Animal Classification Class 10 Science Notes Maharashtra State Board
History of Animal Classification
From time to time, different scientists have tried to classify the animals. Greek philosopher Aristotle was the first to perform the animal classification. Aristotle classified the animals according to criteria like body size, habits, and habitats. Further, as per the new developments in sciences, references were changed, and thereby the criteria of animal classification too. The classification proposed by Aristotle is known as the ‘Artificial method’. Besides Aristotle, the artificial method of classification was followed by Theophrastus, Pliny, John Ray, Linnaeus, etc.
Later on, the ‘Natural system of classification’ was followed. The Natural system of classification was based on various criteria like body organization, types of cells, chromosomes, biochemical properties, etc. By that time, a system of classification based on evolution was also brought into practice. It was used by Dobzhansky and Meyer. Recently, Carl Woese has also proposed animal classification.
Benefits of Animal Classification
- The study of animals becomes convenient.
- The study of few animals from a group helps to understand that entire animal group.
- It gives an idea about animal evolution.
- Animals can be easily identified with great accuracy.
- It helps to understand the relationship of animals with other living organisms.
- It helps to understand the habitat of each animal and its exact role in nature.
- It helps to understand various adaptations shown by animals.
Traditional Method of Animal Classification
Traditionally, depending upon the presence or absence of the notochord, the animal kingdom has been divided into two groups – Non-chordates and Chordates.
A. Non-Chordates:
Characters of non-chordate animals are as follows:
- The body is not supported by a rod-like notochord.
- Pharyngeal gill slits are absent.
- Nerve cord; if present, it is on the ventral side. It is solid & paired.
- The heart, if present, is on the dorsal side.
Non-chordates are classified/divided into ten phyla. Those phyla are Protozoa, Porifera, Coelentarata/Cnidaria, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata and Hemichordata.
Chordates:
Characters of chordates are as follows:
- The body is supported by a notochord.
- Pharyngeal gill slits or lungs are present for respiration.
- The nerve cord is present on the dorsal side of the body. It is hollow.
- The heart is present on the ventral side of the body.
Notochord is a long rod-like supporting structure present on the dorsal side of an animal body. It keeps the nerve tissue isolated from the remaining body.
All chordate animals are grouped in a single phylum and the name of the phylum is the same i.e. Phylum- Chordata. This phylum has been divided into three subphyla Urochordata, Cephalochordata & Vertebrata. Subphylum Vertebrata has been further divided into six classes as Class: Cyclostomata, Class: Pisces, Class: Amphibia, Class: Reptilia, Class: Aves, and Class: Mammalia. This system of animal classification has been in practice till now. However, nowadays, a new system of classification is followed. We will study this new system of animal classification in brief.
At present, according to the five kingdom classification system of Robert Whittaker, all multicellular animals are included in Kingdom: Animalia. This system of classification is based upon some criteria like Body organization, Body symmetry, Body cavity, Germinal layers, Segmentation, etc.
Criteria for New System of Classification
A. Grades of Organization
The body of animals is made up of cells. In the case of multicellular animals, many cells are performing different functions in their body while in unicellular animals, as their body is made up of a single cells; all functions are performed by the same cell only. The body organization of unicellular animals is referred to as the ‘Protoplasmic grade’ organization.
In the case of multicellular animals, if tissues are not formed, their body organization is called a ‘Cellular grade organization’. Ex. Phylum-Porifera.
In the case of some animals, cells come together to form tissues with the help of which all the body functions are performed. Such animals show ‘Cell – tissue grade’ organization. Ex. Animals from phylum – Cnidaria. Flatworms show ‘Tissue-Organ grade’ organization. In this type of organization, tissues are organized to form some organs. However, complete organ systems are not formed.
Besides the four types of body organizations mentioned above, the Remaining animals show ‘Organ-system grade organization’ in which different organs are joined together to form an organ system that performs specific functions.
Ex. Crab, Frog, Human, etc.
B. Body Symmetry
Take the pictures of human body and the Amoeba and try to take an imaginary section through a specific plane of their bodies to get two halves. What did you observe?
