Notes "Animal Kingdom"
Notes "Animal Kingdom"
By:- Nagraj Sir
Animals are multicellular and heterotrophic organisms without cell wall and chlorophyll.
Kingdom Animalia includes
11 major phyla:
1. Porifera 7. Arthropoda
2. Cnidaria 8. Mollusca
3. Ctenophora 9. Echinodermata
4. Platyhelminthes 10. Hemichordata
5. Aschelminthes 11. Chordata
BASIS OF CLASSIFICATION
1.
Levels of organization
a.
Cellular level of organization: Here, the cells are arranged as loose cell aggregates. E.g.
Porifera.
a. Tissue level of organization: Here, the cells are arranged
c. Organ level of organization: Here, tissues are arranged into organs. E.g. Higher animals (Platyhelminthes to chordates).
d. Organ system level of organization: Here, organs are associated to organ system. Each system performs a specific physiological
function. E.g. Higher animals. Organ systems of various animals
show complexities. E.g. Digestive system is 2 types:
o Incomplete: It has only a single
opening that acts as
mouth & anus.
Seen in Cnidaria
and Platyhelminthes.
o
Complete: It has 2 openings (mouth
& anus).
Circulatory system is 2 types: open & closed.
2. Body symmetry
It is the arrangement of similar bodyparts on 2 sides
of main axis of the body.
Based on symmetry, animals are 2 types: Asymmetrical and Symmetrical.
a. Asymmetrical: Here, body cannot be divided into 2 equal
halves.
E.g. Most Poriferans, Snails etc.
b.
Symmetrical: Here,
body can be divided into 2 equal halves. It is 2 types.
Radial
symmetry: Here, body can be divided into 2
equal halves in any vertical plane along
central axis (oral-aboral axis) of
the body. E.g. some Poriferans, Cnidarians, Ctenophores and Echinoderms
(adult).
Bilateral symmetry: Here, body can be divided into
right & left halves
in only one plane.
E.g. Platyhelminthes to
Chordata (except adult Echinodermata).
The body of bilaterally symmetrical animal has a dorsal side (upper), a ventral side (lower), left & right lateral sides, anterior (cephalic) side and posterior (anal or tail) side.
3. Germinal layers (Embryonic layers)
These are layers of embryo from which all the body organs are formed. Based on the number of germ layers, animals are 2 types- Diploblastic and Triploblastic.
a. Diploblastic animals: 2 germ layers- outer ectoderm and inner endoderm. In between these layers, an undifferentiated jelly-like layer called mesoglea is present. E.g. Cnidaria & Ctenophora.
b.
Triploblastic animals: 3 germ layers- Outer ectoderm, middle mesoderm and inner endoderm. E.g.
Platyhelminthes to Chordata.
4.Coelom (body cavity)
It is the cavity lined by
mesoderm. It is seen between body wall and gut wall. Coelom separates the muscles of gut and body wall.
Based on the nature of coelom, animals
are 3 types:
a.
Acoelomate: No
coelom. The space between body wall and digestive cavity is filled with matrix (parenchyma).
E.g.
Porifera to Platyhelminthes.
b.
Pseudocoelomate: False coelom.
Here, the body cavity is not lined by mesoderm. Mesoderm is
scattered pouches.
E.g. Aschelminthes.
c.
Coelomate: True
coelom. Here, the coelom arises from the mesoderm. Coelom is lined by
peritoneal layer and filled with coelomic fluid. E.g. Annelida to Chordata.
Functions of coelom:
It accommodates visceral
organs.
Coelomic fluid reduces friction between visceral organs. It acts as shock absorber.
5. Metamerism (segmentation)
It is the phenomenon in which the body or organs is externally and internally divided into repeated segments (metameres). E.g. Annelids (earthworm etc.), Arthropods.
