44.2 Biogeography

• The biosphere extends into the atmosphere and into the depths of the oceans.

• When compared to the known universe, the biosphere occupies only a minute of space.
• The types of organisms found in different parts of the biosphere are influenced by many abiotic forces.

• latitude and elevation are the most important factors in determining abiotic factors.
• The composition of plant and animal communities changes as these abiotic factors change.
• If you were to begin a journey at the equator and walk north, you would notice gradual changes in plant communities.
• At the beginning of your journey, you would see tropical wet forests with broad-leaved evergreen trees, which are characteristic of plant communities found near the equator.
• As you traveled north, you would see these broad-leaved evergreen plants grow into dry forests with scattered trees.
• You would start to notice temperature and humidity changes.
• The deserts are characterized by low precipitation and high insolation.

• You would see that deserts are replaced by grassland or prairies further north.
• The grasslands are replaced by forests.
• The subarctic is home to the boreal forests and taiga.
• The most northern latitude is where the tundra is found.
• The trek north shows gradual changes in both climate and the types of organisms that have adapted to environmental factors found at different latitudes.
• Due to abiotic factors such as jet streams, the Gulf Stream and ocean currents, different ecosystems exist at the same latitude.
• If you were to hike up a mountain, you would see the same changes in the vegetation as you move higher up.

• Ecologists study the distribution of species.
• The Venus flytrap is endemic to a small area in North and South Carolina.
• The raccoon is native to most of North and Central America and is one of the other species that live in a wide variety of geographic areas.

• The emergence of evolutionary thinking in the 18th century was linked to the emergence of early studies of biogeography.
• Some of the most unique plants and animals can be found in regions that have been separated for millions of years.
• Australia has between 600,000 and 700,000 species of plants and animals, according to biologists.
• Approximately 1/3 of living plant and mammal species are endemic to Australia.

• Australia has many endemic species.
• A pouched mammal is the wallaby, a medium-sized member of the kangaroo family.
• The echidna is an egg-laying mammal.

• Sometimes ecologists can find unique patterns of distribution.
• Despite being tropical, Hawaii has no native land species of lizards, snakes, or Amphibians, only a few native butterflies, and only one native mammal, the hoary bat.
• One example is that of most of Newguinea, which lacks placental mammals.

• This video shows a platypus swimming in its natural habitat in New South Wales, Australia.

• Like animals, plants can be endemic or generalist, and they can be found in many regions.
• Large numbers of endemic plant species can be found in isolated land mass.
• Some of the plants are in danger.
• The forest gardenia is endemic to Hawaii and only 15-20 trees are thought to exist.

• The forest gardenia is a small tree with flowers.
• It is only found in five of the Hawaiian Islands.

• The sun's energy is captured by plants.
• Solar energy is converted into chemical energy by organisms.
• Light availability can affect the evolution of adaptation in photosynthesizers.

• Understory plants can successfully capture available light that passes through the canopy.
• The rapid growth of spring ephemeral plants such as the spring beauty is an adaptation.
• Early in the season before the trees in the canopy develop leaves, these spring flowers achieve much of their growth and finish their life cycle.

• The spring beauty is an ephemeral plant that flowers early in the spring to avoid competing with larger forest trees for sunlight.
• Light cannot reach the zone at the bottom of a lake, pond, or ocean because it is absorbed by the water column.
• A number of adaptions have evolved that allow living things to survive without light.
• Plants grow near the surface of the water.
• Water lilies cannot survive without light.
• In environments with no light for photosynthesis, somebacteria extract energy from chemicals.

• The availability of food in the ocean is an important part of energy.
• Many organisms sink to the bottom of the ocean when they die in the open water; when this occurs, the energy found in that living organisms is sequestered for some time unless ocean upwelling occurs.
• As the wind pushes ocean waters offshore, water from the bottom of the ocean moves up to replace the water.
• Living organisms can reuse the nutrients that were once contained in dead organisms.

• Ocean upwelling recycles resources in the ocean.
• The water from the ocean bottom moves to the surface when wind pushes offshore.

• In the spring and fall, the bottom of the lakes are recycled.

• Many lakes in the north are frozen in the wintertime.
• The water under the ice is slightly warmer than the water at the bottom of the lake.
• The deepest water is also the densest.
• The deepest water is oxygen-poor because the organic material at the bottom of the lake uses up available oxygen that cannot be replaced by means of oxygen dispersal into the surface of the water.

• The spring and fall turnovers are important processes in freshwater lakes that move the oxygen and nitrogen at the bottom of deep lakes to the top.
• Water has a maximum density of 4 degrees.

