exam 3 (review slides) Flashcards
binomial nomenclature
- naming system for organisms where each gets two names - a genus and a species
- introduced by carolus Linnaeus in the 18th century
taxonomic group order (binomial nomenclature) - is bolded on the slides
domain → kingdom → phylum → class → order → family → genus → species
- like a postal address identifying a person in a particular apartment
phylogenetic trees + sister taxa
- represents hypothesis about evolutionary relationships
- each branch point: represents divergence of 2 evolutionary lineages from a common ancestor
sister taxa: groups that share an immediate common ancestor that is not shared by any other group (sisters- closely related)
- there is a sister group associate with each branch point in a tree
homologies & morphology
homologies: similarities between organisms because they share a common ancestor
morphology: organisms with similar morphology or DNA sequence are likely to be more closely related than those that are vastly different in structure and sequence
homology vs analogy + example
homology: similarity due to shared ancestry
analogy: similarity due to convergent evolution
- unrelated species evolve superficial similarities through convergent evolution in response to natural selection to similar environmental conditions (was bolded)
- ex. austrailian “mole” and African golden mole - both resulted from adaption to similar lifestyles, not shared ancestry (also bolded)
monophyletic vs. paraphyletic vs. polyphyletic groups
monophyletic (clade): consists of the ancestor and all of its descendants
- everyone is direct line of descendant
paraphyletic: consists of an ancestral species and some, but not all, descendants (common ancestor to all members if part of the group)
- family reunion where some cousins are missing
polyphyletic: includes distantly related species grouped together because they have similar traits (most recent common ancestor is not part of the group)
- everyone in the group just has blue eyes
outgroup vs. in-group species
in group: main focus of the study or the comparison
- main characters of the story
outgroup: used for comparison but aren’t the main focus
- used to help understand evolutionary relationships with the in-group species
- they compare traits and characteristics between the in-group and outgroup to figure out how they’re related
how is the point at which characters were derived determined?
characters: traits or features
by comparing members of the ingroup with each other and the outgroup (bolded)
- characters shared by the outgroup and ingroup are assumed to be ancestral
- each derived character is assumed to have arisen only once in the ingroup
molecular clock
an approach used to estimate the absolute time of evolutionary change
- measures time in terms of genetic changes instead of hours or minutes
- by comparing genetic differences between species, scientists can estimate how long ago they shared a common ancestor
how are molecular clocks calibrated (set starting point)?
by graphing the number of genetic differences in a gene against dates of branch points known from the fossil record
limits to the molecular clock approach (not bolded but seemed important)
- some genes evolve in irregular bursts, rather than clocklike precision
- rate of evolution deviates from the average periodically, even in reliable clocklike genes
- same gene may evolve at different rates in different taxa
- some clocklike genes evolve at dramatically different rates from each other
taxa
taxonomic rank
- categories or groups that scientists use to organize and classify living things based on their similarities and evolutionary relationships
how horizontal gene transfer plays an important role in tree gene disparities
horizontal gene transfer: genes transfer “sideways” instead of down, so not parent to offspring but one genome (complete set of DNA in one organism) to another
- can occur by exchange of transposable elements (nucleic acid sequence in DNA that can change its position within a genome) and plasmids, viral infection, and possibly fusion
- disparities between different trees may results from movement of genes between the domains (major groups of life- genes jumping around between different type of organisms)
virus (parts + classification)
virus: very small infectious particle consisting of:
- nucleic acid enclosed in protein coat
- in some cases, a membraneous envelope
classified as DNA viruses or RNA viruses
viral genomes can have either double or single stranded DNA or RNA
capsid
protein shell that encloses the viral genome (genetic material)
- it protects the DNA
- tobacco mosaic viruses have helical capsid (rod shape)
- adenoviruses have circular capsid with protein spike at each corner
bacteriophages
also called phages
- viruses that infect bacteria
- look like those robot bots like the cookie from despicable me
viral envelopes
disguise for the virus
derived from membranes of host cells
