Unit 1

6th Mass Extinction

(Holocene, Anthropocene Extinction) -currently experiencing the worst spate of species die-offs since the loss of the dinosaurs 65 mya -cause is rising human population & Humans= Global Superpredators (overhunting and overutilization) *animals populations have decreased by 80% since 1900 Previously all (100%) of vertebrates =wildlife Land Animals now: 3% = wildlife 97% = humans, pets, livestock

Sexual selection

*a special case of natural selection -directed at certain traits of sexually reproducing species that make it more likely for individuals to find or choose a mate and/or engage in successful mating -in many species, male characteristics affected more intensely than female (secondary sex characteristics, sexual dimorphism (pronounced dif btwn males & females): often better for females to be duller so they can survive and take care of offspring Intrasexual: same sex - males directly compete for mating opportunities or territories -ex) 2 male elk Intersexual: opposite sex - females choose w/ males possessing a particular phenotype ex) lizards w/ red vocal sacs, peacocks w/ best dance & show of feathers

Dinosaurs diagram

*aquatic, terrestrial and avian dinosaurs -turtles, crocodiles, alligators are reptiles that survived the K-T extinction (ancient reptilian groups) -birds survived as well and are only direct descendent of dinosaurs alive today -these different dinosaurs that we know today didn't all live at the same time as some media shows

Scientific Names

*can give clues about certain traits *specific names can pay homage to people *can be very unique

Structure determines function

*complementarity of structure and function Biological structures come about as a species adapt to its environment Function: the human hand can grasp things (fine control) and grab objects (power) Structure to function relationship: opposable thumb (fine control), touching the hands to the base of the hand and to wrap the thumb on top makes the power grip possible Function: flight Structure to function: between each of the bat's fingers there's a flat, thin, flap of skin, the skin provides lift as the bat flaps its wings allowing it to fly Ex) protein folding determines protein function

Adaptive radiation

*extreme example of allopatric speciation -when members of a species invade several new geographically separate environments (niches), reduced competition and more resources -often follows mass extinction -the populations become adapted to the dif environments -many new species evolve from the single ancestral species ex) Hawaiian honeycreepers: Hawaii is the most geographically isolated of all islands, lots of endemic species, the honeycreeper (Eurasian rosefinch) arrived in Hawaii 3-7 mya, founder effect (54 dif species, many now extinct) ex) Darwin's finches: 1 common ancestor --> 13 species ex) Australian marsupials (originated in Africa): 1 common ancestor --> 200 species (weren't experiencing competition from placental mammals) *isolated ecosystems and physical isolation often leads to adaptive radiation

Genetic Homologies

*generally look at highly conserved genes (important function) Cytochrome c: -respiratory protein on cristae of mitochondria that plays a role in the ETS for ATP production and apoptosis) -100 a.a. long -highly conserved --> human and chimpanzee identical, chicken and turkey identical (differ from duck by 1), human and chicken differ by 13 Short amino acid sequence in p53 protein (important protein in cell cycle): -monkeys are 95% identical to humans -fish are approx.50% identical to humans but very similar to each other

Primates on the brink

*great apes, gorillas, chimpanzees, bonobos 1) Grauer's Gorilla (largest gorilla) 2) Aye-Aye (people kill them bc they think they have bad omen) 3) Northern Sportive Lemur (climate change and political upheaval in Madagascar has impacted them) 4) Pygmy Tarsier (4 in the wild) 5) Rondo dwarf galago (trafficked) 6) Slow loris (5 species in Indonesia: people sell them on black market or for medicine, have to pull out teeth bc they are 1 of 2 mammals that delivers a toxic bite) *25 species of monkeys, lemurs, etc. on brink of extinction: deforestation and trafficking *since 2000 we have found 79 new primate species

Extraterrestrial hypothesis

*monomers coming from outer space -organic carbon from asteroids and comets stocked prebiotic soup (could have brought bacteria, organic molecules) -Meteorite studies: carabonaceous chondrites lots of organic carbon, a.a's, nucleic acid bases -Controversy: would the materials have survived the intense heat of impact?

Modes of speciation: sympatric speciation

*more for plants and insects -one population develops into 2 or more reproductively isolated groups -no prior geographic isolation (no physical barriers to interbreeding) Autoploidy (nondisjunction of chromosomes): 2n plant --> 2n gametes (+n) = triploid (sterile, seedless) Alloploidy: tetraploid hybridization in plants -results in self-fertile species -reproductively isolated from either parental species *look at diagram

Fossil dating

*only concrete evidence of the past is fossils Fossils=remains and traces of past life Paleontology- the study of the fossil record Most fossils are traces of organisms embedded in sediments -sediment converted to rock -becomes recognizable layers (stratum) in stratigraphic sequence of rocks -strata (a layer) of the same age tend to contain the similar fossil assemblages -helps geologists determine relative dates of embedded fossils despite upheavals

Classification of living things

-1.75 million species described -10-100 million exist! *considers both living and fossil forms

Cambrian Explosion (Period)

-540 million yrs ago -tremendous diversification of animal life during this time -warm, wet climate, O2, no ice at poles -all existent phyla developed (could have more ancient origins) -no major reorganizations of body plans since (all animal phyla have representation in the organisms present in the Cambrian period) -many marine inverts with shells -first vertebrates - 520 mya *good evidence of multicellular life High diversity of the Cambrian may be due to: -favorable environment (in the water)- oxygen (crossed oxygen threshold) : animals could move from anaerobic--> aerobic -evolution of Hox genes: establish the patterning to animals bodies -predator/prey "Arms Race" - shells, reef-building -new ocean chemistry (ability to sequester calcium and oxygen to make calcium carbonate for shells)

Biogeography

-Alfred Russel Wallace- father of biogeography -study of geographical distributions of plants and animals across earth -consistent with origin in one locale and then spread to accessible regions -different mixes of plants and animals in areas separated by water, continents, islands ex) distribution of marsupials (consistent with continental drift, 2.5 cm or 1 inch a year)

Charles Lyell & Hutton

-Earth is subject to slow but continuous cycles of erosion and uplift (Earth is molded by slow, constant change from wind, water, weather, etc.) -proposed Uniformitarianism: rates and processes of change are constant -Principles of Geology *extended the age of the Earth to 4 bya instead of the supposed 4,000 years ago

Primate evolution cont.

