Ecology is the study of the distribution and abundance of organisms.
Biosphere: The area of the earth inhabited by life. It contains all the earth's ecosystems.
This is a thin layer of oceans, lakes, and streams. The land to the depth of a few meters and the atmosphere to an altitude of a few kilometers.
Organisms in these areas are acted upon by nonliving factors called abiotic factors.
Abiotic Factors:
1. Temperature: affects the organism's metabolism, The normal range is between 0 degrees and 50 degrees centigrade.
2. Water: adaptations for water homeostasis and conservation play a large role in determining a species' habitat range.
3. Light: The sun is the major energy source of nearly all ecosystems. Availability of light can determine habitat. In aquatic environments, water selectively reflects and absorbs certain wavelengths of light. As a result of this most photosynthesis occurs near the surface of the water. Animal and plant behavior is often sensitive to photo periods.
4. Soil: Physical structure, pH, and mineral composition of soil limit distribution of plants and have an effect on the animals that feed on them.
5. Wind: Increases the effects on temperature by increasing heat loss by evaporation and convection.
6. Natural Disasters: Fire, hurricanes, typhoons, volcanic eruptions can devastate biological communities.
Principle of Allocation: Each organism uses a small amount of its total energy for growth, reproducing, obtaining nutrients, escaping predators and coping with environmental changes.
Species living in stable environments lead a good life in a small area.
Species living in unstable environments lead a rough life over a wider range.
Terrestrial Biomes: Most often named for the predominant vegetation but each is also characterized by animals adapted to that particular environment.
a). biomes blend into each other without sharp boundaries.
b). May contain several communities represented in one biome.
c). Prevailing climate, particular temperature and rainfall, is most important factor in determining what kind of biome develops.
A climatograph plots temperature and rainfall and shows the impact of climate on the distribution of biomes.
A. Tropical Forest (rain forest): found near the equator, temp varies little from 25 degrees C. and day light varies from 12 hours by less than one hour. Lowlands receive very little rain fall, and develop thorn forests. Nearer the equator regions have distinct wet and dry seasons and tropical deciduous forests occur. Trees relief following heavy rains.
Near the equator, where rainfall is abundant , and the dry season lasts less than a few months is tropical rain forest. Contain more plant and animal species than any other community. Competition is strong for light, soil is poor due to the rapid recycling of nutrients. Animals are mostly tree dwellers.
B. Savanna: is a grassland with scattered individual trees. Found covering: Central South America, central and South Africa, and parts of Australia. Soil is generally porous with a thin humus layer. 3 distinct seasons: cool and dry; hot and dry, and warm and wet in that order. Frequent fires inhibit invasion of trees. Large herbivores ( giraffes, zebras) are commonly most active.
C. Desert: is characterized by low precipitation less than 30 cm / year, not by temperature: both cold and hot deserts exist. Hot deserts occur in S.W. USA, W. South America, North Africa, Middle East, Central Australia. Cold deserts occur: E. Argentina, central Asia, and west of the Rocky Mountains. Reptiles and seed eaters are common. Cacti and succulents are also common.
D. Chaparral: scrub land are regions of dense, spiny shrubs, with tough evergreen leaves found along coasts where cool ocean currents circulate offshore making mild rainy winters and long hot dry summers. Mediterranean , California coastline, Chile, S.W. Africa, and S.W. Australia. Deer, snakes, fruit eating birds are common.
E. Temperate Grasslands: similar to savanna but occur in cold regions. Veldts of S. Africa, the pusta of Hungary, pampas of Uruguay and Argentina, steppes of Russia, and the plains of the USA, are examples.
F. Temperate Forests: grow throughout the mid latitude regions that contain enough moisture to support large broad-leaved, deciduous trees. Occur in Eastern US, Middle Europe, and E. Asia. There is a 5-6 month growing season, very cold winters, and very hot summers. High precipitation and evenly distributed through out the year. Soil rich in nutrients.