Asymmetrical Body: In the case of such a body, there is no such imaginary axis of the body through which we can get two halves.
Ex. Amoeba, Paramoecium, some sponges.
Radial Symmetry: In this type of body, if an imaginary cut passes through the central axis but any plane of the body, it gives two halves.
Ex. Starfish. In the case of this animal, five different planes pass through the central axis of the body through which we can get two halves.
Bilateral Symmetry: In this type of body, there is only one such imaginary axis of the body through which we can get two halves.
Ex. Insects, fishes, frogs, birds, humans, etc.
C. Germ Layers: Diploblastic and Triploblastic
In the case of multicellular animals, germ layers are formed during the initial period of their embryonic development and from those germ layers only, different tissues are formed in the body. In the case of some animals, only two germ layers [Endoderm & ectoderm] are formed.
Ex: All Cnidarians. In most of the remaining animals, three germ layers are formed i.e. mesoderm besides endoderm & ectoderm.
D. Body Cavity (Coelom)
The cavity between the body and internal organs is called as body cavity/coelom. In the case of multicellular animals, during the initial period of their embryonic development, the body cavity is formed from either mesoderm or gut. Such a type of body cavity is present in animals of phylum Annelida and all phyla coming after Annelida. Such animals are called eucoelomate (animals with true body cavity). The body cavity is absent in the case of animals from phyla Porifera, Cnidaria, and Platyhelminthes. Such animals are called acoelomate. In the case of animals from the phylum Aschelminthes, they have body cavities but it is not formed by the above-mentioned two ways. Hence those animals are called pseudocoelomates.
E. Body Segmentation
If the body of the animal is divided into small, similar units, then such a body is called a segmented body and each small unit is called a segment.
Ex: Animals like earthworms from phylum Annelida.
Phylum – Porifera
1. These animals have with simplest body plan and are called ‘Sponges’. They bear numerous pores on their body. Those pores are called ‘Ostia’ and ‘Oscula’.
2. These are aquatic animals. Most of them are marine and few are freshwater dwellers.
3. Most of the animals have an asymmetrical body.
4. These animals have special types of cells- collar cells.
5. These animals are always attached to the substratum and, hence do not show locomotion. Hence, they are referred as sedentary animals.
6. Their spongy body is supported by spicules or spongin fibers. Spicules are made up of calcium carbonate or silica.
7. These animals feed upon small organisms taken in their body along with water. Water is taken in through the ostia and given out through the oscula.
8. These animals reproduce by budding, an asexual method, and/or by sexual methods. Besides, they have a good ability for regeneration.
Examples: Sycon, Euspongia (Bath sponge), Hyalonema, Euplectella, etc.
Phylum – Coelenterata/Cnidaria
1. The body of these animals is cylindrical or umbrella-like. If it is cylindrical, it is called a ‘Polyp’, and if it is an umbrella like called a ‘Medusa’.
2. Most of these animals are marine. Only a few are fresh-water dwellers.
3. The body of these animals is radially symmetrical & diploblastic.
4. Cnidoblast-bearing tentacles are present around the mouth. Tentacles are useful for capturing the prey whereas cnidoblasts inject the toxin into the body of prey. Those are useful for protection too.
Examples: Hydra, Adamsia (Sea anemone), Physalia (Portuguese-man-of-war), Aurelia (Jellyfish), Corals, etc.
Bath Sponge:
This is black coloured and somewhat round-shaped animal. Its body is mainly made up of fibers of a protein spongin and due to this, they have good water-holding capacity. It was used for bathing during the old days. Besides, it was also used for manufacturing pillows and cushions. These were also used as wetting material for sticking postal stamps and counting the currency notes.
Phylum-Platyhelminthes
1. The body of these animals is slender & flat like a leaf or strip. Hence, they are called ‘flatworms’.
2. Most of these animals are endoparasites. Few are free-living & aquatic.
3. Body is acoelomate & bilaterally symmetrical.
4. These are triploblastic i.e. their body is made up of three germ layers – endoderm, ectoderm & mesoderm.
5. These animals are hermaphrodite i.e. male and female reproductive systems are present in the same animal body.
Examples: Planaria, Liver fluke, Tapeworm, etc.
