exam 3

Question 1

What are the three different types of competition?

Answer 1

Interference, resource, apparent competition

Question 2

Define interference competition

Answer 2

Direct interactions, such as physical aggression, to gain access to resources

Question 3

Define resource competition

Answer 3

Indirect competition where species consume shared, limited resources

Question 4

Apparent competition

Answer 4

Occurs when two species indirectly compete by influencing the abundance of a shared predator

Question 5

What is competitive exclusion?

Answer 5

Occurs when one species outcompetes another, leading to the local extinction of the weaker competitor

Question 6

What are the different variables in the Lotka-Voltera model?

Answer 6

• N1, N2 = Populations sizes of species 1 and 2
• r1, r2 = Per capita growth rates
• K1, K2 = Carrying capacities
• a12, a21 = Competition coefficients measuring the effect of one species on another

Question 7

What can we interpret about the Lotka-Voltera model?

Answer 7

• If interspecific competition is stronger than intraspecific competition, one species may be excluded.
• If intraspecific competition is stronger, species can coexist.

Question 8

What are some limitations of the Lotka-Voltera model?

Answer 8

• Assumes constant environmental conditions.
• Does not consider resource variability.
• Ignores species adaptations and behavioral changes.

Question 9

How can competing species coexist?

Answer 9

• Environmental heterogeneity: Spatial or temporal variation allows species to avoid direct competition.
• Niche partitioning: Species specialize in different resources or habitats to reduce overlap.

Question 10

What are the four main types of exploitative interactions?

Answer 10

• Predation: One organism kills and eats another (high lethality, low intimacy).
• Parasitism: One organism lives on or in another, harming it but usually not killing it (low lethality, high intimacy).
• Herbivory: Consumption of plant material (moderate intimacy and lethality).
• Pathogens: Microorganisms that cause disease (high intimacy, variable lethality).

Question 11

What is the difference between constitutive and induced defenses? What are some advantages and disadvantages of each type?

Answer 11

Constitutive defenses: Always present (e.g., spines, toxins).
- Advantages: Constant protection.
- Disadvantages: Energy costly even when not needed.

Induced defenses: Triggered by predators (e.g., chemical release).
- Advantages: Energy-efficient.
- Disadvantages: Slower response time.

Question 12

Define aposematism

Answer 12

Warning coloration signaling toxicity or unpalatability.

Question 13

Define mimicry

Answer 13

Some species imitate aposematic organisms for protection (e.g., Batesian and Müllerian mimicry).

Question 14

Define the Red Queen Hypothesis

Answer 14

Species must continuously evolve to keep up with changing environments and co-evolving predators or parasites.

Question 15

What is the difference between mutualism and commensalism?

Answer 15

Mutualism: Both species benefit
Commensalism: One species benefits while the other is unaffected.

Question 16

How do plants and pollinators benefit from animal pollination?

Answer 16

• Plants receive efficient pollen transfer.
• Pollinators obtain nectar or pollen as food.

Question 17

How do plants and seed dispersers benefit from each other?

Answer 17

Animals transport seeds, increasing plant fitness.

Question 18

Define directed dispersal

Answer 18

Seeds are placed in optimal conditions for germination.

Question 19

How do ant-plant mutualisms work?

Answer 19

Ants provide protection against herbivores, and plants offer shelter or food.

Question 20

Describe some examples of how mutualisms can be disrupted (e.g., how do partners prevent cheating, what are some consequences of losing a mutualist partner)

Answer 20

Cheating prevention: Some species have mechanisms to deter non-cooperative partners.
Loss of a partner: Can lead to declines or extinction of dependent species.

Question 21

define species richness

Answer 21

Species richness is the number of different species in a community.

Question 22

define species evenness

Answer 22

Species evenness describes how similar the abundances of different species are. A community where all species have similar population sizes has high evenness, while one dominated by a few species has low evenness.

Question 23

What is a rank abundance curve and how do you interpret one?

Answer 23

• A rank abundance curve (also called a Whittaker plot) graphically represents species diversity by plotting species abundance (y-axis) against their rank (x-axis).
• A steeper slope indicates lower evenness (one species dominates), while a flatter curve suggests greater evenness.

Question 24

define alpha, beta, and gamma diversity

Answer 24

• Alpha diversity: Species diversity within a single community or habitat.
• Beta diversity: Species turnover between communities, calculated as β = γ/⍺.
• Gamma diversity: The total number of species across all communities.

Question 25

how do you measure alpha, beta, and gamma diversity

Answer 25

Measurements often include species counts and diversity indices (e.g., Shannon index).

Question 26

what is another way to calculate beta diversity?

Answer 26

using the Dice-Sorensen Similarity Index: DSC = 2Sb/(S1+S2) Sb = number of shared species S1 = species in community 1 S2 = species in community 2

Question 27

Shannon evenness index definition

Answer 27

Uses species richness and species abundance to track similarity H = -Sigma (S, i = 2)*pi*ln(pi) S = number of species pi = proportion of individuals in a species

Question 28

Hurlbert's PIE

Answer 28

(N/(N - 1))*(1 - sum of (pi^2) where pi = proportion of individuals in a species

Question 29

what is the difference between resistance and resilience?

Answer 29

- Resistance: A community’s ability to avoid significant change when disturbed. - Resilience: The ability of a community to recover after a disturbance.

Question 30

What hypotheses explain why we expect more diverse communities to be more stable?

