Organic Evolution Exam 1

Charles Darwin

Natural Selection - differences in phenotypes in certain individuals can improve survivability and reproductive success.

HMS Beagle - gathered fossils of extinct animals, trapped birds and collected barnacles,

Homology

structural characters that are shared because they are inherited from a common ancestor

Types of Living Cetacean Mouth Anatomy

Mysticetes - use baleen to filter small animals from water (blue whale)

Odontocetes - toothed whales (sperm whales, dolphins, orca)

Philip Gingerich

discovered Pakicetus -

• Fossil was 50 million years old - oldest cetacean fossil at that point

• Pakicetus lived in shallow streams and appeared to have spent some time on land

Morphology

form and structure of organisms

Genera

taxonomic group that includes species

Genetic Drift

evolution arising from random changes in the genetic composition from one generation to the next

Evolutionary Change

can modify morphological, behavioral, and physiological features

Evolution

explains the diversity of life

Biological Evolution

any change in the inherited traits of a population that occurs from one generation to the next

Shared Traits of Whales to Mammals

Live birth

Mammary glands

Three middle ear bones

Dorudon

Transitional fossil that reveals whales’ link to land mammals

Baleen whales (mysticetes)

Ancestors of all modern whales had teeth

• Baleen completely replaced teeth in mysticetes (genes for teeth building disabled)

Evolution of Large Brains

Caused by sociality

• formation of lasting alliances

• competition for mates

• complex communication

Evidence for Understanding Evolution

Fossils

Comparative Anatomy - studying homologous structures, vestigial structures, etc.

Genetic Evidence - DNA, RNA, protein sequence comparison

The Great Chain of Being

Christians’ view of the cosmos - divine plan established by God at creation

Became known as “Natural Theology”.

Carolus Linnaeus

Linnaean Classification

• organized all living things into hierarchy groups = TAXA

  • Taxonomy - science of describing, naming, and classifying species of living or fossil organisms

Nicolaus Steno

Studied shark teeth - found that after death, teeth became stone

• Idea: life and the planet that supported it had a history filled with change, and Earth itself kept a record of that history.

William Paley

wrote Natural Theology, or Evidences of the Existence and Attributes of the Deity Collected from the Appearances of Nature

• proposed intricate design of life is evidence of a Divine Creator

• cataloged examples of organs and their similarities to man-made machines

“If you see a rock, it’s natural. If you see a clock, there is a creator.”

Buffon

• earth formed according to laws of physics & chemistry

• Earth was older than previously thought

• Life emerged @ distinct types; transformed when environment changed

• Proposed varieties of species arise in response to new habitats

Mary Anning

Paleontologist - found fossils of reptiles (sharklike species & winged flying forms)

• Helped provide evidence for concept of extinction

Lamarck

Believed animals and plants could adapt to their environment

• believed physical changes acquired by organism can be passed down to offspring

  • Example: amputated limb can be passed to offspring

• Complex species descended from microbes

  • Microbes are continually generated

• Opposed “Great Chain of Being”

Georges Cuvier

compared elephant fossils to living elephant from Africa and India

• discovered distinctions (mammoths)

  • concept of extinction

• anti-evolutionist

Uniformitarianism

Natural laws observable now are responsible for events in the past

• Popularized by Hutton & Lyell

  • Earth’s landscapes had been created not by gigantic catastrophes but by a series of many small changes

Ingredients for Natural Selection

1. All species have great potential fertility that population would increase exponentially if all were born successfully

2. Except for minor fluctuations, population will display stability in size

3. Natural resources are limited.

Inference 1: Because more individuals are produced than can be supported by the limited resources, resulting in only a small part of population to survive

4. No two individuals are the same. Every population displays variability.

5. Much of the variability is heritable.

Inference 2: Survival in the struggle is not random but depends on inherited traits. Unequal survival = natural selection

Inference 3: Process of natural selection will lead to continuing gradual change in populations = evolution and new species production

