Animal Kingdom Chapter 4

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Questions and Answers

What is the defining characteristic of animals belonging to phylum Chordata?

Presence of exoskeleton

Presence of gills

Presence of notochord (correct)

Presence of scales

Phylum Chordata is divided into three subphyla: Urochordata or Tunicata, Cephalochordata, and __________.

Vertebrata

All vertebrates are chordates but not all chordates are vertebrates.

True

What replaces the notochord in adult vertebrates?

cartilaginous or bony vertebral column Signup and view all the answers

What are the two basic body forms of cnidarians?

polyp and medusa Signup and view all the answers

Which phylum includes sea walnuts or comb jellies?

Ctenophora Signup and view all the answers

Ctenophores exhibit radial symmetry.

True Signup and view all the answers

In Phylum Aschelminthes, the body is circular in _______-section.

cross Signup and view all the answers

What is the basis of animal classification?

Features common to various individuals in relation to the arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory, or reproductive systems. Signup and view all the answers

Match the following examples with their respective phylum:

Physalia, Adamsia, Pennatula = Cnidaria Taenia, Fasciola, Planaria = Platyhelminthes Ascaris, Wuchereria, Ancylostoma = Aschelminthes Signup and view all the answers

Animals with radial symmetry can be divided into two identical halves by any plane passing through the central axis of the body.

False Signup and view all the answers

Which animals exhibit tissue level of organization?

Coelenterates Signup and view all the answers

In triploblastic animals, the developing embryo has ___ germinal layer.

three Signup and view all the answers

Match the following germinal layers with the correct animal classification:

Diploblastic = Coelenterates Triploblastic = Platyhelminthes to chordates Signup and view all the answers

What are the difficulties that you would face in classification of animals if common fundamental features are not taken into account?

Difficulties in distinguishing and categorizing different animal groups. Signup and view all the answers

If you are given a specimen, what are the steps that you would follow to classify it?

Examine its characteristics, compare with known animal classifications, and identify key traits for classification. Signup and view all the answers

How useful is the study of the nature of body cavity and coelom in the classification of animals?

It helps in determining evolutionary relationships and understanding anatomical variations within animal groups. Signup and view all the answers

What is the difference between direct and indirect development?

Direct development involves a gradual growth and maturation process without distinct larval forms, whereas indirect development includes larval stages and metamorphosis. Signup and view all the answers

Distinguish between intracellular and extracellular digestion.

Intracellular digestion occurs within cells through the breakdown of food particles, while extracellular digestion takes place outside cells in a specialized cavity or organ. Signup and view all the answers

What are the peculiar features that you find in parasitic platyhelminthes?

Parasitic platyhelminthes exhibit suckers and hooks to attach to hosts, lack a proper body cavity, and have specialized adaptations for parasitic lifestyles. Signup and view all the answers

What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?

Arthropods are diverse, adaptable to various environments, have jointed appendages for movement, and exhibit high reproductive capacity. Signup and view all the answers

Water vascular system is the characteristic of which group of the following?

Echinodermata Signup and view all the answers

"All vertebrates are chordates but all chordates are not vertebrates". Justify the statement.

Vertebrates are a subgroup within the chordates that possess a vertebral column, whereas chordates include all animals with a notochord at some stage of their lives, which may or may not develop into vertebrae. Signup and view all the answers

How important is the presence of air bladder in Pisces?

The air bladder in Pisces helps in regulating buoyancy, maintaining stability in water, and controlling the depth at which the fish swims. Signup and view all the answers

What are the modifications that are observed in birds that help them fly?

Birds have lightweight bones, powerful flight muscles, aerodynamic feathers, and unique respiratory systems to support flight. Signup and view all the answers

Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?

No, the number of offspring produced by oviparous and viviparous mothers cannot be equal because oviparous animals lay eggs externally, while viviparous animals give birth to live young, limiting the potential number of offspring in viviparity. Signup and view all the answers

Segmentation in the body is first observed in which of the following?

