Ecosystems: What are They and How Do T hey W ork?

1. Ecosystems: What are They and How Do They Work? Chapter 3

2. What Is Ecology? Ecology is the study of how organisms interact with one another and with their physical environment of matter and energy.

3. Cells Are the Basic Units of Life • Cells: the smallest and most fundamental unit of life • Cell theory: all living things are made up of cells • Eukaryotic vs. prokaryotic

4. Cells Are the Basic Units of Life

5. Ecologists Study Connections in Nature • Ecology: The study of how organisms interact with their biotic and abiotic environment • Levels of organization

6. Ecologists Study Connections in Nature

7. What Keeps Us and Other Organisms Alive? Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere and gravity.

8. The Earth’s Life-Support System Has Four Major Components Biosphere Atmosphere Hydrosphere Geosphere

9. Three Factors Sustain Life on Earth • The one way flow of high-quality energy • The cycling of matter or nutrients • Gravity

10. What Happens to Solar Energy Reaching the Earth? • We get electromagnetic waves: visible light, UV radiation, heat • Absorbed by the earth’s atmosphere, clouds and surface –OR- • Reflected back into space (most of the energy) • Maintains sufficient temperature for life  powers the water cycle • 0.1% of total energy reaching the surface powers photosynthesis.

11. What Happens to Solar Energy Reaching the Earth? • Greenhouse Effect • Greenhouse gases: water vapor, CO2, methane, nitrous oxide, ozone • Hold on to heat and make life possible on Earth • Human activities are increasing the amount of some greenhouse gases • CO2: burning of fossil fuels, deforestation, etc. • Methane and nitrous oxide: more livestock.

13. What Are the Major Components of an Ecosystem? Ecosystems contain living (biotic) and nonliving (abiotic) components. Some organisms produce the nutrients they need, others get their nutrients by consuming other organisms, and some recycle nutrients back to producers by decomposing the wastes and remains of organisms.

14. Ecosystems Have Living and Nonliving Components • Abiotic • Nonliving • Ex. Water, air, rocks, heat, nutrients, etc. • Biotic • Living or once living • Ex. Plants, animals, microbes, dead things, etc.

15. Ecosystems Have Living and Nonliving Components • Different organisms thrive under different conditions • Range of tolerance • May vary by age, health, or genetics in a given population • Outside of this range, it is difficult for a population to survive.

17. Several Abiotic Factors Can Limit Population Growth • Limiting factor principle: Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance • Biggest limiting factor on land is usually water • Aquatic limiting factors include temperature, sunlight, and salinity.

18. Producers and Consumers Are the Living Components of Ecosystems • Producers • Aka autotrophs (literally “self feeding) • Make their own food from inorganic material through photosynthesis or chemosynthesis • Photosynthesis  plants • Chemosynthesis  some bacteria.

19. Producers and Consumers Are the Living Components of Ecosystems • Consumers • Aka heterotrophs (literally “other feeding”) • Must consume other organisms or their remains for energy • Ex. Animals and fungus

21. Consumers • Primary consumers • Herbivores • Ex. Rabbits, grasshoppers, etc. • Secondary consumers • Carnivores • Ex. Spiders, birds, etc. • Third level and up consumers • Carnivores • Ex. Wolves, tigers, etc.

22. Consumers • Omnivores • Feed on both plants and animals • Ex. Humans, pigs, cockroaches, etc. • Decomposers • Feed on dead organisms • Ex. Fungi and bacteria • Detritivores • Feed on the wastes or dead bodies of organisms • Ex. Mites, earthworms, vultures, etc.

23. Energy • All organisms get their energy through respiration • Aerobic respiration • Uses oxygen to release energy from glucose • In general, opposite process of photosynthesis • Anaerobic respiration • Occurs in the absence of oxygen • Results in fermentation (ex. Alcohol and lactic acid).

24. Energy Flow and Nutrient Cycling • Remember: One-way energy flow and nutrient cycling (2 scientific principles of sustainability) • Decomposers and detritivores (often microscopic organisms) are crucial to this process because they break down organic matter to be used again

25. What Happens to Energy in an Ecosystem? Energy flows through ecosystems in food chains and webs. As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.

26. Energy Flows through Ecosystems in Food Chains and Food Webs FOOD CHAIN!!!! • Chemical energy stored as nutrients flows through ecosystems from one trophic level to the next • Plant  Caterpillar  Robin  Hawk • Decomposers and detritivores consume all of them when they die • Every time we go from one level of the chain to the next, most energy is lost to heat and metabolic activities.

27. Food Chains and Food Webs • Most consumers feed on more than one type of organism, and most organisms are eaten by more than one type of consumer • Food webs are illustrations of the complex network of possible food chains in a given ecosystem.

28. Food Chain

29. Food Web

30. Usable Energy Decreases with Each Link in a Food Chain or Web • Biomass: dry weight of all organic matter contained in a single or group of organisms • When an organism is consumed by another, the chemical energy stored in its biomass is transferred to the consumer • With each transfer, some usable chemical energy is lost as heat.

31. Ecological Efficiency • Percentage of usable chemical energy transferred from one trophic level to the next • Ranges from 2-40% depending on the organisms, but 10% is about average • Because of this, the image of a pyramid is helpful to illustrate energy flow.

32. Energy Pyramid Populations in an Ecosystem Biomass in an Ecosystem

33. Interesting factoid • Energy pyramids show how the earth can support more people if they eat at lower trophic levels (i.e. less meat, more veggies and other plants)

34. GPP, NPP and ABC • Gross primary productivity (GPP): • the rate at which an ecosystem’s producers (usually plants) convert solar energy into chemical energy • Measured in energy production per unit area per time span (ex. kcal/m2/year) • Net primary productivity(NPP): • the rate at which energy is produced minus the rate at which the energy is used (respiration) • NPP = GPP – R.

35. NPP

36. What Happens to Matter in an Ecosystem? Matter, in the form of nutrients, cycles within and among ecosystems in the biosphere, and human activities are altering these chemical cycles.

37. Water Cycle • Aka hydrologic cycle Transpiration

38. Water Cycle and Humans • Withdrawal of freshwater from streams, lakes and underground • Clear vegetation for agriculture and development • Increased flooding.

39. Carbon Cycle • Movement depends on the cycle of photosynthesis and cellular respiration • Humans and the carbon cycle  increasing levels of CO2 • Clearing of trees and other plants • Burning of fossil fuels and wood.

40. Nitrogen Cycle • Most nitrogen is found in our atmosphere as a gas (78% of our atmosphere) • Important for organisms because it is a building block of proteins • Atmospheric nitrogen is made usable by nitrogen-fixing bacteria • Then absorbed by plants, which are then eaten by consumers • Returned back to the atmosphere/cycle through waste and decay of dead organisms.

41. Nitrogen Cycle and Humans • Burning of fossil fuels (nitric oxide)  acid rain • Livestock wastes and inorganic fertilizers increase nitrous oxide (greenhouse gas) • Destruction of forests, grasslands, and wetlands • Agricultural runoff and sewage • Nitrogen rich crops.

42. Phosphorous Cycle • Does not include the atmosphere as it cycles through an ecosystem • Very slow in comparison to other cycles • Important for ATP • Usable form is in rocks and soil • Human impact  increased flooding, runoff and erosion cause phosphates to be “lost” for long periods of time in the ocean.

43. Sulfur Cycle • Slow moving nutrient • Found mostly in rocks and deep-ocean sediment • Human impact • Burning fossil fuels • Fossil fuel refining process • Metal refining process.