Transcript AP Biology
Ecology “oikos” = home, “logos” = to study The scientific study of the interactions between organisms and the environment. Studies how an organism’s structure, physiology, and (for animals) behavior meet the challenges posed by its environment. Ex: How do hammerhead sharks select a mate? A population is a group of individuals of the same species living in an area. Population ecology analyzes factors that affect population size and why it changes through time. Ex:What is the carrying capacity of the Kaibab Forest whitetail deer population? A community is a group of populations of different species in an area. Community Ecology examines how interactions between species, such as predation and competition, affect community structure and organization. Ex: What factors influence the diversity of species that make up a forest? Ex: What factors control photosynthetic productivity in the savannah grassland of Africa? An ecosystem is the community of organisms in an area and the physical factors with which those organisms interact. Ecosystem Ecology emphasizes energy flow and chemical cycling between organisms and the environment. Ex: How does ocean circulation affect the global distribution of crustaceans? The biosphere is the global ecosystem-the sum of all the planet’s ecosystems. Global Ecology examines how the regional exchange of energy and materials influences the functioning and distribution of organisms across the biosphere. What level would a biologist be studying if he/she were: Counting the number of offspring born to a pride of lions? - Observing how a drought affects the number of blossoms on a Saguaro cactus? - Determining the effects of warming ocean temperatures on krill populations in the Antarctic? - Observing the behavior of Arctic wolves as they hunt migrating caribou in the Arctic? - Individual organism Population of that organism Community of that organism Ecosystem of that organism What biotic (living) factors and abiotic (nonliving) factors would influence where and how that organism lives? What are the limiting factors in that ecosystem? Biotic factors are living things in an ecosystem that influence how and where other organisms live. Biologists might ask: Why is Species X absent from an area? What biotic factors may limit its’ distribution? Burrowing owls are top carnivores— predators that can influence which species exist in an ecosystem W.J. Fletcher, of the University of Sydney, Australia, reasoned that if sea urchins are a limiting biotic factor, then more seaweeds should invade an area from which sea urchins have been removed. To isolate the effect of sea urchins from that of another seaweed-eating animal, the limpet, he removed only urchins, only limpets, or both from study areas adjacent to a control site. Seaweed Cover 100% 80% Both limpets and urchins removed 60% 40% Only urchins removed 20% Only limpets removed 0% Time-August 1983-February 1984 Control-neither species removed Removing both limpets and urchins resulted in the greatest increase in seaweed cover, indicating that both species have some influence on seaweed distribution. But, since removing only urchins greatly increased seaweed growth while removing only limpets had little effect, Fletcher concluded that sea urchins have a much greater effect than limpets on limiting seaweed distribution. Non-living factors can have a big influence on where species live. These include things such as temperature, water, salinity, sunlight, wind, and soil. Four of these: temperature, precipitation, sunlight, and wind are the major components of climate. The Great Salt Lake in Utah has a very low biodiversity. Why? Biodiversity is the variety of organisms in a given area. Physical factors (abiotic) have a big influence on biodiversity. Ex: Low temp or Low water = Low biodiversity Sahara Desert Forest The biodiversity of habitats and ecosystems varies widely. When ecosystems have high biodiversity, they are more resistant to damage. Systems with low biodiversity can be severely damaged easily. Biomes are major terrestrial or aquatic life zones, with characteristic vegetation and physical environments. Many aquatic biomes are physically and chemically stratified (layered). Photic Zone—where there is sufficient light for photosynthesis Aphotic Zone—where little light penetrates Benthic Zone—at the bottom of all aquatic biomes, made up of sand and organic and inorganic sediments Benthic organisms feed on dead organic matter called detritus, which “rains” down from the productive surface waters of the photic zone. Salinity, DO, and nutrient content varies widely Oligotrophic Lakes are nutrient-poor and generally oxygen-rich Eutrophic Lakes are nutrient-rich and often depleted with oxygen Runoff from fertilized land and dumping of wastes lead to nutrient enrichment, which can produce algal blooms and fish kills. An oligotrophic lake A eutrophic lake Draining and filling have destroyed up to 90% of wetlands which help purify water and reduce flooding. A wetland is a habitat that is inundated by water at least some of the time and that supports plants adapted to water-saturated soil. Wetlands are among the most productive biomes on Earth and are home to a diverse community of invertebrates (which in turn support a wide variety of birds.) Municipal, agricultural, and industrial pollution degrades water quality and kills aquatic organisms. Damming and flood control impede the natural flow. Headwater streams are generally cold, clear, turbulent, and swift. Farther downstream, the water is generally warmer and more turbid. A great diversity of fishes and invertebrates inhabit unpolluted rivers and streams. Estuaries are a transition area between river and sea. Seawater flows up the estuary channel during a rising tide and flows back down during the falling tide. Saltmarsh grasses and algae, along with an abundance of worms, oysters, crabs and many fish species. Many marine invertebrates and fishes use estuaries as a breeding ground. Estuaries are also crucial feeding areas for waterfowl and some marine mammals.