G. Taiga: ( coniferous or boreal forest) is characterized by harsh winters and occasionally warm summers. N. America, Europe, Asia, and at high elevations in more temperate latitudes. Soil thin and acidic. It forms slowly.
H. Tundra: is the northern most limits of plant growth and at high altitudes plant forms are limits to shrubs and mat-like vegetation. Arctic Tundra: encircles the North Pole. Brief warm summers are marked with nearly 24 hours of sunlight. Permafrost, saturated soil prevent large plants from growing. Alpine Tundra: occurs at high elevations at all latitudes.
Aquatic Biomes:
78% of the earth's surface is covered with water. This aquatic environment is divided into two distinct areas: Marine and fresh water biomes. Without this enormous volume of water life on earth would be impossible. The ocean acts as a machine that drives the earth's weather patterns, helps regulate its many climates, servers as a reservoir for phytoplankton that generates 50% of the earth's oxygen, and absorbs large amounts of the earth's carbon dioxide. The structure of biomes are based upon the temperature of the water and its over all depth.
The depth of the water divides it into two distinct zones: The photic zone where abundant light is available for photosynthesis and the aphotic zone where minimal light is available.
The water temperature at different depths causes a layering effect to occur. The warmer water (less dense) will reside near the surface, while the more dense, colder, water will sink and remain near the bottom. The line of demarcation separating these different densities is called the thermocline. Certain times during, the year when the temperatures equalize, a mixing occurs bringing the nutrient rich lower water up to the top, The lower area of these biomes is called the benthos and contains a tremendous amount of dead organic material called detritus.
Marine Biome:
The marine biome is divided into distinct areas both horizontally and vertically. The horizontal divisions include (in order) the inter tidal zone, neritic zone, and oceanic zone. The vertical divisions are: the photic zone ( 0- 200 M), The aphotic zone (200-6,000 M). The benthic zone or sea floor, extends from the neritic zone to the lower depths of the ocean or abyssal zone. This zone contains a tremendous amount of nutrients from aquatic life that died and filtered down. The pelagic zone (all water) is a vertical designation ranging from the sea surface to the abyssal zone. Let's examine these areas more closely.
Intertidal Zone: This area is the beach with its sand and wave action though some are very rocky and void of sand. It is a harsh environment to live in and is under constant change. The tide plays an important role in how plants and animals survive in this area. Few plants are found in this area due to tidal action. Animals are mostly burrowers and filter feeders.
Neritic Zone: In tropical areas coral reefs are found in this area immediately after the intertidal zone. Since coral and algae form a mutualistic relationship by having the algae provide them with the by products of photosynthesis and they in turn provide them shelter and support.
Pelagic zone: This area is considered the open ocean. It is vast and contains very little nutrients. Phytoplankton are abundant here and produce most of the world's oxygen. Zooplankton (small arthropods, copopods, jellyfish, etc.) are also found here. In the deeper areas of the ocean animals called nekton are found. These squid, sea mammals, fish, and reptiles swim freely to find food.
Fresh Water Biome:
The freshwater biome is also divided horizontally and vertically. The horizontal divisions include the littoral zone which is closest to the shore of the lake. The limnetic zone encompasses the open area of the lake. Vertically you have the photic and aphotic zones and the benthic zone still makes up the lake floor. The deep vertical zone is called the profundal zone. Lakes are classified as Oligotrophic (deep and nutrient poor) and Eutrophic (shallower and rich in nutrients). Since there are no absolutes in ecology, a third lake type is recognized the mesotrophic lake. This is a middle ground between the two extremes.
Marshes, bogs and swamps are examples of this type of biome. These areas are either permanently flooded or periodically flooded. They contain aquatic plants and animals and are considered one of the nutrient rich biomes. Under federal and state law many of these areas are protected from commercial or private development.
These are areas where the marine and freshwater environments come in contact with each other. This biome is a very nutrient rich and productive environment. Algae, phytoplankton, and marsh grass are the major producers in this environment. Many invertebrates (clams,worms,and crabs) along with fish makes up its animal complement. This biome is under a tremendous stress from development and pollution.