Chapter 1: Energy Transfer in the Biosphere PDF

# Chapter 1: Energy Transfer in the Biosphere ## The Study of Ecology - Ecology is the study of relationships between living things (biotic) and their non-living surroundings (abiotic). - "Ecology" is based on a Greek word that means house/home. - German biologist and philosopher Ernst Haeckel coi...

# Chapter 1: Energy Transfer in the Biosphere ## The Study of Ecology - Ecology is the study of relationships between living things (biotic) and their non-living surroundings (abiotic). - "Ecology" is based on a Greek word that means house/home. - German biologist and philosopher Ernst Haeckel coined the term in 1866 to describe people who studied nature and the history of plants and animals. - Today, "Ecology" includes all of the aspects below: - **Nature:** Includes traditional ecological knowledge (TEK), mathematics, and the sciences (biology, physics, chemistry, geology, and numerous sub-disciplines of inquiry such as oceanography, astrobiology, and environmental science) - **Technology:** Includes engineering, metallurgy, resource management techniques, and the tools and products derived from our innovative use of these - **Ecology:** - **Culture:** Includes spirituality, religion, anthropology, sociology, political science, and geography ## Biotic and Abiotic Factors - **Biotic Factors:** Are all of the living components in an ecosystem. - Living organisms, the relationships they are involved in, and the processes they carry out (e.g. photosynthesis, cellular respiration, fermentation, growth, reproduction, parasitism, disease, competition, population density). - **Abiotic Factors:** Are all of the non-living components of an ecosystem. - Examples include temperature, sunlight, water, wind, humidity, rock and soil, salinity, water movement, and pH. ## The Biosphere - Earth's Life System - The biosphere includes all of the areas of Earth that are inhabited by and support life. - Consists of: - **Atmosphere:** Gaseous part of Earth, concentrated mainly within 10 km of Earth's surface, but also extending hundreds of kilometers higher. - Composition: 21% Oxygen, 78% nitrogen, 0.934% argon, 0.036% other gases - **Lithosphere:** (Aka geosphere) - solid, mainly rocky part of Earth. - **Hydrosphere:** All of the earth's water, including surface water, groundwater, and water in the atmosphere. ### Systems in the Biosphere - Systems may be classified into three types: 1. **Open system:** Energy and matter are exchanged between the system and its surroundings (e.g. tree) 2. **Closed system:** Energy is exchanged but matter is not (e.g. Earth-like: heat) 3. **Isolated system:** Matter and energy are not exchanged (e.g. universe). ## 1.1 How Energy Enters the Biosphere - The Earth is essentially a closed system - the Earth absorbs solar energy and thermal energy is radiated from the Earth back into space, but matter is not exchanged. ### The Need For Energy - All organisms need energy to grow, maintain body processes, reproduce, and possibly for movement. - The majority of energy on Earth originates from the Sun. - Producers such as plants, algae, and some bacteria are able to convert energy from the Sun into energy-rich carbohydrates in a process called photosynthesis. - All living things (producers & consumers), convert carbohydrates into useable energy through cellular respiration or, in some cases, fermentation. ### Photosynthesis and Cellular Respiration - **Photosynthesis:** - **Reactants:** Carbon dioxide + water + light energy. - **Products:** Carbohydrates (sugars and starches) + oxygen. - **Cellular Respiration:** - **Reactants:** Carbohydrates (sugars and starches) + oxygen. - **Products:** Carbon dioxide + water + energy. - Although the processes are very different, the overall equations for photosynthesis and cellular respiration are **complementary** (meaning the products of one process are the reactants of the other process). ## Producers = Autotrophs - Producers can produce their own food. - **Photoautotrophs:** Use energy from the Sun to produce chemical energy in the form of carbohydrates. - Examples: green plants, phytoplankton (microscopic marine plants - food for whales, shrimp, jellyfish etc.), some bacteria, and some protists (unicellular eukaryotic organisms). - About 1-2% of incoming solar energy is absorbed by producers on the land and in lakes, rivers, and oceans to be used in photosynthesis. ### Albedo - Albedo = Amount of energy a surface will reflect. - Light coloured surfaces (e.g. snow, ice) and thick cloud cover have a high albedo (80-90%) - hence they reflect solar energy. - Dark surfaces (e.g. forest canopy) and water have low albedos (about 25% or less) hence they absorb solar energy. ## Energy for Life in the Deep Ocean - **Chemoautotrophs** (aka chemosynthetic producers) live near deep-sea vents that release extremely hot water containing hydrogen sulfide. - Solar energy is not able to reach the deep, dark depths... - Bacteria live inside the tissues of tubeworms and carry out a process called chemosynthesis. - Bacteria split organic molecules, such as hydrogen sulfide, to release energy. - **Chemosynthesis