Introduction to Biology

Intro to Biology

• Inductive reasoning moves from specific observations to general principles.
• Deductive reasoning applies general principles to specific situations.
• Controlled experiments test one variable, using a control group for comparison.
• The independent variable is manipulated and plotted on the x-axis.
• The dependent variable is affected by the independent variable and plotted on the y-axis.
• The experiment aims to see how the independent variable affects the dependent variable.

Characteristics of Life

• Living things exhibit order and complexity.
• They sense and respond to their environment.
• They regulate their internal conditions.
• They reproduce, ensuring the continuation of their species.
• They grow and develop, changing over their lifespan.
• Growth refers to an increase in size and mass.
• Development involves morphogenesis and differentiation.
• Living things utilize energy for various processes.
• They evolve over time, adapting to changing environments.
• Cellular respiration breaks down matter to produce ATP.
• Photosynthesis uses sunlight to produce glucose.

Emergent Properties

• New properties arise at each step in the hierarchy of life.
• These properties result from the arrangement and interaction of components as complexity increases.

Cell Structure

• The cell is the basic unit of life.
• It consists of a cell membrane, cytosol, genetic material (DNA), and organelles.
• Prokaryotic cells lack a nucleus and membrane-bound organelles and tend to be simpler.
• Eukaryotic cells have a nucleus and membrane-bound organelles and tend to be more complex.
• DNA, the genetic material, comprises nucleotides.
• A gene is a DNA segment coding for a protein.
• Alleles are alternative forms of a gene, like B for brown eyes and b for blue eyes.
• Each gene has two alleles, with one passed down during reproduction.
• The genotype is an individual's allele combination for a gene, such as Bb.
• The phenotype is the observable trait, like eye color.

Intro to Evolution

• Evolution is a change in allele frequency in a population over time (change over time, descent with modification).
• A gene for leg length in dogs, S, has alleles S (short) or S' (long).
• The gene pool contains all alleles in a population.
• Allele frequency is calculated as the number of specific alleles divided by the total number of alleles (frequency of allele S = number of S alleles / total number of alleles).
• If allele frequency remains constant across generations, evolution isn't occurring.
• Allele frequencies are expressed to three decimal places.
• Lack of allele variation prevents evolution.
• Mutations create new alleles.

Mutations

• Mutation is a random error or change in a gene's DNA sequence.
• Only mutations in germ-line cells (eggs and sperm) influence evolution.
• Types of mutations include substitutions, insertions, deletions, and frameshifts.

Evidence of Evolution

• Direct observation
• Fossil record
• Homology
• Vestigial structures
• Biogeography

Direct Observation

• Direct observation is most readily seen in rapidly reproducing organisms.
• An example is the emergence of resistant bacteria.

Fossil Record

• The fossil record shows evidence of past changes over time.

Homology

• Homology is similarity due to shared ancestry.

Vestigial Structures

• Vestigial structures were functional in ancestors but reduced or nonfunctional in descendants.
• The pelvic bone in whales serves as an example.

Biogeography

• Biogeography studies the distribution of species.
• Species distribution is best explained through shared ancestry.
• The principle of parsimony suggests related species are located close together due to common ancestry.
• Homologies share ancestry but not necessarily function.
• Analogies share function but not ancestry.
• Convergent evolution is the independent evolution of similar features in different lineages.

History of Evolutionary Thought

• Ancient Greeks had varying views on the gradual change of life.
• Aristotle believed that species were fixed.
• Scala naturae is a ladder of complexity for living things.
• Carolus Linneaus created the Linnean classification system but did not believe in evolution.
• Georges Cuvier, the father of paleontology, supported catastrophism but did not believe in evolution.
• Catastrophism: boundaries between strata represented catastrophic events wiping out species.
• Charles Lyell, a geologist, believed in uniformitarianism (earth's landscape shaped by slow, gradual changes).
• Jean-Baptiste De Lamarck proposed use and disuse and inheritance of acquired traits.
• Charles Darwin proposed natural selection.
• Alfred Russel Wallace independently developed a natural selection hypothesis.
• Darwin and Wallace jointly published their work, with Darwin gaining more recognition.

