Chapter 13

Principals of Ecology

Ecology

• Study of interactions between organisms and their environments

• Reveals relationships between living and nonliving parts

• “ecology” termed by Ernst Haeckel to encourage scientists to study these relationships

Levels of organization

• Organisms• Populations• Communities• Ecosystem• Biosphere

Organisms

• An individual• Depend on others for food, shelter,

reproduction, protection• Can interact with others of same

species or different species• Can interact with abiotic factors

Populations

• Organisms of the same species that interbreed and live in the same area

• Compete for food, water, mates, etc.• Sharing resources determines

distances between populations

Communities

• Interacting populations• Includes different species that live in

the same area• Change in one population affects the

entire community

Ecosystem

• Interactions of populations and abiotic factors in a community

• 3 types–Terrestrial–Aquatic–saltwater

Biome

• Major regional or global community of organisms

• Characterized by climate conditions and plants

The living environment

• Biosphere – portion of earth that supports life– Includes land, air, fresh and salt water–Extends from highest part of

atmosphere to bottom of ocean• Biotic factors – all living factors in the

environment

The nonliving environment

• Abiotic factors – nonliving parts of the environment– Includes air currents, temperature,

moisture, light, and soil–Can determine which species survive in

a particular area

Biodiversity

• Variety of living things in an ecosystem• Amount of biodiversity depends on many

things such as temperature and moisture• Tropical rain forests account for >50% of

the world’s plants and animals• Rain forests and barrier reefs are “hot

spots” and are richly diverse

Keystone species

• Have a large effect on its ecosystem• May hold the dynamic ecosystem together• They form a complex web of life• Loss of the keystone species affects all

species in that ecosystem

Feeding relationships

• 4 types–Autotrophs–Heterotrophs–Scavengers–decomposers

Obtaining energy

• Producers (autotrophs) get their energy from nonliving sources to make their own food– Sunlight or chemicals (chemosynthesis)

• Consumers (heterotrophs) get their energy by eating other organisms

• Sun is the ultimate source of energy for all organisms

Food chains

• Links species by their feeding relationships

• Shows a sample of links that begin with a single producer

• Model used to show passage of matter and energy through the ecosystem

• Arrows indicate energy flow• No more than 5 links

Heterotrophs

• Depend on autotrophs for food• Herbivores eat only plants• Carnivores eat other animals• Omnivores eat plants and animals• Detritivores eat dead organic matter• Decomposers break down organic

matter into simpler substances

Selective eaters

• Specialists – eat primarily one specific organism or a very small variety of organisms

• Generalists – have a varying diet

Trophic levels

• Feeding steps in the passage of energy and materials

• Do not show all relationships

Food webs

• Show complex relationships in an ecosystem

• Expresses all possible relationships at each trophic level

Water (hydrologic) cycle

• Water on earth is liquid or solid; in atmosphere it’s gas

• Steps– Precipitation falls to the ground– Water flows into lakes, rivers; can be

absorbed into soil; most will feed the oceans– Some water evaporates and enters the

atmosphere; released from plants by transpiration

– Condensation produces precipitation

Water cycle

Oxygen cycle

• Organisms need oxygen for cellular respiration

• Plants release oxygen during photosynthesis

• Oxygen is also released by cycling of other nutrients like carbon, nitrogen, and phosphorous

Oxygen cycle

Carbon forms

• Carbon dioxide in the atmosphere• Bicarbonate dissolved in water• Fossil fuels• Carbonate rocks (limestone)• Dead organic matter

Carbon cycle

• Steps–Plants use CO2 to make their food

–Animals eat plants, release CO2 when they breathe or die

–Decay with NO oxygen makes oil–Burning oil releases carbon dioxide

Carbon cycle

Nitrogen cycle

• Gaseous nitrogen makes up 78% of air• Lightning / bacteria convert nitrogen gas to

useable nitrogen for organisms (nitrogen fixation)

• Steps– Plants absorb nitrates– Animals eat plants and make proteins– Death / decay return nitrogen to soil– Breakdown of nitrates by bacteria return

nitrogen to the atmosphere

Nitrogen cycle

Phosphorous cycle

• Steps– Phosphorous released by weathering of rocks–Plants absorb phosphorous–Animals eat plants–Death / decay returns phosphorous to

soil and water–Phosphates can also be made into

rocks; released by erosion

Phosphorous cycle

Ecological pyramids

• Depict energy conversions in an ecosystem

• 1st level represents producers• Higher levels are stacked on lower

levels • Sun is energy

Energy pyramid