Predation and Herbivory II

Question 1

Animal strategies to avoid being eaten

Answer 1

• behavioural
• signalling to deter predators
• physical features

Question 2

Behavioural strategies

Answer 2

• staying out of sight
• seeking refuge - costs energy and hampers foraging opportunities but fitness benefits outweigh costs
• nocturnality
  communal defense - forming a defensive circle
• mobbing
• alarm vocalizations
• fighting back - attacking/mobbing via chemical and mechanical means

Question 3

Signalling to deter predators

Answer 3

• aposematic coloration (learning to not eat certain organisms with toxins
• Batesian mimicry - a non toxic species resembling a toxic one
• Mullerian mimicry - a toxic species resembling other toxic ones
• bluffing - a pattern displayed by an animal that lacks strong defenses

Question 4

example of bluffing

Answer 4

mayflies posture themselves to make them seem larger

Question 5

Physical Features

Answer 5

• body size
• safety-in-numbers
• rapid movement
• body armour
• autonomy

Question 6

Pros and Cons of body size

Answer 6

pro: not dying, from predators
con: takes a lot of energy to maintain large body size

Question 7

How do species that coexist with predators avoid being eaten if they do actively signal to /deter the predators

Answer 7

refuge
- the existence of refugia has been used as one explanation for why predators do not drive their prey to extinction

Question 8

Gause’s Predation experiment

Answer 8

• three different treatments
• putting predator and prey in a water solution did nnot result in th eoscillations predicted by the Lotka-Volterra predator- pret model
• prey and predator both went extinct
• given refugia for prey, they are able to hide so effectively that predator died

Question 9

Critique of Gause’s Predation experiment

Answer 9

immigration created artificially restocking population

Question 10

What did Gause’s Predation experiment show?

Answer 10

that immigration might be one reason why predator and prey population dynamics show oscillations and why avoid extinction

Question 11

Types of Refuge

Answer 11

• spatial
• metapopulaiton rescue

Question 12

Plant defences

Answer 12

1. make them less likely to be eaten (resistance)
2. reduce the harm while being eaten (tolerance)

Question 13

Structural defensive strategies for plants

Answer 13

• pointy stuff (thorns, spines)
• trichomes (extension of epidermis that inhibit insect movement)
• can also make hard, rigid leaves that are difficult to eat

Question 14

Crypsis

Answer 14

• “hiding”
• ex. Mimosa pudica “wilt” when something comes into contact with them
  ex. stone plant, a type of succulent, avoid being eaten by blending in with their environment

Question 15

Chemical Defensive Strategies - plants

Answer 15

• secondary metabolites: compounds not involved in PSN nor are necessary for respiration, growth or development
• alkaloids: noxious odors, repellent taste, excessive stimulation, lethargy

Question 16

Indirect Plant defensive strategies

Answer 16

sometimes plants call on animals to defend them

Question 17

Constitutive defences (define, pros and cons)

Answer 17

• permanent defenses
• produced continuously, regardless of what happens to the plant
• pro: no need to worry about sudden attacks
• con: cost heaps of energy to maintain

Question 18

Induced Defences (define, pros and cons)

Answer 18

• phenotypic plasticity
• concentrations of a defensive chemical (or morphological defence trait) increase rapidly in response to herbivore damage
• pro: no constant maintenance cost
• con: sudden attacks can be more damaging

Question 19

Example of constitutive defence

Answer 19

toxins
- tobacco contains nicotine, an alkaloid compound that is toxic to some herbivores

Question 20

Example of induced chemical defence

Answer 20

tomato plants increase volatile compound production after infestation by spider mites

Question 21

Why are toxic alkaloids more common in tropical plants?

Answer 21

• tropical areas have more diverse communities of herbivores
• greater variety of herbivores, greater variety of defences needed

Question 22

Why do plants not have warning coloration?

Answer 22

• plants are generally green because of the interaction between light and chlorophyll
• color other than green = less light absorbed= less photosynthesis

Question 23

Why are some fruits toxic?

Answer 23

• they are not ripe yet
• to reduce risk of seeds being digested
• to facilitate seed dispersal by frugivores

Question 24

Why is the planet green?

Answer 24

• because predators limit their plant-eating prey

Question 25

Top-Down control of herbivores by predators

Answer 25

• top-down trophic cascade of effects from carnivore to plant
• carnivores tend to compete with each other for food, and plants also compete strongly
• herbivores tend to compete less - because they are controlled by predators)