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Principles of Ecology So . . . Chapter 3 “We can't solve problems by using the same kind off thinkingg we used when we created them.” ~Albert Einstein Biological Organization Ecological Concepts Ecology: Study of how organisms interact with each other and with their non-living g surroundings. g z Environment: Everything that affects an organism during its lifetime. z – Biotic—Living component – Abiotic—Non-living component Genes, Populations, and Species z z z Genes—Distinct pieces of DNA that determine an individual’s characteristics. Population—All organisms of the same kind found within a specific geographic region. Species—Population of all organisms potentially capable of reproducing naturally among themselves, and producing viable offspring. z Ecosystems are the most complex level of biological organization: cells, tissues, organs, organisms, populations, communities, ecosystems Law of Conservation of Matter z z z Although matter can be changed from one form to another, it can neither be created nor destroyed by ordinary physical h i l and d chemical h i l means There is no such thing as throwing something “away” We all have carbon atoms that were in dinosaurs Laws of Thermodynamics First Law = Energy can not be created nor destroyed; it can be changed g from one form to another z Second Law = When energy is converted from one form to another, energy is lost in the form of heat. z – Nothing is 100% efficient Electromagnetic Spectrum Fate of light impinging on earth Food Chains and Food Webs photosynthesis z Food Chain—Passage of energy from one trophic level to the next due to one organism g consuming g another. z Food Web—Series of multiple food chains. – Some chains rely on detritus. – A single predator can have multiple z 6CO2 + 6H2O = C6H12O6 + 6O2 prey species at the same time. Food Chain - Food Web Producer : convert about 1% of sun energy into organic energy z Consumer: 90% loss of energy loss at each step z Decomposer : Recycle energy and atoms from non-living organic matter little waste. z Fig. 5.15a Energy Flow Through Ecosystems z z z Each step in the flow of energy through an ecosystem is known as a trophic level. As energy moves from one trophic level to the next, most of the useful energy (90%) is lost as heat. (2nd Law of Thermodynamics) Because energy is difficult to track, biomass (weight of living material) is often used as a proxy. Biogeochemical Cycles All substances in organisms cycle through ecosystems z Bulk of substances are not contained within the bodies of organisms z Organisms must be able to move these substances from abiotic into biotic systems. z Carbon Cycle z z z z z Carbon Cycle Carbon and Oxygen combine to form Carbon Dioxide. Plants use Carbon Dioxide during photosynthesis to produce sugars. sugars Plants use sugars for plant growth. Herbivores eat plants, and incorporate molecules into their structure. Respiration breaks down sugars releasing CO2 and water back into the atmosphere. Based on atmospheric carbon dioxide (0.039% of air) z Plants (and some bacteria) make 70 billion tons of organic compounds per year z Carbon dioxide is released into the atmosphere from respiration z Nitrogen Cycle z Cycling of nitrogen atoms between abiotic and biotic ecosystem components. – Producers unable to use atmospheric N. z Must get nitrate (NO3) or ammonia (NH3). – Nitrogen-fixing bacteria converts nitrogen gas (N2) into ammonia. z Plants construct organic molecules. – Eaten by animals. – Decomposers also break down nitrogen- containing molecules releasing ammonia. Nitrogen Fixers z Free living and symbiotic bacteria z Ammonification - Conversion of Nitrogen to NH3 (ammonia). Some are free living (cyanobacteria) and some are symbiotic (Rhizobium sp) Nitrogen fixers - Rhizobium Nitrifiers De--Nitrifiers De Two different groups of bacteria working in sequence. z Organic→ammonia (fungi) →nitrite (Nitrosomas sp.) → Nitrate (Nitrobacter sp) → Organic (via plants) plants). z Plants can produce all 20 amino acids z Many animals and humans cannot produce 8 amino acids (lysine, tryptophan, threonine, methionine, z z Requires anoxic (no oxygen) conditions z Nitrites to nitrogen gas z NH3 → NO2 (Nitrosomas) → N2O (Pseudomonas, Bacillus) → N2 phenylalanine, leucine, isoleucine, valine. Phosphorus