Which of the following animals does NOT have a backbone?
Spider
Understanding Animals with and Without Backbones
Animals are broadly classified into two main groups based on the presence or absence of a backbone (also called a vertebral column or spine):
- Vertebrates: Animals that have a backbone. This group includes fish, amphibians, reptiles, birds, and mammals.
- Invertebrates: Animals that do not have a backbone. This is a very diverse group, including insects, spiders, worms, molluscs, jellyfish, and many others.
Analyzing the Given Animal Options
Let's examine each animal provided in the options to determine if it has a backbone.
| Animal | Classification Group | Does it have a Backbone? | Reason |
|---|---|---|---|
| Frog | Amphibian | Yes | Amphibians are vertebrates. |
| Human | Mammal | Yes | Humans are mammals, which are vertebrates. |
| Spider | Arachnid (Arthropod) | No | Spiders are invertebrates. They have an exoskeleton but no internal backbone. |
| Pigeon | Bird | Yes | Birds are vertebrates. |
Determining the Animal Without a Backbone
Based on the analysis:
- A Frog is an amphibian and has a backbone.
- A Human is a mammal and has a backbone.
- A Spider is an arachnid (an arthropod) and does not have a backbone.
- A Pigeon is a bird and has a backbone.
Therefore, the animal that does NOT have a backbone among the given options is the Spider.
Revision Table: Backbone Presence
| Animal | Backbone (Vertebrate) | No Backbone (Invertebrate) |
|---|---|---|
| Frog | ✓ | |
| Human | ✓ | |
| Spider | ✓ | |
| Pigeon | ✓ |
Additional Information on Animal Classification
Understanding the difference between vertebrates and invertebrates is fundamental in zoology. This distinction is based on a major structural characteristic: the presence or absence of a vertebral column, which is part of the internal skeleton (endoskeleton).
- Vertebrates have a complex nervous system, a well-developed brain, and usually paired limbs. Their backbone provides support and protects the spinal cord.
- Invertebrates make up about 95% of all animal species on Earth. They are incredibly diverse and include many different phyla like Mollusca (snails, clams), Annelida (worms), Arthropoda (insects, spiders, crustaceans), Echinodermata (starfish, sea urchins), and many others. Their support structures vary widely; some have exoskeletons (like insects and spiders), some have hydrostatic skeletons (like worms), and some are soft-bodied.
This classification helps scientists study the evolutionary relationships and diversity of animal life.
Important Questions from Zoology
Lymph is a tissue fluid present in intercellular spaces. It resembles to
- Which one of the following belongs to 'Pisces'?
Which one of the following statements is NOT correct?
Which of the following kingdoms has/have only unicellular organisms?
Consider the following statements:
1. All Echinoderms are not marine
2. Sponges are exclusively marine
3. Insects are found in all kinds of habitats
4. Many primates are arboreal
Which of the statements given above is/are correct?
