Chapter 25: The History of Life on Earth

Early though of how Earth began

1.Extraterrestial

2.Primordial Soup

3.Intelligent Design

4.Protocells/ Endosymbiotic

Origin of Life: Early Earth Condition

Chemical and physical process of early earth produced a simple cell

What are the stages of early earth condition of origin of life?

-Abiotic synthesis of small organic molecule

-Join small molecule into macromolecules

-Package molecule into protocells

-Origin of self replicating molecules

1920, Oparin and Haldane hypothesized

the early atmosphere was reducing environment

1953, Miller and Urey

Demonstrated the abiotic synthesis of organic molecule in a reducing atmosphere was possible

The first organic compound might have formed

In reducing conditions near the opening of volcanoes

Other hypothesis of Organic Compound production: Hydrothermal Vents

Area of deep sea floor where hot water and mineral gush from earth interior into the ocean

Black smoker in deep sea release water at

300-400 degree celcius

Alkaline Vent

Release water with High pH (9-11) and warm water (40-90)

Which will be more suitable to form organic molecule, The Hydrothermal vent or Alkaline vents

Alkaline vents

Another source of Organic Compound

Meteorites, Fragment of Murchison meteorite contain more than 80 aa, including other key organic molecules, including lipids, simple sugars, and nitrogenous bases

What is Protocell

Basic cell before the real cell

Protocell may have formed form

Fluid filled vesicle with a membrane like structure

Montmorillonite is

a soft mineral clay common on early Earth that greatly increases the rate of vesicle formation

The vesicle growth

Exhibit simple growth, reproduction and metabolism

How self replicating RNA was formed?

Through natural selection

RNA is the

First genetic material on Earth

Hypothesis of Genetic material (RNA / DNA)

-2013 Researcher constructed a vesicle that self replicates

-Early earth vesicle passed RNA to its daughter= Daughter being the protocells

-Successful protocell could have increased through natural selection

-RNA could have provided the template for the formation of DNA

-Double-stranded DNA is more chemically stable and can be replicated more accurately than RNA

Which of the following support the idea of a protocell as the origin of life on Earth?

All of the Above

Sediment Rock

-Rock formed from pre-existing rocks or pieces of once living organism with distinct layer

Distinctive layer of rock

Strata

The bias of Fossils are, It favors species that

-existed for a long time

-were abundant and widespread

-had hard parts, such as shells or skeletons

Radiometric Dating

Tool used to determine the age of fossil through half life

Half Life is

The time required for half of the element (isotope) to decay

Isotopes of organism are

accumulated when they were alive

How can you determine the age

Measure the ratio of radioactive isotope (parent) to daughter isotope (stable form)

Origin of New group of organism

The evolution of unique mammalian feature can be traced with fossil record

Tetrapods

Mammal group of animals with four limbs and vertebrae

Geologic Record

-the complete history of Earth as preserved in layers of rock, fossils, and sediments. It provides crucial evidence about the formation of the Earth, life evolution, past climates, and major geologic events.

Geologic Record is divided into

-Hadean Eons

-Archaean Eons

-Proterozoic Eons

-Phanerozoic Eons

Hadean Eons

-4.6-4 billion years ago

-Earth formation

Archaean Eon

-4-2.5 billion years ago

-Origin of life, First simple life

Proterozoic eons

-2.5 billion - 541 million years ago

-First eukaryotes, early multicellular life

Phanerozoic Eons

-541million year -current

-Visible life

Phanerozoic Eon is divided into 3 eras

1.Paleozoic

2.Mesozoic

3.Cenozoic

Paleozoic Era

-541 to 252 million years ago

-Explosion of marine life

-First fish, insect and reptile

Mesozoic Era

-252-66 million years ago

-Age of reptiles and dinosaurs

-First bird, mammals and flowers

Cenozoic Era

-66 million to present

-Mammal era, flower, grass and humans

What is the cause of the era?

Major extinction event in the fossil record

Stromatolites is

-The oldest fossil

-bacteria mat

-3.5 billion years ago

Prokaryotes were

the earth’s sole inhabitant for 1.5 billion years

Oxygen Revolution, When did it appear in the atmosphere

-Accumulated in the atmosphere around 2.7 to 2.4 billion years ago

-Then shot up rapidly between 1-10% of its present level

The oxygen revolution caused

-Extinction of prokaryotic groups

-Some survived in anaerobic environment and other adapted using cellular respiration

When the first eukaryotes appeared?