Evolutionary Mechanisms

• Natural selection: Alleles become more or less common based on their impact on survival and reproduction.
• There must be difference in survival and reproduction due to variation in the trait.
• It is an observable, gradual process.
• Natural selection is similar to artificial selection (selective breeding).
• It increases adaptation, matching organisms to their environment.

Darwin's Observations

• Members of a population vary in inherited traits.
• Species produce more offspring than the environment can support, leading to mortality.

Darwin's Inferences

• Individuals with traits that increase survival and reproduction leave more offspring.
• Unequal survival and reproduction lead to the accumulation of favorable traits.

Example

• Peppered moths' allele frequency changed during the Industrial Revolution in England.

Sexual Selection

• Sexual selection is nonrandom mating that increases reproductive success at a potential survival cost.
• There must be organisms boinking' and a trait driving reproductive success
• Evolutionary fitness is the ability to survive, reproduce, and pass on alleles.
• Survival is necessary, but reproduction is essential.
• Intersexual selection involves mate choice due to limited egg resources.
• Intrasexual selection involves competition.

Gene Flow

• Gene flow is migration, leading to alleles becoming more or less common as individuals enter or exit. Is random and non-random

• Key Effects of Gene Flow on Allele Frequencies:

• Increases genetic diversity by introducing new alleles.

• Reduces genetic differences between populations, making them more similar.

• Can counteract natural selection if migrants introduce alleles that are disadvantageous in the new environment.

• Organisms move in an out of a population

• Two butterfly populations example; blue winged and orange winged

Genetic Drift

• Alleles become common or rare due to random events.
• There must be random occurrences messing with allele frequencies.
• A sampling issue takes individuals out by chance.
• It affects smaller populations more strongly.
• It can lead to fixation or loss of alleles in short periods.
• The bottleneck effect is when a large population is reduced to a small size.
• The founder effect occurs when a few individuals form a new, isolated population.

Bottleneck effect example

• The Old Order Amish community in Pennsylvania was founded by a small number of individuals

Mutations

• Mutations introduce new alleles.
• A new allele's frequency starts at zero.

Hardy-Weinberg Equilibrium (HWE)

• Under HWE, no evolutionary mechanisms are occurring for a gene.
• There is no natural selection or mutations, no net migration, an extremely large population, and random mating.
• p^2+2pq+q^2 = 1
• p^2 = AA
• 2pq = Aa
• q^2 = aa

Species and Speciation

• Species Concepts:
  • There are over 20 different concepts.
  • Used in Bio 7:
    • Morphological: Organisms differing in shape/appearance are different species.
    • Genetic: Organisms with DNA sequences above a certain % identity are the same species.
    • Biological: Interbreeding natural populations that are reproductively isolated are different species.

Morphological Species Concept

• Good for studying extinct species.
• Used by paleontologists (fossil boys).
• Limited because it can be misleading and has limitations.
• Angler fish males are small little parasitic bois that latch onto the big chungus females

Genetic Species Concept

• Good for organisms with accessible genetic material.
• Bad for organisms without accessible genetic material.

Biological Species Concept

• Can reproduce with one another.
• If an organism can't reproduce with another organism, they are reproductively isolated.
• Reproductively isolated groups cannot produce viable and fertile offspring.
• Viable offspring can survive to adulthood.
• Fertile offspring can reproduce themselves.
• Limits:
  • Doesn't apply to asexually reproducing species.
  • Hard to test for extinct or difficult-to-observe species.

What reproductive barriers are

• Barriers that occur at or before fertilization is prezygotic barriers.
• Barriers that occur after fertilization postzygotic barriers.

Prezygotic barriers

• Habitat isolation: Based on location.
• Temporal isolation: Based on time.
• Behavioral isolation: Behavior must be right.
• Mechanical isolation: Reproductive organs don't fit. lock and key
• Gametic isolation: Gamete surface proteins are incompatible.

