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Ch. 16
What is biodiversity?
Species richness (# of species) and
genetic diversity within populations
Case study: the bald eagle
Factors affecting near extinction:
– Habitat destruction (forests)
– Hunted
– Slow reproductive rate
– DDT  thin eggs cracked prematurely
– Other pollutants: lead and mercury
– DDT banned in US (1972)
– Bred in captivity and then released
Why does biodiversity matter?
ecosystem services: pollination depends on insects,
bacteria decompose, presence of one organism
keeps the # of others in check
Greater variety of genes in crops allows for
“crossing” to become more pest resistant
Genetic engineering relies on existing genes – Ex:
insulin, cows making more milk, pest resistant
Medicines: Ex AZT (AIDS) from sponges
Supply other products: wool, paper, cork,
Aesthetic/ethical – beauty, all organism have value
What’s causing its loss?
Habitat destruction!!!!! (includes fragmentation): build roads
and buildings, clear forests to grow crops, drain marshes to
build, divert water for irrigation, flood habitats with dams.
Linked to increasing human population – need for food and
space. Ex: elephants/Africa
Invasive species – compete for food, no natural predators,
prey on other species ex: Kudzu, brown tree snake eating
birds in Guam
Pollution – acid rain destroys plants/change water pH, ozone
depletion increases solar radiation, climate warming. Hurt
organisms with narrow environmental requirements. (condor –
require lg. territories - poisoned by lead in bullets in carrion)
Overexploitation – killed for fun, b/c a nuisance, or profit,
commercial harvest (live organisms) Ex: elephants
(human caused)
Case study: amphibians
Are bellweather species (sentinel
species) - #s are early warning of
environmental damage
 Reliant on water for reproduction, early
life cycle, breathing – sensitive to
 Declining numbers and deformities
 Reasons:
 Pesticides like atrazine – endocrine
 thinning ozone increase UV radiation
What can humans do about
preserving biodiversity?
Conservation biology: in situ (in nature) and ex situ
conservation (in human controlled settings)
– Protecting habitats – larger the better, prioritize high
diversity areas, national parks
• Problems: governments unable/unwilling to enforce laws
– Restoring habitats - $$
– Reintroduction of species – from elsewhere or captivity
– Zoos (artificial insemination), botanical gardens, seed
– Provide economic incentives to local people : pay for
discovery of helpful plants, ecotourism, reduce debt in
exchange for preserving biodiversity. Ex: Madagascar
and US
Endangered Species Act (1973)
Gives US Fish and Wildlife Service power to protect
(from hunting, collecting, harming habitat) endangered
and threatened species
Traits of endangered species:
 requiring a large territory: CA condor
 island living – many found nowhere else (endemic),
evolved w/o predators and diseases and then vulnerable
 low reproductive success – green sea turtle particular
 small population size – need enough males/females
 specialized feeding habits – pandas only eat bamboo
Marine Mammal Protection Act
Prevents hunting, killing, capturing, or
harassing a marine mammal
 Bans the import, export, and sale of
marine mammals or parts
(Convention on International Trade in
Endangered Species)
Where is it the greatest problem?
Tropical rain forests
 Central/South America, central Africa,
Southeast Asia
 Migratory birds
Biodiversity hotspots – small areas with
high number of endemic species
 Most are tropical; many are islands