hello everyone and welcome to this year's last minute crash review for your end of course biology exam this video is for students who are about to take a final course test EOC or state exam in biology that means you might be in 9th or 10th grade right now but that may vary depending on your school or state in this video I'm going to quickly review some really important content that's commonly questioned on the end of course biology exams and review some basic skills that might pop up on your test remember this is a fast review so it won't cover everything you learned in biology and I do talk fast so feel free to change the speed on your video player if you need if you need to go back and do a deeper dive on any of these topics make sure to check out the other resources on my channel let's get started very briefly remember all matter on earth is made of different elements elements are composed of different atoms and in biology we really want to focus on molecules called organic compounds now these are special molecules that all contain carbon that are essential for life and the forming categories are nucleic acids proteins carbohydrates and lipids so we look at what they're made of the monomers or the basic units of nucleic acids are nucleotides the basic monomers of proteins are amino acids and carbohydrates the monomers are monosaccharide and the basic monomers of lipids are often fatty acids and glycerol now up here I have the basic structure as well this is actually a phospholipid which makes up the cell membrane of all living things and we'll get to that in a little bit now to remember all of these organic compound groups I like the pneumonic clean later party now for carbohydrates lipids proteins and nucleic acid acids one thing I like to add to this is clean later party especially now to remember that enzymes for that e are a type of protein which is really important enzymes are really important biological macro molecules and they belong in the protein category now let's talk about water really quick water is the universal solvent it is polar that means it's partially positive and partially negative on opposite ends so some molecules are water loving we call these hydrophilic and they interact easily they're soluble with water hydrophobic or water fearing molecules like oils and fats are insoluble in water now water has special properties it has cohesion meaning water is attracted to itself adhesion is the attraction of water molecules to other molecules or other things thinking adding something on capillary action is when cohesion and adhesion work together pulling up against gravity we can see this in stems in plants or in a straw even and water also has a high surface tension meaning it's more attracted to itself then the air around it which allows certain bugs like Strider bugs and leaves to float on the surface of water now let's get microscopic and go down to the cell remember cells are the basic units of life so all living things have cells all cells are surrounded by a cell membrane which is a phospholipid bilayer we talked about lipids all living things contain genetic information DNA and all cells have cytoplasm now if we look just at the cell membrane let's zoom in really closely it is actually a layer of two rows of phos phospholipids so are Bayer uh the heads of these fosol lipids are hydrophilic so they are able to interact with water easily the inner parts the Tails here they're ranging themselves away from the water because they are hydrophobic now there's two main types of cells we have eukaryotic cells which have a nucleus and membranebound organel like the mitochondria and then we have procaryotic cells which also are surrounded by membrane and also have DNA but they do not have a nucleus and they do not have membrane bound organel they do have ribosomes they do have a cytoplasm but we notice here the DNA which is the scribbles on the diagram is just floating freely in the cytoplasm unlike the DNA and eukaryotic organisms which is in the nucleus now eukaryotic organisms can be animals they can be plants and procaryotic organisms are mostly bacteria we have archa as well within our eukariotic cells we have different types for example animal cells over here which have a cell membrane and plant cells which are also surrounded by a cell wall for extra protection and support another key difference between plant and animal cells is the presence of a chloroplast which is shown right here chloroplasts are the location of photosynthesis which plants perform animal cells do not plant cells also have one rather large vacu and animal cells also have a vacu but um it's not as big and they may have several different vacul as well and remember both plant and animal cells plant and animal cells are both eukaryotic now let's zoom in once again on that cell membrane remember it is made made of a phospholipid Bayer now different molecules can get in and out of the cell membrane in different ways we have simple diffusion which is the movement of particles from a higher concentration to a lower concentration we have facilitated diffusion which allows particles to move from a higher concentration to a lower concentration but across a membrane facilitated being helped this protein channel is helping the molecules get through the membrane then we have active transport which allows molecules to move from a low concentration to a higher con concentration with the help of