Ecology Exam #2

Front 1

How are life histories evolved?

Back 1

life histories are evolved in a way that works for a particular species

this has led to variations on spacing

Front 2

Spacing

Back 2

the distance between neighbors

Front 3

Random Spacing

Back 3

there is no predictable pattern of distribution of individuals, they are as likely to be in any one place as any other

Front 4

Clumped or Aggregated Spacing

Back 4

groups tend to be found together

most common pattern

in a broader sense, clumps may be distributed randomly or in a pattern

Front 5

Clumped or Aggregated Spacing
Examples

Back 5

families (humans or other)
troops of baboons
schools of fish
flock of birds
gaggle of geese
covey of quail
pride of lions
herd of bison
swarm of bees
pack of wolves
colony of ants
pinoak flat
oak grove
pine bluff
cedar glade
corn field

Front 6

Even or Uniform Spacing

Back 6

there is even spacing between individuals

Front 7

Even or Uniform Spacing
Examples

Back 7

-honeycomb example is almost perfectly even (although the bees in the cells cannot choose the spacing pattern)

-breeding sunfishes often have the "honeycomb" spacing

Front 8

Causes of Clumped Spacing Patterns
Habitat Patchiness

Back 8

distribution of moisture, food, cover

Front 9

Causes of Clumped Spacing Patterns
Mode of Reproduction

Back 9

vegetative reproduction by underground stems, dispersal radius of seeds, gathering to find mates (leks, mayfly swarms)

Front 10

Causes of Clumped Spacing Patterns
Mode of Foraging

Back 10

hunt together (lions, wolves)

Front 11

Causes of Clumped Spacing Patterns
Defense

Back 11

flocks of birds see danger, musk oxen form rings, "selfish herd"

Front 12

"Selfish Herd"

Back 12

group to let the other guy get eaten while you hide in the masses

Front 13

Causes of Even Distribution

Back 13

Competitive interaction

-territoriality of birds: "dear enemy"

-some plants produce toxins in the soil to prevent others from growing nearby

Front 14

What are the attributes to spacing often due to?

Back 14

the attributes of spacing are often due to the social system in animals

Front 15

Society

Back 15

a group of individuals of the same species organized in a cooperative manner

-based on communication (visual, auditory, chemical)

Front 16

Disadvantages of Society

Back 16

attract predators
transmit disease
social stress
local food shortage

Front 17

When Advantages Outweigh Disadvantages...

Back 17

sociality is a valid solution

Front 18

Advantages of Society
Protection from Predators

Back 18

more eyes to notice danger, more mouths to provide warning (which allows also better foraging success because less time has to be devoted to watching)

Front 19

Protection from Predators
Confusion

Back 19

hard for a predator to decide which one to chase

ex. covey of quail and a fox (or human)

ex. human with dipnet after fish (pelicans use same approach a successful human would)

Front 20

Protection from Predators
Physical Defense

Back 20

ex. ants, wasps, etc. can attack en masse

ex. mobbing behavior of birds

Front 21

Selfish Herd

Back 21

individuals in the middle are most safe

a selfish herd is not a society

Front 22

Selfish Herd Examples

Back 22

bird nests in the middle of a colony are safer from predators

fishes in school dart inward - safer individuals constantly change as the school rolls inward

Front 23

Bird Nest in the Middle
Why even try to nest on the fringe?

Back 23

at least the organism can be warned when the predator is approaching

Front 24

Advantages of Society
Increase Foraging Efficiency

Back 24

spend more time feeding, less watching so the organism can feed better in groups
ex. birds

predators stand a better chance of flushing prey

Front 25

Social Facilitation

Back 25

learn to act like others in the group

if one individual discovers a more efficient means to do something, others can pick up on it
ex. Japanese Macaques

Human Groups: support groups, Greek organizations, fashions, fads

Front 26

Information Transfer

Back 26

waggle dance of honey bees

bird colonies can tell which members forage better and follow them

Front 27

Hunting Strategy

Back 27

ex. lions, wolves

Front 28

Advantages of Society
Allogrooming

Back 28

hygienic removal of ectoparasites

get those guys in hard-to-reach places

Front 29

What does the choice between being social or territorial depend on?

Back 29

it may depend on distribution of resources

Front 30

Example of Organisms with no choice between social or territorial...

