Community Ecology Practice Flashcards

Comprehensive practice questions covering community ecology interactions, diversity indices, trophic structures, and control mechanisms based on Chapter 54 lecture notes.

What is the definition of competition in community ecology?

A −/− interspecific interaction where both species are harmed by sharing limited resources, which can lead to competitive exclusion or niche partitioning.

What is Gause's principle regarding competitive exclusion?

Two species with identical niches cannot coexist permanently; the better competitor will eventually eliminate the other.

How is an ecological niche defined?

The full set of biotic and abiotic resources an organism uses in its environment, representing its ecological role including food, habitat, temperature range, and timing of activity.

What is the difference between a fundamental niche and a realized niche?

A fundamental niche is the full range of conditions a species could potentially occupy without competitors, while a realized niche is the actual portion occupied after competition limits it.

How does resource partitioning allow similar species to coexist?

Through the differentiation of niches, such as using different perch heights, diets, or active times, as seen in Anolis lizards.

What is character displacement?

The tendency for traits to diverge more in sympatric populations (where species overlap) than in allopatric populations, such as Galapagos finch beak depths.

What characterizes the interspecific interaction known as predation?

A +/- interaction where the predator kills and eats the prey, driving the evolution of adaptations like venom, speed, camouflage, toxins, and mimicry.

What defenses have plants evolved to counter herbivory?

Chemical defenses such as $\text{nicotine}$ and $\text{tannins}$, and structural defenses like $\text{thorns}$.

What is the distinction between endoparasites and ectoparasites?

Endoparasites live inside the host (e.g., tapeworms), while ectoparasites live outside the host (e.g., ticks and lice).

Define mutualism and provide an example from the notes.

A +/+ interaction benefiting both species; for example, acacia trees provide food and shelter to ants that protect the tree from herbivores.

What is commensalism?

A +/0 interaction where one species benefits and the other is unaffected, such as cattle egrets catching insects flushed out by buffalo.

Contrast aposematic coloration and cryptic coloration.

Aposematic coloration is bright warning colors signaling toxicity (e.g., poison dart frogs), while cryptic coloration is camouflage (e.g., canyon tree frogs) used to hide from predators.

How do Batesian mimicry and Mullerian mimicry differ?

In Batesian mimicry, a harmless species mimics a harmful one; in Mullerian mimicry, two or more harmful species resemble each other to reinforce predator avoidance.

What are the two components of species diversity?

Species richness (the number of different species) and relative abundance (how evenly individuals are distributed among those species).

What does a higher Shannon diversity index ($H$) indicate about a community?

A higher $H$ value indicates a more diverse community based on both richness and relative abundance.

What is the difference between a food chain and a food web?

A food chain is a linear sequence of energy transfer, whereas a food web is a network of interconnected chains that more realistically shows species eating at multiple trophic levels.

What is the energetic hypothesis's explanation for short food chains?

Food chains are usually limited to $4$-$5$ links because energy transfer is so inefficient that too little energy remains to support additional trophic levels.

What is the average trophic efficiency across levels?

Averages approximately $10\%$, with the remaining $90\%$ lost to respiration, feces, and uneaten biomass.

What defines a keystone species?

A species that is not necessarily abundant but exerts a disproportionately large effect on community structure, such as the Pisaster sea star controlling mussel populations.

Define foundation species and provide an example.

A species with strong effects due to large size or high abundance that contributes habitat or food, such as American chestnut, kelp, or corals.

What is an ecosystem engineer?

A species that influences community structure by physically creating, modifying, or destroying habitat, such as beavers building dams.

Contrast bottom-up control and top-down control.

Bottom-up control is limited by nutrients or food at lower levels; top-down control occurs when predators limit herbivores, creating a trophic cascade.

What is a trophic cascade?

The indirect effects where adding or removing a top predator causes alternating increases and decreases in populations at lower trophic levels.

What is an invasive species?

A non-native species introduced to a new region that disrupts native communities because it lacks its natural predators and competitors.