- contain host cell phospholipids and membrane proteins
- surround capsids of influenza viruses and many other viruses found in animals
viral replicative cycle
- virus enters cell and is uncoated, releasing viral DNA and capsid proteins
- host enzymes replicate the viral genome
- meanwhile, host enzymes transcribe the viral genome into viral mRNA, which host ribosomes use to make more capsid proteins
- viral genomes and capsid proteins self-assemble into new virus particles, which exit the cell
other bolded info:
- viral infection begins when a virus binds to a host cell and the viral genome makes its way inside
- once a viral genome has entered the cell, cell begins to manufacture viral proteins
- viral nucleic acid molecules and capsomeres (make up capsid) spontaneously self-assemble into new viruses
2 alternative reproductive mechanisms for phases (lytic vs. lysogenic)
lytic: “attack and conquer”, virus infects cell and takes over machinery to make more viruses, kills host cell (bursts open to release progeny phages)
- production of new phases
lysogenic: “sneaky sleeper agent”, instead of immediately taking over and destroying, virus hides in the genetic material inside cell’s DNA, doesnt kill host cell
- but can later become lytic, but stays hidden for a while
- genome integrates into bacterial chromosomes as prophage, which is either replicated and passed to daughter cells or induced to leave the chromosome and initiate lytic
virulent vs temperate phage
virulent: phage that reproduces only by the lytic cycle
temperate: phages that use both lytic and lysogenic cycles
- called lambda and is widely used in biological research
- every time host divides, it copies phage DNA and passes to daughter cells
- environmental trigger can cause it to switch to lytic
bacterial defenses against phages (after having survived an infection)
- cell can block attempts of the same type of phage to reinfect it
- CRISPR region in DNA of cell gets activated when the virus tries to infect again → CRISPR region produces special RNA molecules
- RNA molecules produced by CRISPR are cut into pieces and bound to cas proteins
- the cas proteins go around with the RNA pieces to find and target the genetic material of the invading virus
- once phage identified, cas proteins cut up and destroy genetic material of the virus, preventing it from hurting the cell
viral envelopes
- viral glycoproteins on envelope bind to specific receptor molecules on surface of a host cell
- viral envelope usually derived from host cell’s plasma membrane as the viral capsids exit (wears the cells clothing as disguise as it leaves)
- other viral membranes form from host’s nuclear envelope and are then replaced by an envelope made from golgi apparatus membrane
- ex. herpes virus
retroviruses
instead of going straight to work as soon as they infect a cell, they turn their RNA into DNA
- even though most organisms store their genetic material as DNA, retroviruses store genetic info as RNA
- uses reverse transcriptase to convert its RNA into DNA which becomes part of the host cell’s genetic material
ex. HIV (human immunodeficiency virus) - retrovirus that causes AIDS
provirus
when a retroviruses’ (or any virus)’s
DNA becomes part of the host cell’s DNA
- retrovirus stashes its blueprint inside host cell’s genetic library = becomes permanent resident
- can stay dormant or become active and start making new virus particles
(what makes retroviruses so hard to treat)
on slide:
- RNA polymerase transcribes proviral DNA into RNA molecules
- RNA molecules function both as mRNA for synthesis of viral proteins and as genomes for new virus particles released from the cell
emerging viral diseases
- illnesses caused by viruses that are novel to humans to have undergone significant changes that make them more virulent or capable of spreading rapidly
- influenza is one cause it mutates rapidly
- normal seasonal flu viruses are not considered emerging viruses because variants of them have been circulating among humans for a long time
- however, those viruses still undergo mutations and reassortment
- variations thought to be most likely o occur each year are selected to generate vaccines
high rate of mutation in influenza viruses
influenza viruses have 9 RNA segments in their genome = lots of different genetic parts that can mix and match = high rate of mutation
- emerging virus
3 shapes of prokaryotic cells
spheres (cocci): round little balls, can be found alone, in pairs, or groups that look like a bunch of grapes
rods (bacilli): usually found alone, shaped like rods or sticks
spirals: include spirochetes, which are cork-screw shaped
- others resemble commas or loose coils
gram-positive vs. gram-negative bacteria
- scientists use the gram the stain to classify bacteria by cell wall composition
gram-positive bacteria (purple-pink): simpler cell walls made up of a thick layer of a substance called peptidoglycan
gram-negative bacteria (red): more complex cell walls with outer membrane that consists of lipopolysaccharides
