Learn Turkish: İklim, Dünya'nın doğasını belirler. - The climate determines the Earth's nature.

The verb comes from belirlemek (to determine). The root is belirle-. Because the root ends in a vowel, making the aorist is simple: you just add the suffix -r to get belirler. Since the subject is "it" (İklim), it doesn't need any additional personal suffixes.

How do Dünya'nın and doğasını link together to mean "the Earth's nature"?

This forms a standard possessor-possessed relationship. The owner (Dünya, meaning Earth) takes the genitive suffix -nın (acting like "'s" in English). The owned item (doğa) takes the 3rd person possessive suffix -sı. The apostrophe is used because Dünya is a proper noun.

Why does doğasını have so many suffixes at the end?

Let's break it down! The root is doğa (nature). First, we add the possessive suffix -sı to mean "its nature". Next, because it is the specific direct object of the verb, it needs the accusative case suffix -ı. The -n- in the middle is a buffer letter always used when adding a case suffix to a 3rd-person possessive suffix: doğa + -sı + -n- + -ı.

Why is there a comma after İklim?