-Lemurs, tarsiers, monkeys, apes, humans -descended from tree-dwellers (arborial) All adapted for climbing trees 1) rotating shoulder joint 2) big toe and thumb widely separated from other (true for all primates except humans) 3) stereoscopic vision (allows overlapping fields of vision, depth perception- gauge distances) Also: larger brain, 1 offspring/pregnancy, upright body, claws --> nails Humans (Homo: genus): bipedalism (2 feet), incr brain size, fully opposable thumb Ancestral: Australopithicus, H. habilis, H. erectus Non-ancestral cousins: Neanderthals, Denisovans *review chart in notes

Living Planet Report 2020

-average 68% decline in monitored populations (21,000 pops) of mammals, birds, amphibians, reptiles and fish (verts only) -most significant decline in tropical subregions of the Americas (94%) and Africa (65%) -freshwater biodiversity declining faster than terrestrial or oceanic -megafauna (large size) particularly vulnerable : have changed ecosystem by removing top carnivores (sharks, lions, tigers, etc.) -plant extinction risk is comparable to that of mammals and higher for birds - >1/5 of wild species are at risk of extinction this century due to climate change alone *most startling decline in corals (bc of sea level rising) and cycads (plants, gymosperms)

Characteristics of living organisms: Energy use and metabolism (evan)

-energy required to maintain order (meet energy requirements) -energy utilized via Metabolism -photosynthesis (supports food web), cellular respiration, ATP

Lamarck

-first biologist to propose evolution and link diversity with environmental adaptation -concluded more complex organisms are descended form less complex organisms (striving for perfection) -proposed inheritance of acquired characteristics: Lamarckianism (first proposed mechanisms of evolution) *epigenetic changes that influence genome ex) giraffes acquired long neck by continuously reaching for trees

Characteristics of living organisms: growth, development, and reproduction (grow)

-growth produces more or larger cells, mitosis -development produces organism w/ defined set of characteristics according to genetic program -reproduction sustains species over generations (meiosis, gametes --> zygote) -genetic material causes offspring to have traits like their parents (DNA as material of heredity)

Triassic Period

-gymnosperms dominant, conifer forests -reptiles abundant (1st dinosaurs appeared) - survived Permian extinction bc of adaptations -1st true mammals (synapsids: tiny hair covered shru-like animals that lived at feet of dinosaurs)

Directional Selection

-individuals at one extreme of a phenotypic range have greater reproductive success in a particular environment -curve shifts in that direction Examples: -Size of modern horse (started off as small and forest dwellers and the larger size was favored) -Industrial/Adaptive Melanism -DDT-resistant mosquitoes -Antibiotic-resistant bacteria

Stabilizing selection

-intermediate phenotype is favored -the peak of the curve increases and tails decrease ex) human babies w/ low or high birth weight are less likely to survive (typical is between 7-10 lbs) ex) clutch size of birds (4 to 5 eggs is optimal)

Deep-sea vent hypothesis- 1988

-key organics arose at deep-sea vents -superheated water (300 F) rich in H2S and metal ions mixes w/ cold seawater leading to formation of organics -organics formed in temperature gradients around vents *deep-sea vents are active areas of crust formation from sea-floor spreading, lots of heat (in environment of ocean ridges) *at deep-sea vents there are very complex communities of life (rely on chemo-synthesis) and similar organisms are found at different vents (even though they are far apart from each other) *worms called riftia are bright red bc of hemoglobin and rely on chemosynthetic bacteria

Balancing selection

-maintains genetic diversity Balanced polymorphism: -two or more alleles are kept in balance, and maintained in a population over the course of many generation (regardless of whether the gene selected for is beneficial or harmful) -two common ways 1. For a single gene, heterozygote favored -heterozygote advantage: Hb^s allele -works to keep both dominant and recessive in population ex) sickle cell anemia w/ malaria & cystic fibrosis w/ cholera, typhoid, tuberculosis 2. Negative frequency-dependent selection -rare individuals have a higher fitness (Predator-Prey) -disguised from normal, predator learns general form of animal (most common)

Characteristics of living organisms: Cells and organization (can)

-organisms maintain internal order (cells are the smallest structural and functional unit of life) -chemical uniqueness -hierarchy of organization (cells--> tissues--> organs--> systems--> species--> populations) *emergent properties

Characteristics of living organisms: Response to environmental change (respond)

-organisms react to stimulus, ex: cellular communication at membrane -adaptations/behaviors promote survival *organisms respond to stimuli (adaptations)

Characteristics of living organisms: regulation and homeostasis (regulate)

-organisms regulate cells and bodies (blood glucose, body temp) -maintain relative stable internal conditions *disease= inability to maintain homeostasis

Characteristics of living organisms: biological evolution (evolve)

-populations of organisms change over generations -evolution results in traits that promote survival and reproductive success *gives us an explanation of where species come from

Classification categories cont.

-the higher the category, the more inclusive -organisms in the same domain have general characteristics in common -in most cases, classification categories can be subdivided into additional categories particular w/ insects, birds (superorder, suborder, infraorder) Distinguishing species on the basis of structure can be difficult: -members of the same species can vary in structure -attempts to demonstrate reproductive isolation is problematic because: some species hybridize (2 species crossbreeding) and reproductive isolation is difficult to observe (hard to catch species breeding and see it through the fossil record)

Causes of Microevolution (Genetic Mutations)

-the raw material for evolutionary change (source of genetic variability, underlie all of it) -source of new alleles; new combinations of alleles (source on which other evolutionary forces can act) -not goal-directed; not a result of environmental necessity (occurred before the necessity- not induced by environment) -random events: depending on environmental conditions (good: adaptations, bad, neutral) -other forces act to either maintain the variation or remove it from the population *biggest cause of microevolution

Modes of speciation: allopatric speciation

-two geographically isolated populations of 1 species (natural, physical barrier) -become dif species over time - gene flow interrupted -can be due to differing selection pressures in differing environments --> leading to reproductive barriers *Disperal (members move) vs. Vicariance (natural divide) ex) Kaibab squirrel became isolated from the Abert squirrel on opposite sides of the grand canyon, developing dif belly colors and forelimbs (subspecies: separated by geography) ex) porkfish were separated from one another when Panama divided the pacific ocean from the caribbean sea --> speciation --> panamic porkfish & atlantic porkfish

Disruptive (diversifying) selection

-two or more extreme phenotypes are favored over intermediates; biomodal distribution ex) Cepaea snails vary because a wide geographic range causes selection to vary (some yellow w/ thin brown stripes, others all brown) *may be a force over time that can lead to speciation if a reproductive barrier comes into place

Relative dating

-use index fossils -looks at specimen through various layers -layers can be disturbed by tectonic displacement (volcanoes and earthquakes) Good index fossils: -need to have a wide distribution -have lots of them -belong to groups that evolve rapidly -easy to recognize