Back 30

Hymenoptera (ants, wasps, bees, sawflies) and Termites have no choice but to be social

Front 31

Birds and Mammals choice between being social or territorial

Back 31

they may be either, depending on the time of year

-if resources are evenly distributed, being territorial may work best

-if resources are patchy you can't defend your share so be social and search for the patches together

Front 32

Birds Changing from being Social to Territorial Example

Back 32

in spring, when resources are good, ducks, small birds (robins, meadowlarks, cardinals, etc.) occupy a territory

when winter conditions occur, they flock to locate food patches

Front 33

Eusociality

Back 33

obligatory social behavior with precise roles for differet members

Front 34

Eusociality Characteristics

Back 34

-cooperative rearing of young

-fairly permanent colony: offspring mostly remain cooperatively associated with parents

-division of labor: sterile and reproductive castes

Front 35

Eusociality General Rules

Back 35

-the queen is an egg factory

-workers build and maintain the colony, care for the queen and offspring

-in some groups the workers serve also in protection, other groups have special soldiers

Front 36

Special Genetic System
Haplodiploidy

Back 36

-female (queen) mates during a nuptial flight, stores sperm

-later, fertilized eggs produce females (workers) and unfertilized eggs produce males

-thus the females are diploid, males are haploid

Front 37

Special Genetic System
Haplodiploidy
Family Relations

Back 37

-the workers are sisters caring for the mother

-sisters are half related to mother, fully to father (he's haploid) so sisters are 3/4 related to each other

-the queen is half related to sons, half to daughters

-sons are fully related to the queen

Front 38

Why sterile castes?

Back 38

to help a relative is not like in diploid organisms: we are half related, they are 3/4

-your own offspring (for sisters) would be half related to you

-your mother's offspring are 3/4 related: to help mother raise offspring is to produce individuals more closely related to you

Front 39

Special Genetic System
Haplodiploidy
Mammal Case

Back 39

Naked Mole Rats - hairless, burrowing rodent from Africa

-only one female breeds, but if she dies another replaces her

-caring for young in cooperative but onlly breeding female nurses

Front 40

If the Naked Mole Rats are diploid, then why eusocial and why only breeding female nurses?

Back 40

-nurses because onset of nursing usually is brought on by hormons during pregnancy in mammals

-latrine site: breeding female leaves a chemical which inhibits other females, until she dies and another becomes the mother

Front 41

Monogamy

Back 41

pair bond between individuals

-may be for one season (birds and mammals where both are required to be able to successfully raise young)

-may be for life (ducks, geese, swans, some hawks, etc.): share learned experiences, don't have to deal with a novice

Front 42

Polygamy

Back 42

a single member of one sex bonds with several members of the other sex

Front 43

Polygyny

Back 43

the most common form of Polygamy

one male with several females

Front 44

Polygyny Example

Back 44

harems like in elk

male often defends and herds the female

females benefit because the strongest male wins the harem, therefore the offspring have a genetically fit father: this means the female's offspring are more likely to survive

Front 45

Polyandry

Back 45

type of polygamy

sex role reversal: one female has severall males

Front 46

Polyandry Example

Back 46

seen in a few birds

male builds a nest to attract female, she picks the best mates, leaves an egg and moves on

she has less invested in the egg than the male does in the nest - he is more likely to stay so she can leave

Front 47

Promiscuity

Back 47

"one night stand" - meet copulate, depart (no continuing bond relationship)

seen most in mammals, works if female can get enough food to feed self and young (male is not required)

male leaves because he can (female carries young internally - no nest to construct or incubation with which he must help)

this system is most open to invasion by parasites and viruses

Front 48

Philosophical Questions for Ecology of Human Mating Systems #1:

Does a social system with welfare or child support make humans more promiscuous (casual sex)?

Back 48

consider: the male can leave because the child would be cared for, the female might think less about the future because the state or legal system would insure that the child is cared for

Front 49

Philosophical Questions for Ecology of Human Mating Systems #2:

Would increased promiscuity lead to unwanted pregnancies (duh!) thus increasing the demand for legalized abortion?

Back 49

consider: the female still is left with the pregnancy as a result of copulations. Without a bond relationship with a male to share in child-rearing efforts and costs, she may want a way out (abortion). Recall that females of some birds will leave their eggs because they can (polyandry). Would human females with the technology to terminate a pregnancy brought about through copulation with a lesser quality male (love 'em and leave 'em type) want to do so?

Front 50

What determines the nature of mating systems?

