An Introduction to Ecology and

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Chapter 50 An Introduction to Ecology and The
Biosphere
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I.  Scope of ecology             A.  Interactions
between organisms and their environment           
              1.  Ecology is the scientific
study of the interactions between organisms and
their environment.                               
       a.  Interactions determine distribution
and abundance of organisms.   b.  Three main
themes in ecology are               - Where do
organisms live?               - How many
organisms are present? - Why are they
located where they are?   Figure 50.2 p.1081 (Ed.
6 Figure 50.1 p. 1093) Distribution and
abundance of the red kangaroo in Australia, based
on aerial surveys.
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                                    c.  Ecology
was historically an observational science, often
descriptive à natural history.   d.  An
organisms environment has both abiotic and
biotic components.                                
                 - Abiotic components are
nonliving chemical and physical factors such as
temperature, light, water, and nutrients.         
                                        - Biotic
components are living factors such as other
organisms.
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2.  Ecology and evolutionary biology are closely
related sciences                                  
   a.  Events that occur in the framework of
ecological time (minutes, days, years) translate
into effects over evolutionary time (decades,
millennia).                                       
          Example  Hawks feeding on mice impact
mouse population and may eventually lead to
selection for mice with fur as camouflage.
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3.  Ecological research scale ranges from
individuals to the biosphere                      
               a.  Organismal ecology is about
the way in which an individual interacts with its
environment.   b.  Population ecology is the
study of a group of individuals of the same
species.   c.  Community ecology deals with all
interacting species within a particular area.
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                                    d.  An
ecosystem consists of all abiotic factors plus
all organisms that exist in a certain area à
Ecosystem ecology.   e.  Landscape ecology deals
with ecosystems that exist within an area and the
exchange of energy, material and organisms
between these ecosystems. f. The biosphere is
the global ecosystem.  Global climate research is
an example of ecology at the biosphere
scale.   Fig. 50.3 p. 1082 (Ed. 6 Fig. 50.2 p.
1094) Sample questions at different levels of
ecology.
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II.  Factors affecting the distribution of
organisms             - Biogeography is the
study of past and present distribution of
individual species.    Fig. 50.5 p. 1084 (Fig.
50.4 p. 1095) Biogeographic realms.
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• A.  Species dispersal contributes to the
  distribution of organisms
•                        
• ? Dispersal refers to the process of distribution
  of individuals within geographic population
  boundaries.
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• Question Is the distribution of a species
  limited by dispersal, i.e. by movement of the
  organisms?
• Answer can be obtained by transplant experiments.
  
• If the transplant is successful, then the
  organisms just havent reached the target area.
• If the transplant is not successful, then other
  factors limit the distribution of the organisms,
  such as competitors, lack of a food source, etc.

