Chapter 16-20 Flashcards
Define fossil
- anything that is evidence of life that lived long ago
- any preserved remains/traces of organisms
General ways fossils are formed (4)
- drifting sand
- mud deposits (river)
- volcanic ash
- buried by another organism (burial)
What are fossils generally made of? why/how do they consist of these materials?
limestone
ion oxide
- flesh rots away leaving a cast - minerals are deposited into the poor replacing the organic material
- becomes petrified and turned to rock
Define petrified
Organic material that has turned into stone by replacing
What are the (4) conditions for a fossil to be formed?
- buried quickly - to delay decay and deposits
- alkaline soils - ideal, means that minerals in bone don’t dissolve
- lack of oxygen - oxygen needed to decompose
- hard body parts
General (3) locations for fossils
- edge of lakes, rivers - build up of sediments from flooding/flowing water over fossil to bury it
- caves - limestone containing of calcium carbonate - collapsed roof eg
- ash - volcanic eruptions which burry humans/animals
Name of ppl who discover fossils
anthropologists
- find fossils of artefacts (tools, beads, carvings…)
List 4 types of absolute dating
- potassium-argon dating
- carbon-14 (radiocarbon) dating
- Accelerator mass spectrometry (AMS) radiocarbon dating
- Dendrochronology (tree-ring dating)
Potassium-argon dating use and description (what/process)
- volcanic rock only
- Isotope - different forms of the same element with different neutron numbers in nucleus of atoms
- potassium (K) - mixture of three different forms with different atomic weights
- isotope potassium-40 is radioactive and decays at a fixed rate - forms carbon-40 and argon-40
- determining amount of potassium-40 and argon-40 - can calculate age
Limitations/restrictions/conditions for potassium-argon dating
- only volcanic rock
- older than 100,000-200,000 years - anything younger would have too little decay to determine
- require suitable rock of same age as fossil to be found
Carbon-14 (radiocarbon) dating use and description (what/process)
- is the decay of the radioactive isotope (carbon-14 to nitrogen)
- young samples
- organic materials
- carbon-14 is produced in upper atmosphere where by cosmic radiation, turns to nitrogen at same rate it decays
- plants take in carbon (1 carbon-14 for every million -12) and animals eat plants
- when dead, -14 decays at a fixed rate, no more is taken in
- HALF LIFE - decays to half the amount after 5730 years)
Limitations/restrictions/conditions for Carbon-14 (radiocarbon) dating
- younger samples
- up to 60,000-70,000 years
- 3g at least
- organic material
Accelerator mass spectrometry (radiocarbon) dating use and description (what/process)
- more refined
- dates small samples - as small as 100 micrograms
- breaks up sample into its atoms so they can be counted
- for cave paintings eg - pigments, honey, charcoal, oil, blood
- for artefacts - tools, fire charcoal
Limitations/restrictions/conditions for Accelerator mass spectrometry (radiocarbon) dating
- very small fossils
- 100 micrograms +
- recent - younger than 60,000 years
must contain carbon - organic material
-14, -12 ratio is not constant
Dendrochronology (tree-ring dating)
- Using tree rings to determine years
- Each ring represents one years growth
- Rings vary in width compared to favourability of growing season
- Correlate marker rings with timber taken from ancient human structures - determined age of these human structures
- Small sample drilled from trunk and counting rings
- Combined by radiocarbon dating
Dendrochronology (tree-ring dating) limitations/restrictions/conditions
- Only determine age of tree/wood
- Timber is rarely preserved for more than a few thousand years
- Necessary conditions rarely occur
- Up to 9000 years old
List 3 types of relative dating methods
- fluorine dating
- phylogenetic trees
- stratigraphy
What is stratigraphy
- study of layers of strata
1. Principe of superposition - assuming that top layers are youngest - are complications though
2. Correlation of rock strata - matching layers of rocks from different areas - examining rock itself first then fossils in it
Define index fossil
widely distributed - on earth for a limited period of period
Materials found with stratigraphy
bones, teeth, petrified wood/log, coral, insects, trilobite
Limitations of stratigraphy
- Natural disasters - tsunamis
- Earth plate movements
- caution because sometimes layers are turned upside down - sometimes humans or animals are buried after deposition - may actually be younger than layers above
What is fluorine dating
- When bone is left in soil, fluoride ions present in the water in the soil, replace the ions in the bone
- The older the fossil, the more fluoride it contains
