Vertebrates

- Vertebrates are a group of animals that possess a backbone or spinal column. They are characterized by having an internal skeleton made up of bones or cartilage, which provides support and protection for their bodies.
- Vertebrates are one of the major groups of animals, and they include a wide range of species such as fish, amphibians, reptiles, birds, and mammals.

Options:
a) Earthworm: Earthworms are not vertebrates. They belong to the phylum Annelida and are classified as invertebrates. They do not have a backbone or a spinal column.

b) Ant: Ants are also not vertebrates. They belong to the phylum Arthropoda and are classified as invertebrates. Like earthworms, ants do not have a backbone or a spinal column.

c) Spider: Spiders, like ants and earthworms, are also invertebrates. They belong to the phylum Arthropoda and do not possess a backbone or spinal column.

Correct answer:
d) Dog: Dogs are vertebrates. They belong to the class Mammalia and possess a backbone or spinal column. Dogs are warm-blooded animals and have a complex skeletal system that includes a backbone made up of individual vertebrae.

Explanation:
- The correct answer is option 'D' - Dog. Dogs are vertebrates because they have a backbone or spinal column, which is a defining characteristic of vertebrates.
- Dogs are mammals, which means they give birth to live young and nurse them with milk. They have a well-developed skeletal system, including a backbone made up of individual vertebrae.
- The backbone or spinal column in dogs serves as an important structure that provides support for the body, protects the spinal cord, and allows for movement and flexibility.
- Vertebrates, such as dogs, have a more complex and specialized body plan compared to invertebrates. They exhibit a higher level of organization and complexity, with specialized organ systems and a greater range of behaviors and adaptations.
- In contrast, invertebrates, such as earthworms, ants, and spiders, lack a backbone or spinal column. They have simpler body plans and are often characterized by a segmented body, exoskeleton, or other unique features.