BIOL359 Study Guide - Final Guide: Parallel Evolution, Paraphyly, List Of Extreme Points Of Australia
SchoolUniversity of Waterloo
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- Phylogeny: is the study of ancestor descendent relationships
- Phylogenies are based on:
o Morphological data
o Physiological data
o Molecular data
- Characters are used to describe phylogenies
- Any attribute that gives us insight on the history (shared ancestry) of the population
o Ex molecular phylogenies look at nucleotide sequences
- Pleisiomorphy: refers to the ancestral character state
- Apomorphy: a derived character state that differs from the ancestral state
- Synapomorphy: a derived character state that is shared by two or more taxa from a common ancestor
that is not the plesiomorphic ancestor
- Autapomorphy: a independently derived character state
- Monophyletic: a group that contains the common ancestor and all the extant descendants
- Non-Monophyletic: a group that is not monophyletic
o Paraphyletic: includes the common ancestor but not all of the extant descendants
o Polyphyletic: erroneously grouped taxa based on uniquely derived character states that are
- Synapomorphy describe monophyletic groups
- Homology and Homoplasy
o Homology refers to a character state (shared between two or more taxa) derived from a common
o Homoplasy refers to a character state (shared between two or more taxa) which evolved
independently. Example: America vs African Vultures.
- Can be caused by 3 different ways:
1.) Parallel evolution: the independent evolution of the same feature through the same ancestral
condition. Example 3 spine stickle back. Evolved independently, positive assortative mating has
been an important force driving the divergence of these pairs. The large ones look the same and
you wouldn’t think they have a common ancestor but they actually look more like the smaller
ones than they do like the other larger ones.
2.) Convergent evolution: the independent evolution of the same feature through diff ancestral
3.) Secondary loss: reversion to the original ancestral condition
- Analogy is the opposite of homology
o The fins of a whale and the fins of a shark were both formed through convergences (the same
trait derived from different ancestral conditions)
- Reversals can be caused by mutations which remove the synapomorphy
- When constructing phylogenetic trees it is more beneficial to use synapomorphies (monophyletic
character traits) than homoplaseous traits
- Parsimony - The principle of parsimony states that simple explanations are preferred over more complex
ones therefore synapomorphies are preferred over homoplaseous. Camera eye example.
o Less evolutionary steps are preferred over more
o The least number of steps on a tree is the most parsimonious
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- When constructing phylogenetic trees you must determine an outgroup first which is not part of the
group at interest but not too distantly related to it. This is used to polarize the group and act as the
pleasiomorph by which the synapomorph and apomorphs can be distinguished
- Artiodactyla: mammals with even number of toes
- Perissodactlya – odd number of toes
- Bootstrap Method: a computational way to determine the confidence of a phylogenetic hypothesis
- It adds new data on the basis of the info and counts how many times a particular branch is seen on the
- Cladistics: the use of parsimony to construct phylogenetic trees
o Cladistic taxonomy = evolutionary taxonomy
- The use of DNA sequencing is also used when constructing phylogenies: Bayesian analysis and
- Phylogeny and Co-evolution: as one group diverges expect the other group to diverge with it.
- Adaptation: a specific trait that increases the fitness of an individual in comparison to those who do not
possess the trait.
o Example: Oxpeckers. These were birds that were assumed to be taking off the tics on the Ox.
However this was as just so hypothesis. The birds were divided into two groups (Excluded vs.
Not Excluded). Tick Loads: no significance noted between the presence or absence of the
oxpeckers. Wounds: major statistical significance noted. Oxpeckers are not cleaning the
wounds; they are inflicting them on to the ox. Earwax: again major statistical significance noted.
- 3 things to keep in mind
o Differences among populations are not always adaptive
o Not all adaptations are perfect-trade off and constraints
o Not every trait an organism possesses is adaptive
- Experimental Approach:
o Most powerful approaches to test a hypothesis, allows you to isolate a variable and test that
specifically. It allows us to get half the question of causation. It allows us to say that one
variable is the cause to this problem.
o Correlation cannot be used to infer causation – cannot say that one variable is the cause of the
other variable. Can only use correlations to support hypothesis if you predict that two variables
should be correlated based on another factor.
o Example: Jumping Spider responses. Jumping spider-very territorial, threat display by raising
front legs telling other species to get away Jumping spider is the major predator on this type of
fly—prey mimics its predator in order to deter their predator. The wing waving in the fly is
actually mimicking its own predator to deter it form attacking. Tests show that the wings and the
mimicry made spiders retreat. Normal wings/no wings/normal flies got attacked.
- Observational Approach:
o Garter Snakes - cannot regulate their own body temp and make adaptive choices when choosing
the rocks they lay under.
o Experimental observations shown that the snakes will choose to reside under medium sized
- Comparative Studies:
o Evaluates the strength of hypothesis by testing for patterns across species.
o You must know the evolutionary relationships between the species you are studying
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o Must use correlation as support for your hypothesis.
o Example: Bats Sperm Competition—if a male wants to increase his fitness under those
circumstances want to enter more sperm into the race. In order to produce more sperm, they
need to have larger testes. They will attract more females and reproduce more. Researchers saw
that the larger the testes the larger the social group size.
- Lack of data – 2 data points does not provide enough evidence. 6 different species tested. Positive slope
line generated from that which indicates a correlation between the two. Phylogeny of species – show that
A B and C might have inherited their small testis size from their common ancestor but the others might
have a common ancestor that had large testis. We rather actually have two data points indicating the
common ancestor. It deflates the data rather considerably.
- Use of phylogenies to develop independent contrast between species. Be aware that the method exists –
not to be tested just know the general basics. We still get a nice positive upward sloping line which tells
us that the correlation actually exists.
- Factors that affect evolutionary adaptation
o Trade-offs: a compromise between one trait and another, which cannot be avoided. Ex. flower
size in a Begonia
o Constraint: any factor that slows down or hinders the process of evolutionary adaptation in a
Developmental/functional constraint: due to physiological constraint. Ex. Flower color
change in Fuschia.
Genetic constraint: lack the genetic variability to adapt. Ex. Beetles.
Ecological constraint: environment prevents adaptation. Ex. Dove lice host shifts.
- Phenotypic Plasticity: is the same genotype which yields a different phenotype due to environmental
conditions – may be caused by adaptations
Our Closest Relatives:
- On the phylogenetic tree humans are listed as part of the hominadae along with chimps, gorilla,
orangutans and bonobos.
- Humans did NOT evolve from chimps; they both rose from the same common ancestor; however
humans were the first lineage to separate.
- The Genus Pan distribution: show non overlapping distribution
- Bonobo’s VS Common Chimp
o Squarish snout; more robust bodies than bonobos
o Aggressive and male dominant – the largest male is the dominant
o Eat meat and other monkeys
o Used tools and weapons for hunting and attacking
o In fight for territory they will break out into war
o Both are intelligent and can identify them selves in mirror
o Both have a fission fusion community by which they will exchange individuals randomly
o Roundish snout
o More peaceful, eat sugar cane, do not display war
o They use sex as a method of conflict resolution
o Females are dominant – egalitarian society
o The status of a male depends on the status of its mother
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