mutualism

What are the two main ways to categorize mutualisms?

Degree of dependency and commodities exchanged.

What is an obligate mutualism?

A relationship in which populations go extinct without their partner.

What is a facultative mutualism?

A relationship in which populations can persist without their partner.

What are the three commodities exchanged in mutualisms?

Transport; acquisition of energy and nutrients; protection and defense.

What is transport mutualism?

One species provides transportation for another species' reproduction or dispersal.

What is pollination mutualism?

Plants receive transport of their gametes, while pollinators receive food such as nectar.

What is seed dispersal mutualism?

Plants have their seeds transported, while animals receive food from fruit.

What are the benefits of seed dispersal to plants?

Reduces competition between parent and offspring, provides access to new habitats, and increases gene flow.

What is an example of seed dispersal mutualism?

Black bears eat manzanita fruit, and seeds survive gut passage and are deposited away from the parent plant.

Why are introduced birds not necessarily replacing extinct native Hawaiian seed dispersers?

They have different traits, and many native seeds are too large for introduced birds to disperse.

What is nutrient acquisition mutualism?

A relationship in which organisms exchange nutrients or energy.

What do plants and nitrogen-fixing bacteria exchange?

Plants receive usable nitrogen, while bacteria receive sugars and a place to live in root nodules.

What do plants and mycorrhizal fungi exchange?

Plants receive nutrients and water, while fungi receive sugars.

What do corals and algae exchange?

Corals receive energy-rich products from photosynthesis, while algae receive shelter, carbon dioxide, and nutrients.

What do Hawaiian cave-adapted planthoppers receive from bacteria?

Essential amino acids that are missing from their sap diet.

Why are cave-adapted planthoppers dependent on bacteria?

They require bacterial symbionts to synthesize necessary amino acids.

What is protection and defense mutualism?

A relationship in which one species provides protection or defense while receiving benefits in return.

What do ants receive from acacia plants?

Food (Beltian bodies and nectar) and a place to live in hollow thorns.

What do acacia plants receive from ants?

Protection from herbivores.

What can happen to acacia plants without ants?

They can die within 6–12 months.

What do pistol shrimp and gobies exchange?

The shrimp provides a burrow for shelter, while the goby acts as a lookout and warns of predators.

What do yucca plants receive from yucca moths?

Pollination.

What do yucca moths receive from yucca plants?

Food and a place for their offspring to develop; larvae eat some developing seeds.

Is the yucca plant and yucca moth relationship obligate or facultative?

Obligate; both require the other to reproduce.

What are the costs of mutualism?

Each species must invest energy or resources to provide benefits to its partner.

What does it mean that mutualisms are based on self-interest?

Each species cooperates because the benefits it receives exceed the costs of giving.

Why is mutualism not altruism?

Both species benefit from the relationship rather than one sacrificing itself for another.

What is altruism?

Sacrificing oneself or one's own benefit for another's benefit.

What is cheating in mutualism?

Receiving benefits without paying the cost or providing the expected benefit in return.

What is an example of cheating in pollination?

Nectar robbing, when an animal takes nectar without effectively pollinating the flower.

How do yucca moths cheat?

They lay too many eggs, causing larvae to consume too many developing seeds.

How do yucca plants prevent cheating?

They can stop flower development when moths lay too many eggs.

What does it mean that species interactions occur on a continuum?

Interactions are not always strictly mutualistic, competitive, or exploitative; their outcomes can fall between these categories.

How do yucca moths demonstrate a continuum of interactions?

Six or fewer eggs per flower can result in benefits exceeding costs for the plant, while nine or more eggs can cause costs to exceed benefits.

What happens when yucca moths lay nine or more eggs per flower?

They eat too many seeds, making the relationship exploitative from the plant's perspective.

What does context-dependent mean?

The type or outcome of a species interaction depends on environmental conditions.

What happened to four bacterial species in a harsh, toxic environment?

They benefited from one another; together they survived and degraded toxic industrial fluids.

What environmental conditions promoted positive bacterial interactions?

High toxins and low nutrients.

What happened to bacteria in a benign environment?

They began competing when survival became easier, such as with low toxins and high nutrients.

What does the bacterial toxicity experiment demonstrate?

The same species can cooperate in one environment and compete in another.

What is bioremediation?

Using living organisms to process waste and clean up pollution.

What do leaf-cutter ants use collected plant material for?

They use it to grow fungi that they eat.

What do leaf-cutter ants and fungi exchange?

Ants provide plant material and a protected growing environment; fungi provide food.

What additional organisms are involved in the leaf-cutter ant mutualism?

Fungal parasites and bacteria associated with ants.

What do ant-associated bacteria do?

They produce antimicrobial compounds that suppress fungal parasites attacking the food fungus.

What did Cafaro et al. (2011) find about ant-associated bacteria?

They had approximately a 23 mm zone of inhibition compared with approximately 17 mm for free-living control bacteria.

What is a complex web of species interactions?

An ecological system involving multiple mutualists, competitors, and exploiters rather than only two interacting species.

What does N represent in an N vs. t graph?

Population size.

What does t represent in an N vs. t graph?

Time.

What happens to two competing species when grown together compared with separately?

Both generally have lower population sizes together because competition negatively affects both.

What happens to two mutualistic species when grown together compared with separately?

Both generally have higher population sizes together because both benefit.