Anthro Inquisitive Notes
Chapter 1: Adaptation by Natural Selection
Darwin’s theory of adaptation follows from three postulates:
The struggle for existence. The ability of a population to expand is infinite, but the ability of any environment to support populations is always finite.
Variation in fitness. Organisms within populations vary, and this variation affects the ability of individuals to survive and reproduce.
Inheritance of variation. This variation is transmitted from parents to offspring.
Significant adaptations, such as a change in beak size or body weight, can occur over remarkably short periods of time (for example, 30 to 46 years).
Barring unusual circumstances, most new adaptations do not arise in a short period of time (for example, within a couple generations).
Incremental adaptations can take millions of years to occur.
Discontinuous variation examples:
Human achondroplasia
Human blood groups
Human albinism
Continuous variation examples:
Human skin color
Human hair color
Beak depth
Scientists can not use Darwin's theory of adaptation by natural selection to predict adaptations that an organism will experience next
Darwin couldn't explain how a population might evolve beyond its original range of variation
Theorized before Charles Darwin:
Organism complex traits are the result of divine creation
Organisms can pass changes on to their offspring
Contributed by Charles Darwin:
Small evolutionary changes accumulate to make large ones
Variation is what allows species to change over time
Major evolutionary change happens slowly
Chapter 2: Genetics
The process that leads to a new combination of traits is known as recombination.
E. coli have genes for lactose enzymes that are activated by regulatory genes when there is insufficient glucose available for the bacteria to metabolize.
DNA in regulatory genes determines when protein coding genes are expressed.
DNA affects the structure of several types of RNA.
DNA is not used as a structural protein in cell walls
DNA in protein coding genes affects protein structure.
Regulatory genes can inhibit the expression of protein coding genes by the use of a(n) repressor protein. When a regulatory gene wants the protein coding genes expressed, a(n) activator protein binds to the DNA sequence.
Crossing over: term for the process in which the genes on one chromosome are transferred to the other chromosome in a homologous pair?
A chromosome is inherited as a unit (after recombination); if genes affecting two or more characters are located closely together on the same chromosome, then those genes are more likely to be passed on together—such that the traits do not segregate independently.
Loci for different traits that are on different chromosomes are unlinked. However, loci for different traits that are on the same chromosome are likely to be linked.
Chapter 3: The Modern Synthesis
Goal of evolutionary theory is to determine how genotype frequencies change over time
Evolutionary change can occur through random genetic drift
Mate guardian is a male strategy to prevent other males from mating with an individual female
genotype frequencies must add up to 1.0 and the frequency of the heterozygote is 0.5, that means that the total of the two homozygote frequencies must also be 0.5. Since the frequencies of the two homozygotes are equal, each must have a frequency of 0.25.
For selection to occur, there must be variation within that character or trait. Otherwise, there would be no alternatives for selection to work on.
For a character to be subject to natural selection, it must be able to be inherited from one generation to the next.
Natural selection requires there to be an impact on reproductive success.
Correlated characters can occur because of pleiotropy
Some genes have a pleiotropic effect, meaning one gene affects more than one character.
A correlated response to selection can cause characters to change in maladaptive directions.
In some cases, the shift in one correlated character can lead to a shift in the other character; however, one of the shifts may be maladaptive
Correlated characters are nearly always positively correlated.
Although some correlations are positive (i.e., when one character increases, so too does the other), some correlations are negative (i.e., when one character increases, the other character decreases).
When selection changes the mean value of one correlated character, the other character's mean value will also change.
Although natural selection does increase the adaptedness of a population, it doesn't necessarily lead to the best phenotype.
Sampling variation is a function of genetic drift, wherein random changes in gene frequencies may occur in small populations.
Sampling variation is a function of genetic drift, wherein random changes in gene frequencies may occur in small populations.
Negative correlations refer to statistical relationships between two traits, in which the increase in one is associated with a decrease in the other.
Behavioral plasticity is most likely to evolve when environments are variable
Genetic drift causes more rapid change in small populations than in large populations.
Chapter 4: Speciation and Phylogeny
Evolutionary biologists do not agree about which are the most important factors that maintain distinct species. There is now considerable controversy about the processes that give rise to new species and the processes that maintain established ones.
The process that creates new species and higher taxa is referred to as macroevolution.
Occupying the same location is not enough information to determine if two animals belong in the same species. Sharing the same environment does not necessarily mean organisms will share all aspects of their morphology and behavior. They may have evolved in different locations and migrated to the same forest.
