Animal kingdom

Introduction :    

              All animals are multicellular, Eukaryote, having heterotrophic mode of nutrition animals are holozoic that means they take food to an opening called mouth, either in solid or liquid form. Can you imagine that these organisms, varying from sponges to sharks, ants to whales, earthworms to anacondas, all belong to the same group, i.e. Kingdom Animalia. They all are animals. Now what are animals? What are the basic features which decide that the organisms belongs to Kingdom Animalia? You will be able to answer all these queries after studying and by carefully thinking on the basic features of animals, the criteria of their classification and their differences among themselves.        

Fundamental character or Basic character:

          On the basis of these character animals are classified into eleven phylum these characters are:

1.     Levels of organization

2.     Pattern of complexity of system

3.     Germinal layers

4.     Body plan

5.     Segmentation

6.     Symmetry

7.     Notochord

8.     Coelom (Body Cavity)

1.     Levels of organization: - It explain is that how the cells are arranged in body. Animals have different level of organization.

                        I.            Cellular level: - Cells are arranged in loose groups and perform different functions. Ex. Poriferans.

                     II.            Tissue Level: - Similar functions performing cells organized to from tissue.          Ex. Coelenterates, ctenophorans.

                 III.            Organ Level: - Similar functions performing tissue organized to form organ.        Ex. Platyhelminthes.

                 IV.            Organ System level: - Similar functions performing (relative to one another) organs    organized to form a functioned system called organ system. Ex. Aschelmithes to chordata.

2.     Pattern of complexity of system: - As we increase in phylum the complexity of sytem increases.

I.                  Circulatory System: - Consist heart, blood & blood vessel.

Open Circulatory System	Closed Circulatory System
1.     Sinus ( Blood filled space) present 2.     Capillary absent	1.     Sinus absent 2.     Capillary are present i.e. this type of circulatory system has blood vessel of variable diameter.

                      

1.     Poorly developed blood supply 2.     Low blood pressure 3.     Organs are in indirect contact of blood Ex. Arthropods, Hemichordates, Non-Cephalopods mollusk, Annelids (Leech), Urochordates/tunicates.

1.     Well-developed blood supply. 2.     High blood pressure. 3.     Blood is always present inside blood vessel. Ex. Chordates, Annelids, Cephalopods mollusc.

II.                  Digestive System: - Consist alimentary canal.

Incomplete Digestive System	Complete Digestive System
Alimentary canal consist a single opening from there food enters and undigested food out. Ex. Coelenterates, Ctenophores, Platyhelminthes.	Two separate opening called mouth and another called anus. Ex. Aschelminthes to chordates.

 III.                  Reproductive System: -

Male (Sperm)       +   female (ovum)    -->   Zygote    -->  Morula   -->   Blastula -->  Gastrula     --> Embryo

Embryo: -

i.                   Direct development

ii.                 Indirect development:- embryoàlarva à offspring

                                                          

1.     Germinal Layer: - These layer are made up of cells which lead to the formation of various structure of body. These are:

a)    Ectoderm ( outer most layer)

b)    Mesoderm(middle layer)

c)     Endoderm(innermost layer)

Diploblastic organisms	Triploblastic organisms
Two germinal layers are present i.e. outer ectoderm and inner endoderm Which are connected by undifferentiated non- cellular jelly like layer called mesoglea. Ex. Coelenterates, ctenophores. (sponges are not true diploblastic)	These animals have three germinal layers i.e. outer ectoderm, middle mesoderm, and inner endoderm. Ex. Platyhelminthes to chordates.

2.     Body plan: - three type of body pan found in animals.

a)    Cell aggregated body plan: - cells are arranged in loose form and these cells perform different functions i.e. some division of labor is present ex. Poriferans.

·        If the body of sponge is crushed and cells are captured in culture media or nutrient media these cells collected to form sponge i.e. the remaining part of the body use the culture media for formation of the remaining part of the body.

b)    Blind Sac body plan: - Body consist only one opening called mouth for ingestion and egestion of food ex. Coelenterates, ctenophores and Platyhelminthes.

c)     Tube within tube body plan: - separate opening for ingestion and egestion of food.

Blastopore:- the first opening form in embryo is called blastopore which is the opening of archenteron (form alimentary canal)

Protostome	Deuterostome
Blastopore form mouth ex. Aschelminthes, Annelids, Arthropods, and Molluscs.	Blastopore form anus Ex. Echinodermates, hemichordates and chordates.

