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aspect of sexuality that addresses WHY, or for what function, a trait evolved
Ultimate
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Aspect of sexuality that addresses underlying mechanisms that control for a trait
Proximate
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a form of natural selection that acts differently on the sexes
sexual selection
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sexual selection that favors the ability of one sex
i.e. male-male competition
intrasexual selection
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sexual selection that favors traits in one sex which attract the other
i.e. female mate choice
intersexual selection
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occurs when genetic/reproductive interests of females and males diverge
can lead to one sex having an advantage, or an arms race between the sexes
i.e. infanticide
intersexual or mate conflict
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a trait that is specially suited for a particular fx in a particular env't
adaptation
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conditions for evolution by natural selection
- trait is heritable
- trait has variation
- trait leads to differential reproductive success
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differential reproductive success of individuals over multiple generations based on the heritable differences between them; aka non-random selection
natural selection
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examples of sexually selected traits (5)
- Peacock's tail
- Mandrill's face
- Proboscis monkey's nose
- Orang's cheek flanges
- Fiddler crab's claw
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Features that result from a common ancestry
homology
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Specialized traits that distinguish species from its last common ancestor
derived traits
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Common features that are not the result from a common ancestry
Homoplasy
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when distantly related species evolve the same/similar trait as an adaptation to same ecological pressures
convergent evolution
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characteristics of mammals (6)
- 1. Hair
- 2. Specialized sweat glands
- 3. Live young (vivaparity)
- 4. Three middle ear bones
- 5. Heterodonty
- 6. Pentadactyly (ancestral)
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major categories of primates
- 1. Prosimians (suborder: Prosimii)
- 2. Anthropoids (suborder: Anthropoidea)
- A. New World monkeys
- B. Old World monkeys
- C. Apes & Humans
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traits that have not changed from their ancestral states
primitive (ancestral) traits
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Found in southeast Asia
Share some features with both prosimians and anthropoids.
Sometimesclassified in suborder Prosimii, sometimes in suborder Haplorhini
Nocturnal, Solitary
The only carnivorous (insectivorous) primate!
tarsiers
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prosimian beh'ral characteristics (8)
- arboreal
- nocturnal
- solitary
- seasonal breeders
- small-bodied
- tooth comb
- long snouts
- tapetum lucidum
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adaptations that differ from the ancestral state
derived features
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anthropoid characteristics (5)
- large brains
- nails on all digits
- large body size
- diurnal
- complex social systems w/extended parental care
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platyrrhines
new world monkeys
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catarrhines
old world monkeys and apes
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arboreal, frugivorous/gumivorous/folivorous/insectivorous/seed-eaters, 3 Families: Callitrichidae, Cebidae, Atelidae
New World Monkeys
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subfamilies Colobinae/Cercopithecinae, some species terrestrial, some have menstrual cycles and sexual swellings
Old World Monkeys
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Hylobatidae/Pongidae/Hominidae, no tail, large body size, short trunk, flexible shoulder joint
apes
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arboreal brachiators, fruit-eaters, "lesser apes," sexually monomorphic, socially monogamous, & territorial
gibbons
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anthropoids, arboreal scramblers, found in Asia, fruit-eaters, sexually dimorphic, often solitary
orangutans
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terrestrial knuckle-walkers, largely frugivorous, fission-fusion communities
chimps/bonobos
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small, one-male groups, herbivorous and frugivorous, mountain and lowland species
gorillas
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portion of land that is actively defended
territory
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entirety of land used by a troop
home range
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direct costs of group living (5)
- competition for mates/food
- harassment
- disease transmission
- conspicuity
- conflicts
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indirect side effecs of group living (3)
- coordinate decisions/travel
- cover larger distances for food
- increased competition
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solitary social system, occurs when females assemble based on spread out resources
dispersed
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social systems that consist of multiple members, i.e. pair + offspring, harem/bachelor groups, MM-MF, and fission-fusion
cohesive social systems
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polygynandrous species
chimps, red colobus, some capuchins, some macaques
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temporary association; coalescing and splitting based on availability of food
fission-fusion
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ratio of males to females
socioeconomic sex ratio (SSR)
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ratio of males to presently breeding females
operational sex ratio (OSR)
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extreme is forced copulation; more commonly shows up in primates via intimidation and aggression
sexual coercion
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what are the 3 levels sexual selection acts on?
