COMMUNITIES AND ECOSYSTEMS

Transcription

1 COMMUNITIES AND ECOSYSTEMS 1 COMMUNITY ECOLOGY The study of how abiotic and biotic interact to affect the composition and distribution of communities. INTERACTIONS AMONG SPECIES 1. Competition for a niche ( / ) Lowers carrying capacity Spp. do not always coexist Removal experiments (Ex: warblers) 2. Mutualism (+ / +) Ex: Coral polyps and dinoflagellates Orange Crowned warbler (Vermivora celata) Virginia s warbler (Vermivora virginiae) Ecological niche the sum of an organisms use of biotic and abiotic resources in its environment. 2 1

2 INTERACTIONS AMONG SPECIES Predation and herbivory can lead to diverse adaptations 3. Predation (+/ ) Adaptations in prey for predator avoidance Spines, camouflage, bright colors 4. Herbivory (+/ ) Adaptations in plants for herbivore avoidance (tannins) Thorns, chemicals 5. Parasitism (+/ ) Internal / external Pathogens Not well studied in nature 3 COEVOLUTION A series of evolutionary adaptations in two species that occur in response to one another. Ex: Heliconus caterpillar and passion flower plant coevolution in response to herbivory Heliconius Eggs Decoy eggs 4 2

3 TROPHIC STRUCTURE A pattern of feeding relationships that consist of multiple levels 4 0 Hawk Killer whale Missing scavengers, detritivores and decomposers Snake Tuna Organisms are not always limited to one trophic level Food webs are a better representation of interactions Mouse Grasshopper 1 0 Producers Herring Zooplankton Plant A terrestrial food chain Phytoplankton An aquatic food chain 5 FOOD WEBS Arrows show paths of energy flow Food webs in nature are complex Trophic levels can vary Indirect effects (Ex: lion, zebra, grasses) 6 3

4 7 SPECIES DIVERSITY Includes species richness and relative abundance SPECIES RICHNESS The number of different species present RELATIVE ABUNDANCE A species proportion of total abundance Richness = 4 A Relative Abundance: A = 16/20 = 0.8 B = 2/20 = 0.1 C = 1/20 = 0.05 D = 1/20 = 0.05 B C D Diversity of this community =

5 SPECIES DIVERSITY Includes species richness and relative abundance Richness = 4 A Relative Abundance: A = 5/20 = 0.25 B = 5/20 = 0.25 C = 5/20 = 0.25 D = 5/20 = 0.25 B C D Diversity of this community = HIGH SPECIES DIVERSITY Can impact the stability of a community High plant diversity can increase diversity of other trophic levels Low diversity can result in small isolated populations gene flow, gene dispersal, slow growth rates (Tree C) A B Community 1 C Community 2 D Low diversity can increase negative effects of disease, parasites etc (Tree A) C A Applications for farmers B D 10 5

6 DIVERSITY Can vary among communities Rocky intertidal = high waves; competition for space Home to sponges, snails, clams, anemones, barnacles and algae Sea stars are the 2 0 How would sea star removal affect diversity? 11 KEYSTONE PREDATORS Have larger affects on communities than their abundance would indicate; Can maintain diversity In the absence of sea stars, mussels outcompete others for space! Number of species present With Pisaster (control) Without Pisaster (experimental) Year

7 SEA STAR WASTING DISEASE IN SO. CAL 13 DISTURBANCE An event that damages biological communities and alters resources Small disturbances can make new habitat (fallen tree) Severe disturbances can strip away producers, soil or substrate 14 7

8 ECOLOGICAL SUCCESSION The colonization and replacement of species after a severe disturbance Primary succession occurs when even soil is stripped away (Ex: lava, glaciers) 1 st colonizers: bacteria 1 st producers: lichens, mosses Decaying matter and rocks eventually create soil (1000s 100,000s of years) Vascular plants outcompete lichens and mosses Slow growing plants establish 15 ECOLOGICAL SUCCESSION The colonization and replacement of species after a severe disturbance Secondary succession occurs when the entire community is cleared away; Community structure and diversity depend on successional stage Annual Plants (type III survival) Perennial plants and grasses Shrubs Softwood Trees (5 20 yrs) Hardwood Trees (100s of yrs) Time 16 8

