Factors Affecting Ecosystems CyclesBiodiversity Human Impact

Resources  Renewable – can regenerate or be replenished by cycles  Not necessarily unlimited  Living populations, trees, water, nutrients  Nonrenewable – cannot be replenished by natural processes  Fossil fuels and natural gas

Cycles: Water and Nutrients  Organisms must have matter such as water, minerals, and other nutrients  Build macromolecules and tissues  Carry out other life functions and reactions  Elements, compounds, and other matter are recycled between organisms and their environment through biogeochemical cycles  Energy is transferred in one direction, not recycled!

The Water Cycle  Water moves between the ocean, atmosphere, and land by the following processes:  Evaporation and transpiration  Condensation  Precipitation  Can also runoff, percolate, and be stored underground as groundwater

The Carbon Cycle  Carbon  Found in organic compounds such as carbs, lipids, proteins, and nucleic acids  An important component in animal skeletons (CaCO 3 – calcium carbonate)  Also found in the atmosphere and dissolved in water bodies in the form of carbon dioxide (CO 2 )

Carbon Cycle Processes  Decrease (take out) CO 2 in air/water  Photosynthesis  Deposition/burial and formation of rock  Formation of fossil fuels  Formation of CaCO 3  Increase (release) CO 2 in air/water  Respiration  Decomposition  Erosion  Volcanic activity  Burning fossil fuels  Deforestation

The Nitrogen Cycle  Nitrogen  Major component in amino acids, proteins, and DNA  Nitrogen gas (N 2 ) – 78% of the atmosphere  Not usable by living things  Ammonia (NH 3 ), nitrates (NO 3 -) and nitrites (NO 2 -) are found in wastes, decaying organisms, and fertilizers

Nitrogen Cycle Processes 1. Nitrogen Fixation – N 2 is fixed into usable compounds by special bacteria  Found in the root nodules of legumes  Can also be fixed in the atmosphere by lightning 2. Nitrogen compounds are used by plants 3. Consumers eat the plants 4. Decomposers return nitrogen to the soil and the atmosphere 5. Denitrification – soil bacteria convert compounds back into nitrogen gas

Human Effects  Excess nitrogen from fertilizers can get into water sources and cause an algal bloom  Algae grows rapidly  Can cover the surface and block sunlight  May take in too much oxygen from the water and deplete the oxygen for other life in the ecosystem

The Phosphorus Cycle  Phosphorus  Part of DNA and RNA  Mostly remains in rock, soil, and ocean sediments  Can be released by erosion  Phosphorus Cycle  Plants absorb P from the soil and bind it to organic compounds which then move through the food web

Nutrient Limitation  Ecosystems may be limited by nutrients that are scarce or cycle slowly  Why fertilizers are used (contain N, P, and K)  May affect Primary Productivity – rate at which organic matter is made by producers  How much the producers are producing  High PP = good ecosystem!  Affects the success of populations in the ecosystem

Population Ecology  Populations are characterized by:  Population density – number of individuals per unit area  Geographic distribution – range of locations found  Growth rate – determined by looking at birth rate, death rate, immigration (movement in) and emigration (movement out)

Population Growth  Exponential – occurs when individuals grow at a constant rate  Occurs under ideal conditions with unlimited resources  “J” curve  Logistic – when growth slows or stops following a period of exponential growth  Occurs because resources are less available, birth rate or immigration decreases, death rate or emigration increases  “S” curve

Carrying Capacity  Can be seen on a logistic growth graph  Point at which the growth levels off  Average growth equals zero (BR=DR; Em=Im)  Represents the largest number of individuals the environment can support

Limiting Factors  Cause population growth to decrease  Density-dependent factors – depend on population size  Affect larger, more dense populations more  Competition, predation, parasitism, and disease  Density-independent factors – affect all population sizes in the same way  Unusual weather, natural disasters, seasonal cycles, and human activities (damming rivers, deforestation, etc.)

Biodiversity  The total of variety of all habitats, organisms, and genes in the biosphere  One of the greatest natural resources  Provides us with  Food  Industrial products  Medicines  Other usable resources

Threats to Biodiversity  Often caused by humans:  Habitat destruction or fragmentation (splitting habitats into pieces)  Overuse of animals or parts  Pollution  Introduction of new species  Can become invasive species – reproduce rapidly and affect other populations  Can all lead to endangerment or extinction

Biomes  Major ecological community that includes ecosystems with similar climates and organisms  Examples: desert, tropical rainforest, tundra, savanna, etc.  Organisms within the biome have adaptations or traits that help them survive in those conditions

Climate  Average year-after-year conditions  Includes temperature and precipitation  Determines which organisms can survive in a particular area

Climate Affected By:  Greenhouse effect – trapping of gases (CO 2, water vapor, methane) by the atmosphere that helps hold in heat from the sun  Latitude – position north or south of the equator  Creates climate zones: polar, temperate, and tropical  Typically cooler the farther from the equator  Heat transport by wind and ocean currents

Other factors  Ozone layer – layer of O 3 that protects us from UV radiation  Ozone depletion – CFC’s were reacting with ozone and creating holes in the ozone layer  Still feeling affects today  Global warming – increase in the average temperature of the biosphere  Possibly due to increased CO 2 emissions  Effects may include rise in sea levels, flooding, change in climate and weather, etc

Don’t Forget…  Reduce  Reuse  Recycle