Cycle Bulk of phosphorus on earth is in the ocean … only small amounts in soil (phosphate rock). z Needed in life for nucleic acids and ATP z Plants take in through roots (PO4) z Animals eat plants z Decomposers return it to soil z Human Impact on Nutrient Cycles z Two activities caused significant changes in carbon cycle: – Burning Fossil Fuels. – Converting forests to agricultural land. Fossil fuel burning also increased amount of nitrogen available to plants. z Fertilizer carried into aquatic ecosystems. z z Increase aquatic plant growth rate. – Lowered oxygen concentrations. Fig. 5.19 Ecological Concepts z Limiting factors – The absence of a key factor needed for success. Not life, just success. z Range of tolerance – Certain organisms “prefer” certain environmental conditions. Habitat and Niche The “Where” and the “How” z Habitat: where the organism lives z Niche: Includes space, food, temperature, conditions for mating, g “job” j etc…. The organisms z Also takes into account behavior at various seasons or times of the day z Niche is NOT synonymous with habitat - habitat is a region, niche is a functional role z Natural Selection Conditions Natural Selection – Excess number of individuals results in a shortage of specific resources. z z Natural Selection—Process that determines which individuals within a species will reproduce and pass their genes to t th the nextt generation. ti Conditions: – Individuals within a species show variation. – Organisms within a species typically produce huge numbers of offspring, most of which die. Fig. 5.6 – Due to individual variation, some individuals have a greater chance of obtaining needed resources and thus have a greater likelihood off survival i l and d reproduction. d ti – As time passes, percentage of individuals showing favorable variations will increase while percentage showing unfavorable variations will decrease. Kinds of Organism Interactions Competition z Competition—Two organisms compete to obtain the same limited resource, and both are harmed to some extent. Competition z – Intraspecific—Members of same species competing for resources. – Less fit species must evolve into a – Interspecific—Members of different species slightly different niche. competing for resources. z The more similar the competing species, the more intense the competition. Predation z Competitive Exclusion Principle—No two species can occupy the same ecological g niche in the same place p at the same time. Predation—One animal kills/eats another. – Predator benefits from food. z Prey adaptation is manifested in a higher reproduction rate. – Prey species benefits by eliminating non-adaptive genes from the gene pool. z Poorly adapted predators are less likely to obtain food and thus pass on non-adaptive genes. Predation Predation limits the size of populations z Prey y must survive in at least small numbers or predator becomes extinct. z Prey have evolved to have unique defenses against predators. Moth eye pattern, cactus, armadillo z Community and Ecosystem Interactions Community—Assemblage of all interacting species of organisms in an area. z Ecosystem—System of all interacting organisms, including their non-living surroundings. z Community and Ecosystem Interactions z z z z Major Roles of Organisms in Ecosystems Ecosystem Roles Producers: Make complex from simple Consumers: rely on producers as food Primary - herbivores Secondary - eat primary consumers Tertiary - carnivores, omnivores, scavengers, parasites Decomposers - Eats non-living organic matter as a source of food z Producers—Organisms able to use sources of energy to make complex organic g molecules from simple p inorganic molecules in the environment. Roles of Organisms Roles of Organisms z Consumers—Consume organic matter to provide themselves with energy and organic matter necessary for growth and survival. – Primary Consumers z Herbivores (plants) z Decomposers – Digest organic molecules in detritus into simpler organic compounds, and absorb soluble nutrients. (Bacteria and fungi) z z Use non-living organic matter as source of energy. Keystone Species – Play critical role in maintenance of specific ecosystems. – Secondary Consumers z Carnivores (meat) z Omnivores (plants and meat) Primary Sucession Table 5.01 Secondary Sucession