Definitions of Biological Disciplines evolution—change through time biodiversity—variety of living forms & their habits anatomy & physiology—structure & function behavior—how animals do things ecology—interactions of animals w/ each other & their physical environments

Perpetual Change & Geological Time Perpetual geological & biological change is the rule. Consider the vastness of geological time. radiometric dating age of Earth—4.6 billion years

Evidence of Perpetual Change Banded Iron Formation, Australia rocks up to 3 billion years old

Evidence of Perpetual Change Big Island, Hawaii oldest part of island 400,000 years old (7,500 times younger than the old rocks)

Fossil Record oldest microscopic fossils—3.5 billion years oldest macroscopic fossils—650 million years most animal phyla present 540 million years ago

Fossil Record Burgess Shale (580 million years old [Cambrian]) many phyla present that are long extinct some modern phyla represented an “experiment of evolution”

Fossil Record oldest vertebrates >500 million years old human agriculture ~10,000 years old Therefore, human agriculture is about 0.00002% (two one-hundred thousandths of one per cent) as old as the oldest vertebrates 0.00002% of a mile = 1/3 of a millimeter

Darwin and Evolution Charles Darwin served as naturalist on mapping expedition around coastal South America. Used many observations to develop his ideas Proposed that evolution occurs by natural selection

Influences on Darwin voyage of the H.M.S. Beagle Darwin 23 years old 5-year voyage around the world

Influences on Darwin observed & collected fauna & flora found fossils found seashells in mountains at 4,000 meters experienced major earthquake in S. America

Influences on Darwin Beagle stopped at the Galapagos Islands (on equator 600 miles off of W coast of S. America) spent 5 weeks on islands

Influences on Darwin Galapagos visit hugely influential on Darwin’s development of theory of evolution organisms unique, yet similar to continental forms in S. America (e.g., giant tortoises due to lack of predators)

Charles Darwin Evolution: Modification of a species over generations “descent with modification” Proposed that evolution occurs by natural selection Natural Selection: Individuals with superior physical or behavioral characteristics are more likely to survive and reproduce than those without such characteristics

Natural Selection proposed by Darwin (and Wallace) supported by abundant evidence describes how populations accrue ‘favorable’ characteristics over evolutionary time evidence from artificial selection e.g., dog breeds supported by series of observations & inferences from those observations

Darwin’s Evidence Similarity of related species Darwin noticed variations in related species living in different locations

Darwin’s Evidence Population growth vs. availability of resources Darwin realized that not all members of a population survive and reproduce Deduced that the organisms best adapted to obtaining resources would survive to reproduce

Post-Darwin Evolution Evidence Comparative anatomy - Homologous structures have same evolutionary origin, but different structure and function. - Analogous structures have similar structure and function, but different evolutionary origin.

Common Descent all forms of life ultimately descended from a common ancestor via a branching of lineages single origin of life

Common Descent: Phylogeny structure of life is like a tree—phylogeny common ancestor of ratite birds

Common Descent: Homology homologous structures reflect common evolutionary ancestry e.g., limb skeleton of tetrapods from salamanders to humans share homologous elements

Homologous Structures

Common Descent: Homology Whether or not two structures are homologous depends on the “level” being considered. E.g., bird wing & bat wing grossly homologous modified forelimb but specific elements supporting the airfoil of each are not homologous feathers in bird vs. skin in bat

Analogy similar structures that serve similar function but do not indicate common ancestry e.g., bird wing vs. butterfly wing

What is a species? Biological Species Concept (Mayr 1940) an interbreeding natural population (or group of populations) that is reproductively isolated from other such groups Evolutionary Species Concept (Simpson [1961] & Wiley [1981]) a single lineage of ancestral-descendant populations that maintains its identity from other such lineages & that has its own evolutionary tendencies & historical fate at least 30 other published species concepts

How does speciation occur? evolution of reproductive barriers can be physical, physiological, ecological, behavioral, etc. (frequently a combination) generally accepted that the evolution of reproductive barriers b/t populations of animals requires the presence of geographic barriers (e.g., mountain range, isolated island) that physically separate populations

How does speciation occur? allopatric speciation population separated into two separate groups by geographic barrier followed by evolution of reproductive barriers examples of geographic isolating mechanisms formation of new mountain range separating population of low elevation species formation of new island (e.g., land in ocean, lake on land) followed by rare immigration of individuals

How does speciation occur? examples of allopatric speciation marine iguana & land iguana on Galapagos reptiles on islands in Sea of Cortez Hawaiian crow squirrels on N & S rim of Grand Canyon other speciation mechanisms exist, but allopatric speciation is most pervasive

Gradualism major differences in traits among species evolve by accumulation of many small incremental changes over time somewhat controversial phyletic gradualism

Alternative to Gradualism: Punctuated Equilibrium sudden appearance of new species & rapid morphological changes followed by long periods of stasis some patterns show gradualism & others indicate punctuated equilibrium reality likely combination of both punctuated equilibrium

What Evolution Is & Is Not Evolution is not like a ladder. Evolution is like a tree. The parts of an organism (i.e., its characteristics) can be ancestral or derived, depending on what other organisms it is being compared to. An organism is the sum of its parts. Therefore, an organism is a composite of ancestral & derived characteristics. Avoid using the terms primitive & advanced in reference to organisms or taxonomic groups.