Living together

What is community structure?

The richness and evenness of genetic, species, and functional diversity in a biological community.

What is community composition?

The identity of the organisms (species, OTUs, functional groups) that make up a community.

What are functional groups?

Sets of species with similar effects on ecosystem processes and similar environmental responses.

What is functional redundancy?

When different species perform the same ecological role, increasing ecosystem resilience.

How does genetic diversity affect ecosystem function?

Higher genetic diversity supports more traits and adaptations, enhancing ecosystem resilience and stability.

What is evenness in a community?

The relative abundance of species or functional groups, indicating how balanced a community is.

What is the relationship between biodiversity and ecosystem function?

Greater biodiversity leads to better ecosystem functioning, stability, and r

What is a keystone species?

A species that has a disproportionately large effect on its ecosystem relative to its abundance (e.g., Pisaster starfish).

What ecosystem processes are essential for ecosystem function?

Energy flow, carbon/nutrient cycling, water transfer, and decomposition.

How does biodiversity support ecosystem services?

It enhances services like productivity, stability, resistance to disturbance, and resource recovery.

Why are bats significant in the study of infectious diseases?

Bats are reservoirs for many zoonotic viruses (e.g. SARS, Ebola, Nipah) and may harbor more viruses per speciesthan other mammals.

What are zoonotic viruses?

Viruses that can transmit from animals to humans, often causing emerging infectious diseases.

What is white-nose syndrome?

A fungal disease (Pseudogymnoascus destructans) causing mass mortality in hibernating bats in North America.

What is one reason bats may tolerate viruses better than other mammals?

Bats have dampened immune responses, likely evolved to manage inflammation from flight.

How does bat physiology influence viral infection?

Flight raises body temperature like a fever, possibly reducing viral loads; hibernation may prolong virus incubation.

What ecological traits make bats good virus transmitters?

Large colonies, long lifespan, flight, and seasonal breeding increase contact rates and viral spread.

What is “trait-based analysis” in bat-virus research?

Linking bat life-history traits (e.g. sociality, migration) to patterns of viral transmission and sharing.

Do bats have a disproportionately high number of zoonotic viruses?

Studies show they host many viruses, but this may reflect their high species richness, not unique biology.

How does seasonality affect virus dynamics in bats?

Seasonal birth pulses increase juvenile populations, boosting transmission and possibly virus persistence.

Why is understanding bat-virus dynamics important?

It helps predict spillover risks, guide surveillance, and inform public health strategies.

What are life-history traits?

Traits that affect an organism’s schedule of birth and death, such as reproduction timing and lifespan.

What is the principle of allocation?

Resources are limited, so investment in one trait (e.g. offspring number) reduces resources available for others (e.g. survival).

What is a life-history trade-off?

A compromise between conflicting demands, such as reproducing many offspring vs. surviving longer.

What are the two reproductive strategies in terms of frequency?

Semelparity (reproduce once) and iteroparity (reproduce multiple times).

What is reproductive value?

A measure of how much an individual of a given age contributes to future population growth.

What are the traits of an r-selected species?

Small, short-lived, early maturity, many small offspring (e.g. cod, insects).

What are the traits of a K-selected species?

Large, long-lived, late maturity, few large offspring (e.g. elephants, whales).

What does a Type I survivorship curve show?

High survival in early life, most individuals die in old age (e.g. humans).

Why can't organisms maximize all fitness traits at once?

Biological constraints and resource limitations prevent a "Darwinian Demon."

How are life-history strategies distributed in nature?

Along a continuum between r and K extremes, not as strict categories.

What defines a population in ecology?

A group of individuals of the same species in a specific place and time, interacting with each other.

What are three common methods to estimate population size?

Total count, sampling (e.g. quadrats, transects), and mark-recapture.

What is the key assumption of the mark-recapture method?

The population is stable, and marked individuals mix randomly, marks are retained, and don’t affect survival.

What is population structure?

The age and sex composition of a population, which affects growth and dynamics.

What is a life table?

A summary of birth and death rates by age, used to calculate population growth rates.

What is the difference between horizontal and vertical life tables?

Horizontal = follow a cohort over time; Vertical = sample age structure at one point in time.

What is exponential growth?

Growth where population size increases continuously and rapidly (J-shaped curve), assuming no resource limits.

What is logistic growth?

Growth that slows as the population approaches a carrying capacity (K) due to limited resources (S-shaped curve).

What is density-dependent regulation?

Birth or death rates change with population density, helping stabilize population size.

What caused the population decline of peregrine falcons in the 1960s–70s?

DDT contamination, which led to eggshell thinning and low hatching success.

What is a metacommunity?

A set of local communities linked by dispersal of multiple, potentially interacting species.

What are local vs. regional diversity?

Local = species diversity within a site; Regional = diversity across all sites in a metacommunity.

What does species sorting suggest?

Community composition is driven mostly by local environmental conditions, with limited impact from dispersal.

What are mass effects in metacommunities?

High dispersal allows species to persist in poor habitats via rescue effects, overriding environmental filtering.

What does the neutral theory propose?

All species are ecologically equivalent, and community structure is shaped by random births, deaths, and dispersal.

How does dispersal level affect diversity patterns?

Low = high regional, low local richness; Intermediate = both high; High = homogenisation, lowering diversity.

What is an example of a natural metacommunity system?

Interconnected rock pools, lagoons, or coral reef networks connected via water and larval dispersal.

How does fragmentation affect metacommunities?

It limits dispersal, reducing recolonization and potentially decreasing diversity.

Why is metacommunity theory useful in conservation?

It helps design connected networks like Marine Protected Areas that maintain species flow and ecosystem resilience.

How does metacommunity theory apply to disease ecology?

Host microbiomes or infection sites act as local communities, and bacterial dispersal shapes overall metacommunity dynamics.