Molecular clocks

-use non adaptive nucleotide sequences (proteins that are highly conserved, very important, not subject to adaptations) -assumed constant rate of (neutral) mutations over time *favorable mutations are rare *detrimental mutations are quickly eliminated *so must mutations are neutral (within genome no consequence) mtDNA (mitochondrial, cytochrome c) - 2% nucleotide changes/1 million yrs -crucial for aerobic (ATP), specifies proteins in mitochondria -trace maternal lineage SSU (18S) rRNA- 1% sequence change/ 50 million yrs -all organisms have ribosomes that function very similarly in protein synthesis

Ordovician Period

-warm temperature and atmosphere very moist, lots of CO2 in atmosphere -land was present in supercontinent -diverse marine invertebrates including trilobites (ancient arthropods, 3 part body), brachiopods (lamp shells), bryozoans *earliest vertebrates were starting to diversify -primitive plants and arthropods first invade land (spiders and centipedes) -at end, abrupt climate change (large glaciers) resulted in mass extinction (60% marine inverts) *algae, primitive fish, primitive econodorms, mollusks

Process of evolution

1. Variations are produced by chance mutations and sexual reproduction (crossing over, independent assortment, fertilization) 2. Natural selection selects the "fittest" organisms - organisms that survive and reproduce 3. Natural selection leads to adaptation to a particular environment (only mechanism of evolution that leads to adaptations) 4. Process occurs constantly in all species of life on earth (humans included)

How did life begin?

13-17 bya: Big Bang formed the universe 4.6 bya: our solar system formed 4.55 bya: earth formed 4 bya: earth had cooled enough for outer layers to solidify and oceans to form (water exists in all 3 phases in our biosphere) 4-3.5 bya: life emerged (where biology starts) *life requires interplay between DNA, RNA, and proteins (central dogma of molecular biology: DNA--> RNA--> proteins) *living cells come from pre-existing cells (cell division-mitosis, cell theory) 4 overlapping stages: 1) Nucleotides and a.a.'s produced prior to existence of cells 2) Nucleotides and a.a.'s become polymerized to form DNA, RNA, and proteins 3) Polymers became enclosed in membranes 4) Polymers enclosed in membranes evolved cellular properties (life takes off from that point) *evolutionary theory relies on modifying existing forms, can't explain why life started

Darwin and Origin of Species

1836- returned to England 1838- read work by Rev. Thomas Malthus (political economist): Essay on the Principle of Population- Struggle for Existence for poor -each generation has the same reproductive potential as the previous generation -reproductive potential is greater than environment can support -death, disease, and famine were inevitable if population is to have stability 1839- published journal Voyage of the Beagle 1844- long essay on "Origin of Species" 1856- began work on book (spent lots of time thinking, writing and amassing evidence to have scientific credibility to combat the anticipated skepticism) 1858- read manuscript by Alfred Russell Wallace (had similar ideas, father of biogeography, studied butterflies), both presented at meeting at Linnean Society 1859- On Origin of Species by Means of Natural Selection

Hardy-Weinberg Principle

1908 - G.H Hardy (English mathematician) and W. Weinberg (German physician) independently recognized: -genes remain in equilibrium (constant frequency) over time (in each succeeding generation of a sexually reproducing population) as long as 5 conditions are met *relates allele and genotype frequencies in a population Equation: p + q = 1 p^2 + 2pq + q^2 = 1 (expansion)

Permian Period

290-248 mya -continental drift formed supercontinent Pangaea -interior regions dry with seasonal fluctuations -forest shift to gymnosperms (conifers) -amphibians prevalent BUT reptiles became dominant (weren't tied to water, had scales and stronger skeletal system) -first mammal-like reptiles appeared (maintain constant body temp) -at the end, largest known mass extinction event

Jurassic Period

54 million year chunk -dinosaurs achieved enormous size -mammals remained small and insignificant -plant matter was abundant -1st bird evolved from dinosaur ancestors -break-up of supercontinent from northern to southern

Cretaceous Period

80 million year span (145-65 mya) -dinosaurs began precipitous decline (K-T extinction: meteorite + volcanism hit the Earth at Yucatan peninsula) -continental drift also -Mammals: began an adaptive radiation, moved into habitats left vacated by dinosaurs (could maintain constant body temp, reptiles are ectotherms and rely on outside sources of heat) -ash/soot/dust blocking sun --> kills plant life --> kills herbivores --> kills carnivores

Natural Selection

Adaptation of a population to the biotic and abiotic environment -Abiotic: climate, water availability, minerals -Biotic: competition, predation, sexual selection Requires: -Variation: the members of a population differ from one another -Inheritance: many differences are heritable genetic differences -Differential adaptiveness: some differences affect survivability (all features are not equally adaptive) -Differential reproduction: some differences affect likelihood of successful reproduction *cost-benefit analysis taking place (organisms aren't perfectly adapted) Results in: -a change in allele frequencies in the gene pool -improved fitness of the population *Major cause of microevolution (constant dominant force of evolution)

Genetic Drift- Bottleneck effect

African Cheetah: -fastest living land animal (70-75 mph) -lost nearly all genetic variability (monomorphic for almost all genes: 96%r of alleles are the same from 1 cheetah to the next) -prolonged inbreeding following a bottleneck (10,000-12,000 yrs ago): only a few individuals made it to reproduce, caused by disease, hunting -very low sperm count, motility, and deformed flagella Northern Elephant Seals: -low genetic variability -human inflicted (1890s) -hunted to 20 individuals -now 100,000 -may be susceptible to pollution/disease because they are so genetically similar w/ little genetic variability *whatever genes you happen to have, passes on

Carboniferous Period

Age of Amphibians -rich coal deposits formed and deposits of natural gas by dead plant matter (most of natural resources we use today came from this: coal, oil, natural gas) -cooler w/ land covered by forested swamps Plants and animals further diversified: -very large plants and trees prevalent, conifer forests -first flying insects (only invertebrates that can fly, allowed to move into new habitats) -Amphibians prevalent (water --> land, reorganization of body systems which was important for vertebrate life, tied to water by reproduction, earliest Tetrapods) -Amniotic egg emerges - reptiles (freed animals dependence on water for reproduction)

Cenozoic Era

Age of Mammals 64 mya through today: Paleogene, Neogene (Tertiary) Quaternary Periods--> where we are now -tropical conditions replaced by colder, drier climate (animals w/ constant body temp have advantage & diversify) -mammals continued adaptive radiation (birds, fishes, insects diversified) *birds (covered by feathers and metabolism) and mammals are only vert. to maintain constant body temp -flowering plants already diverse and plentiful (lots of coevolution) -birds and mammals are only vertebrates to maintain constant body temp -earth was characterized by 4 major ice ages: mammoths, ground sloths, etc.

