Definitions [7]
Definition: Notochord
A long rod-like supporting structure present on the dorsal side of the animal body that keeps the nerve tissue isolated from the remaining body is called Notochord.
Definition: Ostia
Small pores through which water enters the body of a sponge are called ostia.
Definition: Osculum
A large opening through which water exits the body of a sponge is called an osculum.
Definition: Collar Cells
Special types of cells present in sponges that help in generating water current and food collection are called collar cells.
Definition: Polyp
A cylindrical body form in coelenterates, such as Hydra, which is usually attached to a surface, is called a Polyp.
Definition: Medusa
An umbrella-shaped body form in coelenterates, such as Aurelia (jellyfish), is called a Medusa.
Define the terms and give one example
Coelom
Coelom: Coelom is the internal body cavity between visceral organs and body wall in which well-developed organs can be accommodated. In some animals pseudocoelom is present (e.g. nematodes) which is a body cavity not lined by mesoderm. True coelom is lined by mesoderm and first appears in annelids. Examples of animals in which true coelom is present are Earthworm, cockroach, snail, all chordates such as birds, humans, etc.
Key Points
Key Points: History of Animal Classification
- Aristotle was the first to classify animals based on body size, habits, and habitats.
- His method was known as the artificial method and was followed by other scientists like Theophrastus and Linnaeus.
- The natural system of classification was later developed using body structure, cells, chromosomes, and biochemical properties.
- Evolution-based classification was also introduced by scientists like Dobzhansky and Carl Woese.
Key Points: Traditional Method of Animal Classification
Animals are divided into two groups based on the presence or absence of a notochord – chordates and non-chordates.
| No. | Feature | Chordates | Non-Chordates |
|---|---|---|---|
| 1 | Notochord | Present | Absent |
| 2 | Nerve Cord | Dorsal, hollow | Ventral, solid, and paired (if present) |
| 3 | Respiratory Organs | Gill slits or lungs | Gill slits absent |
| 4 | Position of Heart | Ventral side | Dorsal side (if present) |
Key Points: Grades of Organization
| No. | Grade of Organization | Description | Examples |
|---|---|---|---|
| 1 | Protoplasmic Grade | All functions performed by a single cell | Amoeba, Paramecium |
| 2 | Cellular Grade | Body made of cells, but tissues not formed | Phylum Porifera (e.g. Sycon) |
| 3 | Cell-Tissue Grade | Cells form tissues to perform functions | Phylum Cnidaria |
| 4 | Tissue-Organ Grade | Tissues form organs, but organ systems not fully developed | Flatworms |
| 5 | Organ-System Grade | Organs work together to form systems with specific functions | Crab, Frog, Human |
Key Points: Body Symmetry
| No. | Type of Symmetry | Description | Examples |
|---|---|---|---|
| 1 | Asymmetrical Body | No imaginary axis can divide the body into two equal halves | Some sponges |
| 2 | Radial Symmetry | Body can be divided into equal halves through multiple planes from central axis | Starfish |
| 3 | Bilateral Symmetry | Only one imaginary axis divides body into two equal halves | Insects, fishes, frogs, birds, humans |
Key Points: Germ Layers
| No. | Type | Germ Layers Present | Examples |
|---|---|---|---|
| 1 | Diploblastic | Endoderm and Ectoderm only | Cnidarians |
| 2 | Triploblastic | Endoderm, Mesoderm, and Ectoderm | Most other animals |
Key Points: Body cavity (Coelom)
| No. | Type of Coelom | Body Cavity Formation | Examples |
|---|---|---|---|
| 1 | Eucoelomates | True coelom from mesoderm | Annelida and higher phyla |
