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Chapter 15 & 16 notes

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popluations and ecosystems

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Chapter 15 & 16 notes

  1. 1. CHAPTER 15 & 16 NOTES “ POPULATIONS & ECOSYSTEMS”
  2. 2. I. HOW POPULATIONS GROW
  3. 3. A. Population – consists of all the individuals of a species that live together in one place at one time.
  4. 4. B. Survival of a population determined by 3 features: <ul><li>1. population size - # of individuals in a population. Very small populations most likely to become extinct. </li></ul><ul><li>2. population density - # of individuals that live in a given area. </li></ul><ul><li>3. dispersion – way the individuals of a population are arranged in space. </li></ul>
  5. 5. <ul><li>Population growth – limited by predators , disease , and the availability of resources. </li></ul><ul><li>1. carrying capacity – population size that an environment can support. </li></ul><ul><li>2. density dependent factors – limited resources such as food, water </li></ul><ul><li>3. density independent factors – environmental conditions; weather, climate </li></ul>
  6. 6. II. HOW POPULATIONS EVOLVE
  7. 7. <ul><li>A. Hardy-Weinberg Principle – the frequencies of alleles in a population do not change unless evolutionary forces act on the population. </li></ul><ul><li>1. mutation </li></ul><ul><li>2. gene flow </li></ul><ul><li>3. nonrandom mating </li></ul><ul><li>4. genetic drift </li></ul><ul><li>5. natural selection – such as the mice populations – run-speed </li></ul>
  8. 8. III. CHARACTERISTICS OF ECOSYSTEMS
  9. 9. <ul><li>Ecology – the study of the interactions between organisms and their environment. </li></ul><ul><li>Habitat – the place where a particular population of a species lives. </li></ul><ul><ul><li>Abiotic – physical factors of a habitat. </li></ul></ul><ul><ul><ul><li>Ex: soil, water, weather </li></ul></ul></ul><ul><ul><li>Biotic – living factors in a habitat. </li></ul></ul><ul><ul><li>Ex: plants, animals, bacteria, fungi </li></ul></ul><ul><li>Community – many different species that live together in a habitat. </li></ul><ul><li>Ecosystem – consists of a community and all of the physical factors of its habitat. </li></ul>
  10. 10. Community/Ecosystem
  11. 11. IV. CHANGES OF ECOSYSTEMS OVER TIME
  12. 12. <ul><li>Examples of new habitats and ecosystem development include: volcano forming a new island , glacier recedes and exposes bare rock , a fire burning all of the vegetation in an area. </li></ul><ul><li>B. Pioneer specie s – first organisms to live in a new habitat. </li></ul><ul><li>C. Succession – a somewhat regular progression of species replacement </li></ul><ul><ul><li>Primary succession – occurs where plants have not grown before. </li></ul></ul><ul><ul><li>Ex: Glacier Bay, Alaska </li></ul></ul><ul><ul><li>2. Secondary succession – occurs in areas where there has been previous growth. </li></ul></ul>
  13. 13. Examples of Succession
  14. 14. V. ENERGY FLOW IN AN ECOSYSTEM
  15. 15. <ul><li>Trophic level – the different energy levels in a food chain or pyramid. </li></ul><ul><li>Food chain – the path of energy through the trophic levels of an ecosystem. </li></ul>
  16. 16. <ul><li>1. First level – producers – green plants and algae </li></ul><ul><li>2. Second level– primary consumers (herbivores) </li></ul><ul><li>3. Third level – secondary consumers eat the herbivores (carnivores,omnivores) </li></ul><ul><li>4. Fourth level – tertiary consumers – (carnivores that consume carnivores) </li></ul><ul><li>5. At every level decomposers are found that break down the dead remains of all organisms. Ex: bacteria, fungi </li></ul>
  17. 17. <ul><li>C. Food web – a complicated, interconnected group of food chains. </li></ul>
  18. 18. <ul><li>D. The amount of energy available decreases as it passes from 1 trophic level to the next. Only about 10% of the energy from one level is passed on to the next level. </li></ul>
  19. 19. VI. BIOGEOCHEMICAL CYCLES
  20. 20. <ul><li>Cycles which pass nutrients from the nonliving environment to the living environment and back. </li></ul><ul><li>1. Water cycle – includes precipitation, evaporation, transpiration </li></ul><ul><li>2. Carbon cycle- includes respiration, combustion, and erosion . </li></ul><ul><li>3. Nitrogen cycle- 79 % of the atmosphere is nitrogen. Bacteria fix atmospheric nitrogen to make ammonia. </li></ul>

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