1.8 billion years ago

How did the Eukaryotes originated?

By Endosymbiosis: prokaryotes engulfed a small cell that would evolve into mitochondrion

What is an endosymbiont

Cell that lives within a host cell

What is serial Endosymbiosis

Mitochondria evolve before plastid through a sequence of endosymbiotic event

Mitochondria and plastid likely descended from

bacterial cell

Evidence that endosymbiotic origin of mitochondria and plastids:

-Inner membranes of both organelles are similar to plasma membranes of living bacteria

-DNA structure and cell division are similar to bacteria

-Both organelles transcribe and translate their own DNA

-Ribosomes are more similar to bacterial than to eukaryotic ribosomes

Multicellularity, a second wave of diversification

Evolution that gave rise to algae, plants, fungi and animals

What is the oldest multicellular eukaryote fossil

Small red algae about 1.2 billion years ago

Cambrian Explosion

-535 to 525 million years ago

-The most major animal phyla first appeared in the fossil record

-First evidence of prey and predator

-Sponges, Cnidarians and Mulluscs

How long ago did fungi, plants and animals started to colonza

about 500 million years ago

Plants evolved and avoided dehydration

Vascular system of transporting material in plants

Tetrapods evolved from

Lobe finned fishes around 365 million years ago

Modern human originated about

195,000 years ago

Sequence the order of events for tetrapod formation on Earth.

1: Land colonization

2: Oxygen production

3: Multicellular Eukaryotes

4: Endosymbiosis

5: Animals

6: Stromatolite formation

6,2,4,3,5,1

The landmass of Earth have formed a supercontinent

Three times over the past billion years

(1 billion, 600 million, and 250 million years ago)

Plate Tectonics

The theory that the Earth’s crust is composed of plates floating on Earth’s mantle

The movement of mantle is a process known as

Continental drift

If the continental plates collide form

Mountains

If the continental plates slide past each other

Cause earthquakes

What are some consequences of Continental Drift? Formation of Pangaea about 250 million years ago

-Deepening of sea basins

-Reduction of shallow water habitat

-Colder and drier climate inland

-Affect on living organism: allopatric speciation

Based on history how many mass extinction happened?

5

Permian Extinction

-Boundary between the Paleozoic and Mesozoic eras 252 million years ago

-Occurred less than 500,000 years

-Caused extension of 96% marine species and 70% land species

What are some factors of Permian Extinction?

-Extreme Volcanism

-Global warming due to excessive volcanism-Acidification of ocean

-Anoxic Condition: No oxygen due to nutrient enrichment in the environment

Cretaceous Mass Extiction

-66 million years ago

-More that half of the marine species, many terrestrial plans and animals and all of the dinosaurs except birds went extinct during this event

What are some factors of n Cretaceous Mass Extiction?

-Presence of iridium in the sedimentary rock suggest a meteorite impact

-Possible dust cloud, blocking the sunlight and disturbed global climate

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

What are some of the consequences of mass extinction?

-Too long to recover: about 5-10 million years

-IT changes the type of organisms found in the ecological communities

-Eliminated lineages with novel and advantageous features

What is Adaptive Radiation?

Single ancestral species rapidly diversifies into many new speciesA

Adaptive Radiation may follow

-Mass extinction

-The evolution of novel Characteristics

-The colonization of new region

Adaptive Radiation: mammals

Mammals underwent an adaptive radiation after the extinction of terrestrial dinosaurs

The disappearance of dinosaurs also opened

ecological niches allowing the expansion of mammals in diversity and size

Other notable radiations include

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

Developmental gene control

the rate, timing, spatial pattern of changes in an organism’s

Heterochrony

-An evolutionary change in the rate or timing of developmental events

-It can have a significant impact on body shape

Example of Heterochrony

the contrasting shapes of human and chimpanzee skulls are the result of small changes in relative growth rates of different body parts

Heterochrony can alter

The timing of reproductive development relative to the development of nonreproductive organs

Two types of Heterochrony

Paedomorphosis

Peramorphosis

Paedomorphosis

Rate of reproductive development accelerates compared with somatic development

-The sexually mature species may retain body features that were juvenile structures in an ancestral species

Peramorphosis

Development is extended or accelerated

-longer beaks than ancestor species

Homeotic genes

determine such basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged

Gene sequence change

Change the form of organism from its ancestral species

Exaptations

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