hi everybody and welcome back to miss Angler's biology classroom I am Miss angler and in today's video we are going to be looking at reproductive strategies in vertebrates now if you're new here don't forget to give this video a thumbs up subscribe and turn your notifications on because I post regularly on Tuesdays and Thursdays with fresh content for grades 8 to 12 now the core content of today's video is going to focus around the different ways in which Brits reproduce what are the advantages and disadvantages of each of them and I'm going to highlight all the really important stuff that you need to know for your exams so what is the purpose of having so many different reproductive strategies amongst animals remember the goal in the animal kingdom is to produce more of yourself in actual fact that is the goal of all living organisms make more of yourself and so in order to do that different animals have different strategies which allow them to make as many of them as possible with either the most resources available or with very few resources available now an important step in reproduction is fertilization which refers to when an egg cell and a sperm cell combine together in order to form an embryo and there are two main kinds of fertilization that occur in the animal kingdom and that is external fertilization and internal we're going to focus first on the external fertilization now when you study this particular topic you need to be very familiar with the advantages and the disadvantages of the types of fertilization now in the photograph in front of you you can see a frog and you can see that it's made thousands of eggs and you'll notice it's in water now this is an important thing for external fertilization because a key feature of external fertilization is making many many eggs often in an aquatic environment and it requires very little parental care once they are actually laid now because there's so many eggs um frogs are trying to increase the chances of fertilization because no one's actually hanging around the eggs we don't actually know for certain whether or not they'll get fertilized so let's have a look at some of the key facts you will need to know for your exam about external fertilization now first things first when we Define it we are looking for things like external fertilization is when gametes the egg cells and the sperm cells join outside of the body there are often a large number of gamits as we can see a large number of egg cells along with sperm cells and it is occurring in water now in terms of the advantages the parents don't need to be in the same location which is great because what it means is like this frog she can lay her eggs and she doesn't have to be around waiting for a male to fertilize them a male can Simply Swim past find the eggs and fertilize them which means it requires very little energy to find a m the disadvantage however is the chance of fertilization that means that she can lay all these eggs and if nobody swims past they'll never get fertilized the good thing however is that these eggs that she laid you can see they're very simple they're actually just like a gelatinous ball they don't require a lot of energy and that's why she can make so many of them is it wasteful it can be however she puts very very little effort into making so many of them the next form of fertilization is internal fertilization now this occurs mostly in terrestrial animals so we're talking reptiles birds and mammals and because there's no external water for sperm to swim in the male gamuts the sperm cells need to be released directly into the body of the female now this comes with advantages and some disadvantages so let's have a look at those side by side along with the external fot ization again so we can make a clear comparison so in our table here we have let's look at the internal internal gametes are now inside the body the requirements is you're going to need a specialized organ you're either going to need a penis and vagina you're going to have something called a CLA you need some kind of reproductive organ and there is going to be a mating ritual in order for there to be fertilization to occur now the advantages is that there's going to be much greater chance of fertilization and that is because um the sperm cells are released inside of the female which means that they are really close um into contact with the egg cells um another Advantage is that you don't need to make as many gametes because you are uh ensuring that the gamuts are very close to one another it ensures fertilization it means sperm cells don't have to swim very far they're very close they're not going to be washed away um it's not going to be destroyed by sunlight and so it increases the chances of fertilization the disadvantage however is that the parents must be in the same location at the same time in other words more effort needs to be placed in finding a mate and if the conditions are not right it is often very difficult for in internal fertilization to occur now we're going to take a look at what happens after fertilization do we lay an egg do we give birth to live young what are the options now for this I'm going to use sharks as my example for each one of the different ways in which Offspring can be birthed or laid in terms of eggs please know that there are plenty of other examples of animals under each of these categories I'm only using sharks because they actually fall into all three categories there are examples of species that are ous over viperous and vorous I know the words are very similar and don't worry we'll unpack each of them now so you know what they mean but I'm going to use them as my example so it's uniform and continuous throughout and we'll start with oery now when you see the word oie or over I want you to think of egg this is an example of a shark that will lay an egg in other words fertilization will occur internally and their egg will be laid and sometimes they're known as mermaids purses and they come in all these beautiful shapes that you can see over here and essentially ovor means that the um baby or the embryo is going to grow outside the female's body and so some defining characteristics of aery is that the eggs developed outside of the parent and that the egg Yol that is on the inside is the only source of food to the shark while it is growing now there are some advantages to this kind of um let's call it egg production and that is the eggs contain a lot of nutrients inside them particularly the yolk there is protection from the elements generally the shell of the egg is quite thick there's also incubation which means it keeps it warm and safe and finally most animals that lay eggs provide parental Care Now sharks are just one kind of an example of an animal that lays eggs there are other animals think of like a chicken or a snake or a lizard they all lay eggs and they would also fall into this category now in any test or an exam you will be expected to draw one of these eggs that we spoke about now specifically the amniotic egg you should be able to draw it label it and also tell me the functions of all of the structures that we find inside of it and I'm going to quickly recap all of them we'll start off with the outermost layer which is the shell this is going to provide VI protection it's going to incubate the egg and keep it safe if we move one layer in you'll see something called the alamin which is if you've cracked a chicken egg open before it's the egg white part and essentially it allows for the um developing embryo to float uh so that it's undamaged then we move on to the Coran now the Coran specifically surrounds all the other membranes and it's responsible for gaseous Exchange in other words that little embryo growing and there needs to exchange gases it needs to be able to exchange oxygen with carbon dioxide and basically breathe now in placental animals you have your placenta and you have an umbilical cord and this will allow you to exchange gases with your mother but eggs don't have that remember they're outside of the female the next layer beyond that is the amnon now the