The correct answer is option 1, which states that statement 1 (Biodiversity hot spots are identified by the International Union for Conservation of Nature and Natural Resources - IUCN) and statement 2 (Biodiversity hot spots are defined according to their vegetation) are correct.

Let`s dissect each option to better understand why the answer is correct:

Option 1: The statement 1 is correct. Biodiversity hot spots are indeed identified by the International Union for Conservation of Nature and Natural Resources (IUCN). This organization uses specific criteria to determine which areas are considered hot spots based on the level of biodiversity and threat of extinction.

Option 2: The statement 3 is incorrect. Biodiversity hot spots are not defined according to their vegetation alone. While vegetation can be an important factor in determining the biodiversity of an area, the IUCN considers a range of factors, including the presence of endemic species and the degree of habitat loss.

Option 3: This option is incorrect. It suggests that all three statements are correct, but statement 3 is incorrect as explained above.

Option 4: This option is incorrect because it suggests that only statement 1 is correct, but statement 2 is also correct.

In conclusion, option 1 is