Abiotic Factors and Biomes Complete (Acts 1-3)


Properties of energy and matter combine to
make multiple habitats. Let’s look at two scenarios: one on land and one in the water,
and see how interaction between energy and matter helps structure where organisms might
live. On the surface of the earth, energy from the sun heats up the ground which then
transfers the heat to the surrounding air. This happens more at the equator because it
receives more direct sunlight. The warm air rises, and as it rises it picks up water vapor
that is evaporated from the surrounding area. When air rises in the troposphere, it gets
colder. And as air cools, it becomes less able to hold water because it becomes more
saturated, and the water starts to precipitate out. This precipitation occurs over the equator
and leads to the formation of rain forests. Rainforests are plant and animal communities
that are adapted to high levels of water. The rising air around the equator draws in
air from the northern and southern latitudes. This then pulls the cool air down, and sets
up these air cells or currents. When the air comes down it is dry from having dumped all
of its water that it previously had. So it picks up any water in the surrounding areas.
This removal of water causes the surrounding areas to be dry. That is why if you look at
a globe, most deserts occur at 30 degrees latitude because that is where the dry air
currents come down. Similar conditions can occur based on landscape features like mountains.
Large mountain ranges can create this effect on a smaller scale. As clouds are forced to
gain in altitude to go over a mountain range, they cool, lowering their saturation point.
The air loses its water on the side of the mountain, and as the air reaches the other
side, it is dry and picks up any of the available moisture. So on one side, you might find lush
greenery, and on the other side, dry arid conditions. Global differences in temperature,
such as the difference between seasons, is due to the angle of sunlight the planet receives.
Just like when you have a flashlight and shine it on a wall, the more perpendicular your
light is to the surface, the more intense the light. If you think about it, when perpendicular,
the energy of the light is concentrated on the smallest amount of surface area. When
on an angle, the energy is spread out over more surface area, and so is less intense.
Because of the curvature of the planet, as you change latitude, you change your angle
to the sun. This is affected by the tilt of the planet. Depending on where we are in our
orbit around the sun determines which part of the planet is most perpendicular, which
in turn creates seasons. So to sum up, the sun’s angle to the earth creates different
temperatures in different regions. The radiation from the sun also creates wind currents which
transport water across the globe. Temperature and precipitation alone are able to distinguish
between most biomes. These factors are very important in determining location of different
plants and animals. Let’s look at how energy and matter interact in aquatic biomes. Light
is not able to penetrate water as it does air. Even in pure water, the majority of light
is lost at depths around 25 meters. This sets up a vertical structure in water for light,
with the highest levels of energy at the surface to low or no energy at the bottom. Solar radiation
is also the major source for heat for aquatic systems. The diffusion of heat is similar
to light and is also structured vertically. The diffusion of heat can create a thermocline,
which is a layer in the water where the temperature will drop rapidly as depth increases. Another
structured abiotic component are nutrients. Most nutrients come from terrestrial systems:
either from weathering of minerals or the decomposition of terrestrial organisms. As
such, you can get a horizontal structure to aquatic habitats, where the most nutrients
are found along the coast, with diminishing amounts of nutrients as you get more removed.
The interaction between solar radiation and properties of matter, like air and water,
create complex habitats that help to create structure to the biological world that overlays
them. One way you might see the structure is by looking at the location of biomes. Biomes
are stereotypes of biological communities. Examples of biomes might be a desert or a
tropical rainforest. A desert in North America, such as the Mojave, might contain an organism
such as the cacti. And the African Sahara desert might contain Euphorbes. Although these
species look similar, they have different evolutionary paths. So they have become adapted
in similar ways, but they use different structures for the adaptation. In the Mojave, the cactus
has evolved needles from its leaves, whereas the Euphorb evolved needles from its stipules.
The Mojave and the Sahara are considered the same biome because even though they may contain
different species that are relatively unrelated, the types of species are similar life forms,
meaning they have similar types of adaptations and life histories. If you are interested
in comparing exact species, you might compare ecotones, which makes distinctions based
on species. A paper in 2004 by Woodward et
al. looked at creating a biome system based on tree species. The benefit of this is that
scientists could then use satellite information to see how biomes change over time in response
to global warming or other human or natural disturbances. One pattern the authors see
is the growth of grasses. They argue that grasses constitute a super biome because they
occur in almost all biomes and in some cases define the biome. Grasses benefit from disturbance
of a habitat because they can grow quickly to fill cleared land. Even though there is
evidence for the increase of grasses before humans, human disturbance has increased the
opportunities for grasses. An interesting side point made by the authors is that traditional
definitions of biomes can include additional information that confuses the issue. Remember
that biomes are types of plant or animal communities. But some definitions include geography or
climate. Biome names that include “tropical” which is a specific latitude region on the
globe, or “boreal” which means northern, are automatically telling you something about
the climate of that region. So if you have a “tropical” in your name, it means that you
are located near the equator and will probably have a warm climate, because climate and latitude
are linked. This can create a circular argument if you said that tropical rainforests are
located where they are because of the warm wet conditions present. Which would make sense.
You would be in essence saying warm wet climates are found in warm wet climates. Hmm, just
something for you to think about. The main point of this animation is that properties
of energy, such as reflectance and heat transfer, interact with the properties of matter like
density of liquids, buoyancy of warmer particles, to create an environment that is complex,
varying in temperature and light and moisture. It also sets up currents that move heat and
materials through an ecosystem. Other variables such as pH, nutrients, and oxygen levels,
help to create even more complexity. This complexity affects where organisms will be
found. For example, plants that need sunlight will only be found in depths of water that
allow light to penetrate. Therefore, when we see a distribution of plants and animals,
it may inform us of the underlying abiotic conditions of that area. It’s easy to see
how abiotic, or non-living components, affect organisms, but how do you think organisms
affect abiotic components?

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