Postzygotic barriers

• Reduced hybrid viability: Offspring doesn't survive long because of hybridization.
• Reduced hybrid fertility: Offspring is sterile due to hybridization.
• Hybrid breakdown

Speciation

• The process creates new species.
• It occurs when one species splits into two.
• Allopatric speciation occurs when one species splits into two in different locations due to a geographical barrier.
• If species can mate after barrier removal, speciation has not occurred.
• Sympatric speciation involves new species forming in the same location.
• A hybrid zone forms when two species with incomplete reproductive barriers interbreed.

What possible outcomes can occur in hybrid zones

• Stability: Fit hybrids continue to be produced with the 2 parent species.
• Fusion: Weak reproductive barriers weaken until species become one.
• Reinforcement: Hybrids are less fit, so species diverge until hybridization is impossible.

History of Life on Earth

• Early Earth
  • Atmosphere contained water vapor, methane, ammonia, sulfur gas, carbon dioxide, and hydrogen.
  • Earth cooled, condensing water vapor into oceans.
  • Volcanic activity may have formed islands.

Start of life in early Earth?

• Synthesis of simple organic molecules
• Synthesis of macromolecules
• Formation of protocells
• Origin of self-replicating mechanisms

Oparin Haldane Hypothesis

• Simple organic compounds could have formed from inorganic molecules found in the earths early atmosphere.

Miler-Urey

• tested the Oparin Haldane hypothesis

Eons of Time

• Hadean Eon (~4.6 - 4 BYA)
  • Earth's surface was partially molten.
  • It was a period of volcanism and asteroid impacts.
  • Named after the Greek god Hades (EVERYTHING IS LAVA).
• Archean Eon (4.0 BYA to 2.5 BYA)
  • The word "ancient" origins comes from Greek.
  • Life originated during this eon (as far as evidence is concerned).
  • Stromatolites (3.5 BYA) are the first evidence of life.
  • Small, unicellular prokaryotes form layer-cake-like structures.
• Proterozoic Eon (2.5 BYA to 542 MYA)
  • The name means "time before animals."
  • Atmospheric oxygen levels rose due to photosynthetic bacteria.
  • Eukaryotic cells originated.
    • Energy-producing organisms got engulfed by a larger organism, creating a symbiotic relationship, which is Endosymbiotic theory
    • Points to the origin of mitochondria and chloroplasts (Lynn Margulis creator).

Endosymbiotic theory evidence

• Chloroplasts and mitochondria have their own DNA and their own cell membranes.
• Chloroplasts and mitochondria are about the same size as bacteria.
• Mitochondria appear to have been derived from "purple bacteria."
• Mitochondria appear to have been derived from "photosynthetic bacteria."
• End of Proterozoic eon (574-535 MYA):
  • Soft-bodied, multicellular eukaryotes arose.
• Phanerozoic Eon (542 MYA to present)
  • Eras:
    • Paleozoic: 542 - 241 MYA
    • Mesozoic: 251 - 65.5 MYA
    • Cenozoic: 65.5 MYA to present

