BIOL 214 Exam 1 Prep Lecture 2

What abilities are required for life?

Store, transmit, express, and modify information over time, (plus growth, reproduction, and regulation) (STEM)

Cell Theory

1) All organisms have cells. 2) Life's chemical reactions occur in cells. 3) Cells contain DNA. 4) Cells come from pre-existing cells.

Why is the origin of the first cell a problem for Cell Theory?

Cell Theory states cells arise from pre-existing cells, but the first cell could not.

Four major stages proposed for the origin of life

1) Abiotic synthesis of small organics 2) Macromolecule assembly (including nucleic acids and proteins) 3) Protocell packaging of these molecules 4) Self-replicating molecules (that made inheritance possible)

Abiotic

Nonliving; abiotic synthesis produces biological compounds without living organisms.

Protocell

An early membrane-bound entity maintaining an internal environment distinct from its surroundings.

Major problems an origin-of-life hypothesis must explain

Origin of organic compounds, energy source, precursor assembly, molecule protection, and reaction location.

Panspermia hypothesis

Hypothesis that life or biological precursors originated elsewhere and reached Earth via comets or meteorites.

Does panspermia prove life originated in space?

No; most researchers favor life arising on Earth, though space material may have supplied compounds.

Murchison Meteorite

1969 Australian meteorite containing amino acids and high levels of organic compounds (glycine, alanine, glutamic acid, valine, proline, etc.) Implied that early life may have been "seeded" by organic compounds falling from the skies

Why is the Murchison Meteorite important?

It shows biologically relevant organic molecules can exist extraterrestrially and seed Earth.

Late Heavy Bombardment (LHB) or Lunar Cataclysm

Period 4.6-4 BYA when heavy asteroid/comet impacts potentially delivered organic compounds to young Earth (scary rock storm)

Oparin-Haldane hypothesis

Proposal that life arose on early Earth through gradual chemical evolution, "primordial soup" (early oceans = vessels of organic compounds)

Reducing atmosphere

An oxygen-poor early atmosphere on Earth facilitating reactions that form organic compounds.

Energy source in Oparin-Haldane hypothesis

Lightning and ultraviolet radiation.

Primordial soup

Haldane's concept of early oceans as large reservoirs of accumulated organic compounds.

Miller-Urey experiment — purpose

Tested whether organic molecules could form abiotically under simulated early-Earth conditions.

Miller-Urey experiment — gases/materials

H₂O, CH₄, NH₃, and H₂.

Miller-Urey experiment — lightning

Electrical sparks from electrodes provided reaction energy to simulate lightning.

Miller-Urey experiment — water cycle

Evaporated heating, electrical gas exposure, and condensed cooling simulated evaporation and rain.

Major result of Miller-Urey

Produced amino acids, proving organic precursors can form abiotically.

What did Miller-Urey NOT produce?

It did not create life, only abiotic organic precursors like amino acids. (meaning the origins of life occurred in a tumultuous abiotic environment

Relationship between Oparin-Haldane and Miller-Urey

Oparin-Haldane is the hypothesis; Miller-Urey is the experimental test of that hypothesis.

RNA World Hypothesis

Proposal that RNA preceded DNA/proteins because RNA stores genetic information and catalyzes reactions.

Ribozyme

An RNA molecule with enzymatic or catalytic activity, some can bind and cleave mRNA to prevent it from functioning (ex: splicing, gene expression)

Why is DNA alone insufficient as the first biological system?

DNA stores and transmits information, but cannot independently perform catalytic biological work.

Why are proteins alone insufficient as the first biological system?

Proteins perform biological work, but cannot propagate themselves or store hereditary information.

Why is RNA a strong candidate for an early biological molecule?

RNA can store, transmit, and express genetic information, and catalyze chemical reactions.

Evidence supporting RNA World

Ribosomes use an RNA framework, RNA functions in protein synthesis, and RNA can evolve.

Major problem with RNA World

RNA is highly unstable, and robust self-replicating (breaks down in seconds). RNA has not been demonstrated/discovered naturally.

LUCA

Last Universal Common Ancestor — the ancient common ancestral form from which all current life descended.

Approximate timing of LUCA in the lecture

About 3.5 BYA. The slides contrast this with the proposed appearance of self-replicating systems around 4.1 BYA.

Evidence for LUCA

No specific LUCA fossil is known; evidence comes from the remarkable molecular unity shared by all living organisms.

Features shared by all life

Shared genetic material (DNA, mRNA, tRNA), the same genetic code (A, C, G, T), shared gene-expression processes (transcription and translation), common molecular building blocks (proteins made of 20 amino acids), and ribosomes.

Why does molecular unity support common ancestry?

The fact that all modern organisms use fundamentally similar information-storage and expression systems strongly suggests they inherited those systems from a common ancestor.

Likely characteristics of LUCA

T likely an anaerobic thermophile, living in an iron-sulfur-rich environment, perhaps a hydrothermal vent, and not dependent on other organisms.

Anaerobic

Able to live/function without oxygen.

