anthro exam 2

epidermis

thin outermost layer of the skin.

what are the two kinds of cells in the epidermis?

keratinocytes and melanocytes

keratinocytes

produce keratin, which gives protection against losing water and abrasion. this is the majority of cells in the epidermis.

melanocytes

produce pigment melanin.

melanin

produce a given amount of baseline pigment, which can be further increased by UV light stimulation (tanning). the number of melanin producing cells is same in all humans - but amount of melanin deposited varies.

melanosomes

pigment containing orgnelles in the melanocyte. in dark skin, melanosomes are larger, more numerous, and less "clustered." this means the color of skin is dependent on melanin pigment production.

other factors that can impact skin color

hemoglobin (blood protien-pink protien) and keratin (yellowish protien in skin and hair)

how many genes are involved in skin color

at least 14

skin color shows a ___ distribution.

clinal. = variation along an environmental gradient.

what is the environmental factor that can affect skin color?

ultraviolet radiation

ultraviolet radiation

= high energy and non-visible radiation contained in sunlight. excess causes dna damage, premature aging, surpressed immune system, skin cancer. UV intensity is highest at the equator, decreases towards poles.

three theories of correlation of uv and skin pigment

1. skin damage and skin cancer thoery

2. nutrient photolysis theory

3. vitamin d synthesis

skin damage and skin cancer theory of UV/pigment

sunburn destroys the skin cells, increases rate of skin infection. can lead to skin cancer, which can lead to death. natural selection therefore favors more melanin production in areas of higher UV to prevent cancer and death.

nutrient photolysis theory of UV/pigment

some essential nutrients break apart (photolysis) when exposed to UV radiation. natural selection favors darker skin which protects from nutrient photolysis. for example folic acid is necessary and your body will put up defenses if something is decreasing the supply.

vitamin D synthesis theory of UV/pigment

explains lighter skin tones in more northern latitudes. vitamin d is essential for calcium metabolism and normal bone/teeth development. but in an unsupplemented diet, it can be difficult to obtain. another way you can get it is synthesis within the skin. done through the interaction of UV light and a cholesterol-like substance found in epidermal cells.

ex. if you live in Scandinavia, you might have a hard time creating vitamin D- so depigment the skin so that it can do vitamin D synthesis. natural selection favors lower melanin production to make the best use of scarce UV for adequate vitamin D synthesis. rickets = disease affecting children with vitamin d deficiencies- impaired mineralizationn of developing bones and teeth.

sickle cell anemia

another trait that varies geographically like skin color. condition that results from a single nucleotide difference in hemoglobin gene that is involved in carrying oxygen- instead of a round shape, its shaped like a sickle. sickle cells dont move inside blood vessels as easily as normal cells, especially in smaller capillaries, so they often cause clots and organ failure- death.

much more common in pockets in india, middle east, equitorial africa. associated with prevalence of malaria. in the process of cells going through the sickle formation leak lots of potassium, which with surplus, can help someone to fight off malaria.

bergman's rule

individuals living in colder habitats tend to have larger body sizes- less heat lost through body surface.

allens rule

limbs and other extremities tend to be longer relative to body size in warmer climates to dissapate heat.

ancestral traits of primates and mammals (features primates share with all mammals)

- mammary glands

- homeothermy (maintaining consistent temperature)

- heterodonty (diff kinds of teeth in one mouth)

- expansion of the neocortex

- placenta (w/ long gestation and live birth)

- intensive maternal care

what are the three major groups of mammals

eutherian mammals

marsupials

monotremes

eutherian mammals

placental mammals, 18 diff orders, includes primates

marsupials

pouch animals- born very early and cared for in a pouch

monotremes

egg laying mammals

what kind of diversity is found in primates

body size

habitat

social structure and mating systems

diet

activity cycle

derived homologies

present in most recent ancestors but not more distant ones, appeared recently

derived homologies of primates

petrossal bulla.

grasping ability in hands and feet.

nails instead of claws.

sensitive tactile pads.

decreased reliance on olfaction.

steroscopic vision and enhanced depth perception.

large brain relative to body size, expanded neocortex.

ancestral homologies

generalized body plan.

generatlized detention (heterodonty).

primate locomotor adaptations

quadrepedalism (limbs are nearly equal in length).

suspensory (short hindlimbs and elongated forelimbs, good for swinging on branches).

knuckle walking.

primate dental adaptations

generalized detention that allows them to process most types of food.

