Ecology – Biology 3500
Review Sheet Number 1 (Test 1):
Ecology – Study of interactions between organisms and their environment. Understand
that "environment" includes virtually EVERYTHING that the organism can interact with,
including individuals of their own species, all other organisms, and the physical environment
as well -- the air, water, soil, weather events, fire, temperature extremes, and even cataclysmic
events such as tidal waves, avalanches, volcanic eruptions (with all that comes with it: ash, lava,
and related effluvia), and, yes asteroid impacts. Needless to say, these interactions are, in turn,
intimately tied into the evolution of the organisms, as all of these interactions are the natural
selective processes that shape the adaptations of the organisms through time.
Chapter 1: What is Ecology?
Overview: can be studied on many levels -- individual, population, community, ecosystem,
and larger regional and even global interactions.
Some quick examples:
1. MacArthur -- resource partitioning by forest warblers; we will do a related lab later in the
2. Nadkarni -- plant nutrient resources in the tropical rain forest, including epiphytes and the mats
they form in the canopy; host trees can tap into the mat with adventitious roots.
3. Davis -- plant community changes through time; the soil pollen record in sediment
NATURAL HISTORY and EVOLUTION UNIT
Chapter 2: Life on Land
Biomes -- major divisions (large scale communities) of the (terrestrial) environment
Major atmospheric determinants of biome (community) composition:
1. Temperature -- heating by the sun; particularly important are the extremes
2. Moisture -- precipitation (and humidity/dew points)
3. Atmospheric Circulation (which is an important controller of temp. and precip.)
To keep in mind: geographic variation in temperature and precipitation is complex, and
there is no single one item that controls temp and amount of precip on Earth's surface
Make sure to read about climate
diagrams (pgs. 15-17), and be able to interpret them.
Also understand, however, that a climate diagram represents average climate, and that
individual years can vary a lot, leading to moist years versus drought years (see pgs. 40-41).
Soils -- complex mixtures of living and non-living
material, typically with distinctive layering.
This, of course, is another major determinant of biome composition
Horizons: O, A, B, C (and the underlying bedrock)
Understand general characteristics of each.
Horizons may be of differing depths, depending on many factors (precip and leaching,
current biological activity, disturbance by man [tilling], etc.)
The Natural History of Biomes: For each of the listed biomes,
you should know basic
characteristics. These include: amount and timing (wet/dry seasonality) of precipitation,
temperature driven seasonality (if apparent), location on the face of the planet, characteristics
of the soils, and typical floral and faunal elements (and what major groups of organisms are
lacking, such as reptiles/amphibians in subarctic/arctic)
Certain aspects to keep in mind as we go through:
Epiphytes and epiphytic growth (why do some plants do this, which ecosystems have this
type of growth and why), wet/dry seasons and occurrence of drought, parallel evolution of
organisms with similar forms in similar habitats in different places in the world (eg., cacti
and certain euphorbs in New World versus African deserts, respectively).
Types of biomes: (this is not an exhaustive list, though all major biomes are listed here)
What distinguishes tropical biomes from temperate (or subarctic/arctic) types?
Rain Forest, Dry Forest, Savanna (not listed are higher elevation biomes, which I
WILL introduce you to and expect you to know something about)
Both tropical and temperate deserts (and arctic tundra is, in many respects, a desert)
Mediterranean (woodlands/shrub-, scrublands), Grassland, Forest (includes a
variety of subsets: deciduous, mixed, and even rain)
The Subarctic and Arctic:
Boreal Forest (Taiga), Tundra
Be aware that, in general, with higher latitude (tropics to the arctic) comes cooler temps.;
similar temperature gradients occur, with shifts in biome composition, with higher altitude. We
will, for example, talk about alpine taiga and tundra (in essence, alpine islands)
Islands: though we typically think of
a piece of land surrounded by water, mountaintops, in
essence, are islands "in the sky", and even ponds and lakes are actually islands for the aquatic
organisms that inhabit them.
Chapter 3: Life in Water
The Hydrologic Cycle -- evaporation-precipitation; would happen without organisms.
Organisms, in essence, temporarily but continuously insert themselves into the cycle.
Turnover time: amount of time for a particular reservoir (body) of water to be renewed.
Rivers can be as fast as 2 weeks, and even the entire 1.3 billion km3 of water in the
oceans is turned over in 3100 years.
Aquatic Life Zones "Biomes" -- again, for each you should know basic characteristics:
distribution on the planet, typical floral and faunal elements.
Major influencing factors: temperature (including extremes), salinity, light, oxygen, nutrient
availability (Note: moisture/precipitation NOT in the list -- we are, after all, talking about
aquatic ecosystems!! Moisture only becomes important when the water is gone or almost
gone, though the original source of the water is precipitation, and continuously supplies the
water to the aquatic ecosystems to keep them in balance.)
Types (not an exhaustive list):
Marine ("Salt Water"): currents play a major role in influencing temperature distribution
Oceanic: divided into several zones
Pelagic -- open waters (not including interactions with the ocean floor)
includes epipelagic, mesopelagic, bathypelagic, abyssal, hadal
Benthic -- bottom habitat
deep ocean bottom: thermal vent communities, w/ chemosynthesis in
bacteria as the producers for this community
Neritic (continental shelf): from shore to about 200m deep
Intertidal (littoral): the shoreline -- the epitome of the extreme ecotone
Kelp & Coral -- in the neritic zone
Kelp tend to be in temperate coastal waters; coral in tropical coastal water
Coral communities rival tropical rain forest in diversity (and productivity)
The Intertidal: the most extreme ecotone
low, high, spring, neap tides; forces driving tides -- sun, moon and local geography
Ranges from: supratidal fringe to subtidal zone; zonation of species obvious.
Height of tides and waves impact structure/diversity
Diversity influenced by rock (more diverse) or sand (less) diverse
Tide pools can experience significant extremes of temperature and salinity
Estuaries: where rivers meet the sea; extreme salinity changes, technically part of
Temperate salt marshes and tropical mangrove forests
Rivers and Streams:
Length/width, speed/direction of flow; varies depending on availability of ground-
Maximum/mininum flow (active vs. wetted channels); flooding.
Stratification -- riparian area; water column, benthic/hyporheic/phreatic zones
Littoral zone; Limnetic zone with epi-/meta-/hypolimnion; benthic zone
Integrity (health) of aquatic systems: assessment is done by species richness and using