Transcript Unit 4 PP
Ecosystems Unit 4 What do you know? • We are going to see what your prior knowledge of ecosystems is before we start the unit. • If you agree with the statement, you will move to west side of the room. • If you disagree with the statement, you will move to the east side of the room. •Ecosystems are not an organized whole, but a collection of organisms. •Forest fires are harmful to terrestrial ecosystems and should not be allowed to burn. •An organism cannot change trophic levels. •An animal that is high on the food web preys on all populations below it. •The top of the web has the most energy. • Characteristics of a population are created according to the needs of the individual or according to a predetermine grand plan. • Characteristics are passes on by the bigger, stronger organisms. • Species live together in an ecosystem because they have compatible needs and behaviors. • A change in the prey population has not effect on the predator. FOOD WEBS SECTION 1: INTRODUCTION • Ecology=study of relationships in nature • Organisms & environments • Between same species • Between different species • Between organisms and matter/energy SECTION 1: INTRODUCTION • Change is constant • Sometimes very slow • Ecologists’ skills= counting, observing, & patience SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • Geography affects ecosystems • Circulation patterns & climate zones • Most important factors= temp. ranges, moisture availability, light, & nutrient availability SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • Biome= broad geographic zone whose plants & animals are adapted to different climate patterns • Biomes can stretch across the globe • Temp. & precipitation vary by latitude SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • Each biome is made of ecosystems • Many different ways to organize biomes • Temperature, rainfall, vegetation, biomass, diverstity, etc. SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • Biomes named for vegetation • Soil varies from biome to biome SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • ¾ of Earth is covered in aquatic biomes • Large bodies of water are stratified (layered) • Aquatic biomes change daily or seasonally • Intertidal zone • Freezing • Drying out SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • Oceans are large and continuous • Freshwater vary in size • Freshwater organisms must be adapted to wide range of conditions • Must be able to move when neededor they will die SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • The same biome has similar organisms wherever they are on Earth • Organisms might not be related • Species are not evenly spread • Tropics have most biodiversity (measured in species richness) • High latitudes have low biodiversity SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES SECTION 2: MAJOR TERRESTRIAL & AQUATIC BIOMES • Biodiversity is not even because • High productivity in tropics=more species • Tropics not affected by glaciers, having more time to develop • Tropics are stable and predictable • More predators & pathogens limit competition • Disturbances occur infrequently enough to allow for successional diversity SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Energy/nutrients are constantly cycled • 1st trophic level=producers • Use solar energy • 2nd trophic level=herbivores • 3rd trophic level= predators • 4th & higher=predators of predators SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Organisms that feed on different levels are @ the highest trophic level • Decomposers return nutrients to the soil • 10% of energy moves from one trophic level to the next • Loss of energy is due to: respiration, growth, reproduction, defecation, & non predatory death. SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Decomposers=most important for energy flow • They process large amounts of material and return energy to the soil for primary producers • Not all energy goes back to producers • Some released as heat (compost) SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • GPP=gross primary productivity • Total organic matter produced from photosynthesis • NPP=net primary productivity • Energy for plant growth after subtracting plant respiration SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Productivity of plants rises with temperature • (until 30 degrees Celsius) • Positively related to moisture • Highest productivity occurs in warm, wet zones SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Ocean productivity is controlled by light and nutrients • Marine productivity is highest near coasts • Upwelling & Runoff • Algal beds and coral reefs have highest production SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • # Trophic levels depends on amount of energy, energy loss and type of organisms • Higher trophic levels=larger organisms • Must eat lots and forage over large areas SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Most land ecosystems have at most 5 trophic levels • Marine have at most 7 SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Simplest way to describe energy flow is a food chain (energy only flows one way) • A more accurate description is a food web. SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS SECTION 3: ENERGY FLOW THROUGH ECOSYSTEMS • Contaminants collect in organisms and are passed along with energy (bioaccumulation) • Contaminant levels increase as you go up in trophic level • Higher levels have to eat a lot of lower level organisms • DDT in eagles • Mercury in humans SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS • M0st important cycles for ecosystems are water, carbon, nitrogen, and phosphorus cycles • Earth is mostly water • 97% oceans, 2% ice caps & glaciers, the rest is groundwater, atmosphere, & useable water SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS • Land & ocean ecosystems are important sinks for carbon to reduce the amount in the atmosphere • Humans generate 7 billion plus tons of carbon per year • 3 billion remain in the atmosphere • Plants can only take in so much before they run out of other nutrients SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS • Nitrogen & phosphorus limit growth if there isn’t enough • Atmospheric carbon cannot be used by plants • Nitrogen-fixing bacteria take N2 from the atmosphere and convert to NH4 & NO3 for plants SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS • Some plants have a mutualistic relationship with nitrogen fixing bacteria on their roots (legumes) • Farmers can plant these to return nitrogen to the soil naturally (crop rotation) SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS • Human activities alter the nitrogen cycle, adding more to land ecosystems • This adds more to aquatic ecosystems • Algal blooms deplete oxygen in water • Acid rain SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS • Phosphorus flows slowly • Soil pH determines the phosphate availability • Low pH=phosphorus stuck in clay • High pH=stuck in iron/aluminum • Best pH is 6-7 SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS • Excessive phosphorus creates eutrophication in water (algal blooms) SECTION 4: BIOGEOCHEMICAL CYCLING IN ECOSYSTEMS SECTION 5: POPULATION DYNAMICS • Life history strategy= an organism’s way of dividing energy between growing, surviving, & reproducing • Optimal life history strategy=maximizes organism’s contribution to population growth SECTION 5: POPULATION DYNAMICS • Unstable area=organisms grow/reproduce quickly • Produce many offspring so some may survive • Stable area=organisms grow/reproduce slowly • Use more energy for growth and competing for resources SECTION 5: POPULATION DYNAMICS • R-selected organisms= unstable environment • Low population levels compared to carrying capacity • Population can grow exponentially at max rate if resources are not limited • Insects, annual plants, bacteria, frogs, rats • pests SECTION 5: POPULATION DYNAMICS • R-selected organisms • Small • Short life • Opportunistic • Irregular boom-bust population cycles • Rapid growth when conditions are favorable SECTION 5: POPULATION DYNAMICS • K-selected organisms=stable environment • Population level is at or near carrying capacity • Large mammals, birds, long-lived plants SECTION 5: POPULATION DYNAMICS • K-selected organisms • Larger • Grow slowly • Few offspring • Long time parenting offspring • Prone to extinction more than r-selected SECTION 5: POPULATION DYNAMICS Feature Norway rat (r-selected) African elephant (Kselected) Reaches sexual or reproductive maturity 3-4 months 10-12 years Average gestation period 22-24 days 22 months Time to weaning 3-4 weeks 48-108 months Breeding interval (female) Up to 7 times per year Every 4 to 9 years Offspring per litter 2-14 (average 8) 1 average, 2 high SECTION 5: POPULATION DYNAMICS • Most organisms are in between r & k selected • Early stages of ecosystems are settled by rselected and then shift towards k-selected SECTION 5: POPULATION DYNAMICS • Survival & reproduction rates don’t stay constant • Resource limitations reduces one/both • Populations grow fastest when they are close to zero • Max population growth rate (N)=K/2 • K is the carrying capacity SECTION 6: REGULATION OF ECOSYSTEMS FUNCTIONS • Resources limit an ecosystem • Essential resource= in minimum amount not available growth doesn’t occur • Substitutable resource= either resource could be used • Complementary resource= a small amount of one resource can be used as a large amount of another SECTION 6: REGULATION OF ECOSYSTEMS FUNCTIONS • “Bottom-up” control= energy flow controls the higher trophic levels • “Top-down” control= abundance of high trophic level organisms dictate • Scientists have found that controlling the activities at higher trophic levels have a higher impact than controlling lower levels SECTION 6: REGULATION OF ECOSYSTEMS FUNCTIONS • Trophic cascades=drastic domino effects felt at lower levels when the top of the food web is changed • Keystone species=organisms vital to the entire ecosystem • They occupy a niche that influences other many other species • Reintroducing wolves to Yellowstone had a positive effect • Other changes could be extremely catastrophic SECTION 7: ECOLOGICAL NICHES • Different species interact in different ways in ecosystems • Positive, negative, or neutral impacts SECTION 7: ECOLOGICAL NICHES • Competition=both species harmed (oak trees compete with maple trees for light) • Predation/Parasitism= one species benefits, one is harmed (wolf preying on rabbit, flea parasitism on wolf) • Mutualism= both species benefit, not necessarily essential (humans and pets, insects pollinating flowers • Commensalism=one species benefits, one is not affected (maggots and a rotting carcass) SECTION 7: ECOLOGICAL NICHES • Niche= range of tolerance an organism can live • Species can occupy different niches if need be • Competitive exclusion principle=if 2 competitors try to occupy the same niche, one will die off SECTION 7: ECOLOGICAL NICHES • Narrow niches have specialists • Sensitive to changes • Endangered species • Broad niches have generalists • Adaptable organisms SECTION 8: EVOLUTION AND NATURAL SELECTION IN ECOSYSTEMS • Relationships between predators, prey, & competitors contribute to natural selection & evolution • The common goal for survival drives natural selection of different traits/behaviors SECTION 8: EVOLUTION AND NATURAL SELECTION IN ECOSYSTEMS • Mimicry=resembling something else • Eating the most efficient food source for energy • Avoidance & escape features/behaviors • Physical features (spines, shells, etc.) • Toxins SECTION 8: EVOLUTION AND NATURAL SELECTION IN ECOSYSTEMS • Natural selection is driven by survival • Predator-prey “arms races” • Tiger moths jamming bat signals • Moving to different niches to avoid competition SECTION 9: NATURAL ECOSYSTEM CHANGE • Succession=changing from one natural community to another over many years to centuries • Primary= colonizing new land (bare rock/lava flow) • Secondary=return of natural vegetation after fire or other removal of vegetation SECTION 9: NATURAL ECOSYSTEM CHANGE • R-selected organisms thrive after disasters • K-selected organisms need stability • K-selected organisms outcompete R-selected • As ecosystems mature, they become more diverse & complex SECTION 9: NATURAL ECOSYSTEM CHANGE