What is the difference between migration and dispersal?

Migration is predictable, round-trip movement between habitats; dispersal is a one-way movement from birth site to another area.

What is natal dispersal?

Movement from the birth site to the first breeding site, often performed by juveniles.

What is breeding dispersal?

Movement between breeding sites, more common in females than males.

What are the benefits of dispersal?

Avoid inbreeding, local competition, and maintain genetic diversity.

What is a metapopulation?

A group of spatially separated populations of the same species connected by dispersal.

What is source-sink dynamics in metapopulations?

Source habitats produce excess individuals that disperse to sink habitats, which cannot sustain populations on their own.

What is migratory connectivity?

The degree to which breeding and nonbreeding areas are linked by individual migratory paths.

What is philopatry?

The tendency of individuals to remain in or return to their birthplace.

How does migration affect distribution?

Migration can lead to shifts, e.g. northward movement of birds due to climate change.

Why is connectivity important in conservation?

It allows recolonisation of local extinctions and increases regional population stability.

What are the four main types of species interactions?

Competition, predation (including herbivory and parasitism), commensalism, and mutualism.

What is the competitive exclusion principle?

Two species cannot coexist if they occupy the exact same niche and compete for identical resources.

What is an example of coexistence due to resource partitioning?

Similar species use different resources or niches, reducing direct competition (e.g. different root depths or diets).

What is character displacement?

Evolutionary change in traits due to competition, helping similar species avoid overlap (e.g. beak size in birds).

What do the Lotka-Volterra equations model?

Interactions such as competition and predator-prey dynamics, showing effects on population growth.v

What is a classic example of predator-prey oscillation?

Lynx and snowshoe hare populations show cyclical patterns due to density-dependent interactions.

What is a refuge in predator-prey dynamics?

A safe area or condition allowing prey to avoid being eaten, helping predator and prey coexist.

How do parasites and herbivores compare to predators?

They often cause similar population effects, including cycles and regulation of host or plant abundance.

What defines commensalism?

One species benefits, the other is unaffected (e.g. birds nesting in trees).

What is mutualism?

Both species benefit (e.g. pollination or gut microbiota), and mutualists can regulate each other’s populations.

What defines a community in ecology?

An assemblage of interacting populations of different species living in the same place at the same time.

What are the two key components of biodiversity?

Species richness (number of species) and evenness (relative abundance of each species).

What is a trophic structure?

The feeding relationships between species in a community, often represented as food chains or webs.

What spatial pattern is seen in species diversity?

Higher diversity at lower latitudes (near the equator); it decreases with elevation, aridity, and depth.

What is succession in community ecology?

A temporal pattern of species replacement over time, often following disturbance or habitat change.

What does the Equilibrium Theory of Island Biogeography predict?

Species richness is determined by island size (extinction risk) and isolation (colonization rate).

What is a keystone species?

A species with a disproportionate effect on community structure, such as Pisaster starfish in rocky shores.

How does habitat complexity affect diversity?

More complex habitats support higher species diversity by providing more niches.

What is the Intermediate Disturbance Hypothesis?

Species diversity is highest at intermediate levels of disturbance.

What’s the difference between top-down and bottom-up control?

Top-down = predators regulate lower levels; bottom-up = resource availability (e.g. nutrients) drives community structure.

What is the Competitive Exclusion Principle?

Two species competing for the same resource cannot coexist indefinitely under stable conditions.

What is the Paradox of the Plankton?

Many species coexist in resource-limited, mixed environments like water drops—contradicting exclusion theory.

What is the Intermediate Disturbance Hypothesis (IDH)?

Species diversity is highest at intermediate levels of disturbance due to coexistence of r- and K-strategists.

What are the three main characteristics of a disturbance?

Magnitude, frequency, and duration.

What happens at low disturbance levels?

Competitive exclusion occurs—K-strategists dominate, and diversity is low.

What happens at high disturbance levels?

Only fast-colonizing (r-strategist) or highly tolerant species survive—again reducing diversity.

What is an example supporting IDH in nature?

Intertidal boulders: small (frequent disturbance) = 1 species, large (rare disturbance) = 2, intermediate = most diverse.

How can non-equilibrium conditions promote diversity?

Fluctuations prevent dominance by a single species, allowing multiple species to coexist.

How does nutrient pulsing influence competition?

It allows both fast-growing (r) and efficient competitors (K) to coexist by disrupting steady competition.

Is IDH still accepted?

While still useful, it's now part of a broader understanding of how disturbance, traits, and environment interact.

What defines symbiosis?

A close, long-term association between two species, which may be mutualistic, commensal, or parasitic.

What is mutualism?

A type of symbiosis where both species benefit, e.g. ants and Acacia trees.

What is brood parasitism?

When one species lays its eggs in the nest of another, leaving the host to raise its young (e.g. cuckoos, honeyguides).

What are key cuckoo adaptations for brood parasitism?

Mimicked eggs, fast development, egg removal, host chick ejection, and manipulative begging.

What is the Red Queen Hypothesis in this context?

An evolutionary arms race between brood parasites and hosts, where both evolve new strategies to outcompete the other.

What is a parasitoid?

An organism (often an insect) that kills its host as part of its lifecycle, e.g. parasitic wasps.

What’s the difference between a parasite and a parasitoid?

A parasite harms but doesn’t usually kill the host; a parasitoid always kills the host.

How do parasitoids act as plant defenders?

Plants release volatile chemicals that attract parasitoids to herbivores feeding on them.

What is social parasitism (e.g. dulosis)?

One species enslaves members of another to work for them, as in some ant species.

Why is brood parasitism evolutionarily beneficial to the parasite?

It increases fecundity by allowing the parasite to invest more in egg production than parental care.