Midterm 2 Flashcards
The main levels of taxonomic hierarchy?
Kingdom, Phylum, Class, Order, Family, Genus, Species
*The full classification of our species
- Kingdom: Animalia
- Phylum: Chordata
- Class: Mammalia
- Order: Primates
- Family: Hominidae
- Superfamily: Hominoidea
- Tribe: Hominini
- Genus: Homo
- Species: sapiens
*the taxonomic classification of the primates
SEE picture on phone
Explain the trade-off between number of offspring and investment in offspring
The trade-off between number of offspring and the investment in offspring is a key concept in evolutionary biology, as it involves a balance between quantity and quality of offspring. Species that produce more offspring (r-selected) may have lower individual investment in each one, while species with fewer offspring (k-selected) tend to invest more resources into ensuring their survival and success
Concept of life history
How different stages of growth and development are typically distributed across the lifetime of an animal
- How much time is spent as an infant?
- How much time is spent growing?
~ When do teeth erupt (weaning; independence from mother)
~ When do bones fuse (adult size)
- When does reproduction start!?
*Generally thought about as a trade-off
What does it mean to say a primate species has a slower life history vs. a faster life history?
Life history theory predicts that certain strategies are optimal in certain situations
-Grow quickly, reproduce early, be small
- Grow slowly, reproduce late, be big
Primates have a slower life history compared to other mammals, which allows for increased opportunities for learning and social interactions. This prolonged development period likely contributed to the development of complex social structures and behaviors in hominid populations.
What biological features do primates share?
- Grasping hands and feet (5 fingers and toes; thumb and “big” toe position)
- Nails instead of claws (distal phalanx)
- Pronation and supination ability (radius and ulna; tibia and fibula)
- Binocular and stereoscopic vision (eye orbits facing forward)
- Color vision in cones (ability to see red; for fruit? for sex?)
- Reduced reliance on smell (reduced snout)
Why are social groups and social behavior so important for most primates?
- Safety and defense (strength in numbers)
- Other individuals around to do stuff; potential for cooperation; potential for exploitation
- Food gathering
- Pool of potential reproductive partners
- Decreasing predation risk
- Easy to defend good food sources
In what ecological niche do we think the earliest primates evolve?
Tropical rainforests
What biological features are present in the strepsirrhines that are more primitive than the haplorhines?
means “wet nose”
- lacks color vision
- rely on smell (large snout)
- nocturnal
- grooming claw
- partially open orbits
- mandible with suture at midline
What biological features are more derived in monkeys and apes than in strepsirrhines?
means “dry nose”
- color vision
- small snout
- diurnal
- no grooming claw
- closed orbits
- no mandible with suture at midline
Platyrrhines dental formula
2.1.3.2-3/2.1.3.2-3
Catarrhines dental formula
2.1.2.3/2.1.2.3
What is the difference between an ape (a hominoid that is not a hominin) and a monkey (a catarrhine this is not a hominoid)?
The main distinction between apes and monkeys lies in their anatomical features, with apes having no tails and larger bodies compared to monkeys
Pronograde vs. orthograde
A pronograde body plan means that an animal moves with its body parallel to the ground, with limbs extending out to the sides. This type of body plan is common in quadrupeds like dogs and cats, allowing for greater stability and agility while moving on all fours.
- in quadrupedal locomotion, the body is this
An orthograde body plan , on the other hand, involves an animal moving with its body perpendicular to the ground, with limbs extending vertically underneath. This body plan is often seen in primates like humans and apes, allowing for more efficient bipedal locomotion.
- in forelimb-dominated, below-branch suspension, the body is this
Below-branch suspension vs. over-branch quadrupedalism
Below-branch suspension involves hanging from branches using the arms, while over-branch quadrupedalism involves moving along branches using all four limbs. Both forms of locomotion are adaptations to life in the trees, with below-branch suspension allowing for greater stability and over-branch quadrupedalism providing more speed and agility
Why do apes tend to move around the trees by climbing or hanging below branches, whereas monkeys walk around on all fours above branches?
