Click on the links below to access textbook chapter summaries, and PowerPoint outlines and images from the textbook.
Chapter 9 Summary Chapter 9 Outline Chapter 9 Images |
Biogeochemical cycles are covered in chapter 3-5 in the textbook, and succession is covered in chapter 5-4. Chapter summaries, outlines, and images for these chapters can be found on the Ecosystems & Ecology page.
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PowerPoint lecture on biogeochemical cycles and project guidelines
Biogeochemical Cycles
Essential APES!
Questions on the NITROGEN CYCLE have appeared on more APES exams than any other of the nutrient cycles.
Nitrogen fixation is the conversion of atmospheric N2 into compounds usable by organisms (ammonia NH3 & nitrate N03-). This requires energy to break the N bonds.
Biogeochemical Cycles
Essential APES!
Questions on the NITROGEN CYCLE have appeared on more APES exams than any other of the nutrient cycles.
Nitrogen fixation is the conversion of atmospheric N2 into compounds usable by organisms (ammonia NH3 & nitrate N03-). This requires energy to break the N bonds.
Abiotic fixation (~10%) occurs through lightening in the atmosphere, producing N oxides which are carried to earth in rain as nitric acid
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Biotic fixation occurs when specialized bacteria in soil & blue-green algae in aquatic environments combine N2 gas with H to make ammonia, which is then excreted. Some is then converted to ammonium ions (NH4+) that can be used by plants.
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Nitrification is the process by which ammonia is oxidized to nitrite ions (N03-), also with the help of bacteria, which is easily taken up by the roots of plants to form proteins, nucleic acids, & amino acids. This form of nitrogen is then passed on to consumers.
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Ammonification is the result of decomposers breaking down organic matter & waste and convert it to ammonia. Decomposition rates affect the level of nutrients available to producers.
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Denitrification is the process by which nitrates are reduced to the gas N2 and returned to the atmosphere. This is performed by bacteria in wet soil of sediments at the bottom of aquatic environments.
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ESSENTIAL APES!
Succession is the natural change in the types of species that live in a certain area, and the gradual replacement of one plant community by another through natural process over time.
Primary Succession - begins in a place that has no soil, such as sides of volcanoes, landslides, following glaciation, or other processes that remove sediment down to bedrock.
Secondary Succession - begins in a place that already has soil, and once had living organisms.
Climax Community - Stable groups of plants and animals that are the end result of succession processes. Climax communities are not necessarily made up of big trees. It could be grass in the prairies or cacti in the deserts.
Succession is the natural change in the types of species that live in a certain area, and the gradual replacement of one plant community by another through natural process over time.
Primary Succession - begins in a place that has no soil, such as sides of volcanoes, landslides, following glaciation, or other processes that remove sediment down to bedrock.
- Generally begins with lichens that do not need soil to survive. (pioneer species).
- When lichens, weather, and erosion break down rocks, soil begins to form.
- Lichens decompose and add organic matter to the rocks to make soil.
- Plants such as moss and fern grow in the soil
- These plants die, which add more organic material to the soil.
Secondary Succession - begins in a place that already has soil, and once had living organisms.
- Occurs faster than primary succession, and has different pioneer species (grasses & herbs).
- Can occur after large or small disturbances.
Climax Community - Stable groups of plants and animals that are the end result of succession processes. Climax communities are not necessarily made up of big trees. It could be grass in the prairies or cacti in the deserts.
Succession is influenced by biotic factors:
• Competition • Predation • Herbivory • Disease • Parasitism • Seed dispersal • Nitrogen fixation • Reproductive strategy • Human impact |
and by abiotic factors:
• Climate • Rainfall • Light • Wind • Temperature • Soil composition • Fire • Drought • Altitude • Geographic location |
Essential APES!
CHARACTERISTICS & BENEFITS OF ECOSYSTEMS WITH HIGH BIODIVERSITY
- Large numbers of species - Large numbers of individuals
- Complex food webs - High genetic diversity
- Great variety of niches/roles - Abundant resources
- Resistant to invasive & pest species
- Abundant decomposers = high nutrient recycling
- Provide numerous ecological services (sources of food, medicines, water & air filtration, pollinators, carbon storage)
Examples: coral reefs & tropical rainforests
CHARACTERISTICS & BENEFITS OF ECOSYSTEMS WITH HIGH BIODIVERSITY
- Large numbers of species - Large numbers of individuals
- Complex food webs - High genetic diversity
- Great variety of niches/roles - Abundant resources
- Resistant to invasive & pest species
- Abundant decomposers = high nutrient recycling
- Provide numerous ecological services (sources of food, medicines, water & air filtration, pollinators, carbon storage)
Examples: coral reefs & tropical rainforests
FACTORS THAT COULD LEAD TO REDUCED BIODIVERSITY
Natural:
- Particulates in atmosphere from volcanoes or asteroids
- Wildfires
- Climate change
- Extreme weather events
- Drought
- Mutation/evolution leading to new diseases, predators
Anthropogenic:
- Deforestation/land clearing
- Agriculture (monoculture, pesticides, GMOs
- Overexploitation (over hunting/fishing, bushmeat trade)
- Water contamination (excess fertilizers, feedlot runoff, construction/road runoff, untreated sewage)
- Burning fossil fuels
- Introduction of invasive species
- Dams, hydroelectric, wind farms, surface mining
Natural:
- Particulates in atmosphere from volcanoes or asteroids
- Wildfires
- Climate change
- Extreme weather events
- Drought
- Mutation/evolution leading to new diseases, predators
Anthropogenic:
- Deforestation/land clearing
- Agriculture (monoculture, pesticides, GMOs
- Overexploitation (over hunting/fishing, bushmeat trade)
- Water contamination (excess fertilizers, feedlot runoff, construction/road runoff, untreated sewage)
- Burning fossil fuels
- Introduction of invasive species
- Dams, hydroelectric, wind farms, surface mining
Results:
- Habitat loss/fragmentation
- Loss of species
- Sea level rise
- Sedimentation, eutrophication
- Decrease in nutrients/oxygen
- Loss of genetic variation
- Loss of natural capital
- Habitat loss/fragmentation
- Loss of species
- Sea level rise
- Sedimentation, eutrophication
- Decrease in nutrients/oxygen
- Loss of genetic variation
- Loss of natural capital