Back 50

habitats and environment

Front 51

Polygyny Threshold

Back 51

Assume that female fitness (measured as relative number of grandoffspring) is related to habitat quality...

if habitat quality within the breeding are is quite variable, females may choose to become polygynous rather than monogamous

Front 52

What sex usually drives the mating system?

Back 52

females

Front 53

Reasons for a Female Driven Mating System

Back 53

males will have the brightest colors, the biggest antlers, the greatest size, etc., that females like - thus she selects the mate in most cases

males want to mate with anything of the same species if they can - it means potentially more offspring carrying their genes

-females want to be selective - they are limited in the number of offspring they can produce to carry their genes so they want the best genes possible in the father

Front 54

Polygyny Threshold Reasoning

Back 54

a female wants the greatest fitness possible, so if a male can defend a territory enough better than another male's territory (which is unmated) the may give up monogamy for fitness

Front 55

Cuckoldery

Back 55

essentially adultery in human terms

it is when a female mated to one male mates also with another male

Front 56

Female Advantage to Cuckoldery

Back 56

her advantage genetically is that is reduces the chances of mating with an infertile male (a bird will not know the egg is sterile, so continues wastefully the incubation process), and increases the variation in her offspring

Front 57

DNA Techniques reveal Cuckoldery is common

Back 57

DNA techniques which give accurate assessment of paternity have shown that many species exhibit cuckoldery (causes problems with interpretation of previously mentioned mating systems)

Front 58

Cuckoldery Study in Germany

Back 58

study where paternity was determined for fathers of children born as some hospital. It turned out that a large percentage (around 30%) of the proud new fathers actuallly were not the fathers. Cuckoldery apparently is common in humans.

Front 59

Evolution

Back 59

change; descent with modification

thought to occur most commonly through natural selection

Front 60

Successive Generations

Back 60

genes that produce phenotypes that leave the most offspring are more common in successive generations

thus, evolution through natural selection is based on a change in proportions of gene (alleles)

Front 61

Philosophical Twist

Religion vs. Evolution

Back 61

religion says everything produces after its kind, therefor species are stable

evolution says things change into new forms through conventions like natural selection, therefore species are not stable, but change over time

Front 62

Philosophical Twist

Religion vs. Evolution Consideration

Back 62

in a changing environment (they all do, we see human intervention causing such changes today) a species that cannot change will go extinct

-a declining or extinct species does not have a stable population

-a population able to adapt by changing gene frequencies is a stable but changing population

Front 63

Philosophical Twist

Religion vs. Evolution Conclusion

Back 63

therefore, according to this argument, the ability of species to change leads to their stability, and they can do so only by producing after their own kind, i.e., ability to adapt or change is the primary force behind stability, or evolution could be seen as they force designed by a Creator to add stability to the creation

Front 64

Evolution affects...

Back 64

populations, not individuals

Front 65

Hardy-Weinberg Law

Back 65

phenotypes and genotypes tend to come into equilibrium in populations if destabilizing factors are not operative

equation

binomial expansion

p and q are allele frequencies

Front 66

Hardy-Weinberg Equilibrium is based on...

Back 66

assumptions that almost are never met

-its value is in allowing us to sort out the causes of evolutionary change

Front 67

Hardy-Weinberg Assumptions

Back 67

1) random mating - each individual has an equal chance of mating with any other-sexed individual

2) no random genetic drift - larger population so no chance events

3) no gene flow - immigrants bringing in or emigrants taking away rare alleles

4) no mutation - which would add new alleles

5) no natural selection - no alleles favored or selected against

Front 68

What are life history characteristics based on?

Back 68

environmental constraints

Front 69

Evolution of Life History Traits
Stable Habitats

Back 69

the environment is predictable so populations will be near K

ex. climax forests, cave, ocean depths

these environments will tend to select organisms that can develop life history strategies keeping the population in check near K, or K-selecting - low reproductive rate

Front 70

Evolution of Life History Traits
Unstable Habitats

Back 70

K may be moving at different times so it is difficult to track K

these environments tend to select organisms that can respond quickly to change, so biotic potential (r) is more closely approximated (r-selecting), high reproductive rate

Front 71

r-selected traits

Back 71

-early maturity (>r)
-numerous young
-small young (to be numerous)
-iteroparous (animal)
-annual (if plant)
-less parental care (too many young)
-less competitive ability (habitat may be empty)

Front 72

Iteroparous

Back 72

animals

several breeding iterations per season

Front 73

K-selected traits

Back 73

-later maturity (decrease r)
-few young
-larger young ( > survival by investment)
-long life (slow growth and maturity)
-semelparous (animal)
-perennial (stable environment)
-more parental care (teach survival skills)
-more competitive ability (population near K, so may be crowded)

Front 74

Semelparous

Back 74

animal breeding once per season

Front 75

Definition of species into r-selecting or K-selecting catergories is relative

Back 75

coyote (K) : grasshopper mouse (r)

grasshopper mouse (K) : vole (r)

Front 76

Life history traits cannot be...

