Lecture 11

Front 1

Herbivory

Back 1

Consumption of plant materials by animals

Front 2

Herbivory can be..?

(2)

Back 2

At the expense of plants (+/-)= exploitation herbivory

or

beneficial to plants (+/+)= mutualistic herbivory. Ex- The latter involves eating plant material but dispersing the seeds or pollen.

Front 3

Herbivore diet

Back 3

seeds (granivore
fruits (frugivore)
stems, leaves (folivore)
buds (browser)
algae (algivore)

Front 4

Generalizations for herbivores

Back 4

1. Food is generally more available for herbivores than it is for carnivores

2. Specialization for a plant diet primarily involve evading the physical and chemical defenses of the plants. They have been naturally selected to evolve defenses that make eating plants less rewarding

3. The most high energy plant foods (seeds, fruit, flowers) are generally the least abundant, most widely dispersed plant product.

4. Digestive track of herbivores is much longer and more complex than those of carnivores.

Front 5

Which plant products have the least accessible energy?


moderately accessible energy?

Back 5

wood, bark, branches

leaves, grass, algae

Front 6

which herbivores have more complex digestive tracts?

Back 6

digestive systems of leaf and grass eaters are more complex than the systems of fruit, nectar, pollen and seed eaters.

"fattest herbs"- cows, hippos, rhinos, buffalo AKA biggest digestive systems

Front 7

Distinct herbivore tacics

Back 7

1. selection of certain plant parts

2. Make food caches

Front 8

Selection of certain plant parts
(ex roots, leaves, shoots, fruits, seeds)

Back 8

deer, mice prefer the seed heads of grasses. cows, the central blades. meadow mice- thick base of base and roots of grass

carnivores seldom focus on only one part of prey

Front 9

Make food Caches

Back 9

make food caches during times of food abundance

done by numerous species

ex. chipmunk, acorn. woodpeckers, squirrels

Front 10

Plant defenses against herbivores

Why is world so green? PLANT DEFENSES

Why don't all plant species have defenses if defending against herbivores is so important?

Back 10

its energetically costly to synthesize structural and chemical defenses, nd therefore only when herbivory becomes excessive is their strong selection favoring defense mechanisms in a population

Front 11

Mechanical Defenses

Back 11

1. tough epidermis

2. entanglement devices

3. piercing devices

Front 12

tough epidermis

Back 12

seed shells, bark on branches and trunks

Front 13

entanglement devices

Back 13

thick waxy cuticle and plant hair on leaves and stems entangles and deters small herbivores

ex. trichomes- enlarged hairs, sometimes with toxic secretion. common in tomato plants

Front 14

piercing devices

Back 14

-cutting edges in "cutgrass" a wetland species (silica)

-spines and needles in many deciduous plants and cacti

Front 15

why do physical defenses occur in the desert where herbivores are less abundant?

Back 15

plants in the dessert are a source of food AND moisture and organisms looking for both seek plant tissue. The cost of replacing plant tissue is very high

Front 16

Chemical defenses

Back 16

1. standing defenses (always present in plants)

2. indigestible chemicals: chemicals that render the plant tissues less digestible

Front 17

Standing defenses

-Secondary metabolites

Back 17

derivatives of existing plant metabolism that are selected for when they discourage herbivores

Front 18

Secondary metabolites

name three

Back 18

1. phenolics (like tannins in oak leaves, which are substances that inactivate animal's digestive enzymes; marijuana in animals)

2. terpenes (mint and lemon oil; pyrethroids in chrysanthemums: pinene in pitch pines that it toxic to bark beetles)

3. Alkaloids

Front 19

Alkaloids (a secondary metabolite)

Back 19

morphine, codeine, caffeine, nicotine, cocaine. causes destructive behavior in herbivores in large quantities; habit-forming nature of these substances is the best way a plant has of reducing herbivore reproduction

Front 20

Indigestible chemicals:chemicals that render the plant tissues less digestible

(it is a standing defense)

