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A.P. Biology

Chapter 46

  1. Ecology - study of the biotic and abiotic factors and their interactions.
    1. Organismal ecology - studies how living organisms interact with and adapt to environment.
    2. Population ecology - studies the factors that affect and control population sizes.
    3. Community ecology - studies the interactions between organisms and populations in an area (predation, competition).
    4. Ecosystem - community ecology with the abiotic factors added in.
  2. Terrestrial Biomes -
    1. SAVANNA- savannas are large grasslands with scattered individual trees. Most savannas cover tropical and subtropical areas of central South America, central and southern Africa, and parts of Australia. Savannas generally have three seasons: cool and dry, hot and dry, and warm and wet. They normally occur in this order. Most soils of the savanna are porous soils, which cause quick drainage of water. Porous soils have only one layer of rich, partially decomposed organic material called humus. The savanna has many different species. There are few deciduous trees and shrubs scattered across the open landscape, but because of frequent fires and grazing mammals the seedlings are destroyed before they ever become established well.
      1. FORBS- forbs are the dominant vegetation of the savanna. A forb is a small, broad-leafed plant that grows with grasses. During the warm and wet season they produce showy flowers to attract insects for pollination.
      2. TROPICAL SAVANNA- tropical savannas are home to some of the world's large herbivores, such as the giraffe, zebra, antelope, buffalo, and kangaroo.
      3. North American Savanna - the savanna is also home to many smaller animals that burrow in the ground like mice, moles, gophers, ground squirrels, snakes, worms, and arthropods. Most animals are mostly active during the rainy season and are also nocturnal. During the dry seasons animals are either dormant or subsist on seeds or dead plants. Most large herbivores migrate to greener pastures and watering holes during the really dry seasons. The term savanna is also used to the areas where the forest and the grasslands meet. You can find this in North America on a band running roughly from Minnesota to east Texas.
    2. DESERT- the desert is the driest of all the biomes. Deserts receive less than 30-cm of rain per year. The soil surface temperature can reach up to 600 C.
      1. HOT DESERTS- hot deserts are found in the southwest United States, the West Coast of South America, North Africa and in the Middle East. The Atacama in Chile, the Sahara in Africa, and parts of Australia are the driest deserts in the world, receiving less than 2 cm of rain per year.
      2. COLD DESERTS- cold deserts are found west of the Rocky Mountains, eastern Argentina, central Asia, and Antarctica. These are classified deserts because of the sparse rain percentage received each year, even though they are very cold.
      3. Inhabitants- Vegetation in deserts is very sparse and in the driest deserts have hardly any. The plants consist of drought-resistance shrubs and cacti or other plants that store water in their tissues. An example of these plants is the Saguaro cacti, which has a "pleated" structure that stretches to absorb as much water as possible during the wet periods. The animal life in deserts is sparse too. The main animals here are seed eating rodents and birds that are prey for larger reptiles. These animals have evolved the most to adapt to their environment.
    3. CHAPARRAL (scrublands)- chaparral is the coastal areas between 30 and 40 degrees latitude. It is characterized by its mild and rainy winters and long, hot, dry summers. The chaparral vegetation is described as stands of dense, spiny shrubs with tough evergreen leaves. These areas are found in the Mediterranean region, coastlines of California, Chile, southwestern Africa, and southwestern Australia. This has adapted to and is maintained by periodical fires. They have adapted to these fires by starting to store food resources in their fire-resistant root crowns. This enables them to re-sprout quickly and use nutrients produced by the fire to grow more. Animals that characterize these areas are deer, fruit-eating birds, seed-eating rodents, snakes, and lizards.
