0:04 Good evening my dear students. How are you all? I hope you all are doing very well. So this is Dr. Anisha from Sri Chaitananya Educational Institutions. Welcome you all for another session of zoologology for NE 2025 bridge course for the aspirants of NE 2027. So here we are students again. Yes, good evening to all of you. Here we are again for another session of zoolology and again we are going to study some of the basic concepts in the animal kingdom. Throughout these courses throughout these days we are studying a lot of new things. We are studying some of the old things also which we are revising in a new way as well as we are studying few of the new things also. Right? I'm very sure you all must be
0:50 knowing that you all are understanding the topics which might give you an upper hand when you actually face the chapters or the exam. So let's start studying again. Take your pen and paper ready and start the topic. What we were studying? We were studying about the animal kingdom. Yes. So animal kingdom here we are. In the animal kingdom we have discussed about the topics like the various film, the layers of the classification, strata of the classification and the various characteristics which divide the organisms into group animal kingdom as well as different animals into different film. So now the basis of classification we were discussing starting with the
1:38 level of organization body symmetry and now we have come till the processes of digestion as well as respiration and circulation. So now so let's start we have studied till the type of vertebrate hearts yesterday. So vertebbrate hearts what all we are going to study today. Yesterday we have discussed about the vertebbrate hearts. How the vertebrae hearts appear in an organism. Now in case of the vertebbrates, if we talk about the vertebrae, the heart is usually the vententral located heart and the heart is divided into either three, two or four chambers. So let's see the
2:23 different patterns of vertebbrate heart. Now the vertebrate heart shows different type of chambers, different types of their partition and different pattern of the circulation of the blood through them. We have studied about the respiratory pigments. I'm very sure you all have studied about the respiratory pigments about the hemoglobin erithrine hemocyanine. These are the different types of respiratory pigments we have discussed their color their the metal ion present and how are they present in the blood. So today we are going to start about the different type of vertebbrate heart. All right. So the vertebbrate heart the first vertebrae heart that we are going to study here
3:11 is today it is the two-chambered heart. So two-chambered heart in which one atria and one ventricle present. This is two-chambered heart called as the heart present in the fishes. So fishes have the twochambered heart. Now in case of the two-chambered heart of the fishes how the blood flows the blood flows in the form of a venus blood. It is the Venus blood that flows through the heart. All right. The Venus blood normally we know the heart receives oxygenated as well as the deoxxygenated blood. In case of the fishes, the heart
3:56 is Venus heart because the deoxygenated blood enters the heart. It gets pumped out and it goes straight to the gills for to the gills for oxygenation. So gills for oxygenation. So that is the two-chambered heart of the fishes. So two-chambered heart of the fishes they pump out venus blood. Remember this two-chambered heart of the fishes they pump out Venus blood. They receive deoxxygenated blood and pump out the deoxxygenated blood which goes to the gills for oxygenation. All right. Now we are
4:42 coming to the three-chambered heart. So this is the three-chambered heart. This is three chambered heart. All right. So what all structures are there? There is right atrium, left atrium and one ventricle. All right. So, right atrium, left atrium and one complete ventricle. This is the three-chambered heart. This is three-chambered heart of the which organisms? Which organisms have the three-chambered heart? It is present in the organisms like the amphibians. The amphibians have three-chambered heart.
5:30 Okay. Amphibians like the frog, like the toad, like the salamander, they have three-chambered heart. Now, how the circulation takes place in case of three-chambered heart? In case of the three-chambered heart, oxygenated blood enters through the right side. The deoxygenated blood enters through the left side and in the v in the ventricle these two blood will undergo intermixing. So there is intermixing of blood. So there is mixed blood in the ventricle. So the ventricle gets the mixed blood mixed with oxygenated and deoxxygenated blood. And
6:17 this mixed blood is then pumped out. It is then pumped out of the it is then pumped out of the ventricle. All right. So it is the deoxxygenated blood as well as the oxygenated blood which is getting pumped out of the heart. So this is the three-chambered heart. This three-chambered heart is present in the amphibians. This type of circulation is called as incomplete circulation. This is called as incomplete circulation. Okay. So this is incomplete circulation. Incomplete circulation.
