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 CO 2 to make their food –Animals eat plants, release CO 2 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 1 st level represents producers Higher levels are stacked on lower levels Sun is energy

Energy pyramid