Part 3

Question 1

What are the 3 kinds of plant defenses?

Answer 1

1. Structural
2. Chemical
3. Associational

Question 2

True or False: According to plant defense hypothesis, if a plant defense is costly then the expression of the defense will be based on the level of grazing inflicted on the plant.

Answer 2

True

Question 3

According to plant defense hypothesis, where are plants more likely to allocate costly defenses?

Answer 3

To the most valuable tissues.

Question 4

What were the effects of cattle grazing on two populations of Opuntia cactus?

Answer 4

The population exposed to the grazing cattle produced more members with spines as compared to those that were not exposed to grazing.

Question 5

What were the effects of exposure to grazing on the Mediterranean shrub Hormathophylla spinosa’s production of spines and fruit? What can be concluded from these results?

Answer 5

The individuals that were exposed to grazers had increased spines and fewer fruits compared to non-grazed individuals. These results show that it is energetically costly for plants to produce defenses, this takes away from the plant’s ability to produce offspring.

Question 6

What are some examples of plant chemical defenses?

Answer 6

Phenylpropanes (cinnamon)

Terpenoids (peppermint, catnip)

Alkaloids (nicotine, morphine, caffeine)

Polyphenols (tannins)

Question 7

In the case of the brown seaweed, what was the effect of clipping the leaves on defensive chemical production as opposed to exposure to grazing from snails (littorina obtusata)?

Answer 7

Clipping the leaves did little to induce production of defensive chemical, however grazing significantly increased the levels of chemical produced.

Question 8

Were littorina obtusata more likely to consume previously grazed brown seaweed or fresh leaves? Why or why not?

Answer 8

No, they were more likely to choose fresh leaves because of the chemical toxins produced by leaf grazing.

Question 9

How was the production of phlorotannins in brown seaweed affected when grazing occurred in the basal stems compared to apical stems?

Answer 9

Phlorotannin production was less active as a result of grazing in the apical shoots compared to the still developing basal shoots.

Question 10

Acacias and ants represent an associational defense because?

Answer 10

The ants provide protection for the plant from herbivores and competitors, and the acacias provide homes for the ants and food through beltian bodies and extrafloral nectaries.

Question 11

What was demonstrated in the study which lined the nests of galapagos finches to protect from bot-fly parasites?

Answer 11

The lined nests produced more fledgling birds, and the sizes of birds as they grew were larger than those that came from unlined nests. This demonstrates that parasites do contribute to population decline in finches.

Question 12

How is food profitability calculated?

Answer 12

By dividing the energy of the item e_i by the total handling time of the item h_i.

Question 13

What are the three main predictions of optimal foraging theory?

Answer 13

1. Predators with small handling times and long search times should be generalists.
2. Diets should be broad in prey-poor environments.
3. The use of low ranking prey types is unaffected by the abundance of the low-ranking prey.

Question 14

True or false? The optimal foraging theory assumes that predators are able to asses the value and abundance of all prey types instantaneously.

Answer 14

True

Question 15

What are the three theories for how animals choose their habitats?

Answer 15

1. Ideal free distribution
2. Ideal despotic distribution
3. Risk-sensitive foraging

Question 16

What is the major assumption of the ideal free distribution theory?

Answer 16

All animals within ecosystems are free to move between habitats unrestricted.

Question 17

What are the major predictions of the ideal distribution theory?

Answer 17

Less suitable habitats will be occupied when the density of the more suitable habitats are high, higher quality habitats will be more densely populated than lower quality ones, and individual success in each habitat will be similar for these cases.

Question 18

In the case of the yellow legged gull two populations’ breeding success rates were studied, one in a preferred habitat (shrub) and one in a less preferred habitat (grass). Were the breeding successes of both the shrub and the grass populations different or the same? Does this support or go against ideal distribution theory?

Answer 18

Breeding in both populations were roughly equal. This supports the ideal distribution theory.

Question 19

What is the assumption of the ideal despotic distribution theory?

Answer 19

Animals are not free to move between ecosystems (hence the despotic).

Question 20

What are the major predictions of the ideal despotic distribution theory?

Answer 20

Population densities will be roughly the same or even greater in poorer conditions with habitat-dependent individual success.

Question 21

What is the assumption of risk-sensitive foraging theory?

Answer 21

Most predators are also prey so animals choose habitats which help to minimize mortality rate/food intake ratios.

Question 22

What are rhizobia and where are they located?

Answer 22

Rhizobia are nitrogen fixing bacteria which live in the root nodules of legumes.

Question 23

What does it mean that nitrogen is “fixed”?

Answer 23

Nitrogen is fixed when it is converted from N_2 to NH_3 by biological means.