Download Chapter 3: Ecosystems: What Are They and How Do They Work

Chapter 3: Ecosystems: What Are They and How Do They Work?
Case Study: Have you thanked the insects today?
Insects have a bad reputation but perform many beneficial services for the environment. Many
plants need insects to pollinate their flowers. Insects eat other insects controlling population size. They
have existed at least 400 million years, reproduce quickly, and rapidly develop new genetic traits. We
need to understand that insects play an important role in the environment and are needed by most land
organisms to survive. (Ex. “The Bee Movie”)
I.
The Nature of Ecology
a. Ecology is a study of connections in nature.
i. How organisms interact with one another and with their nonliving environment.
ii. Organisms, the different forms of life on earth, can be classified into different
species based on certain characteristics.
b. Case Study : Which species run the world?
i. Multitudes of tiny microbes such as bacteria, protozoa, fungi, and yeast help
keep us alive.
ii. Harmful microbes are the minority.
iii. Soil bacteria convert nitrogen gas to a usable form for plants.
iv. They help produce foods (bread, cheese, yogurt, beer, wine).
v. 90% of all living mass.
vi. Helps purify water, provide oxygen, breakdown waste.
vii. Lives beneficially in your body (intestines, nose).
c. Populations, Communities, and Ecosystems
i. Members of a species interact in groups called populations.
ii. Populations of different species living and interacting in an area form a
community.
iii. A community interacting with its physical environment of matter and energy is
an ecosystem.
II. THE EARTH’S LIFE SUPPORT SYSTEMS
a. The biosphere consists of several physical layers that contain:
i. Air
ii. Water
iii. Soil
iv. Minerals
v. Life
b. Biosphere
i. Atmosphere
ii. Membrane of air around the planet.
iii. Stratosphere
iv. Lower portion contains ozone to filter out most of the sun’s harmful UV
radiation.
v. Hydrosphere
vi. All the earth’s water: liquid, ice, water vapor
vii. Lithosphere
viii. The earth’s crust and upper mantle.
c. What sustains life on Earth?
i. Solar energy, the cycling of matter, and gravity sustain the earth’s life.
d. What happens to Solar Energy reaching the Earth?
i. Solar energy flowing through the biosphere warms the atmosphere, evaporates
and recycles water, generates winds and supports plant growth.
III. Ecosystem Components
a. Life exists on land systems called biomes and in freshwater and ocean aquatic life zones.
b. Nonliving and Living Components of Ecosystems
i. Ecosystems consist of nonliving (abiotic) and living (biotic) components.
c. Factors That Limit Population Growth
i. Availability of matter and energy resources can limit the number of organisms in
a population.
ii. The physical conditions of the environment can limit the distribution of a
species.
d. Producers
i. Most producers capture sunlight to produce carbohydrates by photosynthesis:
ii.
e.
iii. Chemosynthesis:
1. Some organisms such as deep ocean bacteria draw energy from
hydrothermal vents and produce carbohydrates from hydrogen sulfide
(H2S) gas .
iv. Photosynthesis
1. Chlorophyll molecules in the chloroplasts of plant cells absorb solar
energy.
2. This initiates a complex series of chemical reactions in which carbon
dioxide and water are converted to sugars and oxygen.
Consumers
i. Consumers (heterotrophs) get their food by eating or breaking down all or parts
of other organisms or their remains.
1. Herbivores
a. Primary consumers that eat producers
2. Carnivores
a. Primary consumers eat primary consumers
b. Third and higher level consumers: carnivores that eat
carnivores.
f.
g.
ii. Omnivores
1. Feed on both plant and animals.
Decomposers and Detritivores
i. Decomposers: Recycle nutrients in ecosystems.
ii. Detrivores: Insects or other scavengers that feed on wastes or dead bodies.
Aerobic and Anaerobic Respiration
i. Organisms break down carbohydrates and other organic compounds in their
cells to obtain the energy they need.
ii. This is usually done through aerobic respiration.
1. The opposite of photosynthesis
iii. Anaerobic respiration or fermentation:
1. Some decomposers get energy by breaking down glucose (or other
organic compounds) in the absence of oxygen.
2. The end products vary based on the chemical reaction:
a. Methane gas
b. Ethyl alcohol
c. Acetic acid
d. Hydrogen sulfide
IV. Two Secrets of Survival: Energy Flow and Matter Recycle
a. Biodiversity Loss and Species Extinction: Remember HIPPO
i. H for habitat destruction and degradation
ii. I for invasive species
iii. P for pollution
iv. P for human population growth
v. O for overexploitation
b. Biodiversity provides us with:
i. Natural Resources (food water, wood, energy, and medicines)
ii. Natural Services (air and water purification, soil fertility, waste disposal, pest
control)
iii. Aesthetic pleasure
c. Goals, strategies and tactics for protecting biodiversity
d. Energy flow in ecosystems
i. Food chains and webs show how eaters, the eaten, and the decomposed are
connected to one another in an ecosystem.
ii. In accordance with the 2nd law of thermodynamics, there is a decrease in the
amount of energy available to each succeeding organism in a food chain or web.
iii. Ecological efficiency: percentage of useable energy transferred as biomass from
one trophic level to the next.
iv. Gross primary production (GPP)
1. Rate at which an ecosystem’s producers convert solar energy into
chemical energy as biomass.
v. NPP = GPP – R
1. Rate at which producers use photosynthesis to store energy minus the
rate at which they use some of this energy through respiration (R)
What are nature’s three most productive and three least productive systems?
e. Soil: Renewable Resource
i. Soil is a slowly renewed resource that provides most of the nutrients needed for
plant growth and also helps purify water.
1. Soil formation begins when bedrock is broken down by physical,
chemical and biological processes called weathering.
2. Mature soils, or soils that have developed over a long time are arranged
in a series of horizontal layers called soil horizons.
ii. Layers of Mature Soil
1. Infiltration: the downward movement of water through soil.
2. Leaching: dissolving of minerals and organic matter in upper layers
carrying them to lower layers.
3. The soil type determines the degree of infiltration and leaching.
f. Matter Cycling in Ecosystems
i. Nutrient Cycles: Global Recycling
1. Global Cycles recycle nutrients through the earth’s air, land, water, and
living organisms.
2. Nutrients are the elements and compounds that organisms need to live,
grow, and reproduce.
3. Biogeochemical cycles move these substances through air, water, soil,
rock and living organisms.
ii. Water Cycle (See Class Activity)
iii. Carbon Cycle (See Class Activity)
iv. Nitrogen Cycle (See Class Activity)
v. Phosphorous Cycle (see class activity)
vi. Sulfur Cycle (See Class Activity)
vii. The Gaia Hypothesis:
Is the Earth Alive?
1. Some have proposed that the earth’s various forms of life control or at
least influence its chemical cycles and other earth-sustaining processes.
a. The strong Gaia hypothesis: life controls the earth’s lifesustaining processes.
b. The weak Gaia hypothesis: life influences the earth’s lifesustaining processes.
viii. HOW DO ECOLOGISTS LEARN ABOUT ECOSYSTEMS?
1. Ecologists go into ecosystems to observe, but also use remote sensors
on aircraft and satellites to collect data and analyze geographic data in
large databases.
a. Geographic Information Systems
b. Remote Sensing
2. Ecologists also use controlled indoor and outdoor chambers to study
ecosystems
3. We need baseline data on the world’s ecosystems so we can see how
they are changing and develop effective strategies for preventing or
slowing their degradation.
a. Scientists have less than half of the basic ecological data needed
to evaluate the status of ecosystems in the United Sates (Heinz
Foundation 2002; Millennium Assessment 2005).