Bio354 exam 2 notes

Black abalone case study

Researchers compared predation pressure between San Nicolas Island (SNI) and San Clemente Island (SCI) to determine whether SCI was suitable for abalone restoration.

Main stressor for black abalone

Climate change is a major stressor, making natural recovery difficult.

Broadcast spawner

An organism that releases eggs and sperm into the water; reproduction can be difficult when population density is low.

Abalone restoration methods

Breed abalone in captivity and release them into the wild, or move them from one location to another.

Translocation

Moving organisms from one location to another to help restore a population.

SCI vs. SNI predation pressure

Predation pressure was higher at SCI than at SNI.

Why was predation higher at SCI?

SCI had higher densities of crab predators.

Tethering experiment

Attaching prey to a tether and placing it in the field to measure relative predation intensity.

Purpose of a tethering experiment

To compare predation rates between locations.

Tethering experiment steps

Attach prey to a tether, place it in the field briefly, record prey loss, and examine remains.

What can prey remains reveal?

The identity of the predator.

Why are tethering experiments short?

Other environmental factors could cause prey mortality if the experiment lasts too long.

Tethering experiment challenge

Tethers may change the natural behavior of prey.

Another tethering challenge

Prey may be removed from the tether by something other than predation.

Tethering experiment solutions

Show that tethered prey behave normally and do not detach for reasons unrelated to predation.

Why use red abalone as a proxy?

Black abalone are federally protected, while red abalone have similar predators and biological traits.

Predated abalone categories

Shell intact, shell damaged, or shell missing.

Main conclusion of the abalone study

Predation pressure was high at SCI, so tethering can help select restoration sites.

Herbivores as predators

Herbivores are considered predators because they consume living organisms.

Numerical response

A change in predator population size caused by a change in prey or food abundance.

Functional response

A change in the number of prey eaten by an individual predator.

Ladybeetle numerical response

Ladybeetle density decreased when cordgrass flowers and pollen were covered and unavailable.

Doomed prey

Prey that are already weak, sick, old, young, or poor competitors and likely to die anyway.

Surplus prey

Healthy prey that are not doomed and may be more important for population regulation.

Life-or-dinner principle

If a predator fails, it misses a meal; if prey fails, it dies.

Why is selection stronger on prey?

Prey risk death while predators usually only lose a meal.

Evolutionary arms race

When predators and prey continually evolve new adaptations against each other.

Lemon drop sea slug defense

Chemicals in the sea slug’s mantle area make it unappealing or harmful to predators.

Learned food aversion

When predators learn to avoid food that made them sick.

Pre-attack defense

A defense that prevents or avoids an attack, such as hiding, retreating, or camouflage.

Post-attack defense

A defense that reduces damage after an attack, such as poison, fortification, or chemical warfare.

Chemical warfare

Using harmful or unpleasant chemicals to deter predators.

Espionage

A prey strategy involving detecting predators by listening, looking, or smelling.

Fortification

Changing body shape, size, or structure to make predation more difficult.

Constitutive defense

A defense that is always present.

When are constitutive defenses favored?

When predation is predictable.

Inducible defense

A defense that is turned on only when a predator or predator cue is detected.

When are inducible defenses favored?

When predation is unpredictable.

Optimal defense theory

The idea that organisms must divide limited resources between growth, reproduction, and defense.

Defense trade-off

More energy used for defense leaves less energy for growth and reproduction.

Induction period

The period when prey are exposed to predator cues so a defense can develop.

Bioassay period

The period when researchers test whether the induced defense actually works.

How are inducible defenses studied?

Expose prey to predator cues or no cues, allow time for defenses to develop, then compare predation.

Scenedesmus defense

Freshwater algae can form colonies that are harder for Daphnia to eat than individual cells.

Phaeocystis defense

Phaeocystis changes between single cells and large colonies depending on the predator.

Enemy-specific defense

A defense that changes depending on which predator is present.

Large Phaeocystis predator response

Chemical cues from a large predator suppress colony formation.

Small Phaeocystis predator response

Chemical cues from a small predator increase colony formation.

