Which of these are the three main types of scientific models?
The variety of life is called [blank_start]biodiversity[blank_end]. Ecologists are only just [blank_start]learning[blank_end] how important biodiversity is for the [blank_start]health[blank_end] of an [blank_start]ecosystem[blank_end] and our planet. A type of plant or animal is said to be extinct when [blank_start]all[blank_end] living members of that species have [blank_start]died[blank_end]. Endangered species are those that are [blank_start]threatened[blank_end] with extinction, or likely to become extinct.