hi everybody welcome to our second in a series of living environment regents review videos these videos are meant to help students review essential content in preparation for the new york state regents living environment exam but they can be used as a basic refresher for lots of different biology content and review as you follow along i encourage you to take notes and take advantage of my other resources on this youtube channel if you need a deeper dive into any of these topics and go ahead and subscribe if you find this kind of material useful for your living environment or biology review this is the second in a series of videos i'm making for students to prepare for the living environment regents exam if you haven't seen part one make sure you go back and do that now this video is gonna go over content so key ideas four through seven under standard four let's dive right in with reproduction species have to be able to reproduce in order to pass on their traits in their genes and to survive some organisms reproduce asexually and virtually all of their genes come from the same parent and so they're copies of the parent organism other organisms reproduce sexually and have half of the genetic information come from two different parents so one half comes from one parent and one half of the genetic information comes from another parent and those two haploid cells are combined you might have heard of cloning before that's the idea that we make an identical genetic copy of one organism dolly the sheep was a famous clone remember in order to get those haploid cells or gametes or sex cells for sexual reproduction we have to go through meiosis first the process of meiosis results in half the genetic information in the daughter cells and in humans this happens during the production of eggs or sperm we can get lots of genetic variation through meiosis through independent assortment of chromosomes crossing over of chromosomes during prophase one of meiosis and then of course the random fertilization of one egg cell with any one sperm cell remember mutation is an important source of genetic variation but these three reasons on this slide are very very important as well process of meiosis is important in sexual reproduction because it provides genetic variation of offspring and genetic diversity is important for the survival of a species so in order to get that egg and that sperm we have to go through the process of meiosis first then those two can undergo fertilization to produce a zygote which is a fertilized egg cell and now a diploid cell so let's put this all together in humans both a biological male and a biological female will need to undergo meiosis in order to produce eggs and sperm then one egg cell and one sperm cell will combine in fertilization after that that fertilized egg will divide and make copies of itself through mitosis as the embryo starts to grow mitosis will continue continue until the cells start to differentiate become all the different important parts of the growing embryo remember differentiation is how we get so many different types of cells from the same dna even though we have the same dna in every single one of our cells different parts of that dna are turned on or off in order to produce the proteins to make the differences in all of our cells human reproduction and development are influenced by a lot of different factors including hormones the environment and gene expression in both males and females our reproductive cycle is regulated by the cycling of different hormones throughout the body including testosterone estrogen and progesterone the cycling of hormones during the female menstrual cycle as shown here is going to involve a series of natural changes in hormone levels in order to produce the physiological effects in the uterus and the ovaries that are going to make pregnancy possible let's take a look at our gonads or our sex organs in human males and females we have gametes or our egg cells produced in the ovaries and then those eggs will leave through the fallopian tubes seen here once a fertilized egg implants in the lining of the uterus the uterus is going to provide an environment that's going to support the development of the embryo and the fetus the placenta which is connected to the developing embryo through the umbilical cord is going to provide essential nutrients and the materials for the developing fetus in males the sperm are produced in the testes is seen here and both sperm and urine are going to pass through the urethra in the male reproductive system during embryonic growth in human pregnancy the development of important essential organs occurs early during the developmental stages here again we see another impact of environment on genes because if the mother is exposing herself or the fetus to negative environmental conditions like alcohol or tobacco smoke that could have a very detrimental effect on the growing embryo that's why it's important to avoid the use of alcohol drugs and tobacco during pregnancy now switching over to key idea five let's talk a little bit about photosynthesis photosynthesis occurs in the chloroplast of plant cells and this is a very specialized process where it takes energy from the sun and converts it to organic compounds specifically glucose so that we can produce atp or the energy for cells photosynthesis is going to provide that connection between the sun's energy and the energy needs of all living systems on earth remember the inputs of photosynthesis are sunlight energy carbon dioxide and water and the outputs of photosynthesis or the products are glucose and oxygen remember plants perform photosynthesis in their chloroplasts and some single cellular organisms do as well when we say photosynthesis produces organic compounds like glucose let's take a step back and look at what organic compounds are in all organisms organic compounds are super important they're used to perform essential tasks within cells and they make up important molecules like dna proteins carbohydrates and fat and some of the chemical energy stored in these molecules is essential for life in all organisms and when i say organic i want you to remember i don't mean something grown without the use of pesticides or genetically modified organisms when we talk about organic in biology what we're talking about is something that contains carbon that's just what that means organic compounds make up all of our cells carbohydrates are really important for energy and they're used in processes like cellular respiration lipids are important structural components and also help with long-term energy in the cells one really important function of