Annelida Signup and view all the answers

Match the following:

Operculum = Mollusca Parapodia = Annelida Scales = Reptilia Comb plates = Ctenophora Radula = Mollusca Hairs = Mammalia Choanocytes = Porifera Gill slits = Chordata Signup and view all the answers

Prepare a list of some animals that are found parasitic on human beings.

Examples of parasitic animals that infest humans include lice, tapeworms, hookworms, fleas, and mites. Signup and view all the answers

Study Notes

Animal Kingdom

The need for classification of animals arises due to the vast diversity of over a million species, which helps in assigning a systematic position to newly described species.

Basis of Classification

Fundamental features common to various animals, such as:
- Arrangement of cells
- Body symmetry
- Nature of coelom
- Patterns of digestive, circulatory, or reproductive systems
- Are used as the basis of animal classification

Levels of Organisation

Animals exhibit different levels of organisation, including:
- Cellular level (e.g., sponges)
- Tissue level (e.g., coelenterates)
- Organ level (e.g., platyhelminthes and other higher phyla)
- Organ system level (e.g., annelids, arthropods, molluscs, echinoderms, and chordates)

Symmetry

Animals can be categorised based on their symmetry, including:
- Asymmetrical (e.g., sponges)
- Radial symmetry (e.g., coelenterates, ctenophores, and echinoderms)
- Bilateral symmetry (e.g., annelids, arthropods, and chordates)

Diploblastic and Triploblastic Organisation

Animals can be classified based on the number of germinal layers, including:
- Diploblastic (e.g., coelenterates)
- Triploblastic (e.g., platyhelminthes to chordates)

Coelom

Animals can be classified based on the presence or absence of a coelom, including:
- Coelomates (e.g., annelids, molluscs, arthropods, echinoderms, hemichordates, and chordates)
- Pseudocoelomates (e.g., aschelminthes)
- Acoelomates (e.g., platyhelminthes)

Segmentation

Some animals exhibit segmentation, including:
- Metameric segmentation (e.g., earthworm)

Notochord

Animals can be classified based on the presence or absence of a notochord, including:
- Chordates (e.g., animals with a notochord)
- Non-chordates (e.g., animals without a notochord)

Classification of Animals

The broad classification of Animalia is based on common fundamental features, including:
- Phylum Porifera (e.g., sponges)
- Phylum Coelenterata (e.g., cnidarians)
- Phylum Ctenophora (e.g., sea walnuts or comb jellies)
- Phylum Platyhelminthes (e.g., flatworms)
- Phylum Aschelminthes (e.g., roundworms)
- Phylum Annelida (e.g., segmented worms)
- Phylum Arthropoda (e.g., insects, arachnids, and crustaceans)
- Phylum Mollusca (e.g., molluscs)

Phylum Porifera

Characteristics of phylum Porifera, including:
- Cellular level of organisation
- Asymmetrical or radial symmetry
- Water transport or canal system
- Skeleton made up of spicules or spongin fibres
- Sexes are not separate
- Reproduction takes place by both asexual and sexual means

Phylum Coelenterata (Cnidaria)

Characteristics of phylum Coelenterata, including:
- Radial symmetry
- Tissue level of organisation
- Cnidoblasts or cnidocytes present
- Two basic body forms: polyp and medusa
- Alternation of generation (metagenesis)

Phylum Ctenophora

Characteristics of phylum Ctenophora, including:
- Radial symmetry
- Tissue level of organisation
- Eight external rows of ciliated comb plates
- Bioluminescence
- Sexes are not separate
- Reproduction takes place only by sexual means

Phylum Platyhelminthes

Characteristics of phylum Platyhelminthes, including:
- Bilateral symmetry
- Triploblastic and acoelomate
- Organ level of organisation
- Hooks and suckers present in parasitic forms
- Specialised cells called flame cells help in osmoregulation and excretion

Phylum Aschelminthes

Characteristics of phylum Aschelminthes, including:
- Bilateral symmetry
- Triploblastic and pseudocoelomate
- Organ-system level of organisation
- Alimentary canal is complete
- Sexes are separate
- Fertilisation is internal and development may be direct or indirect

