All questions of Animal Kingdom for NEET Exam

Germinal Layers in Embryonic Development and Diploblastic/Triploblastic Classification

Embryonic development is a complex process that involves the formation of various tissues and organs from a single cell. During this process, the embryo undergoes several stages of development that are marked by the formation of germinal layers. Germinal layers are the layers of cells that differentiate into specific tissues and organs during embryonic development. These layers form the basis of the body plan of an organism and are classified as either diploblastic or triploblastic.

Diploblastic Organisms

Diploblastic organisms are those that have only two germinal layers: the ectoderm and endoderm. These layers are formed during gastrulation, which is the process by which the embryo folds in on itself to form a hollow ball of cells called the gastrula. In diploblastic organisms, the ectoderm gives rise to the outer layer of the body and the nervous system, while the endoderm gives rise to the inner layer of the body.

Examples of diploblastic organisms include cnidarians (e.g. jellyfish, corals, sea anemones) and ctenophores (comb jellies).

Triploblastic Organisms

Triploblastic organisms are those that have three germinal layers: the ectoderm, mesoderm, and endoderm. These layers are formed during gastrulation, but unlike in diploblastic organisms, the mesoderm layer is also formed. The mesoderm gives rise to the muscles, circulatory system, and other internal organs.

Examples of triploblastic organisms include most animals, including humans.

Conclusion

The diploblastic/triploblastic classification is based on the number of germinal layers that are present during embryonic development. Diploblastic organisms have two germinal layers (ectoderm and endoderm), while triploblastic organisms have three germinal layers (ectoderm, mesoderm, and endoderm). This classification is important for understanding the basic body plan of organisms and how different tissues and organs are formed during embryonic development.

Bilateral Symmetry

Bilateral symmetry refers to the arrangement of body parts in such a way that an organism can be divided into two equal halves by a single plane passing through the central axis of the body. This type of symmetry is found in many animals, especially invertebrates and some vertebrates.

Incorrect statement

The incorrect statement is option C, which states that bilateral symmetry is found in all invertebrates and few vertebrates. This statement is incorrect because bilateral symmetry is actually found in the majority of animals, both invertebrates, and vertebrates. Almost all animals belonging to the phyla Chordata, Arthropoda, Mollusca, and Annelida exhibit bilateral symmetry.

Examples of animals with bilateral symmetry

- Invertebrates like insects, crustaceans, spiders, and worms exhibit bilateral symmetry.
- Vertebrates like fish, amphibians, reptiles, birds, and mammals exhibit bilateral symmetry.

Advantages of bilateral symmetry

Bilateral symmetry provides several advantages to animals:

- It allows for more efficient movement and coordination since paired limbs and muscles can work together to produce more precise movements.
- It facilitates the development of specialized organs and structures, such as eyes and ears, that are paired and located on opposite sides of the body.
- It enables animals to have directional movement, since paired limbs can be used to move forward or backward, up or down, and left or right.

Conclusion

Bilateral symmetry is a common type of symmetry found in the majority of animals, both invertebrates, and vertebrates. It allows for more efficient movement and coordination, facilitates the development of specialized organs and structures, and enables directional movement.

• Animals that belong to the phylum Platyhelminthes to Chordata are all triploblastic.
• But Platyhelminthes and aschelminthes belong to pseudocoelomates.
• Annelids, arthropods, echinoderms and chordates are under eucoelomates. This means not all triploblastic animals are eucoelomates. 
• Pseudocoelomates have false coelom while eucoelomate animals only have the true coelom. 

Correct Matching Explained
The correct answer is option 'C', as it accurately matches the animals with their corresponding symmetry, organization, and coelom type.
Animal Categories and Their Characteristics
- Ctenophores
- Symmetry: Radial
- Organisation: Diploblastic
- Coelom Type: Coelomates (not Pseudocoelomates)
- Echinoderms
- Symmetry: Bilateral (larval stage) and Radial (adult stage)
- Organisation: Triploblastic
- Coelom Type: Coelomates
- Platyhelminthes
- Symmetry: Bilateral
- Organisation: Triploblastic
- Coelom Type: Acoelomates
- Annelids
- Symmetry: Bilateral
- Organisation: Triploblastic
- Coelom Type: Coelomates (not Diploblastic)
Detailed Breakdown of Option 'C'
- Platyhelminthes
- These organisms, commonly known as flatworms, exhibit bilateral symmetry which allows for more complex movement and organization.
- They are triploblastic, meaning they have three germ layers: ectoderm, mesoderm, and endoderm.
- Importantly, they are classified as acoelomates, lacking a true coelom, which differentiates them from other triploblastic groups.
Conclusion
The other options provided contain inaccuracies regarding the animals' symmetry, organization, or coelom type. Thus, option 'C' is indeed the correct choice, effectively aligning Platyhelminthes with bilateral symmetry, triploblastic organization, and acoelomate structure.