Lyell

Believed Earth’s geological features were caused by gradual changes

• Influenced Darwin

Heredity

Transmission of characteristics from parent to offspring

Hutton

small changes can dramatically change landscapes

• earth must be very old

Linnaean Taxonomy

Kingdon

Phylum

Class

Order

Family

Genus

Species

William Smith

Discovered different rock layers contain distinct groups of fossils

• Created first geological map

The “Modern Evolutionary Synthesis”

Made evolutionary theory more powerful, blending genetics and other fields with natural selection

Most evolutionary biologists agree that natural selection is the most important driving force in evolutionary change. However, there are other mechanisms, such as sexual selection and genetic drift. In all mechanisms, the most important common denominator of evolutionary change is:

Reproductive success

Which statement is NOT a central tenet in Darwin/Wallace theory of natural selection

variations in populations emerge through mutations

Abigail Allwood

found fossils of microbes

• dating back 3.43 billion years

• built a rover to look for signs of life on Mars

Kelvin

argued w/ Darwin that Earth is only hundreds of thousands of years

• used temperature of rocks in mine shafts

• wrong because earth is not a rigid sphere - it is dynamic

Half-Life

N = N_oe^(-λt)

• N = # of unstable atoms that remain from original supply

• λ = probability of atom decaying in a given time

Half-Lives

• Carbon-14 → Nitrogen-14: 5730 years

• All atoms of half lives found are more than 80 million years

Radiometric Dating

allows researchers to estimate precise ages at which one geological formation ends and another begins

• unstable isotopes have fixed probabilities of decaying into a more stable form

• unstable → stable

• stability depends on neutron

• ¹⁴C (unstable) → ¹⁴N (stable)

• isotopes with higher probability of decaying do so more quickly

• can be used as “clocks” to provide absolute age

• Rubidium⁸⁷ → Strontium⁸⁷ = 48.8 billion years (half-life)

Geological Periods (youngest → oldest)

Cenozoic (66mya - present)

Mesozoic (251.9 - 66 mya)

Paleozoic (541 - 251.9 mya)

Protezoic (neo-,meso-, paleo-) - (2500 - 541 mya)

Archaean (4000 - 2500 mya)

Hadean (4600 - 4000 mya)

Hominin

member of the clade that includes humans as well

• also, all species closer to humans than chimpanzees

• Only humans are still alive

Lagerstätte

site with an abundant supply of unusually well-preserved fossils - often including soft tissues - from the same period of time

Transition to multicellular life

• began at least 2.1 billion years ago

• evolved independently across multiple lineages

Example: slime mold can aggregate and form stalks for reproduction

Mobility

Elizabeth Turner - found sponge fossils

Ediacaran fauna - animal species found in Ediacaran period (before Cambrian)

Chordates

diverse phylum of animals that includes the vertebrates, lancelets, and tunicates

ALL HAVE:

• notochord

• pharyngeal gill slits

• post-anal tail

Tetrapod

vertebrate with four limbs

Living tetrapods include:

• mammals

• reptiles

• birds

• amphibians

Teleosts

Bony fishes that comprises most of today’s living aquatic vertebrate

Distinguished by:

• upper jawbone mobility = premaxilla

Synapsids

Lineage of tetrapods that gave rise to mammals

• 320 million years ago

• distinguished by a pair of openings behind eyes = temporal fenestrae

• nostril opening

Earliest Detections

• Oldest chemical traces: 4.1 billion years old

• Stromatolites & other microbes: 3.4 billion years

• Multicellular organisms: 1.6 billion years

• Biomarkers of animals: 650 million years

• Plant fossils: 475 million years

• Oldest known animals that looked similar to living animals: 200 million years

• Our own species: 300,000 years

• Tracks of terrestrial animals: 480 years

Cambrian Period

lasted 540 millions years

CT Scan

determined function of hadrosaur crest

• crest connected to nasal cavity (sound generated by blowing air)