Back 76

cleany categorized by human models

Front 77

Plasticity

Back 77

flexibility to alter traits

ex. when density is low, eagles, some colonial birds, and beavers have been shown to breed at earlier ages

ex. litter size may be larger in low-density populations of beaver, deer, river otter, etc.

Front 78

Practical Applications of Understanding Life History Strategies

Back 78

an endangered species that is K-selected requires closer monitoring because reproductive potential is low
ex. California Condors, eagles, grizzlies

for hunting interests: it is difficults to sustain populations for hunters if K-selected
-most game species are relatively r-selected

Front 79

Sociobiology

Back 79

study of the biological basis of social behavior

Front 80

Altruism

Back 80

helping others at a cost to one's self

Front 81

Altruism in Genetic Terms

Back 81

behavior that raises the fitness of another individiual while lowering one's own fitness

Front 82

Why is altruism a difficult concept?

Back 82

because you can explain most acts in terms of its opposite - selfishness

Front 83

Selfishness

Back 83

behavior that benefits the individual at a cost to others

Front 84

Altruism vs.Selfishness Example

Back 84

someone is drowning and another person swims out to save them

-even a good swimmer has a small risk of drowning, so the act could be altruistic

-the protector knows the scorn he/she would recieve for not acting and wants to avoid the social cost (actually a selfish act)

-humans are fond of claiming they do such things becuase they care, but what about selfish deceit?

Front 85

Bottom Line to Altruism vs. Selfishness

Back 85

many behaviors can be interpreted either way, depends on definition

Front 86

Situations that do Cost

Back 86

still, there are apparent situations in which there appears to be a cost to the individual for behaviors it performs

thus, explanations are sought because it seems maladaptive to not be selfish

Front 87

Reason for Kin Selection

Back 87

genes are the units of natural selection

from the point of view of the "selfish gene", the gene wants to leave as many copies of itself as possible (it doesn't care about the individual having offspring as long as lots of relatives are produced - it gives the same result)

Front 88

Kin Selection Example

Back 88

in terms of copies of genes, you would risk you life for 2 siblings (each half related to you) or 2 offspring, 4 uncles or aunts (each is 1/4 related to you), or 8 cousins (each is 1/8 related)

Front 89

Basis of Kin Selection

Back 89

help relatives because it is the same as helping yourself (genetically)

Front 90

Kin Selection as an Explanation for Hymenoptera

Back 90

kin selection is the primary explanation for eusociality in evolution of castes of social hymenoptera

recall these give up reproduction to help sisters and other relatives, genetically because sisters are 3/4 related (haplodiploidy)

note: haplodiploidy is not the only possible cause of eusociality - termites and naked mole rates are diploid

Front 91

Kin Selection as an Explanation for "Helpers at the Nest"

Back 91

"helpers at the nest" sometimes seen in birds

helping parents raise another set of offspring is helping genetically related individuals

this system can develop when moving out on your own would be unsuccesssful due to predation or poor success at rearing offspring

Front 92

Reciprocal Altruism

Back 92

may not occur in nature except in humans (and that is debatable)

it is the expectation that help you give will someday be returned to you

it is easily invaded by cheaters who accept help but would not return it

Front 93

For Reciprocal Altruism to Work:

Back 93

1) there must be stable association (helper and helped remain in contact)

2)organisms can recognize individuals

3)organisms can remember well

4)cheaters will be outcast

in humans, education and growing up (maturing) is the process of gaining the game rules

Front 94

Human Sociobiology

Back 94

some anthropologists, sociologists, etc., argue that human culture can't be studied as biology because the genetic influence on social behavior is minimal

Front 95

Human Sociobiology
Point to Ponder

Back 95

the structure of the brain, allowing humans to be what they are, is under genetic control

Front 96

Human Sociobiology
Argument

Back 96

we shouldn't study humans this way because it could lead to racism and sexism

Front 97

Human Sociobiology
Reality

Back 97

as humans, we often use science to support out prejudices rather than to correct them

further, we are a bit proud and don't want to believe some things (even if they are true)

ex. do humans wear breeding colors (makeup, clothes) to advertise desire to copulate?

