170 likes | 545 Vues
Species – a group of similar organisms whose members interbreed and produce viable offspring. Population – members of the same species that live together in the same area at the same time.
E N D
Species – a group of similar organisms whose members interbreed and produce viable offspring. Population – members of the same species that live together in the same area at the same time. Community – all the populations of different species that live and interact together within an area at the same time. Ecosystem – a community together with its physical (abiotic) environment. Marine Ecology
Population growth More individuals Birth rates > death rates Decrease in resources Food, nutrients, space Until the available resources can no longer support more growth Lag phase Period of relatively slow growth Post-lag phase… Linear, Exponential, or logistic growth How Populations Work in a Community • Renewable resources:replenished by natural processes at a rate comparable or faster than its rate of consumption. • solar radiation, oxygen, tides, food, water, and winds • Non renewable: • used at a rate greater than the environment's capacity to replenish them
Linear growth Constant numerical increase; constant slope Doubling occurs relatively slowly Exponential growth Growing numerical increase; “J” curve Doubling occurs rapidly Occurs with no limits to growth e.g fig. 10.2b (dinoflagellates…much like these bacteria)
Environmental resistance Limiting factors Supply restricts the growth of a population (e.g. food) Logistic growth Converts a “J” curve to an “S” curve (fig. 10.4) Sets carrying capacity Population size sustained by available resources …as resources decrease, competition increases Exponential growth until?
competition, predation, symbiosis Competition organisms compete for same resources Intraspecific (within same species) Interspecific (between species) Superior competitor wins Outcompeting to the point of eliminating the other = competitive exclusion Organisms interact within a community
Resource partitioning Specializing in part of the resources slightly different food different spaces different times Dividing the resources Lends to smaller populations of a single species Giving up some of the resources is limiting Sharing to avoid exclusion
Mutualism Both organisms benefit “Cleaner” shrimp & fish (facultative) Zooxanthellae & Cnidaria (obligate) Commensalism One organism benefits w/o affecting the other E.g. whale barnacles (shelter & food) Parasitism One organism benefits at the expense of the other E.g. intestinal worms (Nematodes in fin whale gut) Ectoparasitic isopods Symbiosis (living together)
Lifestyles Benthic (bottoms) Pelagic (open-water) Plankton: drifting in the currents Phytoplankton autotrophic Zooplankton Heterotrophic Nekton: free swimming Environment/structure Transitional: land & sea Depth Topography Fig. 10.12 Marine communities
How energy passes through the ecosystem one way flow (Fig. 10.13) Producers autotrophs (self nourishment) that use simple inorganic molecules to make complex organic molecules (photosynthesize) Consumers heterotrophs (different nourishment) that eat producers to gain energy, cannot gain energy just from simple inorganics Decomposers heterotrophs that break down dead material to make energy At each level some heat is given off or lost energy that is unavailable to the next level Flow of energy w/in ecosystem
Most food webs are complex… this Antarctic example is considered simple:
Steps of energy transfer Each level relies on the level(s) below Trophic levels
10% E (ave) passes to next level Only a small amount goes toward actual growth Sustains fewer organisms 10 times more biomass is required to sustain the level above Fig 10.16 Energy efficiency
Amount of carbon converted (fixed) from CO2 to usable organics Gross primary production Net primary production Leftover after respiration gC/m2/day gC/m2/year Can also measure O2 production via photosynthesis Primary productivity
Productivity depends on: Light Location Depth Abundance of organics Etc…
CO2 is highly soluble 50 times > atmosphere Converted by photosynthesis Broken down by respiration Consumers, decomposers, & producers Carbon cycle
Homework (due 4/30/08) • Review pgs. 231-240 • Describe the human impact of burning fossil fuels & increasing the amount of CO2 in the atmosphere • What does this do to global temperatures? • How does this impact our oceans? • How does this impact the marine trophic levels?