Bio 10 Lecture Notes 9: Ecology SRJC

Transcription

1 Biomes A broad region characterized by vegetation types shaped by: Climate Average weather condition in a region Climate is affected by: amount of incoming solar radiation prevailing winds Topography- the elevation of land masses Rain Shadow Air rises on the windward side, loses moisture before passing over the mountain As you travel higher in elevation, conditions resemble those at higher latitudes (i.e. going up a mountain can seem like traveling toward the poles) Composition of regional soils. Terrestrial Biomes Deserts- Annual rainfall < 10 centimeters; high level of evaporation Form between 30 degrees north and south and in rain shadows Dry Shrublands and Woodlands Semiarid regions with cooler, wet winters and hot, dry summers Occur in western or southern coastal regions between latitudes 30 and 40 Plants adapted to dry conditions and fire (some rely on fire!) Dry Grasslands Shortgrass prarie Tallgrass prarie Desertification California Chaparral Conversion of large regions of natural grasslands to desert-like conditions Forest Biomes Tall trees form a continuous canopy Evergreen broadleaves in tropical latitudes Deciduous broadleaves in most temperate latitudes Evergreen conifers at high temperate elevations and at high latitudes Tropical Rainforests- lots of moisture, greatest diversity if life Tall Trees- competition for light Vines grow on tree trunks Large, dark green leaves adapted to living in shade of taller plants Epiphytes- plants growing on tree trunks, some can be parasitic Tropical forest canopies are layered, space is limiting factor Temperate Deciduous Forests- broad-leaf trees, drop leaves in winter Coniferous Forests- needle-shaped leaves conserve heat, keep them all year round A. Carranza Page 1 7/25/2015

2 Tundra- plants grow low to conserve heat Arctic Permafrost lies beneath surface Alpine Occurs at high latitudes The Water Provinces: Freshwater Biomes Lakes- Bodies of standing freshwater Eutrophic: shallow, nutrient-rich; has high primary productivity (green water) Oligotrophic: deep, nutrient-poor; has low primary productivity (clear water) Thermal Layering In temperate-zone lakes, water can form distinct layers during summer Seasonal Overturn In spring and fall, temperatures in the lake become more uniform Oxygen-rich surface waters mix with deeper oxygen-poor layers Nutrients that accumulated at bottom are brought to the surface Eutrophication Enrichment of a body of water with nutrients Can occur naturally over long time span Can be triggered by pollutants Rivers and Streams Water moves continuously in one direction. Water may become polluted as it travels to the sea. Estuary Partially enclosed area where saltwater and freshwater mix Dominated by salt-tolerant plants Chesapeake Bay, San Francisco Bay, salt marshes of New England Salt Marsh Mangrove Wetlands Tropical saltwater ecosystem Form in nutrient-rich tidal flats Dominant plants are salt-tolerant mangroves Florida, Southeast Asia Estuarine Food Webs Primary producers are phytoplankton and salt-tolerant plants Much primary production enters detrital food webs Detritus (decomposing organic material) feeds bacteria, nematodes, snails, crabs, fish A. Carranza Page 2 7/25/2015

3 Ocean Provinces (biomes) Intertidal-(Littoral zone)- within the mean high and low tides Intertidal Zones Upper littoral submerged during highest tides of cycle (low diversity) Midlittoral zone regularly submerged and exposed (moderate diversity) Lower littoral exposed only during lowest tides Benthic- attached to or living at the bottom Pelagic- swimming or drifting in the water column (open water) Sandy Coastlines Loose sediments, continually rearranged Few grazing food webs Detrital food webs from organic debris Interstitial Meiofauna Communities of microscopic animals living between sand grains Coral Reef Biomes Reef-building corals have photosynthetic, dinoflagellate symbionts Oceanic Biome (or Province) Photic Zone (Euphotic zone) depth to which light can reach photosynthetic organisms Marine Snow- form basis of food chain where light cannot reach Hydrothermal Vents Chemoautotrophic bacteria use mineral-rich hot water as energy source Upwelling Brings cold, nutrient-rich bottom waters to the surface Upwelling of cool water along western coasts Wind driven phenomenon A. Carranza Page 3 7/25/2015

