Bio 221

Extinctions, ancient forms and adaptive radiation

Fossils Reveal

Need perfect conditions of desiccation, dehydration and mineralization

Fossils Form

Evidence of organism, ex. Trackways

Subfossil

Fossil fuels represent carbonaceous deposits of fossilized marine algae

Chemical fossils

Hard bony parts fossilize best, microbes don’t fossilize, aquatic organisms fossilizes better (more minerals and no O2 so decompose slower), dating rocks is hard

Biased Fossil Record

Only found easy to find fossils, hot humid areas do not give rise to fossils

Incomplete Fossil Record

‘hellish’ eon, no evidence of life, melted crust, orbit shift, no liquid water, very volatile, volcanos and meteorites, 4.55 to 3.8bya

The Hadeon Eon

Earliest forms of unicellular life, Life was limited to the oceans with only trace oxygen in atmosphere, 3.8 – 2.5bya, bacteria evolved before archaea,

Archaeon Eon

approximately 3.8 billion years old, by principle of supposition

Life on Earth Start Date

Radiometric dating on rock for old things

Uranium Fossil Dating

Radiometric dating of fossils for younger things <50, 000, can date tissue with C14 in atmosphere

Carbon Fossil Dating

Oldest fossils, layered formed by bacteria mineralization

Stromatolites

Beginnings of eukaryotic and multicellular life and Great Oxygenation Event, 2.5bya - 500mya

Proterozoic Eon

2.5bya, oxygen increased in the atmosphere and the evolution of photosynthesis

Great Oxygenation Event

500mya – present, The Cambrian explosion marked the evolution of the modern day animal body plan (3 sections), Three eras – Paleozoic (old life), Mesozoic (middle life), Cenozoic (new life), rapid evolutionary change

Phanerozoic Eon

Notochord, 520mya

Fossils of Oldest known chordates (includes vertebrates)

480mya

Oldest trackways

475mya, late Ordovician or early Silurian, probably liverwort like

Oldest land plant fossils

360mya

Oldest land vertebrates

230mya

Dinosaur Evolution

180mya

Common mammalian ancestors date

150mya

Bird Evolution

Deep sea vents - tons of energy, tons of carbon and lots of redox worthy chemicals

Hot springs – tons of energy and nutrients, lots of oxidized minerals

Life originated in:

Minerals coming up from earths core

Redox Reactions

Last Universal Common Ancestor (prokaryote)

LUCA

No membrane bound nucleus, has phospholipid bilayer, branches into Archaea and bacteria

Prokaryotes

Extremophiles, microbes in extreme and regular environments

Archaea

Approximately 1.8 bya, First 2 billion years of life on the planet (3.8-1.8bya) – no fossil evidence of anything other than prokaryotes

Origin of Eukaryotes

Early eukaryotes, single-celled, ambiguous origin, large and structurally complex

Acritarchs

1.6 BY old and interpreted as filamentous algae, discovered by Gabon

Earliest multicellular fossils

Sponges, Believed to be 635 myo, has animal bio/chemical signature (cholesterol like molecule), looks like plants

Oldest animal fossils

Earliest animals, Oldest example found at the Drook formation in Newfoundland and Labrador, 575 myo, Mostly fossilized sponges, jellyfish and comb jellies and frond-like organisms, wiped out during mass extinction

Ediacaran fauna

Around 541 mya the entire ocean ecosystem was reorganized and new animal body plans emerged

Most major extant animal phyla make their first appearance in deposits starting around 550 mya

Best known deposit is the Burgess Shale in BC (Yoho National park), start of modern body part, evolution of genes, trilobites, molluscs, first chordates

Cambrian

Segmentation, bilateral symmetry (dorsal/ventral), increased size and complexity, notochord and spinal column

Cambrian Innovators

Because of increased sun, End of Devonian – Earth was covered in ferns, horsetails and first seed plants

vascular plants evolved

Oldest known land animal, 428 mya millipede, evolved to live in intertidal zones

Pneumodesmus newmani

370 mya and most likely amphibious moving back and forth between water and land, First amniotes (produced shelled eggs) are hypothesized to have evolved 314mya, then split into diapsids and synapsids

Oldest known vertebrate

1. Increased oxygen allowed more primary productivity - plants, algae, emergence of predators, secondary consumers, increased body size (but oxygen levels were ambiguous and larger animals already existed

2. Evolutionary Innovations - segmentation, adaptability, eg. hox genes cluster sparked Cambrian, building blocks got complex

3. Predation/Arms race in the ocean (could explain increased body size, hard body parts and mobility

Non-exclusive Cambrian hypotheses

Meteor hit earth 66mya, end of Mesozoic, loss of big reptiles and mammals thrived

Paleogene Mass Extinction

Age of mammals, 66mya-now

Primates - 55mya

Apes - 20mya

Hominids - 7mya

Homo sapiens - 0.2mya or 200 000 years ago

Cenozoic

Selection - occurs within a population

Evolution - occurs over generations

Selection vs Evolution

Rate of reproduction

Selective forces

Environmental change

Rate of Evolution Drivers

Different morphs of the same species

Artificial Selection

1. Mutation (ingredients of evolution) - do not always cause phenotypic change, debated

2. Drift - random changes to the genetic makeup of a population

3. Natural Selection - caused by interactions of genotype with environment

4. Artificial Selection - caused by humans

Four Mechanisms of Evolution

(1769-1832), Anatomist, thought extinctions caused by catastrophes

Georges Cuvier

(1744-1829), Zoologist at the Natural History Museum in France and arranged fossils in stratigraphical order, Curated fossils and extant mollusks, Suggested species change over time from use and disuse theories and interactions with the environment

However thought human have been around forever and microbes appeared spontaneously