Apes are larger bodied and have longer arms than monkeys, which allows them to swing and hang from branches more easily without breaking the branches. Monkeys, on the other hand, have shorter arms and smaller bodies, making it more efficient for them to walk on all fours across branches
Example of an adaptation that helps apes move around by swinging below branches
- long arms relative to legs
- short, stiff back
- very mobile wrist
- wide shallow crest with shoulder blades on back
- long, curved fingers
Identify the Y-5 pattern vs. bilophodont patterns in lower molars
The Y-5 pattern is characterized by five main cusps arranged in a Y-shape, while bilophodont patterns have two main transverse ridges
Y-5 pattern is on lower molars on: “bifurcation is buccal”
In monkeys, mesial and distal cusp pairs are separated (bilophodonty)
Ecology
The study of how an organism’s biology relates to the environment– especially extracting resources from the environment
Niche
The ecological “space” an organism takes up
Generalist/specialist
Generalists are species that can thrive in a wide range of environmental conditions and feed on a variety of resources, while specialists are adapted to specific habitats and diets.
Generalist=broad
Specialist=very narrow
Frugivory/folivory
Frugivory
- fruits
Folivory
- leaves
Arboreal terrestrial
Arboreal
- live primarily in trees
Terrestrial
- live primarily on the ground
Cooperative breeding
Allomaternal care
- care of offspring by nonparents
Paternity is certain so there is less male-male competition (one breeding male and female)
Which primates are cooperative breeders?
Humans, marmosets, and tamarins
How does cooperative breeding affect the number of offspring that can be produced?
Increases net reproductive output
- can have more and more closely spaced offspring, despite longer periods of dependence because not only ones using energy to care for young
Principle of competitive exclusion
Principle of competitive exclusion states that two species competing for the same limited resource cannot coexist in the same ecological niche for an extended period of time. This leads to one species outcompeting the other, resulting in either the extinction of one species or a shift in their ecological roles
Example of niche partitioning in primates
- change physical space occupying
- change diet
- Nocturnal vs. diurnal (temporal change)
Ex. different species of monkeys will occupy different levels of the forest canopy, with some species specializing in the upper canopy while others stick to the lower levels. This allows each species to access different food sources and avoid direct competition with one another. By utilizing different parts of the same habitat, these primates are able to coexist and thrive in the same environment without overlapping too much in their resource use
Describe an example of a primate adaptation that allows that group/species to occupy a specific dietary niche
- physiological and soft-tissue anatomy changes
- behavioral changes
- skeletal changes
One example of a primate adaptation for occupying a specific dietary niche is the specialized dental morphology of leaf-eating primates like colobus monkeys, which have sharp ridges on their molar teeth to efficiently process tough, fibrous leaves. This adaptation allows them to extract maximum nutrients from their primary food source and thrive in their forest habitats
Describe how canine size, canine dimorphism, and the canine-P3 honing complex relate to social structures in living primates
Canine size in primates is often correlated with social behavior, with larger canines typically seen in species where males compete for dominance and access to females. Canine dimorphism, or differences in canine size between males and females, can also reflect social hierarchies and mating strategies within primate groups. For example, in baboon societies, males with larger canines are often seen as more dominant and have greater access to mating opportunities. Additionally, the presence of a canine-P3 honing complex, which sharpens the canine teeth through repeated contact with the lower third premolar, can indicate aggressive behaviors and social interactions within primate societies. This honing complex is more commonly found in species where males use their canines for display and intimidation, such as in gorillas and some species of monkeys. Overall, canine dimorphism and the presence of a honing complex can provide valuable insights into the social dynamics and reproductive strategies of primates
Explain how fossilization occurs from burial to discovery
1.) Burial under specific conditions
- quickly covered is good
- certain kinds of sediments are better than others
2.) Mineral replacement
- biological minerals are replaced by rock minerals (diagenesis)
3.) Exposure
Mineral replacement is in the middle of burial and discovery, but what is that?
