Animal Kingdom Lecture Notes 2025 PDF

# YAKEEN 2.0 FOR NEET 2025 - Lecture 1: ZOOLOGY ## ANIMAL KINGDOM - By Samapti mam ### Topics to be covered: 1. BASIS OF CLASSIFICATION 2. --- 3. --- 4. --- ### Animal Kingdom (Kingdom Animalia / Metazoans) * Multicellularity * Heterotrophic (type of nutrition) * Dependent on others, directl...

# YAKEEN 2.0 FOR NEET 2025 - Lecture 1: ZOOLOGY ## ANIMAL KINGDOM - By Samapti mam ### Topics to be covered: 1. BASIS OF CLASSIFICATION 2. --- 3. --- 4. --- ### Animal Kingdom (Kingdom Animalia / Metazoans) * Multicellularity * Heterotrophic (type of nutrition) * Dependent on others, directly or indirectly for food. * Holozoic mode of Nutrition * Complete food ingest then Digestion * Locomotion * Reproduction ### (Kingdom Animalia) (Metazoans) - Subkingdom Parazoa (CELLULAR AGGREGATION) - Primitive Metazoa - PHYLUM PORIFERA (sponges) - Cellular aggregation - 1 - 10 Non Chordate - Subkingdom Eumetazoans - True Organ System - Tissue → Organ → Organ system - 2 Phylum Coelentrata / Cnidaria - 3 Phylum Ctenophora - 4 Platyhelminthes - 5 Aschelminthes / Nematoda / Nemathelminthes - 6 Annelida - 7 Arthropoda - 8 Mollusca - 9 Echinodermata - 10 Hemichordata - 11 Chordata ### Basis of Classification #### Level of Organisation (LOO) * Cellular grade of organisation: Only cells are present. * Eg. *Porifera* * Digestion * Respiration * Tissue grade of organisation: Group of similar cells form tissue. * Eg. *Coelentrata, Ctenophora* * Tissue * Organ grade of organisation: Tissue organised as Organ. * Eg. *PLATYHELMINTHES* #### Organ System grade of Organisation: Organ organised as Organ System * Eg. Aschelminthes upto Chordata #### Symmetry * Asymmetrical: Any plane passing through the centre of an animal's body can't divide it into equal halves. * Eg: Mostly *PORIFERA* * Radially symmetrical: Body can be divided into equal halves, passing through centre from more than one plane. * Eg: *Coelentrata, Ctenophora, Echinoderm ADULT* * Bilaterally symmetrical: Body can be divided into equal halves passing through only ONE PLANE. * Eg: *Platyhelminthes upto Chordata (Echinoderm LARVA)* #### Germ layer * Sperm + Ovum → Zygote → 2 celled → 4 → 8 - 16 celled (Morula) → Blastula → Gastrula → GERM LAYERS #### Germ Layer * Diploblastic animals: Animals in which their embryonic life shows 2 germ layers. * Primitive Gut * TS of embryd * Ectoderm (outside): not form anything * Mesoglea (jelly like, undifferentiated, non-cellular layer) * Endoderm (inside) * Eg: *Coelentrata, Ctenophora* * Triploblastic animal: Animals in which embryonic life shows 3 germ layers * TS of embryd. * Ectoderm (outside) * Mesoderm (middle) * Primitive Gut * Endoderm (inner) * Eg: *Platyhelminthes upto Chordate* #### Coelom (Body Cavity) * Coelom: Is the body cavity lined by mesoderm on both sides, to accomodate organs (Eucoelomate) * Gut (endoderm) * Body wall (ectoderm) * Coelom * Ectoderm * Mesoderm * Mesoderm split * Gut * Mesoderm * Eucoelomate: Annelida upto Chordate ### 4.1 Basis of Classification #### 4.1.1 Levels of Organisation Though all members of Animalia are multicellular, all of them do not exhibit the same pattern of organisation of cells. For example, in sponges, the cells are arranged as loose cell aggregates, i.e., they exhibit the cellular level of organisation. Some division of labour (activities) occur among the cells. In coelenterates, the arrangement of cells is more complex. Here the cells performing the same function are arranged into tissues, hence is called tissue level of organisation. A still higher level of organisation, i.e., organ level is is exhibited by members of Platyhelminthes and other higher plyla where tissues are grouped together to form organs, each specialised for a particular function. In animals like Annelids, Arthropods, Molluscs, #### 4.1.2 Symmetry Animals can be categorised on the basis of their symmetry. Sponges are mostly asymmetrical, i.e., any plane that passes through the centre does not divide them into equal halves. When any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry. Coelenterates, ctenophores and echnoderms have this kind of body plan (Figure 4.1a). Animals like annelids, arthropods, etc., where the body can be divided into identical left and right halves in only one plane, exhibit bilateral symmetry (Figure 4.1b). #### 4.1.3 Diploblastic and Triploblastic Organisation Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g., coelenterates. An undifferentiated layer, mesoglea, is present in between the ectoderm and the endoderm (Figure 4.2a). #### 4.1.4 Coelom Presence or absence of a cavity between the body wall and the gut wall is very important in classification. The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates (Figure 4.3a). In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. A body cavity like this is called psedocoelom and the animals possessing it are called psedocoelomates, e.g., aschelminthes (Figure 4.3b). The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes (Figure 4.3c). #### 4.1.5 Segmentation In some animals, the body is externally and internally divided into segments with a serial repetition of at least some organs. For example, in earthworm, the body shows this pattern called metameric segmentation and the phenomenon is known as metamerism. #### 4.1.6 Notochord Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and those animals which do not form this structure are called non-chordates, e.g., porifera to echinoderms. ### 4.2 CLASSIFICATION OF ANIMALS | Kingdom | Levels of Organisation | Symmetry | Body Cavity or Coelom | Phylum | |---|---|---|---|---| | Animalia (multicellular) | Cellular level | Mostly asymmetrical | Acoelomata | Porifera | | | | | | Coelenterata (Cnidaria)| | | | | | Ctenophora | | | Tissue / Organ / Organ System | Radial | Acoelomata | Platyhelminthes | | | | | Without body cavity (acoelomates) | Aschelminthes | | | | | With false coelom (pseudocoelomates) | Annelida | | | | | | Arthropoda | | | | | | Mollusca | | | | Bilaterial | With true coelom (coelomates)| Echinodermata | | | | | | Hemichordata | | | | | | Chordata | *Echinodermata exhibits radial or bilateral symmetry depending on the stage. **Figure 4.4 Broad classification of Kingdom Animalia based on common fundamental features** # THANK YOU