Secondary 2018 Class 8 Science 8 PDF

# Chapter One: Classification of Animal Kingdom The world is inhabited by numerous diverse groups of small and large animals. There are various similarities and dissimilarities among them. Starting from microscopic Amoeba to the gigantic whale, all are included in this diverse animal kingdom. Diffe...

# Chapter One: Classification of Animal Kingdom The world is inhabited by numerous diverse groups of small and large animals. There are various similarities and dissimilarities among them. Starting from microscopic Amoeba to the gigantic whale, all are included in this diverse animal kingdom. Differences among animals depend on their environmental diversity. Animal diversity depends on the variety of habitats in which they live. It is very difficult to understand the vast animal world. To gather knowledge of the animal kingdom easily, its systematic arrangement is necessary, and the method is known as classification. Classification makes the way easy to gather knowledge about the animal kingdom. At the end of the chapter, we will be able to: - classify invertebrate animals. - classify vertebrate animals. - explain the necessity of classification of the living world. ## Lesson 1: Classification of animal kingdom You see various types of small and big animals around you. Based on the knowledge you have acquired in class six, try to answer the questions below. Do all the animals look alike? Do all have vertebral column? Do they share same environment (habitat)? Do they take same food? Do they have similar types of locomotion? Now match your thoughts to the answers below. The animals which we see around us are not all alike. Their shape, structure as well as other physiological activities are also different. Some have vertebral column and some do not have. They live on land, in water and on the trees. Their food is also of different kinds. Animals usually move their whole bodies and often have special organs which do this, such as fins, wings, legs, cilia, appendages etc. Again, some sessile forms are also present in them. We do not have sufficient knowledge about the exact number of such diverse animals in the world. So far about 1.5 million species of animals have been discovered and the number is increasing day by day. Classification is an easy way to know the structure and nature of such huge number of animals. Morphological characteristics of the animal, similarity and dissimilarity among them and their interrelationship are the basis of classification. Depending on their characteristics they are grouped into different taxon serially. This step-wise grouping of the living world is known as classification. To meet this requirement, taxonomy has come up as a separate branch of biology. Species is the lowest rank of the taxonomic unit. For example; man, pigeon, toad etc. are separate species. To classify, an animal is arranged step by step depending on its characters. Aristotle, John Ray and Carolus Linnaeus are the notable names in the history of classification. Naturalist Carolus Linnaeus is called the father of taxonomy. In the naming of animals he introduced binomial nomenclature and defined genus and species. Scientific name of an animals, contains two parts. The process of such naming is called binomial or scientific name. For example, Homo sapiens is the scientific name of man. Scientific name must be in Latin or Latinized language (English). | Name of Animal | Habitat | Structure | Usefulness | Harmfulness | |---|---|---|---|---| | Monkey | | | | | | Earthworm | | | | | | Mussel | | | | | | Bird | | | | | | Fish | | | | | ## Lesson 2-5: Classification of invertebrate animals In the modem classification, all animals belong to the Kingdom Animalia. In this classification previously known phylum Protozoa is ranked as a sub kingdom. Animals of animalia kingdom have been divided in nine phyla. Among these, the first eight phyla belong to invertebrate animals and the last one belongs to vertebrate animals. ## Classification of Kingdom Animalia at a glance: - **Kingdom:** Animalia - **Phylum:** Porifera - **Class:** Cyclostomata - **Phylum:** Cnidaria - **Class:** Chondrichthyes - **Phylum:** Platyhelminthes - **Class:** Osteichthyes - **Phylum:** Nematoda - **Class:** Amphibia - **Phylum:** Annelida - **Class:** Reptilia - **Phylum:** Arthropoda - **Class:** Aves - **Phylum:** Mollusca - **Class:** Mammalia - **Phylum:** Echinodermata - **Sub Phylum:** Urochordata - **Phylum:** Chordata - **Sub Phylum:** Cephalochordata - **Sub Phylum:** Vertebrata ## 1. Phylum-Porifera ### Habit and habitat: The member of the phylum porifera is commonly known as 'Sponge'. Their distribution is worldwide i.e. they are found all over the world. Most of the species are marine. But some live in fresh water. Usually, they live in colonies. ### General characteristics: - Simplest multicellular animal. - Body wall with numerous pores. Through these pores food and oxygen enter into the body. - No compact tissue, organ and organ system. **Example:** *Spongilla, Scypha.* ## 2. Phylum-Cnidaria (Previously known as Phylum Coelenterata) ### Habit and habitat: Members of this phylum are present in almost all the regions of the world. They are mostly marine. Many species found in canals, beels, rivers, lakes, fountains, etc. They are diverse in shape, size and colour. Some species live alone (solitary) and some live in groups forming colonies. They attach themselves to floating logs, leaves or other substrate or move freely i.e. free swimming ### General characteristics: - Body consists of two embryonic layers. The outer one is ectoderm and the inner one is endoderm. - Body cavity known as coelenteron. It helps in digestion and circulation. - Ectoderm bears a special type of cells called cnidoblast. These cells help in locomotion, defense, capture of prey. **Example:** *Hydra, Obelia.