Andhra Pradesh BIEAP AP Inter 1st Year Zoology Study Material Lesson 3 Animal Diversity-I: Invertebrate Phyla Textbook Questions and Answers.
AP Inter 1st Year Zoology Study Material Lesson 3 Animal Diversity-I: Invertebrate Phyla
Very Short Answer Type Questions
What physical feature pertaining to the organism and its medium do you notice in a sponge body form in which sponges can be/were identified as animals and not plants? What do you call the region in the sponge body in which you noticed that feature?
Sponges are primitive multicellular and sessile animals and have a cellular level of organisation. The body wall is composed of two layers separated by matrix mosohyl, and are heaving canal system for transport of water through Ostia, having a cavity in the body called a spongocoel hence the sponge are animals and are not plants.
What are the different structures that make up the internal skeleton of a sponge? What are the chemicals involved in the formation of these structures?
The internal skeleton of a sponge is made up of different types of spicules.
Calcareous spicules made up of CaCO3.
Siliceous spicules – are made up of Silicon dioxide – glass.
What are the functions of the canal system of sponges?
The functions of the canal system of a sponge are gathering of food, respiratory exchange of gases, and removal of wastes.
What are the two chief morphological ‘body forms’ of cnidarians? What are their chief functions?
The body form of Cnidarians is polyp and medusa. Polyp produces medusae by asexual reproduction. Medusae produce polyps by sexual reproduction.
What is metagenesis? Animals belonging to which phylum exhibit metagenesis?
Cnidarians show two basic body forms called polyp and medusa. Cnidarians which exist in both forms exhibit alternation of generations called metagenesis.
What is the cnidarian group with quantitatively/relatively large mesoglea? What is the significance of such a well-developed mesoglea pertaining to the aquatic life of that group?
The Scyphozoa of cnidarian animals have large mesoglea, it is the significance of these animals.
What is the chief difference between the hydrozoans and the rest, of the cnidarians regarding the germinal layer (s) in which its ‘defencive structures or cells of defence occur?
The defencive structures Cnidocytes or Cnidoblasts occur only in the ectoderm, in the hydrozoans in the rest of the Cnidarians the cnidocytes occur in both ectoderm and endoderm.
What are the excretory cells of flatworms called? What is the other important function of these specialized cells?
The excretory cells of flatworms are flame cells. Another important function of these specialized cells is osmoregulation.
Distinguish between amphids and phasmids.
Amphids: These are the cuticular depressions present on the lips surrounding the mouth in the nematodes such as Aphasmidia animals and serve as Chemoreceptors.
Phasmids: These are the well-developed sensory organs and they occur in some nematodes such as phasmidia animals.
What is the essential difference between a ‘flat worm’ and a ’round worm’ with reference to the perivisceral area of the ‘bodies’.
With the reference to the perivisceral area of the body, the flatworms have dorso-ventrally flattened bodies. The body is not segmented, but some of the animals exhibit pseudometamerism. In the Nematoda the body is circular in cross-section, hence the name roundworms, body is not segmented.
How do you account for the origin of the perivisceral space in the body of a nematode and an annelid?
The perivisceral space in the body of a nematode is circular in cross-section. Hence the name ‘wound worms’ body unsegmented. In an annelid, the body is segmented by septa into segments or metameres (annulus – little rings) some of them (Nereis) possess lateral appendages parapodia.
What is metamerism? What is the essential difference between the mode of formation of individual morphological body units of a tapeworm and those of an earthworm?
The body is divided into segments like units called metameres. Like the divination in known as metamerism.
In tapeworm body segments are pseudometameres.
In earthworms, body segments are true segments or metameres.
How do you distinguish a ‘hirudineaun’ from the rest of the annelids, based on the morphological features pertaining to metamerism? How does the coelom of a leech differ from the coelom of an earthworm with reference to its contents?
In hirudinean like Leach, the body is with a definite number of segments. The segments are externally sub-divided into annute, internal segmentation’ is absent.
In Leech coelom is filled with a characteristic tissue called botryoidal tissue. In earthworms, the coelom is filled with coelomic fluid.
What do you call the locomotor structures of Nereis? Why is Nereis called a polychaete?
