Final answer:
The complete predicate in the sentence is "exist in the world." While the sentence refers to 3000 varieties of amphibians, there are actually about 6,200 known species, classified into frogs and toads, salamanders and newts, and caecilians.
Step-by-step explanation:
Underlining the complete predicate of a sentence involves identifying the part of the sentence that tells us what the subject does, is, or has. Looking at the sentence "About 3000 varieties of amphibians exist in the world," the complete predicate would be "exist in the world." This is because it contains the main verb "exist" and the phrase "in the world" which together tell us what about 3000 varieties of amphibians do. In terms of understanding amphibians in biology, it is noteworthy that while the sentence mentions 3000 varieties, there are actually about 6,200 known species of living amphibians. These species are divided into three major groups: frogs and toads, salamanders and newts, and caecilians. It's important to realize that frogs are especially diverse, with almost 5,000 species of frogs worldwide. Amphibians are found across the globe, with a higher biodiversity at lower latitudes, and play crucial roles both as predators and prey within various ecosystems.z