Coral reefs are present in the ocean. These reefs are colonies of specific cnidarians. A precious stone called ‘Coral’ (पोवळा) and the coral powder (प्रळ भस्म used in ayurveda is derived from these reefs. Collect more information about these corals from the internet.
Phylum-Aschelminthes
1. The body of these animals is long thread-like or cylindrical. Hence, they are called roundworms.
2. These animals are either free-living or endoparasites. Free-living animals are either aquatic or terrestrial.
3. The body of these animals is triploblastic and pseudocoelomate.
4. The body of these animals is non-segmented and covered with tough cuticles.
5. These animals are unisexual.
Examples: Ascaris (Intestinal worm), Filarial worm, Loa loa (Eye worm), etc.
Phylum – Annelida
1. The body of these animals is long, cylindrical & metamerically segmented.
2. Most of the animals are free-living, but few are ectoparasites. Free-living animals may be marine or freshwater dwellers or terrestrial.
3. These animals are triploblastic, bilaterally symmetrical and coelomate.
4. They have setae or parapodia or suckers for locomotion.
5. Their body is covered with special cuticles.
6. These animals are either hermaphrodite or unisexual.
Examples: Earthworm, Leech, Nereis, etc.
Phylum- Arthropoda
1. These animals have jointed appendages. Hence they are called arthropods.
2. Planet Earth has the highest number of animals from this phylum. Hence, this is the largest phylum with highly successful animals in the animal kingdom.
3. These animals are found in all types of habitats ranging from the deepest oceans to the highest mountains.
4. The body of these animals is triploblastic, coelomate, bilaterally symmetrical, and segmented.
5. Chitinous exoskeleton is present around their body.
6. These animals are unisexual.
Examples: Crab, spider, scorpion, millipede, centipede, cockroach, butterfly, honey bee, etc
Phylum – Mollusca
1. The body of these animals is soft and slimy. Hence they are referred to as molluscs.
2. This is the second-largest phylum in the animal kingdom.
3. These animals are aquatic or terrestrial. Most of the aquatic mollusks are marine, but few are freshwater dwellers too.
4. The body of these animals is triploblastic, coelomate, non-segmented, and soft. Except for animals like snails, their body shows bilateral symmetry. Their body is divided into three divisions head, foot, and visceral mass.
5. Visceral mass is covered with mantle. This mantle secretes a hard, calcareous shell. This shell may be external or internal or even absent in some cases.
6. These animals are unisexual.
Examples: Bivalve, Snail, Octopus, etc.
Phylum – Echinodermata
1. Calcareous spines are present on the body of these animals; hence they are called echinoderms.
2. These animals are found only in the ocean.
3. Their body is triploblastic, eucoelomate. And it is radially symmetrical in the adult stage. However, they show bilateral symmetry in the larval stage.
4. They perform locomotion with the help of tube feet. Tube feet are also useful for capturing the prey. Some animals are sedentary.
5. They have a skeleton made up of calcareous spines and/or ossicles (plates).
6. These animals have a good ability of regeneration.
7. These animals are mostly unisexual.
Examples: Starfish, sea-urchin, brittle star, sea cucumber, etc.
Phylum – Hemichordata
1. The body of these animals is divided into three parts proboscis, collar & trunk.
2. Notochord is present in the proboscis region only. Hence, they are called hemichordates.
3. These animals are also called ‘acorn worms’.
4. These are marine animals, that live in burrows in sand.
5. They have one to many pharyngeal gill slits.
6. They are unisexual or some may be hermaphrodite.
Ex: Balanoglossus, Saccoglossus.
Through the viewpoint of evolution, Balanoglossus is considered a connecting link between non-chordates and chordates. This animal shows the characters of both groups.
Phylum – Chordata
These animals have supporting notochord in their body. All chordates are included in the same phylum. The phylum Chordata is classified into three subphyla. Following are important characters of phylum Chordata.
