Ecosystems

Introduction Species (be…specific!) –Bear: not good –American Black bear: great –Ursus americanus: amazing Population Community Ecosystem Habitat Niche

All ecosystems have two sets of components. Biotic –Living things –How they interact –Relationships Abiotic –Light –Temperature –Soil –Turbidity –Wind speed –Dissolved oxygen –Slope –Salinity –Flow rate –Elevation –pH –Wave action

How do you measure biotic components? Identify the species –Use a dichotomous key Estimate the abundance of organisms –Percent cover –Percent frequency Estimating biomass –The mass of living material –It’s easiest for plants, but it’s destructive

How do you measure biotic components? We focused mostly on plants. Animals are harder to measure, why? There are some simple ways for smaller organisms. For larger organisms, the Lincoln Index is the easiest way.

Lincoln Index Scientists capture a sample of individuals, mark them, and release them. Scientists then return, capture another sample, and estimate the total population

Calculating Lincoln Index 25 birds caught, tagged, released. 30 birds caught second time, 18 were marked.

Calculating Lincoln Index 8 elephants caught, tagged, released. 9 elephants caught second time, 6 were tagged.

Calculating Lincoln Index 200 ants caught, marked, released. 185 ants caught second time, 57 were marked.

Calculating Lincoln Index 20 blugill caught, tagged, released. 30 bluegill caught second time, 3 were marked.

Lincoln Index Assumptions Population must be closed, no immigration or emigration Time between samples must be small compared to the lifespan Marked organisms must mix with the population after marking

Lincoln Index Setbacks Capture can injure animal Mark/tag may harm animal Mark/tag may be removed Mark/tag may increase/decrease predators Different individuals are more/less “capturable” Individuals may become trap-happy or trap-shy

But it’s not just about HOW MANY living things are in an area. Diversity is very important as well and is a measure of the health of an ecosystem. The lower the diversity, the lower the health. Why do you think this is?

Simpson’s Diversity Index

Ecosystem 1 15 rats 13 squirrels 8 moles 6 mice 5 chipmunks

Ecosystem 2 0 rats 10 squirrels 3 moles 4 mice 25 chipmunks

Ecosystem 3 16 rats 0 squirrels 7 moles 0 mice 32 chipmunks

Ecosystem 4 3 rats 24 squirrels 2 moles 4 mice 5 chipmunks

Ecosystem 5 10 rats 10 squirrels 7 moles 9 mice 0 chipmunks

Ecosystem 6 85 rats 0 squirrels 0 moles 0 mice 0 chipmunks

Ecosystem 7 3 rats 13 squirrels 0 moles 0 mice 5 chipmunks

Ecosystem 8 0 rats 13 squirrels 0 moles 0 mice 22 chipmunks

Ecosystem 9 15 rats 15 squirrels 15 moles 0 mice 9 chipmunks

Pyramid of Numbers Shows the number of organisms at each level. Good for comparing changes Bad because numbers can be too great to represent and difficult for organisms at multiple trophic levels

Pyramid of Biomass Shows the amount of biomass at each level Difficult to measure biomass, biomass varies over seasons

Pyramid of Productivity Shows the amount of energy flow through an ecosystem (rule of 10 - each level is about 10% of the previous level) Good because ecosystems can be compared Bad because the data is hard to get and species can be at multiple trophic levels.

Gross Primary Productivity The amount of energy produced or amount of mass produced by producers

Net Primary Productivity The amount of energy or mass that is stored by producers The amount of energy available to consumers

Gross Secondary Productivity The total amount of energy consumed by consumers

Net Secondary Productivity The total amount of mass gained by (primary) consumers

The data in the table below relate to the transfer of energy in a small clearly defined habitat. The units in each case are in kJ.m -2.yr -1 Net Productivity Calculate the Net Productivity for –Producers –Primary Consumers (Herbivores) –Secondary Consumers (First Carnivores) –Tertiary Consumers (Top Carnivores) Trophic Level Gross Production Respiratory Loss Loss to decomposers Producers Herbivores First Carnivores Top Carnivores 741 Respiratory loss by decomposers 3120

NPP of Producers: ( )=24127 kJ.m -2.yr -1 NSP of Herbivores:21762-( ) =3990 kJ.m -2.yr -1 NSP of Decomposers:( )-3120=472 kJ.m -2.yr -1 Calculations: NSP of Primary Consumers:714-(576+42)=96 kJ.m -2.yr -1 NSP of Secondary Consumers:7-(4+1)=2 kJ.m -2.yr -1

ProducersHerbivores 1st.CarnivoresTopCarnivores Decomposers R= R= R= R=4 1 R=3120 ENERGY FLOW MODEL

Trophic Level Gross Production Respiratory Loss Loss to decomposers Oak Tree Caterpillars Robins Hawks 31 Respiratory loss by decomposers 3120

Trophic Level Gross Production Respiratory Loss Loss to decomposers Phytoplankton Krill Fish Penguins Respiratory loss by decomposers 2792

Measuring abiotic components Marine Ecosystems: –Salinity –pH –Temperature –Dissolved Oxygen –Wave Action

Measuring abiotic components Freshwater ecosystems –Turbidity –Flow Velocity –pH –Temperature –Dissolved Oxygen

Measuring abiotic components Terrestrial ecosystems –Temperature –Light intensity –Wind speed –Slope –Soil moisture –Mineral content

Measuring abiotic components Best method: –Count the organisms Next best method: –Capture-Mark- Release-Recapture –(Lincoln Index)

Population Curves S Curve –Reaches carrying capacity and stabilizes J Curve –Unchecked population growth

Survivorship r- strategists –Short generation time –Mature quickly –Small size –Many offspring –Little parental care Adapted to unstable/ unpredictable environments

Survivorship K- stragetists –Long life/generation time –Mature slowly –Large size –Few offspring –Parental care Predictable/stable environments where population stays near carrying capacity

Population Regulation Density dependent inhibition –Population is regulated by negative feedback –Crowding –Competition

Population Regulation Density independent inhibition –Weather –Disturbances

Succession A natural increase in the complexity of the structure and species composition over time A lifeless area becomes an ecosystem

Bare surface A lifeless abiotic environment becomes available for pioneer species Usually r-selected species

Seral Stage 1 Simple soil starts Pioneer species adapted to extreme conditions colonize

Seral Stage 2 Species diversity increases Organic material and nutrients in soil increases

Seral Stage 3 Larger plants colonize K-selected species become established r-selected species unable to compete get fazed out

Seral Stage 4 Fewer new species Narrower niches develop, K-selected species become specialists

Climax Community Stable and self- perpetuating ecosystem Maximum development under temperature, light, precipitation conditions.

Secondary Succession Soils are already established and ready to accept seeds blown in by the wind

Zonation How an ecosystem changes along an environmental gradient Ex: –Mountain sides –Sea shores –Sea zones