Chapter 3

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

2. Core Case Study: Have You Thanked the Insects Today? • Many plant species depend on insects for pollination. • Insect can control other pest insects by eating them Figure 3-1

3. Core Case Study: Have You Thanked the Insects Today? • …if all insects disappeared, humanity probably could not last more than a few months [E.O. Wilson, Biodiversity expert]. • Insect’s role in nature is part of the larger biological community in which they live.

4. THE NATURE OF ECOLOGY • Ecology is a study of connections in nature. • How organisms interact with one another and with their nonliving environment. Figure 3-2

5. CO2 O2 Nutrients Ecology • Ecology: the study of the relationships between organisms & the abiotic (nonliving) and biotic (living) environment. • The physical conditions influence the habitat in which an organism lives. These include: • substrate • humidity • sunlight • temperature • salinity • pH (acidity) • exposure • altitude • depth • Each abiotic (or physical) factor may be well suited to the organism or it may present it with problems to overcome.

6. Universe Galaxies Biosphere Solar systems Planets Earth Biosphere Ecosystems Ecosystems Communities Populations Realm of ecology Organisms Communities Organ systems Organs Tissues Cells Populations Protoplasm Molecules Atoms Organisms Subatomic Particles Fig. 3-2, p. 51

7. Community Population Biosphere Ecosystem Individual Biome Biological Complexity • Living organisms can be studied at different levels ofcomplexity. • From least to most complex, these levels are (in an ecological context): • Individual • Population • Community • Ecosystem • Biome • Biosphere

8. Organisms and Species • Organisms, the different forms of life on earth, can be classified into different species based on certain characteristics. Figure 3-3

9. Other animals 281,000 Known species 1,412,000 Insects 751,000 Fungi 69,000 Prokaryotes 4,800 Plants 248,400 Protists 57,700 Fig. 3-3, p. 52

10. Case Study: Which Species Run the World? • Multitudes of tiny microbes such as bacteria, protozoa, fungi, and yeast help keep us alive. • Harmful microbes are the minority. • Soil bacteria convert nitrogen gas to a usable form for plants. • They help produce foods (bread, cheese, yogurt, beer, wine). • 90% of all living mass. • Helps purify water, provide oxygen, breakdown waste. • Lives beneficially in your body (intestines, nose).

11. Populations, Communities, and Ecosystems • Members of a species interact in groups called populations. • Populations of different species living and interacting in an area form a community. • A community interacting with its physical environment of matter and energy is an ecosystem.

12. Populations • A population is a group of interacting individuals of the same species occupying a specific area. • The space an individual or population normally occupies is its habitat. Figure 3-4

13. Populations • Genetic diversity • In most natural populations individuals vary slightly in their genetic makeup. Figure 3-5

14. Community • The population of all species living & interacting in an area.

15. Ecosystems • Ecosystems consist of nonliving (abiotic) and living (biotic) components. Figure 3-10

16. The Biosphere • The biosphere is the region within which all living things are found on Earth, extending from the bottom of the oceans to the upper atmosphere. • The biosphere is but one of the four separate components of the geochemical model along with the lithosphere, hydrosphere, and atmosphere. • The Gaia Hypothesis maintains that the Earth is a single self-regulating complex evolving system. An example being the exchange of elements between oceans and land.

17. THE EARTH’S LIFE SUPPORT SYSTEMS • The biosphere consists of several physical layers that contain: • Air • Water • Soil • Minerals • Life Figure 3-6

18. Biosphere • Atmosphere • Membrane of air around the planet. • Stratosphere • Lower portion contains ozone to filter out most of the sun’s harmful UV radiation. • Hydrosphere • All the earth’s water: liquid, ice, water vapor • Lithosphere • The earth’s crust and upper mantle.

19. Oceanic Crust Continental Crust Atmosphere Vegetation and animals Biosphere Lithosphere Soil Upper mantle Crust Asthenosphere Rock Lower mantle Core Mantle Crust (soil and rock) Biosphere (living and dead organisms) Hydrosphere (water) Lithosphere (crust, top of upper mantle) Atmosphere (air) Fig. 3-6, p. 54

20. Habitat • An organism’s habitat is the physical place or environment in which it lives. • Organisms show a preference for a particular habitat type, but some are more specific in their requirements than others. Most frogs, like this leopard frog, live in or near fresh water, but a few can survive in arid habitats. Lichens, fungi & algae or bacteria, are found on rocks, trees, and bare ground.

21. Habitat Needs • Cover – shelter; trees, shrubs, etc. • Water • Nutrients

22. Macronutrients • Chemicals organisms need in large numbers to live, grow, and reproduce. • Ex. carbon, oxygen, hydrogen, nitrogen, calcium, and iron.

