Chapter 50

CHAPTER 50
AN INTRODUCTION TO ECOLOGY AND THE BIOSPERE
Lecture Outline
• The scope of ecology
• Organisms and their environment
• Ecological fields
• Factors affecting the distribution of organisms
• Dispersal & behavior
• Biotic & abiotic factors and the role of climate
• Major biomes
• Aquatic & terrestrial
• Spatial scale of distribution

Ecology
= the scientific study of the interactions between organisms and their environment

Fundamental questions:
--> What determines the abundance of a species?
--> What determines the limit of a species’ range?

Distribution and abundance of the red kangaroo in Australia (aerial surveys)

Environmental conditions
• Abiotic factors:
non-living chemical and physical factors

• Biotic factors:
the living components

Ecological fields
• Organismal ecology
• Population ecology
• Community ecology
• Ecosystem ecology
• Landscape ecology

• Organismal ecology:
concerned with the …
ways individuals interact with the environment
• often defines an ecological niche

• Population ecology:
examines factorsthat affect …
• Population: a population is a group of individuals of the same species living in a particular geographic area.

• Community:
consists of all the organisms of all the species that inhabit a particular area.

• Community ecology:
examines the … ,
and how factors such as
predation, competition,
and disease affect
community structure
and organization.

• Ecosystem: consists of all the abiotic factors in addition to the entire community of species in a certain area.
• Ecosystem ecology: examines the energy …
among the various abiotic and biotic components.

• Landscape ecology:
deals with the ….
• landscape or seascape:
consists of several different ecosystems linked by exchanges of energy, materials, and organisms

• Biosphere:
the global ecosystem that includes all of the planets ecosystems
• extreme variation
• environments are related by global processes
Ecology provides the scientific context for evaluating environmental issues
• The science of ecology isn’t simply concern about the environment
• Ecology: the science of examining delicate relationships between organisms and the environment

• Rachel Carson’s Silent Spring (1962)
• pesticides were causing wide-scale
declines in non-target organisms
• led to the modern environmental
movement

Biogeography
=

• contributes to the understanding what limits geographic distributions

• What limits the geographical distribution of any species??
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1.Dispersal contributes to a species’ distribution
• Is a species’ distribution limited because of limited dispersal?
Test: species transplants

Problems with ‘transplants’: introduced species

• Africanized honeybees
- African honey bee
introduced in 1956
(intentionally)
- hybridized with European
honey bees
- extremely aggressive
- drive out local bees
- move North
--> how far??

• Zebra mussel
- introduced in ~ 1985
(accidentially)
- with ballast water?
- reproduces rapidly
- filters algae (clear water)
- drives out native mussels
and other native species
- dense clusters ? clogs
water intakes etc.

• Round goby
- introduced in ~ 1990
(accidentially)
- with ballast water?
- reproduces rapidly

- feeds on eggs of native fish
-> endangers populations

- feeds on zebra mussel
-> is eaten by larger fish
-> introduction of
contaminants into
food chain

The Tens Rule
• Not all species thrive after an introduction:
• 13 of 98 species of birds introduced into North America thrived
• 13 of 85 species of birds introduced into Europe thrived

-->
-->

Biotic factors that affect the distribution of organisms
• Negative interaction with other species:
•
•
•

Abiotic factors affect the distribution of organisms
• Temperature --> preferred range

• Water --> essential for most organisms

• Sunlight --> provides energy

Abiotic factors affect the distribution of organisms
• Wind --> amplifies temperature effects

• Rocks and soil -->‘patchiness’ of ecosystems

Abiotic factors affect the distribution of organisms
• Climate --> prevailing weather conditions in an area
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• Global climate patterns:
• are largely determined by sunlight and the planet’s movement in space

• The angle of the earth’s axis is responsible for seasonal variations on the earth.

Fig. 50.13 Global air circulation, precipitation and winds

• Local and seasonal effects on climate.
• Bodies of water and topographic features such as mountain ranges can affect local climates:

• Ponds and lakes are sensitive to seasonal temperature change
--> lake stratification and seasonal turnover

• Microclimate:
• climate can vary on a small scale, on a forest floor or under a rock

• Long-term climate change:
• the ice ages affected distribution in the past
• climate changes have long-term effects on the biosphere
• global warming may affect distribution of organisms

• Marine biomes: cover ~ 75 %; salt concentration ~ 3 %
• Freshwater biomes: salt concentration less than 1 %

Zonation in a lake
• photic zone: zone through which light penetrates ? photosynthesis
• aphotic zone: very little light can penetrate
• thermocline: separates a warm upper layer from cold deeper waters
• benthic zone: bottom of any aquatic biome
--> detritus, dead organic matter
• littoral zone:
shallow and close to shore.
• limnetic zone:
open surface water
• profundal zone:
deep, aphotic regions

Zonation in a marine environment
• photic zone: zone through which light penetrates ? photosynthesis
• aphotic zone: very little or no light can penetrate
• intertidal zone: where land meets water
• neritic zone: shallow regions over continental shelves
• oceanic zone: open water
• pelagic zone:
open water of any depth
• benthic zone: seafloor
• abyssal zone:
benthic region in
deep oceans

• Lakes
• Oligotrophic lakes:
--

• Eutrophic lakes: shallower,
--

• Mesotrophic lakes: moderate amount of nutrients and phytoplankton productivity
--

• Streams and rivers are
bodies of water moving continuously in one direction.
Human impact
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• wetlands:
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• estuaries:
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• Examples of marine biomes:
• Intertidal zone
• Coral reefs
• Oceanic pelagic zone
• Benthos
• Abyssal zone

Geographic distribution of terrestrial biomes is based on regional variations in climate

• Tropical forests:
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• Savannas:
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• Deserts:
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• Chaparrals:
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• Temperate grasslands:
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• Temperate deciduous forests:
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• Coniferous forests:
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• Tundra:
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Geographic distribution of terrestrial biomes is based on regional variations in climate

Key terms 50
ecology
abiotic components
biotic components
organismal ecology
population ecology
community ecology
ecosystem ecology
landscspe ecology
seascape
biosphere
biogeography
dispersal
climate
biome
tropics
turnover
microclimate
photic zone
aphotic zone
thermocline
benthic zone
benthos
detritus
littoral zone
limnetic zone
profundal zone
intertidal zone
neritic zone
oceanic zone
pelagic zone
oligotrophic
eutrophic
mesotrophic
wetland
estuary
canopy
permafrost