54
Ecology and the Geography of Life
Lecture Outline
I.
Natural selection adapts each organism to its environment
The environment has both abiotic and biotic components
II.
Biomes
Biomes are large terrestrial regions characterized by similar climate, soil, and
living things
A landscape is a large land area composed of interacting ecosystems
Tundra is the cold, boggy plains of the far north
Tundra is found in the far north where snow melts seasonally
The growing season in the summer is characterized by long days
Tundra has very little precipitation
The nutrient-poor soil lies over the permafrost
Lichens, mosses, grasses, and sedges dominate the vegetation
Many birds are migratory; permanent residents include many rodents and hares, and
insects are abundant in the summer
Taiga is an evergreen forest of the north
The taiga, or boreal forest, is found in the northern continents
Taiga has a longer growing season, but little precipitation
Taiga has deciduous trees, but conifers dominate
The taiga yields much lumber and pulpwood
Temperate rain forest is characterized by cool weather, dense fog, and high precipitation
The temperate rain forest exists in the NW United States, SE Australia, and southern S.
America
Dominant trees are conifers
This biome yields much lumber and pulpwood
The old-growth forest is rapidly being replaced by a monoculture
Temperate deciduous forest has a dense canopy of broad-leaf trees
The trees overlie saplings and shrubs
This biome is characterized by great seasonal variation in temperature and moderate
precipitation
The temperate deciduous forest once had much more rich fauna
This biome has been converted to agriculture in many areas of the world
Grasslands occur in temperate areas of moderate precipitation
Temperature extremes mark grasslands
Most native grasslands have been converted to agriculture, as they are well suited to
raising cereal crops
Chaparral is a thicket of evergreen shrubs and small trees
Chaparral occurs in California, Western Australia, Chile, South Africa and the
Mediterranean area
Chaparral is dominated by drought-resistant shrubs and scrub and is adapted to fire
Deserts are arid ecosystems
Deserts are dry areas found in temperate (cold deserts) and subtropical or tropical
regions (warm deserts)
Low precipitation results in sparse vegetation
Desert plants often exhibit allelopathy
Desert plants tend to be small and often aestivate during periods of drought
Savanna is a tropical grassland with scattered trees
Savanna is found in Africa, S. America, W. India, and N. Australia
The greatest abundance of hoofed mammals occurs in the savanna
Savanna is often converted to rangeland for domesticated animals
There are two types of forests in tropical areas
Tropical dry forests have both a wet and dry season
Tropical rain forests are lush equatorial forests
Tropical rain forests are characterized by high precipitation and high temperatures
The soils in this biome are old and have little organic matter
The tropical rain forest is unrivaled in plant and animal diversity
The plant community is characterized by layers, many epiphytes, and lianas (woody
vines)
This biome is threatened by overpopulation of indigenous people and exploitation of
resources by developed countries
III.
Aquatic ecosystems occupy most of the Earth’s surface
A. Aquatic is classified primarily on abiotic factors but also on types of
organisms
Aquatic ecosystems vary in temperature, salinity, dissolved oxygen, and current
There are three ecological categories of organisms
Plankton are organisms that are at the mercy of currents and waves
Phytoplankton are the photosynthetic organisms
Zooplankton are heterotrophic protozoans and animals
Nekton includes organisms that swim more strongly
Benthic organisms live on or in the bottom
Freshwater ecosystems are closely linked to land and marine ecosystems
Freshwater ecosystems include flowing-water ecosystems, standing-water ecosystems,
and wetlands
These bodies of water make up a small portion of the earth’s surface, but are ecologically
important and may moderate temperatures of adjacent terrestrial ecosystems
Rivers and smaller streams are flowing-water ecosystems
Headwater streams are typically shallow, fast-flowing, and highly oxygenated
Headwater streams are dependent on detritus as a primary energy
input
Rivers are typically deeper, slower flowing, and have less dissolved oxygen
Organisms found in the different flowing water habitats are adapted to these
characteristics
Ponds and lakes are standing-water ecosystems
Lakes of a substantial size can be divided into the littoral, limnetic, and profundal zones
The littoral zone is the shallow zone surrounding the lake and may
have emergent and nonemergent plants
