How Ecosystems Work Chapter 5

Lake Victoria’s Ecological Imbalance World’s second largest freshwater lake 400 species of cichlids, important food source Nile Perch introduced in 1960s 1985, most catch was perch, ate cichlids Today, more than 50% of cichlids and other native fish are extinct Algae eating cichlids disappeared, algal explosion, no Oxygen in bottom of lake dead zone If the rest of cichlids disappear, perch won’t have anything to eat, and fisher will collapse

Lake Victoria’s Ecological Imbalance

What is Ecology? Learning Objectives: Define ecology Distinguish among the following ecological levels: population, community, ecosystem, landscape, and biosphere

What is Ecology? The study of the interactions among organisms and between organisms and their abiotic environment Environment: Biotic (living) - all organisms Abiotic (non-living) - physical factors: space, temperature, sunlight, soil, precipitation, etc. Focus can be local or global Broadest field of Biology Linked to all parts of biology, and to geology, chemistry, physics

What is Ecology? Levels of Interest: Population: a group of organisms of the same species that live in the same place at the same time, e.g., population of marsh grass, walruses Communities: a natural association that consists of all the populations of different species that live and interact together within an area at the same time, e.g., Alpine meadow, tidal pool Ecologists would study how species interact with each other, including feeding relationships 6

What is Ecology?

What is Ecology? Ecosystem: includes all the biological interactions of a community AND the interactions of organisms with their abiotic environment Very complex interactions between energy flow and nutrient cycling Ecologists would study how energy, nutrients, or water level affects the organisms living in a desert Landscape: studies ecological processes over large areas and several interacting ecosystems

What is Ecology?

What is Ecology? Biosphere: the layer of Earth that contains all living organisms Ecologists study the global interrelationships among water, land, atmosphere, and organisms Includes organisms, communities, ecosystems, landscapes, etc. depend on the Earth’s other layers: Atmosphere: layer of air Hydrosphere: supply of water Lithosphere: soil and rock of Earth’s crust

Global Climate Change What is the definition of ecology? What is the difference between an ecosystem and a landscape? Between a community and an ecosystem?

The Flow of Energy Through Ecosystems Learning Objectives Define energy and state the first and second laws of thermodynamics Distinguish among producers, consumers, and decomposers Summarize how energy flows through an ecosystem

The Flow of Energy Through Ecosystems Energy: the ability to do work Potential energy: stored Kinetic Energy: energy of motion

The Flow of Energy Through Ecosystems

The Flow of Energy Through Ecosystems Thermodynamics: study of energy and its transformations First Law of Thermodynamics Energy cannot be created not destroyed Can change from one form to another Photosynthesis/cellular respiration Heat - not usable for biological work Total energy of organisms and surroundings is constant

The Flow of Energy Through Ecosystems

The Flow of Energy Through Ecosystems The Second Law of Thermodynamics The amount of usable energy in the universe decreases over time As energy is converted form one form to another, some of it is degraded into ‘heat’ Heat: less usable form of energy, disperses into environment, less organized than usable energy Entropy: a measure of disorder or randomness Energy conversions are is not 100% efficient

The Flow of Energy Through Ecosystems Producers, Consumers and Decomposers Producers: manufacture large organic molecules from simple inorganic molecules Consumers: consume other organisms as a source of energy and bodybuilding materials Primary Consumers/Herbivores: eat producers Secondary Consumers/Carnivores: eat primary consumers Tertiary Consumers/Carnivores: eat secondary consumers Omnivores: eat everything Detritivores/Detritus feeders: eat detritus (animal carcasses, leaf litter, feces) Decomposers: break down dead organisms and waste products Release simple inorganic molecules that can be re-used by producers

The Flow of Energy Through Ecosystems

The Flow of Energy Through Ecosystems The Path of Energy Flow in Ecosystems Energy Flow The passage of energy in a one-way direction through an ecosystem, as part of a food chain Food Chain A diagram showing linear feeding relationships grassrabbitsnakeeagle Trophic level: each link in a food chain First trophic level: producers Second: primary consumers Third: secondary consumers, etc. Decomposers are at every step Food Web A complex of interconnected food webs in an ecosystem

The Flow of Energy Through Ecosystems

The Flow of Energy Through Ecosystems

The Flow of Energy Through Ecosystems Energy Flow Linear movement of energy along food chain or food web From one organism to the next When ‘food’ energy is converted into ‘work’ energy, some is degraded into heat Second Law of thermodynamics The longer the food chain, the less energy is available for higher trophic levels Limited numbers of trophic levels

Global Climate Change What is the first law of thermodynamics? What is the second? Why is a balanced ecosystem unlikely to contain only producers and consumers? Only consumers and decomposers? Explain your answer. How does energy mover through a food web?

The Cycling of Matter in Ecosystems Learning Objectives: Diagram and explain the carbon, hydrologic, nitrogen, sulfur, and phosphorous cycles

The Cycling of Matter in Ecosystems Biogeochemical Cycles Matter: the material of which organisms are composed Biogeochemical: involves biological, geological, and chemical processes Humans have GREAT influence Cycling vs. Flow: Matter cycles through ecosystem From abiotic environment to organisms to environment Energy flows through the ecosystem From producers to consumers to decomposers, to heat

The Cycling of Matter in Ecosystems The Carbon Cycle The global movement of carbon between the abiotic environment (atmosphere, ocean) and organisms Atmosphere/oceanphotosynthesiscellular respiration/combustion/decompositionatmosphere/ocean Carbon is an essential component of organisms’ molecules Also essential component of abiotic environment

