competition arises when organisms try to make use of the same resources
Post on 17-Dec-2015
216 Views
Preview:
TRANSCRIPT
Intraspecific competition
occurs when individuals of the same species compete for a limiting resource. (e.g. food, light, nutrients, space).
Competitive Exclusion
Strong competition can lead to competitive exclusion, local elimination of a competing species
The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place
G.F. Gause – Competitive Exclusion Principle
G.F. Gause – In 1932 developed
the CEP after researching mixed
cultures of yeast and Paramecium.
He concluded that no 2 species
can occupy the same niche at the same time. Over time, one species will be
more successful & outcompete the other.
Ecological Niches
The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche
An ecological niche can also be thought of as an organism’s ecological role
Ecologically similar species can coexist in a community if there are one or more significant differences in their niches
Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community
Robert MacArthur (1930 - 1972)
Studied 5 speciesOf warblers which appeared to be competing for the same resource. MacArthur’s research determined that each species actually spent most of its time feeding in different parts of the tree and ate different subsets of insects in the tree.
Fig. 54-2
A. ricordii
A. insolitus usually percheson shady branches.
A. distichus perches on fenceposts and other sunny surfaces.
A. alinigerA. distichus
A. insolitus
A. christophei
A. cybotes
A. etheridgei
Toxins in the Environment
Humans release many toxic chemicals, including synthetics previously unknown to nature
In some cases, harmful substances persist for long periods in an ecosystem
One reason toxins are harmful is that they become more concentrated in successive trophic levels
Biological magnification concentrates toxins at higher trophic levels, where biomass is lower
PCBs and many pesticides such as DDT are subject to biological magnification in ecosystems
In the 1960s Rachel Carson brought attention to the biomagnification of DDT in birds in
her book Silent Spring
Fig. 55-20
Lake trout4.83 ppm
Con
cen
trati
on
of
PC
Bs
Herringgull eggs124 ppm
Smelt1.04 ppm
Phytoplankton0.025 ppm
Zooplankton0.123 ppm
Ozone Shield Depletion
Pertains to O3 in stratosphere Chlorine atoms from CFCs destroy O3
ex. Freon cleaning agents foaming agents egg carton insulation & padding
Ozone shield is critical for all living things
UV radiation causes mutations leading to:
skin cancer cataracts impairment of immune system
Also affects crop & tree growth and will kill off algae and krill.
History on ozone depletion
Problem identified in 1980’s Esp. above Antarctic in the spring Propellants were banned in aerosols 1995 – U.S. halted production of CFCs Chlorine pollution began to decrease 2000 – longer lasting polar clouds
contribute to breakdown of O3 by chlorine
pollution.
top related