Phylum Annelida

Characteristics of phylum Annelida, including:
- Bilateral symmetry
- Triploblastic and coelomate
- Organ-system level of organisation
- Metamerically segmented
- Longitudinal and circular muscles
- Closed circulatory system
- Nephridia help in osmoregulation and excretion
- Neural system consists of paired ganglia and a double ventral nerve cord

Phylum Arthropoda

Characteristics of phylum Arthropoda, including:
- Bilateral symmetry
- Triploblastic and coelomate
- Organ-system level of organisation
- Segmented
- Jointed appendages
- Chitinous exoskeleton
- Respiratory organs: gills, book gills, book lungs, or tracheal system
- Circulatory system is of open type
- Sensory organs: antennae, eyes, statocysts, or balancing organs
- Excretion takes place through malpighian tubules
- Mostly dioecious
- Fertilisation is usually internal
- Development may be direct or indirect

Phylum Mollusca

Characteristics of phylum Mollusca, including:
- Bilateral symmetry
- Triploblastic and coelomate
- Organ-system level of organisation
- Soft, unsegmented body
- Molluscan shell made up of calcium carbonate
- Foot, head, and visceral mass
- Radula (tooth-like structure) for feeding
- Respiratory organs: gills, lungs, or book lungs
- Circulatory system is of open type
- Excretion takes place through nephridia
- Dioecious or monoecious
- Fertilisation is usually internal
- Development may be direct or indirect### Molluscs
Molluscs are terrestrial or aquatic animals with an organ-system level of organisation
They are bilaterally symmetrical, triploblastic, and coelomate animals
Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot, and visceral hump
Soft and spongy layer of skin forms a mantle over the visceral hump
Space between the hump and the mantle is called the mantle cavity, where feather-like gills are present
Anterior head region has sensory tentacles
Mouth contains a file-like rasping organ for feeding, called radula
Examples: Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil fish)

Echinodermata

These animals have an endoskeleton of calcareous ossicles, hence the name Echinodermata (Spiny bodied)
All are marine with an organ-system level of organisation
Adult echinoderms are radially symmetrical, but larvae are bilaterally symmetrical
They are triploblastic and coelomate animals
Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side
Most distinctive feature is the presence of a water vascular system, which helps in locomotion, capture, and transport of food and respiration
Examples: Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber)

Hemichordata

Hemichordates have a rudimentary structure in the collar region called stomochord, similar to notochord
Body is cylindrical and is composed of an anterior proboscis, a collar, and a long trunk
Circulatory system is of open type
Respiration takes place through gills
Excretory organ is proboscis gland
Examples: Balanoglossus and Saccoglossus

Chordata

Animals belonging to phylum Chordata are fundamentally characterised by the presence of a notochord, a dorsal hollow nerve cord, and paired pharyngeal gill slits
They are bilaterally symmetrical, triploblastic, coelomate with an organ-system level of organisation
They possess a post-anal tail and a closed circulatory system
Examples: Ascidia, Salpa, Doliolum, Branchiostoma (Amphioxus or Lancelet)

Subphylum Vertebrata

Vertebrates possess notochord during the embryonic period, but it is replaced by a cartilaginous or bony vertebral column in the adult
Besides the basic chordate characters, vertebrates have a ventral muscular heart with two, three or four chambers, kidneys for excretion and osmoregulation, and paired appendages which may be fins or limbs
Examples: Petromyzon (Lamprey), Myxine (Hagfish), Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark)

Class Cyclostomata

All living members are ectoparasites on some fishes
They have an elongated body bearing 6-15 pairs of gill slits for respiration
Body is devoid of scales and paired fins
Circulation is of closed type
Examples: Petromyzon (Lamprey) and Myxine (Hagfish)

Class Chondrichthyes

They are marine animals with a streamlined body and have cartilaginous endoskeleton
Mouth is located ventrally
Notochord is persistent throughout life
Gill slits are separate and without operculum (gill cover)
Skin is tough, containing minute placoid scales
Teeth are modified placoid scales which are backwardly directed
Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray)