- Not absolute because fluoride in water in soils varies from place to place
Define binomial system
- use generic (genus) and specific (species) name
Define
evolutionary trends - gradual change in characteristics that occurred as primates became more highly evolved
Define hierarchy
- series of groups of species from broad to specific
- divided into orders/ groups known as phyla
2 types of primates
primitive and anthropoids
Define arboreal
living in a tree environment
List 8 general characteristic of all primates
- BODY - not specialised for anything particular
- LIMBS - unspecialised
- HANDS/FEET - pentadactyl (five fingers), nails instead of claws, prehensile (grasp), first digit opposable,
- EYES - 3D, forward facing, colour
- SMELL - poor
- TEETH - four incisors in upper and lower jaw
- BRAIN - large and complex, cerebrum size is larger
- REPRODUCTION - not restricted to a breeding cycle, rhythmic sexual cycle - month, year, One offspring at a time , Long period of parental care
List 5 evolutionary trends (NOT for erect posture)
- digits, dentition, smell, vision, brain, gestation/development
Digits - list 6 evolvements
- pentadactyl
- prehensile
- opposability
- nails
- friction ridges
- precision grip
Describe ‘prehensile’ as a trend
- grasping fingers
- Evolutionary trend is to be able to move them freely of each other
Describe opposability as a trend
- thumb can touch each finger - longest in humans
- Toe is opposable in primates – BESIDES humans - lost due to weight baring
- Degree varies between species
Describe nails as a trend
- shorter and flattened instead of claws
- Secure grip on trees
- Better grip on objects
- Some have single claw - toilet claw for scratching
- Receptors on tips
Describe friction ridges as a trend
- small pads with tiny ridges/folds to increase grip
Describe precision grip as a trend
- only in humans
- For holding pencils and sewing etc
- Precise, delicate movement
List 5 dentition evolvements
- change in dental formula
- dental comb
- number of teeth
- diastema
- cusps
Describe dental forumula as a trend
- number of each type of tooth
- Primitive mammals - 3:1:4:3 (3 incisors, 1 canine, 4 premolars, 3 molars) - Total of 44 teeth
- 36 teeth in lemurs, lorises and new world monkeys
- Human teeth - 2:1:2:3
- Total of 32 teeth
Describe ‘number of teeth’ as a trend
- Decrease in number of teeth - smaller face/head
- Large, sharp, pointy canines in old world monkey - humans are similar to other teeth
Describe diastema as a trend
- human don’t have anymore - change I diet and survival requirements
- gap between large upper and lower canines
- makes room for large incisors
- Premolar slants to give room for large incisors
Describe cusps as a trend
- evolve from 3 cusps to 4 in top molars (+ shape)
5 cusps in humans now - 5 cusps in lower molar (Y shape)
- Evolved due to change in diet - fruits
- Layer of had enamel covering teeth for protection from decomposition
Describe dental comb as a trend
- horizontal tooth bottom for grooming
- has disappeared now
List and describe 4 trends in vision
- olfaction - decreased smell segment and increase emphasis on vision section in brain
- Stereoscopic vision - eyes at from of head - moved forward
- was mandatory when arboreal - judge distance between trees - Eye socket - become enclosed to protect the larger nerve
- Rods and cones - night vision and colour - Improved nerves between rods, cones, and brain
Discuss ‘relative size of cerebral cortex’ as an evolutionary trend
- increased in size
- SIZE, CONVOLUTIONS, CEREBRAL SIZE
- Involved with higher functions - vision, memory, reasoning…
- Human average size - 1350cm3
- Larger brains in primates for;
- coordination as arboreal
- Special/social skills
- Finding food
- Identifying threats
- Larger and rounder with bigger brain and intelligence
- Convolutions - stronger pattern/more in humans
Discuss ‘Gestation and parental care’ as a trend
- Increased length between fertilisation and brith
- Increasing length that offspring is dependent off parent
- sexual maturity increasingly later development
State name for walking stance /motion
upright bipedal locomotion
Define tribe
given to relatively new level of classification
Brief order of primates (5) oldest to youngest
- Australopithecus africanus
- Australopithecus afarensis
- Homo erectus - standing upright
- Homo neanderthalensis
- Homo sapiens - humans
List 8 adaptations/trends for erect posture
- foramen magnum
- curvature of the spine
- jaw
- pelvis
- carrying angle
- knee
- foot
- centre of gravity
Compare the foramen magnum position / neck between apes and humans as a adaptation for erect posture
APE
- sits at back of skull - horizontal stance
- have large, strong neck/muscles to carry/support head
HUMANS
- sits in the centre of the bottom of the cranium
- in line with centre of gravity
