welcome ladies and gentlemen to educate how are you great 11s today we're going to be talking about the topic of biodiversity of animals so this topic uh has been deemed very complicated by other students but I'll try my best to make things easier so we are talking about the biodiversity of animals so what is biodiversity just know that we're talking about the differences between the animals so here biodiversity is trying to refer to the differences between the animals that we have here on Earth so ladies and gentlemen let us continue with it so uh the general information remember that all animals are different because they've got different body plans remember that when talking about a body plan we just mean that um how does a body of an organism look like for example this is a rat it looks like a rat and this is a fish and it will look like a fish so they've got different body blands so what makes these bodies different from one another is the following factors so first it is the body symmetry of the organism it is the civilization it is the tissue layers the number of cut open ings as well as the presence of a body cavity so ladies and gentlemen in this video we're just going to do the body symmetry calization as well as the tissue layers so these three are um what you're going to do in this video then we'll do more in our next videos this part so let us talk about calization what is calization in these organisms so calization in an animal is just basically the presence of a head when an animal has got a head then it is it has civilization so this head must have sense organs so we not talking about sense organs we're talking about the eyes we're talking about the ears we're talking about the mouth we're talking about the nose all of those things that satisfy the five senses that we have for example this is a human head it is got eyes here it has got a nose here for smelling it has got a mouth here hence you can say that humans have got civilization because they've got a head with sense organs just like this goat here it has got eyes it has got a nose it has got a mouth the presence of this hat with sense organs it means that the goat has calization and also if you look at this chicken as as well it has got a mouth it has got eyes as well and it has got a head hence we can say that this chicken has civilization so civilization is basically when an animal has got a head and that head has got sense organs so now let us look at the body symmetry so when I'm talking about body symmetry it is just how an animal looks like when you divide or cut it so we mean that we are cutting an animal like this so when you are cutting an animal in half just like this red line here you can see that it is cutting the body of a human in half you can see that we've got a left hand side here as well as a right hand side of the cut so if you see the left hand side and the right hand side are being identical or being the same then you can say that it is bilaterally symmetrical So when you say that it is bil literally symmetrical it means that and you if you cut this animal once it means that if you cut it in Only One Direction then you will have two equal halves what do I mean by two equal halves you can see that this human body this half has got a hand this other half has got a hand as well this side has got half of a head this side have got half of a head this side has got a leg this side is got a leg so you can say that this is bilaterally symmetrical because you can cut it into two halves in only one plan such that those halves are identical to one another just like this bit hole here it has got bilateral symmetry because when you cut it using this red line here you see that this left hand side and this right hand side are equal and they are identical to one another so now why is it advantageous for an animal to be bilaterally symmetrical it is very advantageous for that animal because the animal becomes active and it constantly moves around so an animal when it would when it can be divided into two equal halves it is able to be active so this is what is well this is what is being implied by the text the second type of body symmetry which you have is radial symmetry so in this radial symmetry the same is happening we are still cutting an organism into two equal identical halves but then we can cut it in two different directions not necessarily two let's just say more than one different direction so first of all remember when you're talking about bilateral symmetry if you cut the human exactly at half only then you will have a right hand side and a left hand side that are identical but if you cut the human like this then they will not be the same so you need only to cut it in one plane in One Direction so when you talk about radial symmetry for example this is a jellyfish so oh this is actually starfish so this is a starfish so in a starfish we say that it is radially symmetrical you can cut it this way you can cut it this way you can cut it this way just to obtain two equal halves so you can cut it in any way just to obtain two equal halves I've made a good example here of an orange that explains radial symmetry so here when you want to get two halves maybe you want to share this orange with your friend you can cut it like this you can cut it like that or you can cut it straight you will still obtain two halves in whatever way you cut it so you uh in radial symmetry the body plane can be cut through more than one plane meaning that you can cut it in more than one direction just to obtain two equal hearts in any direction so now we talk about asymmetrical body symmetry so you're saying that a body is asymmetrical for example this is an animal believe it or not this is an animal so this animal is porifera so here this sponge it can be cut here but then you can see that the left hand side is not the same as the right hand side they're not identical to one another so if you can see here the right hand side has got this thing whereas the left hand side does not have it hence you can say that it is asymmetrical