chapter 9:The History of Life on Earth

Earth’s early atmosphere likely contained water vapor and chemicals released by

volcanic eruptions

In the 1920s, A. I. Oparin and J. B. S. Haldane hypothesized that

the early atmosphere was a reducing environment

experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible

Stanley Miller and Harold Urey

Miller-Urey type experiments demonstrate

that organic molecules could have formed in reducing, oxidizing, or “neutral” atmospheres

Amino acids have also been found in

meteorites

RNA monomers have been produced spontaneously from

simple molecules

Small organic molecules polymerize when they are concentrated on

hot sand, clay, or rock

what are the key properties of life?

Replication and metabolism

Protocells

may have been fluid-filled vesicles with a membrane-like structure

In water, lipids and other organic molecules can spontaneously form

vesicles with a lipid bilayer

internal chemical environment

Vesicles exhibit simple reproduction and metabolism and maintain

what was the first genetic material

RNA

ribozymes

RNA molecules

what have ribozymes been found to do?

catalyze many different reactions

Ribozymes can make complementary copies of

short stretches of RNA

what has natural selection produced?

self-replicating RNA molecules

Would RNA molecules that were more stable or replicated more quickly have left the most descendant RNA molecules? why?

Yes, RNA molecules that were more stable or replicated more quickly would have left the most descendant RNA molecules. This is because greater stability and faster replication would increase their chances of persisting and copying themselves more often, making them more likely to be passed on through generations.

Vesicles with RNA capable of replication would have been

protocells

what could RNA provided a template for DNA?

a more stable genetic material

The fossil record is biased in favor of species that:

-Existed for a long time

-Were abundant and widespread

-Had hard parts

strata

Sedimentary rocks are deposited into layers

The fossil record reveals

changes in the history of life on Earth

can fossil have a higher chance of being found or is it always by chance?

Fossil discoveries can be a matter of chance or prediction

how did paleontologists found Tiktaalik

by targeting sedimentary rock from a specific time and environmen

geologic record

divided into the Archaean, the Proterozoic, and the Phanerozoic eons

what was the Phanerozoic encompasses

multicellular eukaryotic life

what 3 eras is the Phanerozoic divided into?

the Paleozoic, Mesozoic, and Cenozoic

what does a major boundaries between geological divisions correspond?

to extinction events in the fossil record

stromatolites

rocks formed by the accumulation of sedimentary layers on bacterial mats

when do Stromatolites date back to?

3.5 billion years ago

who was the earth’s sole inhabitants and from how long?

Prokaryotes; 3.5 to about 2.1 billion years ago

what lead to the oxygen revolution?

O2 produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations

what lead to the extinction of the prokaryotic ?

oxygen revolution

how did some group survive the oxygen revolution?

Some groups survived and adapted using cellular respiration to harvest energy

what gave O₂ the rise?

ancient cyanobacteria

What did the O₂ gave the revolution to?

eukaryotic cells containing chloroplasts

when was the oldest fossils of eukaryotic cells date back to?

2.1 billion years

What is the structures of eukaryotic cell?

nuclear envelope, mitochondria, endoplasmic reticulum, and a cytoskeleton

endosymbiont theory

proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells

Serial endosymbiosis

supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events

Key evidence supporting an endosymbiotic origin of mitochondria and plastids:

-Inner membranes are similar to plasma membranes of prokaryotes

-Division is similar in these organelles and some prokaryotes

-These organelles transcribe and translate their own DNA

-Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes

the did the evolution of eukaryotic cells allow for?

greater range of unicellular forms

Cambrian explosion

refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period

what was the second wave of diversification lead to?

multicellularity evolved and gave rise to algae, plants, fungi, and animals

The oldest known fossils of multicellular eukaryotes are of small algae that lived about

1.2 billion years ago

Cambrian explosion

refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period

what few animals phyla appear before the Cambrian explosion

sponges, cnidarians, and molluscs

what did the Cambrian explosion provide evidence first?

predator-prey interactions

plate tectonics

Earth’s crust is composed of plates floating on Earth’s mantle

what is continental drift?

Tectonic plates move slowly

Oceanic and continental plates can do?

collide, separate, or slide past each other

Interactions between plates cause

the formation of mountains and islands, and earthquakes

Formation of the supercontinent Pangaea about 250 million years ago had many effects:

-A deepening of ocean basins

-A reduction in shallow water habitat

-A colder and drier climate inland

Continental drift has many effects

living organism

continent’s climate can change as it moves

north or south

Separation of land masses can lead to

allopatric speciation

The distribution of fossils and living groups reflects

the historic movement of continents

Name an example of distribution of fossils

South America and Africa is consistent with the idea that these continents were formerly attached

Extinction can be caused by

changes to a species’environment

mass extinction

is the result of disruptive global environmental changes

Name the 5 big extinction

Permian, Paleozoic, Mesozoic, Cretaceous, Cenozoic

A number of factor might have contributed to these extinctions:

-Intense volcanism in what is now Siberia

-Global warming resulting from the emission of large amounts of CO2 from the volcanoes

-Reduced temperature gradient from equator to poles

-Oceanic anoxia from reduced mixing of ocean waters

The Cretaceous mass extinction 65.5 million years ago separates the

Mesozoic from the Cenozoic

Organisms that went extinct include

half of all marine species and many terrestrial plants and animals, including most dinosaurs

What did the meteorite impact cause?

Dust clouds caused by the impact would have blocked sunlight and disturbed global climate

What is proof of the meteorite impact?

The Chicxulub crater off the coast of Mexico is evidence of a meteorite that dates to the same time

Is there a sixth mass extinction under the way?

Data suggest that a sixth, human-caused mass extinction is likely to occur unless dramatic action is taken

Mass extinction can alter

ecological communities and the niches available to organisms

The percentage of marine organisms that were predators increased after the

Permian and Cretaceous mass extinctions

Mass extinction can pave the way for

adaptive radiations

Adaptive radiation

is the evolution of diversely adapted species from a common ancestor

Adaptive radiations may follow:

-Mass extinctions

-The evolution of novel characteristics

-The colonization of new regions

Other notable radiations include

photosynthetic prokaryotes, large predators in the Cambrian Period, land plants, insects, and tetrapods

The disappearance of dinosaurs (except birds) allowed for the expansion of

mammals in diversity and size

Adaptive radiations can occur when

organisms colonize new environments with little competition

Where the the worlds’s great showcase of adaptive radiation?

The Hawaiian Islands

Exaptations

are structures that evolve in one context but become co-opted for a different function

The human brain

complex math, writing, and language skill