Organisms and Species
• Organisms, the different forms of life on earth,
can be classified into different species based on
certain characteristics.
Figure 3-3
Species Diversity and Niche
Structure: Different Species Playing
Different Roles
• Biological communities differ in the types and
numbers of species they contain and the
ecological roles those species play.
– Species diversity: the number of different species it
contains (species richness) combined with the
abundance of individuals within each of those species
(species evenness).
Indicator Species:
Biological Smoke Alarms
• Species that serve as early warnings of
damage to a community or an ecosystem.
– Presence or absence of trout species because
they are sensitive to temperature and oxygen
levels.
Case Study: Indicator Species
Why are Amphibians Vanishing?
• Frogs serve as indicator species because different
parts of their life cycles can be easily disturbed.
Figure 7-3
Case Study:
Why are Amphibians Vanishing?
•
•
•
•
•
•
•
•
Habitat loss and fragmentation.
Prolonged drought.
Pollution.
Increases in ultraviolet radiation.
Parasites.
Viral and Fungal diseases.
Overhunting.
Natural immigration or deliberate introduction of
nonnative predators and competitors.
Some organisms play big roles
• Keystone Species = has
a strong or widereaching impact far out
of proportion to its
abundance
• Removal of a keystone
species has substantial
ripple effects
– Alters the food chain
Foundation Species:
Other Major Players
• Expansion of keystone species category.
• Foundation species can create and enhance
habitats that can benefit other species in a
community.
– Elephants push over, break, or uproot trees,
creating forest openings promoting grass growth
for other species to utilize.
Succession
Definition
• The process where plants & animals of
a particular area are replaced by other
more complex species over time.
Primary vs. Secondary
• Primary begins with a lifeless area where there is
no soil (ex. bare rock). Soil formation begins
with lichens or moss.
Climax Communities
• The area dominated by a few, long-lived
plant species.
Introduced (invasive) species
•
•
•
•
•
They displace native species
They lower biodiversity
The can adapt very quickly to local habitats
They contribute to habitat fragmentation
They can reproduce very quickly
Controlling invasive species
• Techniques to control invasive species
– Remove manually
– Toxic chemicals
– Drying them out
– Depriving of oxygen
– Stressing them
• Heat, sound, electricity, carbon dioxide, ultraviolet
light
Prevention, rather than control, is the best
policy
Changed communities need to be
restored
• Ecological restoration = returning an area to
unchanged conditions
– Informed by restoration ecology = the science of
restoring an area to the condition that existed
before humans changed it
– It is difficult, time-consuming, expensive
– Best to protect natural systems from degradation
in the first place
Restoration efforts
• Prairie Restoration
– Native species replanted and invasive
species controlled
• The world’s largest project: Florida
Everglades
– Depletion caused by flood control
practices and irrigation
– Populations of wading birds dropped 9095%
– It will take 30 years, and billions of dollars
• The U.S. is trying to restore Iraq marshes
Question of the Day
• Which of the following would be considered
an indicator species?
– A. Elephant
– B. Oak tree
– C. Bald Eagle
– D. Leopard Frog
– E. Box Turtle
Measurement of Biodiversity
• Genetic tests
• count/release
• tagging.
The Gaia Hypothesis:
Is the Earth Alive?
• Some have proposed that the earth’s various
forms of life control or at least influence its
chemical cycles and other earth-sustaining
processes.
– The strong Gaia hypothesis: life controls the
earth’s life-sustaining processes.
– The weak Gaia hypothesis: life influences the
earth’s life-sustaining processes.
CLIMATE: A BRIEF
INTRODUCTION
• Weather is a local area’s short-term physical
conditions such as temperature and precipitation.
• Climate is a region’s average weather conditions
over a long time.
– Latitude and elevation help determine climate.
Earth’s Current Climate Zones
Figure 5-2
BIOMES:
CLIMATE AND LIFE ON LAND
• Different climates lead to different
communities of organisms, especially
vegetation.
