Chapter 57: Species Interactions (Part 1, Week 4)

Question 1

What do you call the various ways in which a species can interact with other species, such as predation, competition, parasitism, mutualism, and commensalism; part of the study of population ecology?

Answer 1

Species interactions

Question 2

What is an interaction that affects two or more species negatively, as they compete over food or other resources?

Answer 2

Competition (-/-)

Question 3

What is a one-sided competition between species, in which the interaction is detrimental to one species but not to the other?

Answer 3

Amensalism (-/0)

Question 4

What are the three effects that have a positive effect on species and a negative effect on the other (+/-)? And what do they mean?

Answer 4

Predation, herbivory, and parasitism

Predation - An interaction in which the action of a predator results in the death of its prey.

Herbivory - A form of species interaction in which herbivores feed on plants.

Parasitism - A symbiotic association in which one organism feeds off another but does not normally kill it.

Question 5

What is a symbiotic interaction in which both species benefit? (+/+)

Answer 5

Mutalism

Question 6

What is an interaction that benefits one species and leaves the other unaffected? (+/0)

Answer 6

Commensalism

Question 7

[Start 57.1 Competition]

What are the different types of competition that ecologists have identified? What do these two different types mean?

Answer 7

Intraspecific competition - Competition between individuals of the same species.

Interspecific competition - Competition between individuals of different species.

Question 8

What is a way that competition can exist by the mechanism by which it occurs like when organisms compete indirectly through the consumption of a limited resource, with each obtaining as much as it can?

Answer 8

Exploitation competition.

For example, when fl y maggots compete ina mouse carcass, not all the individuals can command enough of theresource to survive and become adult fl ies.

Question 9

What is a competition in which organisms interact directly with one another by physical force or intimidation?

Answer 9

Interference competition

Often this force is ritualized into aggressive behavior associated with territory. In these cases, strong individuals survive and take the bulk of the resources, and weaker ones perish or, at best, survive under suboptimal conditions.

Question 10

How do you classify competition between vultures feeding on roadkills?

Answer 10

Individual vultures often fight one another over small carcasses. These interactions constitute intraspecific interference competition.

Question 11

What is an example of competition between species not being equal? Think of spartina and how plants compete for soil and sunlight.

Answer 11

Many plant species compete for natural resources such as water and sunlight. To give themselves an advantage, some species produce and secrete chemicals from their roots that inhibit the growth of other species.

For example, diffuse knapweed, an introduced species, secretes root chemicals called allelochemicals into the surrounding environment that kill the roots of native grass species—a phenomenon called allelopathy.

(The suppression of growth of one species due to the release of toxic chemicals by another species.)

Question 12

In 1983, American ecologist Joseph Connell reviewed field studies that discovered competition was in found in what percentage of the 215 species surveyed?

What was the competition rate where single pairs of species utilizing the same resource? What about when studies involved more species?

Answer 12

55%

90%

50%

These are percentages of cases observed.

Why should this be the case? Imagine a resource such as a series of different-sized grains that has four species—ants, beetles, mice, and birds—feeding on it.

The ants feed on the smallest grains, the beetles and mice on the intermediate sizes, and the birds on the largest. If only adjacent species compete with each other, competition is expected to occur only between ant and beetle, beetle and mouse, and mouse and bird. Thus, competition occurs in only three out of the six possible species pairs (50%).

Question 13

T/F Animals have a higher degree for competition than plants.

Answer 13

False. Plants were observed to have a higher degree of competition probably because they connot escape or move. Same thing for marine animals in intertidal zones.

Question 14

What is one way two species can coexist? And what does it mean?

Answer 14

If they do not occupy the same niche.

Niche - The unique set of habitat resources a species requires as well as its effect on the ecosystem.

Question 15

What was significant about when Russian microbiologist Georgyi Gause studied the competition of three protist species, Paramecium aurelia, Paramecium bursaria, and
Paramecium caudatum?

Specifically, highlight main points of the study.

Answer 15

1. They all feed on bacteria ad yeast.
2. When Gause cultured P. caudatum and P. aurelia
   together, P. caudatum eventually went extinct. Both species utilized bacteria as food, but P. aurelia
   grew at a rate six timesfaster than P. caudatum.
3. However, when Gause cultured P. caudatum
   and P. bursaria together, neither went extinct.
4. P. bursaria have tiny green algae inside them, which produce oxygen and allow P. bursaria
   to survive in the lower oxygenlevels at the bottom of the tubes.
5. These are different niches since bursaria was at the lower levels and caudatum was at the higher levels.

