Community Ecology

1
Community Ecology

• By
• Diana Capalbo,
• Jane Joseph,
• Nicole Rebusi
• Sunny Yoo

2
These sprays, dusts, and aerosols are now
applied almost universally to farms, gardens,
forests, and homes-nonselective chemicals that
have the power to kill every insect, the 'good'
and the 'bad,' to still the song of birds and the
leaping of fish in the streams, to coat the
leaves with a deadly film, and to linger on in
soil-all this though the intended target may be
only a few weeds or insects. Can anyone believe
it is possible to lay down such a barrage of
poisons on the surface of the earth without
making it unfit for all life? They should not be
called 'insecticides,' but 'biocides. ---Rachel
Carson, Silent Spring
3
Biodiversity in an Ecological Community

• Biodiversity is the range of organisms present in
  a particular ecological community or system.
• Chapter 53 discusses the biogeographic features
  that affect community biodiversity. These factors
  include
• Geographic size on the community Species
  richness is directly related to geographic size,
  and this is shown in the Species-Area Curve
• Equatorial Polar Gradients Species richness
  generally declines along an equatorial polar
  gradient.

• Silent Spring describe many human activities that
  affect biodiversity. These include
• - Environment Destruction Destruction of
  habitats all over the world is happening so that
  agriculture, and urban development can take
  place.
• -Introduced Species Humans move species to new
  places, which can cause rapid growth in
  population of the species in the new area, and
  cause more competition in an are
• -Biological Magnification Since species become
  immune to certain pesticides or insecticides,
  causing them to adapt and grow stronger thus
  affecting the community they live in.

4

• A community is an assemblage of populations of
  various species living close enough for potential
  interactions.
• Ex trees and shrubs in Shenandoah national park.

5

• Interspecific interactions key relationships in
  the life of an organ is in its interactions with
  other species in the community.
• They include competition, predation, herbivory,
  parasitism, mutualism, commensalism and disease.

6

• Interspecific competition is more likely to occur
  in our world today because so many resources are
  limited because of insecticides and harmful
  toxics.

7

• The animals that ate the plants quickly died
  which led second consumers to interspecific
  competition.

8

• Also chemicals pass through water which lead to a
  short supply of clean water which leads to
  interspecific competition.

9

• More then 200 basic chemicals have been made to
  kill pests which lead carnivores to a limited
  supply of meat which also lead to interspecific
  competition.

10

• Biological niche- organisms job in the community
  since harmful chemicals were released to many
  types of organisms including bees, the balance of
  nature has been thrown out of control. The bees
  niche is to pollinate flowers but if the flowers
  were harmful to the bees then the bees will not
  be able to pollinate the flowers which lead to no
  fruition which leads to a decreased amount of
  food which leads to competition and competitive
  exclusion principle.

11

• Strontium used in nuclear explosions was planted
  in the soil which contaminated plants which
  caused interspecific competition.

12
Food Webs

• In her novel, Silent Spring, Rachel Carson
  suggests ways in which DDT and other
  pesticides/insecticides are spreading to
  different species often causing death and
  illnesses amongst these species.
• Food webs are a series of food chains linked
  together which are used by ecologists to
  summarize the trophic relationships of a
  community (the feeding relationships between
  organisms).

13
And No Birds Sing

• According to the novel, food webs play an
  important role of the spread of DDT and other
  pesticides/insecticides proven by real-life
  events.
• In 1954, Dr. Wallace and Mr. Mehner at Michigan
  State University researched robin populations
  during the spraying for the Dutch elm disease on
  campus.
• However, when the robins migrated back the
  following spring they were found dead and dying
  all over the campus because of insecticidal
  poisoning.

14
And No Birds Sing (continued)

• Dr. Roy Barker of the Illinois Natural History
  Survey at Urbana traced that the robins fate
  were in the hands of the food web with the elm
  tree as its primary producer.
• The DDT sprayed on the trees sent a streaming
  poison to all parts of the trees while forming a
  poisonous film over the leaves and bark.
• When the leaves fall to the ground, they become
  one with the soil which in turn is fed on by the
  earthworms elm being one of its favorite foods.
  Thus, swallowing the insecticide into their
  bodies becoming biological magnifiers of the
  poison.

15
And No Birds Sing (continued)

• One of the robins main foods are earthworms.
• Therefore, after the robin has consumed enough
  earthworms with DDT it was most likely to die
  resulting in the end of the food web.

16
Poison Through The Web

• This example is one of many that have occurred
  during the naïve usage of DDT and other
  pesticides/insecticides.
• The spraying of this poison has contaminated
  plant life, the primary producers, which are
  consumed by animals and humans therefore creating
  a great epidemic throughout the trophic
  structure (feeding relationships) of life causing
  death and illnesses which could lead to
  extinction.

17
Humans have the greatest impact on biological
communities.

• A disturbance is an event, such as a storm, fire,
  flood, drought, overgrazing, or human activity,
  that changes a community, removes organisms from
  it, and alters resource availability.

18
(No Transcript)
19

• Predation- herbivory- since DDT is fat soluble it
  will build up as it moves in the food chain. The
  storage of DDT begins with the smallest
  conceivable intake of chemical and continues
  until quite high levels are reached. The fat
  storage depots act as biological magnifiers, so
  that an intake of a little as 1/10 of 1 part per
  million in the diet results in storage depots
  about 10 to 15 parts per million, an increase of
  one hundredfold or more.

20

• Diseases now are multiple-created radiation in
  all its forms. As we contaminate soil, water, and
  food we also poison the organism that uses them
  to survive and then eventually humans will be
  poisoned.

21
Chemicals Affect the WHOLE Ecological
CommunityTAKEN FROM SILENT SPRING

• In less than two decades of their use, the
  synthetic pesticides have been so thoroughly
  distributed through the animate and inanimate
  world that that they occur virtually everywhere.
  Residues of these chemicals linger in soil to
  which they may have been applied a dozen years
  before. They have entered and lodged in the
  bodies of fish, birds, reptiles, and domestic and
  wild animalsThey have been found in fish in
  remote lakes, in earthworms burrowing in soil, in
  the eggs of birds and in man himself (pgs 15
  and 16)
• The problem of water pollution by pesticides can
  be understood only in context , as a part of the
  whole system to which it belongs (pg39) Water
  must also be thought of in terms of the chains of
  life it supports- from the small as green cells
  of the drifting plant plankton, through the
  minute water fleas to the fishes that strain
  plankton from the water and are in turn eater by
  other fishes or by birds, mink raccoon in a n
  endless cyclic transfer of materials from life to
  life (pg 46)

22

• The world may find that insects and rodents are
  pests but in reality, pests are part of our
  community and they contribute a niche and balance
  to all other life forms. So instead of trying to
  eliminate organisms we do not like, we should
  appreciate all living things because our lives
  are not able to exist without theirs.