BI 101 Food webs and Ecosystems

Transcription

1 BI 101 Food webs and Ecosystems Learning objectives Name the inputs and outputs of photosynthesis, and how this relates to respiration. Understand the importance of light wavelengths in photosynthesis. Describe the flow of energy through the ecosystem, and understand how this affects the biomass of tropic levels Understand the cycling of nutrients such as carbon and water Recognize how impacts to the nutrient cycles affect the whole community 1

2 Levels of study in Ecology Organism Population Community Ecosystem Biosphere What is an ecosystem? The Laws of Thermodynamics A set of universal laws governing all energy changes in the universe The First Law of Thermodynamics Total amount of energy in the universe remains constant Energy cannot be created nor destroyed However, it can change forms During each conversion, some energy is lost into the environment as heat energy 4 2

3 The Second Law of Thermodynamics Disorder in closed systems is continuously Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. increasing Disorder happens "spontaneously" Entropy is a measure of the disorder of a system Simply put, the Second Law states: entropy increases Organization requires energy (both): Keith Eng, 2008 Figure 5.3 Entropy in action 5 Overview of photosynthesis Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cross-section of leaf Cuticle Epidermis Mesophyll Vascular bundle Bundle sheath Stoma Vacuole Nucleus Cell wall Chloroplasts Thylakoid Mesophyll cell Inner membrane Outer membrane Granum Stroma Chloroplast (Right): Roger Brooks/Beateworks/Corbis RF 6 3

4 Plant Anatomy: Vegetative Organs Leaves: Stem: Photosynthesis Gas exchange Light absorption Support Transport Storage Roots: Anchorage Storage Transport Absorption Form = Function leaf blade leaf vein Leaf Vein (one vascular bundle) cuticle Upper Epidermis Palisade Mesophyll stem xylem Water, dissolved mineral ions from roots and stems move into leaf vein (blue arrow) phloem Photosynthetic products (pink arrow) enter vein, will be transported throughout plant body Oxygen and water vapor diffuse out of leaf at stomata. Carbon dioxide in outside air enters leaf at stomata. Spongy Mesophyll Lower Epidermis cuticle-coated cell of lower epidermis one stoma (opening across epidermia) 50 m Fig , p.501 4

5 Making Energy - Photosynthesis Chloroplasts contain the pigment chlorophyll. Chlorophyll a & b Photosynthesis: The Components??? What are the inputs? What are the outputs??? 5

6 Photosynthesis: The Components 6CO 2 + 6H 2 O + Light energy C 6 H 12 O 6 + 6O 2 What are the inputs? - light - water - carbon dioxide What are the outputs? - glucose - oxygen Light is a wave of energy: colors are different wavelengths 6

7 Photosynthesis: Input - Light Intensity The color you see Energy (wavelength) absorbed Photosynthesis: Light Absorption Plants are green because Reflect green light. Absorb red, blue and purple light. 7

8 Photosynthesis: Light Absorption Plant pigments absorb light. Absorb red, blue and purple light Reflect green light Autumnal Changes in Leaf Color Chloroplasts of mature leaves contain several groups of pigments: Chlorophylls - Green Carotenoids - Yellows In fall, chlorophylls break down first and other colors are revealed! 8

9 Discussion Question What would happen if a leaf lacked carotenoids? a. The leaf would absorb all energy levels b. The leaf would turn yellow/orange during the fall c. The leaf would not absorb Carbon dioxide d. Photosynthesis would not be as efficient e. The leaf would require oxygen Photosynthesis: The Components 6CO 2 + 6H 2 O + Light energy C 6 H 12 O 6 + 6O 2 What are the inputs? - light - water - carbon dioxide What are the outputs? - glucose - oxygen 9

10 Guard Cells Vascular plants: have stomata 10

11 Discussion Question What would happen to the rate of photosynthesis if the light levels remained the same and the carbon dioxide levels were increased. a. Rate of photosynthesis would increase b. Rate of photosynthesis would decrease c. Rate of photosynthesis would remain the same d. There is no relationship among the two Plants and Respiration Photosynthesis: 6 CO H 2 O + Light Energy C 6 H 12 O O 2 Respiration: C 6 H 12 O O 2 6 CO H 2 O + Energy 11

12 Food webs Primary producers the autotrophs Auto = self + trophy = nourishment Organisms take nourishment directly from the environment Phytoplankton ocean Terrestrial plants et/biology/eco_water. html ag.com/know002. html 12

13 Consumers heterotrophs Hetero = other + trophy = nourishment Food webs 13

14 Detrital food web Discussion Question Which trophic level is incorrectly matched with its function? a. Primary producer autotrophic organisms b. Primary consumer consumes producers c. Secondary consumer consumes primary consumers d. Primary producer consumes plants e. All of the above are correctly matched. 14

15 Trophic levels within an ecosystem Detrivores (also known as scavengers) are special consumers that eat dead organisms Decomposers are organism that break down organic substances, making them available to other organisms bacteria and fungi are the principal decomposers in land ecosystems Copyright The Tertiary McGraw-Hill consumer Companies, Inc. Permission required for reproduction or display. Trophic level 4 Trophic level 3 Trophic level 2 Trophic level 1 Secondary consumer Primary consumer Producer Decomposers Top carnivore Carnivore Herbivore Bacteria 29 Sun Fungi Discussion Question: The world is green Three hundred trout are needed to support one man for a year. The trout, in turn, must consume 90,000 frogs, that must consume 27 million grasshoppers that live off of 1,000 tons of grass. -- G. Tyler Miller, Jr., American Chemist (1971) Q: Why do we observe less predator biomass and more prey and plant biomass? 15

16 Energy pathways in ecosystems All ecosystems need energy so its living members can grow and reproduce Source of energy = the sun One-way path Flows through various organisms, and eventually dissipates into the environment as heat Energy Flows Through Ecosystems How heterotrophs use (and lose) food energy 17% Growth Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 33% Cellular respiration 50% Feces Much of the energy captured by plants is lost as energy passes through the ecosystem 16

17 The 10% rule About 10% of the energy is retained from one food level to the next. Acquiring and digesting food takes up energy! Not all of the prey/plant/host can be eaten and/or digested 17

18 Discussion Questions: What does it mean to eat low on the food chain? In terms of the energy pyramid, why do some people think it is important for us to do so? Food Supply Energy Pyramid Energy is used much more efficiently if humans eat plants (first tropic level) instead of meat (second tropic level). A given area of farmland can support more people if the crops are fed directly to people rather than to livestock that people then eat. For example if a man needs 3,000 Calories per day, then 30,000 Cal beef are needed, which in turn need 300,000 Cal of corn. This works out to be 1.5 acres of corn per day per person. If the person ate corn directly then 10 people could be supported by the same 1.5 acres of corn. 18

19 Biogeochemical Cycles In contrast to the one-way flow of energy, materials (such as water, carbon and nitrogen) cycle through ecosystems. Water cycle Carbon cycle Nitrogen cycle Phosphorus cycle Water cycle 19

20 Burning or clear-cutting forests breaks the water cycle 20

21 Grandma Johnson Problem Grandma Johnson had very sentimental feelings toward Johnson Canyon, Utah, where she and her late husband had honeymooned long ago. Her feelings toward this spot were such that upon her death she requested to be buried under a creosote bush overlooking the canyon. Trace the path of a carbon atom from Grandma Johnson s remains to where it could become part of a coyote. Your path must contain at least one plant in it. (NOTE: the coyote will not dig up Grandma Johnson and consume any of her remains). 21