Ecology Basics
The branch of biology that studies how organisms interact with each other and with their surroundings.
Ecology
The first organisms to colonize bare rock or land after a major disturbance.
Pioneer Species (Lichens and Mosses)
A living factor that can affect an organism’s survival.
Biotic Factor
Organisms that produce their own food using sunlight.
Autotrophs (producers)
All the interacting populations in an area form this ecological level.
Community
This level of organization includes all members of one species living in the same area.
Population
A community that has reached stability after many years of gradual changes.
Climax Community
The type of relationship where one species benefits while the other is unaffected.
Commensalism
Describe omnivores. Give an example.
Organisms that feed on both plant and animal material.
Ex. Humans (most of the time), dogs
When a population stops increasing because resources like food or space run out, it has reached this limit.
Carrying capacity
This term describes all the regions of Earth where living things are found.
Biosphere
The predictable sequence of changes in an ecosystem following a disturbance.
Ecological Succession
Describe multulaism. Give an example
A relationship where both species benefit.
Ex. Bees and flowers
Organisms that break down dead matter and recycle nutrients.
Decomposers
Give an example of an abiotic factor that influences which organisms can live in a mountain ecosystem.
Examples: soil pH, temperature, sunlight, altitude, moisture.
Identify the ecological level that includes all biotic and abiotic factors in an area functioning together.
Ecosystem
In a typical succession from grass → shrubs → small trees → hardwood forest, which stage is the most stable?
Hardwood Forest
Describe parasitism. Give an example.
A relationship where one organism benefits at the expense of another.
Ex. Tick and a deer
A population of rabbits in a meadow increases for several years and then levels off. Which factor most likely caused the population to stabilize?
A. Decreased genetic variation
B. Increased sunlight during summer
C. Limited availability of food and space
D. Increased birth rate and decreased death rate
C. Limited availability of food and space
A population of deer increases rapidly after predators are removed from a forest. After several years, the population stops increasing and remains stable. Which statement best explains why the population stabilized?
A. The deer reached the carrying capacity of the environment.
B. The deer evolved new adaptations.
C. The deer began migrating out of the forest.
D. The deer became less able to reproduce.
A. The deer reached the carrying capacity of the environment.
These factors in an environment include temperature, light, moisture, and mineral content.
Abiotic Factors
After a forest fire, soil must be rebuilt by pioneer organisms. Explain why these organisms are necessary for other species to return.
They break down rock, form soil, and create conditions that allow plants and animals to return.
Draw a predator and prey graph. Describe the trend.
When the prey population increases, the predator population increases because they have more food. When predators eat the prey, the prey population decreases and the predator population decreases because they have less food.
What is a niche?
The ecological term for the functional role or “job” an organism performs in its environment, including what it eats.
Two species of birds live in the same habitat and eat the same type of insects. Over time, one bird population decreases in size. Which factor most likely caused this decrease?
A. Mutualism between the species
B. Competition for a limited food source
C. A decrease in predator populations
D. An increase in available nesting sites
B. Competition for a limited food source