    4. TEMPERATE GRASSLAND- temperate grasslands share characteristics of the tropical savanna, but are sometimes located in regions of relatively cold winter temperatures. Areas of these conditions are the Veldts of South Africa, the Putza of Hungary, the Pampas of Argentina and Uraguay, the Steppes of the former Soviet Union, and the plains and prairies of central North America. The soils of the grasslands are very thick and nutrient rich, which helps the roots of perennial grasses grow deeper. Large grazing mammals such as the bison, gazelle, zebra, rhinoceros, and antelopes graze the grasslands preventing woody shrubs from popping up. Grasslands expanded greatly in size after the retreat of glaciers in the last ice age.
    5. TEMPERATE DECIDUOUS FOREST- temperate deciduous forest are characterized by large, broad-leafed deciduous trees. These areas also have a lot of moisture to support the growth of these trees. Temperate forests are found along the eastern United States, middle Europe, and eastern Asia. Temperate forest normally has very cold winters and very hot summers. The deciduous trees of temperate forest have a distinct annual rhythm where trees shed their leaves during winter then grow them back in spring. They are able to do this because of the nutrient rich soil. Because of the nutrient rich soil there are many different species of trees like oak, birch, and hickory. This variety of trees also allows for a wide variety of animal species also, but humans are limiting this large variety by cutting down trees.
    6. TAIGA (coniferous or boreal forest)- the taiga areas are located in northern North America, Europe, and Asia. It is also found at high elevations in temperate latitudes. The taiga has long, cold winters and short, wet summers. The summers have very long days(up to 18 hours of daylight) and the precipitation received is mostly snow. The dominant species of trees is the coniferous tree. They often stand so dense that little undergrowth is present. The heavy snow in winter helps hold in ground heat so that little mice and other small mammals could survive underground. Animals of the taiga consist mostly of seedeaters and herbivore insects. These animals are prey for larger animals like grizzly bears, wolves, lynxes, and wolverines.
    7. TUNDRA-
      1. ARTIC TUNDRA- this is the northernmost limits of plant growth. The arctic tundra encircles the North Pole and extends southward to the taiga. The arctic tundra's climate is often very cold. In the winter there is little daylight.
        1. PERMAFROST- permafrost is a condition in the tundra where the underlying subsoil remains frozen causing little growth of plants. Perennial shrubs, sedges, grasses, and mosses grow in rapid growth during the summer months. Most animals of the tundra withstand the cold by living in burrows or having large winter coats. Some animals in the arctic tundra include the large musk oxen, reindeer, hares, arctic fox, and polar bears.
      2. ALPINE TUNDRA- alpine tundras are similar communities that occur at really high altitudes where trees can no longer grow. It can occur in all places if the altitude is high enough.
      3. Inhabitants - some differences between the alpine and arctic tundra are some of the vegetation(they have around 40% in common) and animals, alpine tundras have at least 12 hours of daylight per day, and alpine tundras have a steady growth rate instead of splurging at one time.
  3. Fresh Water Biomes -
    1. Lakes & ponds - because these have slower moving water, there is less mixing and zones are created.
      1. Zones based on light -
        1. Photic zone - upper area where there is enough light for photosynthesis.
        2. Aphotic zone - lower area where very little light reaches.
      2. Zones based on temperature - usually the shallower areas are warmer because they are heated by the sun. These zones are separated by a zone of rapid temperature change called a thermocline.
      3. Zones based on the organisms - these are usually affected by the amount of light and temperature.
        1. Littoral zone - shallows close to shore. Receives plenty of light and heat. Rooted and floating plants and algae live in this zone along with some snails, amphibians, clams, insect larvae crustaceans, etc.
        2. Limnetic zone - photic zone away from shore. Inhabited by phytoplankton (mostly algae and cyanobacteria). This provides food for zooplankton (mostly rotifers & smaller crustaceans), which provide food for larger animals, such as fish, turtles, etc.

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        3. Profundal zone - aphotic area below the limnetic zone. This area has little light and is usually cooler than the upper areas. Organisms from the limnetic zone die and sink into this zone. Microbes that live here break down this detritus and use up the oxygen.
