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 Biome 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

Organisms in Ecosystems

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 and 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

How Organisms Obtain Energy 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

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

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

Energy Pyramids 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 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.

Carbon Cycle

Nitrogen Cycle

Phosphorus Cycle

General Cycle