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ECOLOGY “Ecology” – the scientific study of interactions among organisms and between organisms and their environment, or surroundings. The Biosphere & Ecology The biosphere contains the combined portions of the planet in which all life exists. This includes the land, air, and water. Levels of Organization The levels of organization that pertain to ecology are: Species/Organism – Population – a group of the same species that live in the same area. Community – the various populations that exist in a defined area. Ecosystem – a collection of all the organisms (communities) of a particular place together with their nonliving or physical environment. Biome – a group of ecosystems that have the same climate, and similar dominant communities. Methods of Ecological Study: 1. Observation 2. Experimentation 3. Modeling – since many ecological studies may involve long periods of time, or large spaces, ecologists can make models based on observation and experiments, and from there can make predictions. Energy Flow in Ecosystems: “Without a constant input of energy, living systems cannot function.” Producer : Autotroph : : Consumer : Heterotroph Autotrophs/Producers: -Sunlight is the main energy source for life on Earth. -Plants, some algae, and few bacteria are able to capture the sun’s energy and produce food. (mainly through photosynthesis) These organisms are called autotrophs (or producers). Heterotrophs/Consumers: -Heterotrophs (or consumers) rely on other organisms as their energy & food supply.. Types of heterotrophs: Herbivores – obtain energy by eating plants (cows, caterpillar, deer) Carnivores – eat animals (snakes, dogs, owls) Omnivores – eat both plants and animals (humans, bears, crows) Detritivores – feed on dead plant and animal matter (mites, worms) Feeding Relationships Energy flows in an ecosystem in one direction: The Sun → autotrophs → heterotrophs Food Chain – The way energy stored by producers is passed through an ecosystem. It is the way organisms transfer the energy by eating, or being eaten. Food web – Links all the food chains in an ecosystem together. Trophic Levels – Represents each step in a food chain. Producers are the 1st level, consumers are the 2nd, 3rd, or higher levels. Pyramid showing freshwater ecosystem trophic levels Energy pyramid – shows the energy stored in one level, and what is available for the next level. Only about 10% in one level is transferred to the next level. Cycles of Matter: Unlike one-way energy flow → , matter is recycled in and between ecosystems. The Water Cycle – Evaporation, Condensation, Precipitation, Runoff, Infiltration, Transpiration Nutrient cycles – Carbon, Nitrogen, Phosphorus, etc. Ecosystems: factors and interactions Biotic factors - all of the living parts of an ecosystem, with which an organism may interact. Abiotic factors – non-living factors which shape an ecosystem. Examples are temperature, precipitation, humidity, wind, soil type, sunlight. (see worksheet) Habitat & Niche: The area in which an organism lives is called its habitat. A habitat includes both biotic/abiotic factors. A niche is the full range of physical and biological conditions in which an organism lives. No two species can occupy the same niche in an ecosystem. “If a habitat is an organisms address in an ecosystem, then the niche is its occupation. “ Community interactions: Competition – organisms compete for resources in an ecosystem. A resource is a necessity of life (water, food, etc). Predation – Interaction where one organism captures and feeds on another. The one doing the killing is the predator. The one getting eaten is the prey. Symbiosis – Relationships where 2 organisms live closely together. There are 3 main classes of symbiosis: The 3 main classes of symbiosis: Mutualism – both species benefit from the relationship. (insects, and flowers) Commensalism – one organism benefits, and the other is not harmed or helped (barnacles & whales) Parasitism – one organism lives on, or inside another, and harms it. They generally weaken, but do not kill the host. (tapeworms, or ticks). Ecological succession: Ecosystems are constantly changing in response to natural and human disturbance. The series of predictable changes which occurs in an ecosystem over time is called ecological succession. Primary succession – occurs on surfaces where no soil exists. Examples are on bare rock left by melting glaciers, or recent lava flows. The first species to populate these areas are called pioneer species. (usually mosses & lichens) Secondary succession – occurs following