Locomotor structures of Nereies are parapodia. The parapodia bear many setae that help in locomotion hence the name Polychaeta.
What is botryoidal tissue?
The coelom of Leech is filled with a characteristic tissue called botryoidal tissue, it is resembling a bunch of grapes. They range from excretion to storage of iron, calcium, and revascularization in areas of injury.
What is the difference between the epidermis of a Nematoda and that of an annelid? How does a nematode differ from an annelid with reference to the musculature of the body wall?
The epidermis of Nematoda is syncytial and the epidermis of annelid animals is informed by one cell thick ectodermal epithelial cells.
What do you call the first and second pairs of cephalic appendages of a scorpion?
The first and second pairs of cephalic appendages of a Scorpion are Chelicerae and Pedipalpi.
What is the uniqueness of the first two pairs of cephalic appendages of a crustacean compared to those of the other extant arthropods?
In crustaceans, cephalic appendages are two pairs of antennae (antennules and antennae). It is the unique feature of Crustaceans compared to those of the other extent arthropods.
What is the sub-phylum to which ‘ticks’ and ‘mites’ belong? How do you distinguish them from insects with reference to their walking legs?
Ticks and mites belongs to the sub-phylum Chelicerata and class Arachnida. These have four pairs of walking legs.
What are the respiratory structures of Limulus and Palamnaeus respectively?
The respiratory structures of Limulus are book gills, and in palamnaeus are book-lungs.
What ara antennae? What is the arthropod group without antennae?
Antennae are the sensory organs, of the animals of sub-phylum-Mandibulata of arthropod bear antennae.
What do you call the perivisceral cavity of an arthropod? Where from is it derived during development?
The perivisceral cavity of an Arthropoda is a haemocoel, it is not true coelom, but derived from mostly the embryonic blastocoel.
Which arthropod, you have studied, is called a living fossil? Name its respiratory organs.
The arthropod animal Limulus is called a living fossil, it is respiratory organs are book-gills.
How do you identify a Chiton from its external appearance? How many pairs of gills help in the respiration of Chiton?
Chiton is bilaterally symmetrical and dorsoventrally flattened. Shell is dorsal and consists of eight transverse plates. Poat is ventral elongated and flat. Gills are 6 to 88 pairs helps in respiration.
What is the function of the radula? Give the name of the group of mollusks that do not possess a radula.
The buccal cavity contains a file-like rasping organ called radula for feeding, except for the bivalves and tusk of Molluscs.
What is the other name for the gill of a mollusc? What is the function of osphradium?
The other name for the gill of a mollusc is Ctenidia. The main function of Osphradium is to test the purity of water.
What is Aristotle’s lantern 7 Give one example of an animal possessing it?
In the mouth of the sea Urchin a complex five Jawed masticatory apparatus called Aristotle’s Lantern.
What is the essential difference between the Juveniles and adults of echinoderms, symmetry-wise?
The adult echinoderms are radially symmetrical (pentamerous radial symmetry), but Juveniles (Larvae) are bilaterally Symmetrical.
What are blood glands in pheretima?
Blood glands are present in the 4th, 5th, and 6th segments of pheretima. They produce blood cells and haemoglobin which is dissolved in the plasma.
What are spermathecae on the body of pheretima?
In Pheretima there are four pairs of spermothecae are located in the segments 6th to 9th as one pair in each segment. This receives and stores spermatozoa during copulation.
Short Answer Type Questions
Write short notes on the salient features of the anthozoans.
- Anthozoans are commonly referred to as sea anemones.
- Anthozoa includes sea anemones, corals, and sea pens.
- All are marine forms. These are solitary or colonial.
- They are sedentary and only have polypoid information.
- Coeienteron is divided into several compartments by vertical septa called mesenteries.
- Mesoglea contains connective tissue.
- Cnidocytes occur both in the ectoderm and endoderm and are cellular and contain amoebocytes.
- Germ cells are derived from the endoderm. Ex: Adamsia (sea anemone), Gorgonia (sea fan), Pennatula (sea pen).
What is the class to which the flukes belong? Write short notes on the chief characters of the group.
Flukes belong to the class Trematoda of Phylum-Platyhelminthes.
- Trematoda organs are commonly called flukes.
- These are parasitic on other animals.
