Fossil Records and Earth's History

Fossil Record

• Fossils act as a historical record of life forms
• Paleontologists use fossils to learn about past life and environments

What is a Fossil?

• Fossils give clues about the evolution of organisms long ago
• Fossils offer insights into how the Earth's surface has changed
• Fossils provide information for scientists to understand past environments

Fossil Formation

• Sediment such as volcanic ash or silt, an animal is buried, protecting bones from decay.
• Layers of sediment accumulate above the remains and minerals like silica replace calcium phosphate in bones
• Movement of tectonic plates lifts sediments, pushing fossils closer to surface
• Erosion from rain, rivers and wind wears away rock layers, exposing preserved remains
• Bones/hard parts mineralized by groundwater
• Trace fossils are indirect evidence of organisms, like tracks, trails, wormholes, burrows, nests, feces and calcite mounds

Early Earth - 4.6 Billion Years(b.y.) Ago

• Solar system coalesced from cosmic dust and gas
• Gravitational compaction caused nuclear fusion in the sun
• Planetesimals gathered to form planets, leftovers formed asteroids and comets.
• Earth was likely molten, bombarded by planetesimals - 4.5 b.y.
• The first atmosphere was stripped by solar wind or impacts, but replenished by volcanic eruptions
• It was too hot for liquid water to exist
• Oceans formed, water vapor in the atmosphere condensed and rained out to form oceans - 4.4 b.y.
• Laboratory experiments simulating an early atmosphere have produced organic molecules from inorganic precursors, but the existence of such an atmosphere is unlikely.

Origin of Life - 3.8 b.y.

• Earth was still heavily impacted by meteorites/volcanic eruptions
• First life necessitated chemosynthesis of organic compounds like amino acids from inorganic materials
• Deep ocean thermal springs, protected from meteorite bombardment, as most likely place for life to develop
• Raw materials and heat for chemosynthesis were available there
• Microbes formed in aerosols(liquid droplets/solid particles)
• Rocks in Greenland formed as byproducts of microbial activity - 3.8 b.y.

Oxygen Atmosphere - 1.8 b.y.

• Chemical sediments from 2.0 to 1.8 b.y. consist of oxygen-poor and oxygen-rich iron minerals
• Interlayering reflects a transition from an oxygen-poor to oxygen-rich atmosphere

Early Life

• All organisms are composed of cells, a complex grouping of chemical compounds enclosed in a membrane
• Prokaryotic cells store DNA without separation from the cytoplasm, lacking a well-defined nucleus
  • Prokaryotic cells are earliest, simplest, and anaerobic
• Eukaryotic cells have a distinct nucleus surrounded by a membrane and other membrane-bounded organelles
  • Eukaryotic cells are larger, more complex, and mostly require oxygen
  • Most advanced life forms are Eukaryotes

Evolution of Life Summary

• Early Earth had a poisonous atmosphere and was hot
• Earth cooled, forming oceans
• Simple organic molecules and small RNA sequences may have formed in the oceans and replicated
• First prokaryotes emerged when RNA/DNA were enclosed in microspheres.
• Later prokaryotes photosynthesized and produced oxygen
• Oxygenated atmosphere and ozone layer protected Earth
• First eukaryotes may have been communities of prokaryotes
• Multicellular eukaryotes evolved
• Sexual reproduction hastened evolution by increasing genetic variability

Patterns of Extinction

• Taxonomic/Pseudoextinction is the transformation of a single evolutionary line, with earlier and later members bearing different names
  • Example: Homo erectus is now considered extinct, only when its became Homo sapiens
• True Extinction is extinction of a lineage without descendants
  • Example: Tyrannosaurus rex
• Despite the prevalence of extinction, very little is known about its causes
• Extinction is linked to physical environment changes like decreases in oxygen or temperature changes
• Biological factors include prehistoric overkill by early humans, relating to extinction of large mammals during the Pleistocene
• Extinction rates often increase when previously isolated biotas come into contact
• Predation and competition is also a key factor
• Disease can devastate forms without resistance
• Habitat destruction is now the greatest cause today
• If this has been a common cause the survival or extinction of species may depend not on adaptations, efficiency, competitive ability, or even genetic flexibility, but on the habitats it may occupy
• Extinction might be almost random and not depend on adaption

The Five Mass Extinction Events

The End Ordovician Mass Extinction

• Was the earliest, ~439 million years ago
• Insects and tetrapods had not developed so they were not affected
• Marine organisms most affected like brachiopods, cephalopods, echinoderms, graptolites, Solitary corals and trilobites.
• Plant were not affected
• Suggested causes includes, climate change and a sea level drop

