Midterm Exam 4 Flashcards
(37 cards)
Species-Area Hypothesis
Larger areas lead to more species because they can support more individuals and have a larger habitat range
For: Insect diversity in relation to tree range
Against: There are not more species in the desert/tundra as they are large but hostile environments
Autotrophs
Fix CO2 into biomass with sunlight (photoautotrophs) or by oxidizing inorganic compounds (chemoautotrophs)
Species Richness
The number of species in a community, varying according to geographic range (increase from polar to tropical, increase by topographical variation, and decrease by “peninsular effect”)
Ecosystem Function and Biodiversity Hypotheses
Diverse-Stability Hypothesis: Increase species richness leads to increase in ecosystem stability
Redundancy (Rivet) Hypothesis: Most species are redundant (take up space and don’t add diversity)
Keystone Hypothesis: Ecosystem function plummets as soon as biodiversity declines from natural levels
Idiosyncratic Hypothesis: Ecosystems change unpredictably as number of species changes
Elton’s Diversity-Stability Hypothesis
Claims that disturbances in a species-rich community would be cushioned by large #’s of interacting species
Tilman Cedar Creek Investigation
Found that highest % change in vegetation cover (increased productivity) occurred in most species-rich plot
Species-Productivity Hypothesis
Greater production of plants leads to greater richness via evapotranspiration rates
For: Plants grow optimally in warmer, wet environments, tree species richness can be predicted using the evapotranspiration rate
Against: Some tropical waters have low productivity and high richness while the Antarctic Ocean has high productivity and low richness
Heterotrophs
Includes organisms that eat others (primary and secondary consumers), as well as decomposers (detritivores)
Carbon Cycle
The carbon cycle is composed of factors such as decomposition, respiration, and photosynthesis, which are all biotic. Some abiotic factors also play a role, such as carbon sequestration in terrestrial environments, and carbon sedimentation in aquatic, which both remove carbon from the cycle. Fluxes can occur via natural processes such as volcanic eruptions adding more atmospheric carbon, or humans burning fossil fuels
Primary vs. Secondary Succession
Primary Succession: Founder species colonize barren, previously unihabitated space (e.g., following glacial retreat)
Secondary Succession: Recolonization of a former ecosystem following a natural disaster (e.g., forest fire)
Leading hypotheses explaining large-scale patterns of species richness
- Species-Time Hypothesis
- Species-Area Hypothesis
- Species-Productivity Hypothesis
Island Biogeography
Equilibrium model posited by MacArthur and Wilson. # of species tend toward an equilibrium determined by a balance of immigration and extinction.
Assumes: An increase in # species with an increase in island size, # of species decreases with increased distance from mainland (source pool), and turnover of species should be considerable even with equilibrium present
Limits of Primary Production in Aquatic Ecosystems
Light and Nutrients
Reasons to Support Conservation Biology
Benefits: Conserving biodiversity has tremendously far-reaching benefits and impacts, one such being a great economic benefit through the services provided by the ecosystem, such as naturally cleaning air, tourist destinations
Services: Services provided by the ecosystem, like pollination, clean lakes and streams, and atmospheric gas supply have an incalculable value
Ethics: We as humans have the responsibility to serve as protectors for the world and environment we occupy
Biogeochemical Cycling
The movement of chemicals through an ecosystem
Levels to Examine Biodiversity
- Genetic, amount of genetic variation existing withing and between species (helps respond to environmental conditions)
- Species, # and relative abundance of species in a community (threatened species can become endangered, then in danger of extinction)
- Ecosystem, diversity of structure and function within an ecosystem
Conservation biology aims to protect diversity at all levels
Habitat Conservation Focuses
Megadiversity Countries: Suggests efforts should focus on most biologically rich countries, not necessarily the most unique (utilitarian approach targeting to 17 countries home to ~70% of all known species (e.g., Brazil, Indonesia))
Endemic Species: Focus on hot spots, which are biologically diverse and under the most threat of destruction. Must contain at least 1500 vascular plants as endemic species and lost 70% of original habitat, argument against is that tropical rainforests would receive most attention
Representative Habitat: All major habitats should have conserved representatives (many areas threatened that are not biologically rich can be preserved, also crisis ecoregions with 10% protected)
Island Biogeography/SLOSS Debate: Wildlife reserves and sanctuaries are islands (increase in area equals increase in species protected). Single Large or Several Small (SLOSS) debate focuses on the benefits of protecting one large site to hold a larger population, or several smaller which can contain more variety and reduce threat of disasters
Single Species Conservation Approaches
- Umbrella Species: Protecting them also protects many other species (e.g., Norther Spotted Owl, requires 800 hectares of forest)
- Flagship Species: A single large, instantly recognizable species (e.g., Buffalo, Panda, or Eagle)
- Keystone Species: Plays a special role in the community, not necessarily dominant (e.g., Beaver)
Evapotranspiration
The process through which water is evaporated from the soil, and leaves of plants as they transpire
Can predict the aboveground primary production
Restoration Ecology
Attempts to rehabilitate degraded ecosystems and populations, occurring via complete restoration (put back exactly the same), rehabilitation (return the habitat to something similar to full restoration), or ecosystem replacement (replaces original ecosystem with a different one following a disturbance)
Reintroductions and Captive Breeding
Suppports propogation of plants and animals outside of their natural habitat to produce stock for subsequent release into the wild (e.g., Peregrine Falcon, California Condor, Yellowstone Wolves)
Human Alterations to Biogeochemical Cycles
By burning enormous amounts of fossil fuels, humans are adding a tremendous amount of excess carbon dioxide into the atmosphere, contributing to the greenhouse effect, and causing climate change to occur.
By adding nitrogen-rich fertilizer to crops and lawns, humans are causing the rapid and unregulated growth of plant matter not only in the target plants, but also in nearby bodies of water, leading to eutrophication events and subsequent mass die-offs which effectively poison the water to aquatic species.
By removing massive amounts of water from rivers to sustain human populations, and through the decreased confidence in rainfall patterns and increased severity of the precipitation that does occur, humans have severely altered the water cycle.
Nitrogen Cycle
The nitrogen cycle is mainly dominated by plants and bacteria, which are responsible for fixing the nitrogen in the soil so it can be used by plants. Fluxes in the pool of this critical limiting resource in ecosystems can be attributed to nitrogen-rich fertilizer used by humans in agriculture, the runoff of which can leak into nearby lakes and rivers, causing eutrophication and destabilizing the ecosystem
Phosphorous Cycle
Phosphorous cycles through the environment by erosion of rock and volcanic eruptions, does not have a gaseous phase