Context dependency

The effect of a predator cue depends on conditions such as prey density, habitat, or prey size.

Urchin predator response

Sea urchins may hide or move away when they detect lobster predators.

Urchin density and predator cues

Urchin responses to predators can change depending on how many urchins are present.

Quorum sensing

A group response in which organisms respond based on the presence or density of nearby individuals.

Urchin size and predator response

Smaller urchins may respond differently because they are easier for predators to eat.

Snail habitat response

Snails may be more afraid of predators in barnacle habitats than in mussel habitats.

Why are barnacle habitats higher stress?

Barnacle habitats may provide fewer places for snails to hide.

Why are mussel habitats lower stress?

Mussel habitats provide more hiding places for snails.

Chemical predator cues

Marine inducible defenses are often triggered by chemicals released by predators.

Problem with lab mesocosms

Lab conditions may not accurately represent natural flow rates, predator densities, or chemical signals.

Trophic cascade

An indirect effect that moves through several levels of a food web.

Density-mediated indirect interaction (DMII)

An indirect interaction caused by changes in the population density of a species.

DMII example

An otter reduces sea urchin density, which allows kelp abundance to increase.

Trait-mediated indirect interaction (TMII)

An indirect interaction in which one species changes a trait of another species, which then affects a third species.

TMII example

A crab scares snails, causing them to hide and eat less seaweed, allowing seaweed to increase.

TMII traits

Traits involved in TMIIs can be behavioral, morphological, or chemical.

Why can fear affect communities?

Predator fear can change prey behavior, food webs, nutrient cycling, and plant growth.

Fear and nutrient cycling

Scared prey may eat different plants, and their bodies can affect soil microbes and carbon dioxide production.

Facilitation

An interaction in which one species benefits while the other is unharmed or also benefits.

Mutualism

An interaction in which both species benefit.

Obligatory mutualism

A mutualism required for the survival of one or both species.

Facultative mutualism

A mutualism that is helpful but not required for survival.

Specialist mutualist

A mutualistic species that has only one or a few suitable partners.

Generalist mutualist

A mutualistic species that can interact with many different partners.

Ant-acacia mutualism

Ants receive food and shelter, while acacia plants receive protection from herbivores.

Acacia plant benefit from ants

Protection from herbivorous insects.

Ant benefit from acacia plants

Food from Beltian bodies and nectaries.

Ant removal experiment

Researchers removed ants from some acacia plants and compared them with plants that still had ants.

Result of ant removal

Plants without ants had more herbivorous insects and performed worse.

Mycorrhizal mutualism

Plants receive nutrients from fungi, while fungi receive sugars from plants.

Plant benefit from mycorrhizae

Nutrients such as nitrogen and phosphorus.

Fungi benefit from plants

Energy in the form of photosynthate or plant sugars.

Coral-zooxanthellae mutualism

Coral receives energy, while zooxanthellae receive a habitat.

Coral bleaching

The expulsion or loss of zooxanthellae from coral tissue.

Plant-pollinator mutualism

Animals receive food, while plants receive pollination.

Seed dispersal mutualism

Animals receive food, while plants have their seeds dispersed.

Yucca-yucca moth mutualism

Moths receive food from yucca seeds, while yucca plants receive pollen dispersal.

Yucca plant strategy against cheating

The plant aborts fruits when moth larvae eat too many seeds, killing the larvae.

Yucca moth strategy against plant abortion

Female moths avoid laying eggs on plants where another female has already laid eggs.

Mutualism cheating

When one partner receives benefits without providing the expected benefit.

Cleaner fish mutualism

Cleaner fish remove parasites from larger fish and receive food.

Cleaner fish mimic

A fish that resembles a cleaner fish but bites visiting fish instead of removing parasites.

Why be careful with commensalism?

It may be difficult to know whether the supposedly unaffected species is truly unaffected.

Hyperiella and Clione interaction

The amphipod carries a chemically defended sea angel, gaining protection from predators.

Stress gradient hypothesis

The type and strength of an interaction can change depending on environmental stress.