* New discoveries: Scientists are constantly discovering new species, especially in remote or unexplored areas.
* Defining a "kind": "Kind" is a subjective term. It can be interpreted in different ways, such as species, genus, family, or even broader categories.
* Difficult to count: Many species are small, difficult to find, or live in environments that are hard to access.
However, we do have some estimates:
* Species: Scientists estimate that there are between 8.7 million and 1 trillion species on Earth, with only about 1.5 million formally described.
* Animals: Estimates for animal species range from 7.77 million to 10 million.
It's important to note that these are just estimates, and the actual number is likely much higher. The diversity of life on Earth is truly astounding!