Thermophile

An organism adapted to high-temperature environments.

Why use molecular data for deep evolutionary relationships?

its generally FAR better than morphology for reconstructing extremely ancient relationships because researchers can compare highly conserved genes shared by all organisms.

Conserved gene

A gene that has changed relatively little through evolutionary time; for deep phylogeny, it should occur in all organisms and retain the same basic function.

SSU rRNA

Small-subunit ribosomal RNA, a hallmark highly conserved sequence used to reconstruct deep evolutionary relationships among organisms. one of the most important genes used to build phylogenetic genes

Why can different genes produce different phylogenetic trees?

Each gene has its own evolutionary history because processes such as recombination (!) and horizontal/lateral (!) gene transfer can affect genes differently.

Whole-genome evidence for the three domains

whole-genome approaches tend to support Archaea and Eukarya as sister taxa.

Horizontal gene transfer (HGT)

Movement of genetic material between organisms/lineages other than traditional parent-to-offspring inheritance; it can give individual genes evolutionary histories different from the organism as a whole.

LUCA vs. LUCAs/community model

the earliest universal ancestor may not have been one isolated organism; a more accurate picture may be a community of interacting species that frequently exchanged genes through HGT.

for deep reconstruction, genes must be:

present in all organisms and functions must have remained the same for all organisms

Age of Earth

Approximately 4.6 billion years old.

Igneous rock

Rock formed when molten material cools and solidifies (ex: lava)

Sedimentary rock

Rock formed by deposition and solidification of sediments, typically accumulating in layers.

Metamorphic rock

Existing igneous or sedimentary rock transformed by high pressure and/or temperature.

Which rock type is most associated with fossils?

Sedimentary rock, because sediments accumulate in layers and can bury/preserve remains; intense heat associated with other processes can damage biological remains.

Relative dating

Determines whether something is older or younger relative to something else; it does not provide a numerical age. (determined based on relationships, spatial proximity, or sequence)

Stratigraphy

Study/use of the relative position of rock strata to infer geological sequence and relative ages.

Principle of Superposition

In an undisturbed sequence, layers can be classified as older or younger relative to layers above/below them; generally older layers are beneath younger layers. (closer to the surface are younger)

Original Horizontality

Sedimentary rocks were originally deposited in flat horizontal layers; later geological processes can tilt or fold them.

Cross-Cutting Relationships

A geological feature that cuts across another rock layer is younger than the rock it cuts. Example: a dike or sill is younger than the surrounding rocks it crosses.

Absolute dating

Dating methods that can infer an actual/numerical age, rather than simply older vs. younger.

Radioisotope

An unstable isotope that undergoes radioactive decay; radiometric dating uses predictable radioactive decay to infer age. emit P, N, E. often use half life

Radiometric dating

Absolute dating technique that uses unstable radioactive isotopes and their decay products

Parent isotope

The original radioactive isotope that undergoes decay.

Daughter isotope

The product formed as the parent radioactive isotope decays.

Half-life

Amount of time required for 50% of a parent isotope to decay into its daughter isotope.

Half-life pattern

Start: 100% parent → 1 half-life: 50% → 2: 25% → 3: 12.5% → 4: 6.25%.

Carbon-14 dating

C-14 decays to N-14 with a half-life of approximately 5,700 years in the slides. The C-14:C-12 relationship can estimate time since death.

Useful range of carbon dating

According to the lecture, carbon dating works best for organisms younger than about 60,000 years.

Dating objects older than carbon dating's range

heavier isotope systems, including uranium → lead and other elements, can be used for older materials.

Dendrochronology

Biological dating using tree rings; each annual ring corresponds to one year and can be used to infer age and environmental conditions.

Tree ring interpretation — wide ring

Indicates a relatively good/long growing season.

Tree ring interpretation — narrow ring

Indicates a relatively poor/short growing season.

Tree ring scars/damage

Abnormal growth or scarring can reveal past disturbances such as fire or physical damage.

Plate tectonics (Continental drift)

Earth's outer layer consists of moving plates; their movement changes the arrangement of continents and helps explain geographical/fossil patterns through time. very small changes over time = big difference

Alfred Wegener

Proposed continental drift in 1915; observed that continents appeared to fit together and noted matching fossils on continents now separated by oceans.

Evidence Wegener used for continental drift

Geographic fit of continents and occurrence of similar fossils in South America and Africa, suggesting those continents were once connected.

Divergent plate boundary

Plates move apart; can produce new ocean floor, such as processes occurring in the Atlantic.

Convergent plate boundary

Plates move toward each other; can produce mountain ranges such as the Himalayas.

Transform fault boundary

Plates grind past one another; earthquakes are common, with California given as an example.

Why does plate tectonics matter to evolutionary history?

It explains why similar organisms/fossils occur in corresponding strata on continents now far apart and provides geographic evidence supporting evolutionary interpretations of the fossil record.

Great Basin Bristlecone Pines

Oldest known non-clonal species on the planet w/ never-seen before versatility