7:03 Okay. So this is incomplete circulation. we see in the three-chambered heart which is present in the amphibians like frog and toad. Now we are moving on to the four-chambered heart three and a half or four chambered heart. Now this is another type of heart in which the ventricle is not completely separate. So the another type of heart in which the ventricle is not completely separate. See here in this case there is again right atrium the left atrium the ventricle the ventricle is not completely separated. The right and left side of the ventricle
7:48 is not completely separate. So there is incomplete partition of the ventricle. Incomplete partition of ventricle. So this is called as incompletely separated threechambered heart. This is also called as the three-chambered heart. But this is not ventricle completely separate. Incompletely separated ventricle with three-chambered heart. Now which organisms have such type of heart? It is present in the organisms like reptiles. All the reptiles have this heart except crocodile except crocodilia group.
8:35 Except the crocodilia group. Now the crocodilia group crocodilia group includes the crocodile alligator gavalis. These are called as the crocodilia group. So the crocodiles not just single only the crocodile group or the species of crocodile. It includes the alligators also. It includes the gavlis also. So they have except them rest other reptiles they have the chambers which is two right and left atria will be present and another incompletely separate ventricle that is incomplete partition of the ventricles incompletely divided three-chambered heart will be present. Now here the circulation of blood will be again
9:22 through the left side it will be the oxygenated blood through the right side the deoxxygenated blood mostly the deoxxygenated and oxygenated blood goes separately but a very few part of them under goes mixed blood. So most of them they have incompletely separated ventricle. So as a result of which most of the time the blood goes separated the oxygenated blood goes pumped out in a different way and deoxxygenated blood goes pumped out in a different way. But a very few part of them can have a mixed group of blood with oxygenated and deoxxygenated blood both. So that is called as the
10:08 incomplete incomplete circulation again. So they also show the incomplete circulation. But here the incomplete circulation is not same as that of the amphibian because majority of the blood in case of amphibian is mixed blood. Majority of the blood in case of reptilian is not mixed blood. It is separate. Oxygenated deoxxygenated blood are pumped out of the heart separately. Only a few part of the blood is mixed blood. So that is why this is also considered to be incomplete circulation. All right. So such type of blood or such type of such type of chambers of the heart is
10:54 present in the reptiles. Now you must be thinking what about this deoxxygenated blood like if the body is getting deoxxygenated blood what will happen to them in case of amphibian what happens in case of amphibians once this mixed blood is released out of the heart it goes to various parts of the body and it goes to the underlying blood vessels under the skin layer underlying blood vessels receive these blood which causes the diffusion of oxygen directly from the atmosphere through cutaneous respiration. So through the cutaneous respiration these mixed blood gets oxygenated in case of
11:39 amphibians. So amphibians are receiving mixed blood throughout their body but it is not that they are using this mixed blood they are oxygenating the blood with the help of their cutaneous ways of respiration. Okay, in case of the reptiles again the same thing is happening but in a very few form they are receiving this deoxxygenated blood or the mixed blood. So they also have another method of oxygenating the blood. Now we are coming to the very important part of the chambers of the heart which is completely separated chambers present in the heart. This is right atrium, left atrium, right ventricle and left
12:28 ventricle. So all of these chambers are completely separated from each other. They are not at all linked. They are not at all connected. All of these are completely separate from each other. The ventricle is completely separated. And this is complete fourchambered heart. So this is complete fourchambered heart. Now complete four-chambered heart is present in the organisms. Which organisms have complete four-chambered heart? Organisms like the mammals, like the birds and reptiles like crocodiles. Reptiles like crocodile. The crocodilia group.
13:15 reptiles like crocodiles. So they have completely formed fourchambered heart. Now the circulation that is taking place in completely four-chambered heart. How is it taking place? The left atrium is providing the oxygenated blood. The right atrium is receiving the deoxygenated blood. The deoxxygenated blood is getting pumped out of the heart through the right ventricle separately. This is a completely different circuit and the left atrium is providing the oxygenated blood and it is also getting pumped out of the heart separately.