Front 98

Extinction

Back 98

result when death rate exceeds birth rate for all populations of a species until all individuals are gone

Front 99

Extinction as an Ultimate Fate

Back 99

extinction is the ultimate fate of all species, partlly because evolutionary change may gradually remove one typological species and replace it with a genetically modified one

Front 100

What is extinction generallly caused by?

Back 100

a change in environmental conditions for which the population cannot compensate

specialists are more susceptiable than generalists, who have a wide range of tolerance

Front 101

Human Role in Extinction

Back 101

the human role has been to accelerte extinction due to our effectiveness in causing change

Front 102

Human Notice of Extinction

Back 102

we notice extinction on islands moreso than in local situations where immigrants may repopulate

Front 103

What prompted classification of species?

Back 103

rate of loss

Front 104

Endangered

Back 104

imminent danger of extinction throughout the range

Front 105

Threatened

Back 105

ones approaching endangered status

Front 106

Rare

Back 106

not commonly found so might be threatened - hard to get information so should be monitored

Front 107

Optimal Foraging

Back 107

the notion that animals should try to maximize energy gain with a minimum of energy expenditure

Front 108

Optimum Prey

Back 108

those that fill the stomach with one individual composed of useful food (less nondigestible material), and which are relatively common

it is tough to be optimal, but several species approximate it

Front 109

Smaller Food Packages

Back 109

provide less energy, and the hunt and chase must continue

Front 110

Larger Food Packages

Back 110

less common and may be difficult to catch and kill, more costly

Front 111

Foraging Entails Several Decision Steps:

Back 111

1)deciding where to look
2)searching
3)pursuit
4)capturing and handling

Front 112

Step One: Deciding Where to Look

Back 112

evaluate your potential success when foraging at different places (partly involves distance between patches because travel time is lost for foraging)

Front 113

Step Two: Searching

Back 113

when in a patch, look for food

decide how long to search before leaving for another patch (giving-up time)

Front 114

Step Three: Pursuit

Back 114

when potential food is spotted, must decide whether it is worth pursuit

may be too far away, or aware of you, or too small to be of benefit

actual pursuit is based on a decision of probability of capture

pursuit will cose some time and may make other prey aware of your presence

Front 115

Step Four: Capturing and Handling

Back 115

after capture, which may take additional time following pursuit, time is taken to handle the food (orientation, evisceration, etc.)

Front 116

How is efficiency increased?

Back 116

by forming search images

Front 117

Search Images

Back 117

identify and focus on a common food that is a good energy package

Front 118

Other Considerations in Finding Food:

Back 118

1)food must provide specific nutrient requirements

2)not all common foods are acceptable - poisonous

3)risk of predation - good food source doesn't matter if you die (birds at a feeder are watchful)

Front 119

Devices in Some Animals for Food

Back 119

pockets on gophers, some mice; large ruminant stomach; crops of birds

Front 120

Optimization

Back 120

least fit are lost to natural selection, so pursuit of optimal foraging is an ongoing process

Front 121

Red Queen Hypothesis

Back 121

-must run to stay in place

-predators capture prey least able to escape, so surviving prey pass on genes for greater ability to escape

-less efficient predators die and contribute nothing to the next generation

-thus, prey are one step ahead of predators in becoming more adept

-problem with bringing in exotic species to another land

Front 122

Herbivory

Back 122

eating plants, mostly insects and mammals are herbivores

Front 123

Herbivory
Grazers

Back 123

eat herbaceous plants

Front 124

Herbivory
Browsers

Back 124

eat herbaceous parts of woody plants

Front 125

Herbivory
Smaller Insects

Back 125

may mine leaves, bore into plants, etc.

Front 126

Due to animal use of plant tissues...

Back 126

plants have responded to herbivory in several ways

Front 127

Preventative Plant Adaptations
Thorns and Spines

Back 127

defend against herbivory

Front 128

Preventative Plant Adaptations
Stinging Hairs

Back 128

ex. nettle has HCl on tips of hairs

Front 129

Preventative Plant Adaptations
Chemicals

Back 129

such as tannins that make plant tissues unpalatable or hard to digest

such as toxic alkaloids and other chemicals that deter herbivores

in some plants production of defensive chemicals is induced by browsing

Front 130

Responsive Plant Adaptations
Overcompensation

Back 130

grazers may eat the apical meristem which would have produced a seed head, so the plant compensates by growing 4 lateral meristems and actually increasing fitness

Front 131

Some animals have responded to anti-predators devices so they can still use them to their advantage...