6. Notochord
It is a mesodermally derived supporting rod formed on the
dorsal side during embryonic development in some animals. Animals with notochord are called
chordates and those without
notochord are called non-chordates.
|
Features |
Porifera (Sponges) |
Cnidaria (Coelenterate) |
Ctenophora (Comb jellies or Sea walnuts) |
|
Grades of organization |
Cellular |
Tissue |
Tissue |
|
Symmetry |
Asymmetrical. Some
are radial. |
Radial |
Radial |
|
Germ layers |
- |
Diploblastic |
Diploblastic |
|
Coelom |
Acoelomate |
Acoelomate |
Acoelomate |
|
Habit and habitat |
Aquatic (mostly marine). Sedentary. Solitary/colonial. |
Aquatic (mostly marine). Sessile/free swimming. Solitary/colonial. |
Exclusively marine. Solitary & pelagic |
|
Digestive system |
Absent. Intracellular digestion. |
Incomplete. Intracellular &
extracellular digestion. |
Incomplete. Intracellular and extracellular digestion. |
|
Respiratory system |
Absent |
Absent |
Absent |
|
Circulatory system |
Absent |
Absent |
Absent |
|
Reproduction |
Asexual (fragmentation) &
Sexual. Hermaphrodite. Internal
fertilization. Development is indirect. |
Polyp reproduces asexually (budding) and medusa sexually. Most are separate sexes. External fertilization. Development is indirect. |
Only Sexual. Hermaphrodite. External fertilization. Development is indirect. |
|
Unique features |
Water canal
(water transport) system. Millions of ostia
(pores). Spongocoel & canals are lined
with choanocytes (collar cells).
Body is supported by spicules and spongin fibres. |
Tentacles with cnidoblasts. Gastro-vascular
cavity (coelenteron) with an opening (mouth) on hypostome. Polyp & Medusa forms are seen. Some shows
alternation of generation. Corals have skeleton (CaCO3). |
Locomotion is by 8
vertical external rows
of ciliated comb plates. Tentacles present.
Shows Bioluminescence. |
|
Examples |
Sycon (Scypha), Spongilla (fresh water sponge), Euspongia (Bath sponge) |
Hydra,
Obelia, Aurelia, Physalia (Portuguese
man of war), Adamsia (Sea-anemone), Pennatula (Sea pen), Gorgonia (Sea
fan), Meandrina (Brain coral) |
Ctenoplana, Pleurobrachia |
1.
Water canal
system: Here, water enters through
minute pores (ostia) in the body wall into a central
cavity (spongocoel), from where it goes out through osculum. Canal system is used for food gathering, gas exchange and removal of wastes.
2.
Hermaphrodite (Monoecious): Male and female sex organs are seen in same individual.
3. Tentacles: Finger-like structures which surrounds the mouth of coelenterates. Used for food capture &defense.
4. Cnidoblasts (Cnidocytes): These are stinging cells (present on the tentacles
and the body) with a poison-filled capsule
called
nematocyst. Cnidoblast is used for anchorage,
defense and to capture
prey.
5. Polyp & Medusa: 2 types of body forms incnidarians.
Polyp is tubular
attached asexual form, with upwardly
directed mouth &
tentacles. E.g. Hydra, Adamsia.
Medusa is umbrella like, free-swimming sexual form, with downwardly directed mouth & tentacles. E.g. Aurelia (Jelly fish).
6. Alternation of generation (Metagenesis): The phenomenon in which polyps produce medusae asexually and medusae form the polyps sexually. E.g. Obelia.
7. Bioluminescence: It is the property of some animals to emit light from the body.
|
Features |
Platyhelminthes
(Flatworms) |
Aschelminthes
(Roundworms) |
Annelida (Segmented or Ringed
worms) |
Arthropoda
(Joint-legged animals) |
|
Grades of organization |
Organ &
Organ system |
Organ system |
Organ system |
Organ system |
|
Symmetry |
Bilateral |
Bilateral |
Bilateral |
Bilateral |
|
Germ layers |
Triploblastic |
Triploblastic |
Triploblastic |
Triploblastic |
|
Coelom |
Acoelomate |
Pseudocoelomate |
Coelomate |
Coelomate |
|
Habit and habitat |
Mainly aquatic.
