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Ecology, Ecosystems,Ecology, Ecosystems,& Food Webs& Food Webs
Chapter 16Chapter 16
© Brooks/Cole Publishing Company / ITP
What is Ecology? What is Ecology? study of relationships between organisms & their environment. Levels of organization:
– biosphere- biotic (living) & abiotic factors (non-living)– ecosystem: community + non–living environment– community: populations of different species in given area– population: a group of interacting individuals of same
species– organism (individuals): any form of life
Organisms (Individuals)Organisms (Individuals) organisms are classified into species. species: groups of organisms that resemble each
other, and in cases of sexually reproducing organisms, can potentially interbreed.
estimates of 5 to 100 million species, most are insects & microorganisms; so far only about 1.8 million named; each species is the result of long evolutionary history.
wild or native species: population that exists in its natural habitat .
domesticated or introduced species: population introduced by humans (= non–native species).
PopulationsPopulations population: a group of individuals of the
same species. examples: sunfish in a pond, white oak trees
in a forest, people in a city; habitat: the place where a population
usually lives. genetic diversity: in natural populations
individuals vary in their genetic makeup. Ex: blue eyes vs. green eyes
CommunitiesCommunities community: populations of different
species living together in a given area.– a biological community is a complex
interacting network of plants, animals and microorganisms.
– example: redwood forest community, consisting of populations of redwoods & other trees, shrubs and herbaceous species, animals and microorganisms.
EcosystemsEcosystems ecosystem: communities & the non–
living parts of the environment. example: Ducks, fish, and insect larvae living
in/on a lake or pond.
What is an ecosystem?Ecosystem is a system of living
things that interact with each other and with the physical world.
A Biome is a collection of related ecosystems.
Main Ecosystems:
Desert Rainforest Ocean Taiga
Tundra Chaparral Grassland Temperate
Forrest
Green:Grassland Purple: Taiga Orange:Tundra Black:Temperate Forrest Yellow:Desert
Brown:Chapparal White:Ocean
However……..
An ecosystem can be as large as the Sahara Desert, or as small as a puddle!!!
Ecosystems are more than just the organisms they contain. Geography, weather, climate and geologic factors also influence the interactions within an ecosystem.
Biodiversity
Bio What?
Biodiversity is the variety of all life forms: the different plants, animals and micro-organisms, their genes and the ecosystems of which they are a part.
Biodiversity Continued
Genetic diversity-the total genetic information contained in the genes of all species.
Species Diversity-The variety of species, refers to the number of species and the number of individuals in a species.
Ecosystem Diversity- the variety of habitats natural communities and ecological processes.
Importance Of biodiversity
Humans are dependent on biodiversity for their sustenance, health, well-being and enjoyment of life.
Food- we rely on biodiversity to provide us with a large and varied food source
Health- Humanity derives many of it’s medicines from biodiversity.
Threats to biodiversity Habitat loss and fragmentation Competition from invasive species Pollution Global climate change Desertification Population growth and over consumption Unsustainable use of natural resources.
Simple ecosystem model
Key Attributes:
Biotic and abiotic processes
Ecosystem Boundaries How do we decide where to draw the lines
around an ecosystem? Depends on the scale of the question being
asked– Small scale: e.g., soil core; appropriate for
studying microbial interactions with the soil environment, microbial nutrient transformations
– Stand: an area of sufficient homogeneity with regard to vegetation, soils, topography, microclimate, and past disturbance history to be treated as a single unit; appropriate questions include impact of forest management on nutrient cycling, effects of acid deposition on forest growth
Ecosystem BoundariesNatural Boundaries: ecosystems sometimes are bounded by naturally delineated borders (lawn, crop field, lake); appropriate questions include whole-lake trophic dynamics and energy fluxes (e.g., Lindeman 1942)
Watershed: a stream and all the terrestrial surface that drains into it
rich history of watershed scale studies in ecosystem ecology (“Small Watershed Approach” e.g. Bormann and Likens 1967)
watershed studies use streams as ‘sampling device’, recording surface exports of water, nutrients, carbon, pollutants, etc., from the watershed; deforestation impacts on water supply to a city.
Succession
Ecological succession, the series of changes in an ecological community that occur over time after a disturbance. It can be:
Primary Succession Secondary Succession
Primary Succession
Where plants have not grown before.
Secondary Succession
Area where there has been previous growth.
Succession and Wildlife
What Sustains Life?What Sustains Life? Energy From Sun
– one–way flow of usable energy from sun through feeding interactions heat
Cycling of Matter– the continual flow of matter between the
nonliving environment & living organisms (biogeochemical cycles)
Gravity– enables Earth to hold its atmosphere gases;
causes downward movement of matter in nutrient cycles.