Back 131

1)obtain food source without competitors

2)use the plants poison as protection for the herbivore (ex. Monarch Butterfly on Milkweed)

3)can use the defensive chemical as an indicator of food supply

Front 132

Herbivory affects plant distribution and abundance...

Back 132

overgrazing results in fields of species with herbivore defenses because others are selected against

studies of exclosures (herbivores are excluded)
-deer may browse new growth thus affect regeneration species composition

Front 133

Frugivory

Back 133

fruit eating

usually birds, mammals, insects

Front 134

Mutualistic Relationship between Plant and Animal

Back 134

with frugivory plant and animal are in conflict (seed predators destroy potential reproduction), but sometimes the relationship is mutualistic

-animal gets food, voids seeds elsewhere helping dispersal of plants

-development of color vision by mammals (primates) probably is related to colored fruit

Front 135

Seed Predation

Back 135

removes potential plants from the population

mostly done by insects, birds, and mammals

Front 136

Seed Production Example

Back 136

ex. oaks

may have large or small mast production in different years

may be because of climate (good year), energetic demands (store energy for future burst)

Front 137

Seed Predation Adaptive Angle

Back 137

bumper crop satiates the seed predator before all seed are gone in a good year

must vary production so predator can't K-select to the predictable seed crop

must synchronize with other trees

Front 138

Seed Predation Adaptive Angle 2

Back 138

bumper crop satiates so other seeds are stored (buried) for possible later retrieval - squirrels may plant the forest so this may be similar to production of nectar for pollinators

Front 139

Predation

Back 139

if predators and prey limit one another, population cycles would occur

Front 140

Lotka-Volterra

Back 140

models that simulate population predation cycles

Front 141

Lotka-Volterra Model

Back 141

Write in later

Front 142

Rosenzweig-MacArthur Models

Back 142

refined Lotka-Volterra by including carrying capacity

see figure in notes

Front 143

Rosenzweig-MacArthur Model in Notes

Back 143

results in stable oscillations because the predator isocline is at the peak of the prey isocline

Front 144

Other RM Models Yield Different Results

Back 144

1)when predator is efficient at getting prey, predator isocline is to the left of the peak of the prey isocline, resulting in diverging oscillations and extinction of one or both (spirals outwards)

2)when predator is able only to by efficient at high prey density (nearer K), predator isocline is to the right of the peak of prey isocline, resulting in dampened oscillations leading to stable densities of both populations (spiral inwards)

Front 145

Threshold Densities

Back 145

important - if there is a refuge protecting low densities of prey, they are secure and predation becomes important only after those densities are exceeded - prey populations can grow even if predators are abundant

Front 146

What are population curves based on?

Back 146

population behavior over time

Front 147

Flat Curve

Back 147

some variation but not large amounts (similar to K-selected concepts)

Front 148

Irruptive Curve

Back 148

at irregular intervals, large peaks appear

Front 149

Cyclic Curve

Back 149

peaks and lows occur at regular intervals

Front 150

All models we have covered are overly simplistic, but the insight they provide coupled with the real data have provided a conclusion:

Back 150

for a predator-prey system to exist there must be complexity

-prey need a refuge from predators

-predators must survive thorugh prey scarcity (may be due to prey switching or movement to better patches)

Front 151

Cyclic Populations

Back 151

in biological terms, a cycle has a predictable regularity (although amplitude may vary)

Front 152

Where do cycles tend to occur?

Back 152

in high-latitude ecosystems (esp. tundra and boreal forest)

Examples:
muskrats may be cyclic in the North but not in temperate regions

-lynxes are cyclic in North America but not in Eurasia

-thus, species are not necessarily cyclic but places seem to be

Front 153

Length of Most Cycles

Back 153

most cycles are on 3-4 year or 9-10 year terms

explanations have included predator-prey cycles, fire cycles, parasites, sunspots: most of these have been discarded

-present explanation use an evolutionary response approach similar to seed predation

Front 154

Functional Response to Food Availability

Back 154

predators could respond to increases in prey by targeting the common prey (recall search images) and increasing the percentage of the prey population taken

