Animal Kingdom

Summary

The basic fundamental features such as level of organisation, symmetry, cell organisation, coelom, segmentation, notochord, etc., have enabled us to broadly classify the animal kingdom. Besides the fundamental features, there are many other distinctive characters which are specific for each phyla or class.

Porifera includes multicellular animals which exhibit cellular level of organisation and have characteristic flagellated choanocytes. The coelenterates have tentacles and bear cnidoblasts. They are mostly aquatic, sessile or free-floating. The ctenophores are marine animals with comb plates. The platyhelminths have flat body and exhibit bilateral symmetry. The parasitic forms show distinct suckers and hooks. Aschelminthes are pseudocoelomates and include parasitic as well as non-parasitic roundworms.

Annelids are metamerically segmented animals with a true coelom. The arthropods are the most abundant group of animals characterised by the presence of jointed appendages. The molluscs have a soft body surrounded by an external calcareous shell. The body is covered with external skeleton made of chitin. The echinoderms possess a spiny skin. Their most distinctive feature is the presence of water vascular system. The hemichordates are a small group of worm-like marine animals. They have a cylindrical body with proboscis, collar and trunk.

Phylum Chordata includes animals which possess a notochord either throughout or during early embryonic life. Other common features observed in the chordates are the dorsal, hollow nerve cord and paired pharyngeal gill slits. Some of the vertebrates do not possess jaws (Agnatha) whereas most of them possess jaws (Gnathostomata). Agnatha is represented by the class, Cyclostomata. They are the most primitive chordates and are ectoparasites on fishes. Gnathostomata has two super classes, Pisces and Tetrapoda. Classes Chondrichthyes and Osteichthyes bear fins for locomotion and are grouped under Pisces. The Chondrichthyes are fishes with cartilaginous endoskeleton and are marine. Classes, Amphibia, Reptilia, Aves and Mammalia have two pairs of limbs and are thus grouped under Tetrapoda. The amphibians have adapted to live both on land and water. Reptiles are characterised by the presence of dry and cornified skin. Limbs are absent in snakes. Fishes, amphibians and reptiles are poikilothermous (coldblooded). Aves are warm-blooded animals with feathers on their bodies and forelimbs modified into wings for flying. Hind limbs are adapted for walking, swimming, perching or clasping. The unique features of mammals are the presence of mammary glands and hairs on the skin. They commonly exhibit viviparity.

Animal Kingdom

Phylum - Chordata

- presence of notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits

- symmetry bilateral, triploblastic, coelomate with organ system level of organisation

- possess - post anal tail & closed circulatory system

Q. what is notochord?

Ans. The notochord is an embryonic midline structure common to all members of the phylum Chordata, providing both mechanical and signaling cues to the developing embryo. In vertebrates, the notochord arises from the dorsal organizer and it is critical for proper vertebrate development.

MCQs

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Q1 Consider the following features: (A) Organ system level of organisation; (B) Bilateral Symmetry; (C) True Coelomates with segmentation of body

Select the correct option of animal groups which possess all the above characteristics.

a. annelida, mollusca, and chordata

b. annelida, arthropoda, and chordata

c. annelida, arthropoda, and mollusca

d. arthropoda, mollusca and chordata

Ans. b. annelida, arthropoda and chordata

Explanation: Mollusca shows organ system level of organisation with unsegmented body (except Neopilina which is a segmented mollusca) having distinct head, muscular foot and visceral hump. They usually show bilateral symmetry but some molluscs (example Pila) become asymmetrical due to torsion.

Q2 Which of the following animals are true coelomates with bilateral symmetry?

a. Adult echinoderms

b. aschelminthes

c. Platyhelminthes

d. Annelids

Ans.d. Annelids

Q3. Which of the following kinds of animals are triploblastic

a. Flatworms

b. Sponges

c. Ctenophores

d. Corals

Ans. a.Flatworms

Explanation: Triploblastic is a condition which describes an animal having a body composed of three embryonic germ layers: the ectoderm, mesoderm and endoderm. Most multicellular animals belonging to Phylum Platyhelminthes to Phylum Chordata are triploblastic. Ctenophores, sponges and corals are diploblastic.

Q4 Which one of the following statements about certain given animals is correct?

a. Roundworms (Aschelminthes) are pseudocoelomates

b. Molluscs are acoelomates

c. Insects are pseudocoelomates

d. Flatworms (Platyhelminthes) are coelomates.

Ans. a. Roundworms (Aschelminthes) are pseudocoelomates

Explanation: Acoelomates are animals having no body cavity or coelom. Examples are porifera, coelenterates, ctenophora, platyhelminthes. In pseudocoelomates, body space is pseudocoelom or false coelom. Examples are aschelminthes. In coelomates, body space is a true coelom enclosed by mesoderm on both sides. Remaining phyla from annelida to arthropoda are coelomates. Molluscs are insects are coelomates while flatworms are acoelomates.

Q5 Which one of the following groups of animals is bilaterally symmetrical and triploblastic?

a. Aschelminthes (roundworms)

b. Ctenophores

c. Sponges

d. Coelenterates (Cnidarians)

Ans.a. Aschelminthes (roundworms)

Explanation: Aschelminthes is a phylum consisting of pseudocoelomates. These are mostly aquatic, free living or parasitic. Their body is slender, bilaterally symmetrical and triploblastic.