energy in the form of ATP so a way I like to remember this is kids going down the slide so simple diffusion requires no energy it's just a kid going down the slide from high to low by themselves facilitated diffusion might have a parent or a friend which is representative of our protein and they're going from high to low as well still requiring no energy themselves and then active transport think of a child going from low to high going up the slide so against the concentration gradient but they have to use energy to do that so they're using ATP all right when water moves across a membrane this is called osmosis this is water moving from a higher concentration of water particles to a lower concentration of water and when we think about where the water is moving and comparison to the solute or the other particles dissolved in the water solution here we have kind of an equal balance of particles in and out of the cell that are not water so we would call this an isotonic solution and water would move freely in both directions and about the same amounts in this situation we have a higher concentration of particles or solute inside the cell but a higher concentration of water particles which is the blue here outside of the cell so where would the water move the water would move into the cell this is a situation called a hypotonic solution where there are fewer solute particles outside the cell more inside the cell more water outside the cell a lower concentration of water inside the cell so water would move in and now here we have more solute particles out outside the cell or a higher concentration of solute particles so remember where is water going to move from a high concentration of water so that means it would move outside the cell this is called a hypertonic environment now in a hypertonic environment there is a chance that if a lot of water moves out of the cell the cell could actually shrink and the opposite would happen in a hypotonic environment a lot of water may move into the cell causing it to swell or burst let's get back to enzymes remember these are a type of proteins they are extremely important to living things they are biological catalysts meaning they get things going they get reactions started things like ligase helicase polymerase amase these are all enzymes notice all of these words and in the letters as e which makes it easy to recognize an enzyme even if you've never seen it before some things that can affect enzymes are temperature or pH if enzymes get too hot they can denature or unfold and then they'd be unable to act with their substrate because they no longer have the shape of the active site which is where a protein or an enzyme usually interacts with the substrate the molecule that it's going to do something to or interact with all right let's jump over to cellular respiration now all living things need energy and one of the main ways they get that is through cellular respiration which occurs in the mitochondria this is the process where organisms take glucose sugar and oxygen and go through reactions to transform it into ATP energy in that process carbon dioxide and water are also generated so if we think about this on a larger scale when we eat we consume glucose when we inhale we take in oxygen and when we exhale that CO2 is a byproduct of cellular respiration we exhale water vapor as well you can see that coming out of your mouth on a cold day and then ATP is also generated which gives us the energy to perform our daily activities and survive all eukaryotic organisms are going to perform some type of respiration another important reaction we need to be aware of is photosynthesis this is how plants get the food they need and they use sunlight energy to convert the carbon and carbon dioxide into food molecules like glucose so carbon dioxide in the sunlight energy and water can be transformed into glucose and oxygen remember the plants need that glucose and oxygen to perform cellular respiration themselves so these processes are complimentary and they feed each other which is why photosynthesis is crucial to life on Earth another type of respiration is fermentation this is often called anerobic respiration it's a type of anerobic respiration but that means it occurs without oxygen so bacteria some yeast perform this process and fermentation is not as efficient as cellular respiration cellular respiration produces 36 molecules of ATP where fermentation only produces two molecules of ATP so even though we can also perform fermentation in our muscle cells for example when we run out of oxygen cellular respiration is a much more efficient efficient process for producing energy molecules so like I said the type of fermentation that we can do in our muscle cells is called lactic acid ferment ation and that's because we take glucose and we generate energy molecules ATP but also lactic acid as a byproduct now yeast can do another type of fermentation called alcoholic fermentation and here the yeast produce ethanol as a byproduct or a type of alcohol and carbon dioxide so that carbon dioxide we can see as bubbles forming if you've ever done an experiment with yeast and fermentation it's why Bakers use yeast in their baking because that carbon dioxide can help bread rise and then also of course ATP is generated in this process let's get down to the DNA in our cells remember all living things contain DNA now DNA is organized it is wound up into chromosomes and