Mesozoic Era

Age of Reptiles -consistently hot climate, dry terrestrial environments, little if any ice at poles -248-65 mya -Triassic, Jurassic, Cretaceous periods

Comparative development

All vertebrate embryos have: -a postanal tail (in humans becomes coccyx) -paired pharyngeal (gill) pouches (becomes a respiratory structure, eustacian tube in humans that equalizes pressure in ear drums) -dorsal, hollow nerve cord (spinal cord) -notocord (becomes vertebral column) "Ontogeny (developmental sequence of organisms) SOMETIMES recapitulates phylogeny (evolutionary history of animals) *organisms developmental sequences can tell us about evolutionary relationships *look at chart

Convergent evolution

Analogy- similarity due to convergence ex) Jumping: function/feature (kangaroo, springhare, snowshoe hare, grasshopper, jerboa, bullfrog: all with large hindlimb for jumping) *not closely related *interactions in dif environments were similar

Factors that affect the fossil record

And Sally Never Even Told George Possibly Anatomy: organisms w/ hardy body parts (skeleton or thick shell) are more likely to be preserved than organisms composed of soft tissues (require precise conditions to fossilize) Size: the fossil remains of larger organisms are more likely to be found than smaller organisms Number: species that existed in greater numbers or over a larger area are more likely to be found Environment: inland species are less likely to become fossilized than those in a marine environment or near the water because sedimentary rock is more likely to be formed in or near water (continent's edges) Time: species that lived relatively recently or existed for long periods of time are more likely to be found Geological processes: due to chemistry of fossilization, certain organisms are more likely to be preserved than other organisms (type of rock, environmental conditions, inland vs. coastal) Paleontology: certain types of fossils may be more interesting to paleontologists, bias with regards to where they search for fossils (tend to search in regions where other fossils have been found)

Scala Naturae

Aristotle - Father of Classic Taxonomy Scale of life: -great chain of being establishes man as dominate and perfect form of life -sets man above and apart from nature -inanimate matter (simple, imperfect) --> intermediate forms --> highest, complex perfect forms -incorporated into the religious belief that the earth and its creatures and the results of special creation, that they have not changed since they were created

Origin of the 1st cell cont.

Cell-like structures - Protobiont -boundary (membrane) -polymers inside contain info -polymers inside w/ enzymatic function -self-replication *taking on characteristics of life --> biological evolution Chemical selection- RNA World RNA in protobionts (RNA was probably the first material): -can store info -capacity for replication -enzymatic functions (ribozymes) *what RNA has that DNA doesn't have, helps create proteins *replaced by a DNA/RNA/protein world *view diagram in notes

Voyage of the HMS Beagle

Charles Darwin (1809-1882) -Father of Evolutionary Theory -left medical school and went to theology school to become clergy and dropped out of both becoming a naturalist -1831: age 22 left on voyage as Naturalist for 5 yrs (didn't get along with captain, didn't get paid) -survey from coast of South America to Galapagos and back to England coming back the way of Australia to collect plant and animal specimen *read Lyell and Hutton book

Parsimony (Occam's razor)

Cladists are always guided by the principle of parsimony: -the arrangement requiring the fewest assumptions is preferred (simplest explanation is chosen) -this would: leave the fewest number of shared derived characters unexplained, minimize the number of assumed evolutionary changes *the reliability of a cladogram is dependent on the knowledge and skill of the investigator ex) hypothesis 1 has 6 evolutionary changes and hypothesis 2 has 7, would reject the one w/ 7

Speciation

Cladogenesis: the splitting of one species into 2 (ancestral --> ancestral + new species) Anagenesis: the transformation of 1 species into a new species over time ( ancestral goes extinct bc the new species is formed)

Origin of the 1st cell

Clay hypothesis: -simple organics polymerize on solid surface (clay mud, inorganic crystals that have enzymatic qualities) into more complex organisms -stromatolites (Australia): mats of mineralized cyanobacteria (one of the oldest forms of life, living fossil, living boulders, layers can let us go back in time)

Evidence of evolution

Comparative anatomy (morphology): Homologous structures: anatomically similar because they are inherited from a common ancestor but may not be functionally similar -vertebrate forelimbs: bird, bat, whale, cat, horse, human all share (humerus, radius, ulna, metacarpals, phalanges) Analogous structures: -serve the same function, not constructed similarly, do not share a common ancestor (don't use them to construct evolutionary relationships) -convergent evolution: when organisms encounter similar environmental demands, they develop similar structures -ex) wings on insects and birds (wings are completely dif in structure but similar in capacity of flight)

Hardy-Weinberg Equilibrium

Conditions to be met: 1. No mutations - allelic changes do not occur, or change in one direction are balanced by change sin the opposite direction (no gene duplication, exon shuffling or horizontal genet transfer) 2. No gene flow - migration of alleles into or out of the population does not occur (closed-off population) 3. Random mating - individuals pair by chance and not according to their genotypes 4. No genetic drift - the population is very large, and changes in allele frequency due to chance alone are insignificant 5. No selection - no selective agent favors one genotype over another; all genotypes are equally adapted *highly unlikely but some individual genes may be following the equilibrium

Tracing phylogeny incorrectly

Convergent evolution- Analogy: -the acquisition of a feature in distantly related lines of descent -the feature is not present in a common ancestor -doesn't tell us about relatedness ex) giant armadillo, giant pangolin, giant anteater and spiny anteater all have similar body form -eye of an octopus & human eye Parallel evolution: -is the independent evolution of similar traits, starting from a similar ancestral condition (organisms are more closely related) -several species respond to similar challenges in a similar way ex) old world porcupine & new world porcupine -tenrec & hedgehog

Biological evolution

Descent with modification: -populations of organisms change over generations NOT individuals (individuals are acted on by natural selection that results in evolution of populations) -evolutions results in heritable traits that promote survival and reproductive success "It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change" - Charles Darwin Adaptation= any modification that makes an organism better suited to its way of life (help survival which translates resources to offspring) *better adapted organisms tend to survive and produce more offspring

Geologic Time Scale

Earth's history (4.55 bya to present) -timelines over which life has evolved through the history of life recorded in rock Changes in organisms as a result of: 1) Genetic changes (also coming about from interactions w/ environment) 2) Environmental changes Patterns correlated with emergence and extinction: Can Amy Like Frogs Very Much) 1) Climate/temperature (periods of major environmental change: ice ages, warming periods) 2) Atmosphere (initially no 02 now it is 21% O2, cyanobacteria helped give 02 to atmosphere) 3) Land masses- terrestrial vs. aquatic (continental drift 1-10 cm/yr bc of sea floor spreading) 4) Floods (sea-level rising)/glaciation (glacier moving across land masses leading to deposition and sea-level rising) 5) Volcanic eruptions 5) Meteorite impacts *marine life is oldest form which is why mass extinction are characterized by percent loss of marine species

What is a species cont.

