Ecological Succession

Transcription

1 Primary Climax Community Ecological Secondary (young) Secondary (old) Interdependence Within Environmental Systems 323

2 324

3 Interdependence within Environmental Systems Teacher Pages Purpose The purpose of this activity is to reinforce students understanding of the effect that natural and human-made events and processes have on ecological succession and how species and populations of organisms can change as a result of disturbances to an ecosystem. Correlations to Texas Essential Knowledge and Skills Note: Text with a line through it indicates this part of the TEKS is not being addressed in this activity. Some TEKS statements printed here end with a semicolon or the word and with nothing thereafter this indicates that further TEKS statements follow but are not included here. (11) Science concepts. The student knows that biological systems work to achieve and maintain balance. The student is expected to: (D) describe how events and processes that occur during ecological succession can change populations and species diversity. (Readiness standard) (2) Scientific processes. The student uses scientific methods and equipment during field and laboratory investigations. The student is expected to: (G) (H) Materials Envelopes (2) analyze, evaluate, make inferences, and predict trends from data; and (Incorporated) communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphic organizers, journals, summaries, oral reports, and technology-based reports. (Incorporated) The following materials are included in the blackline masters for this station, which are available on the enclosed DVD. Station Information sheet (1 per station) Model (1 per station) Cycle (1 per station) Natural Disturbance Cards (1 set per station) Processes and Events Cards (1 set per station) Student Pages (1 copy per student) Teacher Pages 325

4 STAAR Biology: Assessment Activities Supplementary Resources Doyle, Robert D.. Retrieved on August 12, 2011 from the website of the mathematics department at the University of North Texas: ~rdoyle/1720/ch25-ecosystems.pdf.. Retrieved on August 12, 2011 from the Department of Biology and Environmental Science at Marietta College: Advance Preparation 1. Print one copy of all the blackline masters for this station from the enclosed DVD using a color printer color is essential to the station activities. Make one copy of the Student Pages (including the glossary) for each student. 2. Laminate the Station Information sheet, the Cycle, and the Model (two pages). Be sure to tape the two pages of the Ecological Model together so that all four stages of succession are in the correct order. 3. Laminate and cut out the Processes and Events Cards and the Natural Disturbance Cards. Place each set of cards in a labeled envelope. Station Setup 1. Tape the Station Information sheet to the station table. Students will use this to confirm the station is set up correctly. 2. Place the Model, Cycle, and the envelopes containing the Natural Disturbance Cards and the Processes and Events Cards at the station. Procedures 1. When students arrive at the station, they should check the station setup against the station information sheet at the table. If anything is missing or out of place, the students should notify you. 2. Pass out a copy of the Student Pages to each student. Instruct students to work through the procedures and answer the questions with their teammate(s). 3. As students work through the station activity, circulate around the room, checking their work and responding to questions. 326 Teacher Pages

5 Guide to Student Responses Note: The suggested student responses presented below in italics represent the best possible answers to the student questions; actual student responses may vary. Essential Question How do the processes and events that occur within an ecosystem affect the species and populations of organisms that live in that ecosystem? The processes and events that occur within an ecosystem change the conditions found in the ecosystem. For example, as soil develops in a primary succession stage, the conditions become more favorable for a different species to migrate in and inhabit the ecosystem. The new species would not have been able to exist in the ecosystem before the pioneer species that first inhabited the ecosystem set the stage for new species survival. Activities and Questions 1. Place each card in the appropriate position on the Model sheet as shown in the example below. Continue until all cards are placed on the model. Note: Correct card placement is represented in the tables below. Autotrophs Organisms and weathering break down rock to form the foundation for soil. Some pioneer organisms die, adding organic material to the soil. Autotrophs inhabit the ecosystem. Primary Secondary (young) Heterotrophs No heterotrophic organisms inhabit the ecosystem. Autotrophs Pioneer species and weathering increase soil quality and quantity. Conditions become favorable to support other plant species. Heterotrophs Animal species that feed on a diverse population of plants first appear. Seeds are brought in by wind and other means. Pioneer species compete with prairietype plants. Teacher Pages 327

6 STAAR Biology: Assessment Activities Secondary (old) Autotrophs Soil continues to build and mature with the addition of organic materials. Pioneer species are replaced as the dominant organism by other species. Competition among plant species occurs for resources. Small shrubs and trees appear. Heterotrophs New species of animals appear, including those that feed on other animal species. Competition among species of animals is prominent. Diversity among plants provides stimulus for other types of animals to appear. Autotrophs Climax Community Heterotrophs Ecosystem communities have reached their capacity to support additional species of organisms. Forests replace other plant species as the dominant plant species. The community is self-sustaining and mature unless a disturbance occurs. 2. Why are there no heterotrophs in the primary succession stage? There are no heterotrophs inhabiting the ecosystem in the primary succession stage because the autotrophs are not able to support them until the end of the primary succession stage, when the soil conditions are better suited to support more diverse species of plants. 3. How do the processes and events that occur during the primary succession stage result in the appearance of more diverse populations of autotrophs in the first stage of secondary succession? In the primary succession stage, the process of chemical weathering and the event of lichen growth cause rocks to break down, forming soil. As some of the lichens die, they add organic material to the broken-down rock. This early stage of soil can now support other autotrophs that in turn attract the kinds of heterotrophs that feed on them. This adds to the diversity of the ecosystem. 4. What effect does a more diverse population of autotrophs in both stages of secondary succession have on the appearance of heterotrophs? A more diverse population of autotrophs increases the diversity of heterotrophs, which depend on the diversity of autotrophs present in the ecosystem. 328 Teacher Pages