teeth in lower and upper jaw.

bilaterally symmetric.

heterodont detention.

primate dental classes

anterior teeth for ingestion (incisors and canines), posterior teeth for chewing (premolars and molars)

diff. dental adaptations for different diets

insectivory (have sharp teeth to puncture outer skeleton)

frugivory (low cusps for crushing soft fruits)

folivory (well developed shearing crests for leaves)

what are the two major groups of primates?

strepsirrhines (dry nose) and haplorhines (wet nose)

what are the strepsirrhine primate groups?

lorises and galagos, lemurs.

what are the haplorhine primate groups?

tarsiers, platyrrhines, cercopithecoids, and apes.

what are the ancestral and derived traits and main locations of all strepsirrhines?

location: madagascar, central and southern mainland africa, SE asia.

ancestral mammalian traits: well developed sense of smell, unfused lower jaw, tapetum lucidum.

derived traits: nails and grooming claw on 2nd digit of hind limb, tooth comb, post-orbital bar.

what are the derived traits and main locations of all haplorhines?

location: central and south america, africa, asia, europe.

derived traits: no tapetum lucidium (sleep at night), reduced olfaction (= no rhinarium, lower jaw fused), tooth comb, enhanced vision (=eyes face forward, post-orbital closure, larger relative brain size)

lorises and galagos (strep)

- africa and asia

- nocturnal

- variety of diets

- mostly solitary or in pairs

- like to stay hidden to avoid predators

galagos, lorises, pottos

lemurs (strep)

- madagascar

- extremely diverse, some in large groups some in small groups

- females = dominant

- vertical clinging and leaping

aye-aye

tarsiers (haplo)

- SE asia

- grooming claw

- unfused lower jaw

- nocturnal, small social groups

- adaptions for vertical clinging and leaping

- large eyes relative to body size

platyrrhines (haplo, arthropoid)

- "flat nosed" w outward facing nostrils

- americas

- hind limb length = fore limb length

- long tails to aid in balace in trees

- shoulder blade positioned to the side of the ribcage

- smaller body size

- 3 premolars

- arboreal

- 2 color vision

owl monkey, marmosets, tamirins, capuchins, golden faced saki, spider monkey

cercopithecoids (haplo, catarrhine)

- "down nose"- narrow, down facing nostrils

- africa and asia

- larger body size

- 2 premolars

- arboreal and terrestrial

- sexual swelling

- trichromatic vision

colobine monkeys, cercopithecines

apes (haplo, hominoids)

- larger body size

- no tail

- build nests in trees to sleep at night

- large brains, enhanced cognition

- prolonged development

- postcranial adaptions for suspensory posture and locomotion = short hindlimbs, elongated forelimbs, mobile shoulder joint, shoulder blade in back, long and curved fingers)

lesser apes (gibbons and siamangs), great apes (orangutanas, gorillas, chimpanzees and bonobos, humans)

where do primates get their nutrients?

- carbs from fruits and gums

- fats and oils from animal prey like insects, nuts, and seeds

- protien from insect and animal prey, leaves

- fiber from leaves

costs and benefits of sociality

costs= greater competition for resources and vulnerability to disease

benefits= enhanced access to resources, reduced vulnerability to predation

resource defense model

- primates live in groups because they are more successful in defending access to resources than lone individuals.

- useful when: 1. food items are valuable. 2. food sources are clumped in space or time. 3. there is enough food within defended patches to meet the needs of several individuals. (fruit often meets all three requirements)

- primates often compere with members of other groups

- larger groups = more successful

*can lead to dominance hierarchies (food, mates, allies)

predator defense model

- group living evolved as a defese against predators. (primates have lots of predators, so this would significantly decrease mortality)

- larger groups found in terrestrial spaces rather than arboreal spaces

- change their behavior in response to the risk of predation (alarm calling)

*weakness of model = predation is difficult to observe, so we cant be 100% sure

mating systems v. social organization

mating systems = mongamy, polygamy, polyandry, and polygynadry

social organization= broader term- solitary, pair, or group living

reproductive strategy for solitary primates

female lives with offspring, males are soiltary

reproductive strategy for paired primates

males dont invest much effort in courtship or mating, incest heavily in offspring and maintaining bond with mate.

reproductive strategy for single-male, multi-female groups of primates

males compete actively to establish residence in groups of females. resident males are constantly under threat of competition with outside bachelor males.