14:01 So both the oxygenated deoxxygenated blood have their own circulatory pathways. Two separate circulatory pathways for oxygenated and deoxxygenated blood. They are not getting mixed at all. So such type of circulation is called as double circulation. As both of them are passing through two different circulatory pathway and it is called as complete double circulation with complete double circulation with pulmonary pulmonary and iotic or
14:46 systemic pathway. pulmonary and systemic pathway. Okay. So this is called as the complete double circulation. In case of complete double circulation there is pulmonary and systemic pathway present. Okay. So that is how there is formation of the heart in different level of the different vertebbrates. In case of the fishes if we see it is two-chambered heart there is only single circulation present. It is called as the single circulation. Single circulation of the venus blood is taking place. So it is the single circulation taking place. In case of the
15:32 incomplete double circulation we can say or mixed circulation we can say in this case of amphibians there is mixing of oxygenated and deoxxygenated blood as a result of which there is incomplete double circulation present. In case of the reptiles there is again incomplete double circulation present in which there is partial mixing of the venus blood and oxygenated blood and this is the double circulation complete double circulation present in the mammals birds as well as the crocodiles like reptiles they have the complete separation of all the chambers as a result of which they
16:17 have separation of oxygenated and deoxxygenated blood to the different parts of the body. The two separate pathways through which the blood flows is called pulmonary and systemic pathway. You will be talking about it or you will be learning about the pulmonary and systemic pathway when you will come to the chapter blood vessels and circulation. So at that time you are going to study them in detail. Now we are coming to the part of nervous system. How nervous system is different in different organisms or different animals. Nervous system is different in case of invertebrates or the primitive organisms like non-cordates and it is well developed or much more developed in
17:04 case of organisms like cordates or vertebbrates. Okay. So let's see what is this nervous system. First of all, the nervous system which divides the organism into two groups. It is with two important characteristic noto cord and nerve cord. Noto cord and nerve cord. Okay. Now howto cord and nerve cord is different in different organisms. In case of the non-corditates, in case of the non-corditates, what happened in case of the non-cordates and what happens in case of the cordates, what differences
17:52 we can see in case of the non-cordates, the nervous system itself, the nervous system itself is which is present ventrally located and in the form of in the form of nerve cords. In the form of nerve cords, noto cord absent. Okay, remember these points. Each of them are very very important. Now what are these points? In case of non-cordates, the nervous system is ventrally located. The nervous system is ventrally located. Where is the
18:37 nervous system of human body present? Just imagine or just think about it. Where is the nervous system of human body present? It is in the dorsal surface. So human body has the nervous system located dorsally. Now the non-cordates if we talk about non-cordidates can be anything can be a flat worm can be a round worm the analids the arropods they all have nervous system which is located ventrally as well as in the form of nerve cords in the form of collection of neurons collection of small nerve- like structures which forms the nerve cords. So in the form of nerve cords they are present and noto cord is absent in them.
19:23 We'll talk about it now what is noto cord. So how is it different in cordates? In case of the cordates the nervous system is dorsally located. Just think about your vertebral column and the spinal cord you will see they are dorsally located. So cordates they have the nervous system dorsally located. Now in the form of nerve cords. Where is it located? In the form of nerve cords. In the form of In the form of both nerve cord and noto cord. So they have nerve cord and noto cord present in them in any part of their life cycle. Now let's
20:10 talk about see this is the primary difference between the nervous system of the non-corditate and cordit. Okay remember this thing this is very very important and you are going to use this concept later also the non-cordates or the invertebrates have their nervous system ventrally located. We the higher organisms the cordates have the nervous system dorsally located. What are the components of the nervous system in the non-cordance? It is made up of nerve cord. Nerve cord is collection of neurons. So those neurons collect together in different forms to form the nerve cord in the non-cordates. In cordates we have non we have this
20:56 nerve cord as well as the noto cord but it is modified in different forms in different stages of life. nerve cord and noto cord modified into various structures also. All right. So let's see what is this notto cord and nerve cord. The notto cord. What is this not cord? Now remember this what is not cord? Notocord is it is a long flexible solid rod like structure. Rodlike structure [Music] originated
