[Music] to start today's episode these are the five wonder tips for you to remember to keep your back neck and eyes healthy while indulging in some screen time this is teacher melvin's healthy tips for everyone number one sit properly so you are well supported your back should be touching the chair back rest number two change your position regularly if you are watching for long periods take turns sitting on the couch chair or floor number three keep dim lighting on in the room rather than no lighting strong or no lighting may lead to eye damage over time number four stretch use commercial breaks to change positions to get up and walk around and to do gentle stretches number five don't watch tv in bed as this often leads to neck and back ache there you are now ready to begin [Music] hello senior high school stem learners welcome to our biology class where learning never stops and the adventure never ends so buckle up and get ready to power your mind teacher melvin and this is wonder science [Music] [Music] have you ever seen a caterpillar turn into a butterfly if your answer is yes you are probably familiar with the idea of a life cycle butterflies go through a spectacular life cycle transition turning from something that looks like a worm into a pupa and finally into a beautiful creature that floats on the breeze a life cycle is a series of developmental steps that an individual goes through from the time it is born and to the time it reproduces the cell cycle can be thought of as the life cycle of a cell what is cell cycle [Music] does it ring a bell for today's episode we will learn more about the cell cycle and why it is thought as a life cycle of a cell are you ready to begin our learning exploration let's have a short game for this activity you will need the following materials a pencil and a piece of paper do you have the materials now if so let's begin here are the mechanics of the game first i will show you five words with jumbled letters in them second quickly and jumble letter combinations to form the correct word arrange the letters as fast as you can because you are only given 60 seconds when you hear the sound that means time is up for every correct answer a wonder badge will be given to you collect all five to get your first wonder gold medal get ready because the game will begin in three two one go [Music] few [Music] [Music] [Music] done is up let's check your answers these are correct words from the letter combinations prokaryotic eukaryotic cytoplasm organelles centrosome there how many words have you correctly arranged if you got all five wonder badges here is your first wonder gold medal earlier i have mentioned that the cell cycle can be thought of as the life cycle of a cell in other words it is the series of growth and development steps that a cell undergoes between its birth or the formation with the division of a mother cell and reproduction or the division to make two new daughter cells to divide a cell must complete several important tasks it must grow copies genetic material and physically split into two daughter cells cells perform these tasks in an organized predictable series of steps that make up the cell cycle well what exactly is a cell cycle cell cycle is the name we give the process through which cells replicate and make two new cells in eukaryotic cells or cells with a nucleus the stages of the cell cycle are divided into two major phases interphase and the mitotic phase during interface the cell grows and makes a copy of its dna or deoxyribonucleic acid during the mitotic phase the cell separates its dna into two sets and divides its cytoplasm forming two new cells let's enter the cell cycle just as the cell forms by division of its mother cell what must this newborn cell do next if it wants to go on and divide itself during interface the cell undergoes normal growth processes while also preparing for cell division in order for a cell to move from interface into the mitotic phase many internal and external conditions must be met interface occurs in three stages namely g1 s and g2 what happens in each phase let's discuss one by one the first stage of interface is called the g1 phase or the first gap because from a microscopic aspect little change is visible however during the g1 stage the cell is quite active at the biochemical level the cell is accumulating the building blocks of chromosomal dna and the associated proteins as well as accumulating sufficient energy reserves to complete the task of replicating each chromosome in the nucleus second the s-space or synthesis of dna throughout interface nuclear dna remains in a semi-condensed chromatin configuration in the s-phase dna replication can proceed through the mechanisms that result in the formation of identical pairs of dna molecules or sister chromatids that are firmly attached to the centromeric region the centrosome is duplicated during the s phase the two centrosomes will give rise to the methodic spindle the apparatus orchestrates the movement of chromosomes during mitosis take note centrioles are not present in the centrosomes of other eukaryotic species such as plants and most fungi and third the genophase or the second gap in the genophage the cell replenishes its stored energy and synthesizes proteins necessary for chromosome manipulation some cell organelles are duplicated and the cytoskeleton is dismantled to provide resources for the mitotic phase there may be additional cell growth during g2 the final preparations for the methodic phase must be completed before the cell is able to enter the first stage of mitosis to sum it up the g1 s and g the faces together are known as interface it is worth to note that the prefix enter means between reflecting the interface takes place between one mitotic phase and the next wonder learners how are you so far remember if you don't take notes you will forget everything we discussed today so make sure to write down important details for easy remembering earlier you learned that the first major phase of the cell cycle is called the interface which is divided into three stages can you quickly recall the three stages excellent work the three stages of the interface include g1 s and g2 wonder learners i commend you for your quick remembering keep up with the good work and now let's proceed to the next phase of the cell cycle which is the m phase [Music] vm or mitotic phase is a multi-step process during which the duplicated chromosomes are aligned separated and moved into two new identical daughter cells mitosis is the tightly regulated process of cell division that includes both nuclear division and the division of cytoplasm to two daughter cells there are two portions of the mitotic phase the first portion is called cardiokinesis