Final answer:
- Scientists have estimated that there are around 8.7 million species of plants and animals in existence. The answer is b
- However, only around 2.8 million species have been identified and described so far, most of which are insects. The answer is c
Step-by-step explanation:
1) It's important to note that estimating the total number of species on Earth is challenging due to the vastness and diversity of ecosystems, as well as the many undiscovered or poorly studied species. However, scientists use various methods to estimate species diversity, such as extrapolating from known species and using statistical models.
The estimated number of species can vary depending on the study and the taxonomic groups considered. The estimate of 8.7 million species represents an approximation based on current scientific understanding. It is important to emphasize that this number is not definitive and may change as new species are discovered and our knowledge of biodiversity expands.
So, the answer is b. 8.7
2) Identifying and describing species is a complex and time-consuming process. Scientists rely on various methods, including morphological characteristics, genetic analysis, and ecological observations, to classify and name new species. However, due to the vastness and diversity of life on Earth, many species remain undiscovered or poorly studied.
Of the identified and described species, insects make up the largest proportion. Insects are incredibly diverse and play essential roles in ecosystems as pollinators, decomposers, and prey for other organisms. They have been the subject of extensive scientific research, resulting in a relatively high number of identified insect species compared to other groups.
So, the answer is c. 2.8