- The body is covered by a thick cuticle and bears two suckers, an oral and a ventral.
- The mouth is anterior and the intestine is bifurcated.
- These are bisexual (monoecious).
- Life history is complex with many hosts and different types of stages – miracidium, sporocyst, redia, cercaria, etc. Ex: Fasciola (Liver fluke), Schistosoma (blood fluke).
What are the salient features exhibited by Polychaetes?
- These are commonly known as bristle worms.
- All are marine. Many are burrowing, others are free swimming or crawling or tubicolous.
- Head is distinct with sensory structures like eyes, antennae, palps, and cirri.
- Clitellum is absent.
- Each segment has a pair of lateral appendages called parapodia in which bundles of setae are arranged.
- Animals are unisexual. Most segments bear glands. Gonoducts are absent.
- Gametes are shed into the coelom.
- Fertilization is external.
- Development includes a trochophore larva. Ex: Nereis
How do the hirudineans differ from the polychaetes and oligochaetes?
- Definite number of body segments are present in hirudinean but many segments are present in polychaetes and earthworms.
- Locomotion in leeches is by suckers but body setae in oligochaetes and parapodia in polychaetes. Parapodia also help in respiration.
- Temporary clitellum during the breeding season is present in leeches but clitellum is absent in polychaetes and permanent clitellum is present in oligochaetes.
- Hirudineans are bisexuals, oligochaetes are bisexual and polychaetes are unisexual animals.
- Coelom is reduced on leeches, but coelom is spacious in oligochaetes and polychaetes.
- Development is direct in leeches and earthworms but indirect in polychaetes.
- Nutrient tissue called botryoidal tissue fills the coelom in hirudinean.
- Anterior and posterior suckers are present in hirudineans. Such suckers are absent in polychaetes and oligochaetes. Ex: Pheretima, Tubifex
What are the chief characteristics of crustaceans?
- This includes prawns, crabs, lobsters, crayfishes, etc.
- Mostly marine, a few are fresh water and some are adapted to terrestrial life.
- In most species, the head and thorax fuse to form a cephalothorax.
- Cephalic appendages are five pairs – first antennae (antennules) second antennae, mandibles, first maxillae and second maxillae.
- Thoracic and abdominal appendages are typically biramous
- Respiration is by gills.
- Excretory organs are green glands or antennal glands.
- Sense organs include statocysts, compound eyes, and antennae.
- Gonopores are paired.
- Development is direct or indirect involving several larval stages. The basic larva is nauplius. Ex: Palaemon (Prawn); Cancer (Crab).
Mention the general characters of Arachnida.
- This includes scorpions, spiders, ticks, and mites.
- Primarily they are all terrestrial.
- Prosoma bears one pair of pre-oral chelicerae, one pair of post-oral pedipalps, and four pairs of walking legs.
- In spiders each chelicera bears a fang into which the poison gland opens.
- Abdominal appendages are modified into book lungs, spinnerets, pectines, etc.
- Telsun is usually absent. It is present as a sting in scorpions.
- Respiration is by book lungs or tracheae.
- Excretory organs are coaxial glands and malpighian tubules.
- Scorpions are viviparous.
- Development is direct. Ex: Palamnaeus (scorpion); Aranea (spider).
Compare briefly a centipede and a millipede.
|1. Centipedes are commonly called a hundred leggers.||1. Millipedes are commonly called a thousand leggers.|
|2. Body is divided into the head and trunk.||2. Body is divided into the head, thorax, and abdomen.|
|3. Centipedes are carnivorous in nature.||3. Millipedes are herbivorous in nature.|
|4. In each segment one pair of appendages are present.||4. In each segment 2 pairs of appendages are present.|
|5. Single genital aperture occurs at the posterior end of the trunk.||5. Single genital aperture opens in the anterior part of the trunk.|
|6. Head bears one pair of antennae, one pair of mandibles, and two pairs of maxillae. Ex: Scolopendra.||6. Head bears paired antennae, mandibles, and maxillae. The maxillae are fused to form a plate-like under lip, the gnathochilarium-a masticatory structure. Ex: Spirostreptus.|
Cephalopods show several unique or advanced features when compared to the other molluscs. Discuss briefly.
