Ecology, Interrelationships In The Biosphere

Some of the images in this segment are provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE


4.1 Ecology

a. Explain energy flow and nutrient cycling through ecosystems (e.g. food chain, food web)
b. Explain matter transfer (e.g. biogeochemical cycles) in ecosystems
c. Distinguish between abiotic and biotic factors in an ecosystem
d. Compare the roles of photosynthesis and respiration in an ecosystem
e. Describe interrelationships within and among ecosystems (e.g. predator/prey)
f. Identify and explain factors that affect population types and size (e.g. competition for resources, niche, habitats, species and population interactions, abiotic factors)
g. Describe the effects of natural hazards on various habitats (e.g. earthquakes, volcanic eruptions, landslides, fire, floods)
h. Describe the impact of humans on ecosystems



Explain energy flow and nutrient cycling through ecosystems (e.g. food chain, food web)



Ecology is the study of the relationship among organisms (living things) and between living things and their environment.

Our Earth is also called the Biosphere- It is that part of the Earth that supports life and contains the following two elements..

This study will help you to learn about what biomes and ecosystems are and the balance that exists to keep them healthy and alive.




All biomes (and ecosystems within biomes) contain three different kinds of living things: 1) SAPROVORES, 2) PRODUCERS and 3) CONSUMERS.


Saprovores are organisms that decay (to deteriorate, rot or decompose) substances of dead organisms.








Examples of saprovores are seen to the left. One thing they have in common is that they have no chlorophyll (green coloring matter in all green plants that is essential for the production of sugars through photosynthesis).

Bacteria- one-cell microorganisms without chlorophyll, multiply by simple division and can be seen only in the microscope.

Fungi (plural), fungus (singular)- includes molds, mildews, mushrooms, rusts and smuts- lack chlorophyll, true roots, stems or leaves and divide with spores. Also includes small multi-cell organisms like worms.



Organisms that

1) contain chlorophyll

2) produce their own food and energy from sunlight, atmospheric carbon dioxide and water (through photosynthesis).



Left side of picture: All green plants and Cyanobacteria.

Right side of picture- Phytoplankton (microscopic organisms) IN WATER







Those living things that

1) Cannot produce their own food (animals, humans- any living thing that does not have chlorophyll)

2) Must eat other organisms (plants and/or animals) to get their energy and food.



Text of picture to left:


Some animals, like a horse, eat only plants. They are first order (primary) consumers. Bears not only eat plants but also many more things.

If a bear eats a horse it would be a second order consumer.

Third order consumers eat second order consumers.. and so on.

It is the same with saprovores...




Text of picture to the left:

TOP ROW: Berries, grasses, roots of plants (producer)--arrow--> Bear (grizzly) Eats roots, grasses, berries- First order consumer

MIDDLE ROW: Grasses (producer)--arrow--> Marmot, Elk eat grasses--arrow--> Bear (grizzly) Eats Marmot and Elk- Second order consumer

BOTTOM ROW: Grasses (producer)--arrow-->Insects eat grasses--arrow-->Chipmunk eat insects--arrow--> Bear (grizzly) Eats Chipmunks- Third Order


A bear can be a first, second, third (and so on..) order consumer depending on the type of food it eats (see above).

Humans and many other organisms can demonstrate the same relationship.







All mass comes from the earth. The green square above represents the total dry mass (weight) of all producers. The mass comes from the producer's ability to incorporate the elements of the Matter Cycles you have just studied.

All energy comes from the sun. The green, bottom part of the energy "pyramid" above represents the total sum of the energy that enters producers.

The first law of thermodynamics states that energy is not destroyed or created, it just changes forms.

The second law talks about the quality of energy. It says that when energy is changed from one form to another it goes from a more "concentrated" (higher quality) to a less "concentrated" form (lower quality).

Heat is a low quality energy

The light of the sun is the highest quality of energy.

The energy that the producers incorporate into themselves from the sun is a lower quality energy than the sun.

From every 1 million kilocalories of sunlight, 10,000 kilocalories are available to producers. The remainder changes to heat energy.



We will first concentrate on the Biomass(matter) of the earth.