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a.  Introduced species sometimes have disasterous
impacts            - African honeybee, Zebra
mussels   Fig. 50.7 p. 1097 (ed. 6 only) Spread
of the African honeybee in the Americas since
1956.
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Figure 50.8 p. 1098 (ed. 6 only) Expansion of
the geographic range of the zebra mussel since
its discovery near Detroit in 1988.
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            B.  Behavior and habitat selection
contribute to the distribution of
organisms                         1.  Organisms
may not occupy all potentially suitable habitat. 
Why?             a.  Evolution doesnt lead to
perfect organisms.   b.  Evolution is
an ongoing process.  Environments change, but it
takes a while for organisms to respond.           
    C.  Biotic factors affect distribution        
                 1.  Organisms required for
potential community members to colonize may be
lacking.            - Pollinators, prey,
predators that limit competition   Figure 50.9
(p. 1099, ed. 6 Fig. 50.8, p. 1086, ed. 7)
Predator-removal experiments.
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D.  Abiotic factors affect distribution           
              1.  Abiotic factors of interest
include                                     -
Temperature (range from 0 to 45
C)                                     -
Water                                     -
Sunlight (water absorbs light, limits area of
photysnthesis                                    
- Wind (increases heat loss)                     
                - Rocks and soil
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2.  Two important ecological occurrences         
                            a.  Seasonal
variation ? alters temperature and
precipitation.    Fig 50.10 p. 1088-1089 (Ed. 6
Fig. 50.12 p. 1102) What causes the seasons?
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                                    b.  Lake
stratification and mixing ? alters oxygen and
nutrient levels. Dependent on temperature
changes and effect on water density.   Fig 50.13
p.1091 (Ed. 6 Fig. 50.15 p. 1104) Lake
stratification and seasonal turnover.
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III.  Aquatic and terrestrial biomes (Biome
major ecosystem type) ? Read and know pages
1106-1117 (ed. 6) or pages 1092-1103 (ed. 7) with
pictures of major biomes
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 A.  Aquatic biomes cover about 75 of the
earths surface                         -
Wetlands                         -
Lakes                         - Rivers,
streams                         - Intertidal
zones                         - Oceanic pelagic
biome                         - Coral
reefs                         -
Benthos                           Fig. 50.15 p.
1092 (Ed. 6 Fig. 50.17 p. 1106) The
distribution of major aquatic biomes.
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Oligotrophic Lake Nutrient poor, water is
clear, oxygen rich little productivity by algae,
relatively deep with little surface area.
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Eutrophic lake nutrient rich, lots of algal
productivity so its oxygen poor at times, water
is murkier ? often a result of input of
agricultural fertilizers
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Rivers and Streams Organisms need adaptations so
that they are not swept away by moving water
heavily affected by man changing the course of
flow (E.g. dams and channel-straightening) and by
using rivers to dispose of waste.
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Wetlands includes marshes, bogs, swamps,
seasonal ponds. Among richest biomes with
respect to biodiversity and productivity. Very
few now exist as they are thought of often as
wastelands.
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Estuary Place where freshwater stream or river
merges with the ocean. Highly productive biome
important for fisheries and feeding places for
water fowl. Often heavily polluted from river
input so many fisheries are now lost.
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Marine environment with zonation.
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Intertidal Zone Alternately submerged and
exposed by daily cycle of tides. Often polluted
by oil that decreases biodiversity.
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Coral Reefs occur in neritic zones of warm,
tropical water, dominated by cnidarians (corals)
very productive, protect land from storms most
are now dying from rise in global temperatures
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Deep-sea vent Occurs in benthic zone diverse,
unusual organisms such as 1-m long worms energy
comes not from light but from chemicals released
from the magma.
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B.  Terrestrial biomes                         -
Tropical forest                         -
Savanna                         -
Desert                         -
Chaparral                         - Temperate
grassland                         - Temperate
deciduous forest                         -
Coniferous forest                         -
Tundra                           Fig. 50.19 p.
1099 (Ed. 6 Fig. 50.24 p. 1112) The
distribution of major terrestrial biomes.
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Tropical Forest Vertical straitification with
trees in canopy blocking light to bottom strata.
Many trees covered by epiphytes (plants that grow
on other plants).
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Example of Tropical, Dry Forest
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Savanna Dominate animals are insects (termites
and ants). Grasses are dominant plants that are
productive in rainy season. Fire during drought
is frequent and life is adapted for it, such as
migration by large animals.
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Desert Sparse rainfall (lt 30 cm per year),
plants and animals adapted for water storage and
conservation. Can be either very, very hot, or
very cold (e.g. Antarctica)
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Chaparral Dense, spiny, evergreen shrubs, mild
rainy winters long, hot, dry summers. Periodic
fires, some plants require fire for seeds to
germinate.
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Temperate Grassland Marked by seasonal drought
and fires, and grazing by large animals. Rich
habitat for agriculture, very little prairie
exists in US today.
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Temperate Deciduous Forest Mid-latitudes with
moderate amounts of moisture, distinct vertical
strata trees, understory shrubs, herbaceous
sub-stratum. Loss of leaves in cold, many
animals hibernate or migrate then. Original
forests lost from North America by logging and
clearing.
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Coniferous forest Largest terrestial biome on
earth, old growth forests rapidly disappearing,
usually receives lots of moisture as rain or snow.
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Tundra Permafrost (Permanent frozen ground),
bitter cold, high winds and thus no trees. Has
20 of land surface on earth.