7 5. What conditions exist in a climax community that support the statement a climax community is in a steady state of ecological equilibrium? A climax community is one that is mature, self-sustaining, and stable. The biotic and abiotic conditions are altered and stabilized to such levels that they support the entire community. This will continue until an outside disturbance occurs, shifting the community from the climax stage. 6. What effects would the natural disturbances you chose have on the diversity of organisms in the ecosystem if it were in the young stage of secondary succession? Answers will vary. One possible answer is a volcanic eruption, which would destroy all living organisms and the soil, taking the ecosystem back to the primary succession stage. However, if the disaster is a flood, the soil may not be completely removed and the ecosystem would not regress to the primary succession stage. 7. What are some kinds of disturbances or disasters that are caused by humans? Select one and discuss the effects it could have on the diversity of the species in the ecosystem affected by this event. Answers will vary. Key points to consider: Is the disturbance indeed caused by human actions, such as over-grazing of animals, nuclear disaster, deforestation, or growth of human populations? Did the student clearly consider the effects on the ecosystem in terms of both the biotic and abiotic factors? Teacher Pages 329

8 STAAR Biology: Assessment Activities I need to remember... Species living in an ecosystem gradually change over time, as do the physical and chemical environments within that ecosystem. takes place because organisms interact with one another in an ecosystem. In an ecosystem left undisturbed, succession follows predictable stages: primary, secondary, and climax communities. Autotrophs are the first pioneer species to inhabit an ecosystem in the primary stage; they create conditions that may be favorable to other autotrophs. Heterotrophs follow autotrophs in the stages of succession first herbivore heterotrophs, then carnivores and omnivores. An ecosystem reaches stability when it becomes a climax community. In this stage it is stable, mature, self-sustaining, and has reached an ecological equilibrium. 330 Teacher Pages

9 Interdependence within Environmental Systems Blackline Masters Contents Station Information sheet Model (2 pages) Cycle Natural Disturbance Cards Processes and Events Cards Student Pages Blackline Masters 331

10 Disease STAAR Biology: Assessment Activities Station Information: Model AUTOTROPHS Pioneer Organisms (lichens) Primary Processes and Events Diversity HETEROTROPHS Wildfires Insect Infestation Volcanic Eruption Hurricane Natural Disturbance Drought Cards AUTOTROPHS AUTOTROPHS Colonization (grasses) Colonization (shrubs) Secondary (young) Processes and Events Diversity Secondary (old) Processes and Events Diversity Pioneer Organisms (herbivores) Colonization (herbivores-carnivores) HETEROTROPHS HETEROTROPHS AUTOTROPHS Stabilization (forest) Climax Community Processes and Events Diversity Stabilization (herbivores-carnivores) HETEROTROPHS Cycle Climax Community Primary Ecological Secondary (young) pioneer species and weathering increase soil quality and quantity conditions favorable to support other plant species new species of animals appear that include those that feed on other animal species animal species first soil appear continues to build an seeds brought in by wind and competition among that species feed on a diverse mature with the addition other means of animals prominent population of plants of organic materials pioneer species compete ecosystem communities diversity among have plants reached capacity to pioneer support species replaced as with prairie-type additional plants species provide of organisms stimulus for other dominate organism with types of animals to appear other species forest replace Processes other plant species and as Events the dominant competition plant species among plant the community is self-sustaining Cardsand mature unless species a disturbance for resources occurs small shrubs and trees appear Secondary (old) 332 Blackline Masters

11 Model, Page 1 HETEROTROPHS HETEROTROPHS Pioneer Organisms (lichens) Primary Processes and Events Diversity Colonization (grasses) Secondary (young) Processes and Events Diversity Pioneer Organisms (herbivores) AUTOTROPHS AUTOTROPHS Blackline Masters 333

12 STAAR Biology: Assessment Activities HETEROTROPHS Model, Page 2 HETEROTROPHS Colonization (shrubs) Stabilization (forest) Secondary (old) Processes and Events Diversity Climax Community Processes and Events Diversity Colonization (herbivores carnivores) Stabilization (herbivores carnivores) AUTOTROPHS AUTOTROPHS 334 Blackline Masters

