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Ecosystems: Structure & Function

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  1. Ecosystems:Structure & Function Biology 391 Ch. 24

  2. What is going on in this picture? Can you explain all of the arrows? What do you think each represents? • How does this define ecology? • Hints: Nutrients, energy, biomass, abiotic, biotic

  3. 24.1 Abiotic Factors • Examples? • Abiotic affects biotic • Distribution, adaptations, etc. • Trade-off  adaptation to live in one envi. Usually means exclusion for another • Biotic can affect abiotic • EX: Soil development by lichens

  4. All life on Earth is interconnected. All life interacts with the nonliving environment.

  5. ECOSYSTEMS • ABIOTIC • Includes: Water, air, temperature, soil, light levels, precipitation, salinity, pH • Sets tolerance limits for populations and communities • Some are limiting factors that structure the abundance of populations • BIOTIC – trophic structure 1. Producers, consumers, decomposers in a food chain, web and pyramid 2. Interactions lead to transfer of energy and biomass


  6. ENERGY SUN Autotrophs Heterotrophs (producers) (consumers) • Autotrophs- plants, algae, phytoplankton • Heterotrophs- • Herbivores- eat plants • Carnivores- eat meat • Omnivores- eat meat or plants • Scavengers- eat dead material • Decomposers- final breakdown of dead material- returning nutrients to soil/water

  7. Energy Pyramid • Shows transfer of energy through trophic levels (who eats what) Producers primary consumers secondary consumers tertiary consumers, etc. • 10% Rule • Only 10% of the energy in the previous trophic level is passed on • Biomass • Total quantity of living matter at each trophic level

  8. Where does the 90% go? What law is this?

  9. Relationships in Ecosystems • What is a niche? • Predation • Predator/prey • Competition • **Competitive Exclusion Principle • Symbiosis • Mutualism • Parasitism • Commensalism

  10. Ecosystem Dynamics – nutrient cycles

  11. Nitrogen Cycle What gases compose air? Nitrogen is NOT usable by plants & animals Must change molecular forms (nitrogen fixation) Ammonia & nitrate preferred by plants Decay & denitrification return N2 to air

  12. Limiting Factors • Abiotic factors that limit the population • Examples?

  13. Population Dynamics • Carrying capacity • Exponential growth vs. Logistic growth • Boom-bust cycle • Predator-prey cycle

  14. http://desip.igc.org/mapanim.html http://www.poodwaddle.com/clocks2.htm

  15. Recap • Can an herbivore be a secondary consumer? Secondary trophic level? Why/why not? • How many trophic levels typically exist in a food web? Explain. • Why could the Earth support more people if we all ate at lower trophic levels? • List 3 abiotic factors and describe how each can act as a limiting factor. • What is the relationship between K and limiting factors?

  16. Chapter 25 • Biomes • Types of ecosystems usually defined by the most conspicuous vegetation • Tropical rain forest • Savanna • Deserts • Temperate grasslands • Temperate deciduous forests • Taiga • Tundra

  17. Aquatic Biome • Vertical zones • Photic zone • Aphotic zone • Benthic and abyssal zones can be within here • Horizontal zones • Intertidal zone • Neritic zone • Oceanic zone