2. This is the total dry weight of all herbivores (organisms that are able to receive their food exclusively by eating plants or algae).

There is a significant decrease in the amount of mass in total herbivores (organisms that eat plants or algae). What this says is that not all plant matter becomes part of the animal that eats it.








3. This is the total weight of all carnivores. This is significantly less than the mass of the herbivores in #2 that suggests that not all of the mass of the first order consumers are eaten by the carnivores (second order consumers)

The implication of this significant decrease is that the NUMBERS of herbivores are significantly less than producers, and that the NUMBERS of carnivores are significantly less than the numbers of herbivores.

Another way of seeing this is that it is very inefficient to eat just meat to get our matter and energy because there is less numbers of animals available.

It also says that a greater number of individuals can be supported if we change our diets from a meat-eating society to a plant-eating society.





2. As in biomass, the energy available for first order or primary consumers is significantly decreased.

Only 1000 kilocalories for every 1 million kilocalories of sunlight is available to first order consumers.

This energy is derived from first order consumers eating the producers. It is a much lower quality energy






3. This is the energy available for second order consumers (or secondary consumers).

There are 100 kilocalories of energy available for every 1 million kilocalories of sunlight. First order consumers are an even lower quality energy source for second order consumers. Second order consumers are an even lower quality energy source for third order or tertiary consumers. There are only 10 kilocalories of energy available from every 1 million kilocalories of sunlight.

An example of a third order consumer is if we catch a fish that eats smaller fish which eats zooplankton (small organisms that are first order or primary consumers), which eat phytoplankton (producers). WE WOULD RECEIVE MORE EFFICIENT ENERGY BY EATING ZOOPLANKTON OR PHYTOPLANKTON




1. All of the plants on earth are not eaten by first order consumers. After that large proportion live out their normal life span, they die.

This is the first of the three reasons that a significant drop in biomass is experienced between the producers and the first order consumers

Dead plants are decomposed by the saprovores which obtain their food and energy from dead material. They are called decomposer organisms and are part of the Decomposer Food Chain.





2. That part of the producers that is eaten becomes a part of the Grazer Food Chain -All of the biomass of the eaten plants is not converted to the biomass of first order consumers.









3) THE PART THAT IS DIGESTED: Most of the mass of the eaten producers is digested by the first order or primary consumers.










4) ENERGY FOR BODY GROWTH/HEAT: A portion of the biomass of the digested producers is converted into energy.

This energy is used by the first order consumer for all of the enzymatic reactions needed for body growth

This energy is converted to heat and lost to the atmosphere. It is the principle reason that so much energy is lost between the biomass of the producers and that of the first order consumers.






5) BODY BUILDING/GROWTH: Not all of the biomass of the digested producers goes into the biomass of the first order consumer because part is used for energy for growth.

The majority of the digested biomass makes up the biomass of the first order consumer (cell walls, muscles, bones, tissues etc.). This is the second of three reasons that there is a significant reduction in biomass between producers and first order consumers.






6) UNDIGESTED FECAL WASTE: The part of the eaten producers that is not digested is the undigested portion

This part of the consumed producer (fecal wastes) is excreted and is decomposed by the Decomposer Food Chain This is the third of three reasons why there is a significant decrease in biomass between producers and first order consumers.







7) EXCRETION, URINE OR CELL WASTES: A portion of the digested material is excreted as waste in the urine (or cell fluids for one-cell organisms) and returns to the nutrient cycles.









8) RELEASE CARBON DIOXIDE, WATER, HEAT, MINERALS: Both the Grazing and the Decomposer Food Chains result in the release of carbon dioxide, water, heat and minerals (phosphates, calcium, etc.).

This is a result of the breakdown of biomass (digested, undigested and dead plants) for the production of energy by the first order consumer and decomposing bacteria and fungi.







You are now ready to understand the principles of Food Webs and Chains.










A FOOD WEB is shown above. It is the detailed interaction between single food chains in an ecosystem.

A single food (matter) and energy pathway is called a food chain. This is a series of organisms, each being eaten by the preceding organism.

Example: 1) grasshopper eats green plants, lizard eats grasshopper and hawk eats lizard.

