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BZYCT-131: Animal Diversity

BZYCT-131: Animal Diversity

IGNOU Solved Assignment Solution for 2023

If you are looking for BZYCT-131 IGNOU Solved Assignment solution for the subject Animal Diversity, you have come to the right place. BZYCT-131 solution on this page applies to 2023 session students studying in BSCG, BSCBCH courses of IGNOU.

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BZYCT-131 Solved Assignment Solution by Gyaniversity

Assignment Solution

Assignment Code: BZYCT-131/TMA/2023

Course Code: BZYCT-131

Assignment Name: Animal Diversity

Year: 2023

Verification Status: Verified by Professor


Note: Attempt all questions. The marks for each question are indicated against it.



Q1) Answer the following:


1a) What is the difference between dinoflagellates and apicomplexans? (2)

Ans) The difference between dinoflagellates and apicomplexans is as follows:

Q1b) List three unique features of Phylum Ciliophora. (3)

Ans) Ciliates, a broad category of single-celled eukaryotes, dwell on water and land. Cilia help them move, eat, and perceive their surroundings. Here are three things that make Phylum Ciliophora stand out:


Unique Genetic System: Ciliates have a diploid micronucleus and a polyploid macronucleus. Sexual reproduction and genetic maintenance are managed by the micronucleus. The macronucleus regulates gene expression and cell function. Two ciliates exchange micronuclei, which undergo meiosis and fusion to generate a zygote and a new individual during conjugation. Due to their genes, ciliates may quickly adapt and generate new features.


Complex Cell Structures: Ciliates have complex cells. They have contractile, food, trichocyst, and cytostomes. Food vacuoles digest food and take in nutrients, while contractile vacuoles regulate osmoregulation and remove excess water from the cell. Trichocysts release a stringy material, and cytostomes help ciliates catch and devour food.


Unique Cell Division: Binary fission divides ciliates. The micronucleus undergoes meiosis, and the macronucleus undergoes mitosis to produce four haploid nuclei. Two of these nuclei form a micronucleus, while the other two split. The cell separates into two daughter cells containing micronuclei and macronuclei after the macronucleus splits in half. This lets ciliates reproduce swiftly and maintain genetic diversity.


Q1c) Which of the following is not true for animals with radial symmetry? (1)

i) Non front and back ends

ii) Are always sessile

iii) No left or right sides

iv) Face the environment from all sides

Ans) Radial symmetrical animals are not always sessile.


Q1d) Match the following: (4)

Q2a) Complete the following sentences inserting appropriate words in blanks: (5)


i) Porifera are ………………. cellular animals’ incapable of ……………… as they remain to the substratum like a ………………….

Ans) Porifera are pore bearing multicellular animals that are incapable of making movement as they are attached to the substratum like a plant.


ii) The sponge body is covered by an outer epithelial layer made up of ………………….

Ans) Sponge body is covered by an epithelial layer made up of pinacoderm.


iii) Sponges with skeleton made up of spicules of calcium carbonate belong to the class ………………….

Ans) Sponges with a skeleton made up of spicules of calcium carbonate belong to the class Calcarea.


Q2b) Write true (T) or false (F) in the space provided against each statement.                      (5)


i) Cnidocyte has a hair like cnidocil which acts as a trigger.

Ans) True.


ii) Medusae are asexual zooids.

Ans) False.


iii) Obelia colony is bimorphic.

Ans) True.


iv) Obelia is a freshwater plant like animal found attached to substratum.

Ans) False.


v) Gonangium is a sexual way of reproduction.

Ans) False.


Q3) Please attempt the following questions: (1)

i) Which of the words given in the parenthesis is correct?

Flame cells in platyhelminths are ………………. in function. (excretory/osmoregulatory)

Ans) Excretory.


ii) Arrange the character most appropriate to the class of Platyhelminthes against it. (4)

Q3iii) What do you mean by true coelomates? Discuss their advantages. (5)

Ans) True coelomates are animals with a true coelom, which is a body cavity filled with fluid and lined by tissue that comes from the mesoderm. This tissue is called the peritoneum. The coelom separates the gut from the body wall and the organs inside the body. This gives the organs a space to move and grow without being affected by the body wall. This kind of body cavity can be found in annelids, arthropods, mollusks, and chordates, among other animal groups.


