Ecosystems and Energy

Ecology: the study of one’s house – - composed of biotic and abiotic components Biotic: living components of the system Abiotic: non-living components of the system – space, temperature, sunlight, soil, wind, precipitiation - incorporates all the sciences and many other areas of study - focus can be limited or large based on the purpose of the study – usually focuses on a specific level of interaction

Tying Ecology Together – movement of energy Energy – ability to do work Types: Chemical Electromagnetic (radiant) Thermal Nuclear Mechanical Electrical Potential Kinetic

Study of Energy = Thermodynamics First Law of Thermodynamics: - the amount of energy in the universe is constant - an organism cannot create energy but must capture the energy from outside itself and then convert it into usable forms

Second Law of Thermodynamics - the amount of energy available to do work decreases over time - ordered systems of energy become disordered by becoming heat - the amount of disorder is measured as Entropy - theoretically all the energy in the universe will eventually be evenly distributed as heat and no work will be done (Heat Death of the Universe) - thus no transformation of energy is 100% efficient Ex: Car engine 20 – 30% efficient at converting chemical energy in the bonds of gasoline into mechanical energy – rest is lost as heat - Human metabolism – 40 % efficient

Energy Exchange in the Ecosystem Photosynthesis and Cellular Respiration Photosynthesis: process of capturing photons (light energy) and using them to fix carbon dioxide into simple sugars 6 CO2 + 6 H2O  C6H12O6 + 6 O2

Photon capture is done by a system of proteins called pigments main pigment is chlorophyll, which appears green because it reflects green light and best absorbs red and blue light - chlorophyll is found in the chloroplast of plant cells Organisms: Plants, algae, some protists, cyanobacteria (blue-green algae) Process: CO2 is fixed to several organic molecules in order to form it into glucose, uses the ATP for energy Glucose is used for energy for growth and reproduction – extra glucose is stored as starch By products are Oxygen

Cellular Respiration process of breaking down organic molecules into CO2 and energy – - reverse of photosynthesis – C6H12O6 + 6 O2  6 CO2 + 6 H2O Glucose is broken down through a series of steps to ensure the slow release of the energy – slow release makes the process more energy efficient – carried out mainly by the mitochondria

Process: Organisms: All eukaryotes (Plants, animals, fungus, most protists) In the end - CO2 that was fixed by the photosynthesis is released by the cellular respiration, which also consumes the O2 that was generated together they form the base process for the carbon cycle However, the energy that is captured by the phototrophs is not transferred to the heterotrophs completely. Much of it is lost as heat and through biological processes.

Energy Flow Through Ecosytems Terms: Producers/Autotrophs (self-feeders) – initial organisms that capture and store energy Types: Photoautotrophs – capture solar energy and convert it to chemical energy Ex: plants and algae- some bacteria and protists Chemoautotrophs – use the energy in other chemicals to build biological molecules Ex: deep sea vent bacteria

Consumers/Heterotrophs (other feeders): must consume biological molecules for a source of energy – cannot make their own food Types: Carnivores: meat eaters - cats Herbivores: plant eaters - cows Omnivores: any eaters – bears Decomposers/Saprotrophes (rotten eaters): Detrivores/Saprobes: break down dead things – fungus and bacteria

Microorganisms and other detritivores Detritus Primary producers Primary consumers Secondary consumers Tertiary consumers Heat Sun Key Chemical cycling Energy flow

Trophic Levels 1. Primary Producers - autotrophs 2. Primary Consumers – herbivores 3. Secondary Consumers – carnivores – herbivore eaters 4. Tertiary Consumers – carnivores – eaters of other carnivores

5. Keystone Predator – top of the food chain – presence helps regulate the populations of the lower trophic levels Ex: lions, wolves removal of the keystone predator often causes a large disruption in the lower trophic levels – removal of wolves from the United States causes a large upsurge of deer populations which in turn ate more and more plants making them less available for the other species

Number of species present (a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates. With Pisaster (control) Without Pisaster (experimental) Number of species present 5 10 15 20 1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73 (b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.

Observation of sea otter populations and their predation Figure 53.17 Food chain before killer whale involve- ment in chain (a) Sea otter abundance (b) Sea urchin biomass (c) Total kelp density Number per 0.25 m2 1972 1985 1989 1993 1997 2 4 6 8 10 100 200 300 400 Grams per 0.25 m2 Otter number (% max. count) 40 20 60 80 Year Food chain after killer whales started preying on otters

6. Detrivores – complete the cycle of nutrients - break things down which make nutrients available for the producers - Together these make up a food chain (page 54) (consumer to decomposer) which more accurately portrayed as a food web (page 55).

Ecosystem “Engineers” (Foundation Species) Some organisms exert their influence By causing physical changes in the environment that affect community structure

Beaver dams can transform landscapes on a very large scale Figure 53.18

Ecological Pyramids Biomass and Energy Transfer Between Trophic Levels Producers: Trap and convert energy into usable forms Producers use this energy for life functions (growth, repair, reproduction) which decreases the amount of energy that is available to the next level Same is true for each consumer level Result: As you move up in levels, the number of organisms, the overall biomass and the amount of energy decreases.

Types of Pyramids 1. Pyramid of Numbers: Figure 3.11 - typically, the organisms at the base of the food chain are most abundant

Biomagnification

Types of Pyramids 2. Pyramids of Biomass: Figure 3.12 - Biomass: amount of biological material – indicates the amount of fixed energy in an organism or system - Average is about 90% decrease - only 10% is passed to the next trophic level

Pyramid of Biomass Trophic level Dry weight (g/m2) Tertiary consumers Figure 54.12a (a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as illustrated by data from a bog at Silver Springs, Florida. Trophic level Dry weight (g/m2) Primary producers Tertiary consumers Secondary consumers Primary consumers 1.5 11 37 809

Certain aquatic ecosystems have inverted biomass pyramids Trophic level Primary producers (phytoplankton) Primary consumers (zooplankton) Dry weight (g/m2) 21 4

Types of Pyramids 3. Pyramid of Energy: Figure 3.13 - expressed as kilocalories per square meter - since the producers are most abundant they will contain the most energy per square meter, but not per organism

Pyramid of Energy Figure 54.11 Tertiary consumers Secondary Primary producers 1,000,000 J of sunlight 10 J 100 J 1,000 J 10,000 J

Ecological Pyramids allow us to look at an ecosystem and determine its productivity Ecosystem Productivity: Gross Primary Productivity (GPP) is the rate at which energy is captured during photosynthesis Net Primary Productivity (NPP) is the amount of energy left over after the producers have used the amount they need for life functions - measured by the kilocalories per square meter per year or the grams of biomass (dry weight of CO2) incorporated per square meter per year

Consumers eat the producers and the NPP becomes available for use (not all – depends on the efficiency of the consumers digestive system) Consumer uses the energy for basic life functions (movement, tissue repair) and the remaining energy (Secondary Productivity) can be used for growth and reproduction

Worldwide agriculture could successfully feed many more people if humans all fed more efficiently, eating only plant material Trophic level Secondary consumers Primary producers