ENVIRONMENTAL SCIENCE

1. ENVIRONMENTALSCIENCE CHAPTER 3:Ecosystems: What Are They and How Do They Work?

2. Core Case Study: Tropical Rainforests Are Disappearing • Found near the equator • At one time covered 14% land surface, now covers only 2% • ~50% world’s known terrestrial plant and animal species • ≥50% destroyed or disturbed by humans • Cutting trees • Growing crops • Grazing cattle • Building settlements

3. Core Case Study: Tropical Rainforests Are Disappearing • Consequences of disappearing tropical rainforests • Decreased biodiversity as species become extinct • Accelerated global warming: fewer trees to remove carbon dioxide from the atmosphere • Changes regional weather patterns: can lead to increase in tropical grasslands

4. Sect. 3.1:What Keeps Us and Other Organisms Alive? • Concepts to learn in 3.1: 1. The four major components of the earth’s life-support system are the atmosphere (air), the hydrosphere (water), the geosphere (rock, soil, sediment), and the biosphere (living things). 2. Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.

5. Earth Has Four Major Life-Support Components 1. Atmosphere: Thin layer of gases, surrounding earth’s surface. Consists of: a. Troposphere: contains the air we breathe (look up mixture) & greenhouse gases b. Stratosphere: contains ozone, which filters UV rays, allowing for life to exist • Hydrosphere: contains all of the water on or near the earth’s surface a. Which water source makes up the largest component?

6. Earth Has Four Major Life-Support Components • Geosphere: 3 parts: a. Core (extremely hot, mostly liquid rock) b. Mantle (mostly rock) c. Crust (thin outer layer) • Biosphere: includes all the parts of the atmosphere, hydrosphere & geosphere where life is found. a. “ecology” focuses on this area b. It is a very thin layer of the earth & atmosphere

7. Three Factors Sustain Life on Earth 1. One-way flow of high-quality energy from the sun 2. Cycling of matter or nutrients through parts of the biosphere 3. Gravity

8. Solar Energy Reaching the Earth (one way energy flow) • Sun’s energy reaches us as electromagnetic waves, seen as: 1. Visible light 2. UV radiation 3. Heat • Natural greenhouse effect: What effect does it have on the earth’s energy?

9. Solar Energy Reaching the Earth (one way energy flow) • The flow of energy in from the sun will equal the flow of energy out into the environment / atmosphere 1. Group discussion: a. How does this happen? b. Is this energy recycled?

10. Sect. 3.2: What Are the Major Components of an Ecosystem? • Some organisms produce the nutrients they need. • Some get the nutrients they need by consuming other organism. • Some recycle nutrients back to producers by decomposing the wastes and remains of organisms.

11. Ecology • Ecology: How organisms interact with biotic (living) and abiotic (non-living) environments • Ecology focuses on levels of matter ranging from the atomic level to the entire biosphere. 5 levels: 1. Organisms 2. Populations 3. Communities 4. Ecosystems 5. Biosphere

12. Nonliving Components of Ecosystems • Abiotic: non-living components of ecosystems, which includes: • Water • Air • Nutrients • Solar energy • Rocks • Heat

13. Living Components of Ecosystems • Biotic: living components of ecosystems, including: • Plants • Animals • Microbes • Dead organisms • Waste products of dead organisms • Waste products of living organisms

14. Trophic Levels • Trophic Levels:“feeding” levels assigned to every organism in an ecosystem 1. Producers- called autotrophs a. Produce food thru photosynthesis 2. Consumers – called heterotrophs a. Primary consumers – herbivores (eat plants) b. Secondary consumers – carnivores that eat herbivores • Third-level consumers – carnivores that eat carnivores • Omnivores– eat both plants and animals

15. Additional Trophic Levels • Decomposers: • Release nutrients from the dead bodies of plants and animals • Detrivores: • Feed on the waste or dead bodies of organisms