Jean-Baptiste Lamarck

(1797-1875), Geologist, Found that land forms are not fixed but changing slowly as a result of geological processes, Estimated earth was much older than biblical 6000 years

Charles Lyell

(1766-1834), found that human population increased faster than food supply, competition leads to survival of the fittest

Thomas Malthus

(1828-1913), Naturalist, Came up with the idea of natural selection independently of Darwin and encouraged him to publish

Alfred Russell Wallace

(1809-1882), Aboard the Beagle from 1831-1836 as a natural historian to accompany the captain, Collected specimens and fossils and found patterns of distributions of traits, particularly in the distribution of beak length in finches between Galápagos Islands because of seed sizes, Wrote “The Origin of the Species by Natural Selections” and found Descent with modification, did not understand how modification or inheritance occurred

Charles Darwin

Variation (exists in all species), Artificial selection (allows enhancement of desired traits), Distribution of species in time and space (variance exists between or within series, if true similar species should be found in similar places)

Evidence for descent with modification

Individuals vary in some traits, Some of the differences are passed to offspring, enquires hereditary, may affects survival, fitness and reproduction (more offspring survive), survival is nonrandom and based on favourable traits for the environment, common decent and ancestors

Darwin’s Postulates

Transformational evolution, forms change that change is inherited

Lamarckism

Most forms die and few that survive contribute traits to next generation

Darwinism

Plants (Regnum Vegtabile), Animals (Regnum Animale), Minerals (Regnum Lapideum)

Linnaeus three Kingdoms

When creating kingdoms he added minerals but they aren’t alive, was racist and classified humans in different species, didn’t believe species could evolve

Linnaeus weaknesses

Domain, Kingdom, Phylum, Subphylum, Class, Order, Family, Genus, and species

Organism Classification

Designated example specimens best representing a species, used as a comparative point for new fossils, must be available to public and reaserchers

Type Species

Single designated specimen used as a type or name bearer

Holotype

Collection of specimens used as a type for a species

Paratype

1834-1919, developed first phylogenetic trees

Ernst Haekel

1913-1976, founded cladistics with flies

Willi Hennig

Species known to have or suspected to have split off prior to diversification event, allows for a starting point and a control, not primitive species, can have ancestral state and derived characteristics

Outgroup

Morphological, behavioural, biochemical (certain enzymes), genetic (DNA, protein function)

Informative characteristics for trees

1. Relationships among taxa form a dichotomous branching pattern

2. Synapmorphies provide evidence for recentness in common ancestry

3. Principle of Parsimony

4. Cladogram (consistent with inferred patterns of historical relationships)

   Should be reconstructible

Four main points of cladistics

Unresolved tree or more than one parsimonious tree

Polytomy

Homoplasies and reversals back to the ancestral state

Complications to the Principle of Parsimony

Philosophical argument that if you have to decide between two alternative explanations, the best choice is always the simplest one,the one that requires the fewest assumptions

Occam’s Razor

The cladogram that is most likely correct is the one that requires the least changes

Principle of Parsimony

Trait in more than 1 ingroup not outgroup

Synapomorphy

Shared ancestral trait, present in ingroup and outgroup

Symplesiomorphy

Derived trait found only in one taxon, ex. Retractable claws in cats

Autapomorphy

States that are present in more than 1 taxon and arose independently more than once (same as convergent evolution)

Homoplasy

Character states present in more than 1 taxon and arose once in common ancestor

Homology

If inheritance was perfect and there was no mutations

Stagnation

Machines of the cell and where variation allows selection, Chains of amino acids folded into unique 3D structures

Proteins

Protein with one amino acid chain

Monomer

Protein with multiple amino acid chains

Oligo/Polymer

Sequences of DNA that encodes for a trait that can be selected for

Genes

Protein octomers that organize eukaryotic DNA

Histones

Arrangement of eukaryotic DNA and stored in nucleus

Chromosomes

Protects DNA from damage, organizes nucleus, limits access of transcriptional machinery to DNA

DNA Arrangement

Genus with over a hundred sets of chromosomes, fern genus is 84n, common in plants, duplication of entire genome, often results in sterility especially if chromosome number is odd

Polyploid

DNA converted to mRNA, only one strand is used as a template

Transcription

RNA converted to proteins by ribosomes

Translation

Also known as degenerate, at 3rd position of a codon, allows mutational tolerance

Redundancy

Occurs at the transcription initiation

Gene regulation

Sequence of DNA like a light switch that regulates transcription initiation, bond by transcription factor tells it to activate, required

Promoter

Genome size is unrelated to complexity, depends only on how it’s used

Genome size

Similar but non-related proteins

Isoforms

mRNA can be rearranged into different combinations of exons and form isomers

Alternative Splicing

Sections of expressed DNA

Exons

Most of it is not expresssed and most does not become proteins, has regulatory and repetitive sequences

Genome

Type of repetitive sequence, mutated genes that look normal but lack a promoter

Pseudogenes

Crossing over, independent assortment, random fertilization

How Meiosis Creates Genetic Variation

Physical exchange of DNA between pairs of chromosomes

Crossing Over

2 pairs of chromosomes assort independently in equally segregated patterns

Independent Assortment

Sperm that fertilizes isn’t necessarily the strongest, there is variation

Random Fertilization

Common, random, all types are equally likely, occurs during DNA replication, due to environmental exposures (eg. muatagens), comes before selection and environment determines if it has benefits, mostly not inherited because it occurs in the soma

Mutations

Involves a substitution of a single base with a different base, Can be: Transitions or Transversions

IF a point mutation happens in a coding region it can result in a simple protein mutation and can be Synonymous or Non-synonymous (missense or nonsense)

Point mutations