All questions of Animal Kingdom for NEET Exam

Except for crocodilians, which have a four-chambered heart, all reptiles have a three-chambered heart consisting of two atria and one ventricle.

The members of the class - Chondrichthyes are marine animals with a streamlined body and have a cartilaginous endoskeleton.

A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouth parts used for feeding and sucking. In vertebrates, a proboscis is an elongated nose or snout.

Metamerism

 Class-Cyclostomata is comprised of, the living jawless fishes. Their mouth is circular and lack jaws, hence they are also called agnathans.  It is surrounded by tentacles (e.g., lampreys and hellish). These also presses retractable teeth.       

Tropical Tasar: Tasar (Tussah) is copperish colour, coarse silk mainly used for furnishings and interiors. It is less lustrous than mulberry silk, but has its own feel and appeal. Tasar silk is generated by the silkworm, Antheraea mylitta which mainly thrive on the food plants Asan and Arjun.

Explanation:
Air bladder is a gas-filled sac that helps fish to maintain buoyancy in water. However, not all fish have air bladders. The correct answer to the given question is option B, i.e., shark, as sharks do not have air bladders.

Reasons why sharks do not have an air bladder are:

1. Buoyancy control: Sharks have a special organ called the liver that is filled with oil. This oil is less dense than water and provides buoyancy to the shark, allowing it to stay afloat.

2. Depth control: Unlike bony fish that have a swim bladder to adjust their depth in water, sharks are able to control their depth by swimming. They can swim at different angles to adjust their depth in water.

3. Adaptation to environment: Sharks have evolved to live in their environment, and their body shape and buoyancy control mechanisms have adapted to suit their needs.

Therefore, it can be concluded that while some fish have air bladders to maintain buoyancy in water, sharks have evolved different mechanisms to control their buoyancy and depth in water.

Correct Statements:
- (i) True coelom is a body cavity which arises as a cavity in the embryonic mesoderm.
- (iii) The body cavity of arthropods and non-cephalopod molluscs is called haemocoel.

Explanation:
- Statement (i): True coelom is indeed a body cavity that develops from a cavity in the embryonic mesoderm. It is lined by mesoderm and provides space for organs to develop and move independently within the body.
- Statement (iii): Haemocoel is a body cavity found in arthropods and non-cephalopod molluscs. It is a spacious cavity that accommodates blood and surrounds the organs.

Incorrect Statements:
- (ii) Digestive cavity is found in acoelomates, pseudocoelomates as well as coelomates - This statement is incorrect as acoelomates lack a body cavity, pseudocoelomates have a pseudocoelom, and coelomates have a true coelom.
- (iv) Aschelminthes possess true body cavity - Aschelminthes are pseudocoelomates, not possessing a true coelom.
- (v) There is no cavity between the body wall and gut in Echinoderms - Echinoderms actually possess a water vascular system instead of a body cavity.
Therefore, the correct statements are (i) and (iii), making option (a) the correct choice.

Overview of Cyclostomata
Cyclostomata is a class of jawless fish characterized by their unique feeding mechanism and body structure. This class includes modern representatives such as lampreys and hagfish.
Feeding Mechanism
- Cyclostomes lack jaws but have a round, sucker-like mouth.
- They use their mouths to attach to hosts or substrates, facilitating their feeding process.
Ectoparasitic Nature
- Most living members of Cyclostomata are ectoparasites, meaning they live on the outside of their host organisms.
- Lampreys, for instance, attach to fish and feed on their blood and bodily fluids.
- This parasitic behavior allows them to obtain nutrients necessary for survival.
Ecological Role
- As ectoparasites, Cyclostomata play a significant role in their ecosystems.
- They are involved in regulating host populations and can impact the health of fish populations.
Conclusion
- The classification of Cyclostomata as ectoparasites is crucial to understanding their ecological importance and evolutionary adaptations.
- Their unique feeding strategy distinguishes them from other fish classes, highlighting their specialized niche in aquatic ecosystems.
In summary, the correct answer to the question is option 'B' due to the ectoparasitic lifestyle of living members of Cyclostomata.

Placoid Scales are characteristic of Chondrichthyes (cartilaginous fishes).
Ctenoid Scales are characteristic of Osteichthyes (bony fishes).
Ectoparasites are typically associated with Cyclostomata (e.g., lampreys).
Proboscis gland is a feature of Hemichordata (e.g., acorn worms).
Thus, the correct code is Option D: 1 2 4 3.

Understanding Cyclostomes
Cyclostomes, a group of jawless fish that includes lampreys and hagfish, exhibit unique characteristics that set them apart from other vertebrates. Let's analyze the statements provided about them.
Statement Analysis

• (a) They lack scales and paired fins.
  This statement is correct. Cyclostomes do not possess scales or paired fins, which distinguishes them from many other fish species.
• (b) They have circular mouth with jaws.
  This statement is incorrect. Cyclostomes have a circular mouth, but they lack true jaws. Instead, they have a sucker-like mouth, which is characteristic of their feeding mechanism.
• (c) They bear 6-15 pairs of gills.
  This statement is correct. Cyclostomes typically possess multiple pairs of gills for respiration.
• (d) They migrate to deep sea for spawning.
  This statement is incorrect for most cyclostomes. While some species may have specific spawning behaviors, many migrate to freshwater or nearshore environments rather than the deep sea.