Question 16

What is the idea that two species with the same resource requirements cannot occupy the same niche? This was discovered by Gause with the experiment involving three different protists.

Answer 16

Competitive exclusion principle

Question 17

What is the differentiation of niches, both in space and time, that enables similar species to coexist in a community?

Answer 17

Resource partitioning, just as the five species of warblers feeding in different parts of a spruce tree.

We can think of resource partitioning as reflecting the results of past competition, in which competition leads the inferior competitor to eventually occupy a different niche.

Question 18

[Bonus] Do you think these results for passerine birds are typical for most other species? For example, do most other species segregate by habitat?

Answer 18

In 1974, Tom Schoener examined segregation in a more wide-ranging literature review of over 80 species, including slime molds, mollusks, and insects, as well as birds. He found segregation by habitat occurred in the majority of the examples, 55%. The second most common form of segregation was by food type, 40%.

Question 19

What was another way for different species to coexist, not involving niche, but something else?

Answer 19

Variation in morphological features that affects their ability to utilize resources.

In 1959, British-born American biologist G.Evelyn Hutchinson examined the sizes of mouthparts or other bodyparts important in feeding and compared their sizes across species that were sympatric
(occurring in the same geographic area) and allopatric
(occurring in different geographic areas).

Hutchinson hypothesized that when two species are sympatric, each species will tend to specialize on different types of food. This specialization may be associated with differences in the size of body parts used for feeding, also called feeding characters.

Question 20

What is the tendenancy for two species to diverge in morphology and thus resource use because of competition?

Answer 20

Character displacement

Question 21

What was the percentage that Hutchinson proposed that could be used as an indication of the amount of difference necessary to permit two species to coexist?

Answer 21

30%. Think finches, galapogos islands, and beak depth.

Question 22

What is the optimal range of conditions in which a particular species functions best?

Answer 22

Fundamental niche

Question 23

What is the actual range of an organism in nature, when some part of the fundamental niche is occupied by a competitor? This is the area where the competitor is absent.

Answer 23

Realized niche

Question 24

What is one of the best methods of determining an organism’s fundamental niche?

Answer 24

Remove one of the competing species and exame the effect on the other species.

EXAMPLE

A now-classic example of this method involved a study of the interactions between two species of barnacles conducted on the west coast of Scotland and the resilience to desiccation.

Question 25

[Start 57.2 Predation, Herbivory, and Parasitism]

Since Predation, Herbivory, and Parasitism are interactions that have a positive effect for one species and a negative effect for the other, how are they classified? (2)

Answer 25

1. How lethal they are for the prey or host

2. The length of association between the consumer and prey

Question 26

What two strategies (predation, herbivory, and parasitism) is nonlethal?

Answer 26

Herbivory and parasitism

Question 27

What has common features with predators (who kill their prey) and parasites (who leech off their prey but do not kill it, like a tick)?

Answer 27

Parasitoids

Like parasitic wasps, they do kill their prey by laying eggs in their prey but incredibly slow death.

Question 28

T/F Some organisms can switch strategies depending on what they are feeding on.

Answer 28

True, look at how bears can be omnivores.

Question 29

Why is predation suggested as a strong selective force?

Answer 29

Evidence of a variety strategies animals have evolved to avoid being eaten.

Common strategies include chemical defense, camouflage, mimicry, displays of intimidation, and armor and weaponry.

Question 30

What are some examples of chemical defense stategies in nature? (3)

Answer 30

1. Skunks
2. Bombardier beetles and their hydroquinine/hydrogen peroxide mixture that is ejected at a temp of (190 degrees F)
3. Squids and black ink

Question 31

List all Antipredator Adaptations! (6)

Answer 31

1. Chemical
2. Coloration advertisment
3. Camo
4. Intimidation (like a puffer fish)
5. Mimicry (some butterflies will look like Monarch butterflies since they are poisonous)
6. Weaponry

Question 32

What is the warning coloration that advertises an organism’s unpalatable taste?

Answer 32

Aposematic coloration

Question 33

[Fun fact] What makes Monarch butterflies toxic?

Answer 33

Their catepillars feed exclusively on milkweed, which contains toxic chemicals called cardiac glycosides that pass into the caterpillars.

Question 34

What is the blending of an organism with the background of its habitat?

Answer 34

Camouflage

For example, many grasshoppers are green and blend in with the foliage on which they feed. Stick insects mimic branches and twigs with their long, slender bodies. In most cases, these animals stay perfectly still when threatened, because movement alerts a predator.