4 Ecosystems A group of interacting populations and their physical environment. All interacting by a flow of energy and with their physical and chemical environments. Modes of Nutrition Photoautotrophs (photo= light, auto=self, trophos=nutrition) Capture sunlight or chemical energy Primary producers Heterotrophs (hetero= other, trophos= nutrition) Extract energy from other organisms or organic wastes Consumers, decomposers, detritivores (eat detritus) Role of Organisms Primary Producers Photoautotrophs Consumers Herbivore- primary consumers Carnivores-secondary consumers, can also be tertiary or further level, depending on who they eat. Omnivores- can be both primary and secondary depending on what they re eating Parasites- secondary or primary consumer,depending on who they parasitize Decomposers- can enter food chain at any trophic level depending on what they re eating Trophic Levels (Feeding relationships) All organisms at a trophic level are the same number of steps away from the energy input into the system Autotrophs are producers closest to energy input first trophic level Energy Flow One-way flow of energy: sun primary producers consumers Primary Productivity Gross primary productivity- total amount of photosynthate created Net primary productivity- amount available to primary consumers (stored by plants) Pyramids of biomass and energy- biomass and energy decrease as you go higher up the food chain Most energy is lost as heat or used to perform work (metabolic pathways) The Rule of Ten or 10% Law - only 10 percent of energy and biomass are present at each successive trophic level Biological magnification- contaminants accumulate in organisms at top of food chain Water Cycle Generally, water evaporates from ocean, falls as precipitation then flows back to ocean Plants Influence the Water Cycle A. Carranza Page 4 7/25/2015

5 Plants Protect Soil Deforestation leads to soil and nutrient erosion Carbon Cycle Reservoirs Atmosphere Oceans Trees and shells (clams etc) are carbon biomass holding stations Decomposers recycle and liberate carbon from the holding stations Decomposition Rates Higher rates in forests due to favorable conditions (moist and warm) Not much carbon accumulates Peat Bog Slow decomposition due anaerobic conditions, more C accumulates Source to Atmosphere Plant and animal respiration Burning of plants Fossil fuels Volcanic acitivity Carbon Cycle Carbon is assimilated by plants then passed on to consumers Consumers and decomposers release C back to atmosphere as CO2 Nitrogen Cycle Reservoir atmosphere Source to Plants Nitrogen-fixing bacteria Decomposition Plant Limiting Factor for Growth Nitrogen Cycle Nitrogen fixing bacteria reduce atmospheric N2 to ammonia (NH3) Primary producers can assimilate NH3 and NO3 to make amino acids Consumers eat producers and acquire N in amino acid form Decomposer bacteria recycle N from organic material Ammonifying bacteria turn NO3 to NH3 Nitrifying bacteria turn NH3 to NO3 Another group of bacteria (denitrifying) turn NO3 to N2 Atmospheric N2 Nitrate (NO3) Ammonia (NH3) A. Carranza Page 5 7/25/2015

6 Community Interactions Community A group of interacting populations Populations are affected by: Available living space (habitat) Resource Availability (niche) Species interactions Habitat an organism s mailing address; the type of place where the individuals normally live Niche an organism s profession (role) in the community Species Interactions Symbiosis Living together for at least some part of the life cycle Most interactions are neutral; they have no effect on either species Commensalism helps one species and has no effect on the other Mutualism helps both species Some are obligatory; partners depend upon each other (coevolution) Yucca plants and yucca moth Mycorrhizal fungi and plants Anemone fish and anemone Parasitism Parasites draw nutrients from hosts live on or in host body Vectors Convey a parasite from host to host Parasitoids Develop inside another species Consume and kill host Micro Parasites microscopic; bacteria, protozoa, etc Competition Interspecific: among different species Exploitative competition- get as much of resource before competitor Interference competition- behaviorally keeping competitor from a resource Intraspecific: between members of the same species Intraspecific competition is most intense Territoriality Allelopathy (sibling harming)- impeding, hurting or killing same species rivals Some species have eliminated ways of avoiding competition: Resource partitioning- developing a very specified niche and focus on resources not common to competitor May use resources in a different way or time Minimizes competition and allows coexistence A. Carranza Page 6 7/25/2015

7 Lions hunt big game, cheetahs go after smaller, faster prey Competitive Exclusion Principle When two species compete for identical resources, one will be more successful and will eventually eliminate the other Predators animals that feed on other living organisms free-living do not reside on their prey Carnivores and omnivores Predator-Prey Relationships Species are limited by the number of available prey In some cases predators limit a prey species Coevolution Two or more species exert selection pressure on each other Prey defenses evolve Prey Defenses Camouflage Warning coloration Mimicry Predator Responses Predators counter prey defenses with new adaptations stealth camouflage avoidance of chemical repellents Community Dynamics Factors affecting changes in community structure Intermediate Disturbance Hypothesis Ecological Community stability is an uneasy balance Community Instability Disturbances can cause a community to change in ways that persist even if the change is reversed. In some cases these are considered alternate stable states Keystone Species A species that has a disproportionately large effect on community structure Removal of a keystone species can cause drastic changes in a community can increase or decrease diversity Species Introductions Exotic species A species moves out of its home range and takes up residence in a new place No natural enemies or controls Can outcompete native species Ecological Succession Over time, one array of species is replaced by another Types of Succession Primary succession: new environments Begins with foundation species A. Carranza Page 7 7/25/2015