The Late Devonian Mass Extinction

• Was the second, ~365 million years ago
• Insects and tetrapods had not developed so they were not affected
• Plants: the rhyniophytes decreased.
• Marine organisms affected: ammonoids, brachiopods, corals, agnathan fish, placoderm fish, ostracods and trilobites.
• Climate change and asteroid impacts are suggested causes

The End Permian Mass Extinction

• The third(biggest), ~245 million years ago
• Known as the 'Great Dying'
• Plants: the previously dominant Ottokariales (glossopterids) became extinct
• Insects: about two thirds of the insect families became extinct and six insect orders disappeared.
• Tetrapods affected: amphibians and mammal-like reptiles
• Marine organisms affected: benthic foraminifera, brachiopods, bryozoans, echinoderms, 44% of fish families, all graptolites, solitary corals and all trilobites.
• Suggested causes climate change, a drop in sea level, massive carbon dioxide (CO2) poisoning and oceanic anoxia

The End Triassic Mass Extinction

• Was the fourth, ~210 million years ago
• Plants: several orders of gymnosperms were lost and the Umkoma-siales (Dicroidium) became extinct.
• Insects: not severely affected. Tetrapods affected some reptile lineages - the mammal-like reptiles (therapsids) especially.
• Marine organisms affected: ammonites, ammonoids, bivalves (Molluscs), brachiopods, corals, gastropods and sponges.
• Suggested causes include climate change, one or more asteroid/comet impacts and volcanic activity.

The End Cretaceous Mass Extinction

• Was the final and best known 65 million years ago
• Plants: debatably up to 75% of species lost
• Insects: not severely affected.
• Tetrapods affected: 36 families from 3 groups including dinosaurs ,plesiosaurs and pterosaurs.
• Marine organisms affected: ammonites, ammonoids, cephalopods, bivalves, foraminifera, icthyosaurs, mosasaurs, plackton and rudists.
• asteroid/comet impact, climate change and volcanic activity were suggested causes

The Sixth Mass Extinction (Holocene Extinction)

• This phase began with the dispersal of modern humans 100,000 years ago
• Possible causes are human impacts or climate change
• This phase began with the development of agriculture - ~10,000 years ago
• Agriculture led to expansion of human activity outside local ecosystems
• Major environmental changes are caused by humans
• This phase drivers, including agriculture; human overpopulation; overexploitation; and invasive species
• Current estimates show we are at a rate of about: 4000 extinct species /year, with an extinction of one species every 15 minutes
• Possibility of future human extinction exists from natural causes that either increase or decrease sub-replacement fertility or also as omnicide with anthropogenic (human) causes

Geological Time

• Eon - The largest division of geologic time, lasting hundreds of millions of years
• Era - Two or more geological periods
• Period - The basic unit of geological time, which lasts tens of millions of years
• Epoch - The smallest division of geologic time
• Age - Is a unit of geological time, which consists of some feature that is shorter than an epoch
• The Archean Fossil Record
  • Oldest known fossils are chains of prokaryotic cells and some related rocks in Greenland 3.5 b.y. old
• The Precambrian Fossil Record
  • Evidence of microbial activity during the Proterozoic and Archean is recorded in fossil stromatolites
• The Proterozoic Fossil Record
  • Eukaryotes were oldest 1.4 b.y.a.
  • Eukaryotes were common by 1.0 b.y.a.
• The Late Proterozoic Fossil Record
  • Ediacara fauna include marine animal and plant fossils that are 600 million years old
• Mawsonia spriggi - a floating, disc-shaped animal like a jellyfish
• Dickinsonia costata -worm-like
• Ozone developed to level where it blocked ultraviolet radiation
• Eukaryotes invented sexual reproduction

The Cambrian

• beginning of period of great diversification: Higher atmospheric oxygen affected skeletal biochemistry and supported larger organisms

The Ordovician

• Seas held diverse marine invertebrates with sophisticated adaptations

The Silurian

• This was the Golden Age of cephalopods and brachiopods
• First land plants/arthropods (scorpion-like invertebrates)

The Devonian

• Is the Golden Age of Fishes, first land plants and vascular plants
• These plants supported limbs and vascular systems

The Carboniferous

• Is the Age of Amphibians; first winged reptiles and first winged insects.
• Ichthyostega had features like a tail like a fish, and it had legs
• Diplovertebron seymouriamorph amphibian with features;

The Triassic

• Is when there were the first dinosaurs and mammals; explosive radiation of dinosaurs. (Primitive Ornithischia, an early dinosaur).

