Wildlife Encounters - 9th - 12th grade
Lesson 2: Wildlife Populations
  • Key Words

Wildlife Populations

Populations are all the members of a species that live in a one area. You are part of the human population for your home town. A freshwater pond has multiple populations, including a population of mallard ducks, and a population of cattail plants growing on the edge.

All of the populations that live and interact with each other in one area make of the community of that area. Our freshwater pond community includes the mallard ducks, the cattail plants, the fish in the pond, and many other species.

The populations and community are affected by many non-living factors in the area, such as the water of the pond, the amount of sunlight, the different nutrients of the soil, and even the quality of the air. All these living and non-living components form the ecosystem of freshwater pond.

ducks on a river

The interactions of an ecosystem are often described as webs that show how the pieces are interrelated. An example of a generic food web in an ecosystem is shown below. All the species connect in multiple interactions, and are dependent on each other.

ecosystem diagram

For the ecosystem to be healthy, every part of that ecosystem must be healthy too. Likewise, to protect an ecosystem, every part, from soil to water to prey animals to predators, must be protected.

If one piece of the web is damaged, everything it interacts with will be affected. It is this interrelatedness that explains why losing one species can lead to the loss of other species.

When ecosystems become unbalance, whole populations of animals are more susceptible to diseases or other disturbances. The health of ecosystems is a delicate balance of plant, animal, environment, and human interaction.

Human activities are one of the biggest influences on ecosystems and the populations in them. The graph below shows the decline in the American Woodcock populations in every state except Illinois. Woodcocks live in forest ecosystems, and human population growth has caused a decrease in forest size as more land is developed for human homes, agriculture, and industry. The growing human population has caused many wildlife populations like the woodcock populations to decrease in size.

woodcock abundance graph
Natural History