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207 Cards in this Set
- Front
- Back
How are life histories evolved?
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life histories are evolved in a way that works for a particular species
this has led to variations on spacing |
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Spacing
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the distance between neighbors
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Random Spacing
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there is no predictable pattern of distribution of individuals, they are as likely to be in any one place as any other
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Clumped or Aggregated Spacing
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groups tend to be found together
most common pattern in a broader sense, clumps may be distributed randomly or in a pattern |
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Clumped or Aggregated Spacing
Examples |
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 |
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Even or Uniform Spacing
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there is even spacing between individuals
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Even or Uniform Spacing
Examples |
-honeycomb example is almost perfectly even (although the bees in the cells cannot choose the spacing pattern)
-breeding sunfishes often have the "honeycomb" spacing |
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Causes of Clumped Spacing Patterns
Habitat Patchiness |
distribution of moisture, food, cover
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Causes of Clumped Spacing Patterns
Mode of Reproduction |
vegetative reproduction by underground stems, dispersal radius of seeds, gathering to find mates (leks, mayfly swarms)
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Causes of Clumped Spacing Patterns
Mode of Foraging |
hunt together (lions, wolves)
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Causes of Clumped Spacing Patterns
Defense |
flocks of birds see danger, musk oxen form rings, "selfish herd"
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"Selfish Herd"
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group to let the other guy get eaten while you hide in the masses
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Causes of Even Distribution
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Competitive interaction
-territoriality of birds: "dear enemy" -some plants produce toxins in the soil to prevent others from growing nearby |
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What are the attributes to spacing often due to?
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the attributes of spacing are often due to the social system in animals
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Society
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a group of individuals of the same species organized in a cooperative manner
-based on communication (visual, auditory, chemical) |
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Disadvantages of Society
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attract predators
transmit disease social stress local food shortage |
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When Advantages Outweigh Disadvantages...
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sociality is a valid solution
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Advantages of Society
Protection from Predators |
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)
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Protection from Predators
Confusion |
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) |
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Protection from Predators
Physical Defense |
ex. ants, wasps, etc. can attack en masse
ex. mobbing behavior of birds |
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Selfish Herd
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individuals in the middle are most safe
a selfish herd is not a society |
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Selfish Herd Examples
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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 |
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Bird Nest in the Middle
Why even try to nest on the fringe? |
at least the organism can be warned when the predator is approaching
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Advantages of Society
Increase Foraging Efficiency |
spend more time feeding, less watching so the organism can feed better in groups
ex. birds predators stand a better chance of flushing prey |
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Social Facilitation
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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 |
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Information Transfer
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waggle dance of honey bees
bird colonies can tell which members forage better and follow them |
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Hunting Strategy
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ex. lions, wolves
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Advantages of Society
Allogrooming |
hygienic removal of ectoparasites
get those guys in hard-to-reach places |
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What does the choice between being social or territorial depend on?
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it may depend on distribution of resources
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Example of Organisms with no choice between social or territorial...
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Hymenoptera (ants, wasps, bees, sawflies) and Termites have no choice but to be social
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Birds and Mammals choice between being social or territorial
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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 |
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Birds Changing from being Social to Territorial Example
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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 |
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Eusociality
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obligatory social behavior with precise roles for differet members
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Eusociality Characteristics
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-cooperative rearing of young
-fairly permanent colony: offspring mostly remain cooperatively associated with parents -division of labor: sterile and reproductive castes |
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Eusociality General Rules
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-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 |
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Special Genetic System
Haplodiploidy |
-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 |
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Special Genetic System
Haplodiploidy Family Relations |
-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 |
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Why sterile castes?
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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 |
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Special Genetic System
Haplodiploidy Mammal Case |
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 |
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If the Naked Mole Rats are diploid, then why eusocial and why only breeding female nurses?
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-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 |
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Monogamy
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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 |
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Polygamy
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a single member of one sex bonds with several members of the other sex
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Polygyny
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the most common form of Polygamy
one male with several females |
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Polygyny Example
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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 |
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Polyandry
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type of polygamy
sex role reversal: one female has severall males |
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Polyandry Example
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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 |
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Promiscuity
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"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 |
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Philosophical Questions for Ecology of Human Mating Systems #1:
Does a social system with welfare or child support make humans more promiscuous (casual sex)? |
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
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Philosophical Questions for Ecology of Human Mating Systems #2:
Would increased promiscuity lead to unwanted pregnancies (duh!) thus increasing the demand for legalized abortion? |
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?
