Ecosystems An Introduction to Energy and Laws of Thermodynamics

Thermodynamics Physical Laws that govern energy relationshipsPhysical Laws that govern energy relationships Ecosystem- the sum of all the organisms living within its boundaries (biotic community) and all the abiotic factors with which they interactEcosystem- the sum of all the organisms living within its boundaries (biotic community) and all the abiotic factors with which they interact Involves Two ProcessesInvolves Two Processes Energy FlowEnergy Flow Note – Energy cannot be recycled therefore there must be a constant supplyNote – Energy cannot be recycled therefore there must be a constant supply Chemical Recycling – Matter can be recycled and Nature does it with perfection.Chemical Recycling – Matter can be recycled and Nature does it with perfection.

The study of energy transformation The study of energy transformation – In short, the law of conservation of energy states that energy can not be created or destroyed, it can only be changed from one form to another or transferred from one body to another, but the total amount of energy remains constant (the same). First law of thermodynamics: Energy can be transferred or transformed but Neither created nor destroyed. For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement in (b). (a) Chemical energy First Law of Thermodynamics Conservation of Energy

In any energy transformation, some energy is lost as unusable energy in the sense that work cannot be performed. This is usually in the form of heat. In any energy transformation, some energy is lost as unusable energy in the sense that work cannot be performed. This is usually in the form of heat. Second law of thermodynamics: Every energy transfer or transformation increases the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s surroundings in the form of heat and the small molecules that are the by-products of metabolism. (b) Heat co 2 H2OH2O + Second Law of Thermodynamics Law of Entropy

Two Important Questions Where does the energy needed for living organisms originate? Where does the energy needed for living organisms originate? How is energy used by these organisms? How is energy used by these organisms?

Flow of energy through life = Metabolism The totality of an organism’s chemical reaction The totality of an organism’s chemical reaction – transforming energy from one form to another organic molecules  ATP & organic molecules sun solar energy  ATP & organic molecules

Living Organisms Temporary storage units for useful energy, whereby one organism can be used by another as a source of energy. Temporary storage units for useful energy, whereby one organism can be used by another as a source of energy.

Metabolism Chemical reactions of life Chemical reactions of life › Anabolic reactions › Forming bonds between molecules › Consume energy › Catabolic reactions › Breaking bonds between molecules › Release energy › Oxidation – Reduction

PHOTOSYNTHESIS 6CO 2 + 6H 2 O + ENERGY C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2 Carbon Dioxide Water Glucose Oxygen CELLULAR RESPIRATION C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2 Carbon Dioxide Water ATP 6CO 2 + 6H 2 O + LIGHT Glucose Oxygen

The Source of High Quality Energy Most of the Energy arrives as electromagnetic radiation from the sun Most of the Energy arrives as electromagnetic radiation from the sun Supports photosynthesis (less than 2%) Supports photosynthesis (less than 2%) Powers the cycling of matter Powers the cycling of matter Drives climate and weather that distribute heat and H 2 O Drives climate and weather that distribute heat and H 2 O Solar radiation Energy in = Energy out Reflected by atmosphere (34%) UV radiation Absorbed by ozone Absorbed by the earth Visible light Lower Stratosphere (ozone layer) Troposphere Heat Greenhouse effect Radiated by atmosphere as heat (66%) Earth Heat radiated by the earth

Chemosynthesis. Chemosynthesis. Chemosynthetic bacteria get energy and raw materials from inorganic sources Chemosynthetic bacteria get energy and raw materials from inorganic sources Oxidize reduced inorganic substances (typically sulfur and ammonia compounds) and produce complex organic compounds. Oxidize reduced inorganic substances (typically sulfur and ammonia compounds) and produce complex organic compounds. Chemoautotrophs Nitrifing bacteria Nitrifing bacteria Halophiles (found in highly concentrated salt lakes) Halophiles (found in highly concentrated salt lakes) Thermophiles (found in hot springs and geysers) Thermophiles (found in hot springs and geysers) complex organic compounds reduced inorganic compounds chemoautotrophs oxygen

Photoautotrophs Autotrophs (=self-nourishing) are called primary producers. Autotrophs (=self-nourishing) are called primary producers. Photoautotrophs fix energy from the sun and store it in complex organic compounds Photoautotrophs fix energy from the sun and store it in complex organic compounds green plants green plants algae algae some bacteria some bacteria some protists some protists photoautotrophs simple inorganic compounds complex organic compounds light

