EcologyModule 15

Organization of the Biosphere

Levels of organization

▪ Biosphere▪ Biome▪ Ecosystem

▪ Biotic factors – living▪ Abiotic factors – non living

▪ Community▪ Population▪ Organism

The ecological “niche”

Every organism in a community has a specific NICHE:The organism’s ROLE in the ecosystem - •Habitat•Place in food web•Interrelationships

Transfer of Energy•An ecosystem’s ultimate source of energy is the SUN

•Solar energy is used by “producers” to make food.

•“Consumers” eat producers (or other consumers) to gain food.

•Each step in the food web is called a TROPHIC LEVEL

Transfer of Energy

Arrows show the transfer of energy from one organism to another

Energy moves inONE DIRECTION!

Transfer of Energy

Ecological Efficiency▪ Only about 10% of the

available energy in one trophic level is passed to the next trophic level▪ The “lost” energy is

used for biological work (eating, growing, respiring, etc) and is converted to HEAT.

Producers

Primary consumers

Secondary consumers

Tertiaryconsume

rsLEAST energy

MOST energy

Cycling of Matter

Role of Decomposers▪ Break down wastes

and dead organisms▪ Decomposition allows

nutrients to be returned to the soil and reused▪ Includes bacteria,

fungi, and some invertebrates

Biogeochemical Cycles

Water Cycle: Nitrogen Cycle:

Biogeochemical Cycles

Carbon Cycle:▪ Driven by photosynthesis

and cellular respiration▪ Decomposition is a form

of cellular respiration▪ Fossil fuel combustion

adds CO2 to atmosphere▪ Deforestation removes

trees that should remove CO2

Community Interactions

Organisms in a community interact with each other in many ways. Some of these interactions include:▪ Competition▪ Predation▪ Symbiosis Communi

tyInteractio

ns

Competition

Predation

Symbiosis

Community Interactions

CompetitionA struggle for resources (food, space, abiotic factors, mates)

Community Interactions

PredationSome organisms (predators), consume others (prey)

Community InteractionsSymbiosis

A close, permanent relationship between 2 organisms – NOT predation or competition!

Mutualism (+,+) Parasitism (+,-)Commensalism (+, 0)

Population Growth

J-Curve: S-Curve:

Time Time

# orga

nism

s

# orga

nism

sExponential growth: rapid growth in a short period of time

Carrying Capacity:The maximum number of individuals an environment can support

Limiting Factors – establish carrying capacity and limit the size of a population

Density Dependent:Includes food, disease, mates

Density Independent:Includes natural disasters

Population Growth

Populations fluctuate around the carrying capacity….

This is called “dynamic equilibrium”.

Change in COMMUNITIES over time

Succession:Communities change over time in a predictable, orderly way over many decades

Changes in plant communities lead to changes in animal communities