One of the best things about having a true coelom is that it gives the animal a skeleton made of water. The coelomic fluid, which is inside the coelom, can be pumped up to support the muscles and make movement more efficient. This is especially helpful for animals that have to move in complicated ways, like digging or crawling through tight spaces. Having a true coelom is also helpful because it makes it possible for specialised organs to form. The coelomic cavity gives organs a place to grow and work without being affected by other organs and body parts. This makes it possible for complex organ systems, like the respiratory and circulatory systems, to develop. These systems can then be optimised for their specific functions without being limited by other structures.


The true coelom also makes room for the digestive system to grow and work well. In animals without a coelom, like flatworms, the digestive system is just a simple sac with one opening. This makes it hard for the animal to digest and absorb food as well as it could. Animals with a true coelom, on the other hand, have a more complicated digestive system with specific areas for digestion and absorption. This lets them process food more efficiently. When there is a real coelom, different body systems can work together in more complex ways. For example, the circulatory system can get nutrients and oxygen to all parts of the body more quickly, and the respiratory system can exchange gases more quickly because the coelomic cavity has more surface area.


Lastly, a true coelom gives a plant or animal more flexibility and the ability to adapt to changes in its environment. Because the coelomic cavity acts as a buffer between the internal organs and the body wall, the size or shape of the body can change without affecting how the organs work.


Q4a) Choose the correct word from the alternative given: (3)


i) Trilobites are an extinct group of primitive/advanced arthropods.

Ans) Primitive arthropods.


ii) Spiders, ticks, mites and scorpions are included under the class Eurypterida/Arachnida.

Ans) Arachnida.


iii) Spinning organs or spinnerets are characteristic of Araneae/Acarina.

Ans) Araneae.


Q4b) Indicate whether the following statements are ‘True’ or ‘False’. (2)


i) There are six pairs of appendages in the head of crustaceans corresponding to six segments.

Ans) True.


ii) Malacostracans account for over 60% of all the crustaceans.

Ans) True.


Q4c) Write short notes on: (5)


i) Compound eye of insects

Ans) The compound eye is a remarkable sensory organ found in insects and many other arthropods, such as crustaceans and millipedes. The structure of the compound eye is composed of numerous tiny lenses, each of which functions as a separate optical unit that captures and processes light. The compound eye of insects is a fascinating example of evolution's ability to create highly specialized organs that are adapted to a particular environment and lifestyle.


The compound eye of insects consists of thousands of individual visual units called ommatidia, which are arranged in a hexagonal pattern on the surface of the eye. Each ommatidium contains a cornea, a lens, a crystalline cone, a light-sensitive cell called a photoreceptor, and a set of pigment cells. The cornea and lens work together to focus light onto the crystalline cone, which acts as a refractive lens to further focus the light onto the photoreceptor cell. The pigment cells surrounding the photoreceptor help to reduce stray light and improve the contrast of the image formed.


The compound eye's hexagonal arrangement of ommatidia provides insects with a wide field of view, allowing them to detect movement and objects in all directions. The arrangement also ensures that there is no overlap or blind spot between adjacent ommatidia. The number of ommatidia in the compound eye can vary between species, with some insects having as few as a few dozen ommatidia, while others have tens of thousands. For example, the dragonfly has about 30,000 ommatidia, while the butterfly has only about 4,000.


The compound eye's ability to detect light and colour varies depending on the type of photoreceptor cells present in the ommatidia. Insects have two types of photoreceptor cells: the long-wavelength-sensitive (L) cells, which are sensitive to red and green light, and the short-wavelength-sensitive (S) cells, which are sensitive to blue light. Some insects, such as bees and butterflies, have an additional type of photoreceptor cell that is sensitive to ultraviolet light, which helps them to navigate using the sun's position.


ii) Moulting in insects

Ans) Moulting, or ecdysis, is the process by which insects shed their old exoskeleton and replace it with a new one. Moulting is essential for the growth and development of insects, allowing them to increase in size and adapt to changing environmental conditions. The process of moulting is complex and involves several physiological and hormonal changes in the insect's body.