2) grasshopper eats green plants and hawk eats grasshopper

Practice: THERE ARE STILL EIGHT MORE MATTER AND ENERGY PATHWAYS IN THE DIAGRAM ABOVE. IDENTIFY THEM. ALSO IDENTIFY THE GRAZER AND DECOMPOSER FOOD CHAINS. Choose one of the food chains and a) remove, b) decrease in number, c) increase in number several parts of the chain. With each a), b) and c) that you do, tell how it would influence the overall balance in the community to numbers of animals, availability of food, etc.


2. Explain matter transfer (e.g. biogeochemical cycles) in ecosystems


Distinguish between abiotic and biotic factors in an ecosystem

More details found below (influence of abiotic factors in ecosystems).



Compare the roles of photosynthesis and respiration in an ecosystem

General Comparison of Photosynthesis and Cellular Respiration

1. Photosynthesis and cellular respiration occur in plants and other photosynthetic organisms. From carbon dioxide, water and the sun's energy, glucose is formed during photosynthesis. In cellular respiration, glucose is broken down, releasing energy.

2. Cellular respiration occurs ONLY in animals/mammals. This implies an absolute need for glucose in the diet of non-photosynthetic organisms.

3. Energy from the sun forms high energy bonds in glucose molecules. When degraded during cellular respiration energy for all cell and enzyme functions, including all of our activities as human beings is released.

4. The precursors of photosynthesis are carbon dioxide, energy from the sun and water. The product is glucose.

5. The precursor of cellular respiration is glucose. The products are energy, carbon dioxide and glucose.

6. Cellular respiration is the opposite chemical reaction of photosynthesis.

7. All steps in both chemical reactions are performed by different enzymes.



Photosynthesis and Cellular Respiration: Summary (Animation)

Click on Green Box to Begin:

1) Photosynthesis and cellular respiration are the basis for the existence of life on this planet. Click on green box to continue..

2) The chloroplast (drawing at the top) and the Mitochondria (lower right of animation) are the organelles in photosynthetic organisms that create and utilize the energy required for cellular functions. Click on green box to continue...

3) Two reactions occur in the chloroplast. One is called the light reaction occurring in the granum (looks like a pile of coins) and the dark reaction occurring in the stroma (looks like bridges between grana). Click on green box to continue...

4) Cellular respiration occurs in the mitochondria in structures called the Cristae. Click on green box to continue.

General Consideration of respiration and photosynthesis. (Click on green box to continue)

5) The energy in light produces chemical energy that is temporarily stored. These reactions are mediated by different enzymes. Click on the green box to continue.

6) Water undergoes an enzymatic reaction producing water and oxygen. The water stays in the grana to continue this part of the light reaction. Oxygen also leaves the cell and enters the atmosphere. Click on green box to continue.

7) The stored energy moves to the stroma as carbon dioxide enters the stroma thus commencing the DARK REACTION. Click on green box to continue.

8) During the dark reaction the stored energy powers the enzymatic synthesis of the sugar glucose from carbon dioxide. Glucose leaves the chloroplast and travels to the mitochondria. Much of the stored chemical energy is transferred to the bonds holding the glucose atoms together. More water is produced in this enzyme reaction. Click on green box to continue.

9) Glucose was actively transported through the membranes of both the chloroplasts and the mitochondria. Once inside the mitochondria, cellular respiration now begins. Click on green box to continue.

10) The reaction takes place in the Cristae. You will now watch the chemical reaction (all steps done by enzymes). Glucose will be broken down and carbon dioxide and water are the products of the reaction. Carbon dioxide leaves the mitochondria. Part of the carbon dioxide is recycled again through chloroplasts. The rest is excreted into the air or through exhalation for mammals/animals. Click on green box to continue

11) Breakdown of glucose also produces chemical energy that is used throughout the entire body for cell and enzyme functions as well as breathing, walking, running... in short.... being able to live and move. The energy is called ATP (adenosine triphosphate). Adenosine is the DNA/RNA purine nucleotide we have already seen. It has three instead of just the one phosphate present in DNA. The other two phosphates have high energy bonds. Click on green box to continue.

