Ecology An Introduction to Ecology and the Biosphere
The Scope of Ecology • High in the sky, a series of satellites circle Earth. • These satellites aren’t relaying the chatter of cell phones. • They are transmitting data on the annual migration of gray whales.
The Journey of Gray Whales • Leaving their calving grounds near Baja California, adult and newborn gray whales (Eschrichtius robustus) swim side by side on a remarkable 8,000 km journey.
Headed to the Arctic • The whales are headed to the Arctic Ocean to feed on the crustaceans, tube worms and other creatures that thrive there in the summer. • Satellites track their progress.
Recovery from Brink of Extinction • Satellites also help scientists track the recovery of the blue whale from extinction. • A century ago, whaling had reduced the population to only a few hundred. • Today, after 70 years of protection, more than 20,000 travel to the Arctic each year.
Questions for Ecologists: • What environmental factors determine the geographic distribution of gray whales? • How do variations in their food supply affect the size of the gray whale population?
What is Ecology? • “oikos” = home, “logos” = to study • The scientific study of the interactions between organisms and the environment.
Studying Ecology at the Organism Level: • 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?
Population Ecology • 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?
Community Ecology • 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?
Ecosystem Ecology • 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: What factors control photosynthetic productivity in the savannah grassland of Africa?
Biome Ecology • A biome is a large region characterized by a specific kind of climate and certain kinds of plant and animal communities. • Biome Ecology focuses on the weather and climate patterns of an area (biogeography) that determines what kinds of organisms live there. Ex: How would a drought affect the population of Black-footed Ferrets in the prairie?
Global Ecology • 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. Ex: How does ocean circulation affect the global distribution of crustaceans?
Now You Try! • 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?
What would an example be of the following? • 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 in an Ecosystem • Biotic Factors in an ecosystem include those related to the activities of living things. Ex: • Food availability • Diseases & parasites • Density of the population • Human influence
Abiotic Factors in an Ecosystem • Nonliving factors tha affect population size are abiotic factors. • Weather & Climate • Availability of Sunlight • Availability of Water • pH of water/soil • Wind • Rocks/soil/mountains
Does feeding by sea urchins limit seaweed distribution? • 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% 60% 40% 20% 0% Both limpets and urchins removed Only urchins removed Only limpets removed Control-neither species removed Time-August 1983-February 1984
Conclusion • 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.