16. Production and Consumption of Energy • Photosynthesis • Carbon dioxide + water + solar energy glucose + oxygen • Aerobic respiration • Glucose + oxygen  carbon dioxide + water + energy

17. Energy Flow and Nutrient Recycling • Ecosystems are sustained through: 1. One-way energy flow from the sun 2. Nutrient recycling

18. Science Focus: Invisible Organisms • Microorganisms/Microbes • Bacteria • Protozoa • Fungi • Phytoplankton

19. Science Focus: Invisible Organisms • Microbes can cause disease • Malaria • Athlete’s foot • Microbes are also beneficial • Intestinal flora • Purify water • Phytoplankton remove carbon dioxide from the atmosphere

20. Sect. 3.3: What Happens to Energy in an Ecosystem? • As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.

21. Energy Flow in Ecosystems • The chemical energy stored in all organisms flows thru ecosystems from one trophic level to another • Food chain • Sequence of organisms, each of which serves as a source of food for the next • Includes food production, feeders, and decomposition • Food web • A more complex network of interconnected food chains. • Consumers feed on more than one organism • Organisms are eaten/decomposed by more than one organism

22. Usable Energy by Trophic Level • Energy flow thru food webs follows the second law of thermodynamics – energy lost as heat • Biomass: The dry weight of all organic matter contained in its organisms 1. Each trophic level has one, but biomass decreases with increasing trophic level • Ecological efficiency – of energy transferred thru food chains is typically 10%. • See “Pyramid of energy flow”, fig. 3-10 pg 47 1. shows variable energy transfer efficiency between trophic levels

23. Ecosystem efficiency in producing plant matter • The amount of biomass an ecosystem is capable of producing is determined by it’s efficiency in capturing solar energy and converting it to chemical energy in food. • Gross Primary Productivity (GPP): rate at which an ecosystems producers (mostly plants) convert solar energy into chemical energy (stored in biomass of their tissues) 1. plants do use some of their produced energy for their own respiration

24. Two Kinds of Primary Productivity • Net primary productivity (NPP): rate at which producers use photosynthesis to produce & store chemical energy minus the rate at which they use some energy thru aerobic respiration. • Planet’s NPP limits number of consumers • Humans use, waste, or destroy between 10-55% of earth’s total potential NPP • Human population is less than 1% of total biomass of earth’s consumers

25. 3-4 What Happens to Matter in an Ecosystem? • Concept 3-4 Matter, in the form of nutrients, cycles within and among ecosystems and in the biosphere, and human activities are altering these chemical cycles.

26. Biogeochemical Cycles • Also called “Nutrient cycles” • All cycles have a place where the nutrients accumulate, called reservoirs • These nutrient cycles connect all organisms through time! • Cycles are all driven by: 1. solar energy 2. gravity

27. Hydrologic Cycle • Water cycle is powered by the sun. Involves 3 processes: • Evaporation (from bodies of water) • Precipitation (rain, snow, sleet) • Transpiration – water evaporation from plant surfaces • Over bodies of water: most water vapor comes from the oceans – 84% • Over land: ~90% of water reaching the atmosphere comes from transpiration

28. The Water Cycle • As water moves thru its cycle, some will temporarily stored in: 1. Living parts of the ecosystems: a. EX: Plants roots pull water into plants, which is stored in chemical compounds, then moved thru the ecosystem by transpiration and by plants being consumed 2. glaciers 3. Aquifers: stores of groundwater under layers of rock, sand & gravel

29. The Water cycle • An important feature of the water cycle is that as water passes thru, there is a natural renewal of water quality. 1. In a sense, it is like a “water filter” which filters out impurities. • Lots of water is visible. How much of it is available to us as freshwater, usable for consumption? * about 0.024% of the total volume of water

30. Science Focus: Water’s Unique Properties • Holds water molecules together (called hydrogen bonding) • Water is liquid over a wide temperature range • It changes temperature slowly • Requires large amounts of energy to evaporate

