Chapter 15- Mutualism & Commensalism

Some positive interactions are highly species-specific and obligate, meaning?

(not optional for either species).

Which statement about the evolution of mutualisms and commensalisms is true? Host-parasite relationships can evolve into commensalisms. Host-parasite relationships can evolve into mutualisms. Parasites and hosts often coevolve. All of the above

All the above

The fungus penetrates the cell walls of some root cells, forming a branched network called an arbuscule.

Arbuscular mycorrhizae

positive interactions may be more common in stressful environments. Why?

Because environmental conditions tend to be more extreme at high-elevation sites

individuals that increase offspring production by overexploiting their mutualistic partner.

Cheaters ----interaction will not persist.

Commensialism is ALWAYS facultative for the species that does not benefit, and does not ________?

Coevolve.

Individuals of one species benefit; individuals of the other species do not benefit but are not harmed(+/0 relationship

Commensialism

The fungus grows between root cells and forms a mantle around the root.

Ectomycorrhizae

he partners in a mutualism are altruistic T/F?

False.

One partner provides the other with shelter, living space, or favorable habitat.

Habitat mutualism

What does it mean when a facultative interaction happens?

It is not obligatory, and it does NOT coevolve.

Which statement about fig-fig wasp association is true? These interactions show clear signs of coevolution. These interactions are facultative. On balance, only the wasp benefits from this relationship. On balance, only the fig benefits from this relationship.

These interactions show clear signs of coevolution

Mutualist receives energy or nutrients from its partner.

Trophic mutualism

What is an example of species-specific and obligate positive reaction?

Tropical figs are pollinated by fig wasps .•The wasps and the figs have coevolved and neither species can reproduce without the other. •The wasps have complex reproductive behaviors in the fig receptacle that ensures pollination. Wasp larvae develop by eating some of the fig seeds.

But parasites and hosts often coevolve,each in response to selection pressure imposed by the other. T/F?

True

Mutualism can arise from a host-parasite interaction. T/F?

True

Symbioses can include parasitism (+/-), commensalism (+/0), and mutualism (+/+) T/F?

True

EX: In high-nutrient environments, plants can easily get nutrients and may reduce the carbohydrate reward to mycorrhizal fungi.

WHY: The costs of supporting the fungus become greater than the benefits that the fungus can provide.

Groups of dominant species (such as trees in a forest) commonly determine________ of other species by providing habitat.

distributions

A fungus increases the ability of a plant to grow under high-salt conditions. For the plant, this association is a _______ mutualism .a.Trophic b. Formic c. Chemical d. Habitat

habitat

At high-elevation sites, neighbors also tended to

increase survival and reproduction of the target species.

When one species provides another with favorable habitat, it

influences the distribution of that species.

Most plants form symbiotic associations between the roots and various fungi called:

mycorrhizae

RNE was generally ______ at low-elevation sites.

negative

For a mutualism to evolve, net benefits must exceed:

net costs.

RNE was generally _______ at high-elevation sites: neighbors had a positive effect on the target species.

positive

Sometimes there is a cost to one or both partners, but the net effect is what for mutualistic/commensialistic interactions?

positive +

Is a deer or moose consume seeds of herbaceous plants. Many seeds pass through unharmed and are deposited with feces. Thus, it becomes a dispersal mechanism. Such intentions are:

sporadic and facultative; there is little evidence to suggest that the species have coevolved.

Which of the following is the most important criterion for determining whether an ecological relationship is a symbiosis? a. Whether both parties benefit b. Whether the parties are from the same kingdom c. The degree of proximity between the two parties d. The number of parties in the interaction

the degree of proximity between the two parties.

Corals form a mutualism with symbiotic algae

zooxanthellae

For each species, the benefits are

> than the costs

Mutually beneficial interaction between individuals of two species (+/+ relationship).

Mutualism

Which statement about mycorrhizae is true Although mycorrhizae are very common in angiosperms, most gymnosperms do not form these associations. Mycorrhizae are symbiotic associations between plant roots and fungi. Mycorrhizae typically are commensalisms, not true mutualisms, because only the plant benefits. Both a and b

Mycorrhizae are symbiotic associations between plant roots and fungi.

of a target species with neighbors present is compared to performance when neighbors are removed

Performance

one or both species benefit and neither is harmed.

Positive Interactions

target species'performance with neighbors present minus its performance with neighbors removed.

Relative neighbor effect

One partner performs an ecological service for the other.

Service mutualisms.

Two species live in close physiological contact with each other

Symbiosis