Answer 30

sampling effect (portfolio effect), niche differentiation, facilitation hypothesis

Question 31

define sampling/portfolio effect

Answer 31

Diverse communities are more likely to include highly productive species that can respond well to disturbances.

Question 32

define niche differentiation hypothesis

Answer 32

Diverse communities use resources more efficiently, reducing competition.

Question 33

define facilitation hypothesis

Answer 33

Some species in diverse communities enhance ecosystem function.

Question 34

What does the Janzen-Connell hypothesis predict?

Answer 34

- Suggests that seedlings have higher survival rates when they disperse away from the parent tree due to escape from pests and pathogens and other seedlings. - Provides an explanation for high species richness in tropical rainforests by preventing any one species from becoming too dominant.

Question 35

Summarize the Powell (Resident Yellow Warblers vs. Wintering American Redstarts for territories) study

Answer 35

- Experiments and methods: Researchers removed Yellow Warblers from specific areas where Redstarts lived and then tracked the movements and health of Redstarts.as body condition and return rates - Findings: Yearling male Redstarts moved into the space left by Yellow Warblers, while adult males with overlapping territories had worse health and lower chances of returning the next year. This shows that competition affects Redstarts negatively.

Question 36

Summarize the Nogués-Bravo (Rewilding) study

Answer 36

- Purpose of study: examines rewilding (practice of restoring ecosystems through species reintroductions). It highlights the lack of consensus on rewilding definitions and emphasizes the unknown risks associated with introducing new species. Methods: reviewing existing literature on rewilding and analyzing case studies of species reintroductions, such as wolves in Yellowstone. The authors argue that while rewilding aims to enhance biodiversity and ecosystem function, it often lacks empirical support for its assumptions, particularly regarding top-down control by predators. Key findings: rewilding can lead to unintended ecological consequences, such as complete removal of native species and challenges in controlling introduced species. The authors recommend prioritizing biodiversity conservation over rewilding projects and conducting thorough cost-benefit analyses before implementation.

Question 37

Summarize the Lepczyk (domestic free range cat diet) study

Answer 37

Key Findings: Free-ranging domestic cats (Felis catus) are invasive carnivores with significant impacts on biodiversity, 16.7% of species of conservation concern. They prey mostly on birds, then reptiles, and mammals. Islands exhibit three times more species of conservation concern compared to continents, so island cats are more of a concern. Methods: Compiled data from 544 studies on cat diets globally, narrowing down to 533 that provided species-level information. Analyzed species consumed by taxonomic group, geographic location (island vs. continent), conservation status, and body mass. Used species accumulation curves to estimate species diversity in diets, which were found to be conservative and non-asymptotic, indicating more species await discovery. Conclusion: The study highlights the ecological risks posed by cats as generalist predators and underlines the necessity for management strategies to mitigate their impact on vulnerable wildlife.

Question 38

Define indirect facilitation and provide an example

Answer 38

- Occurs when one species benefits another through a third intermediary species, rather than through direct interaction. - Example: wolves in Yellowstone indirectly facilitating aspen regeneration. Wolves reduce elk populations, which decreases browsing pressure on aspen trees, allowing them to grow more successfully.

Question 39

What ecological principles are highlighted in the sea otter study?

Answer 39

Sea otters serve as a keystone species in the Aleutian Islands’ subtidal community. By preying on sea urchins, they prevent excessive kelp consumption, maintaining kelp forest ecosystems.

Question 40

What ecological principles are highlighted in the Yellowstone wolf study?

Answer 40

Yellowstone wolves: their reintroduction affected the ecosystem by reducing elk populations, which allowed vegetation like aspens to recover. However, the impact was uneven and not all areas saw full forest recovery.

Question 41

What ecological principles are highlighted in the starfish case study?

Answer 41

Starfish (pisaster): keystone species study by Paine (1966) showed that removing Pisaster led to drastic decline in species diversity, as mussels dominated the habitat, reducing community complexity.

Question 42

What are the main categories of participants in a food web?

Answer 42

- Producers (autotrophs) - Consumers: Herbivores (primary consumers) Carnivores (secondary/tertiary consumers) Omnivores - Decomposers: Saprotrophs (digest externally via enzyme secretion) Detritivores (digest internally by ingestion)

Question 43

What are the categories of species that have high impacts in food webs and ecological communities more generally?

Answer 43

- Keystone species: species that have a high impact on their community relative to their biomass (sea otters, Pisaster starfish) - Dominant species: species that influence community structure due to their large abundance/biomass (spruce trees in taigas)

Question 44

Define ecological guild

Answer 44

Groups of species that rely on the same resource for survival and reproduction (all dung beetles that feed on dung belong to a guild)

Question 45

Define functional group

Answer 45

Groups of species that are grouped based on their function (dung beetles all eat the same thing but they perform different functions, like burrowers for soil fertilization, rollers to roll dung, and dwellers to decompose organic material)

Question 46

Umana guest lecture presentation main points

Answer 46

- Species interaction beyond direct contact , how that impacts ecosystems, and complexity of food webs - talked about indirect facilitation, trophic cascades (changes at top of food chain trickle down and affect many levels of ecosystem), keystone and dominant species, eco guilds vs. functional groups - did case studies on sea otters and kelp forests, yellowstone wolves, starfish and found that food webs are highly interconnected and changes to one species can lead to cascading effects on others - conservation strategies should recognize keystone species and their roles in maintaining ecosystems