What is Ecology?
This photograph is of cattle grazing in a New Mexico pasture. Study the scene carefully,
keeping in mind that its location, New Mexico, is quite different from, say, Michigan,
Vermont, or Wyoming. Many plants and animals besides the cattle live in this pasture.
You would recognize some of these; others may take some thought on your part to
discover. For instance, quail might nest beneath the shrubs in the background. A lizard
might rest in the shade of the yucca plant. Long tapeworms might be found in the
intestines of the cattle. List any animals and plants you think might live in this New
Mexico pasture. Feel free to include both organisms that live here permanently and those
that might be common visitors.
Living Things Present in Pasture
1. Cows.
2. Grass.
3. Cactus.
4. Yucca.
5. Insects.
6. Snakes.
7. Rabbit.
8. Birds.
9. Coyote.
10. Antelope.
11. Buffalo.
12. Eagles.
13. Vultures.
14. Dung beetles.
15. Lizards.
16. Spiders.
17. Scorpions.
18. Flies.
19. Deer.
20. Wildflowers.
Ecologists are interest in studying the living things you listed and others as well. They
would study not only the grasses and shrubs but also all other plants and animals
inhabiting or visiting the pasture. They would include the cattle as well as the flies, ticks,
and parasitic worms that affect the cows. Ecologists would include the ants, earthworms,
and beetles that burrow in the soil. The lizards and rodents that scurry among the grasses
would be objects of study as well as the snakes and hawks that eat these animals.
Ecologists would even study people, since the domestic cattle are evidence of people’s
presence in this pasture.
Although ecologists would identify as many living things as possible, this would not be
their only purpose. As you listed the animals and plants, you probably though of them in
terms of where they lived in the pasture or what they were doing there. Ecologists try to
do the same. For example, burrowing insects are associated with the soil. Their burrows
make air spaces in the earth, and their waste materials add nutrients to the soil. The quail
and the shrubbery are related to each other, also. Quail might nest beneath the shrubs and
hunt for insects harmful to those shrubs.
When studying living things, ecologists might ask the following questions. Try your
hand at answering them.
 In what ways are the cattle dependent on the grassland? Explain your answer.
Cows depend on the grassland because they eat the grass; they also need it for water and
shelter.
 How is the grassland dependent on the cattle?
The grasslands benefit by the cows being their so they can fertilize it, trim it down when
they east it, and also to kick the manure around to help.
 How might the cattle harm the grassland?
Cattle can over eat the grass and harm it beyond recovery. Two bites is a good size.
 In what ways do the plants in the pasture compete with each other?
The plants compete with each other for water, space, and nutriets.
 What animals might compete with the cattle for food?
The rabbits may compete with the cattle for food as well as deer, antelopes, and other
grass-eating things.
 Why might this competition occur?
Competition may occur because they have limited resources, which leads to that
competition.
 What is the main purpose of raising cattle?
One big purpose of raising cattle is for the food they provide for us.

What might this environment look like in 10 years if humans and their cattle were
removed?
Well the ground would not be as fertile as if we were there. Some alien plants could also
come and take over things. Or, it could work the other way, it could give some plants a
chance to live.
Of course, the grass is the main source of food for the cattle. Without it the animals
would die unless humans supplied hay and silage in its place. Cattle depend almost
totally on grass and other herbs. People’s dependence on cattle, however, is only partial,
since they eat other foods besides beef. Cattle can overgraze an area and destroy it as a
food source. Whether they did or not would depend on the size of the cattle population.
The waste materials from the cattle can also enrich the soil. Such relationships are the
types of data the science of ecology deals with.
Ecologists help explain the natural relationships that exist between the plants and animals
in our world. These relationships are called interactions. When organisms interact, they
affect one another and bring about some type of change. Cows interact with grass. One
piece of evidence of this interaction relationship is a size and weight gain in the cow.
Cattle manure interacts with soil as evidenced by increased fertility of the grazing land.
Ecologists’ study of interactions usually includes the role of people, since people are
probably the most influential change agents on earth.
There is one more item to add to your understanding of what ecology is. You are aware
that the types of plants and animals found in the New Mexico pasture are very different
from those found in Florida. What causes the differences? What factors might influence
the kinds of living things that exist in a certain area? Give three examples below:
1. Soil type.
2. Elevation.
3. Humidity.
If you were to study the geographic location and climate of this area of New Mexico, you
would discover that it is characterized by a certain elevation, annual rainfall, temperature
range, soil type, humidity, and land formations such as the mountains in the background
of the photograph. Ecologists have discovered that those nonliving factors, called abiotic
factors, greatly influence living things and interact with them. Often one abiotic factor
may influence another abiotic factor, which in turn influences living things. For example,
there is a decrease in temperature as elevation increases. There is an increase in
precipitation as elevation increases. This lowered temperature and increased
precipitation interact and cause a shorter growing season. These interacting abiotic
factors will limit both the types and sizes of plant life able to survive at upper elevations.
Soil type influences the amount of rainfall that can be absorbed. The amount of available
moisture in the soil will influence the plants that can grow there. What other examples
can you think of?
By putting together the three parts we have just discussed – living things, abiotic factors,
and the interactions that exist between them—you should now have a good working
definition of ecology.