What are the main causes of biodiversity loss?

A zombie apocalypse wipes out almost the entire human species before the zombie threat is eliminated. Only a group of 100 people who were at a family reunion on an uninhabited island survived. They returned to the mainland completely unaware of what had happened to everyone. Regarding the few survivors who now begin to rebuild the human population. Which process of evolution does not change the total number of species?

Imagine you were the manager of a national park with cheetahs. The cheetahs feed primarily on gazelles, while the gazelles eat grass. It takes an acre of grassland to feed one gazelle, and it takes ten gazelles to feed one cheetah. You have a maximum of ten cheetahs when the system is functioning optimally. You would like to increase the cheetah population because people pay money to see the cheetahs. How much total grassland do you need to double the cheetah population supported by this grassland?

What causes the annual growth rings of trees?

Which growth model would you expect to see in a stable population?