Insects have a hard, protective exoskeleton made of chitin and other proteins that provides support and protection to their body. However, this exoskeleton is not flexible and does not allow for growth, so insects must periodically moult to accommodate their increasing size. The frequency of moulting varies between species and can depend on factors such as temperature, food availability, and age.


The process of moulting typically begins with the insect's epidermal cells producing a new cuticle, or exoskeleton, underneath the old one. The old cuticle then separates from the epidermis, and the insect secretes a fluid between the old and new cuticle, which causes the old cuticle to split and separate from the body. The insect then wriggles and twists its body, using its legs to push and pull the old cuticle off. Once the old cuticle has been removed, the insect expands its body to allow the new cuticle to harden and become rigid.


Moulting is regulated by several hormones, including ecdysone, which stimulates the production of the new cuticle, and juvenile hormone, which regulates the insect's growth and development. The levels of these hormones fluctuate during the moulting process, triggering changes in the insect's body and behaviour.


For example, during the pre-moult phase, the insect may stop feeding and become inactive, while in the post-moult phase, it may exhibit increased activity and feeding behaviour. Moulting is a critical process in the life cycle of insects, as it allows them to grow and develop and adapt to changing environmental conditions. However, moulting also exposes insects to increased vulnerability and risk, as they are temporarily soft and vulnerable while their new exoskeleton hardens. In addition, moulting can be energetically costly and may require significant resources, such as food and water, to support the insect's growth and development.


Q5a) State whether the following statements are ‘True’ or ‘False’: (4)


i) Bivalves have adapted for filter feeding methods.

Ans) True.


ii) The blood of cephalopods contains hemocyanin.

Ans) True.


iii) Cephalopods have one of the best developed nervous systems among invertebrates.

Ans) True.


iv) Development in bivalves includes trochophore and veliger larvae.

Ans) True.


Q5b) Fill in the blanks with suitable words: (6)


i) ……………….. is the only living genus under the subclass Nautiloidea.

Ans) Nautilus is the only living genus under the subclass Nautiloidea.


ii) The mantle is innervated by ……………….. ganglia.

Ans) The mantle is innervated by paired ganglia.


 iii) The endoskeleton of most echinoderms is formed of ……………. .

Ans) The endoskeleton of most echinoderms is formed of calcareous ossicles or plates.


iv) In echinoderms the system of coelomic canals and tube feet is called ………………….., …………………… system.

Ans) In echinoderms, the system of coelomic canals and tube feet is called the water vascular system.


v) The larval stages of asteroids are ……………… and ………….. .

Ans) The larval stages of asteroids are bipinnaria and brachiolaria larvae.



Q6a) Correct the given statements. (4)


i) Presence of cranium and paired appendages is a characteristic feature of Agnatha.

Ans) Presence of cranium and paired appendages is a characteristic feature of the superclass Gnathostomata.


ii) In jawless fishes heart is a single chambered structure.

Ans) Given statement is correct.


iii) Development in hagfishes includes a larval stage called ammocoetes.

Ans) Given statement is correct.


iv) Special mucous glands are present in Petromyzon.

Ans) Given statement is correct.


Q6b) Why do marine teleosts need to drink enormous amounts of seawater? (3)

Ans) Marine teleosts, which are bony fish that live in saltwater, have to work hard to keep the right amount of water in their bodies because seawater has a lot of salt in it. To keep from getting too thirsty, these fish need to drink a lot of seawater to replace the water they lose through osmosis and other body processes.


When seawater gets into a marine teleost's body, the amount of salt is higher than the number of ions and fluids inside the fish's cells. This is effective in pressure that pulls water out of the cells and into the fluids around them. To stop this from happening, the fish has special cells in its gills that move salt ions out of its body and into the seawater around it.


This process, called "ion regulation," helps the fish's body keep the right amount of salt and water. But for ion regulation to work, the fish must drink a lot of seawater to make up for the water they lose through their gills. The fish's concentrated urine gets rid of the extra salt from the seawater. This helps keep the osmotic balance of the fish's body fluids.


