Bio464 Chapter 13 : Ecosystems Ecologyyy

Ecosystem ecology

1. CHAPTER 13: ECOSYSTEM ECOLOGY
13.1 Basic components of ecosystems:
basic processes
13.2 Trophic relationships
13.3 Primary and secondary
production
13.4 Production efficiency
13.5 Biogeochemical cycling

2. BASIC COMPONENTS OF ECOSYSTEMS
Producers
•autotrophs -pick up energy from the sun and
materials from the non living sources
•energy capturing green plants, algae, diatoms
Consumers
•heterotrophs –pick up energy and materials
by eating living matter
•Including decomposers
Inorganic and dead matter
•plant and consumers in soil matrix and aquatic
systems

3. MAIN PROCESSES IN ECOSYSTEMS
1) Energy flows : through
ecosystems
2) Chemical cycling : cycles
within them

5. LAW OF THERMODYNAMICS
FIRST LAW OF THERMODYNAMICS
Energy can be transferred or
transformed but neither created nor
destroyed.
SECOND LAW OF
THERMODYNAMICS
Every energy transfer or
transformation increases the
disorder (entropy) of the universe.

6. TROPHIC RELATIONSHIP
Energy and nutrients pass from :
primary producers -to primary
consumers -and then to
secondary consumers

7. FOOD CHAIN

8. FOOD CHAIN

9. DECOMPOSITION
1. Microflora
Bacteria, Fungi
2. Detritivores or detritus feeder
soil microfauna: protozoans
soil mesofauna: nematodes
soil macrofauna: earthworm
3. Microbivores
feeding on dead decomposer including bacteria
and fungi

10. ECOSYSTEM ENERGY BUDGETS
Sets the spending limit for the
energy budget of the entire
ecosystem
Only a small fraction of solar
energy actually strikes
photosynthetic organisms

11. PRIMARY AND SECONDARY PRODUCTIVITY
Primary productivity
•The amount of light energy converted to chemical energy
by autotrophs
•Light energy converted to product
Secondary productivity
•Amount of production/energy available to heterotrophs
•efficient for production of young and growth of new tissue

12. GROSS AND NET PRIMARY PRODUCTIVITY
GPP-energy (carbon) fixed via photosynthesis per unit time
NPP-energy (carbon) fixed via photosynthesis minus energy (carbon) lost via respiration per unit
time
NPP(Net primary productivity) = GPP (Gross primary productivity) –R(Respiration by autotroph)

13. SECONDARY PRODUCTIVITY
Amount of production/energy available to heterotrophs
1) Energy (in the form of plant) consumed passes from the body as waste products (feces and urine)
2) Part is used as heat for metabolism (respiration)
3) The remainder is available for maintenance
-capturing or harvest food, perform muscular work
-usually lost to the environment as heat
Energy left from maintenance and respiration goes into production of young and growth of new tissue
This net energy of production is called secondary production

14. LIMITATION IN PRIMARY PRODUCTION
Aquatic Ecosystems: light and nutrients
Terrestrial Ecosystems : temperature and moisture

15. PRIMARY PRODUCTION IN AQUATIC ECOSYSTEMS
The nutrient most often limiting marine production is either nitrogenor phosphorus.
❑In the open ocean, nitrogen and phosphorous levels are very low in the photic zone but are higher in deeper
water where light does not penetrate.
Some areas of the ocean have low phytoplankton density despite their relatively high nitrogen concentrations.
❑For example, the Sargasso Sea has a very low density of phytoplankton.
❑Nutrient-enrichment experiments showed that iron availability limits primary production in this area.
❑When iron is limiting, adding iron stimulates the growth of cyanobacteria that fix nitrogen.
❑The iron factor in marine ecosystems is related to the nitrogen factor.
❑Phytoplankton proliferate, once released from nitrogen limitation.
❑Iron --> cyanobacteria --> nitrogen fixation--> phytoplankton production

16. PRIMARY PRODUCTION IN TERRESTRIAL
ECOSYSTEMS
❑Tropical rain forests, with their warm, wet conditions, are the most productive of all terrestrial
ecosystems.
❑By contrast, low-productivity ecosystems are generally dry (deserts) or dry and cold (arctic
tundra).
❑Between these extremes lie temperate forest and grassland ecosystems with moderate
climates and intermediate productivity.
❑These contrasts in climate can be represented by a measure called actual
evapotranspiration, which is the amount of water annually transpired by plants and
evaporated from a landscape.

17. EVAPOTRANSPIRATION

18. ECOLOGICAL PYRAMIDS
Pyramid of Productivity
Pyramid of Biomass
Pyramid of Numbers

19. PYRAMID OF PRODUCTIVITY
This loss of energy with each transfer in a
food chain
Can be represented by a pyramid of net
production

20. PYRAMID OF BIOMASS
Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels.
In some aquatic ecosystems, small standing crop of primary producers (phytoplankton)
supports a larger standing crop of primary consumers (zooplankton).

