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Chapter 2 Principles of Ecology. 2.1 Organisms and Their Relationships. What is ecology?. Oikos Greek for “homestead” Ology means “study of” Scientific study of interactions among organisms and their environment
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Chapter 2 Principles of Ecology 2.1 Organisms and Their Relationships
What is ecology? • Oikos Greek for “homestead” • Ology means “study of” • Scientific study of interactions among organisms and their environment • Reveals relationships among living things (biotic) and nonliving (abiotic) parts of the world
What is ecology? • Uses both quantitative and descriptive research • Combines information and techniques from many scientific fields: • Mathematics • Chemistry • Physics • Geology • And many others
Aspects of Ecological Study • Biosphere: portion of the Earth that supports life • High in atmosphere to bottom of ocean • Extends several kilometers above the Earth’s surface and several kilometers below the surface of the ocean • Comparable to peel of an apple • Very diverse climate
Living thing affected by: • Abiotic factors • Air currents • Temperature • Moisture • Light • Soil composition • Terrain • And many others
Living thing affected by: • Biotic factors • Same species for protection, competition, food, and reproduction • Other species for all but reproduction Tree decay
Levels of Organization in Ecology • Need to study more than just an individual to get the whole story • Need to study relationships or interactions among organisms of the same and different species
Levels of Organization in Ecology • Biosphere • Ecosystem • Community • Population • Organism
Populations • A group of organisms of one species that interbreed and live together in the same place at the same time
Populations • Compete with each other for food, water, space, light and other resources in short supply • How organisms share resources determines how far apart they live and how large a population gets
Populations • Some species reduce competition by larvae and adult stages living in different environments and using different resources as food (frogs and many insects)
Individuals Interact within Communities • Community: collection of interacting populations (all the populations at one place and time) • Change in one population will cause change in another population • Small changes • Large changes
Interactions among living things and abiotic factors • Ecosystem: interaction of populations in a community and nonliving (physical) surroundings • Three kinds of ecosystems • Terrestrial (land) • Fresh water • Marine: 75% of the earth
Organisms in Ecosystems • Habitat: place where an organism lives its life (home)
Organisms in Ecosystems • Niche: the role and position a species plays in its environment • All the interactions with abiotic and biotic factors • Everything the species does • How it uses resources • Its job
Organisms in Ecosystems • Even though two species occupy the same habitat, they do not occupy the same niche because resources (food, shelter) are used in different ways • It is an advantage for a species to occupy a different niche, unique strategies are important to reduce competition
Symbiosis • Permanent, close association between two or more organisms of different species • Three types of symbiosis • Commensalism • Mutualism • Parasitism
Commensalism • One species benefits, other species not harmed or benefited • Few examples because further study usually reveals mutualism or parasitism
Commensalism • Cattle egrets follow cattle to feed on the insects stirred up by the grazing cattle. • Egret benefits as it gets more food • Cattle is neither helped nor harmed
Commensalism • Orchids growing on trees have a home and moisture • Orchids benefit while the tree is not affected
Mutualism • Both species benefit
Mutualism A remarkable 3-way mutualism appears to have evolved between an ant, a butterfly caterpillar, and an acacia in the American southwest. The caterpillars have nectar organs which the ants drink from, and the acacia tolerates the feeding caterpillars. The ants appear to provide some protection for both plant and caterpillar. Research of Diane Wagner, American Museum of Natural History Southwestern Research Station
Mutualism • Ants “tending” soybean aphids
Parasitism • One organism benefits the other is harmed but usually not killed Ticks Ring Worm
Chapter 2 Principles of Ecology 2.2 Flow of Energy in an Ecosystem
How Organisms Obtain Energy • Ultimate source of energy is the sun • Producers use the sun’s energy to make food • Consumers eat producers of other consumers
How Organisms Obtain Energy • Autotrophs: “auto” = self; “troph”= energy • Most are photoautotrophs: organisms that use the sun’s energy to make food in the process of photosynthesis; all have chlorophyll • Some are chemoautotrophs; make food by using energy stored in chemical bonds (some Archaebacteria)
Photoautotrophs Cyanobacteria Plants Algae
How Organisms Obtain Energy • Heterotrophs: “hetero”= other; “troph”= energy • Can’t make food so must feed on other organisms • Herbivores: only eat autotrophs • Carnivores: only eat other heterotrophs • Omnivore: eat both autotrophs and heterotrophs
How Organisms Obtain Energy • Heterotrophs: “hetero”= other; “troph”= energy, cont. • Scavengers: feed on dead (carrion and refuse) • Decomposers: breakdown and absorb nutrients from dead organisms (fungi, protozoans, many bacteria)
Heterotrophs Carnivore Decomposer Scavenger Herbivore
Detritivores Eat fragments of dead matter in an ecosystem, and return nutrients to the soil, air, and water where the nutrients can be reused by organisms. Also considered heterotrophs How Organisms Obtain Energy
Matter and Energy Flow • Food Chains: simple model to show energy flow in an ecosystem; one possible route • Food web: several interconnected food chains • shows that an organism occupies more than one trophic level • Expresses more possible feeding relationships at each trophic level • More realistic than a food chain
Food Chain • Arrows indicate direction energy flows • Usually 3 to 5 trophic (energy) levels • On average only 10% of energy is transferred to next trophic level • Most energy is lost as heat • Also lost as urine, feces and other
Food Chain Top Carnivore Carnivore Omnivore Herbivore Producer
Food Web • Trophic level is one step in a food chain • Organisms can occupy more than one trophic level • Important part of organism’s niche is how it obtains energy
Energy and Trophic Levels Energy Pyramid
Pyramid of Numbers Count the number of organisms at each level Numbers decrease as move up the pyramid Not always reveals true relationship as one tree (producer) could support 50,000 insects (herbivore) Energy Pyramids
Pyramid of Biomass Use dry weight of organisms at each level Energy Pyramids
Energy Pyramids Pyramid of Numbers Pyramid of Biomass
Chapter 2 Principles of Ecology 2.3 Cycling of Matter
Cycles in Nature • Energy flows, nutrients cycle • Atoms of carbon, nitrogen and other elements in your body today made up the bodies of other organisms • Matter including nutrients are constantly recycled • The cycling of nutrients in the biosphere involves both matter in living organisms and physical processes found in the environment such as weathering.
