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Ecology • Branch of biology that studies the interactions between organisms and their environment • All of the locations on Earth that can support life Biosphere Abiotic Vs. Biotic Abiotic • Non living factor in an environment Examples • rocks • water • sunlight Abiotic Vs. Biotic Biotic • Living factors in an environment Examples • plants • animals • bacteria Levels of life • Ecologists look at individual organisms (level 1) • organisms that have similar characteristics can mate and produce fertile offspring are a species Population • Group of organisms of a single species that live in a given area Community • A collection of interacting populations in a given area Ecosystem Collection of organisms that interact with each other and with abiotic factors in the environment Landscape a group of ecosystems which affect one another Ecotone (edge effect) a transition area between ecosystems, with blended characteristics Ecotones are often caused by underlying environmental gradients Energy in the Ecosystem Organisms • Autotrophsmake own food producers • Heterotrophmust get nutrients from outside sources consumers Organisms • Carnivore • Herbivore • Omnivore Organisms • Decomposers: break down dead organisms into simple molecules • Scavengers: feed off dead animals Trophic Level • Feeding level on food, energy, or biomass pyramid • Starts with primary producers • Ends with highest level consumer Food Chain • One set of organisms moving up through the trophic levels • Grass mouse fox hawk Food Web • Interconnecting food chains in an ecological community • More than one food chain Importance of decomposers • Because of decomposers the same atoms that made up the dinosaur's cells make up our cells!! Energy Pyramid • Illustrates that energy decreases at each succeeding trophic level • Usually square shaped • Only 10% energy moves up Populations populations • Group of organisms of the same species living in the same location • Change in population size is called growth rate (can be + or -) Populations Can Grow, Shrink, or Remain Stable • Population size governed by – – – – Births Deaths Immigration Emigration • Population change = (births + immigration) – (deaths + emigration) Growing population • Ideal conditions • Healthy organisms reproduce faster • Birth rate is higher than death rate Species Have Different Reproductive Patterns r-Selected species • • • • • Short life Rapid growth Early maturity Many small offspring Low on trophic level Characteristics of r-selected reproductive pattern species • Unpredictable environments • Small body size • Mature rapidly • Reproduce early • Short life span Species Have Different Reproductive Patterns K-selected species • • • • • Long life Slow growth Late maturity Few, larger offspring High on trophic level Characteristics of K-selected reproductive species • Reproduce and mature slowly • Long-lived • Large body size Carrying capacity (k) • Largest number of individuals that can survive over long periods of time in a given environment • Size of population is stabilized Many species grow until capacity is reached and then level off BUT…. Boom and Bust Some species exponential growth and then fast crash can rise again or wait for some time before another boom Exponential Growth, Overshoot, and Population Crash of a Reindeer Density Dependent Limiting Factors • Operate more strongly on large populations • Usually works on stable populations Density Dependant Factors • Disease • Parasites • Competition (food, space) • Stress Density Independent Limiting Factors • Weather – storms, fires, droughts, heat, cold, floods, hurricanes • Human activities – toxic waste spill, pesticides, clear cutting Coevolution • the evolution of complementary adaptations in two or more species of organisms because of a special relationship that exists between them Examples Predator/ prey relationship • Cheetah can run very fast but lacks stamina • Gazelles have evolved stamina to escape cheetahs Batesian Mimicry • A harmless species (non poisonous) resembles a poisonous species Which butterfly has a bitter taste? Mullerian Mimicry • Two poisonous species look alike Queen Butterfly and Monarch are both poisonous Population Interactions Influence Abundance • When populations of different species interact, the effects on one on the other may be positive (+), negative (-) or neutral (0). • By comparing populations living alone and together, several types of interactions can be identified. FIVE IMPORTANT INTERACTIONS BETWEEN TWO SPECIES • • • • • COMMENSALISM (+/0) MUTUALISM (+/+) COMPETITION (-/-) PARASITISM (+/-) PREDATION (+/-) The symbols +, - and 0 refer to the effect of one species on another when both are living together. Competition LIVING ALONE LIVING TOGETHER COMPETITION 0 0 [When both populations live together, abundance of each is lower.] Law of Competitive Exclusion • No two species will occupy the same niche and compete for exactly the same resources for an extended period of time. • One will either migrate, become extinct, or partition the resource and utilize a subset of the same resource. • Given resource can only be partitioned a finite number of times. Resource Partitioning Competition • Interspecific - Competition between members of different species. • Intraspecific - Competition among members of the same species. – Often intense due to same space and nutritional requirements. • Territoriality - Organisms defend specific area containing resources, primarily against members of own species. • Resource Allocation and Spacing Intraspecific Competition Reindeer on St Mathews Island 7000 6000 6000 5000 Number • Resource depletion may result in too many individuals in the population. Thus, the population crashes. • Reindeer on Saint Matthews Island died off as the result of depletion of lichens (food). 