• The water becomes heavier and sinks to the bottom when the temperature of the surface water increases.
• The water at the bottom of the lake is displaced by the heavier and denser surface water.
• The lake bottom is brought along with the water as it rises to the top.
• The turnover is called the spring.

• As the air temperature drops in the fall, the water in the lake becomes cold enough to cause fall turnover as the heavy cold water sinks.
• The water at the surface of the lake is oxygen-rich, while the water at the bottom is not.
• During the winter, the oxygen at the bottom of the lake is used by organisms that need oxygen, such as fish.
• It is important to note that the relative transparency of ice allows the penetration of the shorter wavelength of visible light so that photosynthesis can continue.

• The density and state of water are affected by temperature.
• Few living things can survive at temperatures below 0 degC because of metabolic constraints.

• It is rare for living things to survive at temperatures greater than 45 degrees Centigrade; this is a reflection of evolutionary response to typical temperatures near the Earth's surface.
• Enzymes are the most efficient within a narrow range of temperatures.
• The organisms must either maintain an internal temperature or live in an environment that will keep the body within a temperature range that supports metabolism.
• Some animals are able to survive temperature fluctuations, such as in the case of a reptilian torpor.
• Some Archaeabacteria have evolved to tolerate extremely hot temperatures like those found in the geysers within the park.
• Such organisms thrive in extreme environments.

• The distribution of living things can be affected by the temperature of the air and water.
• In order to survive, animals have to respond to temperature fluctuations.
• Problems related to temperature, locating food, and finding a mate are solved by migration.
• The Arctic Tern makes a 40,000 km round-trip flight between its feeding grounds in the southern hemisphere and its breeding grounds in the north each year.
• In the warmer months, monarch butterflies live in the eastern and western United States, where they build up enormous populations, and migrate to areas around Michoacan, Mexico as well as areas along the Pacific Coast and the southern United States in the wintertime.
• Some mammals migrate.
• Reindeer travel 5,000 km to find food.
• Amphibians and reptiles don't have the ability to travel.
• Not all animals can migrate: migration carries risk and comes with a high-energy cost.

• Some animals are able to survive hostile temperatures.
• In a state known as torpor, animals enter a state in which their metabolism is lowered.
• The animal can wait until its environment supports its survival.
• The wood frog has a chemical in its cells that keeps them from freezing and bursting.

• Water is important for cellular processes.
• Terrestrial organisms have evolved many ways to retain water.

• Plants have a number of interesting features on their leaves, such as leaf hairs and a waxy cuticle, that help to decrease the rate of water loss.

• The freshwater organisms are constantly in danger of having water rush into their cells because of osmosis.
• In freshwater environments, many organisms have evolved to ensure that their solute concentrations remain within appropriate levels.
• The diluting excretion of urine is an adaptation.

• Marine organisms are in danger of losing water to the environment because they are surrounded by water with a higher solute concentration than the organisms.
• Water and solutes can be retained and released into the environment by these organisms.
• Marine iguanas sneeze out water that is high in salt in order to maintain solute concentrations within an acceptable range while swimming in the ocean and eating marine plants.

• Plants get the water they need from the soil through the roots.

• The distribution of plants is dependent on the soil structure, soil pH, and soil nutrient content.
• Animals get their nutrition from the food they eat.
• Distribution of what they eat is related to animal distributions.
• Some animals follow their food resources through the environment.

• Oxygen is important in aquatic environments.
• Oxygen comes from the air that animals breathe.
• Oxygen availability can be an issue for organisms living at high altitudes.
• The concentration of dissolved oxygen is related to water temperature and the speed at which the water moves.
• Cold water has more dissolved oxygen than warm water.
• Salt, currents, and tidal changes can be important abiotic factors.

• The rate of transpiration and convective heat loss from the surface of organisms can be influenced by wind.
• The physical force of wind is important because it can move soil, water, or other abiotic factors.

• Fire can be an important agent of change in the environment.
• Some organisms need the high heat associated with fire to complete a part of their life cycle.
• The jack pine requires heat from fire to open its seed cones.
• Nitrogen is added to the soil through the burning of pine needles.

• The mature cones of the jack pine are only open during a forest fire.
• A fire is likely to kill most vegetation, so a seedling that grows after a fire is more likely to get enough sunlight than one that grows under normal conditions.
• Net primary productivity is the amount of organic matter available as food, and it is influenced by temperature and humidity.
• This means that a large percentage of underground plant material is not included in the measurement.
• Net primary productivity is an important variable.