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