I. Classification and phylogenies
A. Aristotle and the chain of being
Aristotle, 384322 B.C.
believed beings are fixed entities
beings ranked along continuum
ranking called “scala naturae” or Great Chain of Being
In Great Chain of Being, beings arranged in order of increasing “perfection”
B. Linnaeus and the hierarchical classification system
Carolus Linnaeus, 17071778 (Father of Taxonomy)
Taxonomy: theory of practice of classifying organisms
Created binomial nomenclature
Hierarchical classification: classification based on similarities and differences “groups within groups, within groups, within groups” If you want to learn more check out What is the fine tuning argument?
C. Phylogenetic trees
describes that history, and shows evolutionary relationships near and distant relatives
Phylogeny the evolutionary history of organisms
Node: common ancestor at a time of split
each node represents a speciation event
Branch: a lineage through time
Clade: common ancestor and all of its descendents
II. Evolution by natural selection
A. Darwin 18091882
created natural selection
collections and noted from his trips and breeding new varieties of pigeons and other species helped Darwin develop his theory of natural selection Traits evolve through natural selection
ex: Loggerhead shrikes prey on lizards, using keen vision
B. Example: selection for crypsis
- matching body coloration to habitat evolved under natural selection to reduce predation
C. Requirements for selection
- Individuals in a population vary in some trait
at least some variation is genetically based (heritable)
certain genotypes produce more surviving offspring than others differences in survival among genotypes are due to an agent of selection Don't forget about the age old question of What is a sports pyramid?
I. Mechanisms of evolution
A. Examples of natural selection
Pepper moth moth rests on tree branches, matches lichen covered bark
B. Genetic drift
- Genetic drift can cause significant evolutionary change, but genetic drift does NOT make organisms adapted to their environment
C. Gene flow
- Can counter local effects of natural selection
Ex: a 2nd lizard species has white morph in white sand dunes. But brown genotypes disperse frequently from scrub into white dunes
usually involves change in DNA sequence
“Point” mutation is one nucleotide change We also discuss several other topics like What are the functions of the skin?
Rarely generate novel traits
usually change preexisting traits
evolution a change in allele frequency over time in a population of organisms We also discuss several other topics like What are the energy principles in the atmosphere?
population a group of potentially interbreeding individuals of the same species. Ex: All E. coli bacteria in your stomach Don't forget about the age old question of What is globalization in ancient times?
allele a form of a gene
allele frequency proportion of that allele in a particular population
genetic drift random changes in allele frequency from one generation to the next
gene flow transfer alleles from one population to another (usually involves movement of individuals)
mutation alteration of a gene that gives rise to a new allele
A. How do new species form?
- They diverge from existing species by isolation, separation, genetic divergence, and reproductive isolation
B. How does separation occur?
- One population breaks into 2+ separate groups
Allopatric speciation (a physical barrier separating them)
Sympatric speciation (no physical barrier, stops
interbreeding for another reason) Don't forget about the age old question of Evolution by natural selection is driven by how many principles?
Species a group of individuals capable of interbreeding, and reproductively isolated from other groups.
Allopatric a physical barrier arises that prevents interbreeding
Sympatric No physical barrier arises; interbreeding between groups stops for another reason.
Polyploidy multiplication of chromosome number (hove multiple sets of chromosomes)
Allopolyploidy Combination of parents’ chromosome # in offspring, when 2 species successfully mate.
Diploid has 2 sets of chromosomes usually from the mother and father Zygote cell formed by the fertilization of the sperm and egg
I. Prokaryotes – Bacteria and Archaea
- 3 Domains: Bacteria, Archaea, and Eukarya
The Archaea and Bacteria are both prokaryotic, but differ more from each other than does the Archaea from the Eukarya.
Archaea are the sister group to Eukarya
Eukarya involve prokaryotes
- Prokaryotic cells are usually much smaller than eukaryotic cells Prokaryotes everything in one compartment, including DNA
Eukaryotes have a flexible membrane which allows sophisticated cytoskeleton.
Prokaryotes reproduce asexually by fission
Transfer of DNA by a cytoplasmic bridge
Some anaerobic and some aerobic
Use light for energy and CO2 for carbon
A. How are they defined?
Protists are defined by what they are not: Eukaryotes, but not animals, plants or fungi. Most are unicellular, but some algae are multicellular
Not a monophyletic group
Evolution of the animal body plan
I. What defines an animal?
Heterotrophic life style
Move under their own power sometime in their life cycle
All but sponges have neurons (that transmit electrical signals to other cells) and muscle cells that can change the shape of the body by contracting
II. Introduction to evolution of animal body plan
A. Animals with cellular organization Sponges (Porifera) - Tube organization
Cells in ECM – like fruit in jelly
Cells that move water and absorb food
“choanocytes” – funnel cells
B. Evolution of symmetry
-Asymmetrical A plane through the center in any direction will bisect the organism in equal halves
Radial only a single plane will bisect the organism into equal halves
Bilateral one single plane will bisect the organism into 2 equal halves
C. Evolution of extracellular digestion, and a oneway digestive system.
ED the size of food they can consume can be bigger than a single cell
food goes out their mouth because no anus
One way mouth and anus are the same
D. Evolution of body cavity coelom
- a body cavity, not the same as a gut
In humans divided into two thoracic and abdominal cavities