Ecology and Sustainable Development Hand-outs Nurmukhanbetova G.A. Cand.Sc. (Biology)
Topic 4: Synecology – the ecology of communities.
The main idea: Note the way energy relationships determine the structure of ecosystems.
Lecture outline:
1.
Ecosystem structure: Habitat. Niche. Trophic levels.
2.
Three functional groups: Producers – Consumers - Decomposers
3.
Energy flow: Food chains. Lindeman’s rule of 10%
4.
Ecological pyramids: Numbers, Biomass, Energy
5.
Succession: Primary and Secondary Succession.
1.
Ecosystem structure: Habitat – Niche – Trophic levels
Community (Biocoenosis) – living organisms of different populations in the same area.
Ecosystem (Biogeocoenosis)
– an ecological unit that includes all the interacting parts (living organisms and the environment) in an area.
Ecosystem = the community + its physical environment
Example of a single forest: its climate, soil, trees, shrubs, bacteria, invertebrates, and vertebrates - make up one ecosystem. Each kind of organism in an ecosystem has a specific role.
Ecosystem structure:

Habitat (Where to live?) – a physical area in which an organism lives; different types of environment which provide food and shelter for living things.

Niche (How to live?) – the role played by a species in a biological community;
Niche – the total set of environmental factors that determine species distribution in an ecosystem.
An organism’s niche includes its habitat, feeding habits, reproductive behavior, and all other aspects of its biology.
Ecological niches of species living together can never overlap!

Trophic levels, or feeding levels – the relationship between what organism eats and what it is eaten in an ecosystem.
2.
Functional groups: Producers – Consumers - Decomposers
Trophic levels include three functional groups: Producers, Consumers and Decomposers

Producers – autotrophic organisms ( primary producers ), that make their own food by themselves, using solar (phototrophs) or chemical energy (chemotrophs)
Examples: plants, algae, photosynthetic bacteria (cyanobacteria – blue-green algae) and chemosynthetic bacteria
(nitrogen-fixing bacteria).
Autotroph – an organism that uses energy, such as light, to synthesize organic compounds from inorganic substances ( photosynthesis):
H
2
O + CO
2
+ Sun light energy

C n
(H
2
O) n
+ O
2
Water Carbon dioxide Sugar Oxygen
Primary productivity of the ecosystem – the rate at which solar energy is converted into organic compounds by producers (kcal/m 2 /yr).
Example: Although rain forests occupy only 5% of the earth’s surface, they account for ~30% of its productivity.

Consumers - heterotrophs, which include animals, protozoa, and fungi.
Heterotroph – an organism that cannot make its own food, so that it uses ready food (eat other organisms).
Producers

Primary consumer

Secondary consumer o Primary consumer – any organism that eats a producer. o Secondary consumer – an organism that eats a primary consumer.
Consumers are classified according to the type of food they eat:

Herbivores (grass-eating) – obtain their nutrients by eating producers (antelope, deer).

Carnivores (meat-eating) – obtain their nutrients by eating other consumers ( lions, eagles, cobras).

Omnivores (mixture food-eating) – obtain their nutrients by eating both producers and consumers (bears, humans).

Scavengers (dead organisms-eating) – consumers that feed on organisms that have recently died (vultures, crows).

Decomposers – heterotrophs, which include bacteria, fungi, that break down dead tissues and wastes into nitrogen, carbon, phosphorus, and other elements and compounds.
Cycle: Autotrophs then extract these materials from the soil and use them to manufacture food. Thus the process of decomposition recycles chemical nutrients, making them available to the producers again. This cycle is repeated over and over in the same ecosystem.
3.
Energy flow: Food chains. Lindeman’s rule of 10%
The lower trophic level of an ecosystem always contains more total energy than do higher trophic level.