| 2 | Acoelomates | No body cavity | Porifera, Cnidaria, Platyhelminthes |
| 3 | Pseudocoelomates | Cavity not fully from mesoderm | Aschelminthes |
Key Points: Porifera
- Habitat: Aquatic animals, mostly marine and few freshwater species
- Body Symmetry: Mostly asymmetrical
- Special Features: Presence of pores (ostia and oscula), collar cells, and sedentary (non-motile) nature
- Body Support: Supported by spicules or spongin fibres made of calcium carbonate or silica
- Reproduction: Asexual (by budding) and sexual methods; good regeneration ability
- Examples: Sycon, Euspongia (Bath sponge), Hyalonema, Euplectella
Key Points: Cnidaria/Coelenterata
- Body Shape: Cylindrical (Polyp) or umbrella-like (Medusa)
- Habitat: Mostly marine; few are freshwater dwellers
- Body Structure: Radially symmetrical and diploblastic
- Special Feature: Tentacles with cnidoblasts used for capturing prey and injecting toxins
- Examples: Hydra, Adamsia (Sea anemone), Physalia (Portuguese man-of-war), Aurelia (Jellyfish), Corals
Key Points: Platyhelminthes
- Body Shape: Slender, flat like a leaf or strip (called flatworms)
- Habitat: Mostly endoparasitic; few are free-living and aquatic
- Body Structure: Acoelomate, bilaterally symmetrical, and triploblastic
- Reproduction: Hermaphrodite – both male and female systems in one body
- Examples: Planaria, Liver fluke, Tapeworm
Key Points: Aschelminthes
- Body Shape: Long, thread-like or cylindrical (called roundworms)
- Habitat: Free-living (aquatic or terrestrial) or endoparasitic
- Body Structure: Triploblastic, pseudocoelomate, non-segmented, with a tough cuticle
- Reproduction: Unisexual – male and female are separate
- Examples: Ascaris (intestinal worm), Filarial worm, Loa loa (eye worm)
Key Points: Annelida
- Body Structure: Long, cylindrical, metamerically segmented
- Habitat: Mostly free-living (marine, freshwater, or terrestrial); some are ectoparasites
- Body Type: Triploblastic, bilaterally symmetrical, and eucoelomate
- Locomotion: Movement with setae, parapodia, or suckers
- Reproduction: Hermaphrodite or unisexual
- Examples: Earthworm, Leech, Nereis
Key Points: Arthropoda
- Body Structure: Segmented, triploblastic, eucoelomate, and bilaterally symmetrical
- Appendages: Jointed appendages with a chitinous exoskeleton
- Habitat: Found in all types of environments – aquatic, terrestrial, and aerial
- Reproduction: Unisexual
- Examples: Crab, spider, cockroach, butterfly, honey bee
Key Points: Mollusca
- Body Structure: Soft, non-segmented, triploblastic, eucoelomate body
- Symmetry: Bilateral (except in some, like snail)
- Body Division: Head, foot, and visceral mass covered by a mantle
- Shell: Hard, calcareous shell (may be external, internal, or absent)
- Reproduction: Unisexual
- Examples: Bivalve, Snail, Octopus
Key Points: Echinodermata
- Body Structure: Triploblastic, eucoelomate, radially symmetrical in adults and bilaterally symmetrical in larvae
- Habitat: Exclusively marine
- Locomotion: Tube feet are used for movement and capturing prey; some are sedentary
- Skeleton: Made of calcareous spines and ossicles
- Reproduction: Mostly unisexual
- Examples: Starfish, sea urchin, sea cucumber, brittle star
Key Points: Hemichordata
- Body Structure: Divided into proboscis, collar, and trunk.
- Notochord: Present only in the proboscis region, hence the name hemichordates.
- Habitat: Marine animals that live in burrows in sand.
- Respiration: Possess one to many pharyngeal gill slits.
- Reproduction: Mostly unisexual, though some may be hermaphrodite.
- Examples: Balanoglossus, Saccoglossus.
- Evolutionary Importance: Balanoglossus is considered a connecting link between non-chordates and chordates.
