Mader: Biology 8 th Ed. Origin and History of Life Chapter 19.

Mader: Biology 8th Ed.

Origin and History of Life

Chapter 19


Outline

• Primitive Earth• Origin of First Cells• Fossils• The Precambrian• The Paleozoic• The Mesozoic• The Cenozoic• Continental Drift• Mass Extinctions


The Primitive Earth

• Primitive atmosphere most likely consisted of water vapor, nitrogen, and carbon dioxide, with small amounts of hydrogen and carbon monoxide.– Little free oxygen.– Originally too hot for anything but water

vapor to form.– Earth cooled and water vapor condensed

to liquid water.


Monomers Evolve

• Stanley Miller (1953) conducted an experiment to show the first organic molecules could have been produced from primitive atmospheric gases in the presence of strong energy sources.


Polymers Evolve

• Monomers join to form polymers in the presence of enzymes.– Protein-First Hypothesis assumes DNA

genes came after protein enzymes arose.– RNA-First Hypothesis suggests only RNA

was needed to progress toward formation of the first cell or cells.


Protocell Evolves

• Protocells would have been precursors to the first true cells.– A protocell is a structure with a lipid-

protein membrane that carries on energy metabolism.

Semipermeable-type boundary may form around coacervate droplets.

Liposomes form in liquid environments.


Protocell Anatomy


Origin of First Cells


Fossils

• Fossils are remains and traces of past life.– Great majority are found embedded in, or

recently eroded from, sedimentary rock.Sediment becomes a stratum.

Recognizable layer in stratigraphic sequence.

Paleontology is the study of the fossil record.


Fossils


Relative Dating of Fossils

• Strata change their character over great distances.– A stratum of the same age tends to

contain the same fossil.Helps geologists determine relative

dates of the strata despite upheavals.


Strata


Absolute Dating of Fossils

• One absolute dating method relies on radioactive dating techniques.– All radioactive isotopes have a particular

half-life.Length of time it takes for half of the

radioactive isotope to change into another stable element.

Compare radioactivity of a fossil to that of a modern sample of organic matter.


The Precambrian

• Comprises about 87% of the geological timescale.– First cells came into existence.

Prokaryotes Cyanobacteria in ancient

stromatolites added oxygen to the atmosphere.

Lack of ozone shield allowed UV radiation to bombard Earth.


Prokaryote Fossil of Precambrian


The Precambrian

• Eukaryotic Cells Arise– Eukaryotic cell arose about 2 bya.

Nearly always aerobic and contains nucleus as well as other membranous organelles.

Endosymbiotic Hypothesis.• Multicellularity Arises

– Multicellularity arose approximately 1 billion years later (1.4 bya).


The Paleozoic

• The Paleozoic era lasted over 300 million years.– Contained three major mass extinctions.

Disappearance of a large number of species, or a higher taxonomic group, within a relatively small time interval.


Cambrian Animals

• Molecular Clock is based on principle that DNA differences in certain parts of the genome occur at fixed rate, and are not tied to natural selection.– Number of base-pair differences tells how

long two species have been evolving separately.

High Cambrian diversity may be due to the evolution of outer skeletons.


Cambrian Sea Life


Invasion of Land

• Plants– Seedless vascular plants date back to

Silurian period and later flourished in Carboniferous period.

• Invertebrates– Outer skeleton and jointed appendages of

arthropods are adaptive to living on land.• Vertebrates

– Evolution of fishes began in Ordovician.


The Mesozoic Era

• Evolution of many plants and animals continued into the Triassic, the first period of the Mesozoic era.– Nonflowering seed plants became

dominant.– Dinosaurs achieved enormous size.– Mammals remained small and

insignificant.


The Cenozoic Era

• Mammals began an adaptive radiation at the end of the Mesozoic era, moving into habitats left vacant by the demise of dinosaurs.– Flowering plants already diverse and

plentiful.– Primate evolution began.


Factors That Influence Evolution

• Continental Drift– Positions of continents and oceans are

not fixed.Modern mammalian biological diversity

is the result of isolated evolution on separate continents.


Continental Drift


Continental Drift

• Plate Tectonics– Movements of Earth’s crust which is

fragmented into slablike plates that float on a lower hot mantle layer.


Plate Tectonics


Mass Extinctions

• At least five mass extinctions have occurred throughout history. At the ends of:– Ordovician

Continental Drift– Devonian

Bolide EventLoss of 70% of marine invertebrates


Mass Extinctions

– PermianExcess carbon dioxide.Loss of 90% of ocean species.

– TriassicMeteorite Collision

– Cretaceous


Review

• Primitive Earth• Origin of First Cells• Fossils• The Precambrian• The Paleozoic• The Mesozoic• The Cenozoic• Continental Drift• Mass Extinctions

Mader: Biology 8 th Ed. Origin and History of Life Chapter 19.

Documents

Transcript of Mader: Biology 8 th Ed. Origin and History of Life Chapter 19.