Ecology and Sustainable Development Hand-outs Nurmukhanbetova G.A. Cand.Sc. (Biology)

Food chain – the specific sequence in which organisms obtain energy in an ecosystem.
Food chains usually have only 4 or 5 levels, but sometimes 8 - 9 trophic levels.
Food chain of fresh water ecosystem: Alga – Insect nymph – Fish – Otter – Bacteria.
Food chain of grassland ecosystem: Grass–Zebra– Lion – Vulture – Bacteria

Food webs – interrelated food chains in an ecosystem. A diagram of the feeding relationships among all the organisms in a single ecosystem looks like a web. Many consumers eat more than one type of food.
 R. Lindeman’s rule of 10% (1942):
Only the amount of 10% energy passes from one trophic level to the next one, and so is available to the higher levels.
4.
Ecological pyramids: Number, Biomass, Energy
Ecological Pyramids – a diagram of relationships in an ecosystem as a pyramid, in which the primary producer trophic level is at the base and the consumer level above it.
Pyramid models include 3 types: Numbers pyramids, Biomass pyramids and Energy pyramids.

Numbers Pyramid – compare the number of individuals at each trophic level (number/m 2 ).

Biomass Pyramid - compare the amount of biomass at each trophic level (g/m 2 ).
Biomass - is the total dry weight of the organisms in the ecosystem.
Example: Grassland biomass pyramid is right, Freshwater or marine biomass pyramid is inverted.
Detritus – mass of dead organic matter
Phytoplankton – microscopic algae suspended in lake or ocean water.
Zooplankton – microscopic animals suspended or swimming in waters of lakes or oceans.
Benthos – bottom dwellers (such as snails, burrowing worms and insect larvae, bacteria).

Energy Pyramid
– compare the total amount of energy, measured in kilocalories, in each trophic level (kcal/cm 2 /year).
Unlike numbers pyramids and biomass pyramids, energy pyramids are never inverted, because energy is always lost passing from one trophic level to the next higher.
5.
Succession: Primary and Secondary Succession.
Succession
– a gradual, sequential replacement of population in an area.
Pioneer species – first species to colonize a new habitat (for example, lichen).
o Primary Succession
– the sequential replacement of population in an area that has not previously supported life, such as bare rock or a sand dune. o Secondary Succession
– the sequential replacement of population in disrupted habitats that have not been totally stripped of soil and vegetation. The disruption may stem from a natural disaster, such a forest fire or volcanic eruption, or from human activity, such farming, logging, or mining.
Old-field succession
– a version of secondary succession – the replacement of population abandoned farm field .
Secondary succession in lakes: Lake can transform to marsh because of eutrophication
(“algal bloom”) – the increase of nutrients in an environment.
Key terms:
Synecology
Community
Ecosystem
Habitat
Niche
Trophic levels
Autotroph
Heterothroph
Producers
Consumers
Decomposers
Energy flow
Food chains
Food Webs
Herbivores
Carnivores
Omnivores
Scavengers
Ecological pyramids
Numbers pyramids
Biomass pyramids
Energy pyramids
Detritus
Phytoplankton
Zooplankton
Benthos
Lindeman’s rule of 10% (1942)
Primary productivity
Primary succession
Secondary succession
Questions for review:
1. Distinguish between habitat and a niche.
2. Why are primary producers an essential component of an ecosystem?
3. Give three examples of primary consumer and three examples of secondary consumer.
4. What is the function of a decomposer?
5. How does food chain differ from a food web?
6. Distinguish between numbers, biomass and energy pyramids. What is the rule of 10%?
7. How is interspecific competition related to the process of succession?
Make a synopsis: Daniel D. Chiras, “Environmental Science: Creating Sustainable Future”
1. Draw a graph of Food chain and Flow energy and biomass (p.73, fig. 5-8; p.75, fig. 5-10).
Critical Thinking (Writing an essay):
1.
What happens to the solar energy not stored by primary producers?
2.
How does the transfer of energy in an ecosystem fifer from the transfer of nutrients?
3.
Why is energy pyramids never inverted?
4.
Explain why farmers often grow up soybeans or other legume crops in the field after they have grown corn.
5. Build your own ecosystem in an aquarium or terrarium. Be sure to include a representative producer,
consumer, scavenger, and decomposer.