or a nuclear division and the second portion is called cytokinesis or the physical separation of the cytoplasmic components into the two daughter cells in mitosis the nuclear dna of the cell condenses into visible promises and is pulled apart by the mitotic spindle a specialized structure made out of microtubules mitosis takes place in four stages prophase sometimes divided into early prophase and prometaphase metaphase anaphase and telophase the products of mitosis are two daughter cells that have identical dna content that is also identical to the dna content of the original parental cell we will know more about the distinct phases of mitosis in our next episode in cytokinesis the cytoplasm of the cell is split into making two new cells cytokinesis usually begins just as mitosis is ending with a little overlap cytokinesis takes place differently in animal and plant cells in animals soul division occurs when a band of cytoskeletal fibers called the contractile ring contracts inward and pinches the cell into a process called contractile cytokinesis the indentation produced as the ring contracts inward is called the cleavage furrow animal cells can be pinched in two because they are relatively soft and squishy [Music] on the other hand plant cells are much stiffer than animal cells they are surrounded by a rigid cell wall and have high internal pressure because of this plant cells divide in two by building a new structure down the middle of the cell this structure known as the cell plate is made up of plasma membrane and cell wall components delivered in vesicles and it partitions the cell into what happens to the two daughter cells produced in one round of the cell cycle well the answer depends on what type of cells they are some types of cells divide rapidly and in these cases the daughter cells may immediately undergo another round of cell division for instance many cell types in an early embryo divide rapidly and so do cells in a tumor other types of cells divide slowly or not at all these cells may exit the g1 phase and enter a resting state called g0 phase in g0 phase a cell is not actively preparing to divide it's just doing its job for instance it might conduct signals as a neuron or store carbohydrate as a liver cell g0 is a permanent state for some cells where they remain metabolically active but no longer proliferate unless called on to do so they appropriate extracellular signal while others may restart division if they get the right signals in contrast to the rapid proliferation of embryonic cells some cells in adult animals sees division altogether example nerve cells and many other cells divide only occasionally as needed to replace cells that have been lost because of injury or cell death cells of the letter type include skin fibroblasts as well as the cells of many internal organs such as the liver kidney and lung did you know that different cells take different lengths of time to complete the cell cycle the duration of v-cell cycle phases varies considerably in different kinds of cells for a typical rapidly proliferating human cell with a total cycle time of 24 hours the g1 phase might last about 11 hours s phase about 8 hours g2 about 4 hours and m about 1 hour but fast cycling mammalian cells like the ones that line the entistem can complete the cycle every 9-10 hours when they're grown in culture other types of cells however can divide much more rapidly different types of cells also split their time between cell cycle phases in different ways in early frog embryos for example cells spend almost no time in g1 and g2 and instead rapidly cycle between s and m faces resulting in the division of one big cell the zygote into many smaller cells so there you have just learned about the phases of the cell cycle their characteristics and their control points you are now ready to move forward to the next lesson but before that let's evaluate what you have learned so far from our biology lesson challenge yourself to do this five item quiz i will read the question and choices once you're only given 5 seconds to write the letter of the correct answer for each question you will be given one wonder badge for every correct answer are you ready wonder some learners let's play science pop quiz [Music] question number one most of the life of any cell is spent in a period of growth called blank a telophase b prophase c interphase or d anaphase [Music] the correct answer is letter c interface question number two which choice best describes the cell cycle a cells grow and develop during interphase cells reproduce during the mitotic phase b cells grow and develop during the metabolic phase and cells reproduce during interphase c the nucleus of a cell divides during interphase and the cytoplasm of a cell divides during the mitotic phase or d the nucleus of a cell divides during the mitotic phase and the cytoplasm of a cell divides during interface [Music] the correct answer is letter a cells grow and develop during interphase and cells reproduce during the mitotic phase question number three how long does it take for most dividing human cells to complete a cell cycle a a few minutes be a day see a year or a day about seven years [Music] the correct answer is letter b a day question number four during which phase of interface do cells copy their dna a s phase b g1 phase c g2 phase or d cytokinesis [Music] the correct answer is letter a s base question number five which best describes how a plant cell divides a a new cell plate and wall forms in the middle of a cell and two new cells are formed b the two cells twist apart c the membrane pinches shot in the middle of the cell and the cells are split apart or d plant cells do not divide [Music] the correct answer is letter a a new cell plate and wall forms in the middle of a cell and two new cells are formed excellent job stem learners i am happy that you were able to challenge yourselves to do the pop quiz now let us add all the wonder badges you've collected from the pop quiz how many badges have you collected for all the effort that you do i will give you your second wonder gold neddle [Music] for your assignment perform this activity at home arrange the following events in correct order spindle fibers emerge from the centrosomes chromosomes condense and become visible nucleolus disappears nuclear envelope breaks down write your answer in your biology interactive notebook and that ends our wonder learning exploration for the day but don't worry more science adventures are coming your way keep exploring and never stop learning always remember learning biology is fun for everyone this has been your wonder teacher melvin see you next time for another episode of fun wonder learning adventures only here at defin tv [Music] you