Chapter 56 Ecosystems

1. Chapter 56 Ecosystems Biology 101 Tri-County Technical College Pendleton, SC

2. Community versus an Ecosystem • Community consists of populations of all the different organisms in a defined area • As applied, term descriptive of biotic entities (living organisms) • Ecosystem describes all organisms living in particular area together with the physical environment (abiotic) • Abiotic describes nonliving chemical and physical factors in the environment

3. Components of an Ecosystem • Activities of individual organisms within ecosystem • These activities influenced by processes in physical environment • Individuals capture energy and materials; transform and/or retain those items; then transfer them to other organisms • Climates on Earth important component of an ecosystem

4. Components, cont. • Patterns of energy flow • Cycling of materials • Water, carbon, nitrogen, sulfur, phosphorus • Biogeochemical cycle is pattern of movement of chemical element through organisms and compartments of the physical environment

5. Roles and Key Terms • Organisms depend on inputs of energy (sunlight or high energy molecules), water, and minerals for metabolism and growth • All energy utilized comes (or came) from sun • Are a few very limited ecosystem exclusions • Energy flow in most ecosystems originates with photosynthesis • PRODUCER is an organism that can make its own food

6. Roles and Terms, cont. • Most are photosynthetic but some are chemoautotrophic • Source of energy is solar (grow bulbs) • Green plants, photosynthetic bacteria (cyanobacteria and others), and protists (algae and others) • Provide energy-rich organic molecules upon which nearly ALL other organisms feed

7. Roles and Terms, III • Herbivore = consumes primary producers • organism that eats plants (plant products) • Carnivore = animal that feeds on other animals • Primary = eat herbivores • Secondary = feed on primary carnivores • Omnivore obtains food from more than one tropic level • Hybrid of herbivore and carnivore

8. Roles and Terms, IV • Scavenger = organism that feeds habitually on refuse or carrion • Parasite (ecological sense) = organism that absorbs nutrients from body fluids of living hosts • Decomposer/detritovore = feed on dead bodies and waste products of other organisms • Where would we be without them?

9. Chains and Webs • Only about 10% of energy captured at one tropic level available to next higher level • Most is lost to system as heat and by respiration • Energy content of organism’s NET PRODUCTION (growth plus reproduction) is available to next level • Efficiency of energy transfer through food webs depends on fraction of net production that is consumed by others at next level and HOW those organism divide ingested energy between production and maintenance

10. Chains and Webs, cont. • Grasslands, forests, and aquatic communities • Birds and mammals have very LOW production efficiencies because they spend so much energy maintaining constant high body temperature • Herbivore usually LESS efficient than carnivores

11. Primary Production Visual

12. Food Web Visual

13. Bioaccumulation • If compound (chemical) water soluble, it may be quickly metabolized and detoxified • Many water soluble compounds filtered out of blood by kidneys • Lead is an exception • Lipid soluble metabolized MORE slowly • May be stored in body for long time because they dissolve in lipids of membranes and adipose tissue • Mega dose of vitamins, anyone?

14. Bioaccumulation, cont. • Lipid soluble toxins (pesticides/others) can bioaccumulate in environement • Become more and more [ ]ed in predators that consume contaminated prey • [ ]ed 1000s to millions of times • Long-lived species (bears/eagles) particularly at risk • Bioaccumulation may be responsible for high rates of cancer/infertility • Classic examples are DDT and PCB • Humans at top of chain, enough said!!!!!!!

15. Cycles and More…much more! • Amounts of carbon, nitrogen, phosphorous, calcium, sodium, sulfur, hydrogen, oxygen, and other chemical elements on Earth DO NOT change • Quantities available to organisms strongly influenced by HOW they get them, HOW LONG they hold to them, and WHAT they do with them while they have them • Divide global ecosystems into four compartments: oceans, fresh water, atmosphere, and land

16. Cycles, cont. • Elements needed in large quantities cycle through organisms to physical environment and back again • C, H, O, N, P, S • Biogeochemical cycle: pattern of movement of chemical element through organisms and compartments of physical environment • Elements that exist as gases (C and N) cycle faster than nongaseous elements

17. Hydrological Cycle • Cycling of water through 4 compartments • Driven by evaporation of water (most from ocean’s surface) • Also from soils, freshwater lakes and rivers, and from leaves of plants (transpiration) • Returns as rain or snow • Then eventually returns to oceans via rivers, coastal runoff, and subterranean flows

18. Carbon Cycle • Nearly all carbon comes from CO2 in atmosphere or dissolved carbonate ions (HCO3-) in water • Marine organisms tie up some carbon in shells and skeletons • Much carbon in fossil fuels • 1850 (265ppm); 2002 (350ppm); 2050 (580ppm) • Altering the heat balance of Earth (global warming)

19. Nitrogen Cycle • Nitrogen gas (N2) CANNOT be used by most organisms in that form • Can be converted to usable form by only few species of bacteria and cyanobacteria • Nitrogen gas to ammonia in process called nitrogen fixation • Nitrogen often in short supply in most ecosystems

20. Nitrogen Cycle, cont. • Tends to be lost rapidly by leaching, vaporization of ammonia, and by denitrification (return of nitrogen to atmosphere as N2 by some organism (denitrification) • Nitrifiers do NOT take up nitrogen from atmosphere nor respire it back to atmosphere • Convert organic molecules containing nitrogen to inorganic molecules • Nitrates or ammonia that is taken up by plants

21. Nitrogen Cycle Visual

22. Phosphorus Cycle • Exists mostly as phosphate ion (PO3/4-) • Most phosphate deposits are of marine origin • On land, phosphorus becomes available by slow weathering and dissolution of rocks and minerals • Needed as component of energy rich molecules in cellular respiration, AA’s, and nucleic acids • Eutrophic (enriched) Lake Erie and others • Alga blooms, Escherichia coli, closed beaches

23. Human Impact • Humans have increasing impact on all ecosystems • Pick any ecosystem • Global warming, Acid rain, ozone layer depletion, agricultural practices, and deforestation • Where do we begin? or better yet… • Where will it end?