CHAPTER 18 Flashcards
(31 cards)
Four Eras of Time
Precambrian, Paleozoic, Mesozoic, Cenozoic
The principle of common ancestry
States that all life on earth can be traced back to a single ancestor
Fossil
The remains or traces of past life usually preserved in sedimentary rock
Parts of the geological timescale
Eras, Periods, Epochs
Geological timescale
Divides the history of the earth into eras, periods, and epochs.
Stromatolites
Boulders from the Precambrian era
How much of the geological timescale does the Precambrian era contain?
87%
3.8 BYA
First chemical fingerprints of complex cells occur
3.46 BYA
Photosynthetic prokaryotic cells appear
What did early bacteria resemble?
The Arcae that live in Hot Springs today
What did early stromatolites resemble?
Living stromatolites with cyanobacteria on the outer surface
2 BYA
Oxygen levels were high enough that Anaerobic prokaryotes where declining.
Excessive oxygen gas caused…
Extinction of anaerobic organisms and the rise of aerobic organisms.
Oxygen gas forms the ozone shield (O3) in the upper atmosphere contributing to…
The blocking of ultraviolet radiation from reaching the earth surface allowing organisms to live on land
Eukaryotic Cells
Arose 2.1 BYA
Aerobic
Contains a nucleus and organelles
Endosymbiotic theory
States that a nucleated cell probably engulfed prokaryotes which then became organelles
Mitochondria were probably free living aerobic prokaryotes
Chloroplasts were probably free living photosynthetic prokaryotes
Cilia and flagella may have originated from slender undulating prokaryotes that attached to host cells.
Support for the Endosymbiotic theory
Mitochondria and chloroplasts have a similar size of that of bacteria.
Mitochondria and chloroplasts have their own DNA and make some of their own proteins.
Mitochondria and chloroplasts divide by binary fission similar to bacteria
Their outer membranes differ:
The outer - eukaryotic, the inner - prokaryotic
Multicellularity Arises
Not known exactly what multicellular organisms appeared. (approximately 1.4 BYA)
They were initially microscopic
The separation of germ cells from somatic cells may have helped with the diversity of organisms
Early multicellular organisms lacked internal organs and could have absorbed nutrients from the sea
Stages to become a protist
Unicellular colony specialization gametes protist
The Paleozoic era
Known as the Cambrian explosion
Lasted over 300 million years
Had three major mass extinctions (ex. Trilobites)
Cambrian animals
The Cambrian period saw invertebrates flourish
Cambrian sea floors were dominated by trilobites that had armored exoskeletons
Invasion of land
Life first begin to move out of the ocean around 500 million years ago in the Paleozoic era
Spiders centipedes and millipedes all came before the appearance of insects on land
The vertebrate line of descent began in the early Ordovician period.
The Devonian period is called the age of fish.
The Carboniferous was an age of coal forming forests.
Amphibian diversification
Early vascular plants and amphibians were larger and more abundant during the Carboniferous period.
The climate change to colder and drier begin the process that produced coal.
Mesozoic era (The Triassic Period)
Reptiles and went adaptive radiation
One group of reptiles, the therapsids, had mammalian traits.