When reconstructing a phylogeny and deciding where to locate nodes and branch segments, it is important to identify the derived traits that distinguish species from other species that existed before them or that contemporaneously exist with them.
It is important to use derived traits (features that have evolved in a group of species since the last common ancestor of the species under consideration) when reconstructing phylogenies. Only derived traits provide us phenotypic evidence that a species has evolved and become distinct from its ancestral species.
Ancestral traits are traits that are retained from a common ancestor. Species retain or lose ancestral traits at different rates owing to varying rates of evolution. Even distantly related species can share ancestral traits. For this reason, ancestral traits should not be the basis for taxonomic grouping.
Gene flow and reproductive isolation are the basis of the biological species concept. If characters evolved this way, they are likely from the same common ancestor and should be used when constructing phylogenies for taxonomic groupings.
Used for taxonomic grouping
Similar characters are derived
Similar characters evolved due to geneflow
Should not be used for taxonomic purposes
Similar characters are ancestral
Similar characters evolved due to convergent evolution
Hybrids are selected against during the reintroduction stage of allopatric speciation.
reinforcement
Correct label:
Reinforcement
The extent of gene flow between the populations is reduced.
reinforcement
Correct label:
Reinforcement
Morphological and behavioral differences increase.
character displacement
Correct label:
character displacement
Competition over food, mates, or other resources increases morphological differences.
character displacement
As species adapt to different environments, their characters diverge from one another.
character displacement
Selection favors behavioral or morphological adaptations that prevent mating between members of the two populations in question.
reinforcement
Hybrids are usually less fit than nonhybrids. Therefore, selection should favor behavior or morphology that prevents mating between members of individuals from different habitats.
Adaptive radiation occurs when an organism—either animal or plant—diversifies and fills all available ecological niches. This phenomenon occurs when there are many available niches, such as on the Galápagos Islands.
analogous
bipedality in humans and chickens
homologous
hair in both humans and platypuses
no tails in both humans and orangutans
egg-laying in chickens and platypuses
lactation in both humans and platypuses
Biological Species Concept
Two populations with gene flow between them belong to the same species.
Species are made up of a reproductively isolated group of individuals.
Individuals within a species must be able to interbreed with each other.
Ecological Species Concept
Individuals of one species can interbreed with individuals from other species.
Two populations with gene flow between them could be different species.
Species are groups of individuals that adapt similarly to the same natural selection pressures.
The major difference is that microevolution refers to how populations change under the influence of natural selection and other evolutionary forces, while macroevolution refers to how new species and higher taxa are created.
macroevolution
parapatric speciation
sympatric speciation
allopatric speciation
Accumulation of small changes over large time scales
evolutionary changes that produce new species
adaptive radiation
microevolution
mutation
natural selection
genetic drift
takes place on small time scales (generations)
evolutionary changes occurring within a species
small shifts in allele frequencies
Challenge to the Biological Species Concept
Species boundaries are maintained even when there is gene flow between species.
Species are maintained owing to natural selection.
Species can be maintained without gene flow.
According to the ecological species concept, species boundaries can be maintained even when substantial amounts of gene flow occur between species. This is seen in populations that have fewer hybrid individuals than non-hybrid individuals.
Taxa in highest to lowest
Superfamily
Family
Genus
Species
According to the biological species concept, boundaries between different species are maintained by reproductive isolation. The ecological species concept emphasizes that boundaries between species are maintained by natural selection and can exist despite gene flow between different species.
Homegenizes Populations
gene flow
higher fitness of hybrids
similar selection pressures
Makes populations diverge:
reproductive isolation
different selection pressures
geographic barriers
lower fitness of hybrids
reinforcement
character displacement
Sympatric speciation occurs when natural selection favors different adaptations, even when a population is experiencing the same environment. Under the ecological species concept, it is the force of natural selection that is maintaining species’ boundaries.
Allopatric speciation occurs when there is a geographic barrier to gene flow, and a lack of gene flow is what maintains species’ boundaries under the biological species concept.
Parapatric speciation occurs when natural selection favors different adaptations to different environmental zones within a population’s home range. Under the ecological species concept, different selective pressures are maintaining the boundaries between species.
Homologous traits are similar due to descent from a common ancestor. Analogous traits are similar traits that have evolved independently in different lineages (not due to common ancestry). In the image, lactation is a homologous trait in humans and platypuses because they both inherited lactation from a common mammalian ancestor. Bipedality is an analogous trait in humans and chickens because they do not share a common bipedal ancestor. Instead, each species evolved bipedality independently.
