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

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

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

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.

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