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Ecological Niche
• A description of the role played by a species
in a biologic community
• The total set of environmental
conditions/factors that determine a species
• A species that can adapt to a wide range of
environments (“r-adapted”)
– raccoons, rats, wolves, dandelions
• Can adept quickly to changes
• Opportunistic - appear quickly
wherever an opening exists.
• Pioneer species - first to appear
• A species specifically adapted to a very
narrow niche or range of conditions
– pandas, koalas, wild roses
• Much less resilient to change, adept
very slowly
Law of Competition
• no two species will occupy the same
ecological niche and compete for exactly
the same resources in the same habitat for
very long.
– One group or the other will gain an advantage
forcing the other group to move or change
behavior or become extinct
– resource partitioning - adaptations geared to
reduce competition in the same habitat
Species Interactions
• Predation
– Predator - any organism that feeds
directly on another living organism
(Carnivores prey on other animals,
Herbivores prey on plants,
Omnivore prey on both
• Parasites and pathogens can also be
considered predators
• Competition
– Intraspecific competition
• competition within a species
– Interspecific competition • competition between species
Can result in Coevolution
• Symbiosis
• the intimate living together of members of
two or more species
• Unlike predation and competition,
symbiosis can be beneficial to all involved
parties (but not always).
• Commensalism: - "eating together at the
same table" - in this association one
member, usually the smaller, derives benefit
from the association, whereas for the other
member, the association is neither beneficial
or harmful. The relationship can be that of
sharing space, substrate, defense, shelter,
transport or food.
• Ex. Some species of barnacles are found
only as commensals on the jaws of whales.
• The Remora fish (Echeniedea) is a long slender
fish which has its dorsal fin modified as a suckerlike attachment organ. It attaches to the sides of
larger fish and turtles using them as transport hosts
but in addition, obtains food fragments dropped
from the host.
• Mutualism: As the name would suggest this is an
association in which both organisms derive mutual
• associations are seen in cleaning fish often seen
around sharks feeding on parasites in the mouth
and gills. The Egyptian plover performs a similar
service by cleaning the mouth of crocodiles.
• Tick birds on rhinos and ox pecker birds on
various antelopes also share a mutual relationship.
In addition to removing ticks and other irritating
insects, the ox peckers often signal the presence of
predators to the antelopes.
• Parasitism
• " A parasite is an organism living in or on
another living organism, obtaining from it
part or all of its organic nutriment, usually
to the detriment of its host.“
• Examples of parasitism include: tick-dog;
Defensive Mechanisms
• Development of some mechanism by which
to hide better or to defend oneself from
attack. Toxins, smells, stingers or nettles,
body armor
• Evolving to look like something else
– looking like a more dangerous animal
– looking like something inedible
– looking safe - thereby preying on other
• From left to right are the Common Wasp, Vespula
vulgaris, and some of its mimics - the Hornet
Moth, Sesia apiformis, the Wasp Beetle, Clytus
arietis, and the Hoverfly, Syrphus ribesii.
Keystone Species
• a species or group of species whose impact
or involvement on its community/ecosystem
is larger or more influential than expected
from its mere abundance
• Absence of this/these species can reek
havoc on an ecosystem
• “life zones” environments with similar
climate, topography, soil conditions, and
roughly similar biologic communities
– Tundra, Tropical Rainforest, Grassland, …
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
World biome map
Figure 5.3
• the variety of living things
– genetic diversity - The genetic diversity within a
species is primarily the variety of populations that
comprise it. (populations with different genes).
– species diversity- a “population” the individuals of a
species that live together, group from which mates
are chosen
– ecological diversity - the entire composition of a
biologic community
– habitat diversity- the variety of places where life
exists -- coral reefs, old-growth forests in the Pacific
Northwest, tallgrass prairie,
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Known living species
1.4 million
estimate that
there are
between 3 and
50 million
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Biodiversity “hot spots”
Figure 5.20
Hotspot - a concentration of the worlds biodiversity
- commonly equatorial or island based
• Food
• Drugs and Medicine (> 50% of all
medications contain some natural products)
• Ecological Benefits - soil production,
nutrient cycling, food production, water
cycling and purification
• Aesthetic and Cultural
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Natural medicinal products
Human Caused Reductions
• Habitat Destruction
– Fragmentation
Hunting and Fishing
Commercial Products
Live Specimen Trade
Predator and Pest Control
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Mass extinctions
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Human disturbance
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
U.S. wetland acreage
Figure 5.24
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Extinctions and population - Minimum Viable Population
Figure 5.27
Source: Data from H. L. Jones and J. Diamond, “Short-term-base Studies of Turnover in Breeding Bird Populations on the
California Coast Island,” in Condor, vol. 78:526-549, 1976.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Endangered species
Exotic Species
• Exotic organisms are organisms which are
introduced into habitats/ecosystems where
they are not native (i.e. did not evolve
within that community)
• one of the greatest threats to biodiversity
worldwide !
Kudzu vine
Introduced in 1930s by US Soil
Conservation Service to control soil
Kudzu vine
Leafy spurge
Introduced in 1870s by farmers from Russia
The entire plant is poisonous and crowds out food crops
Leafy spurge
Purple Loosestrife
Introduced by gardeners in early 1800s for its pretty purple
flowers. Grows anywhere it is wet, chokes wetlands,
rendering them inhospitable to native plants and wildlife
Purple Loosestrife
Discovered in North America in 1988. Marine biologists believe it
arrived by transatlantic ship-an undetected stowaway in ballast
water that was discharged, mussel larvae and all, into Lake St. Clair,
between Lakes Huron and Erie. Since then, the prolific creature has
spread rapidly throughout lakes and waterways of the eastern
United States and Canada, from the Great Lakes through the
Mississippi River drainage. It remains unchecked by predators or
Zebra Mussels
Asian Long-Horned Beetles
Introduced in 1996, from China
this is a wood eating insect with
no natural predator in the United
Asian Long-Horned Beetles
Flathead Catfish
• Not all destructive alien species come from distant
lands. The flathead catfish poses no threat within
its native range of the lower Great Lakes,
Mississippi River basin, and parts of the Gulf
slope drainage. But when introduced to new
waters as a sportfish, it's a different story. Now
found in the rivers and reservoirs of 18 states
where it was previously unknown, this catfish is
depleting native fish populations.
Flathead Catfish
Brown tree snake
• On the Pacific island of Guam, the forests are
strangely silent, devoid of bird song. There are no
bird songs because there are few birds. They have
been wiped out by the brown tree snake (Boiga
irregularis). A native of the Solomon Islands,
Papua New Guinea, and northern Australia, the
reptile was accidentally introduced to Guam in the
1940s. It probably arrived via military transports
after World War II. Since then, the snake has
spread throughout the island, reaching numbers of
12,000 per square mile in some forested areas.
Brown Tree Snake
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