Dolphins and sharks swim.
analogous
Rabbits and squirrels have fur.
homologous
Humans and monkeys have opposable thumbs.
Homologous
Chickens and sparrows have beaks.
Homologous
Bats and birds have wings.
analogous
Humans and chickens are bipedal.
analogous
Derived traits are very useful for constructing phylogenies because if two species share (by homology, not analogy!) a derived (recently evolved) trait, they must share a recent ancestor.
Ancestral traits are not useful for building phylogenies because they typically evolved long enough ago that numerous speciation events have taken place since the emergence of that trait. So, lots of species might bear that trait—some of them are more closely related than others, but you can’t tell from looking at ancestral traits. In addition, enough time has passed that some species may have lost the trait, further confusing relationships.
found in a common ancestor of the species being compared
ancestral
not useful for constructing phylogenies
ancestral
a relatively “new” trait
derived
evolved since the last common ancestor of the species being compared
derived
a relatively “old” trait
ancestral
very useful for constructing phylogenies
derived
Chapter 5
Derived traits of primates:
Most primates have opposable toes and thumbs that they use for grasping.
There are flat nails on the hands and feet in most species, instead of claws, and there are sensitive tactile pads with “fingerprints” on the fingers and toes.
Locomotion is hind-limb dominated, meaning that the hind limbs do most of the work, and the center of gravity is nearer to the hind limbs than to the forelimbs.
Unspecialized olfactory apparatus that is reduced in diurnal primates
Visual sense is highly developed. The eyes are large and move forward in the head, providing stereoscopic vision
Females have small litters, and gestation and juvenile periods are longer than in other mammals of similar size
The brain is larger than the brains of similarly sized mammals, and it has several unique anatomic features
The molars are relatively unspecialized and max of two incisors, one canine, three premolars, and three molars on each side of lower and upper jaws
Several subtle anatomical characteristics that are useful to systematists such as eye orbits that are fully encased in bone but that are difficult to interpret functionally
platyrrhine
Diurnal
Live in forested areas
Mainly arboreal
Quadrupedal
Round nostrils
Three premolars on each side of upper and lower jaws
Central and south america and southern mexico
Catarrhine
Narrow nostrils face downward
Two premolars on each side of upper and lower jaws
Larger than platyrhine species
Occupy larger variety of habitat than platyrrhine
Africa and asia
Where Primates Live Today:
Nonhuman primates do not live in the wild in Australia.
Living nonhuman primates are primarily located in tropical regions of the world.
Where they don't (not true statements below)
Both living and fossil nonhuman primates have been found distributed throughout most parts of Asia.
Living nonhuman primates inhabit a much wider region than their fossil ancestors did.
Fossil nonhuman primates were found in more equatorial areas than living nonhuman primates.
Strepsirrhines include the lorises, lemurs, and galagos. Haplorrhines include the tarsiers, monkeys, apes, and humans.
One-male, multifemale social groups are very common among primates and the term "polygyny" is often used as a shorthand describing the mating system in these groups.
An animal’s basal metabolic rate is the energy needed to regulate essential body functions. Energy is also needed to sustain growth, development, and reproduction.
At rest large animals use less energy per unit of body weight
The dental formula shows how many of each type of tooth a particular species has on one side of its jaw. The dental formula is written like this:
2.1.3.3
—----------
2.1.3.3
Usually, the dental formula is the same in upper and lower jaws of the same species. There are some exceptions, though, such as the tarsier, which has two incisors in the upper jaw and only one in the lower jaw.
Dental formulas are counted from front to back, starting with the incisors. This image shows the mandible of a male colobus monkey. To find the dental formula, start with the incisors and count on one side: two incisors, one canine, two premolars, and three molars, giving a dental formula of 2.1.2.3.
Hylobatidae
Smaller body size
Pair bonded social groups
Strictly arboreal
Hominidae
Arboreal and terrestrial
Larger body size
Varied social organization or social systems
Gorillas are in africa
RIng tailed lemur in madagascar
Orangutans are found in far Southeast Asia in Sumatra and Borneo.
Howler monkeys are found in south america
Different between male and female chimps
Canines
Same between male and female chimps
Molars
Incisors
Brow ridges
Extant nonhuman primates live
South America
Central America
Africa
Asia
Where extant nonhuman primates do not live
Australia
Apes and old world have 2.1.2.3 while platyrrhine and new world have 2.1.3.3
The Y-shaped pattern of the molars is found in apes; catarrhine monkeys have parallel ridges on their molars.