Matching Body Feature and Animal Possessing It

Body features are specific characteristics that distinguish one animal from another. Here, we are identifying the correct matching pair of body features and the animal possessing it.

Ventral Central Nervous System - Leech

- The ventral central nervous system is a characteristic feature of the leech.
- The leech belongs to the phylum Annelida, which is characterized by segmented bodies.
- The nervous system of the leech is ventral, which means that it is located on the underside of the body.
- The ventral nerve cord of the leech runs the length of the body and is composed of ganglia (clusters of nerve cells) connected by nerves.
- The ventral central nervous system of the leech is responsible for coordinating movement and other bodily functions.

Pharyngeal Gill Slits Absent in Embryo - Chameleon

- The chameleon belongs to the class Reptilia, which is characterized by the absence of pharyngeal gill slits in the embryo.
- Pharyngeal gill slits are a characteristic feature of chordates, which includes vertebrates.
- In the embryo of chordates, pharyngeal gill slits develop into structures such as gills, jaws, and ears.
- However, in reptiles such as chameleons, these structures do not develop from pharyngeal gill slits.

Ventral Heart - Scorpion

- The ventral heart is a characteristic feature of the scorpion.
- The scorpion belongs to the class Arachnida, which is characterized by the presence of a ventral heart.
- The ventral heart of the scorpion is located on the underside of the body, between the cephalothorax and the abdomen.
- The ventral heart of the scorpion is made up of a series of muscular chambers that pump blood throughout the body.

Post-Anal Tail - Octopus

- The post-anal tail is a characteristic feature of some animals, such as fish and amphibians, but not of octopuses.
- Octopuses belong to the class Cephalopoda, which is characterized by the absence of a post-anal tail.
- Octopuses are marine animals with eight arms and no tail.
- The lack of a post-anal tail in octopuses is related to their mode of movement, which involves jet propulsion through water using a muscular mantle cavity.

Therefore, the correct matching pair of body feature and animal possessing it is:

a) Ventral central nervous system - Leech.

Common Features of Parrot, Platypus, and Kangaroo

Homoiothermy
- All three animals are homoiothermic or warm-blooded.
- They are able to maintain a constant body temperature regardless of the external temperature.
- This allows them to live in a variety of environments and adapt to changing conditions.

Differences among Parrot, Platypus, and Kangaroo

Toothless Jaws
- Parrots have a toothless beak that is adapted for cracking seeds and nuts.
- Platypuses have a toothless bill that is used to detect prey in the water.
- Kangaroos have teeth that are adapted for grazing on grass and plants.

Functional Postanal Tail
- Platypuses have a flat, broad tail that is used for swimming.
- Kangaroos have a long, muscular tail that helps them balance and jump.
- Parrots do not have a postanal tail.

Oviparity
- Platypuses are oviparous, which means they lay eggs.
- Kangaroos are marsupials and give birth to relatively undeveloped young that continue to develop in the mother's pouch.
- Parrots lay eggs and incubate them until they hatch.

In conclusion, although parrots, platypuses, and kangaroos share the common feature of homoiothermy, they differ in terms of their toothless jaws, functional postanal tail, and method of reproduction.

The correct answer is option 'C': Spongilla has special collared cells called choanocytes, not found in the remaining three.

Explanation:
- Spongilla is a genus of freshwater sponge, while leech, dolphin, and penguin belong to different animal groups.
- The statement mentions that Spongilla has special collared cells called choanocytes, which are not found in the remaining three organisms.
- Choanocytes: Choanocytes are specialized cells found in sponges. They have a collar-like structure with a flagellum projecting from the center. These cells help in creating water currents and capturing food particles.
- Spongilla, being a freshwater sponge, relies on choanocytes for filter-feeding.
- In contrast, leeches are segmented worms, dolphins are marine mammals, and penguins are flightless birds. These organisms do not possess choanocytes.
- The other statements in the options are incorrect:
- Option 'A': Penguins are not homeothermic; they are actually endothermic, meaning they can generate and regulate their own body heat. The remaining three organisms (Spongilla, leech, and dolphin) are poikilothermic, meaning their body temperature is dependent on external factors.
- Option 'B': Leeches can be found in both freshwater and marine environments. Dolphins are marine mammals, penguins inhabit marine and terrestrial habitats, while Spongilla is a freshwater sponge.
- Option 'D': Although all the mentioned organisms are bilaterally symmetrical, this statement is not specific to only these four organisms and can be true for many other animals as well.

