Environment in the News
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chapter_5.pptHow 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
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Lake Victoria’s Ecological Imbalance
What is Ecology?
- Learning Objectives:
Define ecology
Distinguish among the following ecological levels: population, community, ecosystem, landscape, and biosphere
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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
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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
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What is Ecology?
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- 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?
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What is Ecology?
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- 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
What is Ecology?
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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
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The Flow of Energy Through Ecosystems
- Energy: the ability to do work
- Potential energy: stored
- Kinetic Energy: energy of motion
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The Flow of Energy Through Ecosystems
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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
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The Flow of Energy Through Ecosystems
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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
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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
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The Flow of Energy Through Ecosystems
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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
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The Flow of Energy Through Ecosystems
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The Flow of Energy Through Ecosystems
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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
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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?
- Learning Objectives:
Diagram and explain the carbon, hydrologic, nitrogen, sulfur, and phosphorous cycles
The Cycling of Matter in Ecosystems
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- 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
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- 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
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The Cycling of Matter in Ecosystems
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- 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
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The Cycling of Matter in Ecosystems
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- 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
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The Cycling of Matter in Ecosystems
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The Cycling of Matter in Ecosystems
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- 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
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The Cycling of Matter in Ecosystems
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- 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
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The Cycling of Matter in Ecosystems
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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
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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
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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
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Ecological Niches
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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
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What a Scientist Sees
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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
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Interactions Among Organisms
- Organisms are not independent from others
- Symbiosis
- Predation
- Competiton
- Keystone Species - a special case
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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
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Interactions Among Organisms
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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
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EnviroDiscovery
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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
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Environmental InSight
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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
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Interactions Among Organisms
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Interactions Among Organisms
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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
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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
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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?
- 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
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Case Study