Paleozoic Era

• Paleozoic Era 542 - 241 MYA
  • Cambrian 542 - 241 MYA
    • The most diverse period of all time (MDPOAT).
    • THIS WAS HAPPENING IN THE OCEAN
    • The Cambrian explosion significantly increased animal diversity and disparity.
    • Diversity number of different species
    • Disparity number of different body plans
    • Almost all living phyla appear in the fossil record.
    • Most of the fossils from the Cambrian period were found in the Burgess Shale in Yoho National Park, Canada
      • Cambrian animals:
        • Trilobites
        • Opabinia:
          • had 5 eyes and a vaccuum cleaner mouth
        • Anomalocaris (strange shrimp):
          • hard to find fossils because body breaks apart upon death
        • Hallucigenia
          • wtf is this, we don't know
          • pointy back with lil walky bois on the bottom
        • Pikaia
          • oldest known form of phylum chordata (US!)
  • Ordovician 488 - 444 MYA
    • Mostly dominated by marine life
    • Saw the emergence of ostracoderms (armored jawless fishies)
    • Some terrestrial life starts to pop-off
      • Tiny non-vascular plants invade land
  • Silurian 444-416 MYA
    • Shit goes onto land
    • Rise of jawless freshwater fishies from phylum Chordata
    • Clear evidence of small vascular plants, fungi, and arthropods on land
  • Devonian 419-359 MYA
    • Referred to as "the age of the fishies" because of the large amount of fish diversification that occured.
    • Origin of placoderms (now extinct)
      • marine life that had sharp teeth and armored skin
    • Origin of lobe-finned and ray-finned fishies
    • First tetrapods (four footed animals) move onto land
    • Ferns start to pop off (big ass ferns)
  • Carboniferous 355-299 MYA
    • Named because a large majority of earths coal was deposited during this time
    • Diversification of ray-finned fishies occurs
    • The cooling climate allowed for the polar ice caps to form, dropping sea levels and increasing terrestrial habitats
    • BIG OL SWAPS WITH BIG OL VASCULAR PLANTS
    • First winged insects pop off
    • Tetrapods diversify and amphibians dominate
    • Amniotes originate (reptiles, birds, mammals)
  • Permian Period 299-251 MYA
    • Ammonites (marine boi) diversify
    • All the continents form a supergroup (pangea), water levels are lowest ever
    • Reptiles diversify
    • Gymnosperms (cycads, ginkgos, conifers) dominate plant-life
  • PERMIAN/TRIASSIC MASS EXTINCTION
    • Over 90% of all species went extinct
      • Causes:
        • Intense volcanic eruption
        • Large rise in methane-producing bacteria
        • A rise in ocean temperatures by 6°C, causing ocean acidification
        • Ocean acidification kills animals with calcium carbonate shells (poor lil guys)

Mesozoic Era

• Mesozoic Era 251-196.6 MYA
  • Surviving species spread and diversified
  • DINOS BOI
  • Small teeted bois (mammals)
  • floral was dominated by gymno sperms
  • Age of the reptiles
  • Jurassic Period 196.6-145.5 MYA
    • Dinos diversified
      • On land
        • Sauropods
        • Theropods
        • Stegosaurs
      • In the sea
        • Ichthyosaurs
      • In the air
        • pterosaurs
    • Origins of birbs?
  • Cretaceous Period 145.5-65.5 MYA
    • Continued diversification of dinos
      • tyrannosaurus rex, triceratops/torosaurus, velociraptor
    • Origin of flowering plants
    • Most families of insects appear
  • Cretaceous/Paleogene Mass Extinction
    • Causes:
      • Massive climate change due to comet/asteroid hitting earth. Impact site is the Chicxulub crater on the Yucatan peninsula, discovered by Adriana Ocampo.
    • 80% of all know species ded
      • Half of all marine species ded
      • All non-avian dinosaurs ded

Cenozoic Era

• Cenozoic Era
  • Paleogene Period 65.5-28 MYA
    • Mammals be poppin' off. large teets
    • Surviving mammals, birds, flowering plants and pollinating insects diversify
    • Flowering plants are dominant
  • Neogene Period 23-2.6 MYA
    • Hominins appear (our ancestors)
  • Quaternary Period 2.6 MYA - present
    • Humans appeared 200,000 years ago

Systematics

• Systematics the science of naming and classifying organisms and determining their evolutionary relationships
  • phylogenic reconstructing phylogenies. uses DNA
  • taxonomy naming species and monophyletic groups (clades). doesn't use DNA
• Linnean Classification
  • Domain Kingdom Phylum Class Order Family Genus Species
    • dirty king philip came over for group segs
  • clades are monophyletic and do not have an agreed-upon rank.
• scientific names are binomial
  • binomial means 2 terms
    • first word is genus name, is always capitalized
    • second word is species epithet, is never capitalized
    • scientific name is always italicized when typed
    • scientific name is underlined when written
  • for higher groups (family or larger), always Capitalize first letter and never italicize or underline

