Energy Flow in

Ecosystems and

Biogeochemical

Cycles

Hierarchy of ecology Organism - individual living

thing

Population- a group of the same species

Community – a group of

different species

Ecosystem – all organisms as well as nonliving things in an

area

Biome - a major regional or

global community of organism

- can be as small as the

microorganisms living on your skin or as large as the entire

biosphere

What’s an Ecosystem? An ecosystem consists of all the organisms (biotic) in

a community and the environment (abiotic) with

which they interact.

Biotic - living things

plants animals, fungi, bacteria

Abiotic - non-living things

Moisture, temperature, wind,

sunlight, & soil

Biodiversity

The assortment, or variety, of living things in an

ecosystem

KEYSTONE Species = a species that has an unusually

large effect on its ecosystem

Producer Herbivore

(primary consumer)

Detritivores

(decomposers)

Carnivore

(secondary

consumer)

Energy flow

Energy flows THROUGH ecosystems – open system

Chemical cycling

Nutrients cycle WITHIN ecosystems – closed system

Get their energy

from non-living

sources and make

their own food

Get their energy

by eating living, or

once living,

resources, such as

plants and animals

Break down

organic materials

into simpler

cpmpounds

Energy Flow in Ecosystems

Almost all energy used in

ecosystems comes from

the sun

From there it flows

through a food chain or

web and exits the

ecosystem in the form of

heat, light, kinetic or

chemical energy

A food chain is a sequence

that links species by their

feeding relation

A food web is a model

that shows the

complex network of

feeding relationships

and flow of energy

within an ecosystem

Types of Consumers

Herbivores – eat only plants

Carnivores – eat only animals

Omnivores – eat both plants and animals

Detritivores – eat detritis or dead and dying organic matter

Decomposers - - detritivores that break down organic matter into simpler compounds (example : fungi)

Decomposers

Energy pyramids show the efficiency of energy transfer between trophic levels

Generally 10% of energy is transferred

Food chains never get beyond 4-5 trophic levels

Carnivores that eat secondary consumers

Carnivores that eat herbivores

Herbivores because they are the first consumer

above the producer

The first , or bottom, trophic level

Consumers

Producers

Nutrients

available

to producers

Detritivores

Biogeochemical Cycle

Abiotic

reservoir

Biogeochemical Cycling of Nutrients

The movement of a particular chemical through the biological and geological, or living and non-living parts of an ecosystem.

Most ecosystems require a constant inflow of energy from the sun. In terms of matter, such as oxygen and carbon, the Earth is a closed system and it recycles its resources.

Water cycle

Oxygen cycle

Carbon cycle

Nitrogen cycle

Phosphorous cycle

Water Cycle

Solar energy drives the global water cycle

– Precipitation

– Evaporation

– Transpiration

Water cycles between the land, oceans, and atmosphere

Forest destruction and irrigation affect the water cycle

Solar energy

Net movement of

water vapor by wind

Evaporation

from ocean

Precipitation

over ocean

Evaporation and

transpiration from

land

Transport

over land

Precipitation

over land

Percolation

through

soil

Runoff and

groundwater

Carbon Cycle

• Abiotic reservoirs = atmosphere, sedimentary rocks, dissolved carbon in oceans, and fossil fuels

– Taken from the atmosphere by photosynthesis

– Used to make organic molecules

– Decomposed by detritivores

– Returned to the atmosphere by cellular respiration

Photosynthesis

Burning of

fossil fuels

and wood Primary

consumers Higher-level

consumers

Cellular respiration

Detritus

CO2 in atmosphere

Carbon compounds

in water

Decomposition

Global warming:

CO2 lets sunlight

through but retains

the heat radiated

from Earth.

CO2 in the

atmosphere

CO2

CO2 CO2

Human activities and natural

processes add CO2 to the

atmosphere, increasing the effect.

Photosynthesis removes

CO2 from the atmosphere,

decreasing the effect.

Nitrogen Cycle

The nitrogen cycle relies heavily on bacteria

• Atmospheric N2 is not available to

plants

– Soil bacteria convert gaseous

N2 to usable ammonium (NH4+)

and nitrate (NO3-)

– Some NH4+ and NO3

- are made

by chemical reactions in the

atmosphere

Nitrogen in atmosphere (N2)

Nitrogen

fixation

Detritivores

Decomposition

Assimilation

by plants

Denitrifying

bacteria Nitrates

(NO3–)

Nitrifying

bacteria

Nitrogen-fixing

bacteria in root

nodules of legumes

Nitrogen-fixing

soil bacteria

Ammonium (NH4)

80%

Phosphorus Cycle

Depends on the weathering of rock

• Phosphorus and other soil minerals

are recycled locally

• Weathering of rock adds PO43- to

soil

– Slow process makes amount of

phosphorus available to plants

low

Runoff

Sedimentation