CHAPTER 52: INTRODUCTION

What is Ecology?

Ecology is the scientific study of interactions between organisms and the environment, ranging from an organismal scale to a global scale. The word "ecology" originates from the Greek words oikos (home) and logos (to study).

General Review

Organism — The individuals in an environment.

Organismal ecology — Focuses on how an organism's structure, physiology, and (for animals) behavior allow it to face the challenges of its surroundings.

Population — Group of individuals of the same species living in the same area.

Population ecology — Examines changes in population size and investigates the cause.

Community — Group of populations in an area.

Community ecology — Looks at how interactions between species affect community structure.

Ecosystem —The community of living organisms in addition to the abiotic factors affecting them.

Ecosystem ecology — Emphasizes the flow and chemical cycling between forms of life and their environment.

Landsape/Seascape — A mosaic of connected ecosystems

Landscape ecology — Focuses on factors which control interactions of energy, materials, and organisms across a number of ecosystems.

Biosphere — All of the planet's ecosystems and landscapes. The biosphere encompasses all regions where life may exist on earth, and is the focus of global ecology.

Evolutionary time — Adaptations over many generations through natural selection.

Ecological time — Time frame where differences in the surival and reproduction of individuals lead to evolution.

Species transplant — Ecologists sometimes observe the results of intentinoal or accidental species transplants to learn more about range expansions. If a transplant is successful, then the potential range of a species is larger than its actual range.

Tropics — Regions between 23.5° N and 23.5° S in latitude. These areas are closest to the equator and recieve maximal heat and light.

Prominent Figure

Rachel Carson (1907-1964)

Published Silent Spring in 1962, which applied ecological data to environmental issues. Carson recognized the damage pesticides did to organisms that are helpful to the environment, and her efforts led to the U.S. ban on DDT.

Biotic Factors

Biotic factors (or biota) are all of the the living organisms in an environment. Movement of individuals away from their origin or an area of high population density is called dispersal. This contributes to the global distributions of species. Distributions can be affected by organism behavior, other biotic factors or abiotic factors.

Abiotic Factors

Temperature — Cells may rupture if the temperature drops below 0°C and many proteins denature when above 45°C

Water — The variation in water availablity and a species' ability to obtain and conserve water greatly affects its distribution

Salinity — Do to osmosis, most aquatic organisms are restricted to either freshwater or marine habitats.

Sunlight — Provides the energy that drives most ecosystems on earth. In aquatic habitats, every meter of water absorbs around 45% of red light and 2% of blue light passing through it.

Rocks/Soil — The acidity (pH), mineral composition, and physical sturcture of rocks and soil limit the distribution of plants and therefore animals.

Climate

Temperature, precipitation, sunlight, and wind are all major components of climate, the long-term average weather conditions in a particular region.

Macroclimate — Patterns of the global, regional, and local climate. The Earth's global climate patterns are mostly a result of solar energy and our planet's movement in space. Proximity to significant bodies of water and mountains create regional climate variations, as does altitude and latitude. Furthermore, the tilt of Earth's axis causes dramatic seasonal cycles in most parts of the world.

Microclimate — A small area where the climate is different from its surroundings. These fine patterns affect a small community. A microclimate may be warmer or cooler, wetter or drier, more shaded or more sunny, etc. when compared to the areas surrounding it. Forests, garden beds, fallen logs, and the leeward side of a hill are all examples of microclimates.

Notable Experiment

W. J. Fletcher tested the interaction between sea urcins and seaweed by using a "removal and addition" experiment.

BIOMES OF THE EARTH

Aquatic Biomes

The upper photic zone is where there is enough light for photosynthesis, while the lower aphotic zone is were little light penetrates.

The benthic zone is the bottom of any aquatic biome and is home to organisms which are collectively called the benthos. These species feed mainly on dead organic matter called detritus.

In the ocean, part of the benthic zone (from 2000-6000m below the surface) is called the abyssal zone.

