Chapter 54—Ecosystems

Essential questions

• What limits the production in ecosystems?

• How do nutrients move through the ecosystem?

• How are humans disrupting the biosphere?

I. Ecosystem Basics

Ecosystem

• All the organisms in a community plus abiotic factors– ecosystems are transformers of energy

& processors of matter

• Ecosystems are self-sustaining– what is needed?

� energy

� producers

� cycling of nutrients

Energy Transfer/Flow

• Energy in

– from the Sun

– captured by autotrophs =

producers

• Energy through

– food chain

• transfer of energy from autotrophs to heterotrophs(herbivores to carnivores)

• heterotrophs = consumers

Figure 54.1

Energy Transfer

Energy moves through

Nutrientsrecycled

by…

loss of energy

as heat→→→→<20% efficiency

Nutrient Cycling

Decompositionconnects alltrophic levels

II. Primary Production in Ecosytems

• P.P. = Amount of light energy converted to chemical energy (organic compounds) in a given amount of time

• Production by autotrophs sets energy budget for an ecosystem– Marine

• light, temperature & nutrients – depth

– Terrestrial• light, moisture,

temperature– latitude & climate

• Nutrients

• NPP = GPP - R

Primary Production In EcosystemsWhere is productivity highest per meter? Total on Earth?

Figure 54.3

Regional Annual Net Primary Productivity

Mapping chlorophyll density by satellite (g of carbon/m2/year)

Figure 54.4

Ocean = 46%

Land = 54%

What factors

contribute to

productivity?

• Marine systems

– light

– nutrients (nitrogen)

Coast of Long Island, NY

Freshwater Systems

Eutrophication

What factors

contribute to

productivity?

- Light

- Nutrients

(phosphorus)

Too much of a

good thing?

C, N, P

C, N

III. Secondary Production in

Ecosystems

incompletedigestion

metabolism

-Energy Inefficiency

- <17% food → biomass

(caterpillar)

Figure 54.10

- Chemical energy in food that is converted into new biomass in a given

amount of time

Net Secondary Production

- energy stored in biomass

from growth & reproduction

Pyramids of Production

• represent the loss of energy from a food chain

Figure 54.11

Trophic Efficiency

ranges from 5-20%

So, 80-95% of energy

in one trophic level

never transfers to the

next

Pyramid of Numbers

• Size of each block proportional to number of individuals present in each trophic level

Figure 54.13

Implications

• Dynamics of energy through ecosystems have implications for human populations– Which food would be more ecologically sound?

Figure 54.14

IV. Cycling of Chemical Elements

in Ecosystems

Figure 54.15

Water cycle

Figure 54.16 Physical vs. Chemical

Carbon cycle

Figure 54.17Is CO2 entering the atmosphere the same amount leaving it?

Nitrogen cycle

Figure 54.18Size of arrows….

Phosphorus cycle

Figure 54.19 No atmospheric component

V. Human Impact on

Ecosystems & Biosphere

Human population growth is the root of many environmental problems

Acid

Precipitation

Where does the acid precipitation come from?

Acid Precipitation

Sources of Acid Rain Pollutants

�nitrogen oxides

� sulfur dioxide

�power plants

� industry

� transportation

Acid rain

BioMagnification

1947 Time Magazine

• DDT

BioMagnification

• PCBs

CO2

NOx

CH4

Carbon Dioxide

Global Warming

Research

Large-scale experiment on the effect of elevated CO2 levels

Ozone

Depletion

protects from UV rays

Ozone

Depletion

Bad Ozone vs. Good Ozone

Ozone Depletion

• Loss of ozone above Antarctica

DeforestationLoss of Habitat

Loss of Biodiversity

Diversity

• 3 levels of biodiversity

• All decreased by human activity

– genetic diversity

– species diversity

– community/ecosystem

diversity

Extinction

vortexEffects on a small population

Introduced species

• kudzu

kudzu

brown tree snake

gypsy moth

OverexploitationNorth Atlantic bluefin tuna

Fragmented habitat

Biodiversity hot spots

Restoration projects

Think Globally, Act Locally