Mr. Bouyer

Day 1 | Day 2 - 3 | Lab | Reading Assignment

Use communities to describe ecological succession. Describe the energy flow in ecosystems. Compare terrestrial ecosystems based on temperature and moisture. Compare aquatic ecosystems based on temperature and light. Describe the affects of disturbances on ecosystems.

Animal Identification Assignment.

What two abiotic factors determine the composition of a community?

The total of all species populations inhabiting the same area forms a community. Communities interact with their physical and chemical environments to form ecosystems. Ecosystems are very complex and difficult to study because of all the uncontrollable environmental variables and interactions. The study of ecosystems requires a broad knowledge of chemistry, botany, zoology, agronomy, geology, and meteorology.

Communities:

A community can be any natural biotic unit, regardless of size. Aquatic communities are named according to the features of the water and terrestrial communities are usually named according to the dominant plant species they support. Precipitaion and latitude are two physical factors that determine the composition of a community. Community biomass generally declines as latitude increases or moisture decreases.

The interactions of mountains and prevailing winds have a profound effect on community distribution. An air mass cools rising over a mountain, causing precipitation on the windward side. On the lee side, the descending air warms and picks up moisture forming a rain shadow.

Ecological succession is a progression of communities appearing on a site over time. Each of these communities has its own dominant plant species and animals that depend on them. Young communities quickly accumulate biomass causing rapid change. Climax communities are relatively stable and will remain relatively unchanged for hundreds of years, if not disturbed.

• Primary succession: occurs on sites where no community has previously existed. This would include sand dunes, new volcanic islands, or any place where there is no soil. Primary succession is a slow process because the physical environment must be modified by the community to produce soil.
• Secondary succession: occurs in disturbed areas that were formerly occupied by communities. Since the soil is already established, succession is relatively rapid.
• Pioneering plants: the first plants to grow in a disturbed area. They are usually short, fast growing plants that produce large numbers of seeds.
  • Soil building is primarily a biological process as dead organic matter increases the amounts of nutrients in the soil. As the depth and richness of the soil increases, larger plants are able to grow.

Ecosystems:

The most important thing driving an ecosystem is energy. Ecosystems are open energy systems. This means energy flows through them rather than cycling within them like a closed energy system. Almost all ecosystems are driven by solar energy. Plants capture this energy and turn it into chemical energy through the process of photosynthesis. But energy is continually leaving the ecosystem in the form of heat. The second law of thermodynamics states that there is a universal trend toward heat loss. Living things are not capable of capturing and using heat energy. Because of this, all energy produced by plants and animals is eventually lost.

Forms of energy in ecosystems:

1. Solar energy - only about 1% of the solar energy that enters the earth's atmosphere is converted to chemical energy by photosynthesis.
2. Chemical energy - available as the potential energy of chemical bonds in organic molecules.
3. Kinetic energy - energy produced by the motion of both biotic and abiotic parts of the ecosystem.
4. Heat energy - heat energy flows downhill, that is from high heat areas to low heat areas.

Energy flow is best measured by ecosystem productivity, the rate of assimilation of chemical energy as organic matter. Assimilated organic matter can be measured as biomass, the weight of living matter in a particular area. Primary productivity is the rate at which energy is fixed in photosynthesis by autotrophic organisms. Secondary productivity is the rate at which heterotrophic organisms store energy from food.

Trophic (feeding) relationships within a community or ecosystem:

• Primary producers - autotrophs that produce organic energy.
• Primary consumers - heterotrophs (herbivores) that consume autotrophs.
• Secondary consumers - heterotrophs (carnivores) that consume herbivores.
• Tertiary and quanternary consumers - carnivores that eat other carnivores.
• Decomposers - organisms that break down dead organic matter into smaller organic materials and ultimately into inorganic matter. While bacteria and fungi are the main decomposers, animals like earthworms, nematodes, millipedes, and aquatic insect larvae are important.

