Ecosystems

Feeding level vocab

Producers are the autotrophs of an environment Mostly by photosynthesis

Consumers are the heterotrophs of the environment. They can be… Herbivores- which eat producers Carnivores- which eat other consumers Omnivores- which eat producers and

consumers

Feeding level vocab

Primary consumer - eats producer Secondary consumer - eats primary

consumer Tertiary consumer - eats primary or

secondary consumers Detritivores - (Decomposers) - Break down

complex molecules in dead organic matter into smaller molecules They are responsible for recycling many

nutrients into the soil

Food Chain (review)

A straight-line

sequence of who

eats whom

Simple food chains

are rare in nature

marsh hawk

upland sandpiper

garter snake

cutworm

plants

Tall-Grass Prairie Food Web (review)

earthworms, insects

sparrow

vole pocketgopher

groundsquirrel

coyotebadgerweasel

spider

frog

snake

sandpiper crow

marsh hawk

grasses, composites

Ecosystems

An ecosystem is all of the organisms in an area, along with their nonliving environmentExample: aquariumLiving + Non-living(Biotic + Abiotic)Focus

• Energy flow• Matter cycling

Trophic Levels

Organisms in a community are related to each other through feeding relationships

Each step up in the transfer of energy is known as a trophic level

All energy ultimately comes from the SUN

Energy transfer

An important principle in trophic levels is the 2nd Law of ThermodynamicsEnergy conversions cannot be

completely efficientEach transfer only utilizes about 10%

of the energy

Trophic Levels

REVIEWThe trophic level that supports all

other trophic levels are the primary producers (autotrophs)

These are followed by primary consumers, secondary consumers, etc

Trophic levels correlate to food webs

Trophic Levels

Decomposers/Detritivores Eat detritus (organic

waste/remains of dead organisms)

Can fit in to a food chain or web at any location

Trophic Levels

Producers Convert solar (or chemical)

energy into organic compounds

Primary consumers Eat producers

Secondary consumers Eat primary consumers

Tertiary consumers Eat secondary consumers

Decomposers Recycle nutrients

Energy Efficiency in Ecosystems

Primary production

Just like Congress, an ecosystem also has a budget

The energy budget for an ecosystem is equal to the amount of light energy that is converted to chemical energy (photosynthesis) in a given time periodThis is called the ecosystem’s primary

production The amount of energy in an ecosystem is

derived from this primary production

Global Energy Budget

Each day, the Earth is exposed to about 1022 joules of solar radiationThis is enough energy to supply the

needs of the entire human population for about 25 years

The problem: only a small fraction of that energy is used by plants in photosynthesis

• Most sunlight falls on bare ground or is absorbed or reflected by the oceans

Ecosystem (Net energy)

Primary Productivity:The amount of light energy converted to

sugars by autotrophs in an ecosystemGross vs. Net Primary Productivity

• GPP: the amount of light energy that is converted to chemical energy by photosynthesis per unit time

• NPP: GPP minus the energy used by the primary producers for cellular respiration (R)

NPP = GPP - R

Net primary production

Ecologists are mainly concerned with the net primary production (NPP)This allows them to look at the amount

of energy that is available for the ecosystem• The ecosystem’s actual energy

budget The next slide shows how the Earth’s

energy is distributed

Factors affecting NPP In aquatic (marine and freshwater) ecosystems, 2

factors play a key role Light limitation

• The depth of light penetration• Other factors that limit light exposure

Nutrient limitation• Limiting nutrients can prevent autotrophs

from producing chemical energy (poor soil or other factors that limit growth)

• Eutrophication• Water availability

Eutrification

In lakes, when you have a significant runoff of sewage or fertilizers, you stimulate the growth of cyanobacteria

End result, you use up most of the dissolved O2 in the lake and kills most organisms

Energy transfers and biomass We’ve already discussed that energy

transfer between trophic levels are inefficientA lot of energy is used to maintain the

organism (metabolism and cellular respiration)and cannot be transferred

Additionally, all of these transfers do not transfer ALL available energy• A lot is lost due to heat

Production efficiency

Because, not all of the available energy is utilized, we can use production efficiency to measure the amount of energy that is actually usedREMINDER: Measuring energy use

(through metabolism, O2 usage, CO2 production, heat production, etc)

Production efficiency = Amount of energy utilized

Primary production

Trophic Levels (10% efficiency) Ten-Percent Law

Usable energy is lost through each transfer of energy

• Why? (Remember the law of conservation of energy says energy cannot be created or destroyed; it only changes form.)

Only about 10% of the energy at one trophic level is transferred to the next trophic level. 90% is lost with each transfer.