Animal Diversity

• Domain Eukarya Kingdom Animalia
• Metazoa (also known as kingdom animalia)
  • Synapomorphies
    • cell structure (no cell walls or chloroplasts)
    • are multicellular
    • animals ingest food
• Phylum Porifera
  • commonly known as sponges
  • are asymmetrical
  • does not have true tissues, but some cells have special functions
  • are sessile (non-mobile) with sac-like bodies
  • are filter feeders that use intracellular digestion
• Eumetazoa (true animals)
  • Synapomorphies
    • symmetrical
    • have true tissues
• Phylum Ctenophora
  • commonly known as comb jellies (s'cute)
  • have eight rows of cilia to move around (s'cute)
  • are radially symmetrical
  • generally considered to have two simple tissues:
    • comb rows rows of fused cillia that beat synchronously to propel animal
    • many members have two long tentacles for capturing prey with sticky cells called colloblasts
  • cannot sting (s'cute)
• Phylum Cnidaria
  • commonly know as stinging nettle
  • split into subphylum medusozoa and subphylum anthozoa
  • are radially symmetrical
  • have two simple tissues:
    • epidermis external tissue
    • gastrodermis internal tissue
  • named after having cnidocytes (stinging cells)
    • they release structures called nematocysts that contain poison and barbed threads that cause pain and incapacitate the victim (ouch)
  • digestion:
    • uses extracellular digestion meaning that food is processed outside of cells
    • gastrovascular cavity cavity in middle of body where food is broken down and absorbed
    • has an incomplete gut meaning food and waste enters and exits through the same opening
  • can have 2 major body plans:
    • polyp sessile with basal disc with an upward-pointed mouth surrounded by tentacles
    • medusa free-floating with downward-pointing mouth in a bell-shaped body
    • some cnidarians have only one form, while others have both a polyp and medusa stage
• Subkingdom Bilateria
  • all animals except sponges, cteophores, and cnidarians belong to Clade Bilateria
  • Synapomorphies
    • bilaterally symmetrical
    • contains:
      • Superphylum Deuterostomia
      • Superphylum Lophotrochozoa
      • Superphylum Ecdysozoa
• Superphylum Deuterostomia
  • Synamorphies
    • united by a developmental patterns in which the anus forms before the mouth
      • it's confirmed by DNA analysis
    • includes Echinodermata and Chordata (us!)
• Phylum Echinodermata
  • includes sea stars, brittle stars, sea urchins, sea cucumbers, and crinoids
  • name comes the prickly skin most members of the phylum have
  • are bilaterally symmetrical, ancestrally
    • some look radially, but are not
  • they have:
    • water vascular system hydraulic system of water pressure that terminates in tube feet
      • tube feet flexible structures that help animals move and feed
      • madreporite an opening that regulates the entrance of water into the WVS
    • endoskeleton (inside) made of calcium carbonate
      • spines made of calcium carbonate
      • gills which aid in gas exchange
      • pathway of water: madreporite → stone canal → ring canal → radial canal → ampulla → podium
  • their body plans are funky, they have oral and aboral surfaces instead of anterior and posterior
    • oral surface where dat mouf be
    • aboral surface where the mouth ain't
• Phylum Chordata
  • includes mammals (including us!), birbs, reptiles, amphibians, fishies, and relatives
  • named for the notochord, an internal stiff, slightly flexible rod of connective tissue that supports the body and provides muscle attachment sites
    • in many extant species, this is replaced during development by vertebrae
  • are united by:
    • notochord
    • pharyngeal gill slits or openings in the pharynx
      • purpose is for gas exchange and feeding
    • muscular post-anal tail giggity. for locomotion
    • dorsal hollow nerve cord evolutionary and embryonic precursor to the CNS
• Superphylum Lophotrochozoa
  • are a superphylum because of shared sequenced DNA