Back 20

cellulose- except for fungi, some bacteria, and protists, no organism is able to break down cellulose

silica- an indigestible component of grasses, also hurtful to eat (cur grass)

lignin- the most indigestible product of plants, even to bacteria and most fungi

Tannins- insoluble colloidal compounds that bind to proteins under acid conditions (in animal stomachs) and block protein digestion and make plant nutrients much less available to the herbivore (oak and hemlock)

Inducible defenses (ques on next slide)

Front 21

Inducible defenses

Back 21

plants increase production of existing chemicals, or synthesize new chemicals, upon attack by herbivores of pathogens. These defenses are genetically plastic traits, and are activated only when the plant is attacked, which eliminates the expense of standing defenses when herbivory is low or absent

Front 22

Give an example of inducible defenses

Back 22

chemical deterrent in cottonwoods: cottonwood/beaver/leaf beetle. cottonwood trees felled by beaver produce new shoots containing a defensive compound (salicortin) that deters beaver attack on cottonwood saplings. Unfortuneately, the leaf beetle larvae feeding on these cottonwood saplings acquire the compound that protects them against their normal ant predators, and so in essence, the beaver is deterred, but the beetle is favored by this plant defense.

Front 23

Herbivores responses to plant defenses

(4)

Back 23

1. countering mechanical defenses

2. countering chemical defense

3. form a mutualism

4. eat sub-toxic amounts

5. eat plant before induced defenses are activated

Front 24

countering mechanical defenses

(herbivores response to plant defenses)

Back 24

tough tongue, mouth and gut
ex. cactus-eating tortoises and wood rats, and giraffe who eats prickly underside and outer crown leaves of acacia trees

mastication apparatus and grinding mills to breakdown tough seed coats and resistant tissue: grinding teeth, continually growing teeth, gizzards in birds, regurgitation of cud and re-mastication in many hoofed mammals and rodents

Front 25

Countering chemical defense

1) they inactivate defense chemicals

(herbivores response to plant defenses)

Back 25

cellulase evolution: many bacteria, (decomposers of plant products) have evolved the enzyme cellulase to breakdown cellulose (a defense product) into highly utilizable simple sugars (glucose)

Alkaline pH: ex. gypsy moth caterpillars have an alkaline (high ph) stomach, which keeps tannins from binding to protein and making protein unavailable to the hebrivore. The herbivore is one up in the Co-evolutionary Arms Race between the herbivore and the plant

Front 26

Another countering chemical defense is

Form a mutualism with another species that can digest the defense

Back 26

1) internal (gut symbiosis) of many animals with bacteria and protists that can break down cellulose

EX ruminant herbivores, hoofed mammals, rodents, a few birds and termites have microbial partners (protists, bacteria) in their stomachs and/or caeca that breakdown cellulose into glucose

(LOOK UP IN NOTES)

Front 27

Form a mutualism

an external (ant-fungal relationship)

another herbivore response to plant defenses

Back 27

ex. leaf cutting ant. Ants harvest leaf fragments and put them into chambers with a specialized fungus that grows on the fragments and produces excretions of excess simple sugars for the ants. only the fungus has cellulase for the digestion of plant cellulose.

Front 28

Eat sub-toxic amounts

Back 28

eat subtoxic amounts of plants (some primate leaf eaters) and then move on to another plant species (easy to do in the tropics with a rich diversity of plant species)

Front 29

eat plant before induced defenses are activated

Back 29

eat plant before induced defenses are activated, and then abandon the plant

ex. heliconius butterfly larvae block chemical defenses of a tomato plant relative

Front 30

Carnivory

Back 30

Killing and consumption of other animals (+/-)

Front 31

Carnivory diet

Back 31

includes specialists such as piscivores (fish eaters) and insectivores

Front 32

There is an absence of what in carnivore diet

Back 32

absence of specialization on parts of animals. instead just different animal groups

there is some preference to the otder of tissues consumes- such as brains, head, gonads and guts

Front 33

Generalizations for carnivores

(3)

Back 33

1. animals represent a higher quality food item (protein, fat) than plants.

2. specializations for carnivory are generally different from those of herbivory

3. animals are seldom known to freely produce parts of themselves as food for some other organism in exchange for some favor to resource

Front 34

animals represent a higher quality food item (protein, fat) than plants.