  • found ears were tuned to specific frequency

Burgess Shale

Occasionally soft tissues fossilize

• Landslide will cover previous layes

• example of lagerstätte

• 505 mya

• more than 65,000 specimens

Dawn of Animals

Animals = hetetroph, Plant = autotroph

Early animal life resemble sponge

• oldest fossils dated @ 890 mya

• biomarkers of sponges dating to 635 mya

Earliest animal tracks

• 585mya

• tells us animal gain mobility, instead of being sedentary

Ediacaran fauna

fauna = animals

• dominated oceans from 570-540 mya

  • many went extinct at the end of Ediacaran period

Cambrian fauna

Animals diversified → some grazed on microbial mats, others predator-prey

• 541 mya - 485 mya

Chordates

• 515 mya

• predecessors of vertebrates (NOT ALL HAVE VERTEBRAL COLUMN)

  • All had: notochord, pharyngeal gill slit, post-anal tail

Terrestrial Plant and Fungal Life

Oldest terrestrial plant fossils → ~470 mya

Large forest ecosystems within 100 million years

First Terrestrial Animal Life

Invertebrate trackways → 480 mya

• Probably relatives of insects and spiders

• not clear whether they lived on land permanently

• Oldest fossil: 428 mya

  • Many were millipedes

First Terrestrial Vertebrates

Oldest trackways → 390 mya

Oldest fossils of tetrapods → 370 mya

• showed how they walked

Present Forms of Life Emerged:

Teleost fish → 240 mya

Mammals → 200 mya

Birds → 136 mya

Flowering Plants → 136 mya

Insects → 400 mya

Dinosaurs → 240 mya

The lineage of vertebrates that gave rise to mammals were

Synapsids

Phylogeny

The evolutionary history of a lineage or lineages (populations, genes, or species)

Phylogenetic Tree

visual representation of a phylogeny

• shows evolution over time

Reading a Phylogenetic Tree

Nodes: represent common ancestors for all descendent lineages

Clades: a common ancestor and all of its descendants

Taxa: named groups of organisms

Taxonomic Units

Monophyly: same clade

Polyphyly: multiple organisms from different clades

Paraphyly: multiple organisms (some from same clade, others from different clade)

Synamorphy

derived character state shared by an ancestor and its descendantsO

Outgroup

used to infer approximate ancestral character states

• when making tree, make sure all matrices are 0

Homoplasy

Character state similarity NOT due to common descent

• Arose multiple times

• Convergent evolution: independent evolution of similar traits in separate lineages

  • EX: streamlined body of dolphins and fish

• Evolutionary Reversal: reversion back to ancestral character state

  • EX: fish that lost their eyes because they live somewhere w/o light and eyes weren’t beneficial

Fins to Limbs: Homology Through Time

Coelacanths are one of the closest living relatives of tetrapods

• have fins homologous with tetrapod forelimbs → lobe-fin

  • derives ulna, tibia, etc.

Neil Shubin

Predicted where transitional fossils would be found

• Mid-Devonian rocks in Northern Canada

Tiktaalik

Transitional fossil

• Between fish and tetrapods

• forelimbs share more homologies with tetrapods than Eusthenopteron

Mammalian Ear Bones

Homologous to bones of reptilian jaw

• bones shrunk and detached → adapted to detect airborne sound

Feathers Evolved Before Flight

• Nest protection

• Mating

• Species Recognition

Exaptation: natural selection co-opts a trait for a new function

• trait was already there & gained a function

  • Feathers = protection → flight

What do phylogenetic trees represent?

evolution over time

Which statement about a node of a phylogenetic tree is correct?

A node represents the point at which a lineage splits

What is the main difference between a paraphyletic group and a polyphyletic group?

Paraphyletic Group: does NOT include all the descendants of a common ancestor

Polyphyletic Group: do not share an immediate common ancestor

What are characters in relation to phylogenetic trees?

Heritable aspects of organisms that can be compared across taxa

Polytomy occurs when:

an internal node of a phylogeny has more than two branches

• therefore, the order in which the branchings occurred is NOT resolved

  • we don’t know which branch is more closely related

Tiktaalik is a transitional fossil. What does that mean?

Tiktaalik shares some characters states with tetrapods and some with lungfishes and coelacanths.

Synapomorphy

shared traits or characteristics that two or more species inherit from a recent common ancestor

Thomas Maltus

Human population size is limited by resources