  • have bilateral symmetry and true tissues
  • some members have a structure called a lophophore
    • lophophore a crown of tentacles that function in suspension feeding
  • some members have a specialized type of ciliated larva called trochophore larva
• Phylum Platyhelminthes
  • contains about 20,000 species of flatworms (flattened, soft-bodied animals)
  • have bilateral symmetry
  • simple, flattened, ribbon-like bodies
  • their flat bodies allow for easy exchange with the environment by diffusion
  • most have an incomplete gut with a gastrovascular cavity
  • does not have a coelom (body cavity) to store organs
    • the are a solid mass of cells (other than the lumen of the gastrovascular cavity)
  • does not have circulatory system
• Phylum Syndermata
  • Rotifers
    • named for their crown of cillia around their mouth, that draws in water and food
    • notable structures:
      • alimentary canal one-way digestive system from mouth to butt
      • pseudocoelom false cavity partially lined with mesoderm tissue
    • many rotifer are entirely female, reproducing asexually via parthenogenesis (like bees!)
  • acanthocephalans
    • idk, didn't learn about it
• Phylum Brachiopoda
  • commonly known as lamp shells
  • they resemble clams (mollusca), are actually not closely related
    • the shells are dorsal and ventral
  • notable structures:
    • lophophore crown of cilliated tentacles surrounding their mouth to aid feeding
    • true coelom contains their internal organs and is completely lined by mesoderm
    • pedicel fleshy stalk that attaches the animal to the substrate. makes them sessile
• Phylum Annelida
  • perfect example of metamerism (repeated similar body segments)
    • septa thin walls of tissue internally separating individual segments
  • are found in virtually every habit (fresh, salt, and land)
  • are bilaterally symmetrical with true tissues, complete gut, coelom
  • have setae, bristle-like body projections that help propel the animal
• Phylum Mollusca
  • mollusks (like gary, but not all are like gary)
  • are bilaterally symmetrical with true tissues, complete gut, coelom
  • most have a shell composed of calcium carbonate (like eggshells, or TUMS)
  • common parts are:
    • foot muscle on bottom that helps them move
    • mantle the part that creates the shell
    • radula feeding structure that helps scrap food off surface
• Superphylum Ecdysozoa
  • synapomorphies
    • animals have a cuticle (a hard external coating) that grows with the animal and is periodically shed
    • ecdysis the process of growing and shedding cuticles
• Phylum Nematoda
  • includes nematodes (or round worms that are unsegmented)
  • live in aquatic and moist terrestrial
  • most are free-living, some are parasitic
  • they have:
    • tough cuticle covering their body
    • alimentary canal (complete gut)
    • pseudocoelom
  • they don't have a circulatory system
  • all of their body wall muscles are longitudinal, leading to a "thrashing" motion
• Phylum Tardigrada
  • water bears! (tardigrades)
  • mostly live in water, but are known for being to survive extreme conditions by going into a state of dormancy.
    • they can survive in space!
    • they can survive in extreme cold!
    • they are cute!
• Phylum Arthropoda
  • name means "joint foot" (do you burn, bro)
  • appendages in serial pairs
    • jointed appendages generally used for locomotion
      • Sensory appendages or antennae
      • Feeding appendages (or mouthparts) modified appendages for feeding
  • segmented bodies
  • rigid exoskeleton made of chitin (a protein)
  • alimentary canal (complete gut)
  • coelem body cavity
    • adult arthopod's coelom is replaced by a different cavity called the hemocoel
  • an open circulatory system circulatory fluid is only partially enclosed in vessels
    • hemolymph circulatory fluid of an open circulatory system (found in anthropods)
    • hemolymph is pumped into the hemocoel through short vessels, where it bathes the organs