Endoparasites. Some are free-living. |
Aquatic and terrestrial. Free living or parasitic in plants
& animals. |
Terrestrial, fresh water or marine. Free living or parasitic. |
Cosmopolitan |
|
Digestive system |
Incomplete |
Complete. Tubular alimentary canal with well-developed muscular pharynx. |
Complete |
Complete |
|
Respiratory system |
Absent |
Absent |
Cutaneous respiration. Some have branchial (gill) respiration. |
Gills/ book
gills/ trachea/book lungs |
|
Circulatory system |
Absent |
Absent |
Closed type |
Open type |
|
Reproduction |
Asexual (fragmentation) and Sexual. Hermaphrodite. Internal Fertilization.
Development is indirect. Many larval stages. |
Dioecious. Sexual reproduction. Internal fertilization. Development is direct or indirect. |
Sexual. Earthworms & leeches are monoecious. Neries is dioecious. Development is direct or indirect. |
Mostly dioecious. Usually internal fertilization. Mostly oviparous. Development is direct
or indirect. |
|
Unique features |
Unsegmented, dorso- ventrally flattened body (except tape worms). Excretion and osmo- regulation by Flame cells (protonephridia). Parasites have
Hooks & suckers. Some absorb nutrients from the host through their body
surface. |
Body is circular in cross section. Syncytial epidermis. Thick cuticle. An excretory tube to remove body waste through excretory pore. Sexual dimorphism (females are longer than males). |
Segmentation like rings. Longitudinal
and circular muscles help in
locomotion. Locomotory organs are setae (in earthworm) or parapodia
(in Neries). Excretion by Nephridia. Paired ganglia connected
by lateral nerves to a double
ventral nerve cord. |
Jointed
appendages. Body has 3 regions: head, thorax & abdomen. Body is covered
by chitinous cuticle (exoskeleton). Excretion by Malpighian
tubules. Sensory
organs are antennae, compound &
simple eyes, statocysts
(balance organs). |
|
Examples |
Taenia solium
(Tape worm), Fasciola (Liver fluke), Planaria (shows high regeneration capacity). |
Ascaris (Roundworm), Ancylostoma (Hookworm), Wuchereria (Filarial worm). |
Pheretima (earthworm), Hirudinaria (blood sucking
Leech), Neries (aquatic. Parapodia for swimming). |
Spider, Scorpion, Crab, Prawn, Insects etc. Economically important insects: Apis, Bombyx, Laccifer. Vectors: Mosquitoes (Anopheles, Culex
& Aedes), Housefly etc. Gregarious pest: Locusta. Living fossil: Limulus (King crab) |
1.
Dioecious: Sexes are separate.
2.
Sexual dimorphism: Morphological differences between male and female.
3.
Arthropoda is the largest
phylum. Over two-thirds of all named species are arthropods.
GENERAL CHARACTERS OF DIFFERENT PHYLA (NON-CHORDATES)
|
Features |
Mollusca (Soft-bodied animals) |
Echinodermata (Spiny-skinned animals) |
Hemichordata |
|
Grades of organization |
Organ system |
Organ system |
Organ system |
|
Symmetry |
Bilateral |
Adults radial.