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What determines the nature of mating systems?
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habitats and environment
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Polygyny Threshold
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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 |
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What sex usually drives the mating system?
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females
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Reasons for a Female Driven Mating System
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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 |
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Polygyny Threshold Reasoning
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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
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Cuckoldery
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essentially adultery in human terms
it is when a female mated to one male mates also with another male |
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Female Advantage to Cuckoldery
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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
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DNA Techniques reveal Cuckoldery is common
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DNA techniques which give accurate assessment of paternity have shown that many species exhibit cuckoldery (causes problems with interpretation of previously mentioned mating systems)
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Cuckoldery Study in Germany
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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.
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Evolution
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change; descent with modification
thought to occur most commonly through natural selection |
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Successive Generations
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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) |
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Philosophical Twist
Religion vs. Evolution |
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 |
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Philosophical Twist
Religion vs. Evolution Consideration |
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 |
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Philosophical Twist
Religion vs. Evolution Conclusion |
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
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Evolution affects...
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populations, not individuals
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Hardy-Weinberg Law
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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 |
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Hardy-Weinberg Equilibrium is based on...
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assumptions that almost are never met
-its value is in allowing us to sort out the causes of evolutionary change |
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Hardy-Weinberg Assumptions
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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 |
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What are life history characteristics based on?
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environmental constraints
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Evolution of Life History Traits
Stable Habitats |
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 |
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Evolution of Life History Traits
Unstable Habitats |
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 |
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r-selected traits
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-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) |
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Iteroparous
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animals
several breeding iterations per season |
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K-selected traits
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-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) |
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Semelparous
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animal breeding once per season
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Definition of species into r-selecting or K-selecting catergories is relative
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coyote (K) : grasshopper mouse (r)
grasshopper mouse (K) : vole (r) |
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Life history traits cannot be...
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cleany categorized by human models
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Plasticity
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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. |
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Practical Applications of Understanding Life History Strategies
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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 |
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Sociobiology
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study of the biological basis of social behavior
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Altruism
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helping others at a cost to one's self
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Altruism in Genetic Terms
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behavior that raises the fitness of another individiual while lowering one's own fitness
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Why is altruism a difficult concept?
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because you can explain most acts in terms of its opposite - selfishness
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Selfishness
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behavior that benefits the individual at a cost to others
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Altruism vs.Selfishness Example
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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? |
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Bottom Line to Altruism vs. Selfishness
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many behaviors can be interpreted either way, depends on definition
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Situations that do Cost
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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 |
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Reason for Kin Selection
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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) |
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Kin Selection Example
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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)
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Basis of Kin Selection
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help relatives because it is the same as helping yourself (genetically)
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Kin Selection as an Explanation for Hymenoptera
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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 |
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Kin Selection as an Explanation for "Helpers at the Nest"
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"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 |
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Reciprocal Altruism
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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 |
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For Reciprocal Altruism to Work:
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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 |
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Human Sociobiology
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some anthropologists, sociologists, etc., argue that human culture can't be studied as biology because the genetic influence on social behavior is minimal
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Human Sociobiology
Point to Ponder |
the structure of the brain, allowing humans to be what they are, is under genetic control
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Human Sociobiology
Argument |
we shouldn't study humans this way because it could lead to racism and sexism
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Human Sociobiology
Reality |
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? |
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Extinction
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result when death rate exceeds birth rate for all populations of a species until all individuals are gone
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Extinction as an Ultimate Fate
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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
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What is extinction generallly caused by?
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a change in environmental conditions for which the population cannot compensate
specialists are more susceptiable than generalists, who have a wide range of tolerance |
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Human Role in Extinction
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the human role has been to accelerte extinction due to our effectiveness in causing change
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Human Notice of Extinction
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we notice extinction on islands moreso than in local situations where immigrants may repopulate
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What prompted classification of species?