Ecological species concept: using the ability of organisms to successfully occupy their own ecological niche or habitat, including their use of resources and impact on the environment, to distinguish species Phylogenetic (evolutionary) species concept: a species is an irreducible group of organisms diagnosably distinct from other such grouping and within which there is paternal pattern of ancestry and descent -morphological (anatomical), chromosomal, molecular characters used *best current working definition, broader

Survival of the fit

Fitness is the relative reproductive success of an individual -the most-fit individuals in a population capture a disproportionate share of the resources -interactions with the environment determine which individuals reproduce the most Adaptation: -changes that help a species become more suited to its environment -product of natural selection (only mechanism that leads to adaptation, key mechanism for evolution) *adaptations are determined by genome (random) and selected for by natural selection (nonrandom)

Fossil record

Fossil record (>10,000 yrs old) -fossils record history of life from the past -document a succession of life forms from the simple to the more complex (can see through strata) -sometimes the fossil record is complete enough to show descent from an ancestor ex) can see entire horse evolution (changes in size, forelimbs, teeth structure), first horse was smaller and a forest dweller ex) bird origins from reptiles: transitional fossil is the archaeopteryx and is the missing link between birds and reptiles ex) fish to tetrapods (amphibians): transitional fossil is the tiktaalik (has fish and tetrapod characteristics; lungs, lift head up, bonds in limbs similar to amphibians)

Tracing Phylogeny (evolutionary history)

Fossil record: -fossil record is incomplete -it is often difficult to determine the phylogeny of a fossil -for lots of organisms we only have fossil records -is selective Homology: -refers to features that stem from a common ancestor -homologous structures are related to each other through common descent ex) vert. forelimbs, embryology, cervical vertebrae (7) between giraffe, humans, and whale

Genetic Drift - Founder effect

Founder effect: -when a new population is started from just a few individuals (ex: religious persecution, founding of the U.S.) -the alleles carried by population founders are dictated by chance Formerly rare alleles will either: -occur at a higher frequency in the new population OR be absent in new population ex) the Lancaster, PA Amish group was started by 3 couples and now has 8,000 descendants: has a high incidence of Ellis-van Creveld syndrome (polydactyly, short stature, and shortening of the forearms and lower legs) -1/14 w/ recessive allele in Lancaster, PA Amish -1/1000 in general population *found in a much higher rate in this smaller population *members can leave but nobody can enter in

Causes of Microevolution (Gene Flow)

Gene Flow- Gene Migration: Movement of alleles between populations when: -gametes or seeds (in plants) are carried into another population -breeding individuals migrate into or out of population *continual gene flow reduces genetic divergence between populations and typically increases genetic diversity within the population Populations of relatively sedentary organisms are more isolated from one another than populations of very mobile organisms (subspecies)- can still reproduce by may be on their way to isolation, ex) salamanders on coast of California

Genes in natural populations

Genes can be monomorphic (99% of individuals = 1 allele) OR polymorphic (2 or more alleles in population)- multiple alleles for a trait Polymorphism comes about through various changes: 1. duplication of gene region 2. deletion of significant region of gene 3. change in a single nucleotide (SNP) - smallest and most common (90% of variation is due to this) in a gene Allele frequency = # of copies of a specific allele in population/ total # of all alleles for that gene in population Genotype frequency= # of individuals with a particular genotype/ total # of individuals in a population

Causes of Microevolution (Genetic drift)

Genetic drift: changes allelic frequency due to random chance -can cause the gene pools of 2 isolated populations to become dissimilar -some alleles are lost (0%) and others become fixed (100%) *stronger effect in small populations (the bigger the population --> more genetic variability --> random events don't impact as much) Likely to occur: -after a bottleneck -with severe inbreeding -when founders start a new population *a random event prevents a majority of individuals from entering the next generation (next generation composed of alleles that just happened to make it)

Maintenance of variations

Genetic variability is beneficial: -populations w/ limited variation may not be able to adapt to new conditions -maintenance of variability is advantageous to population -only exposed alleles are subject to natural selection bc phenotype interacts w/ the environment (only alleles that are manifested in the phenotype - many recessive get hidden) *Natural selection does not cause genetic changes *Natural selection acts on individuals *Population evolves as gene frequencies change

Darwin's Theory of Evolution

Geological observations consistent with those of Hutton & Lyell Biogeographical observations: -the study of the geographic distribution of life forms on earth -Darwin saw similar species in similar habitats, also saw tremendous diversity -reasoned related species could be modified according to habitat ex) armadillo in England vs. glyptodont in South America ex) The Patagonian Hare in South America vs. Hare in England ex) giant sloth

Phylogenetic trees

Goals of Systematics: 1) discover all species 2) reconstruct phylogeny (evolutionary history) of a group 3) classify accordingly (organisms) Phylogeny often represented as a phylogenetic tree (taxonomy scheme reflects evolutionary relationships/ history) -a diagram indicating lines of descent Each branching point: -is a divergence from a common ancestor -represents an organisms that gives rise to 2 new groups *shows vertical descent *archaens are more closely related to eucarya than bacteria

Utilizing Hardy-Weinberg Equilibrium

If p or q is changed in next generation --> Evolution has occurred! -Hardy-Weinberg identifies factors that cause evolution -Evolution detected by noting any deviation from a Hardy-Weinberg equilibrium of allele frequencies in the gene pool of a population *Equilibrium population = hypothetical population in which evolution does not occur *conditions for Hardy-Weinberg are rarely met, Hardy-Weinberg population provides starting point for studying mechanisms of evolution Microevolution = accumulation of small changes in the gene pool of a population over a relatively short period of time (that accumulate and can lead to macroevolutionary events), forms the basis for macroevolution

Precambrian time

Includes approx. 87% of geologic time (Hadean, Archaeon, Proterozoic Eons): 600-4,500 mya -little or no atmospheric oxygen -lack of ozone shield allowed UV radiation to bombard Earth (lots of energy/heat in environment) First cells came into existence in aquatic environments (primordial soup) -prokaryotes -cyanobacteria left many ancient stromatolite fossils (when you section them off you see all the layers, living fossils, blue-green algae, look the same as 3.9 bya) -added first oxygen to the atmosphere (through photosynthesis --> inc. 02 --> formation of ozone shield) -evolution of aerobic species (aerobic respiration is favored bc it creates more energy, glycolysis is universal pathway--> probably first to evolve) Eukaryotic cells arise approx. 2 bya (endosymbiotic hypothesis) - explains origins of eukaryotic organelles (nucleus, mitochondria and chloroplasts: cyanobacteria, have their own genome, self-replicating organelles) Multicellularity arises approx. 1.5 bya