Biomass

Another way to look at efficiency is to look at biomass (the total DRY mass of organisms at each trophic level)

Instead of looking at the energy production, the biomass is examined

Pyramid of Numbers/Biomass/Energy Numbers, energy,

& biomass decreases as one moves up the food chain.

Biomass- dry mass of organic matter

Green World Hypothesis

With so many primary consumers feeding on plants, why do we still have so many plants?Why aren’t the plants extinct?

One explanation is the Green world hypothesis

Green world hypothesis Plants have defenses against herbivores Nutrients, not energy supply, usually limit

herbivores (amount of organic material in ecosystem)

Abiotic factors limit herbivores (climate) Intraspecific competition (territoriality) Interspecific competition (predators,

parasites, disease)

Geochemical cycles

Limiting Nutrients

What limits primary production?Aquatic Ecosystems

• Light (depth penetration)• Nitrogen• Phosphorus

Terrestrial Ecosystems• Temperature• Moisture• Minerals (nitrogen & phosphorus are the main

limiting factors for plants.)

Biogeochemical Cycle

The flow of a nutrient from the

environment to living organisms and back

to the environment

Main reservoir for the nutrient is in the

environment

Water Cycle

Atmosphere

Ocean Land

evaporation from ocean

425,000

precipitation into ocean 385,000

evaporation from land plants (evapotranspiration)

71,000

precipitation onto land 111,000

wind-driven water vapor40,000

surface and groundwater flow 40,000

Figure 48.14Page 876

Rain Shadow Air rises on the windward side, loses moisture

before passing over the mountain

Leeward side is in the rainshadow; deserts

Figure 49.7Page 893

Figure 48.16 Page 878

diffusion between atmosphere and ocean

bicarbonate and carbonate in ocean water

marine food webs

marine sediments

combustion of fossil fuels

incorporation into sediments

death, sedimentation uplifting

sedimentation

photosynthesis aerobic respiration

Carbon Cycle - Marine

Carbon Cycle - Land

photosynthesis aerobic respirationterrestrial

rocks

soil water

land food webs

atmosphere

peat, fossil fuels

combustion of wood

sedimentation

volcanic action

death, burial, compaction over geologic time

leaching, runoff

weathering

combustion of fossil fuels

Figure 48.16 Page 878

Carbon in Atmosphere

Atmospheric carbon is mainly carbon dioxide

Carbon dioxide is added to atmosphereAerobic respiration, volcanic action,

burning fossil fuels

Removed by photosynthesis

Greenhouse Effect

Greenhouse gases impede the escape of

heat from Earth’s surface

Figure 48.18, Page 880

Global Warming

Long-term increase in the temperature of

Earth’s lower atmosphere

Figure 48.19, Page 881

Nitrogen Cycle

Nitrogen is used in amino acids and

nucleic acids

Main reservoir is nitrogen gas in the

atmosphere

Nitrogen Cycle

gaseous nitrogen (N2) in atmosphere

NO3-

in soil

nitrogen fixationby industry

fertilizers

NH3-,NH4

+

in soil

1. Nitrification leaching

uptake by autotrophs

excretion, death, decomposition

uptake by autotrophs

nitrogen fixation

leaching

ammonification 2. Nitrification

dentrification nitrogenous

wastes, remains

NO2-

in soil

food webs on land

Figure 48.21Page 882

Nitrogen Fixation

Plants cannot use nitrogen gas

Nitrogen-fixing bacteria convert

nitrogen gas into ammonia (NH3)

Ammonia and ammonium can

be taken up by plants

Ammonification & Nitrification

Bacteria and fungi carry out ammonification

conversion of nitrogenous wastes to ammonia

Nitrifying bacteria convert ammonium to

nitrites and nitrates

Nitrogen Loss

Nitrogen is often a limiting factor in

ecosystems

Nitrogen is lost from soils via leaching

and runoff

Denitrifying bacteria convert nitrates

and nitrites to nitrogen gas

Phosphorus Cycle

Phosphorus is part of phospholipids and

all nucleotides

It is the most prevalent limiting factor in

ecosystems

Main reservoir is Earth’s crust; no gaseous

phase

Phosphorus Cycle

GUANO

FERTILIZER

TERRESTRIAL ROCKS

LAND FOOD WEBS

DISSOLVED IN OCEAN

WATER

MARINE FOOD WEBS

MARINE SEDIMENTS

excretion

weathering

mining

agricultureuptake

by autotrophs

death, decomposition

sedimentationsettling

out leaching, runoff

weathering

uplifting

over geologic time

DISSOLVED IN SOILWATER,

LAKES, RIVERS

uptake by

autotrophs

death, decomposition

Figure 48.23, Page 884

Human Impact

Human Impact

As human populations increase and technology advances, we have a more significant impact on the environmentAffects of agricultureClimatic disruptionThreat to biodiversityHabitat destruction

