ANT203H5 Chapter Notes - Chapter 4: Prosimian, Evolutionary Taxonomy, Hyoid Bone
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Biological species concept - organisms from different populations are considered to be in the
same species if they naturally interbreed and produce fertile offspring.
Anagenesis: The transformation of a single species over time.
Chronospecies: Labels given to different points in the evolutionary lineage of a single species
over time. As a species changes over time, the different stages are labeled as chronospecies in
recognition of the biological changes that have taken place.
Cladogenesis: The formation of one or more new species from another over time.
- The origin of a new species.
-The genetic isolation of populations that may render them incapable of producing fertile
- elimination or reduction of gene flow between populations
-Geographic isolation most common, behavioural isolation (feeding habits, awake during diff
-once gene flow has ceases other evolutionary forces will cause the species to diverge
-natural selection once thought to be the sole reason for speciation
Adaptive radiation: The formation of many new species following the avail-ability of new
environments or the development of a new adaptation.
Modes of Macroevolution
-A model of macroevolutionary change whereby changes occur at a slow, steady rate over time.
-natural selection slowly operating on some initial mutation
-Fossils will show a smooth transition
-A model of macroevolutionary change in which long periods of little evolutionary change
(stasis) are followed by relatively short periods of rapid evolutionary change.
- speciation will occur within small, isolated populations
- When the environment changes too rapidly or when the appropriate genetic variations do not
exist, a species can become extinct.
- Orthogenesis: A discredited idea that evolution will continue in a given direction because of
some vaguely defined “force.”
-bigger or newer isn’t better, natural selection doesn’t always work, no set direction in evolution
-Doesn’t provide perfect structures, not all structures from adaptions (ex: appendix)
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-current structures not always used for current functions (Natural selection operates on the
variation that is present. Structures are frequently modified for different uses)
Classification of species
Homology: Similarity due to descent from a common ancestor
Homoplasy: Similarity due to independent evolution
Parallel evolution: Independent evolution of traits in closely related species.
Convergent evolution: Independent evolution of similar traits in rather distinct evolutionary
Primitive trait: A trait that has not changed from an ancestral state.
Derived trait: A trait that has changed from an ancestral state.
-Comparing traits, are they shared or unique (EX: no tail is a shared derived trait in humans and
apes, walking upright is a unique derived trait)
Approaches to classification
Evolutionary systematics: A school of thought that stresses the overall similarity of all
(primitive and derived) homologous traits in classification.
Cladistics: A school of thought that stresses evolutionary relationships between organisms
based on shared derived traits.
Outgroup: a group used for comparison in cladistic analyses to determine whether the
ancestral state of a trait is primitive or derived
“The Sixth Finger” – an episode which the plot is centered around the idea that there is a goal to
evolution and you can travel backwards and forwards along the evolutionary line.
Primates: The order of mammals that has a complex of characteristics related to an initial
adaptation to life in the trees.
Chordata: A vertebrate phylum consisting of organisms that possess a notochord at some
period during their life.
Notochord: A flexible internal rod that runs along the back of an animal (in gestation)
Vertebrata: A subphylum of the phylum Chordata, defined by the presenceof an internal,
segmented spinal column and bilateral symmetry.
Bilateral symmetry: Symmetry in which the right and left sides of the body are approximately
Characteristics of Mammals
-Placenta mammals: live birth; High survival chance, high energy cost
-Immature baby (kangaroos)
-More pre and postnatal care (few offspring)
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