Key Points: Urochordata
- Habitat: Marine
- Body Covering: Covered with a skin-like test or tunic
- Notochord: Present only in the tail region of larva
- Development: Larvae are free-swimming and undergo metamorphosis to become sessile adults
- Reproduction: Generally hermaphrodite
- Examples: Herdmania, Doliolum, Oikopleura
Key Points: Cephalochordata
- Body Type: Small, fish-like, marine animals
- Notochord: Present throughout the body length
- Pharynx: Very large, with gill-slits
- Reproduction: Unisexual
- Example: Amphioxus
Key Points: Vertebrata/Craniata
- Notochord: Replaced by vertebral column
- Head: Well developed
- Brain Protection: Enclosed in a cranium
- Endoskeleton: Cartilaginous or bony
- Jaw Type: Some are jawless (Agnatha), others have jaws (Gnathostomata)
Key Points: Cyclostomata
- Mouth: Jawless, with sucker
- Skin: Soft, without scales
- Appendages: Paired appendages absent
- Endoskeleton: Cartilaginous
- Lifestyle: Mostly ectoparasitic
- Examples: Petromyzon, Myxine
Key Points: Pisces
- Temperature Regulation: Cold-blooded (Poikilotherms)
- Habitat: Aquatic (marine and freshwater)
- Body Shape: Spindle-shaped
- Locomotion: Fins used for swimming; tail fin for steering
- Skeleton: Scales as exoskeleton; cartilaginous or bony endoskeleton
- Respiration: Through gills
- Examples: Rohu, Shark, Sea horse, Pomfret
Key Points: Amphibia
- Life Stages: Aquatic larva (with aquatic respiration); adult lives on land and water
- Appendages: Two pairs, digits without claws
- Skin: Moist, without scales
- Respiration: Both aquatic and aerial in adults
- Sensory Organs: Tympanum present, external ear absent, eyelids present
- Examples: Frog, Toad, Salamander
Key Points: Reptilia
- Movement: Creeping (body cannot be fully lifted)
- Temperature Regulation: Cold-blooded (Poikilotherms)
- Skin: Dry and scaly
- Neck: Present
- Digits: With claws
- External Ear: Absent
- Examples: Tortoise, Lizard, Snake
Key Points: Aves
- Temperature Regulation: Warm-blooded (Homeotherms)
- Body Structure: Spindle-shaped to reduce air resistance
- Forelimbs: Modified into wings
- Exoskeleton: Feathers; digits with scales and claws
- Jaws: Modified into beak
- Neck: Present
- Examples: Peacock, Parrot, Duck, Penguin
Key Points: Mammalia
- Unique Feature: Mammary glands present
- Temperature Regulation: Warm-blooded
- Body Division: Head, neck, trunk, tail
- Digits: Provided with nails, claws, or hooves
- Exoskeleton: Hair or fur
- Examples: Elephant, Human, Kangaroo, Dolphin
Important Questions [10]
- Write the correct co-relation: Annelida: Earthworm :: Platyhelminthes: _______
- Animal with bilateral symmetry in ______.
- Label the body organization of human in the following figure:
- Identify my class/phylum and give one example of it: I live in your small intestine, my body is long and thread like and pseudocoelomate.
- Identify my class/phylum and give one example of it: We form the highest number of animals on the planet. We have bilateral symmetry and our exoskeleton is in the form of chitin.
- Give a scientific reason. Cockroach belongs to phylum Arthropoda.
- Observe the following diagram. Write the answers of the following questions. To which phylum does the animal included in the diagram belong? What is the exoskeleton made up? What is the symmetry?
- Example of phylum Arthropoda is ______.
- Cockroach, Frog, Sparrow, Starfish, from these animals which can regenerate its broken body part?
- Read the statements and answer accordingly: Calcareous spines are present on the body. Tube feet are used for locomotion and capturing prey also. - Identify the phylum and give one example.
Concepts [28]
- Classification of Living Organisms
- History of Animal Classification
- Traditional Method of Animal Classification
- Conventional System of Animal Classification
- Criteria for New System of Classification > Grades of Organization
- Criteria for New System of Classification > Body Symmetry
- Criteria for New System of Classification > Germ Layers
- Criteria for New System of Classification > Body cavity (Coelom)
- Criteria for New System of Classification > Body Segmentation
- Phylum: Porifera
- Phylum: Cnidaria/Coelenterata
- Phylum: Platyhelminthes
- Phylum: Aschelminthes
- Phylum: Annelida
- Phylum: Arthropoda
- Phylum: Mollusca
- Phylum: Echinodermata
- Phylum: Hemichordata
- Phylum: Chordata
- Subphylum: Urochordata
- Subphylum: Cephalochordata
- Subphylum: Vertebrata/Craniata
- Subphylum: Vertebrata/Craniata > Class: Cyclostomata
- Subphylum: Vertebrata/Craniata > Class: Pisces
- Subphylum: Vertebrata/Craniata > Class: Amphibia
- Subphylum: Vertebrata/Craniata > Class: Reptilia
- Subphylum: Vertebrata/Craniata > Class: Aves
- Subphylum: Vertebrata/Craniata > Class: Mammalia
