Consider the following vertebrates :-
Fishes, Birds, Mammals, reptiles and Amphibians
Which of the following option correctly represent the decreasing order in relation to number of species?

Options

A. Amphibians `lt` Mammals `lt` Reptiles `lt` Fishes `lt` Birds
B. Mammals `lt` Amphibians `lt` Reptiles `lt` Birds `lt` Fishes
C. Mammals `lt` Amphibians `lt` Birds `lt` Reptiles `lt` Fishes
D. Amphibians` lt` Mammals` lt` Birds `lt` Fishes `lt` Reptiles

Answer

To determine the decreasing order of vertebrates based on the number of species, we need to analyze the approximate number of species for each group mentioned in the question:

1. **Fishes**: Approximately 34,000 species
2. **Birds**: Approximately 10,000 to 18,000 species (we will take the higher estimate of 18,000 for this analysis)
3. **Mammals**: Approximately 5,400 species
4. **Reptiles**: Approximately 11,341 species
5. **Amphibians**: Approximately 2,226 species

Now, let's arrange these groups in decreasing order based on the number of species:

1. **Fishes**: 34,000 species
2. **Birds**: 18,000 species
3. **Reptiles**: 11,341 species
4. **Mammals**: 5,400 species
5. **Amphibians**: 2,226 species

Thus, the correct decreasing order in relation to the number of species is:

**Fishes > Birds > Reptiles > Mammals > Amphibians**

### Final Answer:
**Fishes > Birds > Reptiles > Mammals > Amphibians**

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