Which of the following is a case of altruism?
1. a shrimp digs a burrow that it shares with a goby that keeps watch for predators.
2. a prairie dog gives up a foraging opportunity to keep watch for predators.
3. a baby bird aggressively begs, resulting in less food available to its siblings.
4. a plant releases allelopathic chemicals, harming its competitors and itself.
5. individuals in a flock of birds are less susceptible to predators than individuals alone.

economic

swahili is an extremely rich and complex civilization, a set of ethnic groups articulated by a language and a series of cultural elements that fuse the african traditions, islam and indian culture. this growth was largely a result of the indian ocean trading network that brought in not just man-made riches, but also religious ideas, specifically islam, which had a significant impact on the local culture. furthermore, the development of the swahili language gave a common cultural unity to the people.