* ## 3. Phylum-Platyhelminthes ### Habit and habitat: The life style of the member of this phylum is very colourful. Many species live on other organism as ecto-parasite (outside the body) or endo-parasite (inside the body). Some free living species live in fresh or saline water. Some animals of this phylum live in wet and damp soil. ### General characteristics: - Body flat, bisexual and mostly parasitic. - Eecto-parasite or endo-parasite. - Body covered with thick cuticle. - Body bears sucker and hooks. - Flame cell present and acting as excretory organ. - Digestive system incomplete or absent. **Example:** *Liver fluke, Tape worm.* ## 4. Phylum - Nematoda (Also called Nemathelminthes) ### Habit and habitat: Many animals of this phylum are endo-parasite and live in the intestine and blood. These parasitic animals living in human body and animals cause harm to them. On the other hand, many are free living. Which they live in water and soil. ### General characteristics: - Body tubular (cylindrical) and covered with thick skin. - Digestive system complete. Mouth and anus present. - Respiratory and circulatory system absent. - Generally unisexual. - Body cavity without lining and true coelom absent. **Example:** *Round worm, filaria worm.* ## 5. Phylum - Annelida ### Habit and habitat: Annelids are found in almost all temperate and tropical regions of the world. Many species live in damp soil, fresh water and some live in deep sea water also. A few species drag their burrows in stone and soil and live there ### General characteristics: - Body tubular and segmented. - Each segment contains setae that helps in locomotion (exception -no setae in leeches). - Nephridia present as excretory system. **Example:** *Earthworm, Leech.* ## 6. Phylum - Arthropoda ### Habit and habitat: Arthropoda is the largest phylum of the animal kingdom. They are extremely diverse group and occur in all habitat around the globe. Different species are adapted for life on land; in fresh, brackish and marine waters. Many species can fly with the help of wings. Some species live as parasite in (endoparasite) or on (ectoparasite) the bodies of plants and other animals. ### General characteristics: - Body segmented and with joint appendages. - Head bearing a pair of compound eyes and antenna. - Soft body covered with hard chitinous exoskeleton. - Body cavity filled with blood and is known as haemocoel. **Example:** *Butterfly, prawn, cockroach, crab.* ## 7. Phylum- Mollusca ### Habit and habitat: The members of this phylum show diversity in their body form, habit and habitat. They live in almost all environment of the world. They are mostly marine and live in different zones of the sea. Some species live in hills and forest, while some live in fresh water ### General characteristics: - Soft body, usually covered with hard shell. - Muscular foot used for locomotion. - Gaseous exchange (Respiration) takes place by lungs or gills. **Example:** *Snail, Mussel.* ## 8. Phylum: Echinodermata ### Habit and habitat: Echinoderms are all marine. They occur in all oceans of the world and at all depths. None of the members is found on land and in fresh water. They are mostly free living. ### General characteristics: - Dermal skin bears spine. - Body is divided into five equal parts (i.e. pentamerous). - No distinct head, dorsal and ventral surface in adults. - A unique water-vascular system is present and locomotion is done by tube feet. **Example:** *Starfish, Sea cucumber.* ## Lesson - 6-8 : Classification of vertebrate animals ## 9. Phylum - Chordata ### Habit and habitat: Chordate lives in all sorts of environment of the world (i.e the distribution is world wide). Many species are terrestrial in habit. Among aquatic chordates, many species live in fresh water or in ocean. Many species are arboreal, desert dweller, polar, cave-dwelling and flying in nature. There are many ectoparasitic chordate species which live on the bodies of other animals. ### General characteristics: - The notochord a rod-like unsegmented semirigid structure that forms a stiffening body axis throughout life or at some stage in the life cycle of each chordate. - Single, dorsal, tubular nerve cord present. - Pharyngeal pouches (gill slits) present throughout life or at some stages in the life cycle. **Example:** *Man, Toad, Carp (Rui) fish.* There are three sub-phylum under the phylum chordata. Such as- ### (a) Urochordata ### General characteristics: - Notochord present only in larval stage and restricted to the tail. - Gill slits and dorsal tubular nerve cord present only in the early stage of the life cycle. **Example:** *Ascidia, Salpa.* ### (b) Cephalochordata ### General characteristics: - Notochord and nerve cord found along the entire length of body and persist throughout life. - Looking like fish. **Example:** *Branchiostoma* ### (c) Vertebrata The member of this sub-phylum is known as vertebrate. Notochord is present only in embryonic stage and replaced by vertebral column in adults. Depending on structure and other characteristics, this sub-phylum is divided into seven classes. ### (I) Class-Cyclostomata ### General characteristics: - True jaws and paired appendages absent. - Fish like in form. - Body slender, eel-like, rounded with naked skin. - Respiration by gills. **Example:** *Petromyzon.