Q6c) How do the freshwater teleosts overcome their osmoregulatory challenges? (3)

Ans) In freshwater, which is hypotonic for their body fluids, it can be hard for freshwater teleosts to keep the right balance of water and ions in their bodies. Freshwater teleosts have come up with several ways to deal with this problem.


First, freshwater teleosts don't drink much water and make a lot of watery urine to get rid of it. Freshwater teleosts have kidneys that are very good at making low-ion concentration urine. Also, the gills move ions like sodium, chloride, and bicarbonate from the water into the body. This helps keep the ion balance.


Second, freshwater teleosts actively take in ions from the water, like sodium, chloride, and calcium, through their gills and gut. Also, their gills have special cells called mitochondria-rich cells that move ions against a concentration gradient. Ions from the freshwater environment are actively taken in by these cells.


Lastly, some freshwater teleosts have developed special adaptations like a thick layer of mucus on their skin to reduce the amount of water they take in and specialised ion transporters in their digestive tracts to get the most out of the ions they take in.


Q7i) Describe parental care in Amphibians. (5)

Ans) There is a wide range of variation in the level of parental care provided by different species of amphibians. This can be attributed to factors such as the environment, the mating system, and the lifespan of the species. In general, frogs provide a lower level of parental care for their offspring as compared to many other species of animals, such as birds or mammals.


It is common for the female of an amphibian species to watch over the eggs. They show their concern for their young in a variety of ways, including this one. There are several species of toads, such as the common toad (Bufo bufo), in which the females deposit their eggs in bodies of water and then remain nearby to tend to them. They may also clean the eggs in order to prevent mould from growing on them and to protect the eggs from being consumed by other aquatic animals. It is possible for the female of some species, such as the poison dart frog, to lay her eggs on land and then transport the developing tadpoles to a body of water, typically on her back.


Male amphibians can also give parental care. For instance, in the species of toads known as midwife toads, the male wraps his back legs over the eggs and carries them on his back in order to shield them from any danger. Some male frogs will guard the eggs until they hatch, at which point they will transport the tadpoles to nearby water sources on their backs and continue the cycle.  Even after the eggs have been laid, certain species of amphibians may continue to care for their offspring. For instance, in certain species of salamander, the female will construct a nest in which she will lay her eggs. After the eggs hatch, the female will guard the young and feed them. It is possible that the parents of certain species of poison dart frog will feed their developing tadpoles unfertilized eggs until the tadpoles mature into frogs.


Q7ii) Distinguish between anurans and urodeles. (5)

Ans) The difference between anurans and urodeles is as follows:

Q8a) Describe the distinguishing features of turtles of Order Testudines. (4)

Ans) Turtles, which belong to the Order Testudines, have a unique body plan that includes a shell made of bone with an upper shell and a lower shell, a mouth that looks like a beak, and four legs.


Some of the things that make turtles unique are:

  1. Bony Shell: One thing that makes turtles stand out is their hard shell. The carapace and plastron are made up of keratin-covered bone plates called scutes that make up the carapace and plastron.

  2. Beak-like Mouth: Their mouths look like beaks and do not have any teeth. Their jaws are designed to crush and grind food, and their tongues help them move it around.

  3. Four Legs: Turtles have five claws on each of their four legs. The legs are made so that the animal can walk, swim, and dig.

  4. Unique Respiratory System: Turtles have a unique way of breathing that includes lungs and special glands in their cloaca that allow them to get oxygen from water.

  5. Temperature-dependent Sex Determination: The temperature at which turtle eggs are incubated rather than their genes determine the sex of many turtle species.

  6. Long Lifespan: Turtles are known for being very long-lived; some species can live for more than 100 years.

  7. Omnivorous Diet: Turtles are omnivores, which means they eat both plants and animals. They eat things like insects, fish, and plants.


Q8b) How are tuataras different from lizards? (2)

Ans) Tuataras are lizards that live in New Zealand. They are in the order Rhynchocephalia. In several ways, they are different from lizards:

  1.  Third Eye: The parietal eye is the "third eye" that tuataras have on the top of their heads. This eye responds to changes in light and helps keep their circadian rhythms in check.