Biogeochemical cycles:

Unlike energy, chemical materials called nutrients move in cycles within an ecosystem. These cycles are homeostatic (self-regulating) systems. Under normal conditions, if one part of the cycle becomes overloaded, another part of the cycle will become more or less active to relieve the stress in the cycle. Both energy flow and nutrient cycling are important factors determining the success of an ecosystem. Biogeochemical cycles can be divided into two main groups:

1. Gaseous cycles: involve elements that have their major reservoir in the atmosphere.
   • Nitrogen cycle: the most complex of all biogeochemical cycles.
2. Sedimentary cycles: involve elements that have their major reservoir in the lithosphere, the earth's crust.
   • Phosphorus cycle:
   • Hydrologic (water) cycle:

Major terrestrial ecosystems:

Terrestrial biomes are determined by temperature and moisture.

• Tundra
• Taiga
• Temperate Deciduous Forest
• Tropical Rain Forest
• Grassland
• Chaparral
• Desert

Major aquatic ecosystems:

Aquatic biomes are determined by temperature and light.

• Freshwater ecosystems:
  • Lentic ecosystems - composed of standing water like lakes, ponds, marshes, and swamps.
  • Lotic ecosystems - composed of flowing water like rivers and streams.
• Estuarine ecosystems: zones of transition where freshwater rivers enter the ocean. There is a wide range of salinity within estuaries.
• Marine ecosystems: While oceans cover about 70% of the earth's surface, much of this area is relatively unproductive biologically. The ocean zones are marked by differences in depth and light penetration.
  • Littoral zone: the highly variable intertidal area. This zone is inhabited by plants and animals that are adapted to being alternately exposed to water and air as the tide moves in and out.
  • Pelagic zone: the open ocean.
    • Neritic zone - the highly productive areas lying over continental shelves.
    • Oceanic zone - the less productive areas lying over deep.
      • Euphotic zone - upper, well lighted area supporting photosynthetic algae.
      • Dysphotic zone - a twilight area that does not support alga growth.
      • Aphotic zone - a zone of permanently dark water.
  • Benthic zone: the ocean floor.
    • Sublittoral zone - a relatively shallow continental shelf. This area area is highly productive.
    • Bathyal zone - from the continental shelf down to about 4000 meters.
    • Abyssal zone - a deep-sea plane from about 4000 meters down to about 6000 meters.
    • Hadal zone - the deepest ocean trenches down to 10,000 meters.

Disturbance of ecosystems:

Ecosystems are not static; they respond to environmental disturbances in a variety of ways. Through evolutionary changes, species within an ecosystem can adapt over a long period of time. Through successional changes, communities within an ecosystem can adapt over a relatively short period of time.

• Ecosystem resistance - the capacity of an ecosystem to remain relatively unchanged when confronted by a disturbance.
• Ecosystem resilience - the speed at which an ecosystem returns to its former state following a disturbance.

Portfolio Assignment 041:
Scoring criteria

1. Describe a practical way to determine the biomass of a 500 acre wheat field.
2. Write descriptions for each of the major terrestrial biomes listed on this page.
3. There are two types of aquatic biomes. Explain the differences in the two.
4. What determines the different zones in the ocean?
5. How deep is the deepest part of the ocean?

 

In-Class Assignment 041b:
This assignment must be completed by the end of class today to receive credit.

1. Make one PowerPoint slide for each of the following aquatic biomes/zones.
   Use this type of slide.
   • Lentic
   • Lotic
   • Estuary
   • Littoral
   • Neritic
   • Hadal
   
    
2. Place a picture representing the biome on the left.
3. Type the name of the biome in the Title space on the slide.
4. Type the following information on the right side of the side.
   • Characteristics of the water
   • Significant plants found
   • Significant animals found
   • Your name and date

Zoology Class

Precipitation and latitude are the two abiotic factors determining the composition of a community.
Latitude generally controls temperature and length of daylight hours. Both of these are important to plants, therefore also controlling what animals live in an area.