* ### (II) Class-Chondrichthyes ### General characteristics: - All marine. - Cartilaginous skeleton. - Skin with placoid scales; 5-7 pairs of gills are present on both side of the head. - Streamlined body with heterocercal tail but no operculum. **Example:** *Shark, Sword fish.* ### (III) Class-Osteichthyes ### General characteristics: - Mostly fresh water fish. - Skin with cycloid, ctenoid or ganoid scales; some without scale. - Respiration primarily by gills. Four pair of gills are present on both side of the head. Gills are covered by operculum. **Example:** *Hilsa fish, Sea horse.* ### (IV) Class-Amphibia These animals can live under water breathing through their skin, but when on land they breathe by lungs. They lay their eggs in water and these hatch into larvae which breathe by gills. ### General characteristics: - Skin without scales. - Skin thin, soft, moist and with many glands. - Amphibians are cold-blooded animals. - Laying eggs in water. A tadpole hatches from the fertilized egg. **Example:** *Frog, Toad.* ### (V) Class-Reptilia ### General characteristics: - Skin dry and with scales. - They move by crawling. - Limbs paired, usually with five toes; absent in snakes and some lizards. **Example:** *Wall lizard, Crocodile, Snake.* ### (VI) Class-Aves ### General characteristics: - Body is covered with feather. - Two wings, two legs and one beak. - The presence of air sacs with lung helps in flight. - All birds are warm blooded. - Bones are light, strong, delicate and laced with air cavities. **Example:** *Crow, Duck, Magpie.* ### (VII) Class-Mammalia ### General characteristics: - Body covered with hair. - Female mammal suckle their young on milk from mammary glands. - Warm blooded animal - Four-chambered heart. - Teeth heterodont (Varying in structure and function). - All the mammal give birth to child. Example: Man, Camel, Royal Bengal Tiger. But their are some exception like Platypus. ## Lesson-9: Necessity of classification The unit of classification is called taxon, in plural taxa. The different taxa of animal nomenclature are adopted from International Code of Zoological Nomenclature (ICZN). The seven major taxa are as follows: Kingdom, Phylum, Class, Order, Family, Genus and Species. To identify an animal, taxonomists should match the characteristics of the animals with the above mentioned seven taxa. But in case of vertebrate, for example; man, snake, toad, fish etc. sub-phylum is usually added under phylum. All these ranks can be sub-divided to signify taxa that are intermediate between them. Classification is a scientific approach by which we can gather knowledge about different plants and animal easily. It saves labour, money and time. Classification is essential to identify any animal including the newly discovered one. Interrelationship between different animals can be determined with the help of classification. We can determine the systematic position of the organisms according to the evolutionary trend. Organisms can be arranged into different taxa by following definite rule. This also allows us to trace the affinity of one group of organism to other. It is useful to determine the collective and planned knowledge about organisms. For example, all acellular (Unicellular) animals are grouped under one phylum and all multicellular animals under nine phylum. **New words:** Taxonomy, binomial nomenclature, species, animalia, coelom, coelenteron, setae, notochord, larva, cycloid, ganoid. ## What we have learned at the end of this chapter - Vertebrata are advanced Animals. Their notochord is replaced by vertebral column consisting of hard vertebrae. - Respiration by gills in aquatic vertebrate and by lungs in land vertebrate. - Chordata is a phylum under the kingdom Animalia. Animals having notochord, nerve cord and pharyngeal gill slits are known as chordates. - Anterior part of the nerve cord is swollen and transformed into brain. The skull houses the brain and protect it. - Cellular layers of embryo that give rise to different organs are known as germ layer. - Mantle covers the soft body of molluscs. They use their muscular foot for locomotion. ## Exercise ### Fill in the Blanks 1. Excretory system of liver fluke is _______. 2. Blood filled body cavity of prawn is known as _______. 3. _______ use muscular foot for locomotion. 4. Members of the sub-phylum _______ are known as vertebrate. 5. Members of the sub-phylum Urochordata have _______ in their tail. ### Short Answer Questions 1. How many parts are there in binomial nomenclature of an animal ? Mention the name of these parts. What is the scientific name of Man ? 2. Write the names of five known arthropods. 3. Which phylum does prawn belong to? What are the characteristies of this phylum. 4. Mention the characteristics of mammals. 5. What are the characteristics of Urochordata ? ### Multiple Choice Questions 1. Which animal belongs to the phylum Mollusca? - a. Crab - b. Leech - c. Starfish - d. Mussel Radial symmetry applies to those forms that can be divided into similar halves by more than two planes passing through one main axis. Example-Starfish. - Cavity surrounded by body wall is known as coelenteron. It acts as digestive as well as circulatory system. - The space filled with fluid between body wall and the alimentary canal of multicellular animal is known as coelom. - Haemocoel is filled with blood and acts as a part of circulatory system. - Arthropoda is the largest phylum of the animal kingdom. Harmful insects are known as pest.