(LPS) and less peptidoglycan
- tend to be more resistant to antibiotics than gram-positive bacteria
prokaryotic cell surface structures + 3 functions
many prokaryotes have a sticky layer of polysaccharide or protein surrounding cell wall
- called capsule if dense and well-defined - called slime if it is not well organized
function of both types:
- enable adherence to substrate or other individuals (glue)
- prevent dehydration
- protect pathogenic prokaryotes from host’s immune system
fimbriae vs. pili
fimbriae: some prokaryotes have these hairlike appendages that allow them to stick to their substrate or other individuals in a colony
pili (or sex pili): longer than fimbriae, function is to pull 2 cells together enabling the exchange of DNA from 1 cell to another
endospores in bacteria
- when conditions like lack of water or nutrients threatens survival of certain bacteria, they form special structures called endospores
- original bacteria cell copies its genetic info (chromosome) and wraps it in layers of protection to form endospore (puts genetic material into protective shell)
- endospore loses water and becomes dormant (metabolism halts), meaning all its activity stops (kinda like hibernation)
- original cell dies, releasing the endospore
- endospores can withstand extreme conditions and can remain viable for centuriesss!!! until conditions are favorable again
flagella
- most common structures used by prokaryotes for movement
- may be scattered over entire surface or concentrated at the ends of the cell
difference in flagella of eukaryotes and prokaryotes
- differ in structure, mechanism or propulsion, and molecular composition
indicates flagella in prokaryotes and eukaryotes arose independently
internal organization and DNA of a prokaryote
- prokaryotes lack a nucleus
- chromosome is in the nucleoid (a region of cytoplasm not enclosed by a membrane)
- have plasmids: smaller rings of independently replicating DNA
genetic recombination in prokaryotes + ways it happens
genetic recombination contributes to prokaryotic diversity (combining of DNA from 2 sources)
in prokaryotes, genetic recombination happens by:
- transformation
- transduction
- conjugation
- horizontal gene transfer (movement of genes between individual prokaryotes of different species)
3 factors that contribute to high levels of genetic diversity in prokaryotes
- rapid reproduction
- mutations
- genetic recombinations
mutations in prokaryotes
- cells produced by binary fission (split into 2 identical cells) are usually identical, but differences can arise through mutations
- mutation rates are typically low but mutations accumulate rapidly since bacteria reproduce quickly and in large numbers
- individuals that are genetically better equipped for environment survive and reproduce at higher rates than other individuals
rapid production of genetic diversity = rapid adaptation by natural selection
transformation & transduction in bacteria
transformation: bacteria incorporate foreign DNA taken up from their surroundings- could result in new traits
transduction: virus acting as a delivery service for genetic material, phages accidentally incorporate DNA from one bacteria into themselves and then inject that when they infect the next bacteria
conjugation
- bacterial mating
- 2 bacteria come together and form a physical bridge between them called a pilus - this bridge transfers genetic material between them
- involves piece of DNA called plasmid which carries extra genes that can provide benefits
- in bacteria, DNA transfer is always one way: one cell donates the DNA and the other receives it
3 steps of conjugation in E. coli
- Pilus of the donor cell attaches to recipient
- Pilus retracts, pulling the 2 cells together
- DNA is transferred through a temporary structured called the “mating bridge”
the F factor
a piece of DNA called F factor (F for fertility - helps in reproduction) is required for the production of pili
- can either be in a plasmid or in the chromosomes
F factor in the plasmid
F+ cells: have the F plasmid, act as donors of DNA during conjugation
F- cells: dont have the F factor, act as recipients of DNA
- an F+ cell can convert an F- cell to an F+ cell if it transfers an entire F plasmid to the F- cell
- if only part of the F plasmid’s DNA is transferred, the recipient cell will be recombinant
F factor in the chromosomes
if they have F factor in the chromosomes, they get called Hfr cells (high frequency of recombination) are donors during conjugation
- higher frequency of recombination during conjugation because they transfer not only the F factor, but also some of their DNA = genetic recombination
nitrogen fixation
- good thing that prokaryotes do
- convert atmospheric nitrogen (N2) to ammonia (NH3)
- great impact on environment: increases nitrogen available to plants, which cannot use atmospheric nitrogen but can use ammonia
metabolic cooperation in cells
ex. filamentous cyanobacterium Anabaena