Pre-Darwinian Thought

Influenced by Theology ,Myth and Superstition Anaximander: organisms evolve over time, simpler forms preceding more complex Plato: objects are temporary reflections of ideal forms that reside someplace else, "essentialism", theory of forms Aristotle: all living things can be arranged in a linear hierarchy -- Scala naturae Creationism: a god is absolute creator of heaven and earth, out of nothing, by an act of free will; includes Christians, Jews, and Muslims Spontaneous Generation (Dark Ages): living comes from nonliving -sweaty rags in open jar with grain after 21 days produces mice -rotting meat produces maggots -dust gives rise to flies

Advantages of DNA/RNA/Protein world

Information storage: -DNA would have relieved RNA of informational role and allowed to do other functions -DNA is less likely to suffer mutations, more stable Metabolism and other cellular functions: -proteins have a greater catalytic (enzymatic) potential and efficiency (better than RNA at being enzymes) -proteins can perform other tasks- cytoskeleton, transport, etc. DNA --transcription--> RNA --translation--> amino acid chain (polypeptide) --folding--> protein

Silurian Period

Invasion of land -stable climate, glaciers melted --> sea-level rising -significant vertebrates (many fishes) and plants, coral reefs formed (enough calcium carbonate) -large colonization by terrestrial plants (seedless vascular: ferns, horse tails) and animals (arthropods, spiders/centipedes) -move to new environment --> new food and ecosystems (environment in land vs. water is very different) -water is buoyant, land has more O2

Devonian Period

Invasion of land, Age of Fishes -N dry, S wet (oceans) -many more terrestrial species -gymnosperms emerge (seeded plants w/ naked seeds: conifers, pines, evergreens) -first forests are formed -insects emerge and rapidly diversify -Tetrapods - amphibians emerge -invertebrates flourish in the oceans -The Age of Fishes: explosion of fishes, fishes are most diverse vertebrates

Taxonomy through 17th to 18th century

John Ray: 1st thorough study of the natural world Carolus Linnaeus: -the fixity of species (once organisms came into being they didn't change) -each species had an ideal structure and function, and a place in the scala naturae (scale of complexity) -Binomal system of nomenclature Count George Buffon: -wrote catalog of all known plants and animals -suggested life forms change over time Erasmus Darwin (Charles grandfather): -suggested common descent -evidence in developmental patterns, artificial selection, vestigial organs (often looked at farm animals)

Evolution in action - industrial melanism

Kettlewell's moths: Before industrial revolution: Peppered moths: 10% dark colored (carbonaria), 90% light colored (typica) After industrial revolution (mid 19th century): -soot in atmosphere, tree trunks darkened, lichens killed -birds act as a selective agent (may not be the only factor) -Peppered moths: 80% dark colored, 20% light colored Now: 20% dark colored, 80% light colored *evolution in action, selective force has been the same throughout *birds act as selective agent on the moths, visual predator

Cuvier

Late 18th century -first to use comparative anatomy (structure) to develop a system of classification -founded Paleontology - fossils Proposed catastrophism: -local catastrophes in past had caused later strata (rock) to have a new mix of fossils -volcanic event, meteorites, etc. -after each catastrophe, the region was repopulated by species from surrounding areas (adaptive radiation)

Marsupials

Marsupials- pouched mammals, deliver their offspring very early and the offspring develop in the pouch -prime example of biogeography and evolution -found in high concentrations in Australia, moving into New Zealand, South America and North America (here we only have 1: the opossum) -the way that continents have split apart is part of the story (2.5 cm or 1 inch a year) and also the fact that marsupials evolved earlier than placental mammals -Australia drifted off w/ marsupials but no placental mammals (this is why Australia has the most) -North America was connected to Eurasia where placental mammals were abundant which is where there are minimal marsupials *placental mammals have an advantage because their young survive better, born at later state of development

Mass extinctions

Mass extinction: -clear the slate - after mass extinction --> adaptive radiation: organisms that survive, take over and flourish and diversify -relatively short in geologic time doesn't mean the extinction was a fast event Permian mass extinction: -occurred btwn paleozoic and mesozoic eras -largest known -caused by dramatic fluctuations in climate, sea-level, rising CO2 level and savage global warming KT mass extinction (Cretaceous-Tertiary extinction): -occurred btwn mesozoic and cenozoic eras -65 million yrs ago 75% of plants and animals -"The Great Dying": all the non-avian dinosaurs wiped out along with other plants and animals -asteroid hit the surface of Earth (powerful as 10 billion atomic bombs) wiping out large amounts and also leading to volcanic activity --> huge quantities of sulfur and ash in atmosphere Mass extinction- currently?

New Discovery

Massive new animal species discovered in 500 million yr old Burgess Shale -Paleontologists unearth one of the largest radiodonts (primitive arthropod) of the Cambrian explosion (9/8/21) Titanokorys gainesi -1/2 meter long -swimming head -3 part carapace(shell) *we are not done, new discoveries come to life all the time

First biomolecules

Miller and Urey's Apparatus and Experiment (1953)- supports reducing atmosphere hypothesis: -showed that biochemicals could be produced from simple nonbiological sources -primitive atmospheric gases (CH4, NH3, H2, H20) in a reducing environment (no 02) -strong energy sources (electric spark was used to simulate intense energy from lightning, meteorites, radiation, UV, volcanoes bombarding earth) --> yielded HCN (hydrogen cyanide), CH20 (formaldehyde), glycine, sugars, a.a's, N-bases More recent: -neutral environment: CO, CO2, N2, H20 -organics can be made under a variety of conditions *using modern technology found more a.a's, amines and sugars from Miller and Urey's closet

Classification categories

Modern taxonomists use the following classification (each group includes one or more from the previous): Domain (bacteria, archaea, eukarya) Supergroup Kingdom Phylum Class Order Family Genus Species (2 part scientific name, most specific)

Modern evidence of evolution

Molecular homologies: Almost all living organisms (bc of descent from common ancestor): -use the same basic biochemical molecules -utilize same DNA triplet code (genetic code is universal) -utilize same 20 amino acids in their proteins -utilize ATP as energy source Genetic homologies (DNA base-sequence differences): -when very similar, suggest recent common descent -when more different, suggest more ancient common descent *tend to look at developmental genes (pox and pac genes) *central dogma of molecular biology to applies to all organisms

Natural selection vs. evolution

Natural selection acts on individuals in a species Evolution is a property of population: -occurs generation to generation -descendents are dif from ancestors -change in allele (gene) frequencies; change in genetic make-up of population over time (generations) *measure the evolutionary changes by gene frequency changes over time bc it is the genotype that influences phenotype

Causes of Microevolution (Nonrandom mating)

Nonrandom mating- when individuals do not choose mates randomly Assortative mating: individuals select mates with their phenotype and reject opposites, incr. # of homozygotes Disassortative mating: dissimilar phenotypes mate preferentially, incr. # of heterozygotes Inbreeding: mating of 2 genetically related individuals, chose a mate from same genetic lineage (consanguineous) -higher frequency of recessive alleles and diseases associated with that ex) hemophilia in royalty in England, breed dogs and horses

Pace of evolution

Phyletic gradualism: -speciation occurs gradually -stasis is apparent, not real -transitional links found (missing links) -ancestral species transformed into new species *gradually accumulating, subtle Punctuated equilibrium: -speciation occurs rapidly -species experiences stasis -transitional links not found -subpopulation becomes new species ex) sharks, cyanobacteria, some fish *living fossils (look just like ancestral forms)

What is a species?