Class Osteichthyes

It includes both marine and fresh water fishes with a bony endoskeleton
Body is streamlined
Mouth is mostly terminal
They have four pairs of gills which are covered by an operculum on each side
Skin is covered with cycloid/ctenoid scales
Air bladder is present which regulates buoyancy
Heart is two-chambered (one auricle and one ventricle)
Examples: Hippocampus (Sea horse), Catla (Katla), Clarias (Magur), Betta (Fighting fish), Pterophyllum (Angel fish)

Class Amphibia

Amphibians can live in aquatic as well as terrestrial habitats
Most of them have two pairs of limbs
Body is divisible into head and trunk
Tail may be present in some
Skin is moist without scales
The eyes have eyelids
Respiration is by gills, lungs, and through skin
Heart is three-chambered (two auricles and one ventricle)
Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia)

Class Reptilia

The class name refers to their creeping or crawling mode of locomotion
They are mostly terrestrial animals and their body is covered by dry and cornified skin, epidermal scales or scutes
They do not have external ear openings
Tympanum represents ear
Limbs, when present, are two pairs
Heart is usually three-chambered, but four-chambered in crocodiles
Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Crocodilus (Crocodile), Alligator (Alligator), Hemidactylus (Wall lizard), Naja (Cobra), Bangarus (Krait), Vipera (Viper)

Class Aves

The characteristic features of Aves (birds) are the presence of feathers and most of them can fly except flightless birds
They possess beak
Forelimbs are modified into wings
Hind limbs generally have scales and are modified for walking, swimming or clasping the tree branches
Skin is dry without glands except the oil gland at the base of the tail
Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic)
Heart is completely four-chambered
Examples: Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture)

Class Mammalia

They are found in a variety of habitats – polar ice caps, deserts, mountains, forests, grasslands, and dark caves
Some of them have adapted to fly or live in water
The most unique mammalian characteristic is the presence of milk-producing glands (mammary glands) by which the young ones are nourished
They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming or flying
Skin is unique in possessing hair
External ears or pinnae are present
Different types of teeth are present in the jaw
Heart is four-chambered
Examples: Oviparous-O rnithorhynchus (Platypus); Viviparous-Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion)### Classification of Animals
The classification of animals is based on fundamental features such as level of organization, symmetry, cell organization, coelom, segmentation, notochord, etc.

Characteristics of Different Phyla

Porifera: multicellular animals with cellular level of organization, characteristic flagellated choanocytes
Coelenterates: tentacles, bear cnidoblasts, mostly aquatic, sessile or free-floating
Ctenophores: marine animals with comb plates
Platyhelminths: flat body, bilateral symmetry, parasitic forms have distinct suckers and hooks
Aschelminthes: pseudocoelomates, parasitic and non-parasitic roundworms
Annelids: metamerically segmented animals with a true coelom
Arthropods: jointed appendages, most abundant group of animals
Molluscs: soft body surrounded by an external calcareous shell, external skeleton made of chitin
Echinoderms: spiny skin, water vascular system
Hemichordates: worm-like marine animals, cylindrical body with proboscis, collar, and trunk
Chordata: notochord either throughout or during early embryonic life, dorsal, hollow nerve cord, paired pharyngeal gill slits

Characteristics of Vertebrates

Agnatha: most primitive chordates, ectoparasites on fishes, represented by class Cyclostomata
Gnathostomata: jaws, two superclasses - Pisces and Tetrapoda
Pisces: fins for locomotion, classes Chondrichthyes and Osteichthyes
Chondrichthyes: fishes with cartilaginous endoskeleton, marine
Tetrapoda: two pairs of limbs, classes Amphibia, Reptilia, Aves, and Mammalia
Amphibia: adapted to live both on land and water
Reptilia: dry and cornified skin, limbs absent in snakes
Aves: warm-blooded, feathers, forelimbs modified into wings for flying
Mammalia: presence of mammary glands, hairs on the skin, viviparity

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