Question 35

What are some examples of displays of intimidation?

Answer 35

Cats arching their back, frilled lizard collars, and puffer fish PUFFIN UP!

Question 36

What is the resemblance of an organism (the mimic) to another organism (the model)?

Answer 36

Mimicry

Question 37

What are the two major types of mimicry and what do they mean?

Answer 37

Mullerian mimicy - A type of mimicry in which two or more noxious species converge to look the same, thus reinforcing the basic distasteful design.

Batesian mimicry - The mimicry of an unpalatable species (the model) by a palatable one (the mimic).

Question 38

What are examples of armory and weaponry in nature?

Answer 38

Turtle shells, horns and antlers, claws, pincers, and scorpian tails.

Question 39

Fun Fact:

Research studies have shown that predators can have a signifi cant eff ecton prey populations. Considerable data exist on the interaction of the Canada lynx and its prey, snowshoe hares, because of the value of the pelts of both animals.

In 1942, British ecologist Charles Elton analyzed the records of furs traded bytrappers to the Hudson’s Bay Company in Canada over a 100-year period. Analysis of the records showed that a dramatic 9- to 11-year cycle existed for as long as records had been kept.

As hare density increases, there is an increase in density of the lynx, which then depresses hare numbers. This is followed by a decline in the number of lynx, and the cycle begins again. Using radio collars to track individual hares, researchers were able to determine that 90% ofindividuals died of predation.

Ecologists have found that in nearly 1,500 predator-prey studies, over two-thirds (72%) showed a large depression of prey density by predators. Thus, we can conclude that in the majority of cases, predators influence the abundance of their prey in their native environment.

The variety of antipredator mechanisms discussed earlier also shows how predation is important enough to select for the evolution of chemical defenses, camouflage, and mimicry in prey. Taken together, these data indicatethat predation is a powerful force in nature.

Answer 39

N/A

Question 40

What does herbivory involve?

Answer 40

The consumption of plant material or the material of similar life-forms such as algae.

Herbivory can be lethal to plants, especially for small species. However, it is often nonlethal, because many plant species, particularly larger ones, can regrow.

Question 41

What are the two hypotheses that have been proposed to answer the question of why more plant material is not eaten?

Answer 41

First, predators and parasites may keep herbivore numbers low, thereby sparing the plants.

Second, the plant world is not as helpless as it appears. The sea of green is armed with defensive spines, tough cuticles, noxiouschemicals, and more.

Question 42

What is a plant’s first line of defense and what does it entail?

What about a plant’s second line of defense and what does it entail?

Answer 42

It is mechanical such as thorns and spines.

In addition, tough fibers discourage herbivore feeding, and grasses and palms sequester silica, making their foliage difficult to chew.

Furthermore, an array of unusual and powerful chemicals is present inplants, including alkaloids (nicotine in tobacco, morphine in poppies, cocaine in coca, and caffeine in coffee), phenolics (lignin in wood andtannin in leaves), and terpenoids (in peppermint)

Question 43

Powerful chemical compounds are not part of the primary metabolic pathway that plants use to obtain energy and are therefore referred to as?

Answer 43

Secondary metabolites

Molecules that are produced by secondary metabolism.

The staggering variety of secondary metabolites in plants, over 25,000, may be testament to the large number of organisms that feed on plants.

In an interesting twist, many of these compounds have medicinal properties that have proved to bebeneficial to humans.

Question 44

Of the defenses shown here, which type would be most effective in deterring invertebrate herbivores?

Answer 44

Invertebrate herbivores can eat around mechanical defenses; therefore, chemical defenses are probably most effective against these herbivores.

Question 45

What is the ability of plants to prevent herbivory via either chemical or mechanical defenses?

Answer 45

Host plant resistance

One serious problem associated with commercial development of host plant resistance is that it may take a long time to breed into plants—between10 and 15 years.

This time frame results because of the time it takes to identify the responsible chemicals and develop the resistant genetic lines. Also, resistance to one pest may come at the cost of increasing susceptibility to other pests. Finally, some pest strains can overcome the plant’s mechanisms of resistance.

Question 46

Fun Fact: What percentage of cropland in the U.S. utilizes pest-resistant plant varieties, most of these being resistant to plant pathogens?

Answer 46

75%

For example, Bt corn is a variety of corn that has been genetically modified by incorporating a gene from the soil bacterium Bacillus thuringiensis (Bt) that encodes a protein, Bt toxin, that is toxic to some insects.