teamwork among bacteria cells, where different cells work to perform tasks that they couldn’t do alone
in Anabaena: cells are specialized for nitrogen-fixation or photosynthesis
- heterocysts that prevent oxygen penetration are specialized for nitrogen-fixation
- photosynthetic cells exchange carbs for the fixed nitrogen produced by the heterocysts
cyanobacteria + evolutionary significance
only prokaryotes with plantlike, oxygen-generating photosynthesis
believed that plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis (endosymbiosis = one organism engulfed by another but forms beneficial relationship with host)
extremophiles
archae that live in extreme environments, uninhabitable for most organisms
archae = group of single-celled microorganisms similar to bacteria but have distinct genetic characteristic, often found in extreme conditions, like salty places and high temps
exotoxins vs. endotoxins in pathogenic bacteria
exotoxins: toxins produced inside bacteria and released into surroundings that can cause disease
endotoxins: toxins found within the cell walls of certain types of bacteria that only release when the bacteria die and cell wall is broken down
- lipopolysaccharide components of the outer membrane of gram-negative bacteria
role of horizontal gene transfer in creating pathogenic bacteria
- horizontal gene transfer can spread genes associated with virulence (danger) to normally harmless bacteria
- ex. E. coli used to live peacefully in our intestines but then got harmful gene from pathogenic bacteria and now became dangerous and can cause illness
mitochondria and plastids in evolution
mitochondria and plastids are derived from bacteria that were engulfed by ancestors of early eukaryotes
evidence suggests mitochondria (invited in first) evolved before plastids
- arose from alpha proteobacterium
plastid evolution
arose later when a heterotrophic eukaryote engulfed a photosynthetic cyanobacterium
plastids = double membrane organisms that manufacture and store food for the plant
excavata (protists)
includes 3 clades (group of organisms from common ancestor):
parabasalids: also has reduced mitochondria and mostly live in anaerobic conditions, best known is Trichomonas vaginalis, a sexually transmitted parasite
diplomonads: typically lack mitochondria, have a mini version called mitosomes
- lack electron transport chains so energy is derived from anaerobic pathways
- many are parasites like Giardia intestinalis which causes intestinal infections in mammals
euglenozoans: often found in aquatic environments
- kinetoplastids: some species parasitize animals, plants, and other protists. ex. members of genus Trypanosoma infest humans, causing sleeping sickness
SAR (protists)
includes 3 large clades: stramenopilia, alveolata, and rhizaria
-ex. diatoms are important photosynthetic stramenopiles
archaeplastida (protists)
- includes red and green algae and plants
- red and green algae include unicellular, colonial, and multicellular species
protists: SAR: stramenopiles
most stramenopiles have a “hairy” flagellum paired with a shorter “smooth” (nonhairy) flagellum
diatoms: unicellular algae with a unique, two part, glass like shell of silicon dioxide (protests diatoms from crushing jaws of predators)
brown algae: most are marine, including many species commonly called “seaweeds”
- some have gas-filled, bubble shaped floats to keep photosynthetic structures (leaflike blades) near the water surface (bolded)
alternation of generations in multicellular algae
- variety of life cycles have evolved among multicellular algae = most complex is alternation of generations
- diploid = sporophyte, haploid = gametophyte
heteromorphic species, such as Laminaria have structurally different gametophytes and sporophytes
= means that the two stages look so different that it looks like different plants, but its not
protists: SAR: the 3 clades of alveolates
3 clades included in the alveolates:
- dinoflagellates
- apicomplexans
- ciliates
protists: SAR: Alveolates: Apicomplexans
nearly all apicomplexans are parasites of animals - they spread through host as infectious cells called sporozoites
steps:
1. infected mosquito bites a person, injecting sporozoites in its saliva
- sporozoites enter the person’s liver cells. after several days, the sporozoites undergo multiple mitotic divisions and become merozoites, which use their apical complex to penetrate red blood cells
- merozoites divide asexually inside red blood cells and at 48-72 hour intervals, large numbers break out of cells, causing chills and fever
- some merozoites form gametocytes
- another mosquito bites the infected person and picks up the gametocytes along with blood
- gametes form from gametocytes, each male produces several slender male gametes
(rest not boxed) but then fertilize inside mosquito and become babies that go into mosquitos saliva and keep spreading
protists: SAR: Alveolates: Ciliates
named for their use of cilia to move around and feed on bacteria or other protists