lipids that they compose the membranes of all cells so our cell membranes are formed of a phospholipid bilayer with a phosphate head and two lipid tails nucleic acids of course contain all of the genetic information and the instructions to build every protein that our body needs and you can think of proteins like the workers of the cells they're going to do all the important jobs to help our bodies and our cells function an important category or a special type of proteins are enzymes let's talk about those really quickly enzymes are made of amino acids they're specific so they have a specific structure for a very specific reaction and they are reusable so after a reaction enzymes remain unchanged enzymes work as catalysts sometimes they speed up chemical reactions other times you can think of them like molecular scissors they'll cut different molecules apart but basically they're going to lower the activation energy of reaction in order to get it to happen faster a couple enzyme vocabulary words here a substrate is the thing the enzyme reacts with a product is the result of an enzymatic reaction or what comes after the enzyme interacts with the substrate and the active site is the special site or location on the enzyme where the substrate fits in now enzymes can be affected by certain environmental changes like temperature and ph if for example an enzyme gets too hot the amino acids inside can start to unfold because enzymes are a protein and they're made of amino acids and when it unfolds or is denatured it may no longer fit with its substrate and can't perform the reactions that it needs to now lots of different enzymes are used all throughout our bodies in our cells but there's also enzymes within the process of cellular respiration that help certain reactions to occur cellular respiration is that process where we take the glucose that other organisms produce and then we consume and we take in oxygen and through a series of different biochemical reactions we produce carbon dioxide water and atp which is our energy molecule now we perform this plants perform this nearly all living organisms perform some type of respiration but aerobic cellular respiration is where we include oxygen and glucose to produce water carbon dioxide and atp if we were to look at this chemical equation and write it all the way out this is what it would look like and here is the same equation written out in words glucose and oxygen yield carbon dioxide water and atp again this is just a summary equation because there's lots of different little steps during the entire process of cellular respiration to get us to these end products anaerobic respiration does occur in our cells as well and in many other cells on earth nearly all existing organisms perform part of this which is glycolysis but it's less efficient it produces only two atp molecules instead of the 36 that are produced in regular aerobic cellular respiration there's no mitochondria needed so it can take place outside of the mitochondria in the cytosol of the cell and it doesn't need any oxygen it's an anaerobic process so there is a way to get atp and we don't have enough oxygen in our cells but it's better for our bodies to perform aerobic cellular respiration because we get more energy out of it now photosynthesis and cellular respiration are definitely related the products of one feed the other so when plants produce the glucose from photosynthesis and oxygen those products then go directly into the process of cellular respiration for either plants or us or other organisms to perform and then of course carbon dioxide produced as a byproduct of cellular respiration sunlight energy and water are going to be the things that go into photosynthesis so why do we need to produce this atp anyway well it all comes down to homeostasis our organism's ability to maintain a stable internal environment suitable for us to survive the energy from atp is used by organisms to obtain materials transform materials transport materials and of course eliminate waste from the cell in a multicellular organism we might have different mechanisms of homeostasis that we need energy to perform for example the changes in our heart rate or our respiratory rate or sweating to maintain our body temperature or releasing insulin to change our blood sugar levels and make sure they're at the right level that our body needs even plants maintain homeostasis by regulating water loss and opening and closing their stomata in their leaves active transport is one main way we use atp within the cell and we can get molecules into the cell that we need by using the chemical energy within atp in our transport proteins sometimes we encounter disease as a failure of homeostasis for example our bodies and other organisms encounter pathogens all the time pathogens can be things like viruses bacteria and fungi and they're going to infect plants and animals and interfere with normal life function but we do have something to help with homeostasis and counteract these pathogens and the effects they have and that's our immune system so our immune system is going to protect against different foreign antigens or things that are non-self and these are things that don't come from our cells we have different types of cells and molecules within our immune system to help combat these so for example we may have antibodies that we produce to go against the antigens or markers on other organisms or other viruses we might have macrophages or white blood cells that are going to engulf our foreign invaders and take care of them that way and we have other white blood cells that are going to remain as memory cells in our body and then we can fight off other invaders the next time we're introduced to that same pathogen and that's how we get vaccines to work vaccines are going to use dead or weakened or parts of microbes that might have a negative effect on our bodies and introduce those to us so that our bodies can recognize either the surface or the markers that are going to be associated with those pathogens once we know how to fight them off the next time when we're actually infected by a real version of that virus our body will be able to fight it off really easily because we already have the tools and materials to know exactly how to destroy them there's a lot of different topics if we're studying the immune system a few that i'm going to mention are certain other viral diseases like aids which is caused by an infection of hiv can weaken or damage the immune system so that we can't fight off other diseases sometimes people have allergic reactions to things that are traditionally harmless and some allergic