What is ecology?The study of interactions betweenorganisms and their environment.
Ecology? Biology? Biology is simply the “study of life.” Ecology involves the interactions of living and nonliving aspects of the environment. Both biotic and abiotic factors are interconnected – a change in one, changes all the others over time.
Factors Biotic Factors Living factors Humans, plants, insects Abiotic Factors Nonliving factors Physical & chemical characteristics Temperature, pH, O concentration, 2 sunlight, H2O, soil
Abiotic? Biotic? Exploding human population Biotic Species endangerment/extinction Biotic Thinning of the ozone layer Abiotic Greenhouse effect Abiotic
Interactions at Levels Organism A single species Example: one blue gill Note: Since no organism is isolated, ecologists must use MODELS to study the environment and to make predictions about the future
Interactions at Levels Population Members of a single species Example: population of blue gills in a lake
Interactions at Levels Community A group of different populations that live in the same area Only living factors in an area interacting with each other Example: fish, turtles, algae
Interactions at Levels Ecosystem The interactions among living things and the nonliving things in an area Example: lake NOTE: Biomes are large ecosystems
Interactions at Levels Biosphere Broadest category The part of Earth where living things exist Example: atmosphere, lithosphere
Organisms Habitat Where an organism lives Niche What an organism does (its job or role) in its environment Role in the food chain & nutrient cycling Interactions with other species Two types of niches Fundamental niche Realized niche
Fundamental Niche The potential range of conditions and resources that an organism can assume Total range of environmental conditions that are suitable for a species existence Example: We can live anywhere in U.S. (tolerance)
Realized Niche The actual range of conditions and resources that an organism assumes Example: We live and do our “jobs” in Northbrook.
Ecological Roles Generalists Organisms with very broad niches Can live in many habitats, many conditions “Jack of all trades, master of none” Example: Opossum Cockroaches Mice Humans
Ecological Roles Specialists Organisms with very narrow and specific niches Live in one or few habitats, narrow range of conditions Out compete generalists in preferred habitats Example: Koala can only live and survive on Eucalyptus trees in Australia
Ecological Roles In a changing environment, it is better to be a generalist. In a stable environment, it is better to be a specialist.
What is a population?All the individuals of a single species living in an area
Population Size? Density? Population Size Number of individuals Population Density Number of individuals in an area Persons/square mile
Limiting Factors Density dependent limiting factors Factors that limit a population only when a population reaches a certain density Examples: Competition, predation, parasitism, disease, water availability
Limiting Factors Density independent limiting factors Factors that affect all population in the same way regardless of density Examples: Weather, natural disasters, seasonal cycles, pollution
Growth Rate Change in population size over time Depends on births, deaths, immigration (in), and emigration(out).
Growth Rate Populations grow exponentially until they reach carrying capacity (the maximum number of organisms that an area can support) Example: 1, 2, 4, 8, 16, 32….
Population Growth Models Exponential (J-shaped) Growth Curve Logistic (S-shaped) Model Boom and Bust Model
Exponential (J-shaped) Growth Curve Ideal Model Under ideal conditions: plenty of resources, no competition, no parasites, no predators, etc. Because of limiting factors, populations rarely exhibit J-shaped growth curves
Logistic (S-shaped) Model Realistic model Rapid growth, then slowing of growth and leveling off Regulated by carrying capacity (# of individuals which can be supported by resources of environment without damage to environment) Generally density dependent Growth is affected by the density of individuals
Boom and Bust Model Example: 26 reindeer were introduced onto an island off the coast of Alaska in 1910. Within 30 years the herd increased to 2,000. However, overgrazing reduced the food supply and the population crashed to 8 animals by 1950.
Boom and Bust Model Realistic Model Growth occur exponentially, but crash due to… Disturbance, such as weather Overexploitation of environment
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