condenses into chromosomal form before the cell can divide remember each double-sided chromosome that looks like this actually is a duplicated set of DNA so we have two sister chromatids here they're connected at the center by a centrr but usually within the cell if the cell is not preparing for cell division it may not be condensed into these chromosome forms it may may just be in chromatin form which sounds similar to chromosome but it kind of is represented as this like spaghetti like drawing where the DNA is Unwound it's not condensed as the cell prepares for cell division we may see the chromosomes begin to look like this that means the DNA has already been duplicated and the chromosomes are arranging themselves so they can prepare for cell division mitosis is a type of asexual reproduction where cells make exact copies of themselves one cell can generate two identical daughter cells you might have learned the phases of mitosis as Pat which stands for prophase metaphase anaphase and telophase and then at the end there's cyto Kinesis where the cytoplasm actually divides now in prophase the nuclear envelope dissolves and the chromosomes condense they start to move to the middle of the cell and metaphase they align along that cellular equator or the center of the cell and these spindle fibers on opposite ends of the cell come and attach the cir in anaphase think a for away the cytochrom are separated they start to get pulled away from each other towards opposite ends of the cell in telophase new nuclear envelopes start to form the cell starts to separate and inside a Kinesis we have the exact separation of the cytoplasm now with mitosis you've probably also studied meiosis which is a different type of cell division mitosis remember will copy body cells make exact duplicates of cells so one parent cell will create two identical daughter cells whereas meiosis is the process used to generate sex cells so one parent cell that goes through meiosis will generate four daughter cells but they'll only have half the genetic information as the parent cell so meiosis takes a little bit longer it goes through pmac twice and you don't need to memorize what happens in every single stage but the results are important so at the end of meiosis there are going to be four daughter cells each with half the genetic information as the parent cell and this genetic information has been mixed up a little bit so it's a different combination in each cell so the genetic information is different at the end of meiosis which is going to be helpful in the diversity of life on Earth as organisms reproduce sexually now as organisms reproduce we pass on our genetic traits Gregor Mandel was often called the father of genetics he did studies that recognize that a lot of traits are controlled by two different alals or versions of a gene and alals can be dominant or recessive meaning one can cover up a particular trait so we have these words heterozygous homozygous to talk about genotypes or combinations of genes so for example this big T Big T would be a homozygous dominant genotype and each of these letters represents a version of that Gene so you could pause and try to fill this in for yourself but here we go we have big T Big T would be homozygous dominant Big B little B would be heterozygous because it's two different versions of the same gene and Little T Little T is homozygous recessive two different versions of the recessive gene remember a big T often represents a dominant Al and a little or a lowercase letter would represent a recessive Al so for example if yellow body color is dominant to Blue in these fish if we have a Big Y and a little y that would result in a fish being yellow that's the phenotype so if we write the phenotypes here we would see what would happen with each of these genotypes remember genotypes are the combination of genes phenotypes are the actual physical character istics that we get from the genotype so you can pause this and go through each of the examples if you want and you might have also practiced punet squares in biology where you have to separate the alals of both parents on this table and figure out the possible combinations that could result from this Cross or from when these parents mate what their offspring could potentially have and remember what happens in a punet square is just a probability it is a potential outcome we won't know for sure until the off spring are born what the actual genotypes and phenotypes are and remember most human traits most genetics are very complicated so it's not as simple as Gregor mandelle said there's different types of dominance like incomplete dominance where there's a blending of traits co-dominance where we see representations of both traits so for example if a purple and a pink flower were co-dominant for flower color we might see both purple and pink petals in their flowers and of course there's also sex linked traits which are traits that are carried on the ex and the Y chromosomes now humans have 23 pairs of chromosomes that 23rd pair is going to be the sex chromosomes and females have two X chromosomes males have an X and A Y we talk about traits like color blindness these are traits that are carried on the chromosomes that are sex chromosomes so when we perform genetic crosses with sex linked traits we'll also write the X and the Y there and the alil as an exponent and make sure we carry all of the letters together in our