Intraspecific variation Variation accounted for by individual, age, and sex differences seen within...
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Transcript of Intraspecific variation Variation accounted for by individual, age, and sex differences seen within...
Intraspecific variation
• Variation accounted for by individual, age, and sex differences seen within every biological species
Fossil Genera and the evolution of homo
• A genus is a group of species composed of members more closely related to each other than to species from any other genus. • Ex: dogs belong to the Canidae genus that
includes wolves, jackals, coyotes and foxes• We (and all the other extinct “Homo”s ie
Hohabilis, Homo erectus) belong to the Genus Homo
• Species that are members of the same genus share the same broad adaptive zone.
• Members of the same genus should all share derived characters not seen in members of other genera.
Ancestral and Derived (Modified) Characters
• Derived (Modified) Characters that are modified from the ancestral condition and thus are diagnostic of particular evolutionary lineages.
•Ancestral•Characters inherited by a group of organisms from a remote ancestor
Generalized and Specialized Characteristics
• Refer to the adaptive potential of a particular trait
• Generalized if a trait is adapted for many functions: a mammalian limb with five fairly flexible digits, adapted for many possible functions
• Specialized if a trait is limited to a narrow set of functions: hand or foot suited for specialized function of stable weight support in an upright posture
Principles of Classification
• The field that establishes the rules of classification is taxonomy.
• Organisms are classified first on the basis of physical similarities.
• Basic physical similarities must reflect evolutionary descent in order for them to be useful.
Principles of Classification• Homologies • Similarities based on a
common ancestor.• Analogies• Superficial similarities
that are a product of separate evolutionary responses to roughly similar functional demands.
• Homoplasy• The process that leads to
Analogies.
Constructing Classifications and Interpreting Evolutionary Relationships
• Evolutionary systematics• A traditional approach in which presumed ancestors
and descendants are traced in time by analysis of homologous characters.
• Cladistics • Attempts to make rigorous evolutionary interpretations
based solely on analysis of certain types of homologous characters (those considered to be derived characters).
Cladogram• A chart showing
evolutionary relationships as determined by cladistic analysis.
• It’s based solely on interpretation of shared derived characters.
• It contains no time component and does not imply ancestor-descendant relationships.
Birds?
Shared Derived• Relating to specific character traits shared in common between two
life-forms and considered the most useful for making evolutionary interpretations.
• The presence of feathers in the proposed relationship between some (theropod) dinosaurs and birds is an example
Archaeopteryx Late Jurssaic Period ~150mya
Clade -- car example
• From a common ancestor of all passenger vehicles, the first major divergence is between cars and trucks (I).
• A later divergence occurs between luxury cars and sports cars (II).
• Derived features of each grouping appear after its divergence from other groups.
Clade – car example
• In this “tree,” SUVs diverge from trucks, but like sports cars, have a decorative racing stripe.
• This is a homoplasy and does not make SUVs sports cars.
• Classifications based on one characteristic that can appear in different groups can lead to an incorrect conclusion.
Evolutionary systematics
• Traditional approach to interpreting evolutionary relationships with the goal of producing classifications.
Phylogenetic Tree
• A chart showing evolutionary relationships as determined by evolutionary systematics.
• It contains a time component and implies ancestor descendant relationships.
Tempos and Modes of Evolutionary Change
• Macroevolution is the change from one species to another• Macroevolution is only partly understandable through
microevolutionary models.• There are TWO main theories regarding Macroevolution…
Missing link? -- The Theory of Gradualism
• Gradualism refers to change accumulating gradually in evolving lineages, or a series of forms with finely graded transitional differences between ancestor and descendant, with “missing links” present
Punctuated Equilibrium• Punctuated equilibrium refers to no missing links, with real gaps representing
uneven, nongradual process of long stasis and quick spurts• These “quick spurts” still take A LOT of time, some 10,000-50,000 years.
Evolution…classified
• Organizes diversity into categories and, at the same time, indicates evolutionary relationships.
• The kingdom Animalia includes 20 major phyla (singular, phylum)
• Chordata is one phyla and includes all animals with a nerve cord, gill slits and supporting cord along the back.
Mammalian Evolution• The Cenozoic era, the Age of
Mammals.• ADAPTIVE RADIATION
• A process that takes place when a life form rapidly takes advantage of the many newly available ecological niches.
• A species, or group of species, will diverge into as many variations as two factors allow:
1. Its adaptive potential.2. The adaptive
opportunities of the available niches
Mammalian Evolution• Characteristics:• The enlargement of the cerebrum, especially the
neocortex, which controls higher brain functions, resulting in more nerve cells\
Mammalian Evolution
• Characteristics:• A longer, more intense period of growth in utero
MarsupialsMarsupials
MonotremesMonotremes
Placental MammalsPlacental Mammals
Mammalian Evolution• Characteristics:• Distinctive
dentition, termed a heterodont dentition, with 3 incisors, 1 canine, 4 premolars, and 3 molars in each quarter of mouth
Mammalian Evolution• Characteristics:
• Maintenance of constant internal body temperature, warm-bloodedness, and ENDOTHERMIC
Ectothermic