Genetic engineers have also produced Bt cotton, Bt tomato, and genetically modified varieties of many other crop species.

Question 47

What are the two ways herbivores overcome plant defenses like with detoxifying poisons?

Answer 47

By two main chemical pathways - oxidation and connjugation.

Oxidation, the most important of these mechanisms, occurs in the liver of mammals and in the midgut of insects. It involves catalysis of the secondary metabolite to a corresponding alcohol by a group of enzymes known as mixed-function oxidases (MFOs).

Conjugation, often the nextstep in detoxification, occurs by uniting the harmful compound or its oxidation product with another molecule to create an inactive and readily excreted product.

Question 48

What is a good method for estimating the effects of herbivory on plant populations?

Answer 48

Remove the herbivores and examine subsequent plant growth.

A conclusion from such experiments is that invertebrate herbivores, such as insects, usually have a stronger eff ect on plant populations than vertebrate herbivores such as mammals, at least interrestrial systems.

Thus, although large grazers like bison in North America or antelopes in Africa might seem to be of huge importance in grasslands, it is more likely that grasshoppers are the more significant herbivores because of their sheer weight of numbers.

Question 49

What is an organism that feeds on another organism, called the host, for a relatively long time, but does not normally kill it outright?

ALOT OF PARASITE INFO HERE

Answer 49

Parasite

Some parasites remain attached to their hosts for most of their life. For example, tapeworms spend their entire adult life inside the host’s alimentary canal and even reproduce within their host. Others, such as the Chinese liver fluke, have more complex life cycles that require multiple hosts.

To facilitate transmission, many parasites inducechanges in the behavior of one host, making that host more susceptibleto being eaten by a second host. For example, rodents infected with thebrain parasite, Toxoplasma gondii, are more active and less fearful of cats and their smells, which increases the chances that infected rodents will be eaten by a cat, the parasite’s definitive host.

The malaria parasite, a single-celled species in the genus Plasmodium, has a complex life cycle involving two hosts, mosquitoes and vertebrates.

Plasmodium interferes with the ability of the mosquito to draw blood from its vertebrate hosts. This increases the number of attacks the infected mosquitoes make in order to try and obtain enough blood. Increased attack rates maximize the transmissionrates of the Plasmodium itself.

British epidemiologist Jacob Koella and colleagues showed that most uninfected mosquitoes generally feed on just one human host at night, and only 10% bite more than one person. Multiple biting of different hosts increased to 22% in malaria-infected mosquitoes. In addition, the saliva of the infected mosquitoes was changed, making the host’s blood flow less freely into the mouthparts.

Similar behavior is exhibited by leishmaniasis parasites in sand flies and bubonic plague parasites in fleas.

Question 50

T/F Some plants can be parasitic on other plants.

Answer 50

True

Question 51

What is a parasitic organism that lacks chlorophyll and is totally dependent on a host plant for its water and nutrients?

Answer 51

Holoparasite

One famous holoparasite is Rafflesia arnoldii, which lives most of its life within the body of its host, a
Tetrastigma vine, which grows intropical rain forests.

Only the Rafflesia flower develops externally. It is a massive flower, 1 m in diameter, and the largest knownin the world.

Question 52

What is a parasitic organism that photosynthesizes, but lacks a root system to draw water and thus depends on its host for that function?

Answer 52

Hemiparasite

Mistletoe (Viscum album) is a hemiparasite that grows on the stems of trees. Hemiparasites typically have a broader range of hosts than do holoparasites, which may be confined to a single or a few host species.

Question 53

What is the term used to describe parasites that feed on one or a few closely related species?

What are parasites that feed on many host species?

What is a parasite that multiplies within its host, usually within the cells?

What is a parasite that lives in a host but releases infective juvenile stages outside the host’s body?

Answer 53

Monophagous

Polyphagous

Microparasites

Macroparasites

Question 54

Out of micro and macroparasites, which one has a short lived immunological response and the hosts are subject to reinfection?

Answer 54

Macroparasites

Question 55

What are ectoparasites and endoparasites and what are some examples? Which feeds on a more variety of hosts due to specialization needed?

Answer 55

Ectoparasites - A parasite that lives on the outside of the host’s body.

Endoparasites - A parasite that lives inside the host’s body.

Ectoparasites such as leaches and ticks. Endoparasites are pathogenic bacteria and tapeworms.

Question 56

T/F - With the exception of single-celled microorganisms, a free-living organism does not harbor multiple parasites.

Answer 56

False. They typically DO harbor multiple parasites and it is rare that they do not.