4000 3000 2000 1350 1000 0 1940 42 29 1945 1950 1955 Year 1960 1965 1970 Intraspecific Competition • A seed company tells gardeners that planting plants too far apart or too close together will only produce a few seeds. Why? Intraspecific Competition • Territorial behavior has evolved in many species as a response to intraspecific competition. • Male red wing blackbirds stake out a territory in defense of nests and mates. Interspecific Competition Predation LIVING ALONE LIVING TOGETHER PREDATION + + [Prey (A) are in greatest abundance when predators are absent. Predators (B) are in greatest abundance when prey are present.] Predation • Feeds directly upon another living organism • Prey most successfully on slowest, weakest, least fit members of target population. – Reduce competition, population overgrowth, and stimulate natural selection. symbiosis Intimate living together of members of two or more species. • Commensalism - One member benefits while other is neither benefited nor harmed. – Cattle and Cattle Egrets • Mutualism - Both members benefit. – Bees and flowers • Parasitism - One member benefits at the expense of other. – Humans and Tapeworms COMMENSALISM » LIVING ALONE A B LIVING TOGETHER A B COMMENALISM 0 0 + 0 Species A is more abundant when there are more of species B present. Species B is not affected by the presence of A COMMENSALISM • The cattle egret and cattle or other grazing African ungulate species. • The egret benefits from catching insects that cattle “scare-up” while grazing. • Cattle unaffected. COMMENSALISM • Bromeliads are a group of flowering plants that attach to trees (epiphytes). They gain access to sunlight and catch water. • The trees are not harmed or benefited. Mutualism LIVING ALONE A B LIVING TOGETHER A B MUTUALISM + + [Both populations are found in greatest abundance when together.] MUTUALISM • pollination of flowering plants by an insect or humming bird. • The pollinator benefits from the interaction by receiving nectar. • The plant gets its pollen transferred from one plant to another. MUTUALISM • The lichen is a mutualistic association between a species of algae and a species of fungus. • The fungus retains water and takes up minerals. • The algae provides carbohydrates and other organic nutrients as the result of photosynthesis. Parasitism LIVING ALONE A B Parasitism + - LIVING TOGETHER A B - + Parasitism • Tick feeds off mammal benefitting the tick but harming the mammal. • How would this ecosystem be affected if the butterfly population decreased? • How would this ecosystem be affected if the coyote population decreased • How would this ecosystem be affected if the raven population increased? Limitations of where a species can live 1. Physiological stress due to environmental conditions 2. Competition with other species 3. Predation 4. Parasitism and disease 5. luck Critical Environmental Factors • Single factor in shortest supply relative to demand is the critical determinant in species distribution. – Example: a cactus species can not survive if temperature drops below 30º F for more than 12 hours. Tolerance Limits • Each environmental factor has both minimum and maximum levels, tolerance limits, beyond which a particular species cannot survive – Combination of many factors: temperature range, food availability, competitors, predators Tolerance Limits Limits of Range 1. Physical Barriers a. Oceans (humans, cattle, marsupials) b. Mountains (house finch) c. Ice (cactus, coral reefs) 2. Climatic 3. Altitude 4. Food 5. Water 6. Competitors Indicators • If we know the tolerance range of species, we can deduce the conditions in the environment based on the presence of a particular species – Example: trout require cool, clean well oxygenated water; if you see an abundance of trout, what does that tell you about the environment? Ecological Niche • Habitat - Place or set of environmental conditions where a particular organism lives. • Ecological Niche – Role a species plays in a biological community (e.g. large grassland herbivore) – Total set of environmental factors that determines a species’ distribution. – Generalists - Broad niche – Specialists - Narrow niche • When generalists and specialists collide, generalists usually win. Generalists North and Central America Omnivorous: berries, insects, eggs, small animals Specialists China Eat Bamboo Keystone Species • A keystone species is a species that plays a critical role in maintaining the structure of an ecological community and whose impact on the community is greater than would be expected based on its relative abundance or total biomass – Large predators – Critical food organisms (bamboo and pandas) – Often, many species are intricately interconnected so that it is difficult to tell which is the essential component. Starfish: Keystone Species Feeds on muscles and sea urchins Muscles will outcompete other species Sea Urchins over populate: decrease in corals