- The class Cephalopoda includes cuttlefishes, squids, octopuses, nautilus, etc.
- The Head is discrete and bears very conspicuous eyes.
- Shell is either present (e.g.: Sepia) or absent (e.g.: Octopus). When present it may be multi-charactered and external (e.g.: Nautilus) or internal (e.g.: Loligo).
- The foot is modified into eight to ten arms (tentacles) present around the mouth and siphons.
- Some Cephalopods (e.g: Sepia) possess an ink gland as a defensive adaptation.
- Ctenidia are two or four in number – dibranchiate. e.g.: Sepia and tetrabranchiates. (e.g.: nautilus)
- The brain is complex and is protected by a cartilaginous cranium.
- Eyes are superficially similar to those of vertebrates.
- Development is direct. Ex: Architeuthis (giant squid).
Which class of Mollusca represents the primitive molluscs? What are their chief features?
The primitive molluscs are represents the class Aplacophora of Phylum-Mollusca.
These are primitive forms with ‘worm-like’ bodies. These are marine forms without mantle, shell, foot, and nephridia. The Head is poorly developed. A rasping organ radula is present in the buccal cavity. Cuticle contains calcareous spicules. Eyes, statocysts, and tentacles are absent. The heart consists of a single auricle and a ventricle. A pair of gonads are present in some, there is a mid-ventral groove that is homologous to the foot of the other molluscs.
Ex: Neonmia, Chaetoderma.
What are the salient features of the echinoids?
- It includes sea urchins, heart urchins, sand dollars, etc. The body is ovoid or discoidal and covered by movable spines.
- Arms are absent, tube feet are arranged in five bands, and bear suckers.
- Ossicles of the body unite to form a rigid test or corona or case.
- Pedicellaria is “three jawed”.
- Anus and madreporite are aboral in position.
- Ambulacral grooves are closed.
- A complex five-jawed masticatory apparatus called Aristotle’s lantern is present just inside the mouth. It is absent in heart urchins.
- Life history includes a larval form called echinopluteus.
- Specialized gills called peristomial gills as present in sea urchins. Eg: Salmacis (Sea urchin), Echino Cardium (Heart urchin), Clypeastoer (Cake Urchin).
Mention the salient features of Holothuroidea.
Holothuroidea: This class includes sea cucumbers. Body elongated in the oro-aboral axis. Arms, spines, and pedicellariae are absent skin are soft and leathery (Coriaceous). The dermis contains microscopic, isolated ossicles. The madreporite is internal, suspended in the perivisceral coelom. Tube feet are provided with suckers. The mouth is surrounded by retractile feeding tentacles, which are modified tube feet, chief gas exchange organs are a pair of respiratory trees that arise from the wall of the cloaca and form branched tubes in the perivisceral coelom. The development includes auricularia and doliolaria larvae.
Ex: Cueumaria, synaptic, Thyone.
What is the function of nephridia?
- The nephridia of pheretima are ectodermal in origin and are metanephridia.
- Several types of nephridia occur in pheretima but are fundamentally similar in structure.
- Which opens outside through the nephridiopore – The nephridia tolled open nephridia. Ex: Septal nephridia.
- Those who do not have nephridiopore are called closed-type nephridia. Ex: Pharyngeal nephridia.
- Those open at the outer surface are called exonephridia.
- The nephridia play an important role in osmoregulation.
- Earthworms mostly excrete urea as the excretory product and are described as ureotelic animals.
How many types of nephridia occur in pheretima and how do you distinguish them?
In Pheretima three types of nephridia are present.
- Septal nephridia: The septal nephridia are present on the intersegmental septum from 15 & 16 segments onwards to last and are opened into the alimentary canal.
- Integumentary nephridia: The integumentary nephridia attached to the inner body wall from the 3rd segment to the last. They open to the exterior on the body surface by nephridiopores.
- Pharyngeal nephridia: The pharyngeal nephridia present three paired tufts in the segments 4tfl, 5th, and 6th. They open into the buccal cavity and pharynx.
Give an account of the hearts in the circulatory system of pheretima.