31. Additional Unique Properties of Water • Dissolves a variety of compounds • Filters out UV light from the sun • Adheres to a solid surface – allows capillary action in plants • Expands as it freezes

32. Carbon Cycle • Based on carbon dioxide (CO2) • It circulates thru the biosphere, hydrosphere & atmosphere • CO2 makes up 0.038% of atmosphere’s volume • Major cycle processes that carbon cycles thru: • Aerobic respiration • Photosynthesis • Fossil fuel combustion and deforestation (both can lead to a build-up of CO2) • Fossil fuels add CO2 to the atmosphere will cause an increase in temperature (and a decrease in CO2 will decrease surface temperatures)

33. Nitrogen Cycle • Multicellular plants and animals cannot directly absorb and use atmospheric nitrogen (N2), which makes up most of the atmosphere (78%) 1. Nitrogen is extremely important to the building of proteins, vitamins & nucleic acids 2. Bacteria are our friends, because they convert N2 to a form which can be absorbed 3. There are 2 processes involved with this conversion: Nitrogen Fixation and Nitrification 4. There are 2 additional processes in the nitrogen cycle: Ammonification and Denitrification

34. Nitrogen Cycle • Nitrogen fixation: specialized bacteria in soil and green algae in aquatic environments combine N2 with H2 to produce ammonia (NH3) 1. Some is converted to NH4+ ions, and is absorbed by plants • Nitrification: NH3 and NH4+ is converted by special bacteria into nitrate ions (NO3-) 1. plants will use it to make proteins (amino acids) & nucleic acids & vitamins

35. Nitrogen Cycle • Ammonification: The process that decomposer bacterias accomplish when they eat decaying plants & animals, converting their nitrogen-containing compounds into ammonia or ammonium ions. • Denitrification: A specialized process of bacteria in watery soil & sediments of lakes & oceans, that convert ammonia & ammonia ions back into N2 gas, to be returned back into the nitrogen cycle again.

36. Phosphorus Cycle • Does not cycle through the atmosphere • Its obtained mostly from terrestrial rock formations & ocean floor sediments 1. water runs over rocks, slowly eroding off phosphorus salts (containing phosphate ions PO43-) • It is the slowest moving of all the cycles • The presence of phosphorus is a limiting factor on land and in freshwater ecosystems • Biologically important for producers and consumers 1. part of energy transfer molecules ADP & ATP 2. part of nucleic acids

37. Sulfur Cycle • Most sulfur stored in rocks and minerals, & in ocean sediments • Enters atmosphere through: 1. Volcanic eruptions and processes 2. Anaerobic decomposition in swamps, bogs, and tidal flats 3. Sea spray 4. Dust storms 5. Forest fires

38. Sulfur Cycle • Biologically important to producers & consumers 1. sulfur is an essential part of proteins 2. It is absorbed by plants thru their roots

39. 3-5 How Do Scientists Study Ecosystems? • Scientists use field research, laboratory research, and mathematical and other models to learn about ecosystems.

40. Field Research • Collecting data in the field by scientists that are actively in “the mud” • Remote sensing devices are also used to detect/scan the earths surface • Geographic information systems (GIS): used to interpret & display the information obtained thru remote sensing devices.

41. Laboratory Research • Simplified model ecosystems • Culture tubes • Bottles • Aquariums • Greenhouses • Chambers with controllable abiotic factors • How well do lab experiments correspond with the greater complexity of real ecosystems? • Is best for doing controlled experiments!

42. Scientific Studies of Ecosystems • Models can be used 1. Mathematical 2. Computer simulations • Models need to be fed real data collected in the field- baseline data before any meaningful interpretations can take place. • Models must also determine relationships among the key variables

43. Baseline Data to Measure Earth’s Health • A “baseline of data is needed in order to monitor any changes over time • Many ecosystems lack this baseline data • Call for massive program to develop baseline data