Conclusion
Based on the analysis:
- Statements (b) and (d) are incorrect. Cyclostomes do not possess jaws and do not typically migrate to the deep sea for spawning.
- Therefore, the correct answer is option 'D', which identifies the incorrect statements as (b) and (d).
This understanding helps clarify the biological traits of cyclostomes, distinguishing them from other fish groups.

Metagenesis refers to the alternation of generations between asexual and sexual phases of an organism, commonly observed in cnidarians like jellyfish.

Option A: The presence of different morphic forms could refer to polymorphism, not specifically metagenesis.
Option C: This describes metamorphosis, not metagenesis.
Option D: This refers to characteristics unrelated to metagenesis.
Thus, the correct answer is Option B.

(a) Metagenesis is observed in Helminths: Incorrect. Metagenesis refers to the alternation of generations between asexual and sexual phases, observed in cnidarians, not in helminths.
(b) Echinoderms are triploblastic and coelomate animals: Correct. Echinoderms have three germ layers (triploblastic) and a true coelom.
(c) Round worms have organ-system level of body organization: Correct. Roundworms (nematodes) have an organ-system level of organization.
(d) Comb plates present in ctenophores help in digestion: Incorrect. Comb plates (ctenes) in ctenophores are used for locomotion, not digestion.
(e) Water vascular system is characteristic of Echinoderms: Correct. The water vascular system is a unique feature of echinoderms.
Thus, the correct answer is Option B.

Overview of Non-Chordates
Non-chordates are a diverse group of animals that lack key characteristics found in chordates. The statements provided can be evaluated based on the anatomical features of non-chordates.
Analysis of Each Statement
- A. Pharynx is perforated by gill slits.
This statement is typically true for chordates, especially in their larval stages (like in some tunicates and lancelets), but it is not a common feature of non-chordates.
- B. Notochord is absent.
This statement is correct. Non-chordates do not possess a notochord, which is a defining feature of chordates.
- C. Central nervous system is dorsal.
This statement is also correct for chordates. Non-chordates generally have a ventral nervous system or a nerve net in simpler forms.
- D. Heart is dorsal if present.
This statement is true for some chordates, but it does not apply to most non-chordates, as their circulatory systems vary widely.
- E. Post-anal tail is absent.
This statement is true for non-chordates. Many non-chordates do not have a post-anal tail, which is a characteristic feature of chordates.
Correct Answer Explanation
The correct answer is option C (B, D & E only) because:
- B (Notochord absent) and E (Post-anal tail absent) are true statements about non-chordates.
- D (Heart is dorsal if present) is misleading as it does not apply uniformly to non-chordates.
Thus, while B and E are accurate, D can also be misleading in interpretation, which leads to some confusion.
In summary, option C highlights the absence of the notochord, presence of a diverse circulatory system, and absence of a post-anal tail in non-chordates.

Understanding the Assertion
The assertion states: "All vertebrates are chordates, but all chordates are not vertebrates."
- Vertebrates: These are animals that have a backbone or spinal column. This group includes mammals, birds, reptiles, amphibians, and fish.
- Chordates: This broader category includes all animals that possess a notochord at some stage of their development. This group encompasses not only vertebrates but also invertebrate chordates such as tunicates and lancelets.
Thus, the assertion is correct because while all vertebrates belong to the phylum Chordata, not all chordates develop into vertebrates.
Understanding the Reason
The reason given is: "Notochord is replaced by a vertebral column in the adult vertebrates."
- The notochord is a flexible rod-like structure that provides support in the embryonic stages of all chordates.
- In vertebrates, during development, the notochord is gradually replaced by the vertebral column (spine) in adults.
This reason accurately explains a key characteristic that differentiates vertebrates from other chordates.
Conclusion
- Since both the assertion and reason are true, and the reason provides a correct explanation for the assertion, the correct answer is option 'D':
Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.

Understanding Radial Symmetry
Radial symmetry is a body plan in which body parts are arranged around a central axis. This type of symmetry is most commonly found in organisms that are aquatic and often sessile or free-floating.
Phylum Analysis
- Ctenophora (Comb Jellies):
- Exhibit radial symmetry in adults.
- Hemichordata (Acorn Worms):
- Adults display bilateral symmetry, not radial.
- They possess a segmented body and a distinct head region.
- Coelenterata (Cnidaria):
- Have radial symmetry in their adult forms (e.g., jellyfish, corals).
- Echinodermata (Starfish, Sea Urchins):
- Exhibit radial symmetry, typically pentamerous (five-part) symmetry in adults.
Conclusion
The correct answer is B (Hemichordata) because, unlike the other phyla listed, hemichordates demonstrate a bilateral symmetry as adults. Understanding these symmetries helps in the classification and study of various organisms within their respective phyla.