2.1 Describing Populations - PDF

2.1 How Populations Grow LESSON  Standards This content is unavailable when printing. n  Everyday Phenomenon...

2.1 How Populations Grow LESSON  Standards This content is unavailable when printing. n  Everyday Phenomenon io ut Vocabulary population density emigration rib population distribution exponential growth age structure logistic growth immigration ist carrying capacity rD fo ot N Off the coast of California, southern sea otters are making a comeback. These adorable mammals, along with the closely-related northern sea otters, once lived in an area that stretched from Baja California all the way up to Alaska. They were nearly wiped out by fur hunters during the eighteenth century. In 1911, otters were protected by international treaty, and their numbers have been increasing. Southern sea otters are still endangered because they live only along a short stretch of the California coastline. A single large oil spill could cause their extinction. Why does that matter ecologically? Sea otters are important in maintaining the balance of the ecosystem. Otters help maintain the kelp forests by preying on sea urchins and other invertebrates that eat the kelp. Meanwhile, divers off the coast of North Carolina couldn’t believe their eyes. They were certain they’d seen a lionfish. Why was that observation surprising? Because lionfish are native to the tropical Pacific Ocean, not the Atlantic ocean! Recently, more and more lionfish have been reported around Florida, throughout the Caribbean, and all around the Gulf of Mexico. Lionfish are still spreading. Fisheries and biologists are worried, because lionfish are predators that eat at least 70 species of native fishes. How did they get here? Why are their numbers increasing so rapidly? Can we control lionfish? n Describing Populations io Imagine that you’re investigating an endangered species like sea otters or an aggressively ut invading species like lionfish. Among the first questions you ask might be “How many individuals of this species live here?” “Where else do they live?” or “Are those populations rib stable, increasing, or decreasing?” Welcome to population biology! Ecologists study populations by examining their geographic range, growth rate, density and distribution, and age structure. ist rD fo ot N