Bio 221 Combined

Fossils Reveal

Extinctions, ancient forms and adaptive radiation

Fossils Form

Need perfect conditions of desiccation, dehydration and mineralization

Subfossil

Evidence of organism, ex. Trackways

Chemical fossils

Fossil fuels represent carbonaceous deposits of fossilized marine algae

Biased Fossil Record

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

Incomplete Fossil Record

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

The Hadeon Eon

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

Archaeon 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,

Uranium Fossil Dating

Radiometric dating on rock for old things

Carbon Fossil Dating

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

Stromatolites

Oldest fossils, layered formed by bacteria mineralization

Proterozoic Eon

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

Great Oxygenation Event

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

Phanerozoic Eon

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

Fossils of Oldest known chordates (includes vertebrates)

Notochord, 520mya

Life originated in:

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

LUCA

Last Universal Common Ancestor (prokaryote)

Prokaryotes

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

Archaea

Extremophiles, microbes in extreme and regular environments

Origin of Eukaryotes

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

Acritarchs

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

Earliest multicellular fossils

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

Oldest animal fossils

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

Ediacaran fauna

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

Cambrian

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 Innovators (evolution of)

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

vascular plants evolved

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

Pneumodesmus newmani

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

Oldest known vertebrate

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

Non-exclusive Cambrian hypotheses

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

Paleogene Mass Extinction

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

Selection vs Evolution

Selection - occurs within a population

Evolution - occurs over generations

Rate of Evolution Drivers

Rate of reproduction

Selective forces

Environmental change

Four Mechanisms of Evolution

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

Georges Cuvier

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

Jean-Baptiste Lamarck

(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

Charles Lyell

(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

Thomas Malthus

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

Alfred Russell Wallace

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

Charles Darwin

(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

Evidence for descent with modification

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)

Darwin’s Postulates

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

Lamarckism

Transformational evolution, forms change that change is inherited

Darwinism

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

Linnaeus weaknesses

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

Principle of Parsimony

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

Stagnation

If inheritance was perfect and there was no mutations

Proteins

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

Genes

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

Histones

Protein octomers that organize eukaryotic DNA

Chromosomes

Arrangement of eukaryotic DNA and stored in nucleus

DNA Arrangement

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

Polyploid

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

Transcription

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

Translation

RNA converted to proteins by ribosomes

Redundancy

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

Gene regulation

Occurs at the transcription initiation

Promoter

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

Genome size

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

Isoforms

Similar but non-related proteins

Alternative Splicing

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

Exons

Sections of expressed DNA

Genome

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

Pseudogenes

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

How Meiosis Creates Genetic Variation

Crossing over, independent assortment, random fertilization

Crossing Over

Physical exchange of DNA between pairs of chromosomes

Independent Assortment

2 pairs of chromosomes assort independently in equally segregated patterns

Mutations

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

Point 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)

Transition Point Mutation

purine with purine or pyrimidine with pyrimidine (A to G/C to T)

Transversion Point Mutation

pyrimidine with purine or vice versa ( A to C/ G to T)

Synonymous Point Mutation

“Silent” no effects on amino acid protein sequences, mutational tolerance due to redundancy of a protein

Missense

Non-synonymous Point Mutation, encodes wrong amino acid, may effect structure ad function

Nonsense

Non-synonymous Point Mutation, creates a premature stop codon and truncated proteins, will affect structure and may affect function

Indels

Insertions and deletions of 1+ nucleotides. If indels occur in a protein-encoding sequence they cause a frame shift that affects all animal acids or codons after indel

Inversions

Flipping of a DNA segment within a chromosome, often causes no major changes

Duplications

Repeating the same sequence often in tandem with the original. Can have gene dosage effects. Often a result of transposable elements, and jumping genes, ABC —> ABCBCD

Translocations

Originally separate chromosomes to break and fuse with another chromosome

Karyotype

Number, size, shape and arrangement of an organism’s chromosomes, Changes in karyotype can affect the fertility of an individual and viability of the offspring

Aneuploid

Unbalanced number of chromosomes, eg. 2n+1 or 2n-1

Tetraploids

4n, more fertile than triploids (3n), type of polyploid, occurs to autopolyploids or allopolyploids

Autopolyploid

Gene duplication

Allopolyploid

Gene amplification due to hybridization between 2 species

Mutation Rarity

Point mutations are common, but some of the rarer events have greater effects (Like aneuploid), gene dosage;EAs to greater effects, odds of one base pair mutating is rare but ingredients for evolution

Hardy-Weinberg (H-W) equilibrium Conditions

Population must be infinitely large, have no net mutation, no net migration, mate randomly, have no selections for traits or phenotypes

Population

Group of interacting and potentially interbreeding individuals of a particular species

Population Genetics

Study of allele distributions within and among populations and how they change over time

No population subdivision

Individuals can interact with one another very easily

Intermediate population subdivision

Little pockets of individuals that can move between subdivisions but not continuously ex. snowshoe hares on campus

Extreme population subdivision

Populations that are completely isolated from each other ex. bears in different national parks

H-W violations

Lead to evolution: mutation, natural selection, migration, drift

Random Allelic Change

Due to drift and mutation

Genetic Drift

Random changes in the frequencies of 2 or more alleles/haplotypes/genotypes, force that can do allelic change that is not due to selection, often considered sampling error, ex. elephant stepping on ladybugs so only yellow survives

Haplotype

Multiple genetic loci that pass on together

Drift Impact

Dependent on population size, allelic frequencies change genotypic frequencies

Larger the population the more genetic stability

Smaller population have the biggest fluctuations, more variation in allelic frequency and fixation is less likely

Drosophila lab experiment

8 males and 8 females are randomly mated, found over 19 generations the brown eyed allele is lost and other allele is fixed after 30 generations

Biggest problems with genetic drift

• problem with conservation, favours fixation with is not stable at 2 extremes

• At the point of species being endangered, fixation probability increases

• Loss of genetic diversity

Bottleneck

Type of drift, when’s population undergoes a rapid constriction in population size and then expands, allelic frequency in surviving groups may not reflect frequency in original population, rare alleles more likely to be lost, ex. Northern elephant seal was hunted to near extinction then the population expansion showed less genetic diversity

Founder Effect

Occurs when an offshoot of a bigger population establishes a new population, new population alleles dependant on the alleles the founders carry, more common alleles will be represented but some randomness, ex. Many people on a ship experience migraines and are related

Inbreeding

Mating with close relatives, violates random mating and H-W