Chordate Diversity

• Phylum Chordata

  • named for the notochord, an internal stiff, slightly flexible rod of connective tissue that supports the body and provides muscle attachment sites
    • in many extant species, this is replaced during development by vertebrae
  • Synapomorphies:
    • notochord
    • pharyngeal gill slits or openings in the pharynx
      • purpose is for gas exchange and feeding
    • muscular post-anal tail giggity. for locomotion
    • dorsal hollow nerve cord evolutionary and embryonic precursor to the CNS

• Subphylum Cephalochordata

  • commonly called the lancelets
  • are the first group to diverge from other chordates
  • they retain all 4 chordate synapomorphies
  • composed of a few marine burrowing animals that are suspension feeders
    • suspension feeders they grab particles of food out of the water using fleshy cirri around the mouth
      • buccal cirri mouth dingledangles
  • they burrow into the sand using their muscular post-anal tail

• Subphylum Urochordata

  • commonly called tunicates
  • named because of their tails
  • adults look superficially different from Phylum Chordata
    • larvae have all 4 synapomorphies
    • adults only have 1, the pharyngeal gill slits
  • larvae are:
    • free-swimming
  • adults are:
    • sessile and stay attached to the ocean bottom
    • filter feeders
    • tunic thick tissue coating

• Subphylum Vertebrata

  • Chordates with a head and brains protected by a skull
  • Synapomorphies:
    • vertebral elements outgrowths from the notochord that enclose and protect the dorsal hollow nerve cord
    • heart with 2+ chambers
    • erythrocytes with hemoglobin
    • kidneys to filter blood
  • are more active than lancelets and tunicates

• Class Myxini

  • Hagfishes
    • synapomorphies:
      • a skull of cartilage
      • no jaws, but palps
      • gills
      • notochord for their entire life
    • are limited to small and soft decomposing food because of their fleshy mouths
    • defends itself with pores that connect to slime-glands that excrete a substance when attacked, creating a slime when combined with sea water. The slime clogs up the gills of the attacking fish and the attacker lets go and tries to deal with the clogged gills

• Class Petromyzontida

  • The Lampreys
    • synapomorphies:
      • cartilaginous skeleton
      • lack jaws
      • notochord
      • vertebral elements in the form of cartilaginous projections associated with the notochord that partially protect nerve chord
    • due to lack of jaw, they feed on living fish by latching on and sucking the blood (vampire fish!). mouth is stuff of nightmares Gnothostoma- Everything under this point has shared traits

• Clade Gnathostomata

  • (everything under this point has shared traits)
  • synapomorphies:
    • jaws broadened variety of food able to be eat
    • mineralized skeleton
      • ancestors have bony, mineralized skeleton
      • some members have secondarily lost the mineralized skeleton and returned to cartilage
    • diversity in fins
      • median fins unpaired fins along the midline of body. help with stability
        • dorsal top
        • anal bottom rear
        • caudal butt
        • paired fins help with steering
          • pectoral booby
          • pelvic bottom front

• Class Chondrichthyes

  • cartilage fishies
    • sharks, rays, chimeras, and their relatives
    • skeleton is mostly cartilage, but this is derived trait
      • ancestors had bones

• Clade Osteichthyes

  • gnathostomes with a skeleton that is primarily mineralized skeleton

• Class Actinopterygii

  • ray finned fishes
    • many different feeding and reproductive strategies
    • huge variation in sizes
      • smallest: 1cm long
      • largest: 17m long
    • synapomorphies:
      • fins composed of repeated bony elements covered by skin.
        • there is no muscle in the fins, only at the base where the fin attaches to the body

• Clade Sarcopterygii

  • Lobe-fins
    • fins have pattern of bones similar to tetrapod limbs
      • bones are covered by muscles

• Class Actinistia

  • The Coelacanths
    • Abundant during the Mesozoic era
    • thought to have gone extinct during the Cretaceous/Paleogene mass extinction, but they are just really good at playing hide-and-seek
    • live in the deep ocean
    • Very few extant species
    • CHONKY FINS
    • Rediscovered by Dr. Marjorie Courtenay-Latimer (1907-2004)
      • naturalist and curator at east london museum
      • had a relationship with fisherman at the docks to let her know if they caught any fish out of the ordinary. They caught a coelacanth, she freaked out, they named one after her and the river it was found in because she was a freakin' boss.
      • latimeria chalumnae