9 INVASIVE SPECIES Can affect diversity of communities Not always successful Can dominant communities; decrease diversity and alter ecosystems Expensive to remove Ex: Caluerpa taxifolia 600 km Key Frontier of rabbit spread Invasive species: plants, animals, or pathogens that are foreign to an ecosystem and can cause ecological or economic harm ECOSYSTEM ECOLOGY The study of all organisms and abiotic processes in a community Light Autotrophs Producer Energy Chemical elements Herbivore (1 0 consumer) Heterotrophs Detritus Carnivore (2 0 consumer) Cycling of energy and chemicals : carbon, nitrogen, and phosphorous Study of energy flow Inorganic compounds (chemical elements) Decomposer Biomass: the amount of living organic material in an ecosystem 18 9

10 ENERGY FLOW Energy is lost during each trophic level transfer 50% waste Plant material eaten by caterpillar 100 kilocalories (kcal) 35% cellular respiration 15% converted to new biomass Feces 50 kcal 15 kcal 35 kcal Cellular respiration Growth 19 ENERGY FLOW Less energy available as you move up the food chain Producers 10 kcal 10,000 kcal 100 kcal 1,000 kcal 1,000,000 kcal of sunlight Snake gets.001% of initial energy supplied by producers Top level often roam large geographic areas Producers have highest biomass of most ecosystems 20 10

11 ENERGY FLOW & HUMAN RESOURCES Principles apply to use of resources on agriculture and livestock 1 0 Less water needed Less land used Trophic level Secondary 2 0 More water needed More land needed Expensive! Meat-eaters Primary Vegetarians Cattle Producers Corn Corn 21 BIOGEOCHEMICAL CYCLING Chemical elements are finite and necessary for all forms of life Autotrophs Heterotrophs Light Producer Energy Chemical elements Herbivore (1 0 consumer) Detritus Carnivore (2 0 consumer) Chemical elements are stored as organic compounds in 1) living organisms 2) abiotic reservoirs Decomposer Inorganic compounds (chemical elements) 22 11

12 THE CARBON CYCLE Abiotic reservoirs: atmosphere, fossil fuels, limestone and the ocean 5 Burning CO 2 in atmosphere 3 Cellular respiration Photosynthesis 1 Higher-level Plants, algae, cyanobacteria Wood and fossil fuels Primary 2 Decomposition Decomposers (soil microbes) 4 Wastes; death Detritus Plant litter; death 23 THE PHOSPHOROUS CYCLE Abiotic reservoirs: rocks, Essential element for (ATP, DNA) 6 Uplifting of rock Weathering of rock Runoff Phosphates in rock 1 3 Plants Animals Most usable form is phosphate (PO 4 3 ) Rock Phosphates in solution 5 Precipitated (solid) phosphates Assimilation 2 Phosphates in soil (inorganic) Decomposition 4 Detritus Decomposers in soil Often limiting (algae) Mycorrizal fungi! 24 12

13 THE NITROGEN CYCLE Essential element for (amino acids, proteins) Can be a limiting resource for plants Greenhouse gas N 2 O Naturally occurring Easiest uptake Urea or N from decomposition Easy uptake 25 8 Nitrogen (N 2 ) in atmosphere Plant Animal 6 Denitrifiers 5 Nitrates in soil (NO 3 ) Assimilation by plants 3 Organic compounds Death; wastes Detritus Organic compounds Nitrogen fixation Nitrogen-fixing bacteria in root nodules Decomposers Free-living 4 Nitrifying 7 Decomposition nitrogen-fixing bacteria bacteria Nitrogen fixation Ammonium (NH + 4 ) in soil

14 EUTROPHICATION The increase of primary production over time in standing aquatic ecosystems (Ex: urban or agricultural runoff in lakes, ponds) Can lower species diversity Blooms from overload of nutrients Cyanobacteria block light Diatoms reduce oxygen at night Microbes deplete oxygen after bloom Cascading effects in community 27 SUSTAINABILITY The goal of developing, managing and conserving Earth s resources in a way that meets the needs of people without compromising the resources of future generations. Agriculture: depleted soil nutrients, pesticides, fertilizers Deforestation: depletes soil nutrients; increases erosion Desertification in semi arid regions SBCC Sustainability Program

15 REQUIRED VIDEOS The core concepts of this material are fair game for exams! Rethinking Progress See link on the course website: