Sustainability Of Ecosystems Class Notes

Sustainability of Ecosystems Class Notes

Ecosystem

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving (abiotic), physical components of the environment with which the organisms interact, such as air, soil, water and sunlight.

It refers to the interactions between the living things and between the living things and the non-living things.

Biotic vs. Abiotic

Biotic factors things that are living or were once living. Organisms which obtain nutrients, perform metabolism, produce energy, and can move about in the surroundings are biotic. They can grow, reproduce, maintain homeostasis, adapt, and evolve. For examples: plants, animals, bacteria, fungus, etc.

Abiotic factors are the parts of an ecosystem that are not living and never were living. For example: air, water, sunlight, rocks, sand, minerals, etc. Populations & Communities

A population is all the organisms that both belong to the same species and live in the same geographical area. They must also be able to mate with each other to produce viable offspring (their babies must be able to live and to reproduce as well). For examples: all the skunks in a forest, all the great white sharks in the Indian ocean, all the polar bears in the Arctic, all the sugar maples in a NS forest.

A community is all the difference types of populations that exist and interact with each other in a particular ecosystem. For example: in our forests, a community might consist of all the skunks, raccoons, white tailed deer, coyotes, squirrels, pine trees, spruce trees, maple trees, etc.

Biodiversity

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part related to climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions support fewer species.

The greater the biodiversity in a food web or ecosystem, the more stable and healthy the region will be.

Paradigm Shifts A paradigm is a framework for viewing reality. It is how we see/perceive our world.

Paradigms shift over time as a natural result of changing societal values or new scientific information. Think of a Paradigm Shift as a change from one way of thinking to another.

1. For instance, we once believed that the ocean could absorb unlimited amounts of pollutants and would always produce an unlimited amount of fish. We are now starting to rethink this. 2. We once thought that the atmosphere was so big that there would never be an impact from the pollutants that we released into the air. Now we are seeing the effects of acid rain and global warming.

Environmental Sustainability

In ecology, sustainability describes how biological systems remain diverse and productive over time. Long-lived and healthy wetlands and forests are examples of sustainable biological systems. We are talking about the ability to keep natural environments healthy, renewable and productive forever!

Healthy ecosystems and environments provide vital goods and services to humans and other organisms. There are two major ways of managing human impact on ecosystem services. One approach is environmental management; this approach is based largely on information gained from earth science, environmental science, and conservation biology. Another approach is management of consumption of resources, which is based largely on information gained from economics.

Food Chains FOOD CHAIN: A food chain is a step-by-step sequence that shows which organisms eat which other organisms.

 All energy comes from the SUN.  All food chains begin with organisms that produce their own food through the process of photosynthesis – PLANTS. Plants are also known as producers or autotrophs (auto meaning “self/same” and troph meaning “feeding”). Plants are always the 1st tropic (feeding) level.  Organisms that eat the plants hold the next level in the chain. These are known as HERBIVORES (animals that only eat plants) or OMNIVORES (animals that eat plants & animals). These are also known as 1st ORDER CONSUMERS.  Organisms that hold the next level (2nd ORDER CONSUMERS) are either CARNIVORES (meat eaters) or omnivores.  Some food chains could have 3rd, 4th, 5th, 6th, etc. ORDER CONSUMERS.  However, at some point there is an animal that has no PREDATORS (things that hunt for and eat it). These animals, at the top of the food chain are known as TOP CARNIVORES.

One food chain could look like the following:

Sometimes, animals eat the waste (including dead bodies of plants and animals) of other organisms. This waste is called DETRITUS. The organisms that eat the detritus are known as DECOMPOSERS or Detritivores. They play a very important role in the environment by returning the nutrients back to the soil so it can be recycled. Decomposers include bacteria, mushrooms & other fungus, and small worms and insects.

Energy Flow in Ecosystems When we look back at the food chains page, we saw that there were different levels of organisms that feed on other organisms. Each of these levels can also be called TROPHIC LEVELS. The word “trophic” comes from a Greek word that means “feeders”.

 FIRST TROPHIC LEVEL = Plants & other PRODUCERS These are also known as AUTOTROPHS (or organisms that can make their own food (auto = self, troph = feeding) These include plants, algae, and some types of bacteria.

 SECOND TROPHIC LEVEL= These are PRIMARY CONSUMERS.

 TERTIARY TROPHIC LEVEL = These eat the primary consumers. They are called SECONDARY CONSUMERS.