12) Water, like carbon dioxide, is recycled to other parts of the organism. It too can be eliminated. Once ATP is used for energy it loses a phosphate and becomes ADP. It is only recycled..not eliminated. Click on green box to reset animation and review it again...or continue by clicking on the right arrow below.

For details about photosynthesis and respiration, click here.




Describe interrelationships within and among ecosystems (e.g. predator/prey)



1. Prey: -the organism that is killed (and eaten) by another organism. The fish/rabbit are the prey.

2. Predator: -an organism that kills another organism (for food) -examples:


a) when a bird catches and eats a worm, b) when a bear eats a fish,

c) when a horse grazes on grass

The interaction is beneficial to the predator but not to the prey.

Prey populations are benefited because those killed are sickly or weak or old. This maintains the prey population small enough for its available food.

This is a DIRECT RELATIONSHIP because both the prey and predator are directly affected by this relationship. The prey loses its life. The predator has a meal which allows it to survive another day.




3. Parasitism: occurs when one organism lives on or even inside another (called the host).


-parasites obtain food by slowly eating the host or eating fluids inside the host





Identify and explain factors that affect population types and size (e.g. competition for resources, niche, habitats, species and population interactions, abiotic factors)




From Bartholomew and Finklestein, J.Bact., 75:77, 1958

A RELATIONSHIP BETWEEN TWO SPECIES THAT IS BENEFICIAL TO ONE, BUT NEITHER BAD NOR GOOD FOR THE OTHER. This is a DIRECT RELATIONSHIP for the bacteria because the presence of food in the intestine directly affects the bacteria but it doesn't cause disease or death to the other (see example below).

Examples: 1) Bacteria inside human intestines that do not cause disease in humans or help humans but who find plenty of food to eat in the intestines.





Example: Lichens are grey-green colored plant-like organisms (not the bright green color of mosses) that live together with green or blue-green algae (actually the algae lives inside the lichen).

Lichens have no roots -the lichen collects water from rain and nutrients (such as calcium, magnesium, etc.) from rocks or tree trunks where they grow.

-the algae captures sunlight and produce matter and energy for the lichens to grow using the water and nutrients collected by the lichens. One needs the other to be able to grow.






Example: Sea gulls in California do not affect in any way the other kinds of birds living nearby

-they don't affect each other because they don't interact in any way




AN IMPORTANT RELATIONSHIP IN NATURE. IT INVOLVES A COMPETITION BETWEEN TWO SPECIES (SAME OR DIFFERENT SPECIES) FOR SIMILAR RESOURCES. This is an INDIRECT RELATIONSHIP because it indirectly affects other species by decreasing the scarcity of a particular need for survival.

Example: 1) A fox and a coyote may compete for a common food source such as a rabbit. 2) Cougars and mountain lions may compete for a common home such as a cave. 3) A group of animals may compete for the water in a small water hole for survival.




From Wilson and Plunkett, The Fungous Diseases of Man, University of California Press, 1967

A RELATIONSHIP OF A BACTERIA, VIRUS OR FUNGUS TO A HOST THAT RESULTS IN A DISEASE. This is a DIRECT RELATIONSHIP because something bad happens to one of the species (disease) and something good to another (it grows and thrives).

Example: 1) AIDS virus causes disease in man 2) A bacterial infection threatens the existence of a species of animal. 3) A fungous causes a disease in or on a host.




Populations: living things of the same kind- such as all horses, or all dogs, or all bees.

There are many kinds of horses, dogs and bees but a population represents all kinds of a single type of living thing.




Individuals (organisms)

Individual (or organism): a single species or kind within a population

- an Arabian horse (horses)

- a Terrier (dogs)

- a Hornet (bees) are all examples of an individual.

Ecologists study individuals, populations, ecosystems, biomes and the ecosphere (biosphere)



Habitat and Niche


No two species can occupy the same niche but similar species living in the same habitat can have similar ways of living

Example: Hawks and owls prey on mice; both live in forests together. Their niche is slightly different because hawks hunt during the day and owls hunt at night.