Front 155

Numerical Response to Food Availability

Back 155

where predators are attacted to a site of high prey density

also occurs if reproduction is stimulated to produce more predators

Front 156

Batesian Mimicry

Back 156

a harmless species resembles one that is not harmless

Front 157

Batesian Mimicry Example
Butterflies

Back 157

Monarch Butterflies feed on milkweed which contains toxins

the toxins are stored in the Monarch's body so it is toxic to predators

predators quickly learn not to eat Monarchs

thus, Viceroy butterflies look like Monarchs but are not toxic, in order to gain benefits

Viceroys are less common to make the system work

Front 158

Batesian Mimicry Example
Snakes

Back 158

scarlet and milk snakes look like coral snakes

Front 159

Mullerian Mimicry

Back 159

several dangerous species resemble one another

when predator learns to fear one, it also fears the look-alikes

Front 160

Organisms also may mimic..

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aspects of the environment

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Cryptic Coloration

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protective coloration to hide the organism

camouflage

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Camouflage Examples

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catepillars look like leaves, bird dropping, twigs

gray treefrogs look like bark, green treefrogs like leaves

copperheads look like the leaf litter

African pebble plants (look like desert rocks)

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Aposematic (=warning) Coloration

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bright colors in striking patterns

ex. black and white of skunks
ex. poison arrow frogs

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Aggressive Resemblance

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predator looks like the prey or like something harmless in the environment

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Aggressive Resemblance Examples

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fireflies - one species flashes appropriate response for another species, lures the male in by those means, then eats him

cleaning wrasses - another species looks the same but rips out flesh rather than parasites

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Defensive Resemblance

Back 166

look like environment or other features for defense

ex. shape of walking stick; dragonfly naiads look like leaves; eyespots in moths; catepillars swell and look like snake heads

eyes are important in nature

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parasitism

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one organism gets a nutritional benefit at the expense of another organism, without killing it

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Parasitic Organisms

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viruses, bacteria, fungi, protozoans, flatworms, roundworms, spiny-headed worms, some crustaceans, some insects, mistletoes, dodders (yellowish stringlike bodies that twine around other plants)

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Parasite Example
Lampreys

Back 169

some species rasp holes into other fishes and suck out fluids

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Parasite Example
Anglerfish

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an oceanfish that has the male parasitic on the female

-small male attaches to female and they develop a placenta-like fusion of his mouth and her skin

-female still acts as an individual but male becomes little more than a gonad

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Ectoparasites

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a less intimate relationship to the host

found on the body, tap into fluids occasionally

ex. ticks and mites may spend much of their lives off of the hosts

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Endoparasites

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most intimate relationship, live in the body

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Parasitoids

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flies or wasps that live inside the egg, larva, or pupa of another insect

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Complex Parasitism

Back 174

some relationships are so complex that parasites have parasites

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Analogous to blood-sucking parasites are...

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the sap-sucking ones (aphids)

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Parasite Environment

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many parasites, especially endoparasites, live in a generally K-selecting (stable) environment

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Parasite Environment Example

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tapeworms live in the intestine surrounded by food, at almost constant pH, moisture, and temperature

-they are highly adapted for holding position (suckers and hooks)

-due to constant environment, they (like most parasites) are degenerate

-they primarily are sets of gonads, able to produce millions of eggs (r-selected strategy)

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Why do most parasites produce so many eggs?

Back 178

good chances of parasite survival but low chances of egg survival

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Degenerate Parasites

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have no mouth, eyes, digestive system, etc.

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Parasite Competition

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Some parasites may deal with competition

-think of the host organism as a habitat patch or patches

-if there are preferred patches to be had and 2 types of parasites both want access to the patch, competition and displacement may occur

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Parasite Competition Example

Back 181

tapeworms and spiny-headed worms prefer they upper intestine

when occuring together, the spiny-headed worm stays and the tapeworm is displaced posteriorly

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AIDS Transmission

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known to be transmitted most through sexual contact

Front 183

Most Epidemic Spreading of Viruses

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are density-dependent based on the number of individuals in the population

-in AIDS it is also density-dependent, related to the population (# of) sexual contacts (= promiscuity)

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AIDS and Monogamy

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in monogamous or celibate situations, density essentially is 0 so there is no epidemic

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AIDS and Promiscuous Situations

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in promiscuous situations density is high

-because of the male sex drive, males tend to have more sex partners than females, and gay males have the most (according to a TV documentary)

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AIDS Bottom Line

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AIDS is the results of a virus that has taken an adaptive opportunity to invade a niche created by sexual behavior

AIDS existed because we can't date and keep our clothes on, or get married and remain faithful to the marriage

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AIDS Philosophical Problem

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most religions urge monogamy but this has not led to real monogamy in most human populations

could natural selection now create monogamous relationships as the standard for human behavior, considering a much higher mortality rate for non-monogamous individuals?