Biological molecules and minerals replaced by rock materials
Stratigraphy
The sequence of layering of the various rock formations
Principle of original horizontally
Everything starts out roughly horizontal; disruption of horizontality is caused by later factors
Principle of superposition
Younger layers are deposited on top of older layers (superposition)
- a layer that cuts across others is younger than those it cuts
Relative vs. absolute dating
Relative dating involves determining the age of a rock or fossil based on its position in relation to other rocks or fossils, while absolute dating provides a specific age in years. Relative dating is often used when the exact age of an object cannot be determined through absolute dating methods, which are the more preferred methods
Example of relative dating
Biochronology
- relies on the law of superposition:
*The sediment layers at the bottom are the oldest, those on the top are progressively younger
*Establishes a sequence within the site
*Fossils that appear in the bottom strata are older than fossils in the top strata
Example of absolute dating
Radioisotopic dating: based on radioactive decay of elements
Radiometric dating
using the decay of radioactive isotopes to determine the age of fossils and artifacts
Parent element
Element before decay
Daughter element
Element after decay
What starts the radiometric clock?
Some event related to death or burial of an organism starts the radiometric clock and the daughter element begins accumulating
Is radiometric decay constant or variable?
Constant on average
What is half-life?
the average length of time it takes for half of a sample of parent to decay to daughter
What can age be calculated based on?
Knowledge of the half-life and the observed ratio of the parent to daughter
How is volcanic activity involved in Argon-based dating methods?
Rocks heated to high temperatures (volcanic temps) release all argon and start the clock of argon accumulation
- the volcanic rock layers above and below a fossil are dated by using the half-life of Potassium isotope to decay to Argon isotope
- slower decay rate means it can be used to date much older things
What is the molecular clock?
The molecular clock in paleoanthropology is a method used to estimate the timing of evolutionary events based on changes in DNA sequences over time. By comparing genetic differences between species, researchers can determine when these species diverged from a common ancestor
- combines phylogenetic and genomic analyses, calibrated by fossils to estimate when living animals last shared a common ancestor
What is a divergence date?
refers to the estimated time when two species or populations of hominins split from a common ancestor
When does molecular evidence suggest the human and chimpanzee lineages diverged?
4.5 Ma
How are fossils involved in the molecular clock (calibration)?
Fossils are used to provide a minimum age for specific branches on the tree of life based on morphology, allowing researchers to estimate when certain genetic changes occurred.
*By combining fossil data with genetic data, scientists can calibrate the rate at which mutations accumulate over time, providing a timeline for evolutionary events
Cenozoic Epochs and boundary dates
(from bottom/oldest and up)
Paleocene 65.5
Eocene 56.5
Oligocene 34
Miocene 23.3
Pliocene 5.2
Pleistocene 2.6
Holocene 0.01
“Put Eggs On My Plate, Please Honey”
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
What epoch did the earliest primate-like mammals originate?
Paleocene Epoch
Know which epoch primates originated in
Ex. Euprimates –> Eocene
Euprimates –> Eocene
Which epoch hominoids originated in
Hominoids originated in the Miocene epoch, approximately 23 to 5 million years ago
What epoch hominins originated in
Pliocene epoch
What epoch did Homo originate in?
Pleistocene epoch
How can we reconstruct the temperature of the earth in the distant past?
Global temperature curves are built from oxygen isotope data
- The more 18 Oxygen found in the sediment, the colder the climate, the more 16 Oxygen, the warmer the climate
Oxygen isotopes are helpful for reconstructing how____
1.) cool and dry vs.
2.) warm and wet
An environment is
Carbon isotopes from paleo-sites are helpful for understanding whether the plants growing in an area were_________ vs. __________.
trees and bushes (closed environment) vs. tropical grasses and sedges (more open environments)
“You are what you eat”
What is a hominin?
