Transcript Chapter 4
Chapter 4 Ecosystems & Communities Chapter 4-1 The Role of Climate III. Ecosystem Definition: the combination of biotic and abiotic components through which energy flows and materials cycle (usually a self-contained unit, such as a pond, swamp, meadow, or woods) A. Energy Flow 1. Ultimate source - SUN - 50% of suns energy that collides with earth actually reaches the surface of earth - 0.1 % of that ends up in living organisms The Role of Climate Climate is caused by the interplay of many factors: Trapping of heat by the atmosphere Latitude Transport of heat by winds and ocean currents The amount of precipitation that results The shape and elevation of landmasses Maintenance of Earth’s Temperature Range Heat energy is trapped by atmospheric gases Carbon dioxide Methane Water vapor Other gases like CFCs, ozone, NO Without this greenhouse effect, Earth would be 30o Celsius cooler. Greenhouse Effect The Effect of Latitude Different parts of Earth’s surface receive varying amounts of solar radiation As a result of differences in latitude and thus the angle of heating, Earth has three main climate zones: Tropical- receives direct- or nearly-direct sunlight year-round Polar- near North and South poles, receive rays at a low angle The Effects of Latitude cont’d Temperate zones: between the other two zones, receive sunlight at changing angles throughout the year Latitude Wind Unequal heating of Earth’s surface causes warm air at equator to rise, and cooler near poles to sink This creates winds Earth’s rotation develops patterns called currents (example: Gulfstream current, Arctic current) Wind Ch 4-2 Biotic & Abiotic Factors Together determine the survival & growth of an organism as well as productivity of ecosystem in which the organism lives Biotic Factors Biological influences on organisms Birds, trees, mushrooms, bacteria- the ecological community Abiotic Factors Temperature Precipitation Humidity Wind Nutrient availability Soil type Sunlight The Niche Habitat = address. Doesn’t tell much about the individual. Niche = full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. The Niche Place in the food web Range of temperatures it needs to survive Tells when and how it reproduces Determined by biotic and abiotic factors Figure 4-5 Three Species of Warblers and Their Niches Cape May Warbler Feeds at the tips of branches near the top of the tree Bay-Breasted Warbler Feeds in the middle part of the tree Spruce tree Yellow-Rumped Warbler Feeds in the lower part of the tree and at the bases of the middle branches Community Interactions Community interactions such as competition, predation, and various forms of symbiosis can powerfully affect an ecosystem. Community Interactions Competition- occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time Community Interactions Resource- any necessity of life, such as water, nutrients, light, food or space Competitive exclusion principle- no two species can occupy the same niche In the same habitat at the same time Community Interactions Predation- an interaction in which one organism captures and feeds on another Community Interactions Symbiosis- any relationship in which two species live closely together Mutualism Both species benefit. Example: bees and pollen/nectar Mutualism Mutualism: both organisms benefit from living in close association. Example: ants and acacia trees. Community Interactions Commensalism One benefits, other unaffected. Example: barnacles on a whale Parasitism- when one organism lives in or on another organism, obtaining from its host all or part of its nutritional needs Commensalism Example: shark and pilot fish, moss and trees Parasitism Parasitism: one organism benefits at the expense of the other. Usually they do not kill the host. Example: ticks and fleas on dogs, mosquitoes on humans. Disturbance & Succession Ecosystems are constantly changing in response to natural and human disturbances. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. Called ecological succession. Ecological succession- the succession of communities that follows the disturbing of an area. Characteristics 1. Increase in total biomass 2. Gradual decrease in net productivity 3. Mature systems have a greater capacity to entrap and hold nutrients 4. Number of species increase 5. r-species early K-species late Climax community = final stable stage 1 10 2 20 5 Causes of Succession May result from slow changes in the environment that cause predictable shifts in living communities. Example: Freshwater pond fills with sediments and becomes a marsh. Can also be caused by sudden natural disturbance, like hurricane or fire. Example: fire on the prairie Primary & Secondary Succession Happens slowly because living organisms modify their environment a little at a time. Primary succession The colonization of new sites by colonies of organisms is called primary succession. Usually occurs on newly exposed surfaces. Eventually, repopulating slows down and becomes stable. If little or no succession is occurring this is called a climax community. Secondary Succession If a natural disaster or human action destroys a community without destroying the soil it is secondary succession. Community of organisms gradually changes New species replace pioneer species Climax community reached more quickly Examples: land plowed and cleared for farming, lightning fire on prairie