Phytoplankton are the base of the food chain in the limnetic zone
The profundal zone is below the depth of light penetration
Thermal stratification occurs in temperate lakes
Large temperate lakes stratify in both the summer and winter
The thermocline is the zone of rapid temperature change
The fall and spring turnovers are the times of mixing
Increased nutrients, stimulated by human activities, stimulate algal growth
Enrichment caused by human actions leads to eutrophication
Freshwater wetlands are transitional between aquatic and terrestrial ecosystems
Freshwater wetlands include hardwood bottomland forests, prairie potholes, and peat
bogs
Wetlands are important in flood control, breeding sites for birds, and recharge of
groundwater; these are called ecosystem services
Estuaries occur where fresh water and saltwater meet
Temperate estuaries typically encompass salt marshes dominated by grasses and sedges
Estuaries undergo marked changes in temperature, salinity, and other physical
characteristics
Salt marshes are very productive, and are important breeding sites for fish
Mangrove forests dominate in tropical areas and are also important breeding sites for
fish
Estuaries and other coastal areas are threatened by population growth and economic
development
Two-thirds of the world's population lives within 150 km of a coastline, and therefore
these areas are impacted by our activities
Marine ecosystems dominate Earth’s surface
The intertidal zone is transitional between land and ocean
The intertidal zone is the area between the low and high tides
This highly productive zone is also a very stressful habitat
Sandy intertidal zones are characterized by shifting sand
Rocky intertidal zones provide anchorage for algae and animals
Animals and plants have adaptations to avoid desiccation
Seagrass beds, kelp forests, and coral reefs are part of the benthic environment
The benthic environment is the ocean floor
The abyssal zone extends from a depth of 4000 to 6000 meters
The hadal zone is greater than 6000 meters
Seagrasses are flowering plants adapted to being submerged
Kelps are the largest brown algae; they are the primary photosynthesizers in kelp forests
and also provide habitats for marine animals
Coral reefs are very productive benthic habitats, and are restricted to shallow depths as
the coral require zooxanthellae
Fringing reefs surround an island
The barrier reef is widely separated from the island
An atoll is a circular reef surrounding a lagoon, and is the final stage of
reef development
The neritic province consists of shallow waters close to shore
The neritic province is the area of open ocean lying over depths up to 200 m
The euphotic region is the lit zone where photosynthesis occurs
Zooplankton eat phytoplankton, and nektonic organisms eat zooplankton
The oceanic province comprises most of the ocean
The oceanic province is characterized by depths greater than 200 meters
Marine snow is organic debris that "rains" down into the euphotic region
Overfishing is a threat to the neritic and oceanic provinces
Many commercially important fishes have reached commercial extinction due to over
fishing
The Georges Bank, off the coast of New England, was once a very important fishery, but
now has a fishing moratorium due to overfishing
IV.
V.
Ecotones
B. All biomes and ecosystems interact in ecotones
Biogeography
C. Biogeography is the study of geographical distribution of plants and animals
Biogeographers search for patterns in geographical distribution and try to explain how
such patterns arose
A basic tenet of biogeography is that each species arose only once
The place where this occurred is known as the species' center of origin
The range of a particular species is that portion of the Earth on which it is found
Localized, native species are said to be endemic
Species having a worldwide distribution are cosmopolitan
Land areas are divided into six biogeographical realms
The Neartic and Paleartic realms are more closely related than the other regions
The Neotropical realm was almost completely isolated from the Neartic realm and other
land masses for most of the last 70 million years
The Ethiopian realm contains the most varied vertebrates of all six realms
The Australian realm has not had a land connection with the other realms for more than
85 million years and is dominated by marsupials and monotremes
Research and Discussion Topics

Which biomes or oceanic zones are characterized by the highest diversity? Lowest
diversity? Highest and lowest biomass? What animal groups are restricted in their
distribution in biomes and zones? More importantly, why are they restricted to
these zones? Critically analyze plant communities with respect to the previous
questions. Are the answers the same or different? Why?