punet Square cross process now genes can also be influenced by the environment for example these hydrangeas can have different colors based on the pH of the soil and this can go for a lot of different traits sometimes there's temperature differences that can change the color of fur of different mammals and of course chromosomes can have problems separating during meiosis or mitosis and when we have that non-disjunction or those sister chromatids not going to the opposite end of the cell correctly we could end up with a cell with different numbers of chromosomes for example triom 21 would mean that we have three copies of the 21st chromosome and triom 21 is also known as Down syndrome and that mean that person would have a condition that affects their physical characteristics some of their development because of that extra copy of that chromosome now let's talk about DNA a little bit closer now remember that in DNA we have four different bases A's T's G's and C's a is always pair with t g is always pair with C DNA replicates during the S phase of the cell cycle and in DNA replication we have the DNA strand separating and new strands of DNA are built off the templat so it's called semiconservative replication each new strand of DNA has half the old Strand and half brand new if we look back at our organic compound structure each nucleotide has a phosphate a sugar and a base atg or C and so when we put these together A's and T's we can see always pair together with these are little hydrogen bonds in the middle G's and C's always pair together and the backbone of the DNA molecule is made of phosphate and sugar molecules so how do we get exactly from our DNA to our actual trait well the process is called protein synthesis and in the nucleus where the DNA is the DNA will separate and then an mRNA sequence will be built off of the DNA template that mRNA will leave the nucleus and that process is transcription then we'll go through translation where the MRNA will go to a ribosome and tRNA molecules a different type of RNA will match up with the codons or the different groups of mRNA and bring over a matching amino acid and then those amino acids will start to link up and remember amino acids make proteins and so that is how we deliver the message to build the protein that is going to give us some trait in our bodies like the protein that influences eye color or the protein that gives us our hair shape so some differences to remember between DNA and RNA DNA is double stranded RNA is single stranded DNA has actually a deoxy ribo sugar that's where its name comes from deoxy ribonucleic Acid where RNA is made of a ribo sugar and then DNA's bases are A's T's G's and C's where RNA actually has a u instead of a t so if you're creating an RNA strand based off DNA remember to replace wherever a t would go with a u let's do a little practice so if we're transcribing a sequence of DNA this purple is the DNA here the sequence is a g t g t c the complimentary RNA would be a pairs with u g pairs with C T pairs with a G pairs with C T pairs with A and C pairs with G so again try this on your own go ahead and pause real quick the correct mRNA sequence here would be a ug CG auu and then don't forget the next step is translation where we build that protein and to do this by hand you might see a codon chart where you're asked to find the codon and then the matching amino acids so let's say we were looking at a codon that was CCC so we'd start in the center find the C then find the next C in the next Circle and then go to the final Circle here find that c that refers to Pro which is short for Proline one of our amino acids you do not need to memorize all your amino acids and if you're ever asked to do translation on a biology exam you will be provided with a codeon chart codeon charts can also look like this so let's look at CCC again C is our first base here we would go to the top for our second base here's another C and then find that third base C that also corresponds to Proline on this chart it is a universal genetic code let's talk really quickly about biotechnology now there's lots of different growing and emerging new technologies in the field of biotechnology from lab grown meat to DNA tests to genetically engineered organisms to resurrecting woly man Mammoth to crisper DNA and so of course there's ethical questions that go along with all these new techniques one technique you might see on your exam would be gel electropheresis which is a way to identify different parts of DNA so gel electropheresis can be used to study evolutionary relationships identify DNA found at crime scenes or maternity or paternity testing so here we have a simple gel in the gel DNA is loaded at these Wells at the top DNA is negatively charged so it'll be attracted towards the positive and then these DNA samples will travel down this gel as we run an electric current through the gel and we can see which pairs match up so here we have a mother which matches with child a and child B child C though does not have any matches with the mother so we can say that child C is not related to this particular mother and on a much larger scale remember that evolution is the change in genetic makeup of a population over time natural selection is the major mechanism behind Evolution and when we talk about an organism Being evolutionarily Fit that means means how well they are able to survive and reproduce not how strong they are not