Principles of Ecology

Chapter 13

Ecologists Study Relationships

• Interactions and Interdependence Ecology – the

scientific study of interactions among living things and their surroundings

Ecologists Study Relationships

• Biosphere - part of a planet (the earth) in which life exists including land, water, and air

Ecologists Study Relationships

Populations – individuals that live in the same area

Species – a group of individuals that can interbreed

Ecologists Study Relationships

Communities – assemblages of different populations that live togetherCommunities are within the ecosystem

(Ex. A reef in the ocean)

Ecologists Study Relationships

Ecosystem – a collection of all organisms that live in a particular place with their nonliving, or physical environmentScientists often

study species, populations, or communities in an ecosystem.

Ecologists Study Relationships

• Levels of OrganizationBiome – a group

of ecosystems that have the same climate and similar dominant communities

Ecologists Study Relationships

• Ecological MethodsObserving – first step

Long term studies more beneficial-ecological change takes time

SurveysDirect Indirect

Determining Population Size

Catch and releaseQuadrat Sampling

Ecologists Study Relationships

Experimenting – used to test hypothesesCan do in the

field or labLab-more control,

not a true reflection

Field-More accurate, difficult to determine cause and effect relationships

Ecologists Study Relationships

Modeling – gain insightComputersMathematical

modelsUse actual

data to simulate

Data collected using satellite technology

Biotic and Abiotic Factors

• Living and Non-living components– Biotic - living

factors– Abiotic -

nonliving things

Biotic and Abiotic Factors

• Biodiversity– The assortment,

or variety of living things

– Dependent on temperature, moisture

– Keystone Species – species that have a large impact on ecosystems

Energy in Ecosystems• Producers –

organisms that make their own food Autotrophs –

organisms that use energy from the sun or chemicals to make food

Energy in EcosystemsEnergy from the

sun• Photosynthesis

– Autotrophs use light energy to power chemical reactions that make energy

– Uses CO2

– Makes O2 and Carbs

Energy in Ecosystems

Life without light• Chemosynthesis – Use chemical

energy to make carbohydrates– Bacteria deep in the ocean

Energy in Ecosystems• Consumers –

Organisms that need other organisms for their energy and food supply These are also referred

to as heterotrophs

Food Chains and Food Webs

• Feeding Relationships• Food Chains – A series of energy

transferring steps

Food Chains and Food Webs

Types of heterotrophs• Herbivores

– Energy from eating plants

• Carnivores– Energy from eating animals

• Omnivores– Both plants and animals

• Detritivores– Feed on the remains of

dead matter

• Decomposers– Break down organic matter

for energy

Food Chains and Food Webs

• Specialist– Consumer that

primarily eats one specific organism

• Generalist– Have a varying

diet

Food Chains and Food Webs

Trophic Levels – Each step in a food chain or web• First level is producers• Second level on is

consumers-usually herbivores

• Tertiary consumers are usually carnivores

• Each consumer depends on the trophic level below it

Food Chains and Food WebsFood Webs – Feeding relationships

among many organisms in an ecosystem form a network of interactions

Cycling of Matter• The Hydrological Cycle (Water

Cycle)– Evaporation – Water changes from a

liquid to a gas– Transpiration – Evaporation from the

leaves of a plant

Cycling of MatterClouds form from tiny drops of water

collecting called condensation

Cycling of Matter• Recycling in the Biosphere

Biogeochemical cycles• The transforming of matter by biological

systems

– Energy moves in a one way fashion – Nutrients recycle

Cycling of Matter• Nutrient Cycles

Nutrient – All the chemical substances that an organism needs to sustain life

Cycling of Matter• Oxygen Cycle

– Most organisms use oxygen need oxygen

– Plants release oxygen

– Living organisms release carbon dioxide as a waste product

Cycling of MatterThe Carbon Cycle

• Carbon is passed on from one situation to another throughout the biosphere

– Photosynthesis uses CO2 to make carbs

– Carbs are eaten by other organisms

– Organisms exhale CO2

during cellular respiration– All organisms eventually

decay and the carbon is converted to coal or petroleum

– Burning things releases stored CO2 into the atmosphere

Cycling of MatterThe Nitrogen Cycle

• All organisms need nitrogen to make amino acids

– What do amino acids make?– Proteins– 78% of Earth’s atmosphere

Nitrogen gas (N2)– Other types:– Ammonia (NH3)

Nitrate (NO3) Nitrite (NO2)

– Nitrogen fixation – N2 to NH3

– Denitrification - NO3 to N2

Cycling of Matter– The Phosphorus

Cycle• DNA and RNA

need phosphorus • This element does

not go into the atmosphere

• Phosphorus works its way through the food web

Cycling of Matter• Nutrient Limitation

– Ecologists look at the rate of production of producers – Primary Producivity

– Availability of nutrients can limit an ecosystem

– Limiting nutrient• Ecosystem limited by

one nutrient– Nitrogen in the ocean is the

limiting nutrient• 0.00005% nitrogen• If runoff causes a drastic

increase in nitrogen, then an algae bloom occurs

Pyramid Models• Ecological Pyramids – diagram

that shows how much energy is transferred at each trophic level

Pyramid ModelsBiomass Pyramid

• Biomass – Total amount of living tissue in a level

– Represents the amount of potential food available at each trophic level

Pyramid ModelsEnergy Pyramid

• Only about 10 % of the energy is transferred to the next trophic level

– More levels means less energy at the last level

Pyramid ModelsPyramid

NumbersShows how many

individuals there are in each level