a disturbance of a community without removing the soil. Examples are tilled farm lands, or areas of recent fires. Biomes Biomes are determined by abiotic factors, such as climate. A few examples of land biomes are; desert, tundra, rainforest, shrubland, and prairie. Other land areas that do not fit into the major biomes are the polar ice caps, and mountain ranges. Biome precipitation Biome data Aquatic Ecosystems: Aquatic ecosystems are determined by depth, flow, temperature, and chemistry of the overlying water. A few examples are described below: Freshwater ecosystems can be flowing water, or freestanding water. Freshwater wetlands water covers the soil for all or most of the year. Estuaries are wetlands formed where rivers meet the sea. These include salt-marshes and mangrove swamps. Marine ecosystems are within the ocean. They can be photic (receiving sunlight) aphotic (in the dark) Populations: Population size can be affected by: birth rate, death rate, emigration/immigration How Populations Grow 3 characteristics of a population are: 1. geographic distribution 2. density (# / area) 3. growth (2 types) 2 types of population growth: • Exponential Growth - occurs when individuals reproduce at a constant rate. Under ideal conditions, with unlimited resources, a population will grow exponentially. (J curve) • Logistic Growth - occurs when a population's growth slows or stops following a period of exponential growth. This is a result of resources becoming less available. (S curve). Carrying Capacity - the largest # of individuals that an ecosystem can support. (top part of the S curve). Exponential Growth J curve Logistic Growth S curve Carrying capacity approx. 650 Limiting factora factor causing population's growth to decrease. Density-dependent limiting factor - based on # of individuals in area. 3 factors include: Competition, predation, parasitism. Density-independent limiting factor - affect all populations in similar ways. Examples are: unusual weather, seasonal cycles, and human activity. Human Population Growth "The scientific study of human populations is called demography". Demographic transition - a dramatic change in birth and death rates. As countries become advanced in medicine, nutrition, and sanitation the death rate lowers, and demographic transition begins. Renewable & nonrenewable resources: Renewable resources - can regenerate, and are replaceable. They may however, become limited. Examples: Land, Forests, Ocean, Air, Water Nonrenewable resources - cannot be replenished by natural processes. Fossil fuels are an example. Biodiversity Biodiversity - is the sum total of the genetically based variety of organisms in the biosphere. Threats to biodiversity – Extinction- when a species disappears from all or part of its range. Endangered species - a species whose population size is declining, and is in danger of extinction. Habitat fragmentation - when an ecosystem splits into pieces. Hunting Pollution - such as biological magnification where a toxin is concentrated to higher amounts as you move higher in a food chain. Invasive species - non-native species introduced into a habitat which tend to reproduce rapidly. Other Ecology Vocabulary • Smog - a mixture of chemicals that appears as a graybrown haze in the atmosphere. • Pollutant - a harmful material that can enter the biosphere through air, land, or water. • Acid Rain - acidic gases are released by the burning of fossil fuels. These gases combine with water vapor to form drops of nitric and sulfuric acid. These can kill plants, and damage soil chemistry. • Deforestation - the loss of a forest, due to over use of raw materials. Results in loss of habitat, and soil erosion. • Desertification - areas which were once productive, but are not anymore due to farming, overgrazing, and drought. Other Ecology Topics • Ozone Depletion - the ozone layer absorbs a lot of UV radiation from the sun before it reaches Earth's surface. Satellites have shown a hole in our ozone layer over part of Antarctica, and more recently a hole over the Arctic appeared. – CFC's (chlorofluorocarbons) - cause the reduction of ozone as they break apart the ozone molecules (O3). Once widely used in aerosols and refrigerants, they are now under better control in most parts of the world. • Global Warming - the increase in the average temperature of the biosphere. Thought to be caused by too much Carbon dioxide in the atmosphere (a result of burning fossil fuels). If predictions are correct it could cause substantial melting of the polar ice caps and cause flooding. Also insect populations may increase.