What Sustains Life?What Sustains Life? Energy From Sun
– one–way flow of usable energy from sun through feeding interactions heat
Cycling of Matter– the continual flow of matter between the
nonliving environment & living organisms (biogeochemical cycles)
Gravity– enables Earth to hold its atmosphere gases;
causes downward movement of matter in nutrient cycles.
Energy Flow & Nutrient Energy Flow & Nutrient CyclingCycling
Life on Earth depends upon one–way flow of high–quality energy from sun & cycling of crucial elements.
Energy FlowEnergy FlowThe ultimate source of energy in most ecosystems is the sun.
Nutrient CyclesNutrient Cycles nutrient: any atom, ion, or molecule an organism
needs to live, grow, or reproduce.– macronutrients needed in relatively large
amounts e.g., C, O, H, N, P, S, K, Ca, Mg, Fe
– micronutrients needed in relatively small amounts e.g., Na, Zn, Cu, Cl,
– nutrient cycles (= biogeochemical cycles) involve continual flow of nutrients from nonliving (air, water, soil, rock) to living organisms (biota) & back again.
– nutrient cycles driven directly or indirectly by solar radiation & gravity.
– Major cycles: hydrologic (water), carbon, oxygen, nitrogen, phosphorus and sulfur.
Vocabulary for Vocabulary for EcosystemsEcosystems
Abiotic: non–living components. Ex: water, air,sun
Biotic: living components Ex: plants, animals, bacteria
Trophic level- feeding level for an organism
Major components of aquatic ecosystems.
Major components of terrestrial ecosystems.
Key Players in Key Players in EcosystemsEcosystems
Autotrophs/ producers: make their own food via photosynthesis (plants) or chemosynthesis (bacteria in thermal vents use hydrogen sulfide (H2S) & carbon dioxide)
Heterotrophs/ consumers: can’t make their own food, feed on other organisms or their remains.
– Ex: herbivores, carnivores, decomposers, etc.
Key Energy ProcessesKey Energy Processes Photosynthesis: use of chlorophyll. Energy
storing process.– 6 CO2 + 6 H2O + solar energy C6H12O6 + 6 O2
Cellular Respiration:– Aerobic Respiration: energy releasing process.– C6H12O6 + 6 O2 6CO2 + 6 H2O + energy (ATP)
Anaerobic Respiration – Ex. Fermentation: energy releasing process used by
yeast and bacteria
Categories of ConsumersCategories of Consumers primary consumers: (=herbivores) feed directly on
producers; secondary consumers: (=carnivores) feed on primary
consumers; tertiary consumers: feed only on carnivores; omnivores: consumers that feed on both plants &
animals; scavengers: feed on dead organisms; decomposers (saprobes): consumers that complete the
breakdown & recycling of organic materials from the remains & wastes of other organisms;
detritivores: feed on detritus (partially decomposed organic matter, such as leaf litter & animal dung).
The Importance of DecomposersThe Importance of Decomposers
Fig. 4–16
Summary of Ecosystem StructureSummary of Ecosystem Structure
Fig. 4–17
Food ChainsFood ChainsFood chains are a simple food path involving a sequence of organisms, each of which is the food for the next.
Fig. 4–18
Food Webs Food webs are multiple food chains that are interconnected. More complex than food chains.
Ecological Pyramids Represent the flow of energy through an
ecosystem. Typically each trophic level has a certain
amount of BIOMASS (dry weight of organic matter)
Ecological efficiency- amount of usable energy transferred as biomass. Usually 10% at each transfer.
Food chains and webs only have 4-5 trophic levels, because too little energy left to support top consumers.
Energy PyramidEnergy Pyramid
Fig. 4–19
In nature, ecological efficiency varies from 5% to 20% energy available between successive trophic levels (95% to 80% loss). About 10% efficiency is a general rule.
Another Energy PyramidAnother Energy Pyramid
Fig. 4–21
Annual pyramid of energy flow (in kilocalories per square meter per year) for an aquatic ecosystem in Silver Springs, FL.
Note: More individuals can be supported at lower trophic levels. Less energy is lost.
Biomass PyramidsBiomass PyramidsDisplays the biomass at each trophic level.
Pyramid of Numbers
Pyramid of numbers displays the number of individuals
at each level.
1 owl
25 voles
2000grass plants
Primary Productivity of Ecosytems
1.Gross primary productivity (GPP) is the rate at which an ecosystem's producers convert solar energy into chemical energy as biomass.
2. Net primary productivity (NPP) is the rate at which energy for use by consumers is stored in new biomass.
NPP = GPP – R [rate at which producers use biomass]
Net Primary ProductivityNet Primary ProductivityEstimated annual net primary productivity of major biomes & aquatic life zones, expressed as kilocalories per square meter per year.
Fig. 4–24