13 Cycle Primary Climax Community Ecological Secondary (young) Secondary (old) Natural Disturbance Cards Wildfires Drought Insect Infestation Disease Hurricane Flood Volcanic Eruption Blackline Masters 335

14 STAAR Biology: Assessment Activities Processes and Events Cards Organisms and weathering break down rock to form the foundation for soil. No heterotrophic organisms inhabit the ecosystem. Some pioneer organisms die, adding organic material to the soil. Autotrophs inhabit the ecosystem. Pioneer species and weathering increase soil quality and quantity. Conditions become favorable to support other plant species. Seeds are brought in by wind and other means. Pioneer species compete with prairie-type plants. Animal species that feed on a diverse population of plants first appear. Soil continues to build and mature with the addition of organic materials. Pioneer species are replaced as the dominant organisms by other species. Competition for resources occurs among plant species. Small shrubs and trees appear. New species of animals appear, including those that feed on other animal species. Competition among species of animals is prominent. Diversity among plants provides stimulus for other types of animals to appear. Ecosystem communities have reached their capacity to support additional species of organisms. Forests replace other plant species as the dominant plant species. The community is self-sustaining and mature unless a disturbance occurs. 336 Blackline Masters

15 Interdependence within Environmental Systems Student Pages Purpose The purpose of this activity is to reinforce your understanding of the effect that natural and human-made events and processes have on ecological succession, and how species and populations of organisms can change as a result of disturbances to an ecosystem. Before You Begin Check to see that all the items are present and organized according to the Station Information sheet. If you notice a problem, notify your teacher immediately. Materials Station Information sheet Model (2 pages) Cycle Natural Disturbance Cards Processes and Events Cards Essential Question How do the processes and events that occur within an ecosystem affect the species and populations of organisms that live in that ecosystem? Discuss the essential question with your teammate(s) and record your answer. Activities and Questions The Model illustrates a sequence of stages in an ecological succession. Review the sequence of stages from primary succession to the climax community, noting that one side includes autotrophs and the other side heterotrophs. (See the Glossary for definitions.) Student Pages 337

16 STAAR Biology: Assessment Activities Take the Processes and Events Cards out of their envelope. These cards list some processes and events that influence changes in an ecosystem that is undergoing succession. 1. Place each card in the appropriate position on the Model as shown in the example below. Continue until all cards are placed on the model. Model Pioneer Organisms (lichens) Primary AUTOTROPHS organisms and weathering break down rock to form the foundation for soil some pioneer organisms die and add organic material to the soil autotrophs inhabit the ecosystem Processes and Events Diversity HETEROTROPHS AUTOTROPHS Colonization (grasses) Secondary (young) Processes and Events Pioneer Organisms (herbivores) HETEROTROPHS Diversity 2. Why are there no heterotrophs in the primary succession stage? 338 Student Pages

17 3. How do the processes and events that occur during the primary succession stage result in the appearance of more diverse populations of autotrophs in the first stage of secondary succession? 4. What effect does a more diverse population of autotrophs in both stages of secondary succession have on the appearance of heterotrophs? 5. What conditions exist in a climax community that support the statement, a climax community is in a steady state of ecological equilibrium? Student Pages 339

18 STAAR Biology: Assessment Activities Locate the Cycle sheet and the Natural Disturbance Cards. Each card has the name of a natural disaster that can disturb the abiotic and biotic elements in an ecosystem. Select one natural disturbance card at random and place it on the Cycle sheet between the primary succession and secondary succession stages. 6. What effects would the natural disturbance you chose have on the diversity of organisms in the ecosystem if the ecosystem were in a young stage of secondary succession? 7. What are some kinds of disturbances or disasters that are caused by humans? Select one and discuss the effects it could have on the diversity of the species in the ecosystem it disturbs. 8. Now that you have completed these questions, return to the Essential Question. Would you like to modify your answer? Write any modifications below. Note: Because other students are going to do the activity after you, be sure to put all the materials at the station back as you found them. Sometimes there will be materials that need to be renewed or replaced. If you need assistance or have any questions, ask your teacher. 340 Student Pages

19 I Need to Remember... Complete this part after class discussion of this station. I need to remember... Student Pages 341

20 STAAR Biology: Assessment Activities Glossary Autotroph Autotrophs are organisms that are capable of making their own organic molecules from natural processes such as photosynthesis or chemosynthesis. Colonization Colonization is the migration of a species into a new habitat. Ecological succession is the process by which ecosystems change and develop over time. Heterotroph A heterotroph is an organism that cannot manufacture its own food and is dependent on other organisms for its nutrition. Pioneer organisms Pioneer organisms are the first species to colonize an environment; they set the stage for ecological succession, starting the chain of events that lead to an inhabitable ecosystem. Species A species is a group of organisms capable of interbreeding and producing fertile offspring. Stabilization Stabilization is the stage at which a climax community becomes established. It represents the mature, self-sustaining, final stage of succession. 342 Student Pages