Chapter 27

Which three animals are ruminants?

- Giraffes - Cattle - Camels

Which three statements describe a host-parasite relationship?

- The parasite must benefit. - The parasite must coexist with the host, at least temporarily. - The host must be harmed.

Which two mechanisms are examples of contact-independent growth inhibition?

- secretion of bacteriocins - secretion of toxin-bearing outer membrane vesicles

Termites are dependent on their endosymbionts to carry out which two processes?

1. convert (fix) nitrogen to a usable form 2. complete the digestion of cellulose

In the association of the dinoflagellate Symbiodinium with reef building corals, the benefit to Symbiodinium is

1. nitrogenous compounds 2. protection from ultraviolet light

If an aphid is treated with an antibiotic, it dies. Which is the best explanation for this observation?

Aphids harbor obligate mutualistic bacteria.

Identify the common characteristic of cooperation and mutualism.

Both are symbiotic relationships

Which statement regarding cheaters is false?

Cheaters pay the energetic cost for synthesizing the compound. (they don't!)

Which statement regarding symbiosis is false?

Symbiotic associations typically have a negative impact on one of the species involved. Shifting environmental conditions may impact the benefit or harm of a symbiotic interaction. Symbiosis refers to stable associations of one organism with another.

In coral bleaching, which microbial component of the coral holobiont is affected?

The endosymbiotic photosynthetic dinoflagellates

Which statement regarding syntrophy is false?

The flow of nutrients from heterotrophs to autotrophs is an example of syntrophy.

In the termite gut, protists ferment cellulose to acetate, CO2, and H2. The acetate is the termite's preferred carbon source, and the CO2 and H2 are used by bacterial symbionts to produce more acetate by the

Wood-Ljungdahl pathway

Aggregations of many types of organisms in stable relationships are now often referred to as ________ or _________

a super organism or a holobiont

An example of an obligatory symbiotic interaction is

a virus because it absolutely requires a host cell for replication

Because of the environmental conditions in the rumen, all microbes present must function efficiently under ______ conditions

anaerobic

Antimicrobial chemicals synthesized by bacteria to act against closely related strains are termed

bacteriocins

In the Xenorhabdus nematophila - Steinernema carpocapsae symbiosis, the organism X. nematophila is a(n)

bacterium

The loss of photosynthetic pigments from the endosymbiotic photosynthetic dinoflagellates of coral, or the complete expulsion of dinoflagellates from the coral, is called coral

bleaching

In a mutualistic symbiosis, the two partners

cannot survive if separated

A subpopulation of bacteria that avoids producing and secreting a chemical compound that benefits the entire population is termed

cheaters

When different organisms within a population or community try to acquire the same resource, this is called

competition

In antagonistic relationships, the source of conflict between the partners is typically

competition for resources

The two general mechanisms for offensive action against neighboring microbes are

contact-dependent and contact-independent

A symbiotic relationship in which each partner receives some benefit, but each partner can also live independently is called _________

cooperation

The Xenorhabdus nematophila - Steinernema carpocapsae symbiosis is best classified as

cooperation

Ruminants are said to have an "eat now, digest later" strategy, because after feeding on grasses, they spend vast amounts of time chewing a small ball of partially digested grasses called their

cud

Aphids and Buchnera aphidicola bacteria are obligate mutualistic symbionts. Therefore, if the bacterial partner is separated from the insect and placed in a culture medium, the expected result would be that the bacteria would

die.

In a facultative symbiotic interaction between two species of bacteria,

each individual species is capable of growth in the absence of the other

A predatory bacterium that enters its prey's periplasm and consumes its energy and precursors is termed a(n) ______ predator

endobiotic

The contribution of the rumen microbial community to plant digestion in a ruminant animal is

enzymes to degrade a variety of plant polymers

A predatory bacterium that attaches to its prey's surface and releases degradative enzymes to lyse the prey cell is termed a(n) ______ predator.

epibiotic

In the association of reef building corals with the dinoflagellate Symbiodinium, the benefit to the coral is

fixed carbon

The predation of bacteria by heterotrophic protozoans is termed

grazing

The image shows Umbilicaria, a lichen. The arrow indicates a layer of (green top layer)

green algae

The combined "organism" that is an association between fungi and either green algae or cyanobacteria is called a(n)

lichen

Endosymbiotic photosynthetic dinoflagellates are often the basis for the food chain in many

marine invertebrates

A common microbial defense against antagonism is

mutualism

An obligatory symbiotic relationship in which each partner receives some benefit and each partner is dependent on the other is termed

mutualism

Mutualistic relationships between microbes and insects are common because insects

often consume diets lacking essential nutrients

An antagonistic interaction in which one partner obtains biochemical precursors and energy from a living victim is termed

parasitism

An endosymbiotic relationship where one partner benefits and one is harmed, but also involves at least a temporary state of coexistence is called

parasitism

The coral holobiont has endosymbiotic ______ as the basis for its food chain

photosynthetic dinoflagellates

An antagonistic interaction in which one partner obtains biochemical precursors and energy after killing a victim is termed

predation

In the termite gut, protists ferment cellulose to acetate, CO2, and H2. The acetate is the termite's preferred carbon source, and the CO2 and H2 are used by bacterial symbionts to

produce more acetate

In the termite gut, protists ferment cellulose to acetate, CO2, and H2. The acetate is the termite's preferred carbon source, and the CO2 and H2 are used by bacterial symbionts toIn the termite gut, protists ferment cellulose to acetate, CO2, and H2. The acetate is the termite's preferred carbon source, and the CO2 and H2 are used by bacterial symbionts to

produce more acetate

Termites are aided in the digestion of wood by ______ that complete lignocellulose degradation and by ______ that fix atmospheric nitrogen

protists / bacteria

In mutualistic associations between microbes and insects, the microbe generally receives

secure habitat and ample nutrients

Historically, the smaller organism in a symbiotic relationship was termed the ______ and the larger organism the ______. Currently, these two organisms are now regarded as partners

symbiont / host

A symbiotic association in which one species benefits from the metabolic products of another is called

syntrophy

The rumen has a slightly higher _____ than the rest of the animal

temperature

In the Xenorhabdus nematophila - Steinernema carpocapsae cooperative symbiosis, the advantage to Steinernema is that

the bacteria facilitate its reproduction

The enzymes to hydrolyze complex plant polymers consumed by a ruminant animal derive from ________

the diverse microbial rumen community

Protozoans grazing on bacteria is an important component of food webs, as it is the primary mechanism to

transfer carbon and energy from bacteria to more complex organisms

A mature aphid contains millions of Buchnera aphidicola cells, located ______

within specialized cells called bacteriocytes