  2. Teeth: Tuataras have two rows of teeth on their upper jaw and one row on their lower jaw. No other living reptile has this arrangement.

  3. Skull Structure: The tuatara has a different kind of head than lizards do. The tuatara's skull has a lot of movement, which lets its jaws open wider and with more force.

  4. Nocturnal: Most lizards are active during the day, but tuataras are mostly active at night.

  5. Scales: Tuataras have thick, spiny scales on their backs that stick out more than lizard scales.

  6. Reproduction: Tuataras have a unique reproductive system. Males only have one reproductive organ, called the "cloaca," which is used both for mating and getting rid of waste. The females dig nests in the ground where they lay their eggs, which take about a year to hatch.


Q8c) Describe two anatomical features of lizards (including legless members) that distinguish them from snakes. (8)

Ans) Lizards and snakes are both in the order Squamata, and they have a lot in common, like long bodies, jaws that can move, and the ability to shed their skin. But lizards and snakes are not the same because they have different bodies. For example, lizards have legs and snakes do not.


Presence of Legs: Lizards can walk or run with their four legs, which each have five toes. Even lizards with no legs, like the slowworm, have small, useless limbs. Snakes, on the other hand, have lost their limbs over time, and their bodies have become long and cylindrical so that they can move through tight spaces more easily.


External Ear Openings: The fact that lizards have external ear openings, called tympana, is another thing that sets them apart from snakes. The tympana are right behind the eyes and look like small holes or slits in the skin. Through these holes, lizards can hear sounds like other lizards calling out or predators coming close. Snakes, on the other hand, don't have external ears, so they can't hear sounds in the air. Instead, they use vibrations that they pick up through their lower jaw and send to their inner ear.


Moveable Eyelids: Lizards and snakes are also different because lizards have eyelids that can move. Lizards' upper and lower eyelids can open and close on their own. This lets them blink and keep dirt out of their eyes. Snakes, on the other hand, don't have eyelids that can move. Instead, they have a single clear scale called a spectacle that covers and protects their eyes.


Different Skull Structure: The way lizards and snakes' heads are built is also different. Lizards have a clear temporal arch that separates the eye socket from the ear opening. Snakes, on the other hand, don't have this arch and have longer heads. Some lizards, like chameleons, have a tongue that sticks out and can be used to catch prey. Snakes, on the other hand, have a forked tongue that they use to smell things around them.


Q8d) How do crocodiles and alligators differ from each other? (2)

Ans) Crocodiles and alligators belong to Crocodylia. Despite their similarities, they have some differences.

  1. Snout Shape: Crocodiles and alligators differ primarily in nose shape. Crocodiles have longer, V-shaped snouts, while alligators have shorter, wider, U-shaped ones. Their snouts differ due to their diets. Crocodiles' longer snouts help them catch and hold larger prey. Alligators can crush and retain smaller animals due to their bigger mouths.

  2. Habitat: Crocodiles and alligators differ in their habitats. Crocodiles inhabit estuaries, deltas, and lagoons. Alligators prefer rivers, lakes, and marshes.

  3. Tooth Arrangement: Crocodiles' teeth are set up in a more aggressive way than alligators. They have a fourth mandibular tooth on the lower jaw that can be seen when the mouth is closed and fits into a notch in the upper jaw. Alligators don't live in this way.

  4. Temperature Sensitivity: Alligator eggs hatch at 33°C, but crocodile eggs can hatch at a range of temperatures. Crocodiles can endure large temperature variations due to their surroundings.

  5. Size: Crocodiles usually outsize alligators. The largest crocodile, the saltwater, may grow to 7 metres and weigh 1,000 kg. The American alligator is the largest and may reach 4.5 metres and 500 kg.


Q9i) Where was the Archaeopteryx discovered? Give reasons for the Archaeopteryx being considered the connecting link between reptiles and birds. (5)

Ans) The Archaeopteryx is a famous extinct dinosaur that looked like a bird. It was found in Germany in 1861 in the Solnhofen Limestone Formation. It lived about 150 million years ago, during the Late Jurassic time. The discovery of the Archaeopteryx was important in the history of evolution because it showed for the first time that reptiles and birds had evolved from each other.