Equation:** 6CO2(g) + 6H2O(g) + 3H2S(g) → C6H12O6(S) + 3H2SO4(g) - Carbon dioxide + water + (hydrogen sulfide) → carbohydrates + sulfuric acid (sugars and starches) - Chemosynthetic producers can also be found in soil, hot springs, salty lakes, deep caves (places where there is no solar energy). ### How is chemosynthesis similar to photosynthesis? - CO2 and H2O are reactants in both PS & CS. - Glucose is produced. ### How is chemosynthesis different from photosynthesis? - Sources of energy are different. - No O2 produced in CS. ## Consumers = Heterotrophs - Must consume autotrophs or other heterotrophs for energy. - **Herbivores:** Only consume producers. (e.g. insect, cows) - **Carnivores:** Primarily consume other animals. (e.g. tiger, wolf) - **Omnivores:** Consume both plants and animals. (e.g. bear, human) - **Parasite:** Live on or in a host organism and causes damage to the host. - Consumers can be identified according to what they eat and where they fit in a food chain. ## Decomposers - Obtain energy by digesting then absorbing leftover dead matter and waste (called detritus). (e.g. fungi, bacteria). - They are crucial for returning inorganic matter to the soil, air, and water to be used again by producers. - **Detrivores:** Consume small particles of detritus. (e.g. insects, earthworms). - **Scavengers:** Consume large particles of detritus (e.g. vultures, raccoons). ## Laws of Thermodynamics - **1st Law of Thermodynamics:** Energy cannot be created or destroyed; it can only be converted from one form to another. - **2nd Law of Thermodynamics:** No energy transformation is ever 100% efficient. Most common form of 'wasted' energy = heat - Recall that Earth is a "closed system". ## 1.2 How Energy is Transferred in the Biosphere - Thermal energy is transferred through the biosphere through radiation, conduction and convection. ### Radiation, Conduction, and Convection - **Radiation:** Transmitted as electromagnetic waves that make up the electromagnetic spectrum. - When radiation energy encounters particles of matter, it may be reflected or absorbed. - If the radiation is absorbed, the kinetic energy of the particles will increase, resulting in a temperature increase. - Substances that are at a higher temperature than their surroundings will transfer thermal energy to their surroundings or re-emit energy as heat = IR (infrared radiation). - **Conduction:** The transfer of thermal energy through direct contact between particles of a substance without moving the particles to a new location. - Usually occurs in solids and liquids. - **Convection:** The transfer of thermal energy through the movement of particles from one location to another. - Usually occurs in fluids (i.e. liquids and gases). - During convection, the movement of particles forms a current. ## Trophic Levels - An ecosystem is made up of all the organisms that live in a particular environment and the physical environment (e.g. water, minerals, sunlight) in an area. - Together, the living (biotic) factors) and nonliving (abiotic) factors) components form a self-regulating system through which energy and matter are transferred. - Birth, growth, production, breathing, consumption, movement (immigration, emigration), death and decomposition occur continuously and simultaneously. - A state of dynamic equilibrium exists. - A **trophic level** in an ecosystem is a feeding level at which matter and energy are transferred. - 1st trophic level = **Producers** (photosynthetic/chemosynthetic orgs) - 2nd trophic level = **1°C** (usually herbivores) - 3rd trophic level = **2°C** (secondary) - 4th trophic level = **3°C** (tertiary) - 5th trophic level (if present)= **4°C** (quaternary) - **Decomposers** are consumers that feed at all trophic levels. - There is always less energy available at higher trophic levels, thus **FEWER** organisms at higher levels. ### Rule of 10 - About 10% of the energy available at one trophic level is transferred to the next trophic level. - The remaining 90% of the energy is used within a trophic level for various life processes of the organisms, such as: - Cellular respiration - Reproduction - Growth and repair - Regulation (resp. to env't) - Movement - Metabolism (breathing, digestion, eliminating) - Some of the energy that is not transferred to then next trophic level is "lost" or "wasted" (meaning it is not used directly by the organism) as thermal energy. - SO... ENERGY (and the efficiency of energy transfers) limits the number of organisms that can survive and thrive at each trophic level and limits the number of trophic levels. (Which Law of Thermodynamics does this relate to??) - 2nd law - energy transfer is never 100% efficient. ## Food Chains and Food Webs - A **food chain** is a model that shows the linear pathway through which energy is transferred from one trophic level to another. - A **food web** is a model of energy transfer in an ecosystem that shows the connections among food chains. - Food webs better represent feeding relationships in an ecosystem. - An organism can be at more than one trophic level, depending on which pathway (i.e. food chain) you follow within a food web.