21:42 from misodorm originated from misodm. Now I'm very sure you have understood what is ectodom, endodm and misodum. Misodm is the middle germ layer. The third germ layer formed between ectodorm and endodm. So originated from misodum and is located near the dorsal side of the body. Dorsal side of the body. Okay. So that is called as the neto cord. Okay. Okay. Dorsal wat suba you want to
22:28 know what is dorsal and ventral. See dorsal and ventral. I'm very sure most of you can understand what is dorsal and ventral. If not you can see suppose an organism is present. An organism is present. All right. Now the upper part or the hard part of the body is a dorsal surface. In case of an insect, if we take if this is an insect with its legs like this. So this is the dorsal and this is the vententral. In case of human being or in case of any other organism if we take the back portion is the dorsal and the front portion is the vententral side. So that is dorsal and
23:14 vententral. These are the two surfaces of our body. The dorsal and the ventricle. I'm very sure you all must be knowing dorsal and ventral. Even if you don't know, just imagine if you look at an insect, the surface you can see on the surface of of an insect, the upper surface of the insect is the dorsal. The lower part which you cannot see in that insect is the vententral. Similarly in case of human body the back side is the dorsal surface and the front side it is the ventral surface. So that is how vententral and dorsal is differentiated. Now the noto cord is present on the dorsal side of the body like our vertebral column because noto cord is the primitive form of
24:00 the primitive form of primitive form of vertebral column. primitive form of vertebral column in some of the higher organisms. This is the vertebral column which is forming into which is getting formed from the nottoord. So now we are coming back to notto cord. See here in this structure, this is the structure we have. Now in case of this structure, this is the basic diagram of an organism. Maybe it does not look like an organism right now to you. But if you see an organism having the mouth, the digestive system, the circulatory system and other structure, you can see that
24:46 there is the structure called as the noto cord here. This is the noto cord present. All right. Now simplified diagram. If we take suppose this is the body of an organism. Okay. This is the body of an organism. This is the dorsal surface of that organism and this is the vententral surface of that organism. Okay. Now there will be a thick solid rodlike structure present on the dorsal part of the body. This thick solid rod-like structure present on the dorsal part of the body. This is called as the noto
25:33 cord. This is called as noto cord. Now this is not cord present. Notocord in later life forms the vertebral column. Notocord in later life forms the vertebral column. Noto cord is what? It is misodorm originated long flexible rod-like structure. So it is present in case of the cordex only. Non-cordates do not have the structure called as the noto cord. So noto cord it is the long elongated flexible rod solid rod-like structure is the noto cord present on the dorsal part of the body almost like the backbone of the body and later in
26:20 some of the higher organisms noto cord will change into the structure called as vertebral column. Okay. So higher organisms like human body, higher organisms like other mammals, higher organisms like any other organism you can name cow, dog, anything. These are all higher organisms. Lower organisms. Lower organisms can be very primitive fishes which are cordates but they are lower organism. So now these organisms the higher organisms will have noto cord on the dorsal part of their body and the noto cord will later change into vertebral column in their lifetime. So, so what it happens in the embryionic stage or in their developmental stage
27:06 the structure which is present in their body is the noto cord and as they grow inside their embryo as they take a birth when they are born they will change this noto cord into vertebral column. The same thing happens with humans also in our embryionic stage we have this structure called as the noto cord and slowly as we grow inside the placenta slowly this noto cord will be replaced by vertebral column. So this is vertebral column. Vertebral column is what? Vertebral column is the individual vertebra joining together in the form of a column. So that is vertebral column. Yes, the vertebral column provides the
27:53 body a shape, structure, support, strength as well as it performs many function. It helps in the locomotion. It helps in the movement. So all of these are performed by the vertebral column. Vertebral column is originated from the primitive structure called as noto cord. So that is why the organisms with noto cord are called as cordates. Organisms without noto cord are called as non-corditates. Okay. So corded non-corded. Notocord present in any part of their lifetime whether it is embriionic like humans or throughout the lifetime also they are called as cordates. And if they do not have noto cord ever in their life cycle not even
28:40 the laral stage or in the embriionic stage they will be called as non-cordates. Okay. So corded and non-corded two organisms we have seen. Now some of the cordates they change the nottocord into vertebral column and are also called as the vertebbrates. Okay. So some of the organisms in the cordates change the noto cord change the noto cord into vertebral column. change the notto cord into vertebral column and is called as vertebrates they call as vertebbrates.