Q.6 Metameric segmentation is the characteristic of

a. mollusca and chordata

b. platyhelminthes and arthropoda

c. Echinodermata and Annelida

d. annelida and arthropoda

Ans.d. annelida and arthropoda

Explanation: The term metamerism refers to a linear repetition of parts in an animal body. It occurs in three highly organised phyla Annelida, Arthropoda, and Chordata. Each segment is called a metamere, or somatic. Segmentation often affects both external and internal structures. Such a condition is called metameric segmentation. In chordates, the segmentation is apparent only in the embryonic stage. In the adult chordates, segmentation is visible in the internal structures, such as vertebrae, ribs, nerves and blood vessels.

Q7. The animals with bilateral symmetry in young stage and radial pentamerous symmetry in the adult stage, belong to the Phlum

a. Annelida

b. Mollusca

c. Cnidaria

d. Echinodermata

Ans. d. Echinodermata

Explanation: Echinoderms are triploblastic animals with organ system level of organisation. Larval forms possess bilateral symmetry while adults have radial symmetry.

Q8 Which of the following animals have scattered cells with cell-tissue grade organisation?

a. Sponge

b. Hydra

c. Liver Fluke

d. Ascaris

Ans. b. Hydra

Explanation: Hydra, has tissue level of organisation. Its body is multicellular and the cells occur in 2 distinct layers or tissues of specialized cells. Sponges have cellular level of organisation. Liver fluke and Ascaris have organ-system level of organisation.

Q9 Coelom is found between

a. body wall and ectoderm

b. ectoderm and endoderm

c. mesoderm and body wall (endoderm)

d. mesoderm and ectoderm

Ans. c. mesoderm and body wall (endoderm)

Explanation: Coelom is a fluid-filled cavity that forms the main body cavity of vertebrate and most invertebrate animals. It is found between mesoderm and body wall (endoderm)

Q10 Besides annelida and arthropoda, the metamerism is exhibited by

a. mollusca

b. acanthocephala

c. cestoda

d. chordata

Ans.d. chordata

Q11. Bilaterally symmetrical and acoelomate animals are exemplified by

a. ctenophora

b. platyhelminthes

c. aschelminthes

d. annelida

Ans. b. Platyhelminthes

Explanation: - Platyhelminthes are bilaterally symmetrical, triploblastic and acoelomate animals with organ level of organisation.

Q12. Match the following columns and select the correct option.

1. 6-15 pairs of gill slits i. Trygon

2. Heterocercal caudal fin ii. Cyclostomes

3. Air bladder iii. Chondrichthyes

4. Poison sting iv. Osteichthyes

a. 1-ii 2-iii 3-iv 4-i

b. 1-iii 2-iv 3-i 4-ii

c. 1-iv 2-ii 3-iii 4-i

d. 1-i 2-iv 3-iii 4-ii

Ans.a. 1-ii 2-iii 3-iv 4-i

Explanation: Cyclostomes - 6-15 pairs of gill slits, Chondrichthyes-Heterocercal caudal fin, Osteichthyes-Air bladder, Trygon-Poison sting

Q13 Which of the following statements are true for the Phylum chordata?

a. In urochordata, notochord extends from head to tail and it is present throughout their life

b. in vertebrata, notochord is present during the embryonic period only

c. Central nervous system is dorsal and hollow

d. Chordata is divided into 3 subphyla: Hemichordata, Tunicata and Cephalochordata

Ans. d

Explanation: In urochordata, notochord is present only in larval tail. Phylum chordata is divided into three subphyla: Urochordata or Tunicata, Cephalochordata and Vertebrata.

Q14 Match the following columns

1. Gregarious, polyphagous pest i. Asterias

2. Adult with radial symmetry and larva with bilateral symmetry ii. scorpion

3. book lungs iii. Ctenoplana

4. Bioluminescence iv. Locusta

a. 1-i 2-iii 3-ii 4-iv

b. 1-iv 2-i 3-ii 4-iii

c. 1-iii 2-ii 3-i 4-iv

d. 1-ii 2-i 3-iii 4-iv

Ans.b.1-iv 2-i 3-ii 4-iii

Explanation: - Locusta -Gregarious, polyphagous pest; Asterias - Adult with radial symmetry and larva with bilateral symmetry; scorpion - book lungs; Ctenoplana-Bioluminescence

Q15 Match the following organisms with respective characteristics

1. Pila i. Flame cells

2. Bombyx ii. Comb plates

3. Pleurobrachia iii. Radula

4. Taenia iv. Malpighian tubules

a. 1-iii 2-ii 3-iv 4-i

b. 1-iii 2-ii 3-i 4-iv

c. 1-iii 2-iv 3-ii 4-i

d. 1-ii 2-iv 3-iii 4-i

Ans. c. 1-iii 2-iv 3-ii 4-i

Explanation: - Radula-Pila; Malpighian tubules-Bombyx; Comb plates-Pleurobrachia; Flame cells-Taenia

the buccal cavity of Pila (apple snail) possess rasping organ, radula, with transverse row of teeth for cutting grass. Bombyx (silk moth), an insect has Malpighian tubules, as excretory organ. Pleurobrachia is a ctenophore having eight ciliary plates called comb plates. Taenia is a platyhelminth having flame cells for excretion and osmoregulation.