In summary, the correct statement is that Spongilla has special collared cells called choanocytes, which are not found in leech, dolphin, and penguin.

Answer:

Similarity between animal pairs based on features:

a) Pteropus and Ornithorhyncus - viviparity
Both Pteropus (fruit bats) and Ornithorhyncus (platypus) are mammals that exhibit viviparity, which means giving birth to live young ones instead of laying eggs.

b) Garden lizard and crocodile - three chambered heart
Both Garden lizard and crocodile have a three-chambered heart, which consists of two atria and one ventricle. This type of heart is less efficient than a four-chambered heart found in mammals and birds, as it causes mixing of oxygenated and deoxygenated blood.

c) Ascaris and Ancylostoma - metameric segmentation
Both Ascaris (roundworm) and Ancylostoma (hookworm) exhibit metameric segmentation, which means their body is divided into repeating segments that have similar structures and functions.

d) Sea horse and flying fish - cold-blooded (poikilothermal)
Both Sea horse and flying fish are cold-blooded (poikilothermal) animals, which means their body temperature fluctuates with the surrounding environment. They cannot regulate their body temperature internally like warm-blooded (homeothermic) animals such as mammals and birds.

Conclusion:
In summary, the pairs of animals that are similar to each other for the feature stated against them are Pteropus and Ornithorhyncus for viviparity, Garden lizard and crocodile for a three-chambered heart, Ascaris and Ancylostoma for metameric segmentation, and Sea horse and flying fish for being cold-blooded (poikilothermal).

Possible Answer:

Understanding the Matching Pair:
In this question, we are given a set of animal and phenomenon pairs and we need to identify the correct matching pair. Let's analyze each option to determine the correct answer.

Option A: Pheretime - Sexual Dimorphism
Sexual dimorphism refers to the physical differences between males and females of the same species. However, "Pheretime" is not a recognized animal name or term related to sexual dimorphism. Therefore, option A is incorrect.

Option B: Musca - Complete Metamorphosis
Complete metamorphosis is a biological process where an animal undergoes distinct stages of development, including egg, larva, pupa, and adult. "Musca" is the scientific name for the common housefly, which is a well-known example of an animal that exhibits complete metamorphosis. Therefore, option B is the correct matching pair.

Option C: Chameleon - Mimicry
Mimicry is a phenomenon where an animal imitates the appearance or behavior of another organism to gain some advantage, such as protection from predators. While chameleons are known for their remarkable ability to change color, this is not an example of mimicry. Therefore, option C is incorrect.

Option D: Taenia - Polymorphism
Polymorphism refers to the occurrence of multiple forms or variations within a single species. Taenia is a genus of parasitic flatworms, commonly known as tapeworms. While some tapeworms might exhibit variations in their morphology, they are not typically considered polymorphic. Therefore, option D is incorrect.

Conclusion:
After analyzing all the options, we can conclude that the correct matching pair of an animal and a phenomenon it exhibits is option B: Musca - Complete Metamorphosis. The common housefly (Musca) undergoes complete metamorphosis during its life cycle, which includes the stages of egg, larva (maggot), pupa, and adult.

Incorrect Statement Explanation:

Explanation of Option C:
- Pseudocoel (false coelom) is not derived from the blastocoel of the embryo.
- It is actually derived from the blastocoel of the embryo in some animals.
- The pseudocoel is a fluid-filled body cavity that is not completely lined by mesoderm.
- It is found in organisms like roundworms (nematodes) and rotifers.
- The true coelom, on the other hand, is derived from mesoderm and is completely lined by mesoderm.
Therefore, option C is the incorrect statement as it misrepresents the origin and structure of the pseudocoel in certain organisms.

Not Characteristics of Osteichthyes

(i) Body is streamlined and mouth is terminal:
This characteristic is actually a defining feature of Osteichthyes. They are bony fish that have a streamlined body shape and terminal mouth position.

(ii) Gills are covered by operculum:
This is another defining feature of Osteichthyes. They have a bony plate, called an operculum, that covers and protects the gills.

Characteristics of Osteichthyes

(iii) Skin covered with cycloid and placoid scales:
Osteichthyes do have scales covering their skin, but they are not both cycloid and placoid. Cycloid scales are found in some fish, but not Osteichthyes. Instead, Osteichthyes have ganoid or ctenoid scales.

(iv) Many of them are viviparous:
Osteichthyes are mostly oviparous, which means they lay eggs that hatch outside of the mother's body. There are some viviparous species within Osteichthyes, but this is not a characteristic of the entire class.