The Archaeopteryx is a transitional fossil, or "missing link," between dinosaurs and birds because it has traits of both reptiles and birds.


Some of the things that make it an animal between reptiles and birds are:

  1. Feathers: The feathers on the Archaeopteryx are the most important thing that links it to birds. Archaeopteryx's feathers were not like those of modern birds. Instead, they were more like the downy feathers of baby birds. The feathers may have started out to keep warm or help the bird fly.

  2. Skull: The Archaeopteryx's head looked a lot like a reptile's, with sharp teeth in its jaw and a long, bony tail. But the skull also had some bird characteristics, like a light beak.

  3. Wings: Archaeopteryx's wings had the same basic bone structure and flight feathers as those of modern birds. But compared to the size of the body, the wings were much smaller than those of birds today.

  4. Claws: The Archaeopteryx had sharp claws on its wings, which is a trait of reptiles. However, its big toe (hallux) could move back and forth, just like a modern bird's.


The discovery of the Archaeopteryx showed that species change over time through the process of natural selection. The Archaeopteryx was a key piece of evidence that birds came from small theropod dinosaurs, which were reptiles. Also, the Archaeopteryx is important because it shows that feathers were already around before birds learned to fly. The feathers may have started out to keep warm or show off, but eventually they were used to fly. The fact that the Archaeopteryx had feathers also shows that feathers evolved for reasons other than flight, since not all animals with feathers can fly.


Q9ii) Explain the role of drag and thrust in bird flight. (5)

Ans) Birds are adapted for flight and have developed specialised anatomical and physiological features to achieve efficient flight. Drag and thrust are the two main forces that affect how birds fly.

Drag is the force that works against the bird's movement through the air. Drag is caused by air resistance as the bird moves through the air.


The shape and structure of a bird's body and wings are made to reduce drag, which makes it easier for the bird to fly. Birds can do this because their bodies are streamlined, their heads are small, and their feathers lay flat against their bodies when they fly. Additionally, birds have wings that are shaped like air foils, which generate lift and reduce the amount of drag.


Thrust, on the other hand, is the force that propels the bird forward through the air. Thrust is generated by the bird's wings as they move through the air. The wings of a bird are made to both lift and push the bird forward. The wings are curved on the top and flat on the bottom, which creates an area of low pressure above the wing and an area of high pressure below it. This difference in pressure gives the bird lift, which lets it fly. In addition, the wings are angled slightly forward, which causes air to flow over the wings and generate forward thrust.


Birds also use other techniques to maximise their efficiency in flight. Birds, for example, can use updrafts and thermals to get higher without having to work hard. They could also use a tailwind to go faster and use less energy.

Some birds, like hawks and eagles, can stay in the air for long periods of time without flapping their wings. This is called soaring. Drag and thrust are two important forces that help birds fly. Birds' bodies are streamlined, their wings are shaped like air foils, and they have learned how to use updrafts and tailwinds to help them fly more efficiently. By understanding how these forces and adaptations work, we can gain a better understanding of how amazing it is that birds can fly.


Q10a) State whether the following statements are True (T) or False (F). (5)


i)Elephants are the largest land animals.

Ans) True.


ii)Blubber is found in monkeys.

Ans) False.


iii)Carnivores are grass eating mammals.

Ans) False.


iv)Kangaroos are egg laying mammals.

Ans) False.


v)Monotremes are viviparous.

Ans) False.


Q10b) Differentiate between Artiodactyla and Perissodactyla. (2)

Ans) The difference between Artiodactyla and Perissodactyla is as follows:

Q10c) Give one distinguishing morphological feature of each of the following orders: (3)


i) Cingulata

Ans) Presence of bony dermal plates or scutes embedded in the skin that forms a protective shell-like covering on the body.


ii) Sirenia

Ans) Flippers that look like paddles instead of arms, a flattened tail, and no back legs. Also, the upper lip and snout are long and make the upper lip prehensile, which is used to grab food.


iii) Primate

Ans) There are opposable thumbs, nails instead of claws on the fingers and toes, and eyes that look forward and can see in 3D.

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