so it has no symmetry meaning that it cannot be divided into two equal or identical halves so right now for example this one if I cut it here this side is not equal to that side it is not not identical either so it is not the same it does not look the same so now when I cut any of the above there is no way that I can get two equal and identical Hales that is asymmetrical now this is the second characteristic that makes the bodies of animals different from one another it is the tissue layers when you're talking about tissues remember that from your previous grade 10 and grade n you know that an organism such as a human here he is a little girl here before she became a human like that she started as a single cell you should know that by now that she started as a single cell single cell single cell then she divided and all the stuff happened in the tmy of her mom and then she became a big girl so what I'm trying to say is that each and every embryo we are talking about uh the babies in the wombs of mothers so each and every embryo has got gem layers that's what we know from grade 10 and 11 so those gem layers develop into uh organs for example this is how this girl looked like when she was young but then now she looks like this now she looks like this now she looks like this now it's a human how come she became a human from here to here so it is because of certain layers which we call gem layers just like this video is illustrating that a cell goes through a certain process called tissue differentiation to be able to form organs then it later develops into an organism or an animal like this scale here so we've got um two types of tissue layers which will describe here when we've got a Diop plastic and a tripop plastic animal so when you've got a Diop plastic animals it means it contains two gem layers two tissue layers it means that the baby of this animal has got two gem layers remember that these layers later develop into organs to form the organism all right so an enoplastic organism with find this layer which is outside called the ectoderm I've painted in in blue then inside layer is called the endoderm so you can see that in dpop plastic um organisms or animals they've got an ectoderm and an endoderm Ecto meaning that it is an outside layer Endo meaning that it is an inside layer so we've got an ectoderm and an endoderm so here it is but then for a tripop plastic animal we have got another layer between the ectoderm and the endoderm which is called a mesoderm so all of these layers are responsible for developing the organs of an organism yes so later on these will develop and will become an animal an animal just like this little girl here she can came from what she came from these layers as well so it is just explaining that the tissue layers as the were early ones um that develop into organs so let us look at which organs do the tissue layers develop into for example first one is the outer layer which is the ectoderm the ectoderm develops into external organs remember that it is the outer layer so it develops into external organs just like the skin here here is the skin of a human being it developed from the ectom so it means that when this person was a baby when this person was a baby this part this outside part or this part called the um this part called the ectm developed and made the skin and the external organs whereas this endem the part that is inside develops into into the digestive system remember the digestive system is inside it is actually the one that processes your food and stuff like that so the inside layer develops into the digestive system whereas the outside layer develops into the skin and the other outside organisms so it means Diop plastic animals since they've got an Ecto themm and an endo themm only it means that they only have got skin and a digestive system they do not have any other thing besides that remember that now which brings us to the mesoderm the mesoderm develops other organs such as connective tissue such as the bones for example this is the skeleton of a human being so these bones developed from the middle layer called the meso for them to be like this they developed from the meso these blood vessels developed from from the mesem so an animal that does not have a mesem will not develop blood it won't have blood so Diop plastic animals will not form any complex organs because we say that they have got only an ectoderm and an endoderm hence they only have got a skin and the digestive system only and other external organs besides that they won't have blood they won't have any bones so the D Diop plastic animals cannot form complex organisms organs I mean so they are more primitive since they do not have the mesoderm for the development of blood the bones as well as the reproductive organs so Ecto and endoderm are known as primary gem layers meaning that an organism cannot exist without the ectoderm and an endoderm hence we say that even the diploblastic animals have got an ectoderm for the skin and external organs as well as the endoderm for the digestive system whereas the mesoderm is a secondary gem layer so the mesoderm is the one that makes other complex organ organs such as the bones so for example if you take an eorm an earth worm is just something like this here is my eorm here so this earth worm if you see it it has got a skin outside and and uh also it has got some digestive system because it eats so that it can live and stuff so it has got a digestive system but then an eorm does not have bones does not have any other complex organs so it is Diop plastic so it means when it was young when it was still being developed its tissue layers just looked like this it had got an ectoderm as well as an endoderm only so here is an activity that you can use to test yourself out if you didn't understand any other Concepts uh related to this video please make sure that you comment below comment your answers on these activities so that we can see how we can get as much marks as possible and don't forget to subscribe stay tuned for our next video