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Chapter 3
The Biosphere
Chapter 3
The Biosphere
Chapter 3
The Biosphere
3-1 What is Ecology
Objectives• Identify the levels of organization
that ecologists study
• Describe the methods used to study ecology
Ecology• The scientific study of interactions
among organisms and between their environment
Biosphere• The portion of the planet which all
life exists
Levels of Organization • To understand relationships within
the biosphere ecologists ask questions about events and organisms that range in complexity from single individuals to the entire biosphere
• Studies can focus on…
Species• A group of organisms similar to
one another that can breed together
Populations• Groups of individuals that belong
to the same species and live in the same area
Communities• Assemblages of different
populations that live in a particular place together with their non-living physical environment
Ecosystem• Collection of all the organisms
that live in a particular place, together with their non-living environment
Biome• A group of ecosystems that have
the same climate and similar dominant communities
Ecological Methods1. Observing
2. Experimentation
3. Modeling
3 – 2 Energy Flow
Objectives• Identify the source of energy for
life processes
• Trace the flow of energy through living systems
• Evaluate the efficiency of energy transfer among organisms in an ecosystem
Producers• Sunlight is the main energy
source for life on Earth
• Some types of organisms rely on the energy stored in organic chemical compounds
Producers (autotrophs)• Use energy from the environment
to make their own food
Ex.) plants, some algae, certain types of bacteria
Photosynthesis• Process that converts light
energy, carbon dioxide and water into oxygen, sugars and starches
Chemosynthesis• The process that converts
chemical energy into carbohydrates
Consumers (heterotrophs)• Organisms that rely on other
organisms for their energy and food supply
Herbivores• Eat plants
Carnivores• Eat animals
Detritivores• Feed on plant and animal remains
and other dead matter
Ex.) mites, earthworms, snails, crabs
Decomposers• Break down organic matter
• Ex.) fungi, bacteria
Feeding Relationships• Energy flows through an
ecosystem in one direction, from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers)
Food Chain• A series of steps in which
organisms transfer energy by eating or being eaten
Food Web• A network of complex interactions
formed by the feeding relationships among the various organisms in an ecosystem
Trophic Levels
• Each step in a food chain or food web
1st – Producers
2nd – 3rd or higher – consumers
• Each consumer depends on the trophic level below it for energy
Ecological Pyramid• A diagram that shows the relative
amounts of energy or matter contained within each trophic level in a food chain or food web
Energy Pyramid• A diagram that shows the relative
amounts of energy available of each level
• Only about 10% of energy available within one trophic level is transferred to organisms at the next trophic level
Biomass Pyramid• Represent the amount of food
available for each trophic level
biomass• The total amount of living tissue
within a given trophic level
Pyramid of numbers• Shows the relative number of
individual organisms at each trophic level
3 – 3 Cycles of Matter
Objectives• Describe how matter cycles among
the living and nonliving parts of an ecosystem
• Explain why nutrients are important in living systems
• Describe how the availability of nutrients affects the productivity of ecosystems
• Energy is crucial to an ecosystem, but organisms need more than that to survive
• They also need
• Water
• Minerals/nutrients
• Oxygen
• Carbon
• Nitrogen
• Phosphorus
Recycling in the Biosphere
• Unlike the one way flow of energy, matter is recycled within and between ecosystems
Evaporation• The process by which water
changes from liquid form to an atmospheric gas
Transpiration• The process by which water can
enter the atmosphere by evaporating from leaves of plants
Condensation• Forming Clouds
Precipitation• When water returns to the earths
surface
Nutrients• All the chemical substances that an
organism needs to live• Every living organism needs
nutrients to grow and carry out essential life functions. Like water; nutrients are passed between organisms and the environment through cycles
The Carbon cycle• There are 4 different kinds of
processes involved in the carbon cycle:
1. Biological processes
2. Geochemical processes
3. Mixed biogeochemical processes
4. Human activity
The Nitrogen Cycle• All organisms require nitrogen to
make amino acids, which in turn are used to build proteins
• Many different forms of nitrogen occur naturally in the biosphere
• Although nitrogen gas is the most abundant form of nitrogen on Earth, only certain types of bacteria can use this form directly
Nitrogen fixation• Process of converting nitrogen
gas into useful forms
The Phosphorus Cycle• Phosphorus is essential to living
organisms because it forms part of important life sustaining molecules such as DNA and RNA
• Unlike carbon, oxygen and nitrogen, phosphorus does not enter the atmosphere
• Phosphorus remains mostly on land in rock and soil minerals, and in ocean sediments
• As the rocks and sediments gradually wear down, phosphate is released
• Plants absorb phosphate then it moves to the rest of the ecosystem
Nutrient Limitation• Ecologists are often interested in
the primary productivity of an ecosystem
Primary Productivity• The rate at which organic matter
is created by producers
• If a nutrient is in short supply, it will limit an organisms growth
Limiting Nutrient• Single nutrient that either is
scarce or cycles very slowly, limiting the growth of organisms in an ecosystem