      4. Types of lakes - classified by production of organic matter, which is often determined by size and depth.
        1. Oligotrophic - usually deeper, with less phytoplankton in the limnetic zone. Because of the lower numbers of phytoplankton, the water is clearer and light penetrates further. Also, the less phytoplankton means less detritus and more oxygen.
        2. Eutrophic - shallower with higher amounts of nutrients. The higher amounts of phytoplankton in the limnetic zone means the water is cloudier and there is less oxygen in the profundal zone. Sewage and runoff from farms can add to the amount of nutrients in oligotrophic lakes causing them to become eutrophic. This can deplete the amount of oxygen, which means that organisms in the profundal zones would die off. This called cultural eutrophication.
    2. Streams & rivers - moving water that is continuously being mixed keeps the water oxygenated and prevents phytoplankton from growing. An alga that attaches to the bottom is usually the basis of the food chain. This can feed small crustaceans, insect larvae, etc., which in turn feed fish. These animals usually stay in slower water or behind rocks. Also, there are different organisms depending on the location along the stream or river. They can transport nutrients and plants great distances.
  4. Marine biomes - salt water or salt and fresh mixed. There are several different zones in the oceans. There are photic and aphotic zones similar to fresh water. There are also areas that are dependent on their distance from shore. The zone closer to shore where the continental shelf is located is the neritic zone and farther out is the oceanic zone. The area from the open ocean floor to the surface is the pelagic zone (no matter how deep). The benthic zone is the sea floor from the beach out. The abyssal zone is the benthic zone at deeper parts of the ocean.

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    1. Estuaries - fresh water meets salt water. These areas are usually very productive biologically. Grasses, algae and phytoplankton are usually the major producers and feed small crustaceans and mollusks. These areas are also important to many amphibians for food and aquatic birds for food and nesting.
    2. Intertidal zones - rocky intertidal zones often show the most diversity. The uppermost parts are under water for the shortest amount of time and have evolved ways of dealing with the lack of water. In some areas it is easy to determine the different parts of the intertidal zone by the organisms that live in the different parts. The sandy intertidal zones show less diversity because they are usually flatter and the moving tides can erode and change them easier.
    3. Oceanic pelagic zone - As in lakes, the phytoplankton in the photic zone dies and sinks to the aphotic zone, but ocean currents continually mix so there is oxygen at all depths. The phytoplankton in this area accounts for about half of the photosynthesis on Earth. Zooplankton, jellyfish, crustaceans (krill, shrimp, etc.) and also live in this zone because they feed on the phytoplankton. The above ride the currents for movement, but there are also free swimmers in this zone called nekton (aquatic mammals, squid, fish, etc.). This is also an important area for sea birds, which may subsist exclusively on the organisms in the upper areas of this zone.
    4. Benthos - communities on the ocean floor of the neritic and pelagic zones. This is mostly sediment of decayed organisms or worn down rocks. The organisms in this area differ greatly depending on the depth and latitude. Organisms do live in the abyssal zone (the oceanic benthic area) and have adapted to the colder temperature (~ 3ƒ C), the high pressures and the lack of light. Chemoautotrophs have also adapted to areas around undersea volcanic vents that have very high temperatures, pressure and little to no oxygen.
  5. ENVIRONMENTAL DIVERSITY - Biosphere is a mosaic of habitats differing in factors such as temperature, rainfall and light.
    1. Important Abiotic Factors
      1. Temperature - reason for distribution of organisms cells rupture at 0*C, proteins denature at temp. of 45*C. Mammals and birds are major exception.
      2. Water - aquatic face problems with water balance. Terrestrial face constant threat of desiccation.
      3. Sunlight - especially important in plants. Every meter of water absorbs 45% of red light and 2% of blue. Better sense of time than temp.
