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.
High
Diversity
Adjacent ecosystems are connected by an ecotone.
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.
Diversity
Major
* species (biodiversity)
* habitat (“address”)
Ecological
* niches (“job”)
Principles 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?
Greater precipitation
favors forest
development,
except in tundra
Colder conditions
slows evaporation
from soil and plant
water losses.
Climate changes
with both latitude
and altitude
Trophic (Feeding) Levels
Third-order Consumer
Only 10% energy
transfer to each higher
trophic level! What are
the implications?
Secondary Consumer
Primary Consumer
Primary Producer
Decomposers and
Detritus Feeders
Inorganic nutrients
Match Organism with Trophic Level(s)
Trophic Levels
Organisms Primary
Producer
Grasses
Primary
Secondary ThirdConsumer Consumer Order
Consumer
X
Rabbits
X
Snakes
X
Owls
X
X
X
X
X
X
X
X
Humans
Bacteria
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.