filled with cilia that may completely cover the cell surface or be clustered in a few rows or tufts
protists: SAR: Rhizarians
most species of rhizarians are amoebas
amoebas: protists that move and feed using psuedopodia (extensions of the cell surface)
3 clades of rhizarians:
- radiolarians
- forams
- cercozoans
protists: SAR: Rhizarians: Forams
Forams (also called Foraminiferans) are tiny ocean creatures that are named for their porous (has little holes) calcium carbonate shells called tests
closest relative of plants
are red algae and green algae
- plastids arose when a heterotrophic protist acquired a cyanobacterial endosymbiont
idek how this is different from the other one but its bolded on the slide so
protists: archaeplastida: red algae
reproduction is sexual in red algae and life cycles often include alternation of generations
- do not have flagellated gametes so depend on water current to bring gametes together for fertilization
red algae are common in coastal waters of tropical oceans
(all bolded)
Unikonta: Ameobozoans
- are amoebas that have lobe- or tube shaped, rather than threadlike, psuedopodia
they include:
- tubulinids
- slime molds
- entameobas
symbiotic protists examples
symbiosis = close and long-term interaction between 2 different species
- some parabasalids inhabit the guts of termites and aid with the digestion of wood
- some protists symbionts are parasites like plasmodium causes malaria in humans
hyphae & mycelium in fungi
hyphae: tiny thread like filaments that make up structure of fungi
- hyphae have tubular cell walls around them made of chitin
mycelium: dense, tangled web of hyphae spreading through the soil
- network for the fungus to explore and feed on its food source (decomposing organic matter) - they’re like tentacles that go out and explore
mycorrhizae + 2 types
mutually beneficial relationships between fungi and plant roots
2 main types:
ectomycorrhizal fungi: fungus forms sheath (covering) of hyphae around tree’s roots and together they exchange nutrients
arbuscular mycorrhizae fungi: instead of blanket, more like fungus is inside of the tree’s roots, forming structures called arbuscules helping tree absorb nutrients
most vascular plants depend on mycorrhizae
- fungi colonizes soil by dispersal of spores
sexual reproduction in fungi
plasmogamy: a hug, cytoplasm of 2 parent mycelia comes together allowing them to share resources and genetic material
- heterokaryon: type of fungal cell that contains 2 or more genetically distinct nuclei within a single cytoplasm, happens when cells hug but dont do the rest yet (karyogamy)
karyogamy: the more intimate part, haploid nuclei fuse, genetic material combines bringing together DNA producing diploid cells (zygote)
the short-lived diploid cell undergoes meiosis, producing haploid spores (“sexual spores”)
steps from the red box:
plasmogamy → heterokaryotic stage → karyogamy → meiosis → germination → mycelium → asexual starts now spore-producing structures → germination
asexual reproduction in fungi
molds: produce haploid spores asexually by mitosis and form visible “furry” mycelia (early stages of mycelial growth)
single-celled yeasts reproduce asexually without producing spores
fungi: chytrids vs zoopagomycetes
chytrids: type of fungi that produce flagellated spores called zoospores that help it move in water
zoopagomycetes: another type of fungi that grow as hyphae and reproduce asexually by making spores without flagella
zygosporangium
when fungi like zoopagomycetes and mucoromycete want to reproduce sexually, they form this durable structure called a zygosporangium
- houses and protests the zygote
mucoromycetes and zygosporangium
- when conditions are tough, mucoromycetes form a zygosporangium
- when conditions get better, meiosis occurs and zygosporangium germinates into a sporangium
- sporangium releases genetically diverse haploid spores
fungi: ascomycetes + sexual and asexual stage
- 25% of them have symbiotic associations with green algae or cyanobacteria called lichens
- often called “sac fungi” because have sac-like structures called asci where they make spores
- sexual stage: produce fruit bodies called ascocarps that contain spore-forming asci
- asexual stage: enormous numbers of asexual spores called conidia are produced
fungi: basidiocarps
fruiting bodies of basidiomycete fungi (they’re like the mushrooms you see above ground)
ex. common white mushrooms found in supermarkets are basidiocarps
mushroom results from a concentrated growth of hyphae that forms from a dikaryotic mycelium (2 nuclei in each cell instead of one)
lichens
symbiotic associations between photosynthetic microorganisms and fungi
- photosynthetic partners are unicellular green algae or cyanobacteria and fungal partners are most often ascomycetes
choanoflagellates
protists that are considered closest living relatives to animals
- the common ancestor may have resembled modern choanoflagellates
