Download Unit 2 ecosystem study sheet

Unit 2: Ecosystems
Feedback loops: All systems on Earth are linked
Feedback loop = A system structure that causes output from one node to eventually influence input to that node
 Negative feedback loop = output from a system moving in one direction acts as input
 Stabilizes the system, ie. predator – prey interactions
 Positive feedback loop = instead of stabilizing a system, it drives it further toward one extreme or another
o Exponential growth in human population, erosion, melting sea ice
o Rare in nature, but common in natural systems altered by humans
Major components of Ecosystems
Abiotic: nonliving components (water, air, nutrients, solar energy)
 Zone of tolerance: min. & max range of environmental factors that organism can survive in (optimal range can be small)
o Most organisms are least tolerant during juvenile or reproductive stages
 Limiting factor:single factor that can limit or prevent growth of a population (too much or too little)
o Examples: nutrients, space, mate competition, net primary productivity
Biotic: living components (plants, animals, microbes)
Biodiversity: different life forms
Ecosystem = all organisms and nonliving objects that occur and interact in a particular area at the same time
o It includes abiotic and biotic components
 Ecotones = transitional zones between two ecosystems. Elements of each ecosystem mix
 Patches = form the landscape. Example: forested patches within an agricultural landscape
o Widely spaced patches endanger organisms
NPP
Ecosystem Productivity: The amount of photosynthesis that takes place is one indicator of an ecosystem’s productivity
Primary productivity: amount of biomass produced by photosynthetic organisms
 How much solar energy is converted into chemical energy through photosynthesis
Net Primary Productivity (NPP): the left-over remains of biomass available to use as food for other consumers after the producer has
used some for their own respiration
 A measure of the rate at which an ecosystem incorporates carbon from the atmosphere into biomass in a given length of time
(day, week, month, etc.
Secondary productivity: amount of biomass produced by organisms that eat photosynthetic organisms
Most productive ecosystems
1. algal beds and reefs
2. tropical rain forests
3. swamps and marshes
Least productive ecosystems
1. desert
2. open ocean
3. tundra
Loss of Biodiversity
21% of mammals, 12% of birds & 30% of amphibian species are threatened with extinction
In the past 500 years (in the US) 237 animal species & 30 plant species have become extinct
 Extirpation: the disappearance of a population from a given area, but not the entire species globally
Habitat loss
 Disturbed or degraded 40-50% of earth’s land surface
o 95-98% of all virgin forests in US have been destroyed since 1620
 Fragmentation: gradual destruction of a habitat
Causes of habitat loss
 Overuse - poaching
 Climate Change
 pollution; introduced species;
Nonnative (exotic) species (Biological Pollution)
 49% of all US endangered species are caused by nonnative species
 many introduced species have no natural predators, competitors, or pathogens to control numbers
ex. Kudzu vine(SE US for erosion control), Brown Tree Snake (kills birds in Guam)
Zebra mussels (from E. Europe threaten native mussels in Great Lakes)
Gypsy moth (eat American forests), Brazilian pepper (in Everglades)
Rosy tree snail (introduced in Hawaii to kill the giant African tree snail)
Feral & outdoor pet cats—kill 568 million birds annually
Endangered and extinct species
Endangered Species: any organism (plant or animal) whose population has dropped drastically
 Major causes (human): poaching, habitat destruction, climate change
Extinction
Endangered species: has so few individual survivors that the species could soon be extinct
Threatened species: still abundant, but declining in #’s & is likely to become endangered
Background Extinction (Natural rate of extinction)
 natural, low level of species extinction each year, 3-14/ yr. based on fossil record
 estimate 99% of all species that have ever existed are now extinct
Mass extinction
 catastrophic, widespread event kills many existing species
 Earth has experienced five mass extinctions (20-60 million years apart)
o some biologists believe we are experiencing the sixth mass extinction
o rise today in extinction rates above background level = 3-200 species/day
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Characteristics that make a species more vulnerable to biological extinction
 Low reproductive rate ex. blue whales, giant pandas
 Not adaptive to environmental changesex. giant pandas, Everglades kite
 Not many mates ex. many island species
 Feeds at high trophic level (less diversity of food) ex. Bengal tiger, bald eagle, grizzly bear
