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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 • http://www.youtube.com/watch?v=VK9v3ioiYBU
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
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? • 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 Potential energy Kinetic energy
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 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 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 • grassrabbitsnakeeagle • 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 • 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/oceanphotosynthesiscellular respiration/combustion/decompositionatmosphere/ocean • Carbon is an essential component of organisms’ molecules • Also essential component of abiotic environment
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 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 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
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: • 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: • 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 • 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
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 • Competition • 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
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
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