3.     Segmentation: - means the division of body into small segments and if the structure are repeated in segments it is metameric segmentation and each segment is called metamere. On the basis of the segmentation animals are :

a)    Truly segmented or metameric segmentation: - segmentation present at both adult and embryonic stage. It may be only external (Arthropods), only internal(chordates), and both external and internal(Annelids)

b)    Psedosegmentaiton: - segmentation present only in adult (external only) but absent in embryo. Ex. Tapeworm (flatworm).

c)     Unsegmented body: - Segmentation absent in both adult and embryonic stage. Ex. Poriferans, coelenterates, ctenophores, most of flatworms, round worms, mollusks, echinodermates and hemichordates.

4.     Symmetry:- It defines the body condition and the basis of symmetry.

a)    Asymmetrical: - the body of these animals cannot be divided into two equal half in any plane. For ex. Most of the sponges and gastropod mollusks.

b)    Radial symmetry: - the body of animal is divided in two half by passing many plane from center region or central axis. For ex. Coelenterates, ctenophores.

·        Adult echinodermates-pentamerous radial symmetry (starfish)

·        Radial symmetry is advantageous for non-motile or sessile or sedentary animals, so that they are gather food from all directions.

c)     Biradial symmetry: - the body of animal is divided in two equal half by passing two vertical plane, Ex. Sea Anemone (coelenterates).

d)    Bilateral Symmetry: - As the animals start movements on ocean floor through on the anterior end-head is formed; this is called cephalization. Head consists of eyes, mouth, various sensory organs, and brain.

The body of these animals is divided in two equal half by passing only one plane i.e. sagittal plane. Ex. Platyhelminthes to chordates except adult of echinodermates and gastropod mollusks.

5.     Notochord: - A flexible, solid rod like structure which originate from mesoderm present on dorsal surface of body but ventral to nerve chord. On the basis of this ; animals are divided into

a)    Chordates: -having notochord ex. Chordates

b)    Non- chordates don’t have notochord ex. Poriferans to hemichordates

6.     Coelom: - A cavity present in body, which is lined by mesoderm from all the sides. On the basis of coelom animals are:

a)    Acoelomate: - coelom is absent.

b)    Pseudocoelomate: - mesoderm is present in the form of pouches

c)     Eucoelomate: - these animals have true coelom.

Acoelomate diploblastic	Acoelomate triploblastic	Pseudocoelomate	Schizocoelomate	Entercoelomate
mesoderm & coelom absent ex. Coelenterates, ctenophores	Mesoderm present but solid, coelom absent. Ex Platyhelminthes	Mesoderm in the form of pouches, pseudocoelom formed due to retention of blastocoel. Ex Ashelminthes.	Formed due to splitting of mesoderm. Ex. Annelids arthropods, and mollusks	Formed due to scattering of mesoderm in the form of pouches ex. Echinodermates,hemichordates, chordates.

Peritoneum: - mesodermal lining of coelom is peritoneum.

·        The animal having open circulatory system have haemocoel in which coelom is filled with blood.

·        While the animals having closed circulatory system coelom is filled with coelomic fluid.

Metazoa: - this term is used for animal.

a)     Parazoa: lack tissues ex. Porifera.

Eumetazoa: these animals have tissues, organ, and organ system. Ex. Coelentrates to chordates.

Five kingdom classification: -
Given by R. H. Whittaker in 1969. He classified the organisms into five kingdom on the basis of the fundamental characters: -

Character	Monera	Protista	Fungi	Plantae	Animalia
Body organisation	Unicellular	Unicellular	Multicellular	Multicellular	Multicellular
Cell structure	Prokaryotic	Eukaryotic	Eukaryotic	Eukaryotic	Eukarotic
Mode of nutrition	Autotroph or heterotroph	Autotroph or heterotroph	Saprozoic(take food from dead & decaying matter)	Autotroph (synthesis their own food)	Heterotroph(take food directly or indirectly from plants i.e. herbivores and carnivores)

On the basis of fundamental character kingdom Animalia is further classified into 11 phylum.

1.     Porifera (sponge)

2.     Coelentrata (hydra)

3.     Ctenophore (comb jellies)

4.     Platyhelminthes (flat worm)

5.     Aschelminthes/ nemathelminthes / nematoda (round worm)

6.     Annelida (earthworm, leech)

7.     Arthropoda (insects) largest phylum

8.     Mollusca (octopus) 2^nd largest phylum

9.     Echinodermates (star fish)

10.                        Hemichordates (tongue worm)

11.                        Chordate (fish, amphibian, reptiles, bird, mammals)