All questions of Classification of Animal Kingdom for UPSC CSE Exam

The Process of Respiration
Respiration is a vital biochemical process in living organisms that converts food into energy. This process is essential for the survival of all aerobic organisms, including humans.
How Respiration Works
- Energy Production:
- Respiration primarily involves breaking down glucose and other organic molecules to release energy. This energy is stored in the form of adenosine triphosphate (ATP), which cells use to perform various functions.
- Stages of Respiration:
- Glycolysis:
- The first step occurs in the cytoplasm, where glucose is converted into pyruvate, yielding a small amount of ATP.
- Krebs Cycle:
- This occurs in the mitochondria, where pyruvate is further broken down, releasing carbon dioxide and transferring energy to carrier molecules.
- Electron Transport Chain:
- The final stage occurs in the inner mitochondrial membrane, where the energy from carrier molecules is used to produce a significant amount of ATP, with oxygen acting as the final electron acceptor.
Importance of Respiration
- Energy for Cellular Functions:
- The ATP generated serves as an energy currency for cellular activities, including muscle contraction, nerve impulse propagation, and biosynthesis of macromolecules.
- Maintaining Homeostasis:
- Respiration helps in maintaining the balance of oxygen and carbon dioxide in the body, crucial for sustaining life.
Conclusion
In summary, respiration is the process that transforms food into usable energy for living organisms, making it fundamental for survival and functionality. Thus, the correct answer to the question is option 'A' - Respiration.

Characteristics of Insects:
- Presence of a backbone:
- Insects do not have a backbone, they have an exoskeleton made of chitin.
- Backbone is a characteristic of vertebrates, not insects.
- Cold-bloodedness:
- Insects are cold-blooded animals, meaning their body temperature fluctuates with the environment.
- This is a common characteristic of insects but not a defining one.
- Three pairs of legs:
- One of the key characteristics of insects is that they have three pairs of legs.
- This distinguishes them from other arthropods like spiders, which have four pairs of legs.
- Presence of gills:
- Insects do not have gills; they breathe through a system of tubes called tracheae.
- Gills are typically found in aquatic organisms like fish and some arthropods.
Therefore, the correct characteristic of insects among the options given is three pairs of legs. This feature is a defining characteristic of insects and sets them apart from other groups of animals.

Reptilia
Reptiles are a class of animals that lay eggs and have scales or feathers. Here is why you would find these characteristics in the class Reptilia:

Egg-laying
- Reptiles are known for laying eggs, which is a key characteristic that distinguishes them from mammals.
- The eggs of reptiles have a leathery or hard shell to protect the developing embryo.

Scales or feathers
- Reptiles have scales, which are hardened plates made of keratin that cover their bodies. These scales provide protection and help prevent water loss.
- Some reptiles, such as birds, have feathers instead of scales. Feathers serve various functions, including insulation, flight, and display.

Examples of reptiles
- Some common examples of reptiles include snakes, lizards, turtles, crocodiles, and birds.
- Birds are considered a subgroup of reptiles, known as Aves, and they share many characteristics with other reptiles, such as laying eggs and having feathers.
In conclusion, animals that lay eggs and have scales or feathers can be found in the class Reptilia. This class encompasses a diverse group of animals that exhibit these unique characteristics.