amnon and the amniotic fluid are linked together the amnon is the membrane and the fluid is what fills that membrane and the amnon is responsible for protecting against dehydration and mechanical injury so that they can float around and be safe beyond that we then have the alen toys now the alen toys is responsible for collecting nitrogenous wastes essentially as that little embryo grows you need somewhere to put all the wasts it makes and so it's stored away in the AL on toys the next two labels are fairly straight forward we have the embryo which is the developing um fetus and finally we have the Yol sac and the Yol Sac is literally as you imagine a chicken egg it's the yolk it's the yellow part of the egg that's where all the nutrients come from to grow that embryo remember the eggs are not inside the female anymore so somebody has to feed this growing embryo the next reproductive strategy is oo VI viy I know it's a mouthful and it probably looks very similar to the one we just now because it sounds the same and it looks like there's eggs but there's a few major changes yes yet again the name has the word oo in it which means egg but V viery means to give birth live so we're not laying any eggs this time and again I'm going to use a different species of shark as an example now these particular sharks um have internal fertilization as we know but the eggs are kept on the inside of the shark and as you can see here at this little bottom picture the shark is going to carry the eggs until they hatch and they're going to hatch inside of the female's body and so when we talk about over viy eggs are kept inside and Offspring is often born alive it sometimes is confusing because that makes them look like mammals but it's it's not they're actually hatched on the inside and sometimes what they do for nutrition if we look on the other side of the picture is these little sharks will either have a Yol sack you can see in this top picture over here in the corner you've got a little Yol sack they might eat uh their fellow siblings who weren't fertilized unfortunately for them or there's like a Milky like substance that is secreted by the mother into her reproductive system for them to feed off of and so they grow inside the female they become mature and they're still inside their egg it's important okay they haven't left their egg casing but these eggs are a bit softer they don't have a hard shell and eventually they're born live and they can swim around and they don't actually don't need their parents after that so let's look at those advantages of being over viperous there are fewer eggs which is important because it means you're going to put less effort um into protecting them and rather more effort into making the eggs your embryo is less vulnerable because it's inside the female it's protected by the female herself and lastly young are born fully de developed which is really important because what that means is they can literally be born and they can swim away they don't have to be nursed by their parent the parent put all the energy into growing them and now they can go off and they can live freely without their parent the final category of our reproductive strategies is the viy and this is where we fall into this category where we give birth to live young and that's what the vi viery means to to Bear live living young and again I'm going to use one my little sharks here as an example certain species of sharks do give birth to live young so what does it mean to be vorous essentially it means your eggs do not have a shell around them and our animals our offspring are born living now if we look at out a little shark here you can see that the shark along with animals uh like humans and chimpanzees and cats and dogs they all fall into this category and all of the small embryos or the babies are held inside the body and they grow inside the body and they have something called a placenta which you can see over here is this um sack that is attached to them by the uh umbilical cord that's what actually gives you your belly button is the connection between you your placenta and your mother and that means some sharks also have a belly button isn't that funny to think about it but essentially the placenta allows nutrients and wastes to be exchanged between the mother and the baby and what that does is it gives us certain advantages those advantages include a reduced number of eggs because the fewer the eggs the more effort the mother can put into parental care and looking after her babies as they grow inside of her it also provides extra nutrition and lastly that parental care that I mentioned earlier is really important because essentially it means that the mother put all this effort into growing her babies on the inside now that she's birthed them she doesn't want them to die straight away she she's put all that effort in so she's going to continue to put effort in and look after them um to ensure that they survive to reproductive age as well now that we've looked at fertilization we've looked at the formation of the embryo and how we grow it either in an egg or not in an egg what happens after the animal comes out of its egg or out of its mother how do they develop and so the development stage is either going to be a precocial one or altricial let's look at the precocial first and so that's the example running down the left hand side animals that are born with a precocial um strategy means that they are born ready to go you will notice my example here is of a little chicken you will see that it has its fur it can or it's like fluffy down feathers it can stand it can see it can move around it can find food does it follow its mother around yes for a limited amount of time and prediction but that little baby chicken is free to roam around as it pleases on the other hand you have altricial development and this is where animals are born blind naked which means they have no hair no fur and you can see that on this side with this example of this kind of bird you'll see that they don't have their eyes open they don't have any feathers yet they're in the nest they can't walk they can't fly and so they are very reliant on their parents to provide them with food and protection both of these strategies are dependent on the resources available to those species as always I like to end off my lessons with a terminology recap now you can use all of these words for your flash cards which is the best way to study now we looked at types of fertilization internal fertilization happens inside of the female and it ensures that the sperm cell meets the egg whereas external fertilization happens on the outside of the female and in order to make up for the fact that we might not ensure sperm meet the egg we make many many many eggs to make up for that we then looked at the developmental options the way in which the embryo is going to develop and we looked at OVI OVI is when a hard shelled egg is laid outside of the female body and we call this egg the amniotic egg the amniotic egg has the Coran the amnon the alen toys and the Yol each providing a different Nutri nutrition or a waste function for that embryo as it develops we then moved on to OVO viery which is when eggs are held within the female's body the embryo develops inside the egg they hatch inside the mother first and then she gives birth to live young finally we look to for the viy the viy is where we fall in as humans and these organisms give birth to live young and they have a placenta sharing nutrients as well as wastes with their mother lastly we looked at what we would call a developmental stage after birth and we looked at precocial and altricial precocial means that these organisms are born able to walk around see and F for themselves altricial are organisms that are unable to look after themselves they're often blind hairless and very vulnerable to predation now as always if if you've enjoyed this video don't forget to give it a thumbs up like And subscribe turn your notifications on everybody because I post regularly on Tuesdays and Thursdays for grade 8 to 12 and I'll see you all again soon bye