(A Generalization for carnivores )

Back 34

the mechanical and chemical breakdown of animal tissue demands fewer and more simple digestive specializations, as reflected in the relatively lower biomass of carnivore digestive systems in comparison to herbivore diggestive systems

Front 35

specializations for carnivory are generally different from those of herbivory

(A Generalization for carnivores )

Back 35

specializations for carnivory are generally different from those of herbivory (ex those required for catching, subduing and killing prey, such as claws, talons, refined senses and large brains, specialized teeth, venom glands, extreme morphological specializations for speed and prey capture involving leaping/grasping limbs)

Front 36

animals are seldom known to freely produce parts of themselves as food for some other organism in exchange for some favor to resource

(A Generalization for carnivores )

Back 36

animals are seldom known to freely produce parts of themselves as food for some other organism in exchange for some favor to resource, unlike in plants where mutualistic herbivory (+/+) is common. Some microorganims have a mutualistic relationship with plants and animals where beneficials microbes extract some nutrients from an animals body surface (skin, gut lumen) but protect the organism from more harmful microbial invaders

Front 37

Distinct carnivore tactics

(3)

Back 37

1. search image

2. overcoming prey mobility

3. fat storage

Front 38

search image

A Distinct carnivore tactics

Back 38

visual and chemical focus on the most abundant/rewarding prey type while ignoring nearby, but otherwise good, prey, for at least as long as the focal prey is the most economical to take down

Front 39

overcoming prey mobility


A Distinct carnivore tactics

Back 39

-social carnivory (lions)
- pursuit:short distance (cats) or long distance (wolves) dichotomy of adaptations
-Luring (angler fish lure and snapping turtle tongue)
-sit and wait (praying mantis) and surprise pounce/grasp/bite

Front 40

fat storage


A Distinct carnivore tactics

Back 40

food caches are rare as a means of long-term energy storage, except during winter by some carnivores burying parcels of meat

Front 41

Prey Defenses for Carnivore prey

Back 41

1. Mechanical/behavioral defenses of prey

2. Chemical defenses of prey

Front 42

Mechanical/behavioral defenses of prey

(9)

Back 42

1. retaliation: porcupine quills, sting ray spine, zebra kick

2. startling behavior: under wing moth with hind wing eye spots looking like owl face (also, recall apple maggot fly mimicking a jumping spider)

3. deflection of attack to non-vital area: 4-eyed butterfly fish (eyespots on tail)

4. Large size: elephant, buffalo

5. Death feigning: most carnivores avoid eating aged flesh to avoid toxins/disease of rotted flesh- hog nose snake, opossum

6.Fleeing: quickly as deer, antelope; retreat to burrow in ground hogs

7. Crypis: becoming hard to locate (insect of spider looks like bird dropping on leaf)

8.Clustering, safety in numbers and confusion effect ex grunt fish

9. armor: Mussel shell thickness, n inducible (genetically plastic) defense

Front 43

Armor

mussel/crab system

Back 43

chemicals from crabs cause larger mussel shells, so there is a cause and effect relationship between the presence of crabs and thicker mussel shells and stronger attachment

Front 44

Chemical Defenses of carnivore prey

(2)

Back 44

1. Nausea induction

2.Death threat via toxins sequestered from another organism

Front 45

Nausea induction

A Chemical Defenses of carnivore prey

Back 45

skunk scent, hydrogen cyanide production by lady bugs

Front 46

Death threat via toxins


A Chemical Defenses of carnivore prey

Back 46

Death threat via toxins sequestered from another organism

Front 47

Two examples of a Death threat via toxins sequestered from another organism

Back 47

Ex 1. Newts and blue-spotted octopus have Tetrodotoxin obtained from a bacteria (most potent neurotoxin known)

Ex 2. Monarch butterfly.

Front 48

Monarch Buterfly

An example of a Death threat via toxins sequestered from another organism

Back 48

the monarch butterfly is an example of the exploitation of a plant chemical defense

LOOK AT NOTES

Front 49

Parasites

Back 49

organisms that in the process of feedign on animals or plants generally reduce the quantity of tissue, but not tissue function, in amounts too small to be life-threatening but which can be substantial enough to have a negative effect on the organism.

