Association Between People and the Natural World

• All resources for human survival come from the natural world.

• What if society fails to care for and sustain ecosystems?

• What if population increases beyond carrying capacity?

• Disparity between rich and poor widens - social strife- collapse.

Easter Island, Central Pacific Ocean (ca. 1600)

Ecosystems: What are they? = 1) sustainable units of life; 2) all species of a biotic community living within a specified area and interacting among themselves and with abiotic factors; and 3) learning tools for creating a sustainable society and understanding the impact of our actions.

• Ecosystem connectivity and scale.• Major ecosystem principles.• Ecosystem structure:

– Limiting abiotic factors.– Feeding (trophic) relationships– Non-feeding relationships.

Ecosystem types on land are defined by climate, plant association, and soil.

Adjacent ecosystems are connected by an ecotone.

High Diversity

Some ecotones, like those between land and water, form unique transitional ecosystems.

Unique marsh species

Landscapes are groupings of connected and interacting ecosystems.

All landscapes with common characteristics are grouped into biomes.

Aquatic ecosystems can be categorized into types based on light, depth, temperature, and salinity (Table 2.1).

Earth as a whole is the largest scale ecosystem, called the biosphere.

Major Ecological Principles

Diversity * species (biodiversity)* habitat (“address”)* niches (“job”)

Interrelationships* with environmental factors* among populations

Cycles* nutrients get reused* nitrogen & phosphorous* organic to inorganic …

Energy* flows through ecosystems* conserved but transformed

Environmental factors refer to conditions and resources.

• Environmental factors set limits on growth of a species and thereby its distribution.

• Organisms must live within the tolerance range of environmental conditions (abiotic factors of temperature, moisture, sunlight, pH, salinity).

• Resources (what an organism consumes) must be adequate for survival. Too much or too little may be harmful.

Plant Growth:

Conditions?• temperature

• soil pH

• soil salinity (saltiness)

• sand-silt-clay

Resources?• light

• water

• inorganic nutrients

- nitrogen

- phosphorous

- potassium

Climate Determines Biome Type

• Average temperature and precipitation characteristics of a region defines climate.

• Climate selects the type of plant association.

– Continuous high rainfall and mild temperature?

– Rare rainfall and hot temperature?

Colder conditions slows evaporation from soil and plant water losses.

Greater precipitation favors forest development, except in tundra

Climate changes with both latitude

and altitude

Trophic (Feeding) Levels

Third-order Consumer

Secondary Consumer

Primary Consumer

Primary Producer

Decomposers and Detritus Feeders

Only 10% energy transfer to each higher trophic level! What are the implications?

Inorganic nutrients

Match Organism with Trophic Level(s)

Trophic LevelsOrganisms Primary

ProducerPrimary Consumer

Secondary Consumer

Third-Order Consumer

Grasses X

Rabbits X

Snakes X

Owls X X

Humans X X X

Bacteria X X X X

Autotrophs:

Produce organic matter from inorganic nutrients, carbon dioxide, and light energy; called primary producers; most perform photosynthesis.

Heterotrophs:

Feed on organic matter for energy and growth.

Consumers eat the living.

Decomposers and detritus feeders eat dead organic matter, detritus.

Consumer Types:

Herbivores

Carnivores

Omnivores

Consumer Relationships:

Predator-prey

Host-Parasite

Decomposers & Detritus Feeders

Biomass and Energy Pyramids

What is an energy efficient diet for humans?

Complexity of Feeding Interactions:Food Webs

Non-Feeding Relationships

• Mutualism: two organisms benefit each other’s survival; may live where they could not if alone.

• Competition: habitat and niche diversity reduces competition; favors greater biodiversity.