The Jurassic

• Is the Age of dinosaurs

Cretaceous and Tertiary

• Is when birds appeared and mammals diversified
• Evidence as nesting mothers around dinosaur eggs suggests that dinosaurs cared for young
• After the Cretaceous boundary, flowering plants diversified

The Tertiary: Eocene and Miocene

This is when grassland spread and some of the most well known life forms diversified

Quarternary: Pleistocene and Holocene

• Is when there were mammals and a host of modern humans diverged and colonized most enviorments
  • homo erectus developed large brains, tools, weapons, fire to survive in the changing enivroments

Systematics

Introduction

Systematics is the Latinized Greek word "systema” (organized whole) as applied to systems of classification developed by early naturalists

• Carolus Linnaeus developed Systema naturae Systematics is about the scientific study of the kinds & diversity of organisms & of any & all relationships among them

Challenges to Systematics

• Only just over 1/2 million species have been named, with an estimated 5% organisms that ever lived
• New organisms are still being found and identified

Why Systematics matters

• It is a foundation and integrative science on plant biology; economic botany and conservation of rare and endangered species It is also fun
• New technologies constantly bring new data meaning there is constant evaluation

This field requires access to:

• Field collections
• Lab stocks/ natural populations
• Biological or ecological and climate and weather
• Statistical or computational tools for soil chemistry
• Frozen tissue and extracts; gene and protein sequencers
• DNA or protein patterns
• Clones, patents, gene

Biological Methods Used in Systematics

Include

• Comparing phylogenetic genes & molecular genetics to determine relationships based on anatomy; habitat; reproduction; behavior & evolutionary history
• Global understanding using knowledge-based biology for studying epidemiology
• Providers: systematic data used in expertise to the fauna
• Collections made to plan for the future

Systematics Work products

Consist of Peer reviewed publications as manual collections and specimens for the field

Kingdoms and Domains

• Linnaeus originally proposed two kindoms: Animalia and Plantae
• Later, by the 1950s, scientists expanded the kingdom system
• The Five Kingdoms*
• The Monera kingdom consists of bacteria
• The Protista kingdom consists of amoeba, slime mold
• The Fungi kingdom consists of mushrooms, yeasts, molds
• The Plantae kingdom consists of flowering plants and mosses
• The Animalia kingdom consists of mammals, birds to worms and sponges

Domains

• In recent years, biologists have recognized that the Monera are composed of two distinct groups with distinct differences
• The Three Domains (Eukarya, Bacteria and Archea) are the modern way of classifying
• The Three Domains Include*
• Bacteria vs Archaea
• Archaea-bacteria
• EuBacteria
• Animalia and Fungae

The Component Fields of Systematics

• Includes diversity; classification and genetics based in comparative systematic studies
• phylogenetics and evolutionary lineages are often represented as tree diagrams based on their lineage

Systematics Goals

• To inventory the world’s organisms with a coherent relationship and classification to find any new species

To Do This:

• Comparative genetics are a tool to find any variations
• Need to compare any known organisms, and look for any different attributes that might shared based in a ecological or species
• Linnaeus has been attributed to grouping species as similar through recognizable taxonomies based on morphology

Tools of Systematics

• Currently, systematists use
• Biochemical and genetic testing
• Comparing characteristics across groups They

Taxonomy and Nomenclature.

• Is the defining science for names based in shared traits versus synapomorphies with classifications dependent on the author

Major areas

• By characterizing particular taxon with descriptions, distributions, in monographs of the taxon to create floristics to catalog any relationships

To properly follow taxonomy

• There must be a phenetic and phylogenetic analysis done for each case based on similarity
• Many traditional classifications systems are phenetic with only descent in mind

Taxonomic process

• The science is used identify any new samples after it has been described, identified and named depending if there is any similar traits such as color or shape
• Taxonomists use taxonomic key to simplify this and follow expert determinations as well by comparing samples
• The naming is formal through a standardized system that is a product of the the Code of Botanical and Zoological Systems by following language

Binomial Nomenclature

• Can be followed based in morphology which can be found in different species within the taxa from different experts which can be used to determine gender
• It can perpetuate across multiple fields and follow specific traits from the plant

To fully follow taxonomies

• Must follow the codes for rank as well with a holotypes and isotypes for unique species in the right setting to be recognized
• The different type of features for plants based on specific aspects and what the plant does
• Must follow what species it belongs in at its code

Disadvantages to Common names:

• It depends on the observer, so common names are inconsistent with that language, can only refer to one taxon if the user
• It requires a taxonomist to be studied, hence the commonness is limited through various fields

Explore the fossil record, how fossils form, and what they tell us about the history of life on Earth. Learn how paleontologists use fossils to understand past life, environments, and the evolution of organisms over millions of years.