Notes – Chapter 25 Phylogeny and Systematics
•_______________________________________– evolutionary history of a
species or group of related species
•_______________________________________ – study of biological
diversity in an environmental context (tracing phylogeny)
•_______________________________________ - science of naming,
identifying, and describing diverse forms of life
•_______________________________________ – supercontinent of land
masses (present 250 mya)
Geologic Time Scale
•Major Events in Evolution
♦4.6 bya – formation of the __________________________ (Precambrian)
♦3.5 bya – prokaryotic cells
♦2.2 bya – eukaryotic cells
♦600 mya – soft-bodied ______________________________
♦500 mya – colonization of land plants (Paleozoic)
♦420 mya – jawless fish
♦375 mya – bony fish, amphibians, insects
♦325 mya – first seed plants, reptiles
♦220 mya – cone-bearing plants (Mesozoic)
♦175 mya – ____________________________________ abundant
♦80 mya – angiosperms
♦60 mya – mammals, birds, pollinating insects (Cenozoic)
♦30 mya – primate groups
♦2.5 mya – apelike ancestors
♦0.5 mya – _____________________________________ appear
Radiometric Dating
•The measurement of certain radioactive
___________________________________
in fossils or rocks.
•____________________________________
___ – the number of years it takes for
____________% of the original sample to
decay; it is unaffected by temperature,
pressure, and other environmental variables
•Carbon-14 to Nitrogen-14 → 5,730 years
•Potassium-40 to Argon-40 → 1.3 billion years
•Uranium-238 to Lead-206 → 4.5 billion years
–Found in Volcanic Rock
The Fossil Record
•The fossil record is far from being complete, it is slanted in favor of species
that existed for a long time, were abundant and widespread, and had shells or
hard skeletons.
•A substantial fraction of species that have lived probably left no fossils,
most fossils that formed have been destroyed, and only a fraction of the
existing
fossils have been discovered.
Major Mass Extinctions
•__________________________________ Period – 250 mya
•________% of marine animal went extinct
•8 out of 27 orders of Permian insects did not survive
•The extinction occurred in less than 5 million years
•Reasons
•Occurred about the same time the continents merged to form
____________________________ – Marine and terrestrial habitats
disturbed
•Massive volcanic eruptions in what is now Siberia – increase in
atmospheric carbon dioxide =
____________________________________
•Global warming = reduced temp. differences between the poles and
equator. Could lead to uneven mixing of the oceans which decrease
amount of dissolved oxygen
Major Mass Extinctions
•__________________________________ Period – 65 mya
•Extinction of dinosaurs
•Killed more than half of the marine species
•Exterminated many families of terrestrial plants and animals
•Reasons
•The climate became cooler, and shallow seas receded from
continental lowlands
•Large volcanic eruption in what is now India
•“____________________________________ Hypothesis” – a large
comet (dirt and ice) or small asteroid (rock and metal) collided with
Earth
Taxonomy
•_____________________________– Binomial;
based on a 2-part Latin name; genus and species.
•Ex. Pseudacris nigrita, Homo sapiens
•Hierarchical Classification – way for us to
structure and view of our world
Phylogenetic Systematics
•Phylogenetic
____________________– reflect the
hierarchical classification of
taxonomic groups
•______________________________
___ – a “tree” constructed from a
series of dichotomies, or 2-way branch
points that represent divergence of an
animal from a common ancestor; the
“deeper” the branch to greater the
divergence
•The sequence symbolizes historical
chronology
•_______________________________ – each branch in a cladogram;
ancestral species and all of its decendents
How Do We Construct a Cladogram?
•_________________________________ – likeness attributed to shared
ancestry; all forelimbs of mammals are homologous
•Not all likeness qualifies as homology
•________________________________ Evolution – Species from different
evolutionary branches may come to resemble one another if they have
similar ecologocial roles and natural selection has shaped analogous
adaptation. Similarity due to convergence is called analogy.
•Example – the wings of a bird, bat, and bee.
•As a general rule – the greater the number of homologous parts between
two species, the more closely the species are related.
•The more complex two similar structures are, the less likely it is they
evolved independently
–Example – the human skull and chimpanzee skull match almost
perfectly bone for bone, the only difference is the way they fuse
together. Most likely, the genes required to build these skulls were
inherited from a common ancestor.
Phylogeny Can Be Inferred From Molecular Data
•Anatomical characteristics and homology alone cannot account for all
evolutionary relationships
•Systematists compare genes (____________) and gene products
(_______________________) to determine evolutionary relationships