The Biosphere

Ecology• Study of interactions among organisms and

between organisms and their environment.• Coined by Ernst Haeckel from– Oikos = house– Logos = study of

Biosphere• Combined areas of the Earth where life exists

– includes land, water, and air• From about 8 kilometers above Earth to 11

kilometers below ocean surface

Biosphere is composed of three main parts1. lithosphere – soil and rock of Earth’s crust2. atmosphere – gases surrounding Earth3. hydrosphere – all of Earth’s water

- is a closed system for matter, while energy from the sun flows through the systems

Levels of Organization

• Ecologists study organisms and their environment at many different levels:

• 1. Species- group of similar

organisms that can and do breed in nature to produce fertile offspring.

2. Populations- members of a species that live in the same area at the same time

3. Community- groups of different populations that live together in a defined area

4. Ecosystem4. Ecosystem

- all of the organisms in a given area together with their nonliving, or physical, environment (abiotic)

5. Biome- group of ecosystems that have the same climate and similar dominant communities

6. Biosphere

Ecological MethodsEcologists use the Scientific Method for

discovering more about the natural world.

Three basic approaches:1. Observation – first step in asking

questions2. Experimenting – used to test hypotheses

- Laboratory vs. Field- manipulating variables

3. Modeling – models are developed to gain insight into complex phenomena such as global warming on ecosystems.

Exploring Ecology from Space- to understand global ecology requires remote sensing satellites- optical sensors can sense heat, light, and other wavelengths and

convert that information into data - can assess such things as carbon dioxide levels, temperature, land use

changes, forest destruction, etc.

Energy Flow• All organisms require

energy to power life’s process

• Energy flows through ecosystems

Producers• Organisms that are

capable of using energy to produce organic compounds from inorganic compounds

• Sunlight is main energy source for all living organisms– Less than 1% of

sunlight that reaches the Earth’s surface is used by producers

• Photosynthesis is the most important chemical reaction on Earth for life because it can bring non-living CO2 into the realm of life.

• Converts CO2 and water to simple sugars

6CO2 + 6H2O C6H12O6 + 6O2

• Chemosynthesis – used by some producers to get energy from inorganic compounds

• Autotrophs– Organisms which can produce their

own food – Use energy from the environment to

assemble simple inorganic molecules into large organic molecules

Consumers = Heterotrophs• Organisms which cannot make their own

food from inorganic molecules• Must consume other organisms for energy

and food supply• Herbivores – eat plants• Carnivores – eat animals• Omnivores – eat both plants and animals• Detritivores – eat detritus (remains of dead

organisms)• Decomposers – break down organic matter

into inorganic compounds

Food Chain- series of organisms

which transfer energy and matter from one tothe other in feedingrelationships

Trophic Levels- each step in a food

chain

Food Webs- all of the

interconnected food chains in an ecosystem.

Ecological Pyramids- diagrams which show the relative amounts of energy, matter, or number of

organisms at each trophic level- most look like a pyramid because of decreasing amounts of what is being

measured as you move up trophic levels in an ecosystem- pyramid of biomass and pyramid of numbers can sometimes be inverted

Energy Pyramid – only about 10% of energy passes from one trophic level to the next.- limits the number of trophic levels in an ecosystem

Pyramid of Numbers – shows numbers of individuals at each trophic level. - sometimes is inverted due to fewer producers

Biomass Pyramid –shows the amount of living tissue at each trophic level.

Cycles of MatterWhile energy flows through

ecosystems, matter is recycled repeatedly from non-living sources through living organisms and back to the abiotic world.

Biogeochemical Cycles – cycles which move matter through and between ecosystems and connect biological, geological, and chemical aspects of the biosphere.

Matter isn’t used up, but transformed by living organisms.

Water Cycle – all living organisms need water.

Nutrient Cycles• Organisms need nutrients to build tissues and carry out essential life functions.• Primary producers are able to bring nutrients in as simple inorganic forms and

convert them to organic compounds.Carbon Cycle• Biological process such as photosynthesis, respiration, and decomposition take

up and release carbon dioxide and oxygen• Geochemical processes such as erosion and volcanic activity release carbon

dioxide to the atmosphere.

• Mixed biogeochemical process such as burial and decomposition of dead organisms and conversion under pressure to fossil fuels store carbon underground

• Human activities such as mining, cutting and burning forests, and burning fossil fuels release carbon dioxide into the atmosphere.

Carbon Cycle – pg. 77

Nitrogen Cycle• All organisms need nitrogen to

make amino acids which are used to build proteins

• Nitrogen gas makes up 78% of the atmosphere

• Several types of bacteria convert nitrogen from one form to another

• Nitrogen fixation converts nitrogen gas into ammonia which can be converted into usable nitrates and nitrites.

• Bacteria in the nodules of legumes do nitrogen fixation

• Lightning converts nitrogen gas to usable nitrates and nitrites

• Producers use nitrates and nitrites and consumers get their nitrogen from the producers

• Denitrification converts nitrates back into nitrogen gas

• Humans add nitrates to the biosphere in our fertilizers

The Cape Grim Baseline Air Pollution Station in Tasmania, where air samples have been collected since 1978. These samples show a long-term trend in isotopic composition that confirms that nitrogen-based fertilizer is largely responsible for the 20 percent increase in atmospheric nitrous oxide since the Industrial Revolution. Photo courtesy of CSIRO.

Nitrogen Cycle – pg. 78

Phosphorus Cycle• Important in DNA and RNA• Not a common element in the biosphere• Does not enter atmosphere, but exists in rock and soil minerals, and

in ocean sediments.

Phosphorus Cycle – pg 79

Primary Productivity – rate at which organic matter is created by producers- available nutrients help control productivity

Nutrient Limitation• When an ecosystem is limited by a single nutrient that is scarce or cycles very

slowly this substance is called a limiting nutrient.• Farmers apply fertilizers to make up for this• When fertilizers run-off into water they sometimes cause algal blooms

– Algae grow rapidly and sometimes cover the water– When algae die, their decomposition removes oxygen from the water and

causes many animals to die.

• Eutrophication- increase in plant growth in water- water is more rich in nutrients

What is Eutrophication? Eutrophication is a process where bodies of water, such as lakes, estuaries, or slow-moving streams, receive excess nutrients that stimulate excessive plant growth.

This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water. This can kill other marine life which also depend on dissolved oxygen in the water.