8 Ends with climax community Secondary succession: communities destroyed or displaced May not have foundation species Also ends with climax community Climax Community Stable array of species that does not change over time The final community in ecological succession In a particular habitat, succession produces the same climax community Population Ecology Population All members of a species living in a defined area at the same time Ecological principles govern growth and sustainability of all populations Demographics Population size- Total number of individuals Population Age Structure Divides population into age categories Reproductive base pre-reproductive and reproductive age categories Population Density the number of individuals per unit area. Population Distribution Patterns of Population Distribution Random Dispersion- the position of each individual is independent of the others. Uniform Dispersion-when individuals are evenly spaced. Clumped Dispersion- when individuals aggregate in patches. Clumped is most common type * * * * * * * * * * * * * * * * Random Uniform Clumped Population Size and Exponential Growth + Births: add to population - Deaths: subtract from population + Immigration: add to population -Emigration: subtract from population r = Net reproduction per individual per unit time (r = b - d, assuming no migration) Variable combines per capita birth and death rates (assuming both constant) Can be used to calculate rate of growth of a population A. Carranza Page 8 7/25/2015

9 Birth Rate b = number of births / number of individuals Death Rate d = number of deaths / number of individuals Zero Population Growth Interval in which number of births is balanced by number of deaths Assume no change as a result of migration Population size remains stable Exponential Growth Equation G = rn G is population growth per unit time r is net reproduction per individual per unit time N is population size Exponential Growth Population size grows by increasing increments during successive intervals The larger the population, the more individuals reproduce Effect of Deaths Population grows exponentially as long as per capita death rates are lower than per capita birth rates Biotic Potential Maximum rate of increase per individual under ideal conditions Varies between species In nature, biotic potential is rarely reached Limiting Factors Any essential resource that is in short supply All limiting factors acting on a population dictate sustainable population size Carrying Capacity (K) Maximum number of individuals that can be sustained in a particular habitat Logistic growth occurs when population size is limited by carrying capacity Logistic Growth As size of the population increases, rate of reproduction decreases When the population reaches carrying capacity, population growth ceases Logistic Growth Equation G = rmax N (K-N/K) G = population growth per unit time A. Carranza Page 9 7/25/2015

10 rmax = maximum population growth rate per unit time N = number of individuals K = carrying capacity Overshooting Capacity Population may temporarily increase above carrying capacity Overshoot is usually followed by a crash; dramatic increase in deaths J (exponential) vs S (logistic) curves Density-Dependent Controls Logistic growth equation deals with density-dependent controls Limiting factors become more intense as population size increases Disease, competition, parasites, toxic effects of waste products Density-Independent Controls Factors unaffected by population density Natural disasters or climate changes affect large and small populations alike Survivorship Curves a plot of age-specific survival 3 types of survivorship curves Type I high survivorship until fairly late in life typical of species w/ low reproductive rates reproduce fewer young, spend time and energy nurturing and protecting young, larger, stronger, more developed offspring (more likely to survive in competitive env.) humans, elephants K-selected species Predictable Environments found late in succession, stable well-defined communities # AGE Type II fairly constant death rate at all ages lizards, small mammals, song birds Type III highest death rate early in life reproduce at a young age, produce large # of offspring, devote little care to offspring, may die after reproducing starfish, oysters r-selected species Unpredictable Environments A. Carranza Page 10 7/25/2015

11 Life History Patterns Patterns of timing of reproduction and survivorship Vary among species Life History Traits Age of first reproduction Number of offspring per reproduction event Body size at maturity Brood interval Human Population Growth Population exceeds 6 billion Rates of increase vary among countries Average annual increase is 1.3% Population continues to increase exponentially Increase in growth rate Expansion of habitat and new climatic zones Increased capacity in existing habitats Population has sidestepped limiting factors Technology better shelter, sewage disposal Medicine immunization, disease control, prenatal care, better hygiene Human population has grown almost exponentially for three centuries. The human population increased relatively slowly until about 1650 when the Plague took an untold number of lives. Now doubling time ~50yrs (at 1.2%). Inevitability, human populations will stop growing, but how or when we are not sure. A. Carranza Page 11 7/25/2015