29:25 So some of the cordates are also called as vertebbrates. All right. Okay. So non-cordates and cordates here we have seen what is not cord. Now another important similarly equally important word is the nerve cord. So here we are again with the word nerve cord. We heard we learned about the noto cord. Noto cord is the primitive vertebral column which provides the strength of the embryo as well as presence of the notto cord makes the organism corded. Absence makes it non-corded. Notto cord is misodermal origin. Now we are coming to the part which is called as nerve cord.
30:12 This is again very very important. So here we are again in this diagram. Okay. See here this diagram again we have seen this diagram similarly while explaining the noto cord. The dorsal surface has this structure called as the notto cord. Okay. Let's see what is cord and how they are related. This is the noto cord. All right. This noto cord is going to be in future the vertebral column also. Now just on the surface or towards the dorsalmost part of the body there is one more hollow structure is present. Okay. So this hollow dorsally located
30:58 structure this hollow dorsally located structure this hollow dorsally located structure is called as the nerve cord. So what are the characteristics of nerve cord? Where is nerve cord located? You all can see here just dorsal to the noto cord. Dorsal to the if notto cord is almost on the dorsal side. Dorsal side even more dorsal to the noto cord is the structure present which is called as nerve cord. Now what is nerve cord? Nerf cord is hollow dorsal made up
31:45 of nerve cells. Made up of nerve cells. Okay. So dorsal hollow and made up of nerve cells. This structure is called as the nerve cord. So nerve cord and noto cord. I will tell you how they are related. Nerve cells dorsally hollow located. This structure is the nerve cord. It is dorsally located dorsal most. And they are hollow. They are not solid like the noto cord. It is a hollow elongated tube most dorsal to the body. That is called as the nerve cord. Now the thing is the nerve cord in future produces the structure called as spinal cord and the brain. brain and spinal cord is formed
32:33 from this nerve cord. Now imagine and tell me which structure of our body is going to be the nerve cord. Then if we have noto cord as the vertebral column then which structure is going to be the nerve cord. The nerve cord in future becomes I want to answer from each and every one of you. Think of it and answer me. The nerve cord will be changed into yes tell me tell me tell me who is going to answer first of all the n chord is going to change into I'll just give you 3 minutes answer me the structure which is changing into the nerve cord in
33:20 our body if the noto cord is our vertebral column if the noto cord is the vertebral column vertebral column is enclosing the structure called as the spinal cord. So this spinal cord and the brain. Yes, excellent answer Shakuntala CNS. The central nervous system. Absolutely right. Brain and the spinal cord. Yes, spinal cord and brain. Spinal cord and brain is obtained from the nerve cord which is the part of central nervous system. The noto cord encloses the see here the noto cord when it is going to become a vertebral column. the noto cord or the vertebral column will enclose completely the nerve cord or the spinal cord and the anterior part of the spinal cord will swell up and changes
34:07 into the structure called as brain. So that is how brain and spinal cord is formed in case of vertebbrates. So this is about the nervous system of the cordate and non-cordate. So here spinal cord and brain is obtained from the nerve cord. Which origin is this? Which germ layer helps in the origin of the nerve cord? Nerf cord is ectoermal in origin. Ectodermal in origin. The nerve cord is ectoermal in origin. From the ectodorm of the jumblus nerve cord is originated. So this is the basic difference of the nervous system in a cordate and a non-cordate. In case of the cordate there will be notocord and nerve cord present and in the higher
34:53 organisms like the vertebbrates noto cord will change into vertebral column nerve cord will change into spinal cord and brain and they form the complete nervous system and the skeletal system of the body in case of non-cordates. Now we have seen about the cordates. What happens in case of the non-cordates? For example, if you take an example of a flat worm. Okay? If you take an example of a flat worm like this, this is a flat worm. Pleneria. This is a flat worm. Platty helm means pleneria. Okay. So, what type of this is just an example. Almost all the
35:39 organisms have this structure. So if we see the organism to be if this is an organism if this is the structure of an organism the nervous system will be located in case of non-corditate is ventral. So here is the nervous system located in case of non-cordates. Non-cordates have ventrally located nervous system. So non-corded nervous system. nervous system in case of non-corded it is the ventrally located ventrally located nervous system. All right. Now the nervous
36:26 system is ventrally located in case of the non-cordates and how are they appearing? How they appear? They appear in the form of double vententral nerve cord which are connected transversely like this. Which are connected transversely like this. Here structure like this. All right. So how do they appear? See how do they appear here? They have two ventrally located two or double
37:13 vententral nerve cord or two nerve cords. Two double vententral nerve cord which are connected by transverse nerves which are connected to each other by transverse nerves. Remember these things clearly or study these things properly because you are going to use these components the use these concepts exactly while you will be studying each and every film separately. All right. So read them properly. In case of the flatworms or the analides or the arropods, they have this vententral nerve cord or the double vententral nerve cord which are connected to each other like this with the help of
37:59 transverse nerves. They are all ventrally located. The nervous system in case of non-cordate is ventrally located. The nervous system in case of the cordates dorsally located. Cordates have no cord and nerve cord. They have double they have only the nerve cord which is definitely not solid. They are double and ventrally located connected to each other with the help of these transverse nerves. So this is the basic difference between the nervous system of the cordates and non-cordates. Okay. Now here we are again to another type of the characteristics that differentiates between different film of the animal kingdom that is the reproductive system.