The Cycling of Matter in Ecosystems

The Cycling of Matter in Ecosystems The Hydrologic Cycle Water circulates from the ocean to the atmosphere to the land, and back to the ocean Provides renewable supply of purified water Balance of water on land, oceans, and atmosphere Evaporation Transpiration Precipitation Runoff from watersheds Percolation

The Cycling of Matter in Ecosystems

The Cycling of Matter in Ecosystems The Nitrogen Cycle Nitrogen is an essential component of proteins and nucleic acids Atmosphere is 78% Nitrogen gas Steps: Nitrogen fixation: N gas into ammonia, by bacteria physical, and human activities Nitrification: ammonia to nitrate, bacteria Assimilation: plants absorb nitrate/ammonia Ammonification: organisms produce N-containing waste Denitrification: nitrate is converted back into N gas

The Cycling of Matter in Ecosystems

The Cycling of Matter in Ecosystems

The Cycling of Matter in Ecosystems The Sulfur Cycle Poorly understood Most Sulfur is underground Erosion releases Sulfur to ocean S gases enter atmosphere from natural sources Sea delivers sulfates to land Volcanoes release Hydrogen sulfides and Sulfur oxides Hydrogen sulfides react with water to form sulfuric acid Some sulfur compounds in living organisms Bacteria drive the Sulfur cycle (like the Nitrogen cycle)

The Cycling of Matter in Ecosystems

The Cycling of Matter in Ecosystems The Phosphorous Cycle Cycles from land into living organisms and back No atmospheric component Erosion of rocks releases phosphorous into soil Plants absorb it and use it for nucleic acids and ATP, pass it on to consumers Decomposers release phosphorous into water Can be lost at bottom of ocean fro millions of years Aquatic cycle is also interesting

The Cycling of Matter in Ecosystems

Global Climate Change What are the differences and similarities between the five biogeochemical cycles, particularly in the roles organisms play in them?

Ecological Niches Learning Objectives: Describe the factors that contribute to an organism’s ecological niche Explain the concept of resource partitioning

Ecological Niches Niche: Habitat: The totality of an organism’s adaptations, its use of resources, and the lifestyle to which it is fitted Describes the place and function of an organism within the ecosystem Takes into account all aspects of an organism’s existence The “way of life of an organism” Habitat: Part of an organism’s niche, the place where the organism lives

Ecological Niches Fundamental Niche: Realized Niche: The potential, idealized niche of an organism It’s probably broader than it is in nature Realized Niche: The niche an organism actually has and the resources it actually uses Competition and other factors usually make the realized niche narrower than the fundamental niche

Ecological Niches

Ecological Niches Resource Partitioning The reduction in competition for environmental resources among coexisting species, by reducing similarities in their niches When two species are very similar, their niches may overlap Ecologists think that species cannot occupy the same niche in a community Species with similar niches divide up resources in such a way that they reduce competition among themselves

What a Scientist Sees

Global Climate Change What are three aspects of an organism’s ecological niche? What is resource partitioning?

Interactions Among Organisms Learning Objectives: Distinguish among mutualism, commensalism, and parasitism Define predation and describe predator-prey relationships Define competition and distinguish between intraspecific and interspecific competition Discuss an example of keystone species

Interactions Among Organisms Organisms are not independent from others Symbiosis Predation Competiton Keystone Species - a special case

Interactions Among Organisms Symbiosis An intimate relationship or association between members of two or more species One species lives in or on another species Relationship may be beneficial, neutral or harmful Result of coevolution Interdependent evolution of two interacting species E.g., plants and pollinators

Interactions Among Organisms

EnviroDiscovery Bee Colonies Under Threat Coevolutionary relationships are very specific If one species is affected suffers, so is the other Colony Collapse Disorder (CCD) Since 2006, 30–90% of bees in colonies in US have died Pesticides, pathogens, parasites, viruses Bees are necessary for pollination of many important crops and wild species

EnviroDiscovery

Interactions Among Organisms Symbiosis Three types: Mutualism An association where both organisms benefit Bull Horn Acacia and acacia ants Commensalism One species benefits, the other doesn’t benefit or is harmed Tropical trees and epiphytes Parasitism One species benefits, the other is harmed Parasite-Host relationship Internal and external types of parasites

Environmental InSight

Interactions Among Organisms Predation The consumption of one species (prey) by another species (predator) Coevolutionary “arms race” Predator strategies - more efficient ways to catch prey Prey strategies - more efficient ways to escape/avoid predator

Interactions Among Organisms

Interactions Among Organisms

Interactions Among Organisms Competition The interaction among organisms that vie for the same resources in the same environment Resources are limited Food, shelter, living space, sunlight, etc. Intraspecific Competition Among individuals of the same population (same species) Interspecific Competition Among individuals of different species

Interactions Among Organisms Keystone Species Vital in determining an ecosystem’s species composition Crucial to the maintenance of an ecosystem When keystone species is removed other organisms may become more common, more rare, or extinct Usually not numerous, but very influential Affect availability of food, water, or other resources E.g., Gray Wolf

Global Climate Change What is one example if mutualism? Of parasitism? What is one example of a predator-prey interaction? Or competition? What is the difference between interspecific and intraspecific competition? How does a keystone species affect its ecosystem?

Case Study Global Climate Change: How does it affect the Carbon cycle? Biggest culprit: levels of CO2 in atmosphere Levels of CO2 have increased 20% in last 50yrs Generated by burning of fossil fuels, clearing and burning land and forests Need to stabilize and reduce emissions with ‘stabilization wedges”, each reduces 1 billion tons/yr

Case Study