Ecosystems and Energy

Chapter 3

Ecology Study of the interactions of organisms and

their living and non-living environment Many different scales to ecology Abiotic factor – Non-Living environment

Example: Wind, soil, precipitation Biotic factor – Living environment

Example: all organisms (plants, people)

Organism – any living thing Species – Group of organisms who interbreed

and produce fertile offspring Population – A group of organisms in the same

species that live in the same area at the same time Community – All populations in the same area,

at the same time that interact Ecosystem – A community together with its

physical environment Landscape – several interacting ecosystems Biosphere – All living organisms on Earth

Levels of Ecology

Biosphere - All living organisms on Earth Hydrosphere – All of Earth’s water supply Atmosphere – Gases that surround the

Earth Lithosphere – Soil and rock of Earth’s

crust

Ecology encompasses the study of the interrelationships among Earth’s biosphere, hydrosphere, atmosphere and lithosphere

Energy – ability to do work Energy is the capacity to do work

measured in kJ (work) or kcal (heat) Kcal = raise 1kg water 1 degree = 4.184 kJ

Different forms of energy Electrical, chemical, solar, mechanical,

nuclear, thermal Potential vs. Kinetic energy

Thermodynamics Open system –

Closed system -

First Law of Thermodynamics Energy cannot be created or destroyed. It

can be transferred from one form to another

An organism cannot create the energy that it requires to live Plants Sponge Bacteria Humans

Second Law of Thermodynamics Whenever energy is converted from one form to another,

some usable energy is lost in thermal energy that disperses into the environment

Entropy – Measure of disorder or randomness Entropy tends to increase over time No energy conversion process is 100% efficient

Cars = 20-30% efficient Cells = 50% efficient

Order is maintained through constant energy input

Photosynthesis Light energy from the sun is converted to

chemical energy carbohydrates (glucose) Uses photosynthetic pigments (chlorophyll)

6CO2 + 12H2O + sun C6H12O6 + 6H2O + 6O2

Cellular Respiration Organic molecules (glucose) are broken down to

release energy Usually in the presence of water and oxygen

C6H12O6 + 6O2 + 6H2O 6CO2 + 12H2O + energy

Energy FLOW in an ecosystem Enters as solar energy (sun) Photosynthesis (plants) Stored energy (organic molecules) Cellular respiration Some lost to environment (2nd Law of

thermodynamics)

Roles in an ecosystem Producers/Autotrophs Consumers/Heterotrophs

Primary ConsumersHerbivores (omnivores)

Secondary ConsumersCarnivores (omnivores)

Tertiary Consumers Detritus Feeders

Decomposers/Saprotrophs

Food chainAlways linear

Simplistic

Food Web More complex

Ecological PyramidShows relative energy values in each trophic level

10% rule

Pyramid of numbers Usually more

producers than consumers

More prey than predators

Pyramid of Biomass Biomass –

Quantitative estimate of total mass of living material

Usually in units (g/m2)

Pyramid of energy Energy content

(kcal/m2/year) Never 100% efficient 10% Rule Usually not more than

4 or 5 trophic levels

Productivity of Producers Gross Primary Productivity – (GPP)

Energy that is captured during photosynthesis Net Primary Productivity (NPP)

Energy that remains in a plant after respiration

NPP = GPP – Respiration

Productivity Units : kcal/m2/year Energy fixed by photosynthesis Grams of carbon in tissue Most productive ecosystems:

Rainforests Wetlands, swamps, marshes

Most unproductive ecosystems: Tundra, deserts Open ocean

The NPP for a particular river ecosystem is measured at 8833 kcal/m2/year. Respiration by the aquatic producers is estimated at 11,977 kcal/m2/year. Calculate the GPP for the ecosystem.

NPP = GPP – R

8833 = GPP – 11,977

GPP = 8,833 + 11,977

GPP = 20,810 kcal/m2/year