Understanding Ecology: Interactions, Biomes, and Ecosystems

1. ECOLOGY Introduction

2. I. WHAT IS ECOLOGY? • study of interactions between organisms & the environment • leads to evaluating of environmental issues

3. A. Important Abiotic Factors 1. environmental temp. • water • sunlight – drives nearly all • wind – effects temp. • rocks & soil (structure, pH & minerals) • periodic disturbances (fire, hurricanes, volcanoes)

4. III. The cost & benefits of homeostasis • Regulators: maintain homeostasis through behavioral & physiological mechanisms • Conformers: allow internal conditions to vary w/ external • Principle of allocation: each organism has a limited amount of energy that can be allocated for obtaining nutrients, repro. escaping; so too much for homeo….

5. IV. BIOMES – often name for predominant vegetation

6. Tropical Forest • near equator • temp. varies little • rainforest = greatest diversity

7. Savanna • grassland w/ scattered trees • S. America & Africa (central & south)

8. Desert • low & unpredictable precipitation (not temp.) • central Asia & N. Africa

9. Chaparral • dense, spiny shrubs w/ tough evergreen leaves (along coasts) • periodic fires

10. Temperate Grasslands • similar to savannas but with cold winters (plains & prairies of U.S.) • soil deep & rich

11. Temperate Deciduous Forest • midlatitude regions with sufficient moisture to support large, broad-leaved dec. trees

12. Taiga • coniferous forest • soil thin & acidic

13. Tundra • permafrost • northern-most limits of plant growth (low shrubby, mat-like vegetation) • not a lot of animals

14. V. Aquatic Biomes – occupy the largest part of the biosphere • Freshwater – (less than 1% salt) closely linked to terrestrial biomes they are near • Marine – (more than 3% salt) 75% of Earth; algae make most oxygen

15. Ponds & Lakes • standing bodies of water • vertical stratification in light (aphotic vs. photic) & temperature (thermocline) • oligotrophic = deep, nutrient poor (clear) • eutrophic = shallow, nutrient rich (murky)

16. Streams & Rivers • bodies of water that move continuously in 1 direction • change in structure & life from headwaters to mouth

17. Wetlands • covered by water that support aquatic vegetation • hydrophytes live here

18. Estuaries • area where fresh water stream or river merges with ocean • very productive due to nutrients from rivers • salinity varies

19. The Intertidal Zone • where land & sea meet; alternately submerged & exposed by tides • Rocky – vertically stratified (attached to harsh) • Sandy – no clear stratification (pred. & scavengers)

20. Coral Reefs • warm, tropical water where sunlight penetrates to ocean floor (diverse & productive)

21. Oceanic Pelagic Biome • open waters far from shore • nutrient content low • plankton & nekton prevalent

22. Benthos • ocean bottom • nutrients from detritus • diverse • low light & temp.

23. POPULATION ECOLOGY

24. I. Important Characteristics • Density = number of individuals per unit area or volume • Dispersion = clumped, uniform or random

25. III. Mathematical model for exponential growth describes an idealized population in unlimited environment • Change in population size over time = births – deaths • ZPG = death & birth rates are equal (births & deaths still occur) • Carrying capacity = maximum stable population size that the environment can support over long time period

26. IV. Factors affecting population growth • Density-dependent * nutrients * territory * accumulation of waste • Density-independent * weather, climate * natural disasters

27. COMMUNITY ECOLOGY

28. I. Predation & parasitism (+ - ) interactions • Predation 1. Plant defenses against: thorns, hooks, spines, bad taste, hormones causing abnormal development 2. Animal defenses: hide, escape, coloration 3. Mimicry: to scare or lure prey

29. Interspecific competitions are(- -) • Inference competition – fighting • Exploitative competition – consumption or use • Niche: how it “fits into” an ecosystem (the organism’s role)

30. V. Factors that structure communities • Competition • Predation • Environmental patchiness: more heterogeneous the habitat = more diverse community

31. VI. Succession is the sequence of changes in a community after a disturbance • Ecological succession: transition in species composition over ecological time • Primary succession: begins in areas essentially barren of life due to lack of formed soil or on rubble • Secondary succession: if an existing community has been cleared by some disturbance that leaves soil intact

32. Climax community: relatively stable state after transitional stages • Disturbances can have positive impact on community: species diversity

33. ECOSYSTEMS * Involves energy flow & chemical cycling

34. I. Trophic structure determine an ecosystem’s routes of energy flow & chemical cycling • Food chain – pathway along which food is transferred from trophic level to trophic level • Food web – relationships actually woven & elaborate

36. Trophic levels: 1. primary producers 2. primary consumers 3. secondary consumers 4. tertiary consumers 5. decomposers

37. II. An ecosystem’s energy budget depends on primary productivity • Primary productivity: amount of light energy converted to chemical energy by autotrophs of an ecosystem gross: total converted net: total – energy used for respiration

38. Factors determining productivity: temperature, precipitation, light intensity • As energy flows through an ecosystem, much is lost at each level (85-95% of energy available never transfers to next level) • Only 3-5 trophic levels can be supported • Predators highly susceptible to extinction if ecosystem disturbed

39. Water Cycle • Sun causes evaporation from ocean --- water rises, cools --- falls as precipitation • Primarily physical

40. Carbon Cycle • Carbon dioxide into leaf – into biomass – out with respiration • Some carbon diverted in wood, coal, petroleum

41. Nitrogen Cycle • Atmosphere 80% N2 • Nitrogen only available NH4 (ammonium) & NO3 (nitrate) • Enters ecosystems by atmospheric deposition (5-10% dissolved by rain) or nitrogen fixation

42. Phosphorus Cycle • Weathering rocks adds P to soil – producers absorb & incorporate – transferred to consumers – back to soil by excretion & decomposition