ECOSPHERE (BIOSPHERE): This is the part of the earth that supports life and extends from the floor of the ocean, at 36,000 feet (11,000 meters) below sea level, to the top of the highest mountain-at 30,000 feet above sea level (9,000 meters).




-If the earth (above) were the size of an apple, then the area that supports life would be about the thickness of the skin of the apple.


-The biosphere (ecosphere) recycles all matter except for the energy received from the sun. This is why it is called a CLOSED SYSTEM. It is this recycling that allows life to exist on this planet.





The land we walk on is part of the lithosphere of the earth and is called the crust. Most life exists between 100 meters below sea level to 6,000 meters above sea level.






Interesting facts:







Biomes are the land portion of the ecosphere or biosphere.

The two most important contributing factors of weather that govern vegetation are

Temperature and precipitation also govern the kinds of climates that exist in any one area.

The yellow and green lines above represent how far north or south of the equator (red line) we are. It is warmest at the equator. The temperature becomes cooler as one goes away from the equator traveling either north or south.




It is the same with altitude. The higher we go above sea level, the cooler it gets. The climates and biomes change as altitude increases. The same thing happens as we go south of the equator to the South Temperate and Antarctic Zones.











Ecosystems, Relationships In Ecosystems, Biological Communities



Ecosystem (Ecological System)-The interaction of all living things (Biotic factors) among themselves and with their environment (Abiotic factors) in a particular place in the Biosphere.



Community- the organisms living in a given area

Although the area represented by the community above is small, it is part of a much larger area as shown in the drawing below.








The only difference between an ecosystem and a community is that in the community only living things and their relationships are studied. Effects of the environment are not considered when looking at a community.

In an ecosystem, the environment (Abiotic) is included in the study.

The extended community on the drawing with the elephant (and includes the smaller community above) consists of snakes, birds, many kinds of insects living above the ground as well as on and beneath the ground... frogs, dozens of different kinds of plants, elephants, giraffes and many other mammals- These form a complex community of living things.





Community boundaries are limits set for study purposes only. Logical limits or boundaries do exist (for example- oceans, rivers). Latitude (which is how far north or south of the equator one is), influences temperature and moisture and is another natural boundary.


Arctic Communities

Tropic Communities


Examples of communities at different latitudes are given below.


Arctic Communities: very few species can grow. Those that can grow have all food and energy to themselves because there is only a small number of different kinds of organisms.

-changes in numbers of organisms (individuals) causes drastic changes in community

- this community is unstable


Tropic Communities: there are many species and small numbers of rare species. Only a small part of the food and energy pass through each species so if something happens to one, there are few effects felt in the entire community.

-These communities are very stable.



Principles of Ecology Studies:

Ecologists want to know


TEXT OF DRAWING ABOVE: TOP: Effect of abiotic factors on populations and communities. FAR LEFT TO RIGHT (MIDDLE OF DRAWING): No Life, Small Numbers of Living Things, Optimum Range, Small Numbers of Living Things, No Life. LOWER LEFT: Concentration of abiotic chemical and physical factors are too low. LOWER RIGHT: Concentration of abiotic chemical and physical factors are too high.

The graph above shows that when the abiotic chemical and physical factors that exist in ecosystems are too high or too low, there is no life possible.

When the concentration of these factors is "just right" populations and communities thrive. (See details below)

No life-low concentration factors:



No life-high concentration factors:



Small numbers-lower than normal concentration factors or higher than normal concentration of factors:



Optimum conditions:




Describe the effects of natural hazards on various habitats (e.g. earthquakes, volcanic eruptions, landslides, fire, floods and more.

Describe the effects of natural hazards on various habitats (e.g. earthquakes, volcanic eruptions, landslides, fire, floods and more)


Describe the impact of humans on ecosystems

Problems Caused by Human Modifications of Groundwater System

        Groundwater currently provides about 20% of all water used in the US. Human modification of the groundwater system can have several long-lasting consequences:

    1. Reducing groundwater withdrawal.
    2. Re-injecting treated wastewater into recharge wells.
    3. Construction of recharge ponds.

Other impacts on ecosystems by humans- and don't forget the rainforests

Select an area of the globe to discover human impact



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