The infraorder Lemuriformes includes lemurs,, which are found only in Madagascar and the Comoro Islands off the coast of Africa.
Catarrhines have a 2.1.2.3 dental formula and are generally larger than platyrrhines. Prehensile tails are only found in platyrrhine species.
Territorial primates use vocalizations to announce their presence.
Territorial species aggressively defend the borders of their territories from outsiders.
Nonterritorial primates have home ranges that overlap with those of neighboring primate groups.
If they mingle together they may interact peacefully, avoid each other, or fight
Primate Extinction Dangers
Hatat loss
Climate change
Bushmeat trade
Why Comparative method is used
The method allows scientists to discern the traits that primates have in common versus the differences that emerge from ecological variation.
The method provides insight into hominin evolution since there is little evidence of behavior in the fossil record.
Female reproductive strategies/ success
lots of parental investment
importance of longevity
importance of social bonds
access to good resources
Male reproductive strategies/ success
competition for access to mates
limited parental involvement
sexual selection
Counterstrategies against infantacide:
Females try to confuse male about paternity
Females try to protect offspring
Intersexual Selection
females choose mates
attractive traits that indicate quality
rare among primates
Intrasexual Selection
male–male competition
larger canines
Drive variation in female reproductive performance
rank
age
longevity
social bonds
Infancticide in baboons and impact on male-female relationships
Females form friendships with one or two adult males.
Male friends can intervene on behalf of their female friend and protect the female's young.
A friendship between a female with offspring and a male does not increase the chances of infanticide.
Intrasexual selection favors traits that increase success in male–male competition.
Sexual selection results in male adaptations that enhance their ability to compete with other males for access to females.
Sexual selection as strong as ordinary selection
Intersexual selection does not favor traits that increase success in female-female competition
Groups that consist of multiple males and one female do not always engage in a cooperative breeding system.
Sometimes one male breeds like in marmoset
False: he male in one-male, multifemale groups has assured, exclusive access to the females.
There may be competition with males outside the group who try to gain access to the females.
Sexual dimorphism arises from intrasexual selection.
Hrdy's hypothesis that infanticide is an evolved reproductive strategy has been subject to criticism. Sommer believes that the criticism is the result of "naturalistic fallacy."
The naturalistic fallacy suggests people believe that if we accept infanticide as "normal" in primate groups, it must also be justified in humans; what is found in nature is "right, just, and inevitable" according to this fallacy.
Why are dominance hierarchies among the females of a primate species formed?
Females flight over access to food resources
Most important factor for female primate reproductive success is her ability to obtain nutrient rich resources
Chapter 7: The Evolution of Cooperation
methods primates use to recognize their kin
vocal cues
smell
patterns of association between individuals
physical similarity
Proximity
Hamilton's Rule
altruists are more likely to interact with each other than chance suggests, then altruistic behaviors could be favored by natural selection.
Altruistic behavior benefits others at a personal cost.
In cooperatively breeding primates:
Sisters sometimes disperse together to form new groups, where one sibling acts as the dominant breeding female and the others help to raise young.
Cooperative breeding takes place more commonly among kin than among unrelated individuals.
The following is not true in cooperatively breeding primates:
Mate competition is greater among related females.
Unrelated females help care for the young of the breeding female in order to prove that they will be a good parent.
In a cooperative breeding scenario, subordinate females are able to produce offspring as readily as dominant females
When monkeys are nervous and anxious, rates of certain self-directed behaviors, such as scratching, increase. Thus, self-directed behaviors are a good behavioral index of stress.
Grooming is an example of altruistic behavior
Natural selection typically does not favor altruistic behaviors
Mutualism is most likely to work when slacking off is not profitable for any of the participants.
rb>c
R:
the average coefficient of relatedness between the actor and the recipients
The coefficient of relatedness, r, measures the genetic relationship between interacting individuals. More precisely, r is the probability that two individuals will acquire the same allele through descent from a common ancestor.
C:
the fitness cost to the individual performing the behavior
The sum of cost to the individual performing the behavior, c, is placed in a ratio of benefit:cost. This ratio scales with the degree of relatedness among individuals.
B:
the sum of the fitness benefits to all individuals affected by the behavior
The sum of benefits to all individuals affected by the act, b, is placed in a ratio of benefit:cost. This ratio scales with the degree of relatedness among individuals.