      4. Wind - Can increase heat loss by evaporation and convection. Flagged appearance on plants.
      5. Rocks and Soil - Physical structure pH and composition. Decides where plants grow and the animals that feed on them.
      6. Periodic Disturbances - Fires, hurricanes, tornadoes and volcanic eruptions. Sometimes communities benefit and adapt.
    2. Climate and distribution of biomes
      1. Temperature, Water, Light and Wind are components of climate. You can see the impact of climate on a climograph.
      2. Certain annual temperatures and precipitation can support different forests.
    3. Global Climate Patterns
      1. Solar energy from sun. Half is absorbed by upper atmosphere before it reaches earth. The rest is absorbed by earth and the some is reflected out.
      2. Tropics - Region between 23.50 north latitude and 23.50 south - Little seasonal change - greater toward poles.
      3. Solar Radiation near the equator creates precipitation and winds.
      4. Lots of water in atmosphere creates tropical rain forest then at 300 latitude it absorbs moisture from land making deserts. At about 600latitude releases moisture which makes a taiga. No moisture makes arctic and Antarctic. (Very Cold) Cycles back.
    4. Local and seasonal effects on the climate.
      1. Proximity to bodies of water effect climate. Evaporation over ocean is greater. Example: North-facing side of mountain grows trees, South grows shrubs. Deserts usually leeward side of mountains.
      2. Water Mixing
      3. Microclimate - Under rocks and trees

 

  1. Responses of Organisms - Biomes and their ecological communities are composed of populations of individual organisms that are adapted to the physical environments in which they live.
  2. Natural selection has produced diverse adaptations to extremes of temp, light, and other abiotic factors, however, no organisms can survive the full range of environmental conditions present on Earth.
  3. The success of an organism at survival and reproduction reflects it’s overall tolerance to the entire set of environmental variables it confronts.
  4. Homeostasis and the Principle of Allocation
    1. Regulators - use behavioral and physiological mechanisms to achieve homeostasis (ex) in brine shrimp, which live at high but variable salt concentrations, the ability to maintain a stable internal salt concentration. by osmoregulation
    2. Conformers – allow conditions within their bodies to vary with external changes in these variables (ex) marine invertebrates live in environments where the salinity is very stable…if placed in water of varying salinity, they will lose/gain water to conform to the external environment
    3. Principle of allocation – each organism has a limited amount of energy that can be allocated for obtaining nutrients, escaping from predators, coping with the environmental fluctuations, growth, and reproduction
  1. Environmental Grain – used by ecologists to define the use of spatial variation by organisms of different size
    1. Coarse-grained environment – one in which environmental patches are so large that in individual organism can choose among patches
    2. Fine-grained environment – one in which patches are small relative to the size and activities of an organism and the organism may not even behave as though the patches exist
    3. Temporal Variation – can also be either coarse or fine grained…daily variations in factors are fine-grained whereas seasonal and longer term shifts in climate are coarse-grained
  1. Behavioral Responses
    1. Muscular reactions – shivering, etc.
    2. Move to a new location
    3. Burrowing
    4. Migrating - this is moving, but not permanently.
    5. Modifying their immediate environment (ex—honeybees collectively beating their wings)
  1. Physiological Responses (generally slower than behavioral)
    1. Regulation
    2. Homeostasis
    3. Acclimation = a shift of the performance curve in the direction of the environmental change
  1. Morphological Responses (responses that alter the form or internal anatomy of the body)
    1. in animals – (ex) mammals and birds grow a heavier coat of fur or feathers in winter
    2. in plants – (ex) in arrowleaf plant which can grow on land, completely submerged in water, or rooted in water with its upper leaves emerging above the surface
  1. Adaptation over evolutionary time - Behavioral, physiological and morphological adjustments are the responses of individuals operating on an ecological time scale, however, these responses occur within a framework of adaptations fashioned by natural selection acting over evolutionary time. Organisms locked by their adaptations into one type of environment may fail to survive if placed in a different environ., however, the absence of a species in a particular place does not necessarily imply that the species could not survive in that location