21. PYRAMID OF NUMBERS
Represents the number of individual organisms in each trophic level

22. THE GREEN WORLD HYPOTHESIS
Proposed by Hairston, Smith and Slobodkinin 1960.
The world is green
because herbivores are held in check by their predators, parasites, and diseases such
that they cannot consume all the plant biomass.

23. THE GREEN WORLD HYPOTHESIS
The green world hypothesis proposes several factors that keep herbivores in check
1.Plants have defensesagainst herbivores -Plants contain much woody lignin as well as many
secondary compounds that inhibit herbivores
2.Nutrients usually limit herbivores-Nutrient such as nitrogen are critical for animals and are
often in short supply in plant materials.
3.Abioticfactors (temperature, moisture, light) limit herbivores. Seasonal changes in temperature,
precipitation, and other climatic factors depress herbivore numbers.
4.Intraspecific competitioncan limit herbivore numbers. Self-regulation through territoriality,
cannibalism, or other forms of interference competition can limit the numbers of some
herbivores
5.Interspecific interactionscheck herbivore densities. Enemies are effective in some communities
in which predators, parasites and disease limit herbivores and prevent them from consuming all
green plants .

24. BIOGEOCHEMICAL
CYCLES
WATER CYCLE
NITROGEN
CYCLE
PHOSPHORUS
CYCLE
CARBON
CYCLE

28. THE NITROGEN CYCLE
Four processes participate in nitrogen cycle:
Nitrogen fixation
Decay
Nitrification
Denitrification
Nitrogen enters atmosphere through 2 ways:
1. Atmdeposition (5-10%)
2. Nitrogen fixation (90-95%)

29. THE NITROGEN CYCLE
5-10%through atmosphere deposition
NH4+(ammonium) and NO3-(nitrate), the 2
forms available to plants
added to soil by dissolving in rain or settling
as dust or particles
Some plants, epiphytic bromeliads have
aerial roots that can take up NH4+ and
NO3-directly from moist atmosphere
ATMOSPHERE DEPOSITION

30. THE NITROGEN CYCLE
The ability to fix nitrogen is found only in certain
bacteria and archaea.
Some live in a symbiotic relationship with plants
of the legume family (e.g., soybeans, alfalfa).
Some establish symbiotic relationships with plants
other than legumes (e.g., alders).
Some establish symbiotic relationships with
animals, e.g., termites and "shipworms" (wood-
eating bivalves).
Some nitrogen-fixing bacteria live free in the soil.
Although the first stable product of the process is
ammonia, this is quickly incorporated into protein
and other organic nitrogen compounds.
1. NITROGEN FIXATION

31. THE NITROGEN CYCLE
Breaking down of molecules of dead organisms
into ammonia.
The release of ammonium (NH4+) from decaying
organic material is called ammonification
2. DECAY

32. THE NITROGEN CYCLE
2 steps:
Bacteria of the genus Nitrosomonas, oxidize
ammonia (NH3) to nitrites (NO2−)
Bacteria of the genus Nitrobacter , oxidize the
nitrites to nitrates (NO3−)
These two groups of autotrophic bacteria are
called nitrifying bacteria.
Soil and ocean = contain archaeal microbes, that
convert ammonia to nitrites. Abundant than
nitrifying bacteria .
Many legumes, in addition to fixing atmospheric
nitrogen, also perform nitrification
3. NITRIFICATION

33. THE NITROGEN CYCLE
Denitrification reduces nitrates to nitrogen gas,
thus replenished the atmosphere.
Bacteria are the agents, live deep in soil and in
aquatic sediments where conditions are
anaerobic.
They use nitrates as an alternative to oxygen in
anaerobic respiration.
Thus they close the nitrogen cycle.
4. DENITRIFICATION

35. THE PHOSPHORUS CYCLE
Do not involve atmosphere.
1.Plants absorb phosphorous in the form of PO43-(phosphate) from the soil
2.Transferred to consumers (snail) in organic form
3.Added back to soil by excretion of phosphate by animals (snail) and by the action of
bacteria and fungi decomposers
4.Mineralization into the soil
5.Leaching process of the soil will deposit the phosphate into the ocean
6.Sedimentation-is the process of letting suspended material settle by gravity.
7.Incorporated in rocks via geological uplift
8.Weathering and erosion of rocks-breakdown the rock and add phosphate to soil

36. SO, HERE IS THE END OF LESSON
THANK YOU FOR YOUR ATTENTION AND HARD
WORK
HOPE YOU HAVE GAIN A LOT FROM THE
CLASS.. I KNOW I HAVE ☺
I WISH YOU GOOD LUCK FOR YOUR FINAL
EXAM AND YOUR FUTURE UNDERTAKINGS.
THANK YOU STUDENTS!
NISA KAMIL