Ch 2.Ecosystems

What they are?
Plum Island
The State of the Nation’s Ecosystems: Measuring the
lands, waters, and living resources of the United States.
 Six major types of
 Coasts and oceans
 Farmlands
 Forests
 Fresh waters
 Grasslands and
 Urban and suburban areas
 Indicators
 System dimensions
 Ecosystem extent
 Fragmentation and landscape pattern
 Chemical conditions
 Nutrients, Carbon and oxygen
 Contaminants
 Physical
 Biological components
 Plants and animals
 Communities
 Ecological productivity
 Human uses
 Food, fiber and water
 Recreation and other services
1) What are Ecosystems?
Ecosystems are the biotic and abiotic factors in a specified area
that interact with one another.
 Understanding the interaction of the biotic and abiotic factors in
an ecosystem can help us to see why particular human activities
may be a problem for human survival.
 Example: The loss of ozone in the stratosphere increases the
quantity of UV radiation on the surface of the planet. In the same
way that humans experience sunburn from too much sun
exposure, so do plants. Excessive UV may damage or destroy plant
protein and DNA, killing the plant.
Important ecological terms
 Biotic communities: All the populations of different plants,
animals and microbes occupying a given area.
 Abiotic factors: All the factors of the physical environment:
moisture, temperature, light, wind, pH, type of soil, salinity,
Important ecological terms
 Ecology: Study of ecosystems and the interactions that occur
among organisms and between organisms and their
 Ecologist: The investigators who conduct ecological studies
Important ecological terms
 Species: All the members of a specific kind of plant, animal
or microbe; a kind given by similarity of appearance or
capacity for interbreeding and producing fertile offspring
 Populations: All the members of a particular species
occupying a given area.
 Associations: A plant community with a definite composition,
uniform habitat characteristics, and uniform plant growth.
Important ecological terms
 Ecotone: transitional region that shares many of the species
and characteristics of two ecosystems. It also includes unique
Fig. An ecotone may create a unique habitat with specialized species not found in either of the
ecosystems bordering it.
Important ecological terms
 Landscapes: group of interacting ecosystems in a particular
area. A barrier island, a saltwater bay, constitute a landscape
Fig. Ecosystems are not isolated from one another. One ecosystem blends into the next through a
transitional region, an ecotone, which contains many species common to the two adjacent
Important ecological terms
 Biomes: grouping of all the ecosystems of a similar type. I.e.
tropical rain forests, grasslands, deserts, etc.
 Biosphere: All the species on Earth, along with all the
environments, make up one vast ecosystem, the Biosphere.
2) The structure of Ecosystems
Feeding relationships
Trophic structure
Trophic structure
Detritus feeders and
Trophic structure
Producers: capture energy from the Sun or chemical reactions
to convert carbon dioxide, an inorganic molecule into organic
•What is the difference between
organic and inorganic molecules?
• Producers are also known as
autotrophs. What is an autotroph?
Trophic structure
2) Consumers:
Primary consumers:
feed directly on
producers (herbivores)
Secondary consumers:
feed on primary
consumers (carnivores)
Omnivores: feed on
both plants and animals
Consumers are also known as heterotrophs. What is an heterotroph?
The Structure of Ecosystems
Feeding relationships among
Predator/prey relationships: any relationship
in which one organism feeds on another.
Parasites: plants or animals that become
intimately associated with their “prey” and
feed on it over an extended period of
time without killing it. The organism that
is fed upon is called host.
Pathogens: bacteria and viruses that cause
Trophic structure
3) Detritus feeders and decomposers:
Organisms that feed on death plants or animals,
feaces, etc.
 Primary detritus feeders: organisms that feed
directly on detritus
 Decomposers: secrete digestive enzymes that break
down dead matter. I.e. bacteria and fungi.
 Secondary detritus feeders: feed on primary
detritus feeders. I.e. protozoans, mites, insects, and
 Are detritus feeders autotrophs or heterotrophs?