how fast they are it's really about how they can survive and pass on their traits to their offspring and remember that environments are a huge factor in evolution and they can act as a selective pressure and different organisms will have better rates of survival in different types of environments an adaptation is an inherited trait that is favorable to an organism that helps an organism survive and Charles Darwin was one of our main scientists that created this idea of natural selection we have lots of evidence now to support this idea of evolution from the fossil record to biochemical and DNA evidence embryology we can see how different organisms develop very similarly through the study of their embryos a philogenetic tree or a cladogram is a way to look at different evolutionary relationships over time and when we see branches on a tree we can see where their last common ancestor might have been and we can also add traits to this tree so if we look at a tree like this we can read it as anytime there's a trait that appears any organism that comes after that trait developed that trait so for example the organisms on this tree that have vascular tissue are ferns pine trees and flowering plants but not mosses and the organisms or the groups of organisms that have seeds are pine trees and flowering plants but not Ferns and mosses now backing all the way up to the biosphere remember different levels of organization in biology go from molecule all the way up to all life on Earth and at the population community and ecosystem level we can talk about biodiversity which is a measure of the variety of different types of organisms in an ecosystem and biodiversity is very important to living things because the more biodiverse an ecosystem is the more resilient it will be now of course environments are always changing large scale changes that can influence ecosystem can be maybe the addition of different nutrients to a system we could have forest fires we could have droughts we could have floods earthquakes there's so many things that could influence and create major changes to an ecosystem in a food chain we can see that organisms that produce their food often come first so producers like these autot tropes or grass are here and we always drew the arrow pointing towards the organism that is doing the eating so think about this food going into this Elk's stomach that's the direction of arrows for a food chain or a food web now we have our producers or our autotrophs here are heterotrophs are organisms that get their food from something else so they don't make it on their own they consume their food this is also a heter trro and this is also a hetro and when we go up a food chain or a food web we can also identify organisms as producers or consumers so this is a producer this is a primary consumer because it's the first organism that eats the producer this is a secondary consumer and this is a tertiary consumer if the human were to eat the Bobcat on a trophic pyramid remember that the most energy is found at the bottom of the pyramid and as you go up a level most of that energy is lost to the environment so it's more efficient to consume lower on at trophic pyramid if you're an organism there are tons of different mod molecules and atoms cycling throughout our environment carbon is one of them and the carbon cycle involves both photosynthesis the plants harnessing sunlight energy in order to take the carbon dioxide from the air and create glucose molecules respiration we take that glucose and we use it to create energy and then we exhale the carbon dioxide decomposition can break down carbon in organisms bodies and combustion also releases carbon dioxide into the environment now there are tons of resources on Earth some are renewable which means they can be replaced quickly by natural processes some are non-renewable meaning they cannot be replaced generally within human lifetimes or as fast as they are being used and so we need to consider the our use of resources as the population of humans continues to boom on planet Earth a hole in the ozone layer is a problem that we've identified recently but it's actually getting better but this hole produced by the use of cfc's or a chemical called chlorofluorocarbons was pretty dangerous cuz it was letting in armful UV radiation into the earth now this is separate from the issue of global warming which is predominantly affected by the combustion or burning of fossil fuels because that adds gases to the atmosphere that cause it to hold more heat and continued global warming can lead to rising sea levels coastal flooding but there are other human impacts plenty of human impacts on the environment such as introduction of invasive species introduction of diseases changing habitats deforestation industrialization all of these things but humans can also have a positive impact on the environment by reducing our consumption of resources recycling planting native species protecting wildlife and habitats and supporting sustainable practices wo we're coming to the end I hope this has been helpful as you cram for your biology exam I have lots of other biology AP biology and other life science resources on this channel so be sure to subscribe so you don't miss out best of luck on your biology exam let me know if you have any more questions in the comments below thanks so much for watching and give this video a like if it's been help helpful I'll see you later