Human Impact

As a result of large scale agriculture and industrialization, humans have utilized resources on a large scaleThis often disrupts many of the

geochemical cycles

Agriculture

In order to feed the massive number of humans (again, increasing at a geometric rate), we must tax the landClearing natural vegetation to make room

for agriculture (most recent study, shows about 200,000 acres of the Amazon rainforest is burned daily)

Supplementing the soil to support large scale agriculture (huge disruption in the nitrogen cycle)

Human Impact on Ecosystems

Increased Eutrophication of Lakes Increase in nutrient levels

(phosphates, nitrates, etc.)• Can lead to algal blooms

• Hypoxia • What is it?• Why?

• Can lead to the eventual loss of fish and other aquatic organisms

• Accelerated by sewage/factory wastes, leaching of fertilizers into freshwater

Human Impact on Ecosystems

Combustion of Fossil Fuels Leads to acid

precipitation Changes the pH of

aquatic ecosystems and affects the soil chemistry of terrestrial ecosystems

Also, has a huge impact on the carbon cycle

Biological Magnification

Land and water pollution can be a big problem for many organisms Chemicals that we use on farms and in

our homes can be toxic to wildlife Many chemicals that enter an

ecosystem undergo biological magnification, a process in which chemicals become more concentrated as they move up the food chain

Human Impact on Ecosystems

Biological Magnification Toxins become more

concentrated as they move up the food chain

• Toxins that are lipophilic cannot be excreted in urine (water!), so they are stored in fatty tissue (adipose tissue) unless the organism has enzymes to break it down

• Important examples? The biomass at any given

trophic level is produced from a much larger biomass ingested from the level below

Fewer predators at higher levels means more poison in each organism

Human Impact on Ecosystems Increasing Carbon Dioxide Concentration in the

Atmosphere Burning fossil fuels (wood, coal, oil) releases CO2

Carbon dioxide and water in the atmosphere retain solar heat, causing the greenhouse effect

Acts as a blanket to warm the Earth

• Greenhouse effect allows life on the planet

• Too many greenhouse gasses raises the temperature to the Earth too much

How much has Earth’s temperature changed?

What does this mean?

In a nutshell . . . We don’t knowPossibilities:

• Melting polar icecaps (evidence for this is supported) and raise ocean levels

• Severe climate changes (increased frequency in hurricanes in the last couple of decades

• Increased severity of storms (el Nino)

Human Impact on Ecosystems

Use of chlorofluorocarbons has destroyed ozone (O3) by converting it to oxygen gas.

Ozone protects against UV radiationIncreasing skin cancers, cataractsWhat are your odds of getting skin

cancer in your lifetime?

Ozone levels over Antartica

Effects of Human Impact

Biodiversity Why is biodiversity so important?

Conservation biology: utilizes ecology, psychology, and evolutionary biology to develop strategies to sustain ecosystems on Earth

Restoration biology: applies ecological principles to restore degraded ecosystems to their former health

Levels of biodiversity

Genetic diversity: genetic variation in populations (because of in-breeding, cheetahs have very little genetic diversity)

Species diversity: because of the inter-relatedness of food webs, species are important. Because of human impact, many species are endangered or threatened (likely to become endangered)

Levels of biodiversity

Ecosystem diversity: damage by industrialization and agriculture has drastically altered or destroyed different ecosystems.

Major threats to biodiversity

Habitat destruction – by agriculture, urban development, logging, mining, general pollution

Introduced species – whether intentionally or unintentionally has drastically altered many ecosystems

Overexploitation – harvesting wild plants or animals at such a rate that the organisms cannot regenerate their populations (makes many species endangered or extinct)

Major threats to biodiversity

Disruption of interaction networks – removing or altering the composition of keystone species or dominant species can have drastic effects on ecosystem balance

Restoration efforts

Assumption: Most damage to an environment is reversible

Even though this is optimistic, the reality is that many communities are not infinitely resilient

Restoration ecologists must work to manipulate with processes that can speed recovery

Bioremediation Bioremediation: use of living organisms to

detoxify polluted ecosystemsUsually prokaryotes, fungi, or plants In San Luis Obispo, there was an oil spill at

a place called Avila Beach• We were researching bacteria that can

“eat” hydrocarbons and break them down to water and carbon dioxide

• What would be concerns with releasing organisms into the environment?

Biological Augmentation

Bioremediation looks to remove harmful pollutants

Biological Augmentation looks to use organisms to add essential materials to a degraded ecosystemUse of natural fertilizers, enrich

degraded soil with organic material, introduce plant species that rejuvenate soil