Pre-Darwinian idea: Typographical (Morphological) Species Concept: species is defined by fixed, essential features; each species has a unique structure that makes it distinct (**it is not right that they are fixed, put to bed by evolutionary theory) Biological Species Concept: a species is a reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature; interbreeding w/ common gene pool to produce viable, fertile offspring *drawbacks: -species have dimensions in space and time (how do you know from fossil record if they were interbreeding) -sexual and asexual reproduction (what characteristics do you use for asexual) -unit of evolution and taxonomic category w/ scientific name

Primate evolution

Primate evolution began in Quaternary Period (1.8 mya to today) -age of man (Hominids) -Homo sapiens appear 130,000 years ago

Molecular data

Protein comparisons: -Immunological techniques: degree of cross reactions used to judge relationship (how the proteins react to antibodies, stimulate immune system) -Amino acid sequencing (similar sequence in same protein indicates close relationship, newer) RNA and DNA comparisons: Systematics assumes: -2 species w/ similar base-pair sequences are assumed to be closely related -2 species w/ differing base-pair sequences are assumed to be only distantly related ex) cytochrome c, p53 take species DNA, break hydrogen bonds, bond one strand from each DNA and see where the complementarities lie (fewer mismatches=more identical)

Fossil Dating -Absolute

Radiometric dating- half life: -the length of time required for half the atoms to change into something else (spontaneously change by giving of particles (types of radiation)) -how they give off radiation, particles, is unaffected by temp, light, pressure, etc. -all radioactive isotopes have a dependable half life (ranges from seconds to billions of yrs) *may need several isotopes to age specimen, ex) if so much C-14 has become N-14 *you don't sample the fossil bc it would destroy it, you sample the sediment around the specimen ex) Carbon-14 --> Nitrogen-14 : 5730 yrs In living organisms there is a ratio of C-12 (stable) to C-14(radio isotopic) but when it dies no new C is added, and the C-14 that exists after death starts to decay (carbon is the basis of all organic matter, brought in by eating and breathing)

Primitive Earth

Reducing Atmosphere Hypothesis/ Abiotic (Prebiotic) Synthesis- 1920's: Oparin and Haldane Primitive atmosphere: -H20 vapor, N2, CO2 -small amounts of H2 and CO *little free oxygen (reducing atmosphere, without oxygen large molecules don't get broken down, also no bacteria that are usually responsible for decomposition) *originally too hot for liquid water (no ozone layer to shield sun radiation) *as earth cooled, water vapor condensed to liquid water *primordial soup (water bath, accumulation in ocean, thick and warm) Spontaneous formation of organic molecules in primordial soup: inorganic --> organic -monomers evolved and joined to form polymers

Adaptive melanism

Rock pocket mouse -Dr. Michael Nachman has quantified predation on rock pocket mice and identified adaptive changes in coat-color genes that allow the mice to travel under the radar of hungry predators *watch video

Species vs. Population

Species- group of related organisms that share a distinctive form; among species that reproduce sexually, members of the same species are capable of interbreeding to produce viable and fertile offspring Population: members of the same species that are likely to encounter each other and thus have the opportunity to interbreed (usually in same region)

Systematics and taxonomy

Systematics- the study of the biological diversity and evolutionary history of life on earth Taxonomy- branch of biology concerned with identifying, naming, and classifying organisms Name: only 1 scientist gets to "name" a species Identify: anyone can with a key (working through a series of characteristics to identify unknown specimen) Classify: group a species with its closest relatives (evolutionary principles) Began with the ancient Greeks and Romans: -Aristotle classified organisms into groups such as horses, birds, and oaks (Scala naturae) John Ray: -believed that each organism should have a set name

The Three-Domain System of Classification

The Bacteria and Archaea are so different they have been assigned to separate domains Distinguishable by: -difference in rRNA base sequences -plasma membrane chemistry -cell wall chemistry Domain Eukarya: -uni- and multicellular organisms -cells w/ a membrane-bound nucleus -sexual reproduction common -contains kingdoms: kingdom fungi, kingdom plantae, kingdom animalia, protists (now new kingdom = hemimastigotes)

Biology

The scientific study of living organisms and how they have evolved -scientific: discovery science --> hypothetico-deductive method (scientific method (prescribed way)) -living organisms: redundant term because organisms are living *all forms of life share common characteristics bc they evolved from common ancestor (unity) *guiding principle in biology is the evolutionary theory is how biology makes sense Descent w/ modification: helps to explain both unity and diversity, but lots of organisms waiting to be described (15 to 100 million)

Galapagos Islands

Tortoises: -Darwin observed tortoise neck length varied from island to island -proposed that speciation on islands correlated with a difference in vegetation (species could be modified based on environment) High dome shells and short neck: lush vegetation w/ lots of rainfall Flatter shell and long neck: dry areas, hard to reach vegetation Finches: -Darwin observed many dif species of finches (13) on various islands, each had unique beak structure that correlated to feeding habits -speculated they could have descended from a single pair of mainland finch (island species originated from mainland species)

Since dawn of human civilization

Vanished: 83% of wild mammals 80% of marine mammals 50% of plants 15% of fish *large cats may be gone in 10-15 yrs *rhino, giraffe, Pangolins will soon be extinct

Comparative anatomy:

Vestigial structures: -fully developed anatomical structures -reduced or obsolete function ex) human appendix, male breast tissue/nipple, wisdom teeth, human tailbone (coccyx), erector pili and body hair, blind fish, sex organs in dandelions, wings on flightless birds, hind leg bones in whales/snakes, fake sex in virgin whiptail lizards (pseudocopulation) Pseudocopulation: vestigial behavior: engage in behavior that is programmed in genome, act like they are having sex but not outcome because they are females

