This document discusses food webs and energy flow through ecosystems. It explains that producers like plants and algae use photosynthesis to capture energy from the sun and make sugar, while some bacteria use chemosynthesis. Consumers break down sugars through respiration. Food chains show how primary producers are eaten by primary consumers, which are eaten by secondary consumers, and so on. Decomposers break down organic matter and release nutrients for producers. Food webs and net primary productivity depend on photosynthesis by producers. Keystone species are important to food web structure. Energy and matter cycle through ecosystems via biogeochemical cycles like carbon and nitrogen cycles. Relationships between species include mutualism, commensalism, parasitism,

1. Food Web dynamics and
Productivity
movement in ecosystems
Big Idea 4: Biological Systems
Interact

2. Essential Knowledge
•4.A.6: Interactions among living
systems and with their environment
result in the movement of matter and
energy.

3. Energy Flows in Ecosystem
Producers
Consumers
Decomposers

4. Producers: PhototroPhs
• Use sun to produce sugar (PS)
• Plants, Algae (Phytoplankton),
Bacteria
• PS is 1 % efficient!

5. • Use H2S to produce sugars
(chemosynthesis)
• Bacteria
Producers: chemotroPhs

6. consumers: heterotroPhs
• Break down stored sugars (aerobic
respiration)
• C6H1206 + 6H2O + 6O2 
6CO +12H O+ Energy (36 ATP)

7. simPliFied Food chain
• Primary producers get eaten by….

8. • Primary consumers get eaten by…
simPliFied Food chain

9. simPliFied Food chain
• Secondary consumers get eaten by…

10. Simplified food Chain
• Tertiary consumers get eaten by…

14. Importance of Decomposers
• Make vital elements available to primary
producers.
 Convert organic material into inorganic
materials (producers can use in soil/
H2O)

15. Food Chains and Webs
• Are dependent upon primary
productivity!!!

16. Gross Primary
Productivity (GPP)
•Rate at which energy is captured
during PS and stored.
HIGH
LOW

17. Net Primary
Productivity
(NPP)
• Energy that
remains in
producers after
respiration;
biomass
available to
consumers
• NPP =
GPP - Resp.
Energy that
is available
to
consumers!

19. Keystone Species!
• Connected to many species in the food
web.
• Removal causes trophic cascade.
• Ex: Sea Otter

20. Math Calculations!
15 minutes

21. EnErgy Flows, But MattEr is
rEcyclEd! BiogEochEMical
cyclEs: c, n, and watEr

24. Nitrogen Cycle Video Clip
• Study Jams

25. Interactions Among
Organisms
Symbiosis:
relationship b/t 2
species
•Mutualism (+,+)
•Commensalism
(+,0)
•Parasitism (+,-)

26. Mutualism
• Both Species Benefit
• Rhinos and

29. Mycorrhizae• Symbiotic fungus
found on plant
roots
•Aids in water
retention, mineral
uptake (nitrates)
W/out M With M

30. Commensalism
• One member is helped, the other
neither benefits or is harmed
• Cows and Cattle Egrets

31. Parasitism
• + and -
relationship
•parasite benefits,
host loses
•parasite usually
smaller than host
Leech Bite, Thailand
Lamprey

32. Endoparasites
• Parasites that live within the body of the
host!
• Ex. Tapeworm…

33. Ectoparasites
• Parasites that feed on the external
surface of the host.
• Ex: ticks

34. Competition
• Orgs attempting to use the same
scarce resources in same
ecosystem.

35. Intraspecific Competition
• Between SAME species

36. Interspecific Competition
• Competition between
DIFFERENT species