Ecological Interactions and Environmental Factors

Ecological Interactions

• Competition: Chipmunks and squirrels
• Predation: Owls and mice
• Mutualism: Bees and tulips
• Commensalism: Robins and oak trees
• Parasitism: Mosquitoes and dogs

Application: Prairie Ponds and Duck Populations

a) An abiotic factor that influences the number of prairie ponds is precipitation (rain and snowfall). In wet years, increased water collection allows more ponds to form and persist. Conversely, during droughts, ponds shrink or dry up due to reduced water input and higher evaporation rates, causing the number of ponds to fluctuate annually.

b) The hunter’s hypothesis states that if prairie ponds are protected and their numbers increase, the duck population will rise because ducks rely on ponds for food, shelter, and breeding. The data supports this, as graphs indicate a positive correlation between pond availability and duck population size.

Key Ecological Concepts

2. The two abiotic factors that define the climate of terrestrial biomes are temperature and precipitation (rain/snow).

3. Fertilizers introduce excess nutrients into water systems, increasing the carrying capacity for algae and triggering rapid algal blooms.

4. A limiting factor is any environmental element that restricts population growth. For instance, if food availability decreases for a rabbit population, fewer individuals survive and reproduce, leading to a population decline.

Assessment Answers

A) BDAADC

B) g, c, j, a, b, p, l, i, m, f, o, e, h

Revised Ecological Interactions

• Competition: Chipmunks and squirrels
• Predation: Owls and mice
• Mutualism: Bees and flowers
• Commensalism: Robins and bird nests
• Parasitism: Mosquitoes and dogs

Application: Rainfall and Habitat Dynamics

a) Rainfall is a primary abiotic factor affecting pond numbers. Low rainfall or drought conditions cause ponds to dry up, reducing their total count. Higher rainfall increases water collection, allowing ponds to form or expand. Consequently, annual rainfall variability drives fluctuations in pond numbers.

b) The hunter’s hypothesis—that protecting prairie ponds to increase their numbers will boost the duck population—is supported by data. The correlation between increased pond availability and higher duck counts confirms that ducks depend on these habitats for survival and reproduction.

Advanced Ecological Concepts

2. The two abiotic factors defining terrestrial biome climates are temperature and precipitation (rain or snow).

3. Fertilizer runoff promotes rapid algae growth, which can deplete oxygen levels in the water, harming aquatic organisms and reducing the ecosystem's carrying capacity.

4. A limiting factor restricts population size. For example, food availability acts as a limiting factor for deer; insufficient food leads to lower survival and reproduction rates, effectively capping the population growth.