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EVOLUTION (Key events in life history (Mesozoic era (flowering plants…
EVOLUTION
Key events in life history
Cenozioc era
this was like 56 million years ago
ice ages, origin of species Homo
origin of primates group
Mesozoic era
flowering plants appear and diversify
gymnosperms continue as dorminant plants
cone-bearing plants dorminate landscape
this was like 250 million year ago
palezoic era
origin of reptiles
this was like 500 million years ago
diversification of bony fishes, first tetrapods and insect appear
diversification of early vascular plants
Archaean era
this was like 3500 million years ago
concerntaration of atmospheric oxygen begins to increase
oldest fossils of prokryotic cells appear
Hadean era
this was like 4500 million years ago
origin of earth
neo-proterozoic era
diverse algae and soft-body invetebrate animals appear
this was like 1800 million years ago
oldest fossils of eukaryotic cells appear
Conditions of early earth
Abiotic synthesis of small organic molecules eg amino acids and nitrogeneous bases
the joining of the small molecules into macromolecules such as proteins and nuclei acids
packing of these molecules into protocells, droplets with membranes that maintain an internal chemistry different from that of the surrounding
the origin of self-replicating molecules that eventually made inheritance possible.
Fossils
fossil record documents the history of life
its shows grea changes in the kind of organism on earth at different points in time
many were destroyed by later geologic processes, and only a fraction has been dicovered.
contain isotopes of elements that accumulated in the organism when they were alive
the age of a fossil can be determine by radiometric dating.
Phylogeny and tree of life
impotance of genome and molecular clock
some genes can diverge and potentially take on new functions
distantly related species often have many orthologous genes .the small variation in gene number in organism varying complexity suggest that genes are versatile and may have many fuctions
molecular clock help track evolutionary time
molecular clock analyses suggest thatthe most common strain of HIV jumped from primates to human in early 1900s
Phylogenies are infered
from morphological and molecular data
organism with similar morphologies or DNA sequence are likely to be more closely related
organism with diiferent strutures and DNA sequence are not likely close related
to infer phylogeny, homology must be distinguished from analogy
computer programs are used to align comparable DNA sequences and to distinguish molecular homologies from coincidental matches between taxa that diverged long ago
constructing phylogenic trees
shared characters are used
clade is a monophyletic group of that includes an ancestral species and all of its descendants
among phylogenies, the most parsimonious tree is the one that requires the fewest evolutionary changes
the most likely tree is one based on the most like pattern of changes
well-supported phylogenetic hypothese are consistent with a wide range of data