precopulatory, postcopulatory, and postzygotic
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mating contests and mate choice are examples of what level of sexual selection?
precopulatory
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copulatory plugs, sperm competition, and mate guarding (sometimes) are examples of what level of sexual selection?
postcopulatory
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infanticide is an example of what level of sexual selection?
postzygotic
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female counter-strategies to infanticide? 5
- paternity confusion (hidden ovulation, pseudoestrus)
- female defense aid
- male defenders
- female transfer
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most muscular tube in the male body
vas deferens
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what is the most likely reason for such complexity in primate penile morphology?
selection by cryptic female choice
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tip of the penis
distal/glans
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species with the most derived penile morphology; distal penis is filiform w/no glans, likely evolved from sperm competition and to accomodate female swellings
chimps and bonobos
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mechanism for detecting pheromones
vomeronasal organ
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humans and our extinct ancestors after the split from the last common ancestor with chimpanzees
hominids
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any member of the family Hominidae, including all australopithecines and the genus Homo, walks upright
hominid
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any member of the superfamily Hominoidea, including humans, all living apes, and numerous extinct ape and humanlike species from the Mioccene, Pilocene, and Pleistocene epochs
hominoid
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• Date from 4.2 million years to 1.2 million years ago
• Mix of bipedal locomotion and ape-like features
• Small brained creatures with lots of sexual dimorphism in body mass and a little in canine size
• Some species had specialized dietary adaptations (Paranthropines)
General facts about australopithecenes
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Remains found at Lake Turkana, primitive biped (suggested by knee and ankle bones) living in streamside forests
Had large molars, thick enamel, and reduced canines; its U-shaped dental arcade is more similar to chimps and gorillas
Dated to 4.2-3.9 mya
Australopithecus anamensis
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remarkably complete skeleton, best-known australopithecine, found in East Africa 4-3 mya, fossils indicate habitats ranging from woodland to dry savanna, and that there was pronounced sexual dimorphism
Lucy
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species represented by the Lucy fossil, one of the earliest bipeds
Australopithecus afarensis
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individual with a flatter face than earlier australopithecines. Nomenclature is questioned.
Kenyanthropus platyops
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possibly earliest australopithecine to use tools (2.5 MYA)
A. garhi
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“Southern ape ofAfrica”
• Found in South African cave and cliff deposits in a cement like matrix (breccia).
• Probable descendant of A. afarensis that migrated south
Taung Child, 3 yr old, discovered 1924
Australopithecus africanus
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Proper term for robust Australopithecines
Paranthropines
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• Anatomically specialized for hard-object diet: nuts and tough fibers. Also ate some meat.
• Maximized muscles of mastication produced flared zygomatic arches and postorbital constriction.
Robust Australopithecines
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-Small brained animal with prognathic face and large anterior teeth.
-Primitive, possible ancestor of later robust individuals who share a set of traits with this species.
-Locality: Lake Turkana
P. aethiopicus
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• Robust individual who shared some features with A. aethiopicus.
• Highly specialized with a wide East African distribution.
• Locality: Kenya, Tanzania, Ethiopia
P. boisei
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• Discovered in 1938 ata time when scientists doubted early hominids lived in Africa.
• Robust individiuals but smaller than A. boisei.
• Locality: Kromdraai, Swartkrans, Drimolen
P. robustus
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2 outcomes of >1 species occupying the same habitat
- 1. Diversify
- 2. Compete for food, with one becoming extinct
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Defining traits of the genus Homo (4)
- Rounded braincase
- Reduced post-orbital constriction
- Reduced lower facial prognathism
- More anteriorly situated foramen magnum
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“Handy man” since found in association with stone tools
Much larger brain? ~50% > compared to Australopithecines
Findings restricted to Olduvai Gorge
Homo habilis
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-Consist of cores (river cobbles) or source material from which flakes are removed by striking with a hammerstone
-Include flakes or small fragments, extremely sharp and useful in butchering meat or slicing through animal hide.
