Part II Flashcards
why is it difficult to estimate current rate of extinction?
- difficult to say w/ certainty that a species is extinct
- most species unknown to scientists, therefore extinct species also unknown
cycles that generate climate changes short term
- earth revolves on its axis leading to alternating cooling and warming w/ solar radiation
- earth orbits sun, tilted axis generates annual climactic cycles b/w northern hemisphere tilted toward sun during half of the orbit, southern hemisphere tilted toward sun other half
- LEADS TO
- diurnal-nocturnal behaviour of animals
- seasonal growth and death of annual plants
cycles that generate climate changes long term
- variaration of tilt of earth’s axis
- variation of shape of earth’s orbit around sun
- procession of equinoxes: distance form earth to sun cna either accentuate or ameliorite effects of axial tilt on weather
3 concerning observations re:global warming
- greenhouse gases lead greenhouse effect
- increased concentration of gg lead to increase greenhouse effect
- mean global temperature has increased
greenhouse gases
water vapor, carbon dioxide, methane, etc.
greenhouse effect
gg allow solar radiation to penetrate atmosphere and warm earth’s surface and inhibit reradiation of energy back to space
causes of global warming
- increased consumption of fossil fuels
- devasation of ecosystems (release gg)
- astronomical factors, increased photosynthesis (unpopular)
will organisms be able to adapt to future climate change?
- have been able to adapt well in past but maybe not in future
- current pops. already stressed by habitat degradation and overexploitation
- stressed pops. are small and therefore have lower chance to produce offspring
- human alteration of landscapes has reduced quantity of suitable habitats and fragmented landscapes by roads, etc. decreasing odds of individuals arriving in new suitable habitat
- possible temps will rise to unprecedented levels
- melting ice caps reduce shoreline
- unprecedented rate of increase in temp
why are rare species more vulnerable to extinction than common species?
- greater chance of pushed to extinction by environmental change
- environmental event may encompass species’ entire range
- demographic problems
- unbalanced sex ratio can limit birth rate
- more likely to happen to small pops.
- genetic problems
- inbreeding
- genetic drift
- bottlenecks
- restricted ability to adapt
why are some species particularly sensitive to human-induced threats?
- limited adaptability and resilience
- may be due to low reproductive capacity, limited dispersal capabilities, inflexible habitat requirements, etc.
- human attention
- may be edible, extremely unpopular (e.g. bats)
- ecological overlap
- tied to human-preferred ecosystems (e.g. w/ fertile soil and benign climates)
- large home-range requirements
- cannot fit in among humans
population
groups of individuals of some species occupying a defined area at same time
meta populations
group of diff. patch pops.
turnover
subpopulations appearing and disappearing due to colonization and local extinction
population visibility analysis (PVA)
any systematic attempt to understand processes that make pop. vulnerable to extinction, technique used to measure minimum viable population
4 interacting factors that might contribute to pop’s extinction
- demographic stochasticity
- =uncertainty resulting from random variation in reproductive success and survivorship at individual level
- environmental stochasiticity
- =random variations in components of habitat quality
- e.g. climate, nutrients, water
- catastrophes
- =dramatic events that occur at random intervals
- e.g. droughts, hurricanes
- genetic stochasticity
- random variation in gene frequencies of a pop. resulting from genetic drift, bottlenecks, inbreeding, etc.
habitat degradation
process by which habitat quality for a given species is diminished
habitat loss
habitat quality so low that environment is no longer usable by given species
ecosystem degradation
alterations to an ecosystem degrade/destroy habitat for many of the species that constitute the ecosystem
ecosystem loss
changes to ecosystem so profound to so many species (esp. dominant species) are lost so that ecosystem converted to another type (e.g. deforestation)
contamination: air pollution
- extensive research on effects on human and domesticated species, less on wild species
- destroy plant species downwind from factories
- eradicate lichen species
- diminish individuals’ health and ability to reproduce
- can make aquatic habitats more acidic
contamination: water pollution
- aquatic species more vulnerable than land species
- extinction of species in one place can lead to entire extinction b/c only found in one place
- less likely to cause extinction if in marine habitats
- eutrophication and harmful algal blooms
contamination: pesticides
- some benign and break down quickly, others wreak havoc (e.g. DDT)
- biomagnification = pesticides concentrate at top of ecosystem
human structures: roads
- curbs/lanes dividers absolute barriers to small, flightless mammals, etc.