A narrow layer of abrupt temperature change in oceans and many lakes is called a thermocline. Changing temperature causes a type of water mixing called turnover, which brings oxygenated water to the bottom and nutrient-rich water to the surface.

Lakes — Still bodies of water ranging vastly in size. Oligotrophic lakes are nutrient rich and generally oxygen-rich; eutrophic lakes are nutrient-rich but quite depleted of oxygen. This is due to either an abundance or lack of decomposable organic matter.

Rooted aquatic plants live in the shallow littoral zone whereas microorganisms inhibit the deep limnetic zone.

Wetlands — A habitat covered by water at least some of the time. There are basin wetlands (shallow basins), riverine wetlands, (banks of rivers)and fringe wetlands (coasts of large lakes and seas).

Streams/Rivers — Clear, cold, headwater streams join together to form warmer and more turbid rivers

Estuaries — Transition area between a river and the ocean. Seawater flows up the channel during rising tide and flows back down during the falling tide. Important breeding ground for many fish.

Intertidal Zones — Oxygen and nutrient levels are replenished with the return of the tide. High diversity and biomass of algae.

Oceanic Pelagic Zone — Vast section of open blue water, mixed by ocean currents. Covers around 70% of Earth's surface and has clear, oxygenated water but less nutrients than coastal regions of the ocean.

Coral Reefs — Both shallow and deep-sea coral reefs are built from CaCO3 skeletons of corals and harbor huge diversities of life. Corals require high oxygen levels. A typical reef begins as a fringing reef on a young, high island, then an offshore barrier reef and then finally a coral atoll as the old island submerges completely.

Marine Benthic Zone — Consists of the seafloor below the coastal neritic zone, and the offshore pelagic zone. Organisms adapt to constant cold and high water pressure in the abyssal zone.

Terrestrial Biomes

Ltitude affects climate and therefore also biome distribution. Biome patterns can also be modified by disturbances (a negative event such as storms, fires, human activity).

Climographs plot the temperature and precipitation of different regions, showing the impact of climate. Terrestrial biomes usually grade into each other via regions called ecotones, with no strict boundaries.

Vertical layering is of importance in terrestrial biomes due to the sizes of plants. For intance, forests have an upper canopy, a low tree layer, a shrub understory, ground plants, forest floor, and a root layer.

Tropical Forest — Found in equatorial and subequatorial regions. Includes tropical rain forest that recieve rain consistently (around 200-400cm annually) and tropical dry forests that recieve 150-200cm of rain annually with a 6-7 month dry period.

Desert — Precipitation is low and highly variable (<30cm per year). Deserts occur in the interior of continents or in bands near 30° N and 30° S in latitude.

Savanna — Found in equatorial and subequatorial regions, buck have only 30-50cm of rainfall annually in addition to a 8-9 month dry period. Warm temperatures year-round.

Chaparral — Occurs in midlatitude coastal regions on several continents. Mainly shrubs, small trees, and grasses which favor a rainy winter and long, dry summers.

Temperate Grassland — Dominated by grasses and forbs. Temperature ranges from -10°C in the winter to 30°C in the summer. Average annual precipitation is between 30-100cm although periodic droughts are normal.

Northern Coniferous Forest — The largest terrestrial biome: extends across northern Eurasia and North America in a broad band. Huge temperature range (from -50°C to over 20°C in Siberia). Annual rainfall is around 30-70cm, though portions close to the northern US. Pacific coast can recieve over 300cm of precipitation.

Temperate Broadleaf Forest — Hot, humid summers near 35°C and cool winters around 0°C. Between 70-200cm of precipitation falls annually, with some regions recieving snow in the winter.

Tundra — Covers the expanse of the Arctic with winters being long and cold (averageing at around -30°C). Permafrost restricts te growth of plant roots and thus large plants cannot survive. High winds and low temperatures can create similar environments called alpine tundra at the top of very high mountains.