- supported by vertebrae column
- has gradually moved forward because of erect posture
Compare the curvature spine between apes and humans as a adaptation for erect posture
APE
- flat, slight curved spine
- straight
- head protrudes off
HUMAN
- double curvature (two curves)
- S - shape
- CTLS / “STILTS” - cervical, thoracic, lumbar, sacral
- wedge of the lumber gives from froward to back - gives jutting curve
^ enables balance on neck
- brings vertical column directly under centre of gravity of skull
Compare the jaw between apes and humans as a adaptation for erect posture
APE
- protruding
- large size
- U shape
HUMAN
- flatter facial profile
- to balance head in the centre - so that head isn’t sticking out front/back more
- parabolic shape
Compare the pelvis between apes and humans as a adaptation for erect posture
APE
- elongated
- narrow
- consists of scrum, acetabulum, pelvis
HUMAN
- broader and shorter
- bowl shaped
- supports abdominal organs
- larger in women for passageway in birth
- space for bone and muscle attachment
Compare the carrying angle between apes and humans as a adaptation for erect posture
APE
- swayed walking
- acetabulum in light with inner knee joint
HUMAN
- tip of hip joint (hook) is directly above the centre of the knew joint - so busy weight can be transferred from pelvis to leg
- wider acetabulum = femur converges towards inside
- weight falls on outside of knee
- centre of gravity crosses over femur
- striding gate - hips and knee can be fully extended
Compare the knee between apes and humans as a adaptation for erect posture
- knee is a hinge joint with ligaments on either side
- centre of gravity is in line with front of knee and down the outside
- therefore force is trying to pull knee back but ligaments restrict bending in opposite direction
= hinge wants to bend forward - force wants to bend back = equals out for no energy
Compare feet between apes and humans as a adaptation for erect posture
APE
- able to grasp with foot
- opposability of big toe
- lower down and smaller big toe - not as big and important as humans for balance
HUMAN
- lost prehensility (grasping)
- big toe is large and aligned with others - for balance
- metatarsals for arch’s -longitudinal (front to back) and transverse arch (side to side)
Compare centre of gravity between apes and humans as a adaptation for erect posture
APES
- longer arms than legs - brings upper body down/slouched
- higher centre of gravity - chest region
HUMAN
- longer legs - concentrates gravity, increases length of stride/steps
- lower centre of gravity - hips/pelvis
Describe muscle tone in 3 areas
- striding gate - weight transferred from heel, along outside, crossing the ball and finishing at big toe
- foot is now weight baring not gripping - arm swinging - compensates for trunk rotations around pelvis
- Right arm swings at left step etc.
- Reduced energy expended - carrying angle - weight distribution towards central axis
Rotation of body at lower leg and foot - each footstep is more straight
Describe relative size of cerebral cortex as an evolutionary trend
- 1350cm3 - average human
- frontal lobe in humans is very large - think, planning, processing, reasoning
^ functions that don’t occur hugely in app - absence of forehead in apes & protruding brow bone
- cranium capacity measures brain size by endocasts
Prognathism & dentition as an evolutionary trend - APE VS HUMAN
APE
- protruding canines which are large and pointy
- dental arcade = U - shape
- diastema
- 2:1:2:3
- large brow ridge - instead of frontal lobe
HUMANS
- small canines - look like incisors
- parabolic shape
- 2:1:2:3
- small brow ridge
List 5 advantages of bipedal locomotion
- increase range of vision - food/predators
- increase in height - scaring predators
- hands free for carrying (food)
- higher reach
- improved body cooling
Why was there evolution from ape to bipedal locomotion/erect posture? (general)
- cooling
- 5 survival advantages
- change in climate
- change in environment - thinning of forests etc
- avoid over heating - less sun contacts with vertical stance
Australopithecine first fossil origin and time period
Southern Africa
Early 1920s
Australopithecine - first noticeable changes (8)
- brow ridge / lower forearm head
- rounder head
- less protruding jaw
- . less protruding teeth
- foramen magnum moving forward
- bipedal locomotion
- canine
- pelvis/femur
Name/ briefly describe two variants of australopithecines
- robust - taller and heavier
- large, broader molars & jaw
- bony crests in skull - Gracile - shorter, lighter
- proportioned head & jaw
- Australopithecus afarensis and Africanus
What is the other name for homo habilis - why that?
handyman
Features of homo habilis (5)
- larger brain
- smaller teeth
- taller
- stood more erect
- powerful grasp- still spent time in trees