- animals run down even if can cross
- provide access to habitats to people who want to exploit ecosystem
- may provide access for exotic species to infiltrate habitat
human structures: dams
- limits species’ ability to move up/down stream during mating season
- e.g. salmon populations eliminated by dams
soil erosion
- natural process accelerated by humans (e.g. agriculture)
- leads to habitat degradation and decreased productivity of land
fire regimes
- severe human fires can destroy habitats
- campaigns to prevent fire also too effective - low intensity fires suppressed, leads to accumulation of fuel
water use
- mostly used for agriculture than industry, domestic uses and reservior expansion
- when remove large quantity of water, biota affected
deforestation
- forests grow in places w/ fertile soil so desireable for agriculture
- slowed, stopped or reversed in some areas
- demand for forest in developed countries decreased b/c pop stabilised or shift away from agro
- still issue in tropical regions
- damages diverse ecosystems
desertification
- grasslands/woodlands being degraded until dominated by sparse unproductive veg.
- usually associated w/ overgrazing and cultivation
why do large fragements have more species than small ones?
- greater variety of environments
- provides niches for additional species
- likely to have common and uncommon species
- small fragment likely to only have common species
- larger samples have more species
history of overexploitation
- humans killed off woolly mammoth 11000 years ago
- overkill (most important factor)
- climate change
- disease
- human-set fires
- Polynesians arrive in NZ and kill off bird species
- all types of moas
- Madagascar extinction
- giant tortoises
- giant lemurs (etc.)
- N.America by colonials
- nearly eradicated turkeys, beavers
what are the two major forms of overexploitation?
- bushmeat
- overfishing
overfishing
- not given enough public scrutiny
- not sympathetic to fish
- fishing happens in sea + not w/in national boundaries
- fish stocks only recently starting to decline
- fish population phenomena
- ‘fishing down the food chain’
- predatory fish that used to dominate catches replaced by species further down food chain
- individual fisheries collapsing
- running out of new places to exploit (usually sustain total catch by fishing in remote and deep places)
- ‘fishing down the food chain’
bushmeat exploitation
- wild animal used for human food (esp. in tropical terrestrial ecosystems)
- profound effects
- loss of supply of protein
- exposure to HIV/AIDS and Ebola
- in W. Africa when have large fish supplies, lower bushmeat levels
- could be solved if Europeans stopped fishing off their coasts
commercial exploitation
why does this easily lead to over exploitation?
- huge potential markets for wild species
- enormous desire for wealth among exploiters
- domestic substitutes not identical to wild versions and therefore have lower prices
- market price of wild species increase as becomes rarer
- communal resources - costs shared among everyone
- wildlife found in remote places (lesser legal grip)
- exploiters have capital to purchase tech to gather wildlife in large quantities
- disparity in currencies makes selling rare species profitable
recreational exploitation
- examples
- hunters
- watchers
- anglers
- pros/cons
- bad b/c leads to overexploitation
- good b/c licenses fund conservation efforts
- even nonconsumptive exploitation can be harmful to animals b/c shy, etc.
incidental exploitation
- e.g. catching tuna w/ nets and drowning dolphins in process
- most destructive is trawling for shrimp
- killed turtles but now must have devices on trawlers to release turtles
indirect exploitation
e.g. roads, fences, etc.
consequences of overexploitation
- effects on large species worse b/c larger = more babies
- tend to hunt animals in reproductive prime or growth prime (i.e. cutting down trees) not at natural mortality
- tend to kill males more b/c larger and travel more therefore more contact w/people
- skewed pop can affect reproduction
- not worst b/c most males mate w/ many females (polygynous)
- can change genetic structure - kill best and leave worst
- change landscapes (cut down trees, no longer forest)