– Biomes – large terrestrial regions characterized by
similar climate, soil, plants, and animals.
– Each biome contains many ecosystems whose
communities have adapted to differences in
climate, soil, and other environmental factors.
A variety of factors determine the
biome
• The biome in an area depends
on a variety of abiotic factors
– Temperature, precipitation,
atmospheric circulation, soil
• Climatographs
– A climate diagram showing
an area’s mean monthly
temperature and
precipitation
– Similar biomes occupy
similar latitudes
Earth’s Terrestrial Biomes
• Tropical Rain Forest • Desert
• Taiga (Northern
• Tundra
Boreal Forest)
• Temperate Deciduous Also considered:
Forest
• Mountains
• Temperate Rain Forest • Polar Ice Caps
• Temperate Grassland
• Tropical Savannah
• Chaparral
Desert
• The evaporation is greater than the
precipitation (usually less than 25
cm). Covers 30% of the earth.
DESERT BIOMES
• Variations in
annual
temperature (red)
and precipitation
(blue) in tropical,
temperate and
cold deserts.
Figure 5-12
FOREST BIOMES
• Forests have enough precipitation to support
stands of trees and are found in tropical,
temperate, and polar regions.
FOREST BIOMES
• Variations in
annual temperature
(red) and
precipitation (blue)
in tropical,
temperate, and
polar forests.
Figure 5-19
Taiga (evergreen coniferous forest)
• Just south of the tundra (northern part of N.
America), it covers 11% of earth’s land. Its
winters are long, dry & cold. Some places have
sunlight 6 to 8 hours a day. The summers are
short and mild, w/ sunlight 19 hours a day.
MOUNTAIN BIOMES (Taiga)
• High-elevation
islands of
biodiversity
• Often have snowcovered peaks that
reflect solar
radiation and
gradually release
water to lowerelevation streams
and ecosystems.
Figure 5-25
Tropical Rain Forest
• Tropical rain forests
have heavy rainfall
and a rich diversity
of species.
– Found near the
equator.
– Have year-round
uniformity warm
temperatures and
high humidity.
Figure 5-20
Grassland
• The rainfall is erratic & fires are
common. It has & shrubs that are
good for grazing animals.
GRASSLANDS AND CHAPARRAL
BIOMES
• Variations in
annual
temperature
(red) and
precipitation
(blue).
Figure 5-14
Savanna
• The tropical & subtropical grassland. It
is warm all year long with alternating
wet & dry seasons.
Chaparral (temperate grassland)
• These are coastal areas. Winters are mild
& wet, w/ summers being long, hot, &
dry.
Chaparral
• Chaparral has a
moderate
climate but its
dense thickets
of spiny shrubs
are subject to
periodic fires.
Figure 5-18
Temperate Grasslands
• The cold winters
and hot dry
summers have deep
and fertile soil that
make them ideal for
growing crops and
grazing cattle.
Figure 5-15
Tundra (polar grasslands)
• Covers 10% of earth’s land. Most of the year,
these treeless plains are bitterly cold with ice
& snow. It has a 6 to 8 week summer w/
sunlight nearly 24 hours a day.
Polar Grasslands
• Polar grasslands
are covered with
ice and snow
except during a
brief summer.
Figure 5-17
Natural Capital Degradation
Grasslands
Conversion to cropland
Release of CO2 to atmosphere
from grassland burning
Overgrazing by livestock
Oil production and off-road
vehicles in arctic tundra
Fig. 5-27, p. 123
Natural Capital Degradation
Forests
Clearing for agriculture, livestock
grazing, timber, and urban
development
Conversion of diverse forests to tree
plantations
Damage from off-road vehicles
Pollution of forest streams
Fig. 5-28, p. 124
Question of the day.
An ecosystem has an ecological efficiency of
10 percent. If the tertiary consumer level has
1 kcal of energy, how much energy did the
producer level contain?
A. 100 kcal
B. 1000 kcal
C. 10,000 kcal
D. 90 kcal
E. 900 kcal
steady states
• Steady state- in a system, when input
equals output it is said to be in a steady
state.