- any species on our side of the split
- a member of the taxonomic Tribe Hominini
When do we think human evolution started (about how many million years ago)?
6-7 Ma
How old are the oldest hominin fossils?
4.2 Ma
What are the characteristics of hominins?
- distribution
- population size and density
- reliance on material culture
- genetic uniformity
- cognition
- bipedalism
- sex & social organization
- relatively large brain
- diet
- longer gestation, later age at maturity
- unique body proportions
How can we identify a hominin in the fossil record?
1.) Skeletal evidence of bipedalism
2.) Skeletal evidence of reduced, non-honing canines and low canine dimorphism
Skeletal evidence of bipedalism
Indicators can be found in:
- skull
- spine
- pelvis
- legs
- feet
What is the canine-P3 honing complex?
functions to keep canines sharp
- large dagger-like upper canine, diastema, and asymmetric third premolar (P3)
- the back side of upper canine wears against the front side of the lower P3, keeping canine tips sharp
What do the reduced, non-honing canines of hominins imply, with regard to social structure and reproductive biology?
The reduced, non-honing canines of hominins suggest a shift towards a more cooperative and less aggressive social structure rather than intense male-male competition for females. Additionally, this change may reflect a shift towards pair bonding and monogamous relationships in hominin reproductive biology
Reduced canine dimorphism means that there is less sexual selection pressure on males to have large, sharp canines for competition, indicating a shift towards a more peaceful and cooperative social structure. This may also suggest that females choose mates based on other factors besides physical aggression and dominance
Australopiths
group of Plio-Pleistocene hominins characterized by a combination of ape-like and human-like features
Where were australopiths found and when did they exist?
They originated sometime before 4.2 Ma and lasted until about 2.0 Ma (gracile) and 1.2 Ma (robust)
What are the characteristic features of Australopiths?
- Ape-sized brains
- subnasal prognathism (jaws that stick out in front of the face)
- Smaller than living humans
(- long arms, short legs)
Derived
- bipedal
How big are australopiths?
Ranged in stature from 3’6’’ - 5’6’’
Were australopiths dimorphic in body size?
Yes, australopiths were dimorphic in body size, with males typically being larger than females, however, there were no signs of the canine size dimorphism we see in gorillas and orangutans
HIGHLY dimorphic in body size BUT NOT in canine size!!!
Upper limb morphology of australopiths
Australopiths have primitive limb proportions, compared to living humans
- long forearms
- long, curved fingers
- upward facing shoulder joint
Was there evidence to support australopiths being bipedal?
Yes!
- There is behavioral evidence from Laetoli footprints are indisputable evidence that a bipedal hominin walked across this layer of volcanic ash in 3.6 Ma
- There is behavioral evidence from the knee
- There is evidence from the pelvis
Yes, there is evidence to support the theory that australopiths were bipedal, including the structure of their pelvis and foot bones which suggest adaptations for walking upright. Additionally, studies of their fossilized footprints have shown characteristics consistent with bipedalism
Australopiths had non-dimorphic canines. What does that imply about structure and reproductive biology?
Non-dimorphic canines in Australopiths suggest that there was likely less competition among males for mates, as they did not need to rely on physical displays of dominance. This may indicate a more cooperative social structure and potentially a more monogamous reproductive system compared to species with dimorphic canines
What function does the Australopithecus sagittal crest serve?
An extension of bone on the cranium that provides attachment surface for extra large chewing muscles
What did robust australopiths eat and how do we know that?
Robust australopiths show major anatomical adaptations and isotopic evidence of eating some (or a LOT) of foods derived from grasses since extreme chewing adaptations to aid in digestion of such tough food items
Carbon isotopes can help us know if an extinct animal was eating foods derived from___________ vs. ___________.
grassy-style plants vs. foods derived from tree/bush style plants