Conclusion:
Therefore, the correct answer is option (c) (i), (iii), and (iv), as these characteristics are not accurate descriptions of Osteichthyes.

Answer:

The correct answer is option 'C': All vertebrates are chordates, but not all chordates are vertebrates.

Explanation:

To understand why option 'C' is the correct answer, let's break down the definitions of chordates and vertebrates and examine their relationship.

Chordates:
- Chordates are a phylum of animals that belong to the animal kingdom.
- They are characterized by certain key features, including a notochord (a flexible rod-like structure) at some point during their development.
- The notochord is usually present in the early embryonic stages and may or may not persist into adulthood.
- Chordates also possess other characteristics like a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.

Vertebrates:
- Vertebrates are a subphylum of chordates that have a backbone or vertebral column.
- They possess a notochord during their embryonic stage, but this notochord is subsequently replaced by the development of bones or cartilage forming the vertebral column.
- The vertebral column provides support and protection to the spinal cord in vertebrates.
- Vertebrates include animals like fish, amphibians, reptiles, birds, and mammals.

Relationship between Chordates and Vertebrates:
- All vertebrates are chordates because they possess the defining characteristics of chordates, including the presence of a notochord during their embryonic stage.
- However, not all chordates are vertebrates. Some chordates, like tunicates and lancelets, possess a notochord throughout their entire life but do not develop a vertebral column.
- These non-vertebrate chordates retain the notochord as their primary supportive structure.

Therefore, option 'C' makes sense because it correctly states that all vertebrates are chordates, but not all chordates are vertebrates.

Understanding the Statements
To analyze the statements regarding Cephalochordata and Urochordata, we need to clarify the characteristics of these two groups of organisms.
Cephalochordata Characteristics
- Cephalochordates, such as lancelets, possess a notochord that extends the entire length of their body throughout their life.
- This notochord provides structural support and is characteristic of the phylum Chordata.
Urochordata Characteristics
- Urochordates, commonly known as tunicates, have a notochord only during their larval stage.
- In the adult stage, most Urochordates do not have a vertebral column; instead, they lose the notochord and are primarily composed of a tunic.
Analysis of the Statements
- Statement 1: "Cephalochordata bears notochord all along the body throughout life."
- This statement is correct as Cephalochordates retain their notochord from larval stages into adulthood.
- Statement 2: "Urochordate bears vertebral column only in tail region throughout the life."
- This statement is incorrect. Urochordates do not possess a vertebral column in their adult form; they lose the notochord and develop a tunic.
Conclusion
- Given that Statement 1 is correct and Statement 2 is incorrect, the correct answer is option B.
By understanding the characteristics of these two groups, we can see why the statements hold their truth values as described.

Introduction:
Vertebrates are a group of animals that possess a vertebral column or backbone. They include fish, amphibians, reptiles, birds, and mammals. These animals share certain characteristics that distinguish them from other groups of animals.

Main Body:

Characteristic of vertebrates without exception:

The correct answer to the given question is option 'D', which states that the common characteristic of all vertebrates without exception is the presence of a well-developed skull.

1. Presence of a well-developed skull:
- All vertebrates possess a well-developed skull, which is a bony structure that encloses and protects the brain.
- The skull is made up of several bones and provides a rigid framework for the protection of the brain and sensory organs such as the eyes, ears, and nasal passages.
- The skull also plays a crucial role in the attachment of muscles responsible for chewing, biting, and other movements of the head.

2. Importance of a well-developed skull:
- The presence of a well-developed skull is essential for vertebrates as it protects the delicate brain from injury.
- The skull also provides support and protection to the sensory organs, which are vital for survival and adaptation to the environment.
- Additionally, the attachment points for muscles on the skull allow for the complex movements of the head and jaw, enabling various functions such as feeding, communication, and defense.

3. Differences in skull structure:
- While all vertebrates possess a well-developed skull, there are variations in its structure among different groups.
- Fish have a relatively simple skull, consisting of several bony plates and a cartilaginous framework.
- Amphibians and reptiles have more complex skulls, with additional bones and structures to accommodate their specific adaptations.
- Birds have a highly specialized skull, designed for lightweight and efficient flight.
- Mammals have the most diverse and complex skulls, reflecting their wide range of adaptations and lifestyles.

Conclusion:
The presence of a well-developed skull is a common characteristic of all vertebrates without exception. This structure protects the brain, supports sensory organs, and allows for various head and jaw movements. While the overall structure of the skull may vary among different groups of vertebrates, its importance in providing protection and facilitating essential functions remains constant.