1. Notochord is present in the body during at least any developmental stage.
2. Pharyngeal gill slits are present in the body during at least any developmental stage.
3. A single, tubular spinal cord is present on the dorsal side of the body.
4. The heart is present on the ventral side of the body.
A. Sub Phylum – Urochordata
1. These are marine animals.
2. Their body is covered by a skin-like test or tunic.
3. Larvae of these animals are freely swimming and notochord is present in only tail region of larvae. Hence, they are called Urochordata.
4. Larvae metamorphose into adults after settling down at the bottom of the sea.
5. Generally, these animals are hermaphrodite.
Examples: Herdmania, Doliolum, Oikopleura, etc.
B. Sub Phylum – Cephalochordata
1. These are small, fish-like, marine animals.
2. Notochord is present throughout the body length.
3. Pharynx is very large and contains gill slits.
4. These animals are unisexual.
Ex: Amphioxus.
C. Sub Phylum – Vertebrata/Craniata
1. In these animals, the notochord is replaced by a vertebral column.
2. In these animals, the head is well developed.
3. The brain is protected by the cranium.
4. The endoskeleton is either cartilaginous or bony.
5. Some chordates are jaw-less (Agnatha) whereas some are with jaws (Gnathostomata).
Subphylum – Vertebrata is divided into six classes as follows:
a. Class – Cyclostomata
1. These animals have jaw-less mouths provided with suckers.
2. Their skin is soft and without any scale.
3. Paired appendages are absent.
4. The endoskeleton is cartilaginous.
5. Most of the animals are ectoparasites.
Examples: Petromyzon, Myxine, etc.
b. Class – Pisces
1. These are cold-blooded (Poikilotherms) aquatic animals living in marine and fresh waters.
2. The body is spindle-shaped to minimize water resistance.
3. They have paired & unpaired fins for swimming. The tail fin is useful as a steering organ during swimming.
4. The exoskeleton is in the form of scales & endoskeleton is either cartilaginous or bony.
5. Respiration occurs with gills.
Examples: Rohu, Pomfret, Sea horse, Shark, Electric ray, Sting ray, etc.
c. Class – Amphibia
1. These animals are strictly aquatic during larval life and perform only aquatic respiration whereas they can live in water as well as on land during adult life and can perform aquatic as well as aerial respiration.
2. They have two pairs of appendages. Digits are without claws.
3. Exoskeleton is absent. Skin is without any derivative and is usually kept moist for respiration.
4. External ear is absent but tympanum is present.
5. Neck is absent. Eyes are prominent with eyelids.
Ex: Frog, Toad, Salamander, etc.
d. Class – Reptilia
1. According to the course of animal evolution, these are the first true terrestrial animals with creeping movement.
2. These are cold-blooded (poikilotherms) animals.
3. They creep on the land as their body cannot be lifted.
4. Their skin is dry and scaly.
5. Neck is present between head & trunk.
6. External ear is absent.
7. Digits are provided with claws.
Examples: Tortoise, Lizard, Snake, etc.
e. Class – Aves
1. These vertebrates are completely adapted for aerial life.
2. These are warm-blooded (Homeotherms) i.e. they can maintain their body temperature constant.
3. Their body is spindle-shaped to minimize air resistance during flight.
4. Forelimbs are modified into wings. Digits are covered with scales and bear claws.
5. Exoskeleton is present in the form of feathers.
6. Neck is present between head and trunk.
7. Jaws are modified into beaks.
Examples: Peacock, Parrot, Pigeon, Duck, Penguin, etc
f. Class – Mammalia
1. The presence of mammary glands is a typical character of mammalia.
2. These animals are warm-blooded.
3. The body is divided into the head, neck, trunk, and tail.
4. Digits are provided with nails, claws, or hooves.
5. The exoskeleton is in the form of hair or fur.
Examples: Elephant, Human, Kangaroo, Dolphin, Bat, etc.
Comprehensive Maharashtra State Board Class 10 Science Notes Animal Classification can help students make connections between concepts.