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rate of loss
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Endangered
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imminent danger of extinction throughout the range
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Threatened
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ones approaching endangered status
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Rare
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not commonly found so might be threatened - hard to get information so should be monitored
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Optimal Foraging
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the notion that animals should try to maximize energy gain with a minimum of energy expenditure
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Optimum Prey
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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 |
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Smaller Food Packages
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provide less energy, and the hunt and chase must continue
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Larger Food Packages
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less common and may be difficult to catch and kill, more costly
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Foraging Entails Several Decision Steps:
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1)deciding where to look
2)searching 3)pursuit 4)capturing and handling |
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Step One: Deciding Where to Look
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evaluate your potential success when foraging at different places (partly involves distance between patches because travel time is lost for foraging)
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Step Two: Searching
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when in a patch, look for food
decide how long to search before leaving for another patch (giving-up time) |
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Step Three: Pursuit
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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 |
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Step Four: Capturing and Handling
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after capture, which may take additional time following pursuit, time is taken to handle the food (orientation, evisceration, etc.)
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How is efficiency increased?
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by forming search images
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Search Images
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identify and focus on a common food that is a good energy package
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Other Considerations in Finding Food:
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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) |
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Devices in Some Animals for Food
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pockets on gophers, some mice; large ruminant stomach; crops of birds
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Optimization
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least fit are lost to natural selection, so pursuit of optimal foraging is an ongoing process
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Red Queen Hypothesis
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-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 |
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Herbivory
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eating plants, mostly insects and mammals are herbivores
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Herbivory
Grazers |
eat herbaceous plants
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Herbivory
Browsers |
eat herbaceous parts of woody plants
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Herbivory
Smaller Insects |
may mine leaves, bore into plants, etc.
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Due to animal use of plant tissues...
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plants have responded to herbivory in several ways
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Preventative Plant Adaptations
Thorns and Spines |
defend against herbivory
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Preventative Plant Adaptations
Stinging Hairs |
ex. nettle has HCl on tips of hairs
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Preventative Plant Adaptations
Chemicals |
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 |
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Responsive Plant Adaptations
Overcompensation |
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
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Some animals have responded to anti-predators devices so they can still use them to their advantage...
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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 |
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Herbivory affects plant distribution and abundance...
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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 |
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Frugivory
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fruit eating
usually birds, mammals, insects |
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Mutualistic Relationship between Plant and Animal
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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 |
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Seed Predation
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removes potential plants from the population
mostly done by insects, birds, and mammals |
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Seed Production Example
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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) |
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Seed Predation Adaptive Angle
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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 |
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Seed Predation Adaptive Angle 2
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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
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Predation
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if predators and prey limit one another, population cycles would occur
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Lotka-Volterra
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models that simulate population predation cycles
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Lotka-Volterra Model
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Write in later
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Rosenzweig-MacArthur Models
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refined Lotka-Volterra by including carrying capacity
see figure in notes |
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Rosenzweig-MacArthur Model in Notes
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results in stable oscillations because the predator isocline is at the peak of the prey isocline
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Other RM Models Yield Different Results
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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) |
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Threshold Densities
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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
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What are population curves based on?
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population behavior over time
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Flat Curve
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some variation but not large amounts (similar to K-selected concepts)
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Irruptive Curve
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at irregular intervals, large peaks appear
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Cyclic Curve
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peaks and lows occur at regular intervals
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All models we have covered are overly simplistic, but the insight they provide coupled with the real data have provided a conclusion:
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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) |
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Cyclic Populations
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in biological terms, a cycle has a predictable regularity (although amplitude may vary)
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Where do cycles tend to occur?
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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 |
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Length of Most Cycles
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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 |
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Functional Response to Food Availability
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predators could respond to increases in prey by targeting the common prey (recall search images) and increasing the percentage of the prey population taken
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Numerical Response to Food Availability
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where predators are attacted to a site of high prey density
also occurs if reproduction is stimulated to produce more predators |
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Batesian Mimicry
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a harmless species resembles one that is not harmless
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Batesian Mimicry Example
Butterflies |
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 |
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Batesian Mimicry Example
Snakes |
scarlet and milk snakes look like coral snakes
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Mullerian Mimicry
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several dangerous species resemble one another
when predator learns to fear one, it also fears the look-alikes |
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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
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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 |
some species rasp holes into other fishes and suck out fluids
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Parasite Example
Anglerfish |
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
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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?
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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
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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
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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
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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
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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 |
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 |
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")
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Vertebrate Example of Saprobism with Carrion
Hyaenas |
hyaenas have powerful jaws to crush bone to get at the marrow
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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
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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
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fecal waste products, esp. of large herbivores are used mostly by insects (beetles and flies)
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Saprobism with Dung
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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
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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 |