Heterotrophs Heterotrophs (=other-nourishing) cannot produce their own food directly from sunlight+ inorganic compounds. They require energy previously stored in complex molecules. Heterotrophs (=other-nourishing) cannot produce their own food directly from sunlight+ inorganic compounds. They require energy previously stored in complex molecules. Examples of heterotrophs Examples of heterotrophs – Herbivores – eat plants – Carnivores – eat meat – Omnivores – eat both plants and meat – Scavengers – eat carrion – Saprophytes – eat dead or decaying material heterotrophs simple inorganic compounds complex organic compounds this may include several steps, with several different types of organisms heat

Primary Productivity Primary productivity determines the amount of energy available in an ecosystem Primary productivity determines the amount of energy available in an ecosystem Primary productivity is affected mostly by light in aquatic ecosystems Primary productivity is affected mostly by light in aquatic ecosystems Limiting nutrient is phosphorus or nitrogen Limiting nutrient is phosphorus or nitrogen Temperature and moisture are key control factors in terrestrial ecosystems Temperature and moisture are key control factors in terrestrial ecosystems Evapotranspitation Evapotranspitation Water transpiration Water transpiration

Components of Ecosystems Heat Abiotic chemicals (carbon dioxide, oxygen, nitrogen, minerals) Producers(plants)Decomposers (bacteria, fungus) Consumers(herbivores,carnivores) Solar energy Abiotic cycles Abiotic cycles Producers (autotrophs) Producers (autotrophs) – Source of all food Photosynthesis Photosynthesis Chemosynthesis Chemosynthesis Consumers (heterotrophs) Consumers (heterotrophs) Aerobic respiration Aerobic respiration – Oxygen Anaerobic respiration Anaerobic respiration – Methane, H 2 S Decomposers Decomposers – Matter recyclers… – Release organic compounds into soil and water where they can be used by producers

Energy Flow Heat First Trophic Level Second Trophic Level Third Trophic Level Fourth Trophic Level Solar energy Producers (plants) Primary consumers (herbivores) Tertiary consumers (top carnivores) Secondary consumers (carnivores) Detritvores

Trophic Levels – Energy Pyramids An energy pyramid provides a means of describing the feeding and energy relationships within a food chain or web. An energy pyramid provides a means of describing the feeding and energy relationships within a food chain or web. Each organism in an ecosystem is assigned to a feeding (Trophic) level based on source of energy Each organism in an ecosystem is assigned to a feeding (Trophic) level based on source of energy The greatest amount of energy is found at the base of the pyramid. The greatest amount of energy is found at the base of the pyramid. The least amount of energy is found at top of the pyramid The least amount of energy is found at top of the pyramid Producers Primary consumers Secondary consumers Tertiary consumers

Energy Pyramid Each step shows that some energy is stored or utilized in the organism which eats the preceding one. Each step shows that some energy is stored or utilized in the organism which eats the preceding one. Shows that much of the energy is lost when one organism in a food chain eats another. Most of this energy which is lost goes into the environment as heat energy. Shows that much of the energy is lost when one organism in a food chain eats another. Most of this energy which is lost goes into the environment as heat energy. It is estimated that only 10% of the energy at each trophic level is available to organisms at the next higher level. It is estimated that only 10% of the energy at each trophic level is available to organisms at the next higher level.

Implications of Pyramids…. Why could the earth support more people if the eat at lower trophic levels? Why could the earth support more people if the eat at lower trophic levels? Why are food chains and webs rarely more than four or five trophic levels? Why are food chains and webs rarely more than four or five trophic levels? Why are there so few top level carnivores? Why are there so few top level carnivores? Why are these species usually the first to suffer when the the ecosystems that support them are disrupted? Why are these species usually the first to suffer when the the ecosystems that support them are disrupted?

Biomass  Energy is sometimes considered in terms of biomass = the dry weight of tissue of all the organisms and organic material in an area.  Producer organisms represent the greatest amount of living tissue or biomass at the bottom of the pyramid.  Producer organisms represent the greatest amount of living tissue or biomass at the bottom of the pyramid.  There are more plants on Earth than there are animals.  Bio=life Mass=weight  Bio + Mass = Weight of living things within an ecosystem.

Why we transform each species into biomass instead of absolute numbers

Number of observations Number of links in food chain Streams Lakes Terrestrial Average number of links = 3.5

Food Webs A food web is a series of interrelated food chains which provides a more accurate picture of the feeding relationships in an ecosystem More than one thing will usually eat a particular species. A species will many times feed at multiple levels on the trophic pyramid

Generalized Food Web of the Antarctic Humans Blue whaleSperm whale Crabeater seal Killer whale Elephant seal Leopard seal Adélie penguins Petrel Fish Squid Carnivorous plankton Krill Phytoplankton Herbivorous zooplankton Emperor penguin Note: Arrows Go in direction Of energy flow…