Larvae bilateral. |
Bilateral |
|
Germ layers |
Triploblastic |
Triploblastic |
Triploblastic |
|
Coelom |
Coelomate |
Coelomate |
Coelomate |
|
Habit and habitat |
Aquatic. Few are
terrestrial. |
Exclusively marine. |
Exclusively marine. |
|
Digestive system |
Complete |
Complete. Ventral mouth
and dorsal anus. |
Complete |
|
Respiratory system |
Gills in aq. forms
and pulmonary sac in terrestrial forms. |
Dermal branchiae (skin
gills or papulae) and tube feet. |
Gills |
|
Circulatory system |
Open type |
Open type |
Open type |
|
Reproduction |
Dioecious. Oviparous. Development is direct or indirect. |
Dioecious. External fertilization. Development is indirect. Ciliated free-swimming larva. |
Dioecious. External fertilization. Development is indirect. |
|
Unique features |
Body has head,
visceral mass (visceral hump) & muscular foot. Head has sensory tentacles. Calcareous shell. Feather-like gills for respiration & excretion. Mantle & radula are seen. |
They have an endoskeleton of calcareous ossicles (Spiny bodied). Head absent. Water vascular system present. Excretory system absent. Shows autotomy & regeneration. |
Worm-like cylindrical body formed of anterior proboscis,
a collar and a long trunk. Collar bears stomochord
(a rudimentary structure similar
to notochord). Excretion by Proboscis gland. |
|
Examples |
Pila (Apple Snail), Pinctada
(Pearl Oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil
fish), Aplysia (Sea Hare), Dentalium (Tusk shell), Chaetopleura (Chiton) |
Asterias (Starfish), Echinus (Sea Urchin), Echinocardium, Antedon (Sea Lily), Cucumaria (Sea Cucumber), Ophiura (Brittle Star) |
Balanoglossus (Tongue worm), Saccoglossus |
1. Mollusca is the second largest
phylum.
2. Mantle (Pallium): The membrane which covers visceral mass. Space between
the hump and mantle is called
mantle cavity.
3. Radula: File-like rasping
organ present in the mouth of molluscs. It is used forfeeding.
4.
Water
vascular (ambulacral) system: In this system, sea water
enters through a porous
plate called madreporite and reaches the radiating canals and tube feet (podia). Its functions are locomotion, respiration, capture & transport of food and
excretion.
5.
Hemichordata was earlier
considered as a sub-phylum of Chordata. Like chordates, it has pharyngeal
gill slits.
PHYLUM CHORDATA
It includes animals
with notochord, dorsal
tubular nerve cord and pharyngeal gill slits.
Notochord is a flexible rod located in the mid dorsal line between the alimentary canal and the nerve cord in the embryo.
Differences
between Chordata and Non-Chordata
|
|
|
Chordata |
Non-Chordata |
|
1. Notochord is found in the embryonic stage |
Absent |
|
2. Central
nervous system is dorsal, hollow and
single |
Ventral, solid
and double |
|
3. Pharyngeal gill slits present |
Absent |
|
4. Ventral
heart |
Dorsal heart
(if present) |
|
5. A post-anal part
(tail) is present |
Absent |
Phylum Chordata is classified into 3 subphyla: Urochordata, Cephalochordata & Vertebrata.
|
PROTOCHORDATA (ACRANIATA) |
VERTEBRATA (CRANIATA) |
|
|
Urochordata (Tunicata) |
Cephalochordata |
|
|
|
Lancelet). |
|
- All are ectoparasites on some fishes
- Elongated body without scales and paired fins.
- 6-15 pairs
of gill slits for respiration. Sucking and circular mouth without jaws.
- Cartilaginous cranium and vertebral column
- Circulation is closed type.
- Marine, but migrate for spawning to fresh water. After spawning, they die. Their larvae, after metamorphosis, return
to ocean.