Consistent with predications derived from Hamiltons rule
Assistance with territorial defense and mate retention is more common among close kin than among distant kin and nonkin.
Cooperative breeding where multiple group members care for dependent young, even those that are not their direct offspring.
Not consistent with predictions derived from Hamilton's rule
Coalitions are more common among distant kin and nonkin than among close kin.
Grooming is more common among distant kin and nonkin than among close kin.
Conditions of reciprocal altruism
Reciprocal altruism can evolve if altruistic behavior is demonstrated between both partners over time.
Individuals only engage in reciprocal altruism with individuals that they come into contact with often.
Reciprocal altruism requires that individuals have some way to keep track of, or respond to, benefits given and support received.
Some organisms are able to recognize their kin by their physical likeness to themselves. This is called phenotypic matching.
Coefficient of relatedness r
half siblings 0.25
Nonkin 0.0
Parent-offspring 0.5
first cousins 0.125 or 0.0625
Female dominance relationships are amazingly stable over time. In many groups, they remain the same over months and sometimes over years. The stability of dominance relationships among females may be a result of the tendency to form alliances in support of kin.
Primates sometimes use the age of other young primates that they associate with to determine whether they are kin.
Chapter 8: The evolution of cognitive complexity and primate life histories
The deterioration of an organism's physical abilities, which occurs as they get older, is called senescence
Compared to most other animals, primates rely more heavily on learning to survive and reproduce successfully.
Primatologists believe that the enlargement and reorganization of the brain in monkeys and apes was linked to the competitive pressures produced by social challenges
Slow maturation and late production
Energy is diverted from current reproduction to maintenance.
Fewer offspring are produced overall.
Growth enhances reproductive success.
Fast maturation and early production:
More offspring are produced overall.
Energy devoted to current reproduction diverts energy from growth and maintenance.
The proportional length of the reproductive life span is increased, and the time between generations is decreased.
Theory of mind refers to the idea that a primates’ ability to predict what others will do in particular situations is based on their knowledge of the mental states of others.
Our brains account for 20% of our metabolic energy.
Our brains account for 2% of our total body weight.
When Seyfarth and Cheney conducted an experiment where female baboons listened to a recording of one female’s grunt followed by another female’s submissive fear barks, they found that female baboons responded more strongly when they heard a higher-ranking female responding submissively to a lower-ranking female’s grunt
All organisms face evolutionary trade-offs, in which one advantageous quality is lost or diminished in favor of gaining another. For example, elephants (and other animals who have single offspring) have traded quantity for quality in reproduction. Smaller litters and longer gestation times mean more care can be provided to offspring.
Natural selection does not select for the ability to avoid aging because aging is a feature of the selection for traits that lead to the greatest reproductive success at young ages at the expense of traits that increase longevity.
The following is true for animals that begin to reproduce early
Animals that begin to reproduce early have high mortality (death) rates.
Animals that begin to reproduce early usually have short life spans.
Animals that begin to reproduce early are usually small bodied.
compared to other organisms, primates tend to have slower, longer life histories and larger brains relative to body size
In order from smallest relative brain size and shortest life history
Strepsirrhines, monkeys, great apes
Haplorrhines live in more complex foraging niches and make use of more complicated and skills-intensive foraging techniques than strepsirrhine primates. Using complex foraging techniques enabled by large brains, haplorrhines to feed on high quality foods that other animals cannot effectively acquire, extract, or process.
The idea that the parts of the brain that are linked to learning and planning expanded in primates because they needed to be able to operate effectively in a complicated social world is called the social brain hypothesis.
The social brain hypothesis holds that a larger brain allows primates to overcome problems linked to competitive pressures produced by living in large groups. Social intelligence (acquired by having a big brain) allows primates to sustain social bonds and keep track of relationships within the group. This is an important part of survival!
Schuppli and her colleagues examined the relationship between primates’ speed of development and their foraging niches, finding that primates with more complex foraging niches grow up more slowly.
short life history
environments with intense predation pressure
long life history
environments with severe competition for access to reproductive resources
The social brain and ecological brain hypotheses are not mutually exclusive. Both may be related to one another.
The social brain hypothesis does not do a good job of explaining group size variation in apes.
Some monkeys have knowledge of the nature of the relationships among other individuals. These are known as third-party relationships.
Selective pressures are much weaker on traits that affect only the old.