Revision: Kingdom Classification >> Kingdoms in Animals Biology ICSE ICSE Class 7 CISCE

Classes comprising animals like fish, amphibians, reptiles, birds, and mammals constitute the next higher category called phylum. All these, based on common features like the presence of the notochord and dorsal hollow neural system, are included in the phylum Chordata. In the case of plants, classes with a few similar characters are assigned to a higher category called division.

Genus comprises a group of related species that have more characters in common in comparison to species of other genera. We can say that genera are aggregates of closely related species. For example, potato and brinjal are two different species, but both belong to the genus Solanum. Lions (Panthera leo), leopards (P. pardus), and tigers (P. tigris), with several common features, are all species of the genus Panthera. This genus differs from another genus, Felis, which includes cats.

A taxon is a taxonomic group at any level. It represents a group of organisms at any level.

1. The next category, family, has a group of related genera with a smaller number of similarities as compared to genus and species. Families are characterised on the basis of both vegetative and reproductive features of plant species.
2. Among plants, for example, three different genera, Solanum, Petunia, and Datura, are placed in the family Solanaceae. For example, the genus Panthera, comprising lions, tigers, and leopards, is put along with the genus  Felis (cats) in the family Felidae. Similarly, if you observe the features of a cat and a dog, you will find some similarities and some differences as well.
3. They are separated into two different families – Felidae and Canidae, respectively.

1. You have seen earlier that categories like species, genus, and families are based on a number of similar characters.
2. Generally, order and other higher taxonomic categories are identified based on the aggregates of characters. Order, being a higher category, is the assemblage of families that exhibit a few similar characters.
3. The similar characters are fewer in number as compared to the different genera included in a family. Plant families like Convolvulaceae, Solanaceae are included in the order Polymoniales, mainly based on their floral characters.
4. The animal order, Carnivora, includes families like Felidae and Canidae.

This category includes related orders. For example, order Primata, comprising monkeys, gorillas, and gibbons, is placed in class Mammalia, along with order Carnivora, which includes animals like tigers, cats, and dogs. Class Mammalia has other orders as well.

A large opening through which water exits the body of a sponge is called an osculum.

Small pores through which water enters the body of a sponge are called ostia.

Special types of cells present in sponges that help in generating water current and food collection are called collar cells.

An umbrella-shaped body form in coelenterates, such as Aurelia (jellyfish), is called a Medusa.

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.

A cylindrical body form in coelenterates, such as Hydra, which is usually attached to a surface, is called a Polyp.

• Meaning - Heterotrophic, multicellular eukaryotes; cells lack a cell wall; cannot produce their own food.
• Nutrition - Mode of nutrition is holozoic (food obtained by ingestion); food is digested in an internal cavity; food is stored as glycogen or fat.
• Reproduction - By sexual reproduction - copulation of male and female followed by embryological development.
• Other features - Follow a definite growth pattern; higher forms have elaborate sensory and neuromotor mechanisms (nervous system and sensory organs); most are capable of locomotion.
• Cell structure - Has a nucleus and membrane-bound organelles; no chloroplasts (hence cannot photosynthesise); no cell wall (unlike plants and fungi).

• Meaning - Sponges; primarily marine (except Spongilla - freshwater); body is asymmetrical; cellular level of organisation.
• Water canal system - Water enters through ostia (pores) → spongocoel (body cavity) → exits through osculum; helps in feeding, respiration and waste removal; canals lined by choanocytes (collar cells).
• Digestion - Intracellular; body supported by spicules and spongin fibres.
• Reproduction - Hermaphrodite (produces both eggs and sperm); asexual by fragmentation; sexual by gamete formation; fertilisation is internal with indirect development (distinct larval stage).
• Examples - Sycon, Spongilla (freshwater), Euspongia (bath sponge), Euplectella (Venus' Flower Basket).

• 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

• 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

• 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

• 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

• 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

• 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

• 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)