Enviro Exam 2 Review PDF

Biodiversity → the variety of life on Earth (genes, organisms, ecosystems, functions) → Tropical Rainforests have high biodiversity - biodiversity is highest near the equator and attenuates towards the poles What supports/explains the high biodiversity in tropical rainforests? - complexity of...

Biodiversity → the variety of life on Earth (genes, organisms, ecosystems, functions) → Tropical Rainforests have high biodiversity - biodiversity is highest near the equator and attenuates towards the poles What supports/explains the high biodiversity in tropical rainforests? - complexity of the plant architecture (“niche diversity”) - abundant solar energy - warm/wet climate Features creating niche diversity: - Woody vines (lianas) are wrapped around the trees - epiphytes (bromeliads) - live on trunks and branches - trunks are buttressed - Floor contains tree seedlings, herbaceous plants, ferns - floor thickly laced with roots - roots are shallowly layered in the upper 1/3 m of soil - soil is low in nutrients because the nutrients are reabsorbed almost immediately by the mychorrhizae North American biodiversity examples: Everglades Appalachian Mountains Pacific Northwest Our very own Black Rock Forest → Biodiversity hotspot: area with exceptional concentrations of endemic species and is undergoing exceptional loss of habitat - These 25 hotspots comprise only 1.4% of the Earth’s land area, yet they are home to 44% of the world’s plant species. → How do you measure biodiversity? 2 elements: richness and evenness - Species richness: Which species are present? - Species evenness: What are their relative abundances? *A diverse community = high numbers and high evenness → Diversity Mathematically: - Shannon Wiener Index: Example: - Same species richness, but B has higher species evenness - Prediction: B will have higher biodiversity (On an excel spreadsheet) Columns show: Number of individuals per species, proportion of total number of individ., natural log of proportion, (p) x (|ln p|). End number shows biodiversity Why care about biodiversity? - The members of a biological community work together to create a functioning system that provides services for the planet. - These services are called ecosystem services and are defined as: benefits supplied to human societies by natural ecosystems: generally essential goods and life support processes. - These services are valuable. The general public is unaware. - The economic value for the 17 ecosystem services from 16 biomes is $33 trillion per year (at least). (From Costanza et al. (1997) Nature 387.) In 2014 this was updated to $125-145 trillion per year. What processes are happening in ecosystems that provide the mechanism for many of the services? Productivity: production of plant material during PS as measured in grams of carbon per m2 Decomposition: breaking down organisms to molecules that get recycled Nutrient cycling: passing of nutrients between biosphere, atmosphere and lithosphere What are some of these ecosystem services? Purification of air and water Regulation of atmospheric composition* Regulation of climate* Regulation of hydrological cycle* Pollination of crops Seed dispersal (FORESTS AND OCEANS DO MOST OF THIS* VIA PHOTOSYNTHESIS AND RESPIRATION AND EVAPOTRANSPIRATION) → Evapotranspiration: Evaporation + Transpiration. - Loss of water from the soil both by evaporation from the soil surface and by transpiration from the leaves of the plants growing on it. Goods: - Medicines - Lumber - Food - Recreation - Aesthetics - Water Supply *Some examples of medicines discovered in plants: Digoxin, Paclitaxel, Atropine, Quinine, Codeine, Acetyl Salicylic Acid, Morphine, Warfarin, Vincristine → New York City Drinking Water....how does nature keep water clean? The drinking water reservoir is surrounded by a forest watershed - The roots of trees and soil microbes in the forest cleanses the water - Pollutants are held or filtered by soil, others are taken up or transformed by plants/microbes. And still others are first held by soil and then taken up by vegetation or degraded by bacteria. Birds keep NY drinking water safe and protect the trees - Caterpillars eat the leaves off of the tree, trees could die and water would not get cleaned - Migratory birds arrive at the same time the caterpillar appear, they eat the caterpillars and save the trees *Birds are declining, invest in conservation of birds Other threats to NY drinking water - Deforestation in watershed/expansion of impervious surfaces - Fertilizer and pesticide use in the watershed (agricultural use + runoff) - Mismanages/outdated sewage treatment Threats to Biodiversity - Habitat destruction - Introduction of exotics - Pollution (includes climate change) - Population (over pop) - Over consumption → Habitat loss, fragmentation are major threats *Isolated habitat = island, surrounded by water or agricultural fields Theory of Island Biography: small islands have less species than larger ones Characteristics of small island habitats: - Few partners to breed with - Disasters have more impact and severe effects on smaller populations - Distances from other islands (small or large) determines rate that new species may immigrate - Increased Habitat edge *edge features: - sunlight and air circulation - forest edges heat up each day, the air over those regions rises, drawing cool moist air out of the forest - hot dry air takes a toll on large hardwood trees such as mahogany and ebony in the tropics - open fields also expose the forest to wind, which blows down trees and further opens up the canopy - over time, these gaps are filled with fast-growing trees and vines a shift to generalist species with loss of specialist species Example study: Near-Complete Extinction of Native Small Mammal Fauna 25 Years After Forest Fragmentation Gibson et al. Science 341:1508 → How quickly can species disappear from forest fragments? - Event: Forest islands were created after a mountainous area was flooded to form a reservoir in Thailand. They observed near total loss of small mammals in: 5 years from fragments