BIOL 4100 Lecture Notes - Endangered Species, Species Richness, Restoration Ecology

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Conservation biology is guided by 3 basic principles:
Evolution is the process that unites all of biology
The ecological world is dynamic
Humans are a part of ecosystems
early photosynthetic prokaryotes and eukaryotes generated oxygen, making
Earth's atmosphere unsuitable for anaerobic organisms
plants accelerated weathering of the rocks, gaining access to rock-bound nutrients
endemic species – species that are found nowhere else
humans have been exterminating species for 1000s of years due to over-hunting
People value biodiversity because:
Humans depend on other species for food, fiber and medicine
Species are necessary for the functioning of ecosystems and the many
benefits and services those ecosystems provide to humanity
Human derive enormous aesthetic pleasure from interacting with other
species
Extinctions deprive us of opportunities to study and understand ecological
relationships among organisms
Living in ways that cause extinction of other species raises serious ethical
issues because species are judged to have intrinsic value
How Do Biologists Predict Changes in Biodiversity?
To preserve Earth's biodiversity, we need to both maintain the processes that
generate new species and provide conditions that will keep extinction rates no
higher than typical levels
4 reasons that scientists cannot predict the number of extinctions that will occur:
We do not know how many species live on Earth
We do not know where species live
It is difficult to determine when a species actually becomes extinct
We do not know what will happen in the future
North America's largest woodpecker, the ivory-billed pecker, was considered
extinct for 60 years until recently where there have been claimed sightings
Species-area relationship – a well-established mathematical relationship between
the size of an area and the number of species it contains
conservation biologists have measured the rate at which species richness
decreases with decreasing habitat patch size
found that a 90% loss of habitat will result in the loss of half the species that
live in and depend on that habitat
current loss of tropical evergreen forests (the most species-rich biome) is 2%
per year
conservation biologists develop statistical models that incorporate information
about a population's size, its genetic variation, morphology, physiology and
behaviour of its members to estimate risks of extinction
Endangered species – in imminent danger of extinction in all or a specific
part of their range
Threatened species – likely to become endangered in the future
rarity is not a cause for concern
species whose populations are suddenly shrinking rapidly are usually at high risk
species with special habitat or dietary requirements are more likely to become
extinct
populations with a few individuals confined to a small range can be easily
eliminated by local disturbances
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the golden toad in Costa Rica became extinct due to climate warming
What Factors Threaten Species Survival?
habitat loss is most important cause of species endangerment in the U.S.
Especially for species in freshwater
Fragmentation – as habitats are progressively lost to human activities, the
remaining patches become smaller and more isolated
small patches cannot maintain populations of species that require large
areas
Edge effects - the fraction of a patch that is influenced by factors originating
outside it increases rapidly as patch size decreases
species from surrounding habitats colonize on the edges of patches to
compete with or prey on species living there
species disappeared from isolated patches when the surrounding forest was
cut
species that are lost from small habitat fragments are unlikely to become
reestablished there because dispersing individuals are unlikely to find
isolated fragments
a species may persist in a small patch if it is connected to other patches by
corridors of habitat through which individuals can disperse
Invasive – when species spread widely and become unduly abundant, often at a
cost to the native species of the region
most introduced species are imported without their natural enemies, while native
plants must devote considerable energy to defending themselves against the
native herbivores
invasive plants generally have high rates of growth and reproduction
because they spend less energy in producing defensive compounds
introduced pathogens have destroyed whole populations of several eastern
North American forests
disease outbreaks usually leave no traces in the fossil record
due to human activities, average temperatures in North America will increase
about 2-5oC
organisms that are able to disperse easily may be able to shirt their ranges as
rapidly as the climate changes provided that appropriate habitats exist in new
areas
ranges of species with sedentary habits are likely to shift slowly
if Earth's surface warms as predicted, new climates will develop and existing
climates will disappear
new climates are certain to develop at low elevations in the tropics
if warming of oceans continues about 40% of coral reefs are likely to be killed
reefs adjacent to cool, upwelling waters and reefs in cloudy waters have
relatively low temperatures and are healthy
What Strategies Do Conservation Biologists Use?
Protected areas – an important component of efforts to preserve biological
diversity
preserve habitats while preventing the human exploitation of the species
living there may serve as nurseries from which individuals disperse into
exploited areas
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