- E.g. Petromyzon (Lamprey) and Myxine (Hagfish)
SUPERCLASS PISCES (FISHES)
|
Class Chondricthyes (Cartilaginous fishes) |
Class Osteichthyes (Bony fishes) |
|
Marine. Stream-lined body. Predaceous. |
Marine &
fresh water. Stream-lined body. |
|
Cartilaginous endoskeleton. Notochord is persistent throughout life. |
Bony endoskeleton. |
|
Ventral mouth. |
Terminal mouth. |
|
Gill slits without operculum. Powerful jaws. |
4 pairs
of gills covered by operculum on each side. |
|
Skin with
placoid scales. Teeth are
modified placoid scales which
are backwardly directed. |
Scales are
Cycloid, ctenoid etc. |
|
No air bladder. So, they have to swim constantly to avoid sinking. |
Air bladder for buoyancy. |
|
Poikilotherms (cold-blooded). |
Poikilotherms (cold-blooded). |
|
Two-chambered heart (one auricle
and one ventricle). |
Two-chambered heart (one auricle
and one ventricle). |
|
Sexes are separate. In males, pelvic
fins bear claspers. Internal fertilization. Many of them viviparous. Examples Scoliodon (Dogfish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray- has poison sting), Torpedo (Electric ray- has electric organ). |
Sexes are separate. External fertilisation. Mostly oviparous. Development is direct. Examples Marine: Exocoetus (flying fish), Hippocampus
(seahorse) Fresh water: Labeo (Rohu), Catla (Katla), Clarias (Magur). Aquarium: Betta (Fighting fish), Pterophyllum (Angel fish). |
SUPERCLASS TETRAPODA
|
Class Amphibia |
Class Reptilia |
Class Aves (Birds) |
Class Mammalia |
|
They live in aquatic & terrestrial habitats and need water
for breeding. |
Dry & cornified skin, epidermal scales or scutes. |
Presence of feathers and beak. Forelimbs are modified into wings. |
Presence of mammary glands (milk producing glands). |
|
Body has head
& trunk. Some have tail. Moist skin without scales. Most have 2
pairs of limbs. |
Snakes and lizards shed their scales as skin
cast. Limbs- 2 pairs
(if present). Crawling mode
of locomotion. |
Dry skin without glands except the oil gland at the base
of tail. Hind limbs have scales and are modified for walking, swimming or clasping tree branches. Hollow & pneumatic long
bones. |
Skin with hair. 2 pairs of limbs for walking,
running, climbing, burrowing, swimming or flying. |
|
Tympanum represents ear. |
Tympanum represents ear. |
Tympanum represents ear. |
External ear (Pinnae). |
|
3-chambered heart (2 auricles + 1 ventricle). |
3-chambered heart (but
a septum partially separates ventricle). Heart is 4- chambered in crocodiles. |
4-chambered heart. |
4-chambered heart. |
|
Poikilotherms |
Poikilotherms |
Homoiotherms |
Homoiotherms |
|
Alimentary canal,
urinary & reproductive tracts open into
a Cloaca which opens to exterior. |
Well-developed alimentary canal. |
Digestive tract has additional chambers, the crop & gizzard. |
Well-developed alimentary canal. Dentition is Heterodont, thecodont &
diphyodont. |
|
Respiration is by gills (in larva), lungs & skin |
Respiration by lungs. |
Double respiration. Air sacs connected to lungs. |
Respiration by lungs. |
|
Sexes are separate. External fertilisation.
Oviparous. Development is indirect. |
Internal fertilisation. Oviparous. Development is direct. |
Internal fertilisation. Oviparous. Development is direct. |
Sexes are separate. Internal
fertilisation. Viviparous (except Echidna and Platypus). Development is direct. |
|
Examples Bufo (Toad), Rana (Frog),
Hyla
(Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia) |
Examples Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus
(Crocodile), Alligator, Hemidactylus (Wall lizard). Poisonous snakes: Naja (Cobra), Bangarus (Krait), Vipera (Viper) etc. Non-poisonous snakes: Python etc. |
Examples Corvus (Crow), Columba (Pigeon),
Psittacula (Parrot), Struthio
(Ostrich), Pavo (Peacock),
Aptenodytes (Penguin), Neophron
(Vulture) etc. |
Examples Ornithorhynchus (Platypus), Macropus (Kangaroo),
Pteropus (flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (dog),
Felis (Cat), Elephas (Elephant), Equus (Horse),
Delphinus (Commondolphin), Balaenoptera
(blue whale), Panthera tigris (Tiger), Panthera leo (lion) |
Poikilotherms
(Cold-blooded animals): Animals that lack the capacity to regulate their body temperature.
Homoiotherms (warm-blooded animals): Animals having
ability to maintain
a constant body temperature.
Comments
Post a Comment