HETEROTROPHS: These are all the organisms that must eat something else (either plant or animal) in order to obtain energy. The word “hetero” mean “other” and the word “troph” means “feeder”. This means it eats something else. These are the same things as “CONSUMERS”

FOOD WEBS FOOD WEBS are groups of food chains that interact. Anything that happens to one part of the food web will have an effect on the other parts of the food web. This is why all food webs are so complex. You can’t do anything to one part without impacting on all other parts. There is a great picture of an interacting food web on page 35 of your text. Take a look at it now.

How does Energy Get Into A Food Web?

All energy comes from the sun. It must then be converted into usable “energy forms” by autotrophs who carry out the chemical reaction known as PHOTOSYNTHESIS that takes place in the chlorophyll filled sack known as chloroplasts (this is what makes plants green). During this process sunlight is converted into sugars and starches. These are the energy packets that all other organisms use for energy in the cells of their body.

However, not all the energy that the plant absorbs is converted into sugars and starches that can be used by other organisms. Much of the energy must be used by the plant itself just to keep it alive. Therefore, the transfer of energy is not perfect and some energy is used up and lost at each step.

Most of the energy that is taken into the animals when it eats plants or other animals cannot be passed onto the next level in the food chain. Most of the energy is used up just be moving the arms and legs, etc.

Bioaccumulation vs. Biomagnification Bioaccumulation: The increase in concentration of a pollutant from the environment to the first organism in a food chain.

If the farmer sprays pesticide on the orchard, each apple, leaf, etc. may only contain 1 ppm. If someone eats 30 apples, they might accumulate 30 ppm of pesticide in their body.

Biomagnification: The increase in concentration of a pollutant from one link in a food chain to another.

Cats must eat 3 mice Mice must eat 3 grasshoppers to stay Grasshoppers must alive eat 3 seeds to stay alive

…Each cat contains 27 ppm of toxin

…Each mouse contains 9 ppm of toxin …Each grasshopper contains 3 ppm of Each seed contains 1 toxin ppm of toxin Case Study #1 – Missing Sea Otters Sea otter populations begin to drop. Now there is Normally killer whales eat nothing to keep seals, but with seal the sea urchin populations dropping they population under turn their attention to the control! smaller sea otters.

Sea urchins eat the attachments that hold the kelp forests to the sea floor. If there are not enough sea otters to keep the urchin Herring are disappearing populations under due largely to overfishing control – the forests (trawling, etc.). This means disappear! there is less food for the seals Carrying Capacity

The carrying capacity is the largest population of a species that an environment can support.

Factors that affect the carrying capacity:

1) Available materials & energy

2) Food Chains a. Population size i. Lots of plants = lots of herbivores = lots of carnivores, etc. b. Number of predators c. Number of prey/food

3) Competition a. Intraspecific competition – when members of the same species compete for the available resources. E.g. grizzly bears fight over estuary areas while waiting for the salmon to arrive. b. Interspecific competition – when different species compete for the resources. E.g. Wolf packs that chase grizzly bears out of their pack territory in order to protect food resources and their pups.

4) Population Density – the # of individuals in a certain area.

a. Density- dependent factors - factors that impact population size due to density. E.g. Disease spreads quickly when density is high.

b. Density-independent factors – factors that impact population size regardless of the # of individuals. E.g. Fires, drought, and floods The Carbon Cycle

Photosynthesis - The process where autotrophs/producers convert sunlight “ENERGY” into food (carbohydrates, like sugars are starches). The Carbon Cycle

Carbon in the air is found in the form of CO The 2 When plants & animals Sun die, their decomposing bodies release CO back Photosynthesis: 2 CO + H O → C H O + O + H O to the environment. 2 2 6 12 6 2 2

Plants take in CO and Cellular Respiration: 2 C H O + O + H O → CO + H O + Energy release O during 6 12 6 2 2 2 2 2 Photosynthesis Animals eat the plants & other animals. Animals release CO 2 during the process of Burning fossil fuels and cellular respiration. wood releases CO to the 2 atmosphere.

Dead bodies of plants and animals can be converted into hydrocarbons (fossil Fuels) after millions of years. Burning these hydrocarbons releases CO . 2 Photosynthesis vs. respiration

Photosysnthesis

Cellular Respiration

 Cellular respiration takes place in each and every cell in our body.

 It is how the food we eat is broken down to release the energy needed for all our life processes (e.g. motion)

 All animals do cellular respiration, but plants also do respiration when they are in the dark. The Nitrogen Cycle

 Plants need nitrogen to create proteins and DNA (their genetic code).

 We can provide nitrogen to plants through the use of chemical fertilizers. The 3 main ingredients

in chemical fertilizers are Nitrogen (N), phosphorus (P), and potassium (K).

 However, where do natural ecosystems get their nitrogen?

 The air is approximately 80% nitrogen.

