Population Growth Curves

Exponential vs. Logistic Growth

Predator-Prey Population Cycles

Figure 53.12

Figure 53.22

Figure 53.25

Figure 53.20

What do Ecologists Study?• Ecosystem: all interactions between living things

(community) and physical factors in a given area– Biotic (living) vs. abiotic (non-living) factors (ex., floods, droughts)

• Habitat: place where organism lives; can be general or specific (biomes are major climatic zones)

• Niche: organism’s way of life; multi-dimensional; in theory, only one species can occupy a niche (ecological species concept)

• Energy Flow: producers, autotrophs, phytoplankton; consumers, heterotrophs, zooplankton, herbivores, carnivores, omnivores, detritivores, decomposers – Food Chains: ~90% energy loss each trophic step– Food Webs: more realistic; note importance of krill in Southern

Ocean food web (shared resource, not necessarily limited)– Food Pyramids: less biomass (and abundance) at higher levels;

decomposers act on all trophic levels• Biogeochemical Cycles: hydrologic, carbon, nitrogen cycles

– Carbon cycle: related to global warming theory

Figure 52.19

Figure 54.11

Figure 55.10

Figure 55.9

Figure 55.14a

Figure 55.14b

Figure 55.14c

Figure 55.14d

What Relationships Exist Between Organisms in Ecosystems?

• Predation and Anti-predation– Diet Specialists/Generalists: specialists can have morphological, behavioral,

and physiological adaptations for capturing/assimilating prey; scarcity of prey can lead to extinction of diet specialists

– Anti-predation: cryptic and warning colorations, mobbing, displays • Competition: assumes a limited (not just shared) resource; removal

experiments used to test for effects on fitness– Intraspecific: between members of same species; most intense is between

males for access to females– Interspecific: between separate species; can lead to competitive exclusion– Scramble: rare in nature; all may get less than needed– Contest: mechanisms; ex. harems vs. sneakers (ex., wrasse, marine iguana)

• Symbiosis: evolved life-relationship between two or more species– Mutualism: both species benefit (ex. anemone and clownfish)– Parasitism: one benefits, other is harmed; endo- and ectoparasites– Commensalism: one benefits, other with no effect; least common,

examples often debated (exs. whale shark with pilotfish; reef shark with remora? – debatable, since remora may cause hydrodynamic drag)

• Facilitation: organism indirectly benefits others (ex., earthworms aerate soil, nightly excretion of ammonium by blacksmith benefits

algae)

Figures 54.2and 54.3

Why is Biodiversity Important?

• Biodiversity: variation among living organisms– Species diversity: number of species in an ecosystem; increases

with stability/uninterrupted evolution (ex., deep sea, tropical rain forests), and available niches; decreases with isolation

– Genetic diversity: variation within a species• If low, more vulnerable to catastrophic changes/extinction

• Importance of Biodiversity– Ecosystem stability: keystone species are those with influence

disproportionate to their abundance (ex. sea otter in Alaska) – Genetic reserves; esp. regarding agriculture; endemic species are

unique to particular habitat (ex. marine iguana in Galapagos Is.)

– Practical uses (ex. medicine, future foods)– Aesthetic and ethical value: biophilia, Gaia Hypothesis

• Largest Threats to Biodiversity1. Habitat loss and fragmentation: conservation incl. wildlife corridors2. Introduced species (especially on islands)3. Hunting/poaching; illegal trade international treaty (CITES)

Figure 54.15

Figure 56.17