reactions are caused by an overreaction of the immune system to typically harmless materials we can also get disease that are caused by environmental factors toxic substances genetic inheritance environmental impacts like poor nutrition organ malfunction even behaviors certain disease will appear right away others are chronic and will last for a long time and others may not show up for many many years sometimes we can have mutations in our dna that are going to cause cancer which is the uncontrolled division of cells and if we expose ourselves to certain muted mutagens or carcinogens we have a higher likelihood of developing cancer for example uv radiation is a carcinogen that could cause cancer in our skin cells all right let's take a step back and talk about the ecosystem now we already mentioned this in our first video a little bit but i want to go back to talk about how all energy on earth is really supported by the sun and of course all matter here on earth is here to stay and the atoms and molecules that we interact with and make up our bodies are the same atoms and molecules that were here hundreds of thousands of years ago think about how carbon hydrogen nitrogen and oxygen all combine and recombine together and are passed through different food and matter systems but analyzing the flow of energy and the cycling of matter within an ecosystem is important part of biology so this diagram is something that you might want to consider these plants are going to use carbon from the atmosphere to undergo photosynthesis and create glucose and oxygen which are our ingredients for respiration but if we think about if more snails are added to this container what effect is it going to have on the plants in the container eventually if we add more snails we would see more carbon dioxide and more carbon dioxide would lead to more plant growth because the plants could take in more carbon dioxide to perform more photosynthesis all of these biological molecules can be limiting as well so the number of organisms any particular habitat or ecosystem can support is dependent on the availability of certain resources within that environment for example energy water oxygen nutrients all of those are going to have an effect on how many organisms an environment can support and within an environment organisms are going to interact with each other in various ways so mutualism for example the type of behavior where both organisms are going to benefit from that relationship so for example pollinators that are going to distribute the pollen for particular flowers but also give off nectar to support the production of honey for bees parasitism is when one organism is harmed or hurt and the other organism benefits you probably know a lot of parasites in your life including these little mosquitoes here that are actually going to take your blood and then you are going to have probably an allergic reaction or mosquito bite from that particular relationship commensalism is when one organism is neither harmed nor benefits but the other organism does so for example barnacles on a baleen whale like this could be really no big deal for that whale but the barnacles have a place to live and a home a predator-prey relationship is very similar to a parasitic relationship but in this instance the organism that is harmed or hurt also dies so it is consumed by the other organism who is benefiting all ecosystems are going to go through a sequence of progressions from primary succession and secondary succession and these are changes where the ecological community modifies the environment making it more suitable for more organisms and this can take hundreds or thousands of years and eventually it'll become a stable ecosystem so as we know the earth has finite resources and increasing human consumption of those resources is definitely placing a lot of stress on the natural world and different environments so even though we are part of the earth's ecosystems we also can have lots of negative effects on them for example the introduction of invasive species can be really destructive to native organisms within an environment this is a picture of kudzu here that has overtaken a wooded area because it doesn't have any natural predators and can grow very fast and outcompete the native organisms pollution from humans is also another major human impact in the environment as we have an increase in human populations we're going to have more rapid depletion of our natural resources and more species are going to go extinct habitat loss is the number one reason a particular organism will go extinct and so when we talk about protecting threatened or endangered species protecting their habitats is a major way we can protect them and of course the burning of fossil fuels is the major contributor to the overall warming of the earth's atmosphere there are lots of different types of human impact like global climate change habitat destruction and fragmentation agriculture monocropping or introduction of invasive species or disease species or new diseases and of course waste and pollution being familiar with at least a few of these and understanding the overall impacts of humans on the environment is definitely going to be key in your living environment review lastly i want to clear up one common misconception that students have between global warming and depletion of the ozone layer both of which are caused by humans global warming though is generally caused by the combustion or the burning of fossil fuels and then leads to the warming of the earth's atmosphere when we have more of those greenhouse gases we could create the greenhouse effect which is an overall atmospheric and earth warming effect which leads to increased global temperatures extreme conditions loss of habitat sea level rise depletion of the ozone layer isn't causing global warming though so this particular event is caused by chlorofluorocarbons or halocarbons that are released into the atmosphere and they produce holes in the ozone which can lead to increased uv radiation eye damage in human skin cancer but those holes the ozone layer are not directly related to the increased warming of the earth's atmosphere so some students mix that up a lot and i just want to clear that up at the very end of our video so this has been a really quick review of the key ideas four through seven in standard four of our living environment curriculum if you're interested in learning more about some of the laboratory techniques and other parts of information that might show up on the regents exam be sure to subscribe and stay tuned thanks so much for watching and best of luck on your biology endeavors