Trophic categories
Photosynthetic green
(fungi and
Primary detritus
Secondary and
higher orders of
detritus feeders
Higher orders of
Parasites: plants or
2) The structure of Ecosystems
Feeding relationships
Trophic relationships
Trophic relationships
a. Food chains: feeding pathways
 Food chains are a description of who eats whom.
 Predator-prey and host-parasite describe specific feeding
b. Food webs: complexes of feeding relationships.
c. Trophic Levels or Feeding Levels
 All producers belong to the first trophic level.
 All herbivores (primary consumers) are on the second trophic level.
 All primary carnivores (secondary consumers) are on the third
trophic level.
Trophic Relationships
Food chain
Food web
2) The structure of Ecosystems
Feeding relationships
Biomass and biomass pyramids
Biomass and biomass pyramid
 All organic matter can be defined as biomass
 All biomass can be arranged into a feeding relationship with the
producers on the first trophic level.
Biomass and biomass pyramid
 On average, 10% of the energy from one trophic level
moves to the next trophic level.
2) The structure of Ecosystems
Non-feeding relationships
Non feeding relationships
Mutually Supportive Relationships: mutualism.
Competitive Relationships
How are competitive relationships reduced?
Habitat: place
Niche: role
What happens when competition is not reduced?
Competitive exclusion principle
 Conditions: abiotic factors that vary in space and time, but
are not used up or made unavailable to other species.
i. e. temperature, wind, pH, salinity, fire
 Resources: factors (biotic or abiotic) that are consumed by
i.e. water, chemical nutrients, light, oxygen
2) The Structure of Ecosystems
Limiting Factors
 Factors that limit growth, reproduction or even survival of a
 Biotic or abiotic
 Basic items include temperature, light, oxygen, carbon dioxide,
and precipitation.
 Only one limiting factor need be out of its optimum range to
cause stress for an organism.
Optimum, zones of stress and limits of
 Optimum: level at which an organisms do best.
 Range of tolerance: the entire span that allows any growth at all.
 Limits of tolerance: points at the high and low ends of the range of tolerance
 Zones of stress: between the optimal range and the high or low limit of
Range of tolerance
Limiting factors
 Law of Limiting Factors - Quantities of any single factor
above or below optimum levels necessary for organism
growth, reproduction, or survival will limit growth,
reproduction, or survival.
 Synergistic effects (synergism): two or more factors
interacting in a way that causes an effect much greater than
one would anticipate from the effects of each of the two
acting separately.
3) Global biomes
The Role of Climate
The role of climate
 Climate: describes the average temperature and precipitation of a
given region
Weather the daily variations in temperature and precipitation
Vary widely in different parts of the world.
A given climate supports only those species that find the temperature
and precipitation levels optimal or within ranges of tolerance.
Temperature and precipitation combine to create the world's biomes.
Activity: Describe how ecosystems change as
temperature and precipitation change:
while temperature
is held constant
a.Vary temperature
while precipitation is
held constant
Activity: Describe the effects of altitude and
3) Global biomes
MicroclimateSpecific sites with temperature and moisture
conditions significantly different from the overall or average
climate of the region in which it is located.
Microclimates. Abiotic factors such as terrain, wind, and type of soil create different
microclimates by influencing temperature and moisture in localized areas
4) Implications for humans
The three revolutions:
Neolithic Revolution
a. Development of agriculture
b. Required permanent or long term settlements and specialized skills
c. Allowed for the initial increase in human population reliable food.
Industrial Revolution
a. Created the modern world
b. Energized by fossil fuels (initially timber). resulted in the concentration of waste
d. Created even greater increase in human population size because of the
specialization of the workforce and the replacement of animal/human power with
fossil fuels.
Environmental Revolution
a. Need to create sustainable human systems
b. Need to create systems in which waste products are not concentrated (pollution),
and wastes are resources.