Ecosystems and Energy Flow

• Matter is recycled between the abiotic and biotic components of the ecosystem
• Organisms get matter to build their bodies from the non-living (abiotic) environment
• Plants absorb CO2 from the air during photosynthesis to synthesize sugar molecules (C6H12O6)
• Ecology is the study of living organisms and their interaction with the nonliving environment
• Examples of what ecologists study:

  • Populations: same species in a given area, e.g. number of coyotes in El Dorado park
  • Communities: all populations in a given area, e.g. coyotes, plants, rabbits
  • Ecosystems: a community and its abiotic environment, e.g. coyotes, plants, rabbits plus sunlight, soil, water
  • Biosphere: all ecosystems inhabitants
• Population ecologists are concerned with demographics or evolution of populations (number of individuals and how they adapt)
• Community ecologists are concerned with interactions among organisms in an ecosystem (who eats who or who helps who)
• Salinity gradient set up by fresh water flowing into bay in Long Beach, CA demonstrates the relationship between abiotic factors and biological communities
• Long Beach has 1 ecosystem and 3 communities:

  • River (fresh): organisms adapted to fast-flowing fresh water, e.g. trout, bass, frogs, turtles, aquatic insects, ducks
  • Estuary (brackish): organisms adapted to still water and low salinity, e.g. cordgrass, periwinkles, herons, shorebirds, mosquito fish
  • Bay (salt): organisms adapted to ocean currents and high salinity, e.g. crabs, croaker, juvenile fish
• All species have minimum and maximum levels of any environmental factor in order to live and will exist in fewer numbers at the edges of the range
• Energy is the ability to do work and can exist in forms such as chemical energy, nuclear energy, solar energy, heat energy, mechanical, and electrical energy
• Thermodynamics is the study of energy transformations:

  • 1st Law: Energy cannot be created nor destroyed, may change from one form to another
  • 2nd Law: Energy available to do work decreases over time, systems spontaneously increase entropy
• Metabolism is the biological conversion of stored energy to ATP, where energy from the sun is converted by plants into sugar and then to ATP
• Energy flow in ecosystems involves producers (phototrophs, chemotrophs), consumers (heterotrophs), and decomposers (saprotrophs)
• Producers use solar radiation to produce sugar through photosynthesis, while chemotrophs use H2S to produce sugars through chemo-synthesis
• Energy enters ecosystems from the sun through photosynthesis, where CO2 + H2O + Sun is converted to C6H12O6 + H2O + O2
• Gross Primary Productivity (GPP) is the rate at which producers convert solar radiation to sugar molecules
• Net Primary Productivity (NPP) is the energy that remains in plant tissue after cellular respiration, available to consumers
• Heterotrophs break down stored sugars through aerobic respiration, with primary consumers being herbivores, secondary consumers being carnivores, and tertiary consumers being top carnivores
• Decomposers (saprotrophs) feed off dead organic matter in soil, releasing nutrients, and include fungi and bacteria
• Energy transfers through food chains and food webs, with energy transfers being only 10% efficient from one trophic level to another
• Energy transfers are not 100% efficient, with only 10% of the energy at one level making it to the next level (90% lost as heat)
• Pyramid of Energy shows that energy is always lost as you go up the trophic levels, with fewer organisms in the food chain as you go up
• Implications include usually no more than 3-4 levels in a food chain, fewer organisms in the food chain as you go up, and the importance of multiple connections for ecosystem stability
• Food webs show multiple ways energy can move through an ecosystem, with more connections leading to a more stable ecosystem
• Ecologists study the interaction between organisms and their abiotic environment
• Example: Ecologists study how the amount of rainfall in an area impacts the diversity of plants
• Ecology can be split into Population Ecology and Community Ecology
• Population Ecology: study of how and why populations change over time
• Community Ecology: study of how and why populations respond to other members of the ecosystem
• Understanding ecological interactions helps understand the impact of human activities on ecosystem function
• Energy is the ability to do work and is governed by the laws of thermodynamics
• First law: energy cannot be created or destroyed but can change form
• Second law: the amount of energy available in a system decreases over time
• Living systems capture, store, and use energy but cannot create it
• Sunlight is the source of energy for all living systems
• Plants capture sunlight and convert it into sugar through photosynthesis
• Plants are producers, animals are heterotrophs that depend on plants for energy
• Energy flows through ecosystems in one direction and is not recycled
• Energy from the sun is captured by producers and transferred through trophic levels in food chains