What are three things that humans do that can lead to the extinction of an animal species?

There are a LOT more than three here. If you need this for an assignment or whatever, pick the best three. # Habitat loss/destruction. If an animal's ecosystem (including the place where it lives, its relationships with predators and prey) breaks down and changes faster than it can adapt, it will die out. # Predation. If a new predator enters an ecosystem (usually a species introduced by humans) that the animal cannot defend itself against, it will be eaten out. # Hunting by humans. If an animal is intentionally sought and killed by humans as a pest, food animal or for novelty (ie elephants for tusks, tigers for pelts) and more are killed than the reproduction rate replaces the animal will become extinct. # Disease. If a new disease or mutation of an existing disease occurs that the animal has no immunity to, this can quickly sweep through and destroy a population. # Isolation. If the pockets of habitat where that animal can live are too small, the populations in any one place will be tiny. This makes them very fragile because they can easily be wiped out by disease, predators, a natural disaster etc. Also, isolated population pockets become inbred resulting in a far greater occurence of stillbirth and deformed young that do not survive. # Extreme conditions. An example would be a grazer's ecosystem being gripped by a drought. The grass will die and the animal will starve. These usually happen so fast that the population has no time to adapt to them. # Natural disasters. If a species' population is spread over a small area which is destroyed by a natural disaster, it has a fair chance of dying out.