Ecological Succession: Trends in Succession

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Ecological Succession Trends in Succession

• Unit 10, Part 1

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Section 1 Ecological Succession

• Although you probably havent thought about it,
  the shrubs, moss or grasses you see when walking
  along a sidewalk could be the beginnings of new,
  natural communities.
• If these areas were not altered by human
  activities, each would undergo a series of
  changes in which different species of organisms
  would appear, to be replaced later by others.
• Given enough time, each area would become a
  complex and stable community.

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Succession and its Causes

• The series of changes in a community is called
  ecological succession.
• The diversity of organisms living in each
  community today is not the same as it was in the
  past. Biotic and abiotic factors have changed
  over time.
• Some communities may be stable, having undergone
  changes over a long period of time, and others
  may not yet be stable and still have some
  changing to do.

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What Causes Ecological Succession?

• A major factor is the effect a particular set of
  organisms has on the physical environment.
• During succession, organisms alter their physical
  surroundings in a way that makes those
  surroundings more suitable for other kinds of
  organisms and less suitable for themselves. As a
  result, new organisms invade and the old
  organisms move out.

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Primary Succession

• Succession that begins in areas where there is no
  life is called primary succession.
• This stage begins with very tough organisms -
  those that can grow under adverse conditions.
• This is called the pioneer stage.

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Climax Community

• The stable stage in the development of a
  community is known as the climax community.
• The type of climax community that emerges in a
  given area depends on the interaction of all
  factors in the environment.
• Because it is stable and complex, a climax
  community tends to remain the same over a long
  period of time without further succession.

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Secondary Succession

• Succession often begins as a result of natural
  destruction, such as fire, volcano, or flooding,
  or by human interference.
• In either case, new succession begins when the
  dominant plants of a community are removed.
• If the land is left untended, secondary
  succession occurs.
• This happens more quickly than primary succession
  because soil is already formed and seeds may be
  present.

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Succession of Plants
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Trends in Succession

• Whether primary or secondary succession, both
  have common characteristics.
• At the beginning, small plants with short life
  cycles (such as grass) are present. These are
  later replaced with larger plants with longer
  life cycles (like trees). This traps more energy
  via photosynthesis, which increases the
  biodiversity over time.
• Food chains are short and simple at first, but
  increase in complexity as time goes on and more
  species are present.
• Recycling of wastes and nutrients also becomes
  more efficient.

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Ecological Succession Human Interaction

• Unit 10, Part 2

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Human Interaction

• Humans have obviously done a lot to change the
  ecosystems in which they live.
• Picture the journey across America. Some places
  are dense with people, building, and cars, while
  others seem untouched. Other places have been
  heavily traveled, while still more have only been
  walked by cattle, buffaloes, and deer.
• While we love the modern marvels we use daily,
  what is the price of all these changes weve made?

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Pollution and Pesticides

• Imagining that cross-country trip again, describe
  the difference between the air in California and
  the air in Iowa.
• How does the population density of humans affect
  this?
• What are some things we do to contribute to the
  pollution?
• What can we change to make it better?
• These are all questions we must ask in order to
  determine the solutions to the decline of our
  resources.

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Pollution

• Pollution is caused by many factors, almost all
  of which can be attributed to human activity.
• The burning of fossil fuels (e.g., gasoline and
  coal) to power our cars, the use of substances
  containing CFCs (chlorofluorocarbons), and the
  dumping of wastes into our water are all sources
  of pollution.

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The Problem With Pesticides

• Pesticides, while beneficial for farmers
  protecting their crops, also have a downside.
• First, theyre toxic chemicals. Releasing them
  into the air, the soil, and the water, exposes
  not only humans, but also countless other
  organisms to their dangers.
• Secondly, after awhile, most insects will develop
  a resistance to them, forcing us to create newer,
  better, and more harmful toxins.
• Is this ever a good thing?

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Are There Other Options?

• There are some non-chemical, natural alternatives
  to using pesticides.
• One would be to release natural predators to keep
  pest populations in check.
• Another would be to use the pests own
  biochemical characteristics against them.
• Other alternatives, called cultural controls,
  involve breeding plants that are resistant to
  pests, or that have their own defense mechanisms.

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The Consequences

• In recent years, more attention has been paid to
  the relationship between the population boom and
  the damage being done to our atmosphere.
• Space issues, resource availability, disease, and
  intraspecific competition are all factors that
  affect the human population.

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The Ozone Layer A Hole in the Sky

• As youve probably heard, there is a hole in what
  we call the ozone layer. Ozone is a chemical (O3
  to be exact) that serves many purposes to
  protect the Earth from space debris, to help
  control the temperature, and perhaps most
  importantly, to shield the earth from harmful
  ultraviolet radiation from the sun.
• So, whats the problem with the deterioration of
  the ozone layer?

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Acid Precipitation

• As we know, the abundance of factories and
  automobiles burning fossil fuels can wreak havoc
  on the atmosphere.
• One such problem with this is the acid (mostly
  sulfuric acid) that builds up when smoke gets
  trapped in the air.
• When it rains, snows, sleets, or hails, the water
  collects the acid and brings it down with it.
  This results in the deterioration of metals, the
  increased acidity of the soil, and a pH change of
  water sources.

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Global Warming

• Global warming and the greenhouse effect are
  both issues as the average temperature of the
  earth increases.
• The greenhouse effect occurs when gases are
  trapped in the atmosphere. These gases are
  heated by the sun, which makes our temperatures
  on earth even higher.
• How might this affect different plants and
  animals?

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Conservation of Resources

• Youre probably familiar with the symbol below,
  which means reduce, reuse, recycle.
• What are some ways we do this now?
• What are some ways we can do this in the future?

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Food, Fuels, and Forests

• We can increase food by practicing selective
  breeding to produce more grain per plant. We can
  also replace the plants we have cut down in
  another area.
• We can seek out alternative fuel sources, such as
  ethanol, nuclear energy and solar power to reduce
  the burning of fossil fuels.
• We can recycle paper products to keep from having
  to cut down more trees and destroying forests and
  the animals who live in them.
• Any other ideas?

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Is There Any Hope?

• Pollution, over-consumption, and an expanding
  human population are real and important problems
  facing the earth.
• With enough planning and cooperation, we can
  reverse some of the damage thats been done over
  time and ensure that theres a place for our
  grand-children to live.
• Scientists have been working on alternative
  energy sources, and more people are recycling.
  Together, these things should add years to the
  life of Earth.