Systems are active
• Dynamic equilibrium = system
processes move in opposing
directions at equivalent rates,
balancing their effects
• Homeostasis = a system maintains
constant or stable internal conditions
• Emergent properties = system
characteristics not evident in the
components alone
– “The whole is more than the sum
of the parts”
It is hard to fully understand systems; they connect to other systems and do not
have sharp boundaries
Systems are perceived in various ways
• Categorizing environmental systems helps make
Earth’s dazzling complexity comprehensible
• For example, the earth consists of structural
spheres
–
–
–
–
Lithosphere = rock and sediment
Atmosphere = the air
Hydrosphere = liquid, solid or vapor water
Biosphere = all the planet’s living organisms and the
abiotic portions of the environment
• Boundaries overlap, so the systems interact
Ecosystems
• Ecosystem = all organisms and nonliving entities that
occur and interact in a particular area at the same
time
– Includes abiotic and biotic components
– Energy flows and matter cycles among these components
• Biological entities are highly intertwined with
chemical and physical entities
– Interactions and feedback loops
Energy is converted to biomass
• Primary production = conversion of solar energy
to chemical energy by autotrophs
• Gross primary production (GPP) = assimilation of
energy by autotrophs
• Net primary production (NPP) = energy
remaining after respiration, and is used to
generate biomass
– Available for heterotrophs
• Secondary production = biomass generated by
heterotrophs
• Productivity = rate at which ecosystems generate
biomass
Ecosystem Productivity
Net primary productivity (NPP)- The
energy/biomass that remains after
respiration (R) and is available by
heterotrophs/consumers in that
ecosystem
NPP = GPP – R
Net primary productivity of various
ecosystems
High net primary productivity = ecosystems whose plants rapidly convert solar
energy to biomass
NPP variation causes global geographic
patterns
NPP increases with temperature and precipitation on land, and with light and
nutrients in aquatic ecosystems
Nutrients can limit productivity
• Nutrients = elements and compounds required for survival that
are consume by organisms
• Macronutrients = nutrients required in relative large amounts
– Nitrogen, carbon, phosphorus
• Micronutrients = nutrients needed in smaller amounts
• Stimulate plant production
• Nitrogen and phosphorus
are important for plant and
algal growth
Dramatic growth of algae in water
treated with phosphate
Nutrient runoff is devastating aquatic
systems
• Dead zones of water result from nutrient pollution from
farms, cities, and industry
• Pollution and human impact have devastated fisheries and
altered aquatic ecosystems
• Scientists are investigating innovative and economical ways to
reduce nutrient runoff
Phytoplankton blooms off the
Louisiana coast
The Gulf of Mexico from a systems
perspective
• Nutrients from fertilizer enter the
Mississippi River from Midwestern
farms
• Fertilizer use has increased, which
causes….
• Phytoplankton to grow, then…
• Bacteria eat dead phytoplankton
and wastes and deplete oxygen,
causing…
• Fish and other aquatic organisms
to suffocate
Ecosystems integrate spatially
• Ecosystems vary greatly in size
• The term “ecosystem” is most often applied to
self-contained systems of moderate geographic
extent
• Adjacent ecosystems may share components
and interact
• Ecotones = transitional zones between two
ecosystems in which elements of different
ecosystems mix
Landscape ecology
• Landscape ecology = the study of landscape structure and how
it affects the abundance, distribution, and interaction of
organisms
– Helpful for sustainable regional development
• Patches = form the landscape, and are distributed spatially in
complex patterns (a mosaic)
• Landscape = larger than an ecosystem and smaller than a
biome
Metapopulations and conservation
biology
• Metapopulation = a network of subpopulations
– Most members stay within patches but may move
among patches or mate with those of other patches
– Individuals in small patches risk extinction
• Conservation biologists = study the loss,
protection, and restoration of biodiversity
• Habitat fragmentation = breaking habitat into
small, isolated patches due to human impact
– Corridors of habitat can link patches