done? Are we done here? Tell me. Yes, sir. Done here? Agreed? Let's see. Few more things. Like, ecology. Let's see. Ecology. What is this? What do you understand? What is ecology? Ecology is the scientific study of interaction between organism and environment. I will say, is the scientific study of the interactions between organism, their environment. Done? Let's see. Actually, your environment is going to have environment having two components. Component. One is abiotic. Another is biotic component. Agreed? Abiotic component that is non-living. Like light, temperature, water. And biotic component is going to involve organisms. Agreed? Now we will define population. Agreed? It is a group of individuals. Group of individuals. Agreed? Of the same species. Of the same species living in a particular area. It is a population. Another definition is for community. What a community is, it consists of all the organisms, of all the species that inhibit a particular area. Agreed? Then ecosystem, the biosphere. Getting my point. All these definitions, you people, please go and search for them. Okay. And try to read your. Getting my point. What is a wetland? What is a coral reef? Everything you try to read. Okay. We will be discussing it in the next class. Read here. Bye everyone.