Front 50

Life cycles of the adult parasite

Back 50

Life cycles of the adult parasite (in/on the definitive host) often involve other organisms (intermediate host)

see blood fluke page 736

Front 51

Two types of parasites

Back 51

1. resident parasites

2. transient parasites

Front 52

Resident parasites

Back 52

live-on parasites, often a community of ecto- and endoparasites living and often reproducing in/on a single organism

ex/ tapeworm, feals, yeats on animals, galls, scale, insects of plants. Buffalo video

Front 53

Transient parasites

Back 53

periodic visitors looking for a meal, such as mosquitoes, leeches, vampire bats, ticks, soapberry bug. Theoretically, most plant herbivores are plant parasites in the sense that they graze on a plant part without altering tissue function or killing the plant

Front 54

Pathogens

Back 54

anything that CAUSES disease (the alteration in the normal function of living cells, tissues, organs, or organ systems).

Pathogens can range from environmental stimulants (cigarette smoke) or organisms (bacteria, viruses).

Pathogens organisms reduce the individuals ability to sustain normal life functions and activity, and if untreated can cause death

Front 55

It is not in the parasite's best interest to..?

Back 55

It is not in the parasite's best interest to kill the individual that they depend on for food and protection for long periods.

Front 56

What are two types of parasites?

Back 56

1. Resident parasites

2. Transient parasites

Front 57

Resident parasites

Back 57

live-in parasites, often a community of ecto- and endoparasites living and often reproducing in/on a single organisms

Front 58

Example of resident parasites

Back 58

tapeworm, fleas, yeast on animals; galls, scale insects of plants.

EX Buffalo video

Front 59

Transient parasites

Back 59

periodic visitors looking for a meal, such as mosquitoes, leeches, vampire bats, ticks, soapberry bug; Theoretically, most plant herbivores are plant parasites in the sense that they graze on a plant part without altering tissue function or killing the entire plant

Front 60

Pathogens

Back 60

anything that causes disease (the alteration in the normal function of cells, tissues, organs, organ systems)

Front 61

Pathogens reduce what?

Back 61

Pathogenic organisms reduce the individual's ability to sustain normal life functions and i, and if untreated can cause death

Front 62

What are the Characteristics in the context of interactions between organisms

(4)

Back 62

1. Pathogens use the host as a disposable energy source for its own reproduction and, in the case of animals, dispersal agent

2. The virulence (ability to cause disease) of pathogenic organisms is influenced by the density of the host and, when present, the vector (=another organism that transmits the disease causing microbe to the host)

3. Pathogens often modify the behavior of the host to make them more vulnerable to contact by the vector

4. Diseases, such as those caused by viruses, are often difficult to control because the high mutation rates of the viruses stay ahead of any immunological responses of its host.

Front 63

The virulence (ability to cause disease) of pathogenic organisms is influenced by the density of the host and, when present, the vector (=another organism that transmits the disease causing microbe to the host)

Describe High and Low Virulence

Back 63

High Virulence- High density of the host/vector allow the rapid spread of the disease before symptoms and even death occur, despite the fact that the host shows almost immediate symptoms and even death (= SYMPTOMATIC host). The pathogen is not designed by natural selection to reduce virulence to give enough time for disease transmission; the high host density of the host insures almost immediate transmission.

Low virulence- Low host/vector density results in pathogens delaying the onset of the disease symptoms (asymptomatic) in order to insure their transmission to other hosts. These disease organisms are often difficult to eradicate because infected individuals spread the disease widely before the symptoms appear

Front 64

Example of High and Los Virulence

Back 64

High- bird flu

Low- Aids

Front 65

Pathogens often modify the behavior of the host to make them more vulnerable to contact by the vector

this is a Characteristics in the context of interactions between organisms

give an example

Back 65

the mosquito in the case of malaria; data show that mosquitoes are highly attracted to individuals inflicted with the disease

Front 66

Two case studies involving pathogenic organisms?

Back 66

1. Myxoma virus: causes the disease Myxomatosis in rabbits

2. Human Malaria

(Look Up in Notes)