New discovery of Ediacaran fossils

Yilingia spiciformis - newly discovered (2018) in Southern China -segmented cylindrical body (worm?) -similar to Cambrian animals -ages what we know about animal life (animal life may be older than we thought)

Phylogenetic circle

all species (past and present) are related by an evolutionary history -vertical descent w/ mutation (parents w/ offspring) -horizontal gene transfer (non-offspring, bacteria, archaeons, single-cell prokaryotes) *origins of mitochondria and chloroplasts

Phylogenetic trees cont.

classification lists the unique characters of each taxon and is intended to reflect phylogeny Characters: structural, chromosomal, molecular (heritable, measurable) Primitive characters: features present in all members of a group, and present in the common ancestor, ancestral trait Derived characters: present in some members of a group but absent in the common ancestor (unique to dif lineages, characteristics that come on later bc of environmental pressures), structural chromosomal, molecular features (genetic basis, measurable)

Plate tectonics

continental drift (continents have not always been in the same place) -helps to explain the distribution of organisms that we see End of paleozoic: supercontinent pangea Triassic: pangea has split into northern and southern (Laurasia, Gondwana) --> Jurassic --> Cretaceous: north america, eurasia, south america, africa , australia, india not connected to eurasia and antartica --> cenozoic: present day (divide between North America and Eurasia)

Ediacaran Fossils

end of proterozoic eon -Ediacaran/Vendian Period (600-540 mya) -Multicellular animals appear, including Sponges -shallow marine mudflat animals in unusual forms, 2 tissues layers, no internal organs or shells or bones (invertebrate), very abundant -acquired nutrition by absorption (big surface area to volume ratio) -wheels, ribbons, fawns -possess collagen *mass extinction occurred

Core concepts for biological literacy

even so I pledge sobriety 1) Evolution: the diversity of life evolved over time by processes of mutation, selection, and genetic change 2) Structure and function: basic units of structure define the function of all living things 3) Information flow, exchange, and storage: the growth and behavior of organisms are activated through the expression of genetic information in context 4) Pathways and transformations of energy and matter: biological systems grow and change by processes based upon chemical transformation pathways and are governed by the laws of thermodynamics 5) Systems: living systems are interconnected and interacting (cells, organisms)

Macroevolution

evolutionary changes that create new species and groups of species; accumulation of microevolutionary changes over long periods of time

Whales

fossil record spans 50 million years -descended from 4 legged ardeodactile (land dweller) -terrestrial tetrapod to aquatic animals lacking hind limbs (shows how evolution can involve what structures you lose) Order Cetacea: -whales -dolphins -porpoises *hippopotamus is the closest, living relative, not ancestral

Evolution

heritable change in 1 or more characteristics of a population or species from 1 generation to the next Microevolution: changes in a single gene in a population over time Macroevolution: formation of a new species or groups of species

Cladistic vs. traditional view of reptilian phylogeny

look at chart in notes *taxonomy is a work in progress, re-organize previous ideas *birds are only organisms to have feathers, if it has feathers it is a bird, birds also can maintain constant body temp, birds are glorified reptiles

Traditional systematics

mainly uses anatomical data (original way of constructing phylogenetic trees) -classify organisms using assumed phylogeny with emphasis on phenotype (problems w/ that bc of conv. evolution) -stress both common ancestry and degree of structural difference among divergent groups -construct phylogenetic trees by applying evolutionary principles to categories -not strict in making sure all taxa are monophyletic Monophyly (good): most recent common ancestor & all descendants from that ancestor in same group Paraphyly (okay): includes common ancestor but not all descendants, put descendants into dif group bc we think they have something that makes them unique Polyphyly (never acceptable): members traced to separate ancestors, does not contain the most recent common ancestor of the group

Taxonomy

mid-1700s, Carolus Linnaeus Binomial system of nomenclature: -first word is genus name (capitalized, noun) -second word is specific epithet (refers to 1 species within its genus, adjective) -a species is referred to by the full binomial name (either underline or italicized) -genus name can be used alone to refer to a group of related species *scientific name is universal, reduces confusion, unique, promotes communication (always latin)

Cladistic systematics

more modern approach, traces evolutionary history of the group under study, only recognizes monophyletic groups uses shared derived characters (synapormorphies: homologous structures) to: -classify organisms -arrange taxa into a cladogram -a cladogram is a special type of phylogenetic tree *clade: an evolutionary branch that includes a common ancestor together with all its descendant species (monophyletic group) Monophyletic group: taxon whose units all evolved from a single parent stock; most recent common ancestor and all of its descendants outgroup: defines oldest features, study group that has oldest feature

Reproductive isolating mechanisms

reproductive isolating mechanisms inhibit gene flow between species and maintain distinctiveness of species, two types: Prezygotic mechanisms (discourage attempts to mate): -habitat isolation -temporal isolation (timing of reproductive events) -behavioral isolation (members respond to species behavioral cues, ex) songs, dance) -mechanical isolation (male anatomy doesn't fit w/ female anatomy) -gamete isolation (sperm can't fertilize the egg of a dif species (enzyme on sperm can't dissolve egg coating)) Postzygotic mechanisms (prevent hybrid offspring from developing or breeding): -hybrid inviability (zygote mortality) -hybrid sterility (can't breed) -hybrid breakdown ex) tiglon, liger, leopon, mules are male donkey + female horse *these animals don't usually cross paths, their mix is a result of human interventions (artificial insemination)

DNA-DNA Hybridization

review chart in notes

Darwin's Explanatory Model of Evolution by Natural Selection

review chart in notes Evolutionary model: -can explain evolution of all species -can tell us how it came about *offered a rational explanation with lots of evidence

Strata + fossils

review diagram *younger are towards top *older strata are toward base *each strata developed under different environmental conditions

Population genetics

study of genes and genotypes in a population -want to know extent of genetic variation, why it exists, how it is maintained, and how it changes over the course of many generations tells us about adaptations -helps us understand how genetic variation is related to phenotypic variation ex) if 1 individual has a specific gene to begin with and doesn't pass it on, no one inherits it BUT if it does pass it on by chance it leads to phenotypical changes

Classification system - previous

until the mid-1800's biologists recognized only 2 kingdoms: -plantae (plants) -animalia (animals) *protista (protists) were added as a third kingdom in the 1880s (single-celled eukaryotes) Whittaker expanded to 5 kingdoms in 1969 by adding Fungi and Monera (prokaryotes)

Phanerozoic Eon

well displayed life Paleozoic Era -543-248 mya -3 major mass extinction events Burgess Shale organisms: -fossil deposit discovered in 1909 -both hard and soft shell organisms were preserved (usually don't have lots of evidence for invertebrates) because of mud-slide giving a wealth of organisms