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Ecology –how & why organisms interact with each other & with environment Levels of Biological Organization 1. Species – group of similar organisms; successfully interbreed 2. Population – members of same species living in same area @ same time Levels of Biological Organization 3. Community – all populations living together & interacting 4. Ecosystem – a community together w/ abiotic (nonliving) part of environment Populations How Do We Determine How Populations Change In Size? Growth rate (r) – birth rate minus death rate r=b-d r = (+), r = (-), r = (0) Types of Population Growth What type of growth is this? Types of Population Growth Exponential pop. growth (J curve) –occurs when optimal conditions allow a constant growth rate Types of Population Growth The larger the pop. gets, the faster it grows, doubling each time. Types of Population Growth What type of growth is this? Types of Population Growth Logistic population growth (S curve) – initial exponential increase, levels out as carrying capacity is reached What’s Carrying Capacity (K)? Types of Population Growth Logistic population growth (S curve) – initial exponential increase, levels out as carrying capacity is reached Carrying capacity (K) The largest population that can be supported by available resources. Effects of a Limiting Resource in a Population Human Population What kind of growth? http://www.census.gov/main/www/popclock.html l Reproductive Strategies r-selected species (opportunistic) – have traits that contribute to high population growth rate (r) Examples of r-selected species? Characteristics that r-selected species would have? Reproductive Strategies r-selected species (opportunists) – traits that contribute to high population growth rate (r) Examples of r-selected species? Characteristics that r-selected species would have? Reproductive Strategies K-selected species – have traits that maximize chance of surviving in environment where # of individs. is near carrying capacity (K) Examples of K-selected species? Characteristics that K-selected species would have? Communities Types of Interactions Predator/Prey Interactions What do predators tend to prey on? Why are predator/prey interactions important? Predators prey on weak and sick, forcing prey to become more fit Predators are forced to become more fit. Affects fitness of organisms! Why are predator/prey interactions important? How is predator affecting prey and vice versa? Why are predator/prey interactions important? Controls abundances of organisms!! Why are predator/prey interactions important? How is predator affecting the number of species in intertidal (tide pool) community? Why are predator/prey interactions important? Predators keep prey #’s in check so prey will not out compete each other and form a monoculture and lower species diversity. Predator in Kelp Forest Community: Sea Otter Kelp Forest Community Major Grazer of Kelp: Sea Urchins Urchin Barrens Urchin Predators In Kelp Forest Community What happens to this food web if we remove predators? Algae & Seastar Consumers in Coral Reef Community Giant Triton Coral Killers Crown of Thorns seastar Overgrowth of algae What will happen if these species disappear from a community? Types of Interactions Symbiosis “living together”– any association between 2 or more species Types of Interactions Competition – occurs when 2 or more individuals use an essential, limited resource What is the outcome of head to head competition? Competitive exclusion - 1 species is excluded from portion of community by another Resource partitioning – differences in resource use among species; dividing the resource Shorebird Bill Shapes & Feeding Strategies Ecosystems How energy flows in ecosystems What is being given off at each level? Food Chains – energy moves from one organism to the next in a sequence (one way flow) Rarely exists in nature Food web- complex of interconnected food chains More likely in nature Trophic level- each level in the food chain At each level heat is given off that is unavailable to next level Energy Pyramids Displays amount of living material (energy) available at each trophic level Why is there a stepwise decline of biomass as you go up levels? How much energy will be transferred to the animal that eats the caterpillar? Heat Heat Most consumed energy goes towards cellular respiration and lost as heat and waste Only a small amount goes toward actual growth (stored energy) and is transferred to next level Only a small amount goes toward actual growth (stored energy) and is transferred to next level So, is there more energy available at the higher or lower levels? Why more zebras than lions? www.animals.timduru.org www.game-reserve.com Why more krill than orcas? Because of stepwise decline, more energy is available to lower level consumers and higher numbers of them can be supported. What type of consumer is more “expensive” for an ecosystem to support? Why? How many levels do high level consumers consume compared to low level consumers? Carnivores are “expensive” to support because they “consume” more levels ! Why can certain animals at lower trophic levels be much larger in size than carnivores? www.animals.timduru.org Because of stepwise decline, more energy is available to lower level consumers and larger sized animals can be supported. www.animals.timduru.org Because of stepwise decline, more energy is available to lower level consumers and larger sized animals can be supported. www.sps.nus.edu.sg www.hoglezoo.org Whose at a higher trophic level, the orca or the baleen whale? So what will be able to be larger in size? Fig. 9.18 Fig. 8.5 Vegetarians vs. Meat Eaters What level is consuming more energy & is more expensive for an ecosystem to support? Vegetarians vs. Meat Eaters Takes 10 lbs of feed corn to produce 1 lb of bacon or beef steak Being meat eater is an inefficient way of using photosynthetic productivity (energy)