38:46 Yes, reproductive system we have studied earlier also about the reproductive system we have studied which is monicious and which is dashious or what are they how do they defined as and what are the different examples. We have also studied about the external and internal fertilization. I'm very sure you all remember these terminologies. Monacious. I have given you a trick also to remember them. Monacious in a single body two reproductive organs or two types of reproductive system will be present. So they are also called as bisexual. All right remember it dio2. So in case of diocious organism they are commonly called as
39:32 unisexual because two separate bodies or two separate individuals showing the different reproductive system male reproductive system in male female reproductive system in females. So monicious and dashes terminologies we use we use the terminologies of external and internal fertilization. If the fertilization is taking place inside the female body, inside the female body, if the fertilization is taking place, it is the internal fertilization. And if the fertilization is taking place outside the female body, it will be called as the external
40:19 fertilization. And we are now going to study about the development. There are different types of development. What are the different types of development present? Now different types of developments are present because the basic terminologies of reproductive system we already have studied. Now we are going directly to the different types of development. Development are of two types. direct development and indirect development. Now what is a direct and a indirect development? What is it going to be? Direct and indirect development. In case of direct development, what happens in case of direct development?
41:06 There is no laral stages present. No laral stages present during the development of an organism. The organism develops into from the fertilized egg into an adult form directly without undergoing any changes without undergoing any intermediate stage directly into an organism. Okay. So that is called as the direct development. when they are not showing any laral stages. The young organism that has come out of the fertilized egg looks the miniature form of its adult structure. The miniature form of the adult structure. For
41:52 example, a human body. A human body when a human child is born, it is just the miniature form of an adult structure. They do not develop wings. They do not develop any extra structure. It is just the miniature or pre or we can say the smaller form of an adult organism. They have the same two hands, two legs, same type of body structure, similar type of body organization. Whereas in case of indirect development, different laral stages will be present. Different laral stages are present in case of indirect development. So what happens in case of the indirect development? In case of indirect development, the fertilized
42:39 egg, if this is the fertilized egg, the fertilized egg will first change into a structure called as the larvae. Later it will change into a structure called as the pupa and then it changes into an young organism. It changes into young organism. The larvae and pupa are structurally or physiologically different from the young organism. That is called as indirect development. When the egg changes into a different organism, later it develops wings. Later the feeding habit changes, the staying habit changes and slowly it under goes
43:25 further more changes and finally it changes into a young organism. Such type of development is called as indirect development and these changes these changes are called as metamorphosis. This is called as metamorphosis. What is metamorphosis? Gradual change. If you need to know what is metamorphosis, it is the gradual change from gradual change from an egg to an adult organism. It is called as metamorphosis.
44:14 Now metamorphosis we have to study in detail because metamorphosis these concepts and these important questions are asked in the neat exam also and it is there in your syllabus also. So about metamorphosis we are going to study tomorrow for our class. We will be discussing about the types of metamorphosis and the different type of organisms showing the different types of metamorphosis. So read about the today's classes. We have discussed about the different types of heart and circulatory system. We have discussed about the different patterns of the nervous system present in cordit and non-cordit and the reproductive pattern. We will be discussing tomorrow about the metamorphosis and many other topics. So thank you everyone. Read well, study
45:00 well. All the best. Thank you.