• Class Dipnoi

  • the lungfishes
    • about 6 know extant species currently, were more diverse in Mesozoic era
    • synapomorphies:
      • muscular fins
      • lungs
        • can breath air to supplement breathing through gills (look at you, hannah montana)
      • gills
      • radiant cuteness
    • tend to live in lands and ponds that sometimes dry up

• Tetrapods

  • synapomorphies:
    • four footed or four legged with digits
    • bones of the pelvic girdle fuse to vertebral column
      • this transfers strike force to rest of body
  • Transition of vertebrates onto land
    • the following changes can be observed in transitional fossils:
      • limbs with digits
      • loss of opercular bones
        • operculum the bone that covers the gills in fishies (shown in blue above)
      • gain of the atlas, the first cervical vertebrae to move the head
      • eyes move toward the top of the skull
    • tiktaalik roseae one of the earliest fossils with tetrapod characteristics
      • had fish-like traits, but also tetrapod traits
      • had neck, flat skull, and eyes on top of skulls

• Class Lissamphibia

  • synapomorphies:
    • 4 digits on forelimb (if present)
    • glands in skin (secretes mucous (for aiding gas exchange) or poison)
    • fat bodies (store energy)
  • Amphibian Reproduction
    • external reproduction
    • eggs are jelly coated with no hard shell. will collapse under force of gravity
      • must occur in body of water
    • amplexus a mating behavior in frogs and toads where a male clasps a female from behind with his front legs, enabling them to release sperm and eggs close together for external fertilization (seen below)

• Clade Amniota

  • extinct members are marked with dagger
  • less tied to water than any above animals, allowing them to live in more diverse places
  • synapomorphies:
    • amniotic egg doesn't have to be in water, it's got all ya need insiiiide
      • shell hard outside that prevents egg collapsing from gravity and provides protection from elements
      • series of membranes function in getting stuff into and out of the egg
        • amnion a fluid filled cavity that surrounds the embryo and protects it from mechanical shock
        • yolk sac contains stockpile of nutrients for embryo. blood vessels transport nutrients between yolk and embryo
        • allantois sac for the disposal of metabolic wastes. also involved in gas exchange between embryo and air
        • chorion exchanges gas between embryo and air outside the shell

• Clade Reptilia

  • synapomorphies:
    • fenestrae a pair of holes on each side of the skull behind the eye socket
  • Monophyletic Group Archosaurs include crocodilians (alligators and crocodiles) and birds
    • have: Fenestrae in skull (make the skull lighter) teeth in socked ridge in femur

• Class Crocodylidae

  • big ol flat heads with bi ol bite force

• Class Aves

  • BIRBS
    • are related to archosaurs because the scales on their feet and their feathers, which are modified scales (both are made of keratin)
    • ancestors might have had teeth, but was secondarily lost (not proven)
      • Archaeopteryx bird thing with teefs

• Monophyletic Group Lepidosauria

  • consists of lizards, snakes
    • smaller and lighter skull than crocodiles
      • have: overlapping scales shed in flakes tail autonomy (ability to lose one's tail and be cool with it) hemipene (split intromittent reproductive organ)

• Class Testudines

  • phylogenetic position uncertain until recently because:
    • they lack holy skulls.
      • early fossils show that they once had skull openings like other reptiles, but they have since evolved out of them
      • genomic studies have found that they are probably more closely related to archosaurs than Lepidosauria

• Class Mammalia

  • have: hair to retain body heat TEETS (mammary glands)
    • Subclass Monotremata
      • mammals that lay eggs
      • consist of platypus' and echidnas
        • they lack nipples, but have glands on belly
    • Subclass Metatheria
      • marsupials
        • give birth, but are born very early in development. the baby travels from birthing canal to pouch where they finish development
          • they have nipples
    • Subclass Eutheria
      • placental mammals
        • have a longer gestation period
          • they finish development inside the womb
      • E