What is carrying capacity?

• The maximum number a habitat can support over time
• The number of young born in the whole habitat each year
• The speed of the exponential phase

Put these three named phases of a closed microbial culture in their usual order.

• Exponential, lag, stationary
• Lag, exponential, stationary
• Stationary, lag, exponential

Under stable conditions, a population grows and levels off as shown in the yearly bars. Estimate its carrying capacity.

• About 260, where the bars climb fastest
• About 30, the starting count
• About 370, where the bars level off

Which described effect is density-independent?

• Disease spreads faster per animal when more animals share the same area
• Predators take a larger fraction of prey when more prey share the same area
• A flood gives each animal the same death risk at low and high density

Which described effect is density-dependent?

• Food competition reduces survival more as animals crowd together
• An eruption kills more animals in a denser population, but the fraction killed is unchanged
• Frost survival per animal is unchanged when more animals occupy the same area

For populations starting well below K, how do ideal exponential and logistic growth models differ on a graph?

• Exponential is S-shaped toward K; logistic is J-shaped
• Exponential is J-shaped; logistic is S-shaped toward K
• Both are S-shaped and approach the same fixed value of K

In equal-sized fields, a frost kills the same fraction of a population of ten voles as of ten thousand. Its effect is density-dependent.

A deer herd stops growing while grass still covers the fields. Which explanation could account for this?

• Grass covers the fields, so food quality must be adequate and food cannot limit the herd
• Food quality, disease, and predators may limit growth
• Births always stop as soon as any crowding begins, even with plentiful resources