Ecosystems: What They Are Chapter 2

2.1 Ecosystems: A Description

The Structure of Ecosystems

2.2 The Structure of Ecosystems

The Structure of Ecosystems Producers photo or chemo Herbivores Secondary Consumer eat plants carnivore eats meat secondary consumer omnivore eats meat & plants primary consumer secondary consumer parasite feeds on organism, usually without killing it secondary or primary

The Structure of Ecosystems

COMPOSTING

Africa

Egypt

Ghana ountry/ghana/home.htm

2.1 Ecosystems: A Description  Most basic plant community is the association  Plant community supports or limits the animal population  Populations of species are constantly interacting with the abiotic factors of an ecosystem

2.1 Ecosystems: A Description  A distinctive biotic community living in a certain environment  EX: forest, grassland, wetland, marsh, river, reef, log, sand dune  Transition between ecosystems is call ecotone  Landscape is the study of interactions between ecosystems

2.1 Ecosystems: A Description  Biomes are groupings of similar or related ecosystems or landscapes

The Structure of Ecosystems  Producers:  Create energy (food) from sunlight mostly through photosynthesis  Some bacteria can create energy through chemosynthesis

The Structure of Ecosystems  Key feature of organic material is the presence of carbon-hydrogen bonds

The Structure of Ecosystems  Parasites  Medical profession calls bacteria and virus parasites, pathogens  Found in nearly every major organism group  May live inside or out  Usually does not kill host but may weaken it so much it is more easily killed by other predators  Athletes foot, intestinal worms, mistletoe, bedbugs, ticks

The Structure of Ecosystems

 Food Chain: life is not this simple!  Food Web: now we’re talkin!  Levels of these webs are called trophic levels

The Structure of Ecosystems

 Usually no more 3-4 trophic levels (maybe 5 in marine systems)  Fundamental movement of chemical nutrients and stored energy through each level  Biomass is highest at first level (producers)  Biomass decreases with each subsequent level

The Structure of Ecosystems Why does biomass decrease? 3 reason:  Not all consumed material is converted to body mass, some used as energy  Some biomass is never eaten but goes to decomposers  Carnivores must be bigger than their prey. There is limit to animal size and space to live in

The Structure of Ecosystems  Not all ecosystem relationships are predator-prey  Some are mutualistic

The Structure of Ecosystems

 Competition is kept to a minimum in habitats because each organism has it’s own niche  This niche gives each organism a distinct time, place, and food type for living and eating  If 2 species share the same niche, one will be eliminated, competitive exclusion principle

The Structure of Ecosystems

 The degree to which each of these factors is present profoundly affects the type and number of organisms present in each habitat

The Structure of Ecosystems  Each species thrives under specific environmental regimes  Changing even one factor can create stress for the organism  For each environmental factor there is an optimum level  Anything above or below stresses or kills the organism (Law of Limiting Factors)

The Structure of Ecosystems Fundamental Principle Every species of plant and animal has an optimum range, zones of stress, and limits of tolerance with respect to every biological factor.

2.3 Ecosystems to Global Biomes  Climate is average temperature and precipitation  These occur in great variation creating wide variety of climates  Population densities will be greatest where conditions are optimal  Population decreases as any condition departs from optimal

2.3 Ecosystems to Global Biomes  6 major biomes (p. 45)  Precipitation is the primary deciding factor in a biome  Temperature is secondary

2.3 Ecosystems to Global Biomes Microclimates Affecting Biomes  Temp & precipitation may vary greatly within a climate region due to location  Altitude, soil type, topography, direction of slope, acidity, alkalinity, salinity, proximity to large body of water

2.3 Ecosystems to Global Biomes Biotic Factors Affecting Biomes  One species may change biome for another, EX tall plant creates too much shade for a sun lover  Absence of one species will eliminate other species due to lack of food

2.3 Ecosystems to Global Biomes Physical Barriers Affecting Biomes  Ocean, desert, mountain range, dams, croplands, human constructed sites

2.4 The Human Factor