Class11 Biology Animal Kingdom Session 6

2. Chapter 4
Animal Kingdom
Basis of Classification
Lecture no.1

3.  Basis of Classification
 Phylum Porifera
 Phylum Coelenterata
 Phylum Ctenophora
 Phylum Platyhelminthes
 Phylum Aschelminthes
 Phylum Annelida
 Phylum Arthropoda
 Phylum Mollusca
 Phylum Echinodermata
 Phylum Hemichordata
 Phylum Chordata

4. Kingdom Animalia
 Absence of cell wall
 Heterotrophic mode of nutrition
 Reserve food as glycogen
 Locomotion is present
 Show quick response to external
stimuli
 They are multicellular and Eukaryotic

5. Basis of Classification
The various features for classification of living
organisms are as under:
 Level of Organization
 Symmetry
 Germ layer
 Coelom
 Segmentation
 Notochord

6. 1.Level of organization
 Cellular level
 Tissue level
 Organ level
 Organ system

7. In sponges, the cells are arranged as loose cell
aggregates, i.e., they exhibit cellular level of
organization.
Cellular level
Porifera

8. 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 organization.
Tissue level
Coelenterates

9. Organ level is exhibited by members of Platyhelminthes and other higher
phyla where tissues are grouped together to form organs, each specialized
for a particular function.
Organ Level

10.  Echinoderms and Chordates, organs have
associated to form functional systems, each
system concerned with a specific physiological
function. This pattern is called organ system
level of organization.
 Organ systems in different groups of animals
exhibit various patterns of complexities.
 For example, the digestive system in
Platyhelminthes has only a single opening to
the outside of the body that serves as both
mouth and anus, and is hence called
incomplete.
 A complete digestive system has two
openings, mouth and anus.

11. Circulatory System
Open Closed
In this type the blood is pumped
out of the heart and the cells and
tissues are directly bathed in it
e.g. Arthropoda
In this type the blood is
circulated through a series of
vessels of varying diameters
(arteries, veins and
capillaries) e.g. Mammals

12. Symmetry
2.Symmetry
Symmetry refers to a correspondence of body parts, in
size, shape, and relative position, on opposite sides of a
dividing line or distributed around a central point or axis
Asymmetrical Radial
symmetry
Bilateral
Symmetry

13. Asymmetrical
Any plane that passes through the center does
not divide them into equal halves. e.g. Sponges
Radial Symmetry
When any plane passing through the central axis of
the body divides the organism into two identical
halves, it is called radial symmetry. e.g.
Coelenterates, ctenophores and echinoderms
Bilateral Symmetry
Where the body can be divided into identical
left and right halves in only one plane, exhibit
bilateral symmetry. e.g. annelids, arthropods
Radial Symmetry
Bilateral Symmetry

14. 3.Germ layer
A germ layer is a group of cells in an embryo that interact with each other as
the embryo develops and contribute to the formation of all organs and tissues.
All animals, except perhaps sponges, form two or three germ layers. The germ
layers develop early in embryonic life, through the process of gastrulation.
Germ Layer
Diploblastic Triploblastic

15. Diploblastic Organization
 These type of animals has two germ layers
 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.
 These type of animals has three germ layers
 Those animals in which the developing embryo
has a third germinal layer, mesoderm, in
between the ectoderm and endoderm, are called
triploblastic animals e.g. Platyhelminthes and
chordates.
Triploblastic Organization

16. Image credit NCERT

17. 4.Coelom
The body cavity, which is lined by mesoderm is called coelom
Coelom
Coelomates Pseudo coelomates Acoelomates
Animals possessing coelom
are called coelomates, e.g.,
annelids, molluscs,
arthropods, echinoderms,
hemichordates and
chordates
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. Such a body cavity is called
pseudo coelom and the animals
possessing them are called pseudo
coelomates, e.g., aschelminthes
The animals in which the
body cavity is absent are
called acoelomates, e.g.,
Platyhelminthes

18. Image Credit NCERT

19. 5.Segmentation
Segmentation is the serial repetition of similar organs, tissues, cell
types or body cavities along the anterior-posterior axis of bilaterally
symmetric animals
Segmentation
Metameric Superficial
In some animals, the body is externally
and internally divided into segments with
a serial repetition of at least some organs.
The body which shows this pattern are
called metameric segmentation and the
phenomenon is known as metamerism.
In some animals segmentation is
only externally not internally. e.g.,
Platyhelminthes

20. 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.
Image credit NCERT

21. Classification of Animals
Source NCERT

22. 1. The body cavity formed by the splitting of the
mesoderm is called
(a) pseudocoelom
(b) coelom
(c) haemocoel
(d) blastocoe
(b) coelom
MCQ

23. 2. Which of the following level of organization is
found in coelenterates?
(a) cellular
(b) tissue
(c) organ
(d) organ system
(b) tissue

24. 3. The tapeworm takes its food by
(a) suckers
(b) mouth
(c) scolex
(d) skin
(d) skin

25. 4. Chordates may not have a
(a) vertebral column
(b) dorsal nerve cord
(c) gill slits
(d) notochord
(a) vertebral column