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Effects of Parasites on Host Numbers

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parasites may keep some populations below K, preventing competitive exclusion, and thus increase species diversity

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Parasite Effect on Host

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some parasites are almost benign in affecting their host, others may kill it

this depends upon evolution of the particular parasite-host system

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Parasite Effect on Host Example

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-in Arkansas, we killed almost all of our deer long ago

-later, we brought some in to restock (from Michigan, which had brainworm)

-brainworm has little effect on deer, but does affect moose (Michigan example) and elk (Arkansas example)

-the Game & Fish Commission tried to restock elk, which usually fails due to brainworm

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Parasite Effect on Host Consideration

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parasite is beneifited if the host is relatively unaffected - live in harmony with your environment because if the environment dies, so do you

-if the host is killed by the parasite, the relationship is probably new

-evolutionary outcome is greater resistance by the host and less virulence by the parasite

-question: human parallel as parasites on the land?

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Some Parasites Alter Behavior of the Host

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life cycles may include intermediate hots that must become prey for they determinate host

thus, some parasites may alter behavior of the present host to increase vulnerability

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Parasites Altering Host Behavior Examples

Back 193

ex. larvae of some flukes live in eyes of fish, partially blinding then so more vulnerable

ex. another fluke moves to the tentacles of the snail host; being brightly colored and pulsating, bird predators see them more easily

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Mutualism and Parasitism

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in some cases what begins as parasitism may end up as mutualism

ex. deer, cows, etc. have a large cecum with a microfauna that can digest cellulose

-this may have originated as parasitic micro-organisms

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Commensalism

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one species lives in association with another but at no cost to the other

gain to the commensal may be food, transportation, support, shelter

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Commensalism Examples

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Remora - has suction cup to attach to shark , eats shark leftovers

Arkansas Example: use of beaver ponds by river otters

Epiphytes: "upon plants" - one uses another for support, perhaps Spanish Moss

Human Commensals - house mouse, norway rat, house finch ("sparrow")

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Saprobism

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feeding on dead or dying tissue

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Carrion

Back 198

dead animal material

insects, birds (vultures), some mammals, bacteria, fungi feed on carrion

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Vertebrate Example of Saprobism with Carrion
Condors and Vultures

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Condors and Vultures are most purely scavengers of carrion

-thes birds have bare heads allwoing them to stick their heads into carcasses without getting feathers messy

-the legs don't have feathers and waste product run down the legs (which usually disinfects)

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Vertebrate Example of Saprobism with Carrion
Bald Eagle

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the Bald Eagle generally scavenges dead fish (Franklin didn't like it as the U.S. symbol because it "didn't get its food honestly")

Front 201

Vertebrate Example of Saprobism with Carrion
Hyaenas

Back 201

hyaenas have powerful jaws to crush bone to get at the marrow

Front 202

Insect Examples of Saprobism with Carrion

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-most beetle or flies, larvae or adults feed

-burying beetles bury a carcass to remove competition, even shaving the carcass to remove blowfly eggs

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Plant Examples of Saprobism with Carrion

Back 203

some plants have adapted to use these insects as pollinators by having odors similar to carriosn (ex. skunk cabbage, pitcher plant, stinkhorn mushroom)

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Dung

Back 204

fecal waste products, esp. of large herbivores are used mostly by insects (beetles and flies)

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Saprobism with Dung

Back 205

ex. dung beetle (tumblebugs) or scarabs as in Egypt
- shape dung into balls, roll them away and bury them with eggs

- very important system due to amount of fecal material produced by large herbivores - it is a frequent and stable niche which can be occupied

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Saprobism with Dead Trees

Back 206

various insects (beetles, wasps) burrow into trees and begin decomposition

-fungi are common as decomposers

-bessbugs slowly move through the wood, also isopods, centipedes, roaches

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Saprobism with Litter

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decaying leaf layer would get very deep if not decomposed

-if accumulation is greater than decomposition rate, fires might get hot

-allochthonous material in aquatic systems: many detritivores (aquatic insects) depend on materials from terrestrial habitats
--these form the base of many aquatic food chains