reproductive strategy of multimale, multifemale groups of primates

male- male competition is regulated through dominance relationships- which is associated with individuals rates of reproductive success. females prefer males with higher mating success.

dominance

measured as the direction of approach-retreat interactions, direction of submissive and agressive behaviors

contest competition

dominance rank may determine priority access to preferred resources, increase reproductive success of high ranking individuals.

occurs when access to a resource can be monopolized.

some individuals exclude others and obtain more resources.

scramble competition

occurs when reosurces cannot be monopolized.

first come, first serve basis.

resources are of a low value, highly dispersed, or occur in large patches.

reproductive potential

the maximum number of offspring an individual can produce

female methods of increasing reproductive success

limited by access to important resources and long duration of gestation and early care (can only be pregnant so many times)

1. investing more time and energy into the offspring

2. choosing a high-quality mate

male methods of increasing reproductive success

lots of variance in strategies, can be limited by access to females.

1. increasing number of mates - done by engaging in male male competition.

sexual selection

a form of natural selection that occurs when individuals differ in their ability to compete with others for mates or to attract members of the opposite sex.

(natural selection favors the ones who are good at sex and producing offspring)

intrasexual selection

competition among sex individuals for access to members of the opposite sex.

favors large body size, large canine teeth, etc.

also leads to high levels of body size and canine sexual dimorphism. (as competition increases, male selection favors bigger ones, females stay same, gap gets larger)

sperm competition- also may favor those with increased sperm mobility and production (testes size)

intersexual selection

individuals exert choice among indivisuals of the opposite sex for mating partners.

favors traits that make males more attractive to females (indicators of better genes)= ex. symmetry- beauty = better features= better ability

paleontology

study of extinct organisms based on their fossilized remains

fossil

preserved remains of once-living organisms. rare event, conditions must be perfect for fossilization.

the matrix in fossilization

skeletons become fossils by absorbing minerals from their surroundings. the matrix composition is critical for analyzing and dating fossils.

what are three types of fossil dating?

relative dating, absolute dating, paleomagnetism

relative dating, define and types

using principles of stratigraphy (rock layers).

establishes relative ages between localities.

- lithostratigraphy, tephrostratigraphy, biostratigraphy

lithostratigraphy (relative dating)

characteristics of rock layers determine relative ages within sites)

tephrostratigraphy (relative dating)

using chemical similarities of volcanic ash layers to determine time equivalence

biostratigraphy

using the organisms themselves to establish relative ages across sites (looking at index fossils)

absolute dating, define and types

techniques that estimate the age of a fossil in absolute terms, through the use of a natural "clock" such as radioactive decay, or isotopes.

- paleomagnetism, magnetic barcodes

paleomegnetism

using changes in the earths magnetic polarity to establish age

magnetic barcode

pattern of reverse and normal polarity help link unknown geological sections to known timescale

effects of continental drift on primate origins

positions of continents changes over time, effects climate and movement/distribution of animal species

traits of early primate fossils

petrosal bulla.

highly derived hands and feet - grasping hands and feet, flat nails instead of claws).

decreased reliance on smell - smaller nose.

increased reliance on vision - forward facing eyes, post orbital bar protects eyes.

hypothesis for the adaptive origins of primates

arboreal - evolved as adaptations to the arboreal lifestyle of ancestors.

visual predation- visual adaptations stem from stalking and grasping insect prey, reduction of olfaction = biproduct of this.

angiosperm exploitation - emerged to help reap more benefits flowers, fruits, and organisms that dwell with or eat flowers and fruits.

*all hypothesis are true to a degree and contribute to primate origins, not just any one.

human mosaic evolution

diff traits of modern humans evolved at different times.

major anatomical effects of bipedalism in humans

center of gravity is situated directly in the midline, only minimal muscle activity is needed to maintain standing posture.

proportion of legs and arms favors longer legs for increased stride strength.

vertebral column has two curves (cervical/thorasic and lumbar)

pelvis shaped wider, more basin shaped. shorter, broader, curved iliac blades. repositioned cluteal muscles, improved lateral stability.

valgus angle in knee, angled femur.

human detention formula

- 2.1.2.3

- y5 molar pattern

- overall reduction in canine size and sexual dimorphism in canine size

- parabolic dental arcade

- smaller incisors than apes

- less facial prothagonism (flatter face)

adaptive explainations for bipedalism

social- ability to provide for family improved by bipedalism.

ecological- allowed for more efficient moving across forested patches and expandind savannas, better for finding food and spotting predators.