 Fixed migratory patterns (development interferes – dams, windmills, powerlines) ex. whooping crane, sea turtles
 Rare (not many to begin with) ex. many island species, some orchids
 Commercially valuable (poachers more likely to kill them) ex. tiger, elephants, rhinoceros
 Large territories (hard to find a mate, habitat fragmentation) ex. California condor, Florida panther
Causes of Species Extinction
Habitat Loss (#1 cause)
tropical deforestation is greatest eliminator of species followed by:
destruction of coral reefs & wetlands c. plowing of grasslands
pollution of freshwater & marine habitats
Greatest threats in US are:
Agriculture, Commercial development, hydroelectric development, Outdoor recreation (off-road vehicles), Livestock grazing,
Pollution
Commercial hunting & poaching
 trade in wild plants & animals generates $10-20 billion annually
o Gorilla ($150,000), elephant & rhino ivory ($?), Amazon macaw ($20,000)
 for every live animal sold as a pet in US, 50 other animals were killed
 sale of bushmeat (gorilla meat) by local people
 Over-harvesting of commercial fisheries
Predators & Pest Control
 extinction of Carolina parakeet by US fruit farmers
 prairie dog holes break cattle’s legs
 African farmers kill elephants that trample their food crops
Loss of Genetic Diversity
 limits ability to survive by limiting phenotype outcome possibilities, less chance of having right combination if
environment changes
 Inbreeding allows recessive genes to accumulate
Maintenance through conservation
Strategies
Conservation Biology:studies the factors behind the loss, protection, and restoration of biodiversity
 Captive breeding
 Cloning (not helpful large scale)
 Forensics (increase genetic diversity)
 Umbrella/flagship species (protects other species)
 Protect biodiversity hotspots
 Debt for nature swaps
 Restoration Ecology
o Combine with local community-based conservation
Species Approach
 involves identifying which species are at greatest risk of becoming extinct, gaining understanding of the species, & legally
protect them & their habitats
o problem = we protect only “cute animals”
 propagate endangered species in captivity
 reintroduce species into sustainable habitats
Ecosystem Approach (National Parks, etc.) more effective than species approach
 focuses on ensuring that enough land and aquatic areas are protected to provide habitat for the majority of terrestrial
and aquatic wild species
 eliminate or reduce populations of alien species from protected areas
 restore degraded ecosystems
 saves multiple species
o Problems: mostly scenic areas protected, poor countries don’t enforce
Reasons for preservation
 Intrinsic value & preserving genetic diversity
 Economic goods (species provide food, fuel, lumber, medicines, etc.)
 Ecosystem services (photosynthesis, pollination of crops, soil formation, nutrient cycling, pest control, climate regulation,
flood control, waste decomposition, etc.)
 Recreation—ecotourism (generates $500 billion worldwide)
o Ex. Male lion in Kenya generates $515,000 in tourist dollars but only $1000 if killed for its skin.
Relevant laws and treaties
International treaties
International Union for Conservation of Nature (IUNC) Red List
 list of species at high risk of extinction
Convention on International Trade in Endangered Species (CITES)-1975
 lists more than 800 species that cannot be traded
 lists 29,000 species whose international trade is monitored & regulated
 limited effectiveness (difficult to enforce, convicted violators pay small fines, member countries can exempt themselves,
much illegal trade occurs in countries that have not signed the treaty-152 have signed)
National Laws
Lacey Act (1900)-prohibits transport of live or dead wild animals across state lines without federal permit
Endangered Species Act (1973)-makes it illegal for Americans to import or trade any product made from an endangered species
 forbids federal agencies & private land owners to carry out, fund, or authorize development that would jeopardize
endangered species
 Fish & Wildlife service must design a recovery plan for all endangered
Zoos & Game parks
Egg pulling-collect wild eggs of endangered species & hatch them in zoos or research centers
Captive breeding-wild animals are captured and bred in captivity, or artificially inseminated, then reintroduce the offspring into the
wild (ex. Peregrine falcon & black-footed ferret)
Seed Banks – stores seeds of plants as a reference for the future
Wildlife Management
 manipulating wildlife populations and their habitats for their welfare & for human benefit
 uses laws to regulate hunting & fishing
 plant vegetation that is preferred food for wild species
 sport hunting is allowed only during certain seasons and is limited to size, number, and sex of animals killed
 major flyways for migratory waterfowl are managed by international treaties