Hearts in Pheretima: The dorsal blood vessel and the ventral blood vessel are connected by a pair of pulsatile hearts, in each of the seventh, ninth, twelfth, and thirteenth segments. Of these four pairs, the anterior two pairs connect only the dorsal blood vessel to the ventral blood vessel. Hence they are ’ called lateral hearts. The posterior two pairs connect both the dorsal blood vessel and the supra-oesophageal blood vessel with the ventral blood vessel. Hence, they are called lateral oesophageal hearts. These two types of hearts also differ in the number and arrangement of their valves. Four pairs of valves are present in each lateral heart, while three pairs of valves are present in each lateral oesophageal heart. Hearts allow the blood to flow into the ventral blood vessel only.
Long Answer Type Questions
Draw a labelled diagram of the reproductive organs of Pheretima.
Reproductive organs of pheretima: Pheretima is a hermaphrodite (bisexual). There are two pairs of testes. One pair each present in the 10th and 11th segments. Their vasa deferentia run up to the 18th segment where they join the prostatic ducts. Two pairs of seminal vesicles present in the 11th and 12th segments are sacs in which spermatogonia mature into spermatozoa. The common prostatic and spermatic ducts open to the exterior by a pair of male genital pores on the ventrolateral sides of the 18th segment. Two pairs of accessory glands’ are present one pair each in the 17th and 19th segments. Four pairs of spermathecae are located in the segments 6th to 9th (one pair in each segment). They receive and store spermatozoa (spermatophores) during copulation.
One pair of ovaries is attached to the posterior face of the inter-segmental septum of the 12th and 13th segments. Oviducal funnels are present beneath the ovaries and they continue into oviducts (14th segment). They join together and open to the exterior on the ventral side of the 14th segment by a single median female genital pore.
Describe the digestive system and process of digestion in pheretima.
The digestive system in pheretima: The alimentary canal is a straight tube and runs from the first to the last segment of the body. The mouth opens into the buccal cavity (1-3 segments) which leads into the muscular pharynx (4th segment). A small narrow tube, oesophagus (5-7 segments), continues into a muscular gizzard (8th segment). It helps in grinding the small particles of food in the decaying leaves (grinding mill). The stomach extends from segments 9 to 14. The food of earthworms is decaying leaves and other organic matter mixed with the soil. Calciferous glands, present in the stomach, neutralise the humic acid present in the humus of the soil. The intestine starts from the 15th segment and continues till the last segment.
A pair of short and conical intestinal caeca project from the intestine in the 26th segment. An internal median fold of the dorsal wall of the intestine called typhiosole, helping in increasing the area of absorption, is poorly developed in Pheretima (between the 26th and the rectum which occupies the last 23 to 28 segments). The alimentary canal opens to the exterior by a small rounded aperture called the anus. The ingested soil rich in organic matter passes through the digestive tract where digestive enzymes break down complex food into smaller absorbable units. These simpler molecules are absorbed through intestinal membranes and are utilized for various metabolic activities.
Process of digestion: Digestion in earthworms is extracellular. Earthworm obtains their nourishment from the organic debris (detritus) present in the soil. So it is called a detritivore. The pharynx is ejected due to the inside out of the buccal chamber. The pharynx, with the help of its radial-dilator muscles, works as a suction pump in feeding.
The organic food along with the swallowed soil particles is sucked into the pharynx, where it mixes with the salivary secretion. The mucin in the saliva lubricates the gut wall for the easy passage of food and also helps in the formation of the bolus. The proteolytic enzyme in the saliva partly digests the proteins. Then the food reaches the gizzard. Its circular muscle and the thick cuticle grind the food into fine particles. In this state, the food is easily acted upon by the digestive enzymes in the stomach and intestine.
The intestinal juice of an earthworm is comparable to the pancreatic juice of higher animals. All these enzymes like proteases, amylases, and lipases act upon the finely ground food and digest the organic matter in it. Proteases digest proteins into amino acids, amylases digest carbohydrates into glucose and lipases digest lipids into fatty acids and glycerol.
The digested food is absorbed by the intestinal epithelium in the typhlosolar region. The extensive capillary network of blood vessels of the intestine plays a vital role in absorption. The typholosole helps in increasing the area of absorption. The undigested food then passes to the rectum, where water is absorbed from the undigested food. Then the undigested matter is egested out through the anus in the form of worm castings.