Oldowan tools
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• A major shift in hominid lineage took place about 1.8 MYA from H. habilis
• Bigger bodies
• Longer legs
• A modern-like gait
• A larger brain and uniquely shaped skull
Homo erectus
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used Acheulean tools, earliest evidence of controlled fire, diet included both plants and animals to sustain brain size and body size increase
H. erectus
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Have a blend of H. erectus and H.sapiens traits (mosaic evolution)
Robust bodies and large faces
Larger brain, more sapiens-like skull
Large, arching brow ridge
Large nasal aperture
Thick-boned cranial vault
Inflated cheeks
Homo heidelbergensis
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Larger cranium than modern humans, Short limbs, short fingers, but broad chests and broad pelvis
Neanderthals
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Direct ancestors of modern Europeans, contributed some genes to modern human populations were completely replaced by modern humans without contributing any genes to contemporary populations
Neanderthals
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Behavioral traits include making stone tools, Coping with cold, Hunting and subsistence, Cannibalism, Burying the dead, Ritual and symbolic performance and expression
Neanderthals
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size, sexual composition anad spatiotemporal cohesion of a society
social organization
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3 aspects of a social system
- social organization
- mating system
- social structure
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pattern of social interactions and social relationships of members of a society
social structure
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5 reasons to form groups
- predator protection
- resource defense
- foraging efficiency
- improved cargiving opps
- infanticide protection
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composition of a social group
social system
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determines the number of sexual partners that individuals have
mating system
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social system in which individuals forage separately to increase efficiency, but sometimes sleep near each other
dispersed/solitary
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social system in which individuals feed, travel, and sleep together
cohesive
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system in which individual females occupy very large and exclusive ranges where other females are not tolerated. The best option for males is to pair up with a single female
monogamy
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characteristics of monogamy (6)
- Low M-M competition
- Low SD
- High PI
- Egalitarian
- Small home ranges
- Arboreal
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system in which a female lives in a reproductive or social unit with more than one male
polyandry
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reproductive skew, SSR, OSR, and female choice influence the intensity of _______________
male-male competition
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canine dimorphism is dependent upon what type of ratio?
socioeconomic sex ratio
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body size dimorphism depends on what ratio?
operational sex ratio
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sex differences in schedule of development
bimaturism
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aspects of morphology that reliably indicate male survival ability, pathogen resistance, etc.; they also indicate how a male's offspring will do
handicaps
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examples of handicaps
- ornament size
- color intensity
- ornament elaboration
- degree of asymmetry in bilaterally symmetrical structures
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Male reproductive tactics (5)
- Dominance
- Coalitions w/other males
- Mate guarding
- Sneaky males
- Sexual coercion
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stage in which dominance is established via aggressive competition among individuals
initial stage
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stage in which members arrange themselves into a transitive hierarchy based on the outcome of the many individual contests among individuals
equilibrium stage
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relationship between individuals in a group, not inherited genetically
dominance
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what conditions must be in place for animals to fight?
if the probability of winning the fight X value of the resource outweigh the cost of fighting
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short-term association of 2 or more males
coalition
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long-term coalition of 2 or more males
alliance
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a male and female who maintain an exclusive relationship, highly variable in duration, usually to facilitate mating opportunities and ensure fertilization
consort
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extreme is forced copulation; more common is intimidation, harassment, and aggression directed at female to induce her to copulate willingly
sexual coercion
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adaptive strategy among non-human primate males in which they kill a female's infant in order to induce ovulation and bring her out of lactational amenhorrea sooner
infanticide
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most muscular tube in the male body
vas deferins
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provide transport medium (fluid) for spermatozoa during ejaculation
seminal vesicles and & prostate gland
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5 potential hypotheses for evolution of male genitalia
- lock and key hypothesis
- genitalic recognition
- pleiotropism
- mechanical conflict of interest
- female choice
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occurs in female spider monkeys, has a function in scent marking/attracting mates, in fission-fusion structure, similar to fx of swellings
clitoral hypertrophy
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filtering mechanism of females that is 1-2 cm in humans, function is not entirely understood
uterotubal junction
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ovarian end of oviduct
fimbria
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removal of sperm plasma membrane
capacitation
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a sperms' rapid figure-8 movements that may help to break away from the pack
hyperactivation
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escape of the acrosomal contents
acrosome reaction
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Characteristics of the primate order?
- grasping hands and feet
- nails instead of claws
- hindlimb-dominated locomotion
- increased reliance on vision
- reduced dependence on olfaction
- extensive female investment in offspring
- large brains
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