Ecological Biology

we live in a crowded World 2 million kinds of living things occupying every imaginable place [Music] a seashore home to strange exotically beautiful life forms a high mountain snowfield here live vast numbers of tiny organisms red pigments Shield their delicate cell Machinery from intense ultraviolet radiation found at high altitude they are well adapted for this mars-like environment and live here without competition from other life forms at the Mountain's base is another kind of extreme environment a hot spring near the boiling point living things abound but they are very primitive microscopic forms of life [Applause] [Music] the field of biology that investigates why organisms live where they do and how their populations interact is ecology ecologists may study the distribution of organisms in space and time or they investigate broader questions how does energy flow through a living community how are materials shuffled around within an ecological system others focus on single populations what affects them what do they affect at any of these levels ecology becomes a complex and fascinating inquiry into the interconnected threads that bind all living things feeding competing capturing or being captured [Music] along an isolated Coastline the shifting tide washes over the rocks in its daily cycle here is a fantastic natural laboratory for investigating how populations interact with each other and with their environment muscles for example why do these common shellfish form a dark band along the wave-washed coast looking at the sharply defined muscle beds an ecologist starts asking questions could food limit the muscles more information is needed what do they eat microorganisms filtered from the sea water wherever waves wash over the intertial Rocks food is available so why are the muscles limited food must not be the answer at least not the whole answer how important are Predators birds can get at the upper muscles and dine at leisure while the tide is [Music] out how about competing species Barnacles cover the Rocks just above the muscle beds could Barnacles limit the muscles by occupying their growing space perhaps the delicate muscle larv cannot survive on the hot dry rocks above protection of adults experiments have shown that all of these factors can play a role in governing the muscle population's upper border but the lower border is another problem almost everyone who visits the sea has seen starfish dining on muscles could predation by starfish limit the lower border of the muscle bed Studies have shown that starfish cannot tolerate as much exposure as muscle these slow moving Predators must live well below their prey as the tide comes in they creep at imperceptible speed to the lowest muscles feed and return before receiving Too much exposure to Sun and drying air evidence that starfish limit muscle distribution came from a bold experiment in which all starfish were removed from a stretch of Coastline result the lower border gradually extended in 2 years doubling the size of the muscle bed the nice thing about studying muscles and Starfish is that they hold still you can count them remove one species or the other and check the effects however Predator prey interactions are not always this easy how many mountain lions live in this Canyon how many deer you can search for days and not see one of these secretive animals avoiding such difficulties some ecologists have taken the problem of interacting populations into the lab and put it under the microscope meet didinium its name means terrible nose with good reason for this is a predator as ferocious as any which spring from the imagination of Science Fiction didinium is a microscopic wolf with an appetite for only one kind of prey the smoothly swimming slipper-shaped parami [Music] [Music] these scenes photographed in natural time show an awesome example of predation a predator swallows a prey larger than itself in 30 minutes it will take another and then [Music] another after engorging didinium divides producing new individuals that will repeat the ravenous process again and again with such an efficient Predator at large its prey should be brought to Extinction yet parium continues to be one of the most abundant organisms in lakes and ponds how is this possible such questions can be answered through experiments that allow populations to interact in a controlled way to begin a few daia are added to a culture of paramia and daily counts are made of both [Music] populations by day six daia are becoming abundant in the culture on day seven a few paramia are left hiding in the bushes and there are a great many daia dinner is [Music] over on day eight an interesting change every didinium in the culture has developed a shell-like covering that shows up brightly under polarized light within its protective shell a didinium enters a state of dorcy suspended in time its Predator temporarily out of the way parium population builds up until responding to chemical signals a didinium comes out of dorcy and the feasting begins all over again this relationship has been going on cycle after cycle for Untold millions of years like starfish and muscle the association continues because in its natural environment Predator cannot eliminate its prey [Music] however if paramia are cultured in a clean dish a simplified environment with no microscopic bushes or fish skeletons to hide in the daia will totally consume their prey they compete for the very last parium ending a cycle and bringing about their own Extinction [Music] only in a complex environment one with bushes and organisms to get in the way can parium and didinium coexist laboratory studies of this kind bring up questions about our own ecology for example humans depend upon a highly simplified environment for food single crops grown on huge factory-like farms in order to understand our own system ecologists would like to know more about natural systems the Earth itself is a giant ecological system sunlight streams in energy for Life carbon dioxide water nitrogen oxygen raw materials flowing in great Cycles between atmosphere and living world ecologists call this global life support system the biosphere within the biosphere are more or less distinct ecological units called ecosystems a seashore is one kind of ecosystem a pond another Forest desert grassland each system has its own character yet in basic ways these major ecosystems are alike for example all run on solar energy as plants the food producers convert light into the chemical energy of food this process photosynthesis occurs in tiny green bodies within plant cells using light energy these chloroplasts manufacture essential nutrient molecules Ino raw materials carbon dioxide water nitrates phosphates and sulfur compounds out come carbohy hydrates fats proteins nucleic acids the molecules of life when an animal eats a plant it picks up a supply of biological molecules molecules that can be used in two ways for energy to drive its metabolism and as a source of materials for building its own products what effect can these molecular level events have on ecosystems St studies show that only a small fraction of energy contained in one organism is transferred to the next Consumer most of the energy picked up in food is used in activity and lost as [Music] heat because of this low transfer of energy an ecosystem can be expected to have a greater mass of producers than consumers and more plant eaters than predators amount of growing area required to support a human population will depend upon what they choose to eat if this plot supports X number of people eating plant Foods a much greater area would be required if these crops were fed to animals and animal products were eaten instead as long as the sun shines energy for life is renewable but what about raw materials used by plants to synthesize food nitrogen for example imagine a nitrogen atom contained in a protein part of a plant cell in winter when the plant dies back the protein is digested by a bacterium and our atom becomes incorporated into a bacterial protein the bacterium is eaten by an earthworm and the nitrogen atom is returned to the soil in the worm's waste products picked up by a root hair our nitrogen is again incorporated into plant protein animals eat plants and in turn are eaten or die nothing is wasted as borrowed molecules return to the system through the activities of scavengers and decomposers shuffling molecules is a vitally important ecological process if raw materials are not kept in circulation an ecosystem runs down and supports less and less life this is exactly what happens when range animals go to market they carry away borrowed molecules and the range becomes less productive recycling is what keeps natural ecosystems running however modern agriculture is an ecological system that for the most part does not recycle materials the is removed its molecules pass through our bodies and are then deposited in a sewage treatment plant from here they go into a river or the sea but in few cases are they returned to the fields to nourish new plants instead fertilizer made with a high energy cost is brought in to ensure next year's crop how long can this forced system of food production continue to work another important question the New Field of human ecology must try to answer ecology is a relatively new science but its findings already carry an important message humans are part of Earth's life support system how we fit our activities into the great cycles of the biosphere and how we choose to interact with other living things will determine the quality of life from here on for [Music] here [Music]