 Unfortunately, most organisms can NOT use the nitrogen directly from the air.

 The nitrogen must first by “fixed”.

 “Fixing” means that the nitrogran must be bonded to other elements like hydrogen (H) and

oxygen (O) to make new compounds.

+ o N + H2 → NH4 (ammonium)

- o N + O2 → NO3 (nitrate)

 The is called NITROGEN FIXATION

 Once the nitrogen has been fixed, plants can absorb the compounds through their roots.  Animals get their nitrogen by eating plants of other animals that ate plants. Animals can’t make their own nitrogen. Nitrogen Fixing Bacteria

 Nitrogen fixing bacteria in the soil or water “fix” the nitrogen in the air.  The most important nitrogen fixing bacteria are called Rhizobia.  Rhizobia are found in the nodules (swellings) on the roots of legumes (like peas, beans & clover).

 Before chemical fertilizers were created farmers would plant legumes in their fields to help add “fixed” nitrogen to the soil. Putting Nitrogen back into the air

Nitrogen compounds (fixed nitrogen) can be converted back into nitrogen gas by denitrifying bacteria. This is called denitrification. N Most of the nitrogen in2 the atmosphere (79% of the air) )is in the form of nitrogen gas – this form is not usable Lightning is one way that N 2 for plants or animals. It must be is converted into NO ! converted to nitrate (NO ) first. 3 3 In order to return the nitrates back to the atmosphere, the nitrogen must be converted Animals eat the plants and convert the nitrogen-rich back to gaseous nitrogen (N ). 2 proteins in the plants into nitrogen-rich proteins in the A second type of special “meat” of the animal. bacteria in the soil is called Denitrifying Bacteria. It does this job!

Animal wastes and the dead bodies of plants and animals contain the nitrogen compounds. These are broken down by decomposers and returned to the soil for plants to use.

Special bacteria called nitrogen-fixing bacteria live in the roots of certain bean plants. Other nitrogen-fixing bacteria live in the soil. They convert the unusable N2 into nitrates (NO3) that is then used by plants to make proteins. Nitrogen Facts:

 Nitrogen is one of the most abundant elements on Earth.  79% of Earth's atmosphere is nitrogen in gas form.  No living cell can exist without nitrogen.  But organisms cannot use nitrogen in gas form.  Multicellular life (plants, animals and fungi) depend almost entirely on bacteria to obtain (or "fix") nitrogen from the air and transform it into a chemical form that plants can use. Go Deeper: Interliving: Nitrogen-Fixing Bacteria. o Some of these talented bacteria interlive with legumes such as beans: these take nitrogen out of the air in soils. o Other bacteria live freely in the soil, processing manures and urine, and also helping to decompose dead plants and animals. o A third kind of bacteria lives in the soil and changes "fixed" nitrogen (a hydrogen compound) into nitrates (oxygen compounds), which plants can use. Without these nitrifying bacteria, agricultural fertilizers do not work. o In the ocean, cyanobacteria fix nitrogen for marine life.  Plants assimilate nitrogen from soil, and with it create amino acids and proteins.  Animals get nitrogen from eating plants or from eating other animals.

The Nitrogen cycle has two major beginnings and two major paths.  Nitrogen from soil air (to) nitrogen-fixing bacteria (to) nitrifying bacteria (to) plants (to) animals (to) decomposers  Nitrogen from dead organisms (to) decomposers (to) nitrifying bacteria (to) plants

You should know that a little nitrogen is fixed by lightning, and that volcanoes release some nitrates: both are carried to soils by rain. Too Much Nitrogen

 Adding too much fertilizer to soil results in nitrogen saturation. The extra nitrogen can “burn” the roots of plants (including trees) by making the soil acidic.  Burning fossil fuels releases a lot of nitrogen into the air. The nitrogen compounds dissolve in the moisture in the air forming ACID PRECIPIATION (acid rain and acid snow).  Acid rain can affect lakes.

 It can also destroy the wax on leaves of maple trees allowing disease to attack the trees. This has led to decreases maple syrup production.  Too much nitrogen in the environment get washed into rivers, lakes, ponds and the ocean. This can cause an explosion of growth of algae that “chokes” the water.  This is called eutrophication

1) Nitrates are carried into the water by run-off from farms & cities. 2) Increased plant growth at the surface blocks sunlight from reaching the bottom. 3) Plants below the surface can no longer do photosynthesis. Therefore, no new oxygen is produced. 4) The plants die and the # of decomposers increases greatly. This uses up more oxygen and releases more carbon dioxide. 5) With less oxygen and more carbon dioxide, fish and other animals die! Blooms of phytoplankton in the ocean can be seen from space