So... Chapter 3. Ecosystems are the most complex level of biological organization:

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1 So... Principles of Ecology Chapter 3 We can't solve problems by using the same kind of thinking we used when we created them. ~Albert Einstein Ecological Concepts Ecology: Study of how organisms interact with each other and with their non-living surroundings. Environment: Everything that affects an organism during its lifetime. Biotic Living component Abiotic Non-living component Biological Organization Ecosystems are the most complex level of biological organization: cells, tissues, organs, organisms, populations, communities, ecosystems Genes, Populations, and Species 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.

2 Law of Conservation of Matter Although matter can be changed from one form to another, it can neither be created nor destroyed by ordinary physical and chemical 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 from one form to another Second Law = When energy is converted from one form to another, energy is lost in the form of heat. Nothing is 100% efficient Electromagnetic Spectrum Fate of light impinging on earth

3 photosynthesis 6CO 2 + 6H 2 O = C 6 H 12 O 6 + 6O 2 Food Chains and Food Webs Food Chain Passage of energy from one trophic level to the next due to one organism consuming another. Some chains rely on detritus. Food Web Series of multiple food chains. A single predator can have multiple prey species at the same time. Food Chain - Food Web Producer : convert about 1% of sun energy into organic energy Consumer: 90% loss of energy loss at each step Decomposer : Recycle energy and atoms from non-living organic matter little waste. Fig. 5.15a

4 Energy Flow Through Ecosystems 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. (2 nd 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 Bulk of substances are not contained within the bodies of organisms Organisms must be able to move these substances from abiotic into biotic systems.

5 Carbon Cycle Carbon and Oxygen combine to form Carbon Dioxide. Plants use Carbon Dioxide during photosynthesis to produce sugars. Plants use sugars for plant growth. Herbivores eat plants, and incorporate molecules into their structure. Respiration breaks down sugars releasing CO 2 and water back into the atmosphere. Carbon Cycle Based on atmospheric carbon dioxide (0.039% of air) Plants (and some bacteria) make 70 billion tons of organic compounds per year Carbon dioxide is released into the atmosphere from respiration Nitrogen Cycle Cycling of nitrogen atoms between abiotic and biotic ecosystem components. Producers unable to use atmospheric N. Must get nitrate (NO 3 ) or ammonia (NH 3 ). Nitrogen-fixing bacteria converts nitrogen gas (N 2 ) into ammonia. Plants construct organic molecules. Eaten by animals. Decomposers also break down nitrogencontaining molecules releasing ammonia. Nitrogen Fixers Nitrogen fixers - Rhizobium Free living and symbiotic bacteria Ammonification - Conversion of Nitrogen to NH 3 (ammonia). Some are free living (cyanobacteria) and some are symbiotic (Rhizobium sp)

6 Nitrifiers Two different groups of bacteria working in sequence. Organic ammonia (fungi) nitrite (Nitrosomas sp.) Nitrate (Nitrobacter sp) Organic (via plants). Plants can produce all 20 amino acids Many animals and humans cannot produce 8 amino acids (lysine, tryptophan, threonine, methionine, phenylalanine, leucine, isoleucine, valine. De-Nitrifiers Requires anoxic (no oxygen) conditions Nitrites to nitrogen gas NH 3 NO 2 (Nitrosomas) N 2 O (Pseudomonas, Bacillus) N 2 Phosphorus Cycle Bulk of phosphorus on earth is in the ocean only small amounts in soil (phosphate rock). Needed in life for nucleic acids and ATP Plants take in through roots (PO 4 ) Animals eat plants Decomposers return it to soil Human Impact on Nutrient Cycles 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. Fertilizer carried into aquatic ecosystems. Increase aquatic plant growth rate. Lowered oxygen concentrations.

7 Fig Ecological Concepts Limiting factors The absence of a key factor needed for success. Not life, just success. Range of tolerance Certain organisms prefer certain environmental conditions. Habitat and Niche The Where and the How Habitat: where the organism lives Niche: Includes space, food, temperature, conditions for mating, etc. The organisms job Also takes into account behavior at various seasons or times of the day Niche is NOT synonymous with habitat - habitat is a region, niche is a functional role

8 Natural Selection Natural Selection Process that determines which individuals within a species will reproduce and pass their genes to the next generation. Conditions: Individuals within a species show variation. Organisms within a species typically produce huge numbers of offspring, most of which die. Natural Selection Conditions Excess number of individuals results in a shortage of specific resources. Due to individual variation, some individuals have a greater chance of obtaining needed resources and thus have a greater likelihood of survival and reproduction. As time passes, percentage of individuals showing favorable variations will increase while percentage showing unfavorable variations will decrease. Fig. 5.6

9 Kinds of Organism Interactions Competition Competition Two organisms compete to obtain the same limited resource, and both are harmed to some extent. Intraspecific Members of same species competing for resources. Interspecific Members of different species competing for resources. The more similar the competing species, the more intense the competition. Competition Competitive Exclusion Principle No two species can occupy the same ecological niche in the same place at the same time. Less fit species must evolve into a slightly different niche. Predation Predation One animal kills/eats another. Predator benefits from food. Prey adaptation is manifested in a higher reproduction rate. Prey species benefits by eliminating non-adaptive genes from the gene pool. Poorly adapted predators are less likely to obtain food and thus pass on non-adaptive genes. Predation Predation limits the size of populations Prey must survive in at least small numbers or predator becomes extinct. Prey have evolved to have unique defenses against predators. Moth eye pattern, cactus, armadillo Community and Ecosystem Interactions Community Assemblage of all interacting species of organisms in an area. Ecosystem System of all interacting organisms, including their non-living surroundings.

10 Community and Ecosystem Interactions 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 Major Roles of Organisms in Ecosystems Producers Organisms able to use sources of energy to make complex organic molecules from simple inorganic molecules in the environment. Roles of Organisms Consumers Consume organic matter to provide themselves with energy and organic matter necessary for growth and survival. Primary Consumers Herbivores (plants) Secondary Consumers Carnivores (meat) Omnivores (plants and meat) Decomposers Roles of Organisms Digest organic molecules in detritus into simpler organic compounds, and absorb soluble nutrients. (Bacteria and fungi) Use non-living organic matter as source of energy. Keystone Species Play critical role in maintenance of specific ecosystems. Table 5.01 Primary Sucession

11 Secondary Sucession