Ecosystems and Energy Chapter 3. What is Ecology? Ecology – study of the interactions among organisms and between organisms (biotic) and their abiotic.

Ecosystems and Energy

Chapter 3

What is Ecology?

Ecology –

study of the interactions among organisms and between organisms (biotic) and their abiotic environment.

• Biotic – Living component of the environment– Ex: birds, insects

• Abiotic– Nonliving or physical components of the

environment Ex: light, oxygen

What is Ecology?

Levels of Biological Organization

Ecologist are most interested in the level that includes or is above an individual organism. (From elephant )

What is Ecology?

Ecological Levels of Organization:

Population: group of organisms of the same species that live together in the same area at the same time

What is Ecology?

Ecological Levels of Organization:

Community: all the populations of different species that live and interact together within an area at the same time

What is Ecology?

Ecological Levels of Organization:

Ecosystem: A community and its physical environment

CO2

What is Landscape Ecology?

A subdiscipline that studies ecological processes that operate over large areas

Landscape –

encompasses larger area and several ecosystems

Biosphere –

the whole earth

The Energy of Life

• What is energy?– The capacity or ability to do work

• Energy exist in different forms– Chemical, radiant (light), thermal (heat),

mechanical, nuclear, electrical

• Units– Kilojoules (kJ)– Kilocalories (kcal)– 1 kcal = 4.184 kJ

The Energy of Life

Potential vs. Kinetic Energy

This is stored energy

This is the energy of motion

Potential energy changed into kinetic energy when the arrow is released

The Energy of Life

Thermodynamics –

The Energy of Life

1st Law of Thermodynamics –

energy can change forms, but is not created or destroyed

2nd Law of Thermodynamics –

“Entropy Rules!”

amount of usable energy decreases as energy changes forms

1st Law deals with quantity of energy,

2nd Law with quality of energy.

The Energy of Life

Photosynthesis

6 CO2 + 12 H2O + radiant energy

C6H12O6 + 6 H2O + 6 O2

Sugar

In photosynthesis, energy from the sun is stored in plants

The Energy of Life

Cellular Respiration

C6H12O6 + 6 O2 + 6 H2O

6 CO2 + 12 H2O + energy

In cellular respiration stored energy is released to do work

The Energy of Life

Case-in-Point: Life Without the Sun

This picture shows a hydrothermal vent ecosystem found at the bottom of the ocean

Bacteria living in the tissue of the tube worm extract energy from hydrogen sulfide

The Flow of Energy Through Ecosystems

Producers, Consumers, and Decomposers

Energy flows from Producers

To Consumers

And finally to Decomposers

The Path of Energy Flow

Food Chains –Shows the flow of energy in an ecosystem where energy

from food passes from one organism to another.

Starts here

Note that energy is lost as heat

Ends with decomposers

Food Webs –

How is a food web different from a food chain?

•A more realistic model

•Consist of interlocking food chains

•Takes into account different food sources for an organism

The Path of Energy Flow

Case-in-Point: How Humans Have Affected the Antarctic Food Web

Krill

Baleen whales

Squid Fishes

Toothed whalesSealsPenguins

What would happen if you eliminated krill?

The Path of Energy FlowEcological Pyramids

graphically represent the relative energy values of each trophic level.

Pyramid of Numbers

•A pyramid of numbers shows the number of organisms at each trophic level in a given ecosystem.

•The organisms at the based of the food chain are the most abundant, and few organisms occupy each successive trophic level, giving the pyramid its shape.

Ecological Pyramids

Pyramid of Biomass

A pyramid of biomass illustrates the total biomass at each successive trophic level

Biomass is a quantitative estimate of the total amount of living material and indicates the amount of fixed energy at a particular time.

Ecological Pyramids

Pyramid of Energy

•A pyramid of energy illustrates the energy content of the biomass of each trophic level.

•These pyramids always have large energy bases and get progressively smaller through succeeding trophic levels showing that most energy dissipates into the environment when going from one trophic level to the next.

The Path of Energy Flow

Example: Thermodynamics in Action

Desert: Primary producers = 100 g / m2

Temperate forest: Primary producers = 1,500 g / m2

Food webs very simple, very few tertiary consumers

Food webs very complex, more tertiary consumers, some quaternary.

The Path of Energy Flow

Desert Biomass Pyramid

Primary producers = 100 g / m2

Primary consumers = 10 g / m2

Secondary consumers = 1.0 g / m2

Tertiary consumers = 0.1 g / m2

Tertiary consumers must range over large areas to obtain enough energy to subsist.

such as . . .13.5 kg coyote must range ~12 ha to subsist (30 acres).

The Path of Energy Flow

Temperate Forest Biomass Pyramid

Primary producers = 1,500 g / m2

Primary consumers = 150 g / m2

Secondary consumers = 15 g / m2

Tertiary consumers = 1.5 g / m2

13.5 kg coyote only needs ~1 ha to subsist (2.5 acres).

Also, possibility of quaternary consumers, like bears.

NOTE: just relative examples, not accurate

The Path of Energy Flow

Ecosystem Productivity

Net Primary Productivity

Gross Primary Productivity

Plant cellular respiration=

Net primary productivity (NPP)

• Plants respire to provide energy for their own use so that the energy in plant tissues after cellular respiration has occurred is the net primary productivity (NPP).

• The Net primary productivity represents the rate organic matter is actually incorporated into plant tissues for growth.

• Only the energy represented by NPP is available as food for an ecosystem’s consumers.

Gross Primary Productivity (GPP)

• Gross primary productivity (GPP) of an ecosystem is the rate energy is captured during photosynthesis. (Total energy)

• It is primary because plants occupy the first trophic level in food webs.

Human Impact on Net Primary Productivity

• Humans consume more of Earth’s resources than any other animal species.

• When both direct and indirect human impacts are accounted for, humans use 32% of the annual NPP of land-based ecosystems.

• Humans represent only 0.5% of the total biomass of all consumers and are in competition with other species’ needs for energy.

• Human use of so much of the world’s productivity may contribute to the loss of many species through extinction.

• To minimize this impact, humans must share terrestrial photosynthesis products, NPP with other organisms and control the population explosion.

The Path of Energy Flow

Ecosystem Productivity

Note that areas with more producers have a higher NPP