23. Micronutrients • These are needed in small or even trace amounts. • Ex. sodium, zinc copper, chlorine, and iodine.

24. Ecological Niche Adaptations • The ecological niche describes the functional position of an organismin its environment. • A niche comprises: • the habitat in which the organism lives. • the organism’s activity pattern: the periods of time during which it is active. • the resources it obtainsfrom the habitat. Habitat Activity patterns Presence of other organisms Physical conditions

25. The Fundamental Niche • The fundamental niche of an organism is described by the full range of environmental conditions (biological and physical) under which the organism can exist. • The realized niche of the organism is the niche that is actually occupied. It is narrower than the fundamental niche. • This contraction of the realized niche is a result of pressure from, and interactions with, other organisms.

26. Factors That Limit Population Growth • Availability of matter and energy resources can limit the number of organisms in a population. Figure 3-11

27. Tolerance range Too acidic Too alkaline Optimum range pH Examples of abiotic factors that influence size of the realized niche Too cold Temperature Too hot Law of Tolerance • The law of tolerance states that “For each abiotic factor, an organism has a range of tolerances within which it can survive.” Number of organisms Unavailable niche Marginal niche Preferred niche Marginal niche Unavailable niche

28. Factors That Limit Population Growth • The physical conditions of the environment can limit the distribution of a species. Figure 3-12

29. Limited Resources Population Growth Cycle • A population can grow until competition for limited resources increases & the carrying capacity (C.C.) is reached.

30. Typical Phases • 1. The population overshoots the C.C. • 2. This is because of a reproductive time lag (the period required for the birth rate to fall & the death rate to rise). • 3. The population has a dieback or crashes. • 4. The carrying capacity is reached.

31. What Happens to Solar Energy Reaching the Earth? • Solar energy flowing through the biosphere warms the atmosphere, evaporates and recycles water, generates winds and supports plant growth. Figure 3-8

32. Producers: Basic Source of All Food • Most producers capture sunlight to produce carbohydrates by photosynthesis:

33. Producers: Basic Source of All Food • Chemosynthesis: • Some organisms such as deep ocean bacteria draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide (H2S) gas .

34. Photosynthesis: A Closer Look • Chlorophyll molecules in the chloroplasts of plant cells absorb solar energy. • This initiates a complex series of chemical reactions in which carbon dioxide and water are converted to sugars and oxygen. Figure 3-A

35. Sun Chloroplast in leaf cell Chlorophyll H2O O2 Light-dependent Reaction Energy storage and release (ATP/ADP) Glucose Light-independent reaction CO2 Sunlight 6CO2 + 6 H2O C6H12O6 +6 O2 Fig. 3-A, p. 59

36. Consumers: Eating and Recycling to Survive • Consumers (heterotrophs) get their food by eating or breaking down all or parts of other organisms or their remains. • Herbivores • Primary consumers that eat producers • Carnivores • Primary consumers eat primary consumers • Third and higher level consumers: carnivores that eat carnivores. • Omnivores • Feed on both plant and animals.

37. Decomposers and Detrivores • Decomposers: Recycle nutrients in ecosystems. • Detrivores: Insects or other scavengers that feed on wastes or dead bodies. Figure 3-13

38. Scavengers Decomposers Termite and carpenter ant work Carpenter ant galleries Bark beetle engraving Long-horned beetle holes Dry rot fungus Wood reduced to powder Mushroom Time progression Powder broken down by decomposers into plant nutrients in soil Fig. 3-13, p. 61

39. Aerobic and Anaerobic Respiration: Getting Energy for Survival • Organisms break down carbohydrates and other organic compounds in their cells to obtain the energy they need. • This is usually done through aerobic respiration. • The opposite of photosynthesis

40. Aerobic and Anaerobic Respiration: Getting Energy for Survival • Anaerobic respiration or fermentation: • Some decomposers get energy by breaking down glucose (or other organic compounds) in the absence of oxygen. • The end products vary based on the chemical reaction: • Methane gas • Ethyl alcohol • Acetic acid • Hydrogen sulfide

41. Two Secrets of Survival: Energy Flow and Matter Recycle • An ecosystem survives by a combination of energy flow and matter recycling. Figure 3-14

42. Decomposition • As plant or animal matter dies it will break down and return the chemicals back to the soil. • This happens very quickly in tropical rainforest which results in low-nutrient soils. • Grasslands have the deepest and most nutrient rich of all soils

43. BIODIVERSITY Figure 3-15

44. Biodiversity Loss and Species Extinction: Remember HIPPO • H for habitat destruction and degradation • I for invasive species • P for pollution • P for human population growth • O for overexploitation

45. Biodiversity Loss and Species Extinction: Remember HIPPCO • H for habitat destruction and degradation • I for invasive species • P for pollution • P for human population growth • C for Climate Change • O for overexploitation

46. Why Should We Care About Biodiversity? • Biodiversity provides us with: • Natural Resources (food water, wood, energy, and medicines) • Natural Services (air and water purification, soil fertility, waste disposal, pest control) • Aesthetic pleasure

47. Solutions • Goals, strategies and tactics for protecting biodiversity. Figure 3-16

48. ENERGY FLOW IN ECOSYSTEMS • Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem. Figure 3-17

49. Food Webs • Trophic levels are interconnected within a more complicated food web. Figure 3-18

50. Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs • In accordance with the 2nd law of thermodynamics, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web.