The Biosphere

What is Ecology?Ecology – the scientific study of interactions among

organisms and between organisms and their environment, or surroundings.

• Biotic – living

• Abiotic – non-living

Both biotic and abiotic factors shape an ecosystem

Ex: Affect of drought on skunk population

Biosphere – the combined portions of the planet in which all of the life exists, including land, water, and air, or atmosphere. It extends from about 8 km above Earth’s surface to 11 km below the ocean surface.

Levels of OrganizationTo understand relationships within the biosphere,

ecologists ask questions about events and organisms that range in complexity from a single individual to the

entire biosphere.

Levels of OrganizationSpecies - a group of organisms so similar to one another

that they can interbreed and produce fertile offspring.

Populations – groups of individuals that belong to the same species and live in the same area.

Communities – different populations that live together in a defined area.

–These clams that live near

an ocean vent constitute a

population

Levels of Organization

Ecosystem – a collection of all organisms that live in a particular place, together with their nonliving, or physical, environment.

Biome – a group of ecosystems that have the same climate and similar dominant communities.

Biosphere – the region of the

Earth that supports life

Ecological MethodsRegardless of the tools they use, scientists conduct

modern ecological research using three basic approaches: observing, experimenting, and modeling.

All of these approaches rely on the application of scientific methods to guide ecological inquiry.

Energy FlowSunlight is the main energy

source for life on Earth.

Some types of organisms rely on the energy stored in

inorganic chemical compounds.

Autotrophs – plants, some algae and certain bacteria can capture energy from sunlight or chemicals and use that energy to produce food.

Producers – organisms that make their own food (autotrophs).

Energy Flow – With NO Light!

Chemosynthesis – when organisms use chemical energy to produce carbohydrates. Such as sulfur bacteria converting sulfur compounds into carbohydrates around thermal vents in the ocean. Ex: Chemosynthetic Bacteria

Thermal vent

Energy Flow – From the Sun

Photosynthesis – the conversion of light energy into chemical energy which is stored within organic compounds.

Energy Flow – ConsumersHeterotrophs – organisms that rely on other organisms

for their energy and food supply; also known as consumers.

Consumers include animals, bacteria & fungi

Energy Flow – Consumer TypesHerbivores – animals that obtain energy by eating only

plants. Ex: cows & caterpillars

Carnivores – organisms that obtain energy by eating animals. Ex: snakes, dogs & owls

Omnivores – organisms that obtain energy by eating both plants and animals. Ex: humans, bears & crows

Detritivores – organisms that feed on plants and animal remains and dead matter (detritus).

Ex: mites, earthworms & snails

Decomposers – break down organic matter. Ex: bacteria & fungi

Feeding RelationshipsEnergy flows through an ecosystem in

one direction, from the sun or inorganic compounds to autotrophs

(producers) and then to various heterotrophs (consumers).

Food chain – a series of steps in which organisms transfer energy by eating and being eaten.

TROPHIC LEVEL

Quaternaryconsumers

Tertiaryconsumers

Carnivore Carnivore

Carnivore Carnivore

Carnivore Carnivore

Herbivore Zooplankton

Plant Phytoplankton

Secondaryconsumers

Primaryconsumers

Producers

A TERRESTRIAL FOOD CHAIN AN AQUATIC FOOD CHAIN

Trophic Levels•Each step in a food chain or food web is called a trophic level.

•Producers make up the first trophic level.

•Consumers make up the second, third, or higher trophic levels.

•Consumers depend on the trophic level below it for energy.

Tertiaryandsecondaryconsumers

Secondaryandprimaryconsumers

Primaryconsumers

Producers

(Plants, algae,phytoplankton)

Detritivores

(Prokaryotes, fungi,certain animals)

Wastes anddead organisms

Food Web – the feeding relationships among the various organisms in an ecosystem form a network of complex interactions; the interactions of all the food chains in an ecosystem.

Ecological PyramidsAn ecological pyramid is a diagram that shows the

relative amounts of energy or matter contained within each trophic level in a food chain or food web.

Energy Pyramid – shows the relative amount of energy available at each trophic level.

Only about 10 % of the energy available within one trophic level is transferred to organisms at the next trophic level.

Ecological PyramidsBiomass – the total amount of living tissue within a

given trophic level. Biomass is usually expressed in terms of grams of organic matter per unit area.

Cycles of MatterUnlike the one-way flow of energy, matter is recycled

within and between ecosystems.

Biogeochemical cycle – process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from one part of the biosphere to another.

Solarheat

Precipitationover the sea(283)

Net movementof water vaporby wind (36)

Flow of waterfrom land to sea(36)

Water vaporover the sea

Oceans

Evaporationfrom the sea(319)

Evaporationandtranspiration(59)

Water vaporover the land

Precipitationover the land(95)

Surface waterand groundwater

Water Cycle

Water CycleEvaporation – the process by which water changes from

liquid form to an atmosphere gas.

Transpiration – when water enters the atmosphere by evaporating from leaves of plants.

Nutrient CyclesNutrients – all the chemical substances that an organism

needs to sustain life.

Every living organism needs nutrients to build tissues and carry out essential life functions. Like water, nutrients are passed between organisms and the

environment through biochemical cycles.

Carbon CycleCO2 in atmosphere

Cellular respiration

Higher-levelconsumers

Primaryconsumers

Plants,algae,

cyanobacteria

Photosynthesis

Wood andfossil fuels

Detritivores(soil microbes

and others) Detritus

Decomposition

Burning

Nitrogen Cycle

• Nitrogen is plentiful in the atmosphere as N2

– But plants cannot use N2

Nitrogen Fixation• Various bacteria in soil (and legume root nodules)

convert N2 to nitrogen compounds that plants can use

– Ammonium (NH4+) and nitrate (NO3

–)

• Some bacteria break down organic matter and recycle nitrogen as ammonium or nitrate to plants

Denitrification

• Other bacteria return N2 to the atmosphere by converting nitrates into N2

Nitrogen (N2) in atmosphere

Amino acidsand proteins in

plants and animalsAssimilationby plants

Denitrifyingbacteria

Nitrates(NO3

–)

Nitrifyingbacteria

Detritus

Detritivores

Decomposition

Ammonium (NH4+)

Nitrogenfixation

Nitrogen-fixingbacteria in soil

Nitrogen-fixingbacteria in root

nodules of legumes

Nitrogenfixation

Nitrogen Cycle

Phosphorus Cycle

Phosphates (compounds containing PO43-) and other

minerals are added to the soil by the gradual weathering of rock.

Consumers obtain phosphorus in organic form from plants.

Phosphates are returned to the soil through excretion by animals and the actions of decomposers.

Phosphorus is essential to living organisms because it forms part of important life-sustaining molecules such as DNA & RNA.

Upliftingof rock

Phosphatesin solution

Weatheringof rock

Phosphatesin rock

Phosphatesin organic

compounds

Detritus

Detritivoresin soil

Phosphatesin soil

(inorganic)

Rock Precipitated(solid) phosphates

Plants

Animals

Decomposition

Runoff

Phosphorus Cycle

Nutrient LimitationPrimary productivity – the rate at which matter is created

by producers.

Limiting nutrients – single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem.

Algal bloom – the result of runoff from heavily fertilized fields – the result is often immediate increase in the amount of algae and other producers.