Community ecosystem ecology_access(1)Presentation Transcript
Chapter 15: Ecosystems and
Organisms and their environments
by Mark Manteuffel, St. Louis Community College
What are ecosystems?
A community of biological organisms plus
the non-living components with which the
An ecosystem is all of the living organisms
in a habitat as well as the physical
Ecosystems are found not just in obvious
places such as ponds, deserts, and
tropical rainforests but also in some
unexpected places, like the digestive
tracts of organisms or the shell of a beetle.
A variety of biomes occur
around the world, each
determined by temperature
What is the average temperature?
What is the average rainfall (or other
Is the temperature relatively constant or
does it vary seasonally?
Is the rainfall relatively constant or does it
Temperature and precipitation dictate:
• Primary productivity levels
the amount of organic matter produced
The numbers and types of primary
• are the chief determinants of the amount and
breadth of other life in the region.
Biomes are the major ecological
communities of earth, characterized
mostly by the vegetation present.
Different biomes result from differences in
temperature and precipitation, and the
extent to which they vary from season to
Global air circulation
patterns create deserts and
Global patterns of weather are largely
determined by the earth’s round shape.
Solar energy hits the equator at a more
direct angle than at the poles, leading to
warmer temperatures at lower latitudes.
This temperature gradient generates
atmospheric circulation patterns that result
in heavy rain at the equator and many
deserts at 30° latitude.
influences the weather.
Is it warmer or cooler in urban
areas relative to nearby rural
“Urban Heat Islands”
Why is it so windy on streets
with tall buildings?
Local features of topography influence the
With higher altitude, the temperature drops.
On the windward side of mountains, rainfall is
high; on the backside, descending air
reduces rainfall, causing rain shadow
Urban development increases the
absorption of solar energy, leading to
higher temperatures, and creates wind
near the bottom of tall buildings.
Ocean currents affect the
Global Patterns of Circulation in
Why do beach communities
have milder weather than more
Water’s Capacity to Absorb and Hold Heat
Oceans have global circulation patterns.
Disruptions in these patterns occur every
few years and can cause extreme climate
disruptions around the world.
Chains or Webs?
• Pathway from photosynthetic producers
through the various levels of animals
• Involve harvesting energy from multiple stops
in the food chain
Losses at every “step” in a food chain
Inefficiency of energy transfers
Energy from the sun passes through an
ecosystem in several steps.
First, it is converted to chemical energy in
Herbivores then consume the primary
producers, the herbivores are consumed
by carnivores, and the carnivores, in turn,
may be consumed by top carnivores.
Detritivores and decomposers extract
energy from organic waste and the
remains of organisms that have died.
At each step in a food chain, some usable
energy is lost as heat.
Energy pyramids reveal the
inefficiency of food chains.
Where does the rest go?
Expended in cellular respiration or lost as
Why are big, fierce animal
species so rare in the world?
Energy from the sun passes through an
ecosystem in several steps known as
Energy pyramids reveal that the biomass
of primary producers in an ecosystem
tends to be far greater than the biomass of
The biomass transferred at each step
along the food chain tends to be only
about 10% of the biomass of the
organisms being consumed, due to
energy lost in cellular respiration.
As a consequence of this inefficiency,
food chains rarely exceed four levels.
Essential chemicals cycle
The Recycling of Molecules
Each chemical is stored in a non-living part of
Organisms acquire the chemical from the
The chemical cycles through the food chain.
Eventually, the chemical is returned to the
The Three Most Important
Why are global CO2 levels
Global CO2 levels are rising in
general, but they also exhibit a sharp
rise and fall within each year.
Nitrogen is like a bottleneck
limiting plant growth.
Chemicals essential to life—including carbon,
nitrogen, and phosphorus—cycle through
They are usually captured from the
atmosphere, soil, or water by growing
organisms; passed from one trophic
level to the next as organisms eat
other organisms; and returned to the
environment through respiration,
decomposition, and erosion.
These cycles can be disrupted as human
activities significantly increase the
amounts of the chemicals utilized or
released to the environment.
Interacting species evolve together.
Causes organisms to become better
adapted to their environment
Does not distinguish between biotic and
abiotic resources as selective forces
In producing organisms better adapted to
their environment, natural selection does
not distinguish between biotic and abiotic
resources as selective forces.
Each species’ role in a
community is defined by its
More than just a place for living, a niche is a
complete way of living.
“You can’t always get what you want.”
• the full range of environmental conditions
under which a species can live
• where and how a species is actually living
A population of organisms in a community
fills a unique niche, defined by the manner
in which they utilize the resources in their
Organisms do not always completely fill
their niche; competition with species that
have overlapping niches can reduce their
Competition can be hard to see,
but it still influences community
Populations with completely overlapping
niches cannot coexist forever.
Competition for resources occurs until one or
both species evolve in ways that reduce the
competition, through character displacement,
or until one becomes extinct in that location.
adaptation in both predators
and their prey.
One of the most important forces shaping
the composition and abundance of
species in a community
Why do exotic species often flourish
when released into novel habitats,
even though natural selection has not
adapted them to this new
Prey Adaptations for Reducing
There are two broad categories of
defenses against predators:
Include Mechanical, Chemical,
Warning Coloration, and
1) Mechanical Defenses
2) Chemical Defenses
3) Warning Coloration
Include both seemingly passive
and active behaviors: hiding or
escaping, or alarm calling or
Predator adaptations for
Predators and their prey are in an
evolutionary arms race.
As physical and behavioral features
evolve in prey species to reduce their
predation risk, predators develop more
effective and efficient methods of
The coevolutionary process can result in
brightly colored organisms, alarm calling,
and many types of mimicry.
Parasitism is a form of
Parasites have some unique features and
face some unusual challenges:
• The parasite generally is much smaller than its
host and stays in contact with the host for
extended periods of time.
• Complicated life cycles as means of getting from
host to host.
Case 1: Parasites can induce foolish,
fearless behavior in their hosts.
Rats and cats
Case 2: Parasites can induce inappropriate
aggression in their hosts.
Case 3: Parasites can induce bizarre
and risky behavior in their hosts.
The lancet fluke
Parasitism is a symbiotic relationship in
which one organism benefits while the
other is harmed.
Parasites face some unusual challenges
relative to other predators, particularly how
to get from one individual host to another,
and some complex parasite life cycles
Not all species interactions are
negative: mutualism and
Not all species interactions are combative.
Evolution produces beneficial species
interactions as well, including mutualism,
in which both species benefit from the
interaction, and commensalism, in which
one species benefits and the other is
neither harmed nor helped.
Many communities change
Much faster than primary succession
• life and soil are already present
Succession is the change in the species
composition of a community over time,
following a disturbance.
In primary succession, the process begins
in an area with no life present.
In secondary succession, the process
occurs in an area where life is already
But in both types, the process usually
takes place in a predictable sequence.
Some species are more
important than others within a
Keystone species have a relatively large
influence on which other species are
present in a community and which are not.
• Unlike other species, when a keystone
species is removed from the community, the
species mix changes dramatically.
• For this reason, preserving keystone
species is an important strategy in
maximizing the preservation of biodiversity.