ectoderm, endoderm, diploblastic animals, and triploblastic animals
ectoderm: outermost layer of cells that forms the skin and the nervous system (top layer of bread)
endoderm: innermost layer of cells that lines blind pouch (archenteron) that forms gut and digestive system (bottom layer of bread)
diploblastic animals: have only ectoderm and endoderm (simple sandwich with only 2 layers)
- cnidarians
triploblastic animals: in addition to ectoderm and endoderm, also have mesoderm which gives rise to muscles and most organs (fancy sandwich)
- all bilaterally symmetrical animals
cleavage patterns in animals with protostome and deuterostome development
protostome
- spiral cleavage: cell divides in spiral pattern, creating spiral arrangement of cells
- determinate cleavage: cutting with cookie cutter, shape is as is, determined very early
deuterostome
- radial cleavage: stacking building blocks on top of one another, cell divides in way that creates layers, each one directly above
- indeterminate cleavage: dividing clay into smaller parts, but each part has potential to become something else, fate of cell is not determined
- idk if u need to know the definitions of all, they’re not bolded but need to know the classifications for sure
blastopore in protostome and deuterostome development
blastopore = indentation in the gastrula that leads to the formation of the archenteron (forms the gut)
protostome: blastopore becomes the mouth
deuterostome: blastopore becomes the anus
Eumetazoa & Bilateria (diversification of animals)
Eumetazoa: clade of animals that has tissue, like muscles and nerves
- most animals fall into this group except sponges and a few others
Bilateria: subgroup of Eumetazoa
- includes animals that have bilateral symmetry (can be divided into 2 equal halves) and have 3 germ layers (ecto, meso, endo)
3 clades of bilaterians
bilaterians = animals that have bilateral symmetry
1. deuterostomia: may be invertebrates or vertebrates
2. ecdysozoa: all invertebrates that have exoskeleton that sheds as they grow
- includes: nematodes and arthropods
3. Lophotrochozoa: more diverse group that includes animals that may have lophophores (used for feeding), like ectoprocts or trochophore larvae (early-stage larvae), like mollusks (snail) and annelids (worms)
cnidarians + medusozoans and anthozoans (invertebrates)
group of animals that live in water, mostly in oceans
- creatures like corals, hydras, jellyfish
- defining characteristic is stinging prey
- diploblastic with radially symmetrical bodies
medusozoans: all cnidarians that produce a medusa (spent most of their time in jellyfish-like form)
- scyphozoans (jellies)
- cubozoans (cube jellies)
- hydrozoans (hydra)
anthozoans: mostly stay anchored to the sea floor
- corals: can be solitary or colonial, form symbioses with algae, and secrete a hard exoskeleton of calcium carbonate
Lophotrochozoans: Molluscs parts (invertebrates)
THEYRE SNAILS BRUH
muscular foot: usually used for movement
visceral mass: contains most of internal organs
mantle: fold of tissue draping over visceral mass that secretes the shell
radula: scrapes up food, for feeding
- many mollusks have ciliated larval stage called the trochophore
lophotroschozoans: annelids (invertebrates)
- segmented words
- have a coelom
- now divided into 2 clades:
errantia and sedentaria
sedenteria = leeches
leeches
sedenteria of annelids
- some slit the skin of their host and secrete anesthetic to prevent detection
- secretion of hirudin prevents coagulation, enabling them to gorge on the host’s blood
ecdysozoa: arthropods (invertebrates)
- insects, lobster, crayfish, spiders
- body consists of segmented body, hard exoskeleton, and jointed appendages
- have open circulatory system that uses heart to pump hemolymph into cavity surrounding the tissues and organs (the hemocoel)
3 major lineages that diverged early:
- chelicerates (sea spiders, horseshoe crabs, scorpions, ticks, mites, and spiders)
- myriapods (centipedes and millipedes)
- pancrustaceans (insects, lobsters, shrimp, barnacles, and other crustaceans
(all these examples were bolded)
chordates (vertebrates)
all chordates share a set of derived characters, but they may appear only during early development
4 key characters:
- notochord: flexible rod that runs along back of animal, provides support and structure
- dorsal, hollow nerve cord: bundle of nerves that eventually develops into brain and spinal cord
- pharyngeal slits or clefts: openings in throat area (pharynx) that connect to outside world
- muscular, post-anal tail: tail bruh
Ancestral chordates likely resembled lancelets (like fish but lack jaws and obvious organs, just like a line), which retain all key chordate traits as adults
amniotes (vertebrates)
tetrapods whose living members are the reptiles (including birds) and mammals
- named for amniotic egg which contains 4 membranes that protect embryo
- key adaptation for life on land = amniotic off reduced dependance on water for reproduction
