LECTURE 3 Flashcards
what is taxonomy?
artificial classification of organisms
solely based on visible similarities
still used to name organisms
what is phylogeny?
natural classification of organisms
reflects the evolutionary relatedness between organisms
how were organisms grouped before the concept of evolution? and how did that change
grouped based on morphological similarities (taxonomy), no relationships between the groups
fossils of animals and plants were found and used to suggest the appearance of the groups to build evolutionary family trees
why were microorganisms left out until the late 1960s?
left out because there are no microbial fossils
they all have very similar shapes even if they are different with evolution
how can a phylogenetic tree be made for microorganisms?
by comparing ubiquitous gene sequences (genes present in all organisms) to include microorganisms and create a tree of life
what are traditional early classification schemes vs haeckel’s proposal?
traditional early=plants and animals
haeckel=plants, animals, and microorganisms
what does haeckel’s tree of life look like?
common source of life
division in three groups: plantae, protista, animalis
the groups do not interact with each other
what classification scheme did edouard chatton propose?
eucaryotes and procaryotes
what scheme did robert whittaker propose?
the 5 kingdom scheme
monera, protista, fungi, plantae, animalia
(completely wrong)
what did carl woese do?
proposed the 3 kingdom scheme
used a molecular approach by comparing the stable and ubiquitous 16S ribosomal RNA gene
3 kingdoms: bacteria, archaea, eucaryotes
these three groups are equally distant
how do you build a phylogenetic tree?
get the sequence of a ubiquitous gene (16S ribosomal RNA gene, 1600 nucleotides)
align the gene sequences using a sequence alignment program
feed the sequences to a phylogenetic algorithm
find which sequences have the highest homology
create the tree
the length of the branch is proportional to the evolutionary distance
what evidence supports the endosymbiotic theory?
what is the endosymbiotic theory of evolution?
a primitive eukaryotic cell engulfed an ancient prokaryote to create the first eukaryotic cell
the two cells continued to evolve in a mutually beneficial symbiotic relationship
prokaryotic cell benefitted from being in a sheltered environment rich in nutrients
the eukaryotic cell received ATP by respiration or by photosynthesis
when did the first prokaryotes and eukaryotes appear?
first prokaryote: 3.5 billion years ago
first eukaryote: 1 billion years ago
what microorganism do mitochondria descend from?
gram negative alpha proteobacterium which is an obligate intracellular parasite (cannot live on its own)
