unit 1

how many vertebrate species currently inhabit the earth?

\~73,400

what group makes up nearly half of all vertebrate species?

fish

when did the first vertebrates appear?

500 million years ago

what are the four characteristics of chordates?

notochord; dorsal, hollow nerve cord; pharyngeal slits; postanal tail

what is the function of the notochord?

body support

what do more derived vertebrates have in terms of the notochord?

a vertebral column - only remnants of the notochord exist (intervertebral disks)

what do other animal phyla (not chordates) have instead of dorsal hollow nerve cord?

solid nerve cords located ventral to the gut.

what are pharyngeal slits?

perforations in wall of pharynx that open to outside of body

what is the function of pharyngeal slits? (originally and in more derived species)

originally used for filter feeding, modified for gas exchange and other functions.

what is the function of the postanal tail? (originally and in more derived species)

originally used for locomotion in water, modified for locomotion on land or lost.

what are the 3 main subgroups in phylum chordata?

urochordata, cephalochordata, craniata

describe subphylum cephalochordata

lancelets or amphioxus - tiny eel-like marine animals, adults present all chordate characteristics, no backbone

describe subphylum urochordata

tunicates or sea squirts - sessile marine animals, attach to rocks and filter feed. adults do not resemble a chordate - have a tadpole larval stage with all 4 chordate characteristics.

describe craniata

same characteristics as other chordates, plus: pronounced cephalization (distinct brain encased in skull (cranium)), vertebral column that encloses nerve cord.

where did vertebrate arise from?

cephalochordates or the larval form of urochordates.

what is paedomorphosis?

the retention of larval characteristics into adulthood.

what are the key features of vertebrates?

endoskeleton, link between pharynx and breathing, well developed nervous system, paired limbs

what is the benefit of an endoskeleton?

provides protection, accommodates growth better than exoskeleton.

what is the benefit of a link between pharynx and breathing?

more active lifestyle

what is the benefit of a well developed nervous system?

high degree of cephalization - brain and sense organs

what is the benefit of paired limbs?

improved locomotion

describe the group cyclostoma (‘agnatha’)

jawless fishes - hagfish and lamprey. jawless vertebrates with cartilaginous skeletons. marine and freshwater. notochord persistent into adulthood. lack paired appendages.

describe the superclass gnathostomata

vertebrates with hinged jaws. marine and freshwater. notochord replaced by vertebrae in adults in most species. paired appendages.

what are chondrichthyes?

cartilaginous fishes

what are osteichthyes?

bony fishes

what are amphibia?

frogs, toads, salamanders

what are reptilia?

snakes, lizards, turtles, crocodiles

what are aves?

birds

what are mammalia?

mammals

what are the “major transitions” in vertebrates in order?

jaws, lungs (+ derivatives), limbs, amniotic egg

what is systematics?

the scientific study of the kinds and diversity of organisms and their evolutionary relationships. involves describing, naming, and classifying organisms

what is taxonomy?

discipline in charge of providing names for groups of organisms and establishing rules by which organisms are named.

who founded taxonomy?

aristotle

who do we get modern taxonomy from? include what year and in what work.

carolus linnaeus, 1735, in systema naturae

what is binominal nomenclature?

every organism is assigned a two part name - 1st word genus, 2nd word species.

order of taxonomy

kingdom, phylum, class, order, family, genus, species

how to remember taxonomy

kevin’s poor cow only feels good sometimes

species ‘definition’

members of the same species have similar characteristics, and are reproductively isolated from other such groups.

aristotelian essentialism

species are eternal, immutable, discrete. species are classified by morphological features (blood vs no blood, nose or no nose). had an idealized form of the species - “type,” and variations were treated as deviations.

radical shift in 19th century (in species & classification)

species are not eternal or immutable. variation in nature is common and important for survival.

what was darwin’s work on natural selection called & what year?

on the origin of species, 1859

components of natural selection

1\. more individuals are born each generation than can survive and reproduce

2\. there is trait variation among individuals

3\. at least some of this trait variation is heritable

4\. trait differences are tied to fitness

is evolution by natural selection random?

no - mutations may be random, but selection is not.

what is the underlying principle of biology?

evolution by natural selection

what are the consequences for systematics?

similarities in structure imply evolutionary relationships and a tree of life describing the relationships among species.

evolutionary classification

uses the evolutionary history of organisms for classification. closely related species should have more similar characteristics.

homologous structures

similarity due to shared ancestry (ex. limbs of tetrapods)

analogous structures

similarity not from shared ancestry (convergent evolution - ex. wings of bats and birds)

phylogenetics

study of the evolutionary relationships among species

what is a taxon

a taxonomic group worthy of a name: a “set” of similar organisms.

monophyletic

contains most recent common ancestor and all descendants

paraphyletic

contains most recent common ancestor and all members of group, but NOT all descendants

polyphyletic

does NOT contain ancestor of group (i.e., group has multiple evolutionary origins)

example of monophyly

mammals, birds

example of paraphyly

reptiles

example of polyphyly

flying vertebrates

allopatric speciation

separate places

sympatric speciation

same place

types of allopatric speciation

vicariant speciation, founder effect

vicariant speciation

original population becomes separated (ex. by geographic barriers), subject to different environmental stresses and diverges via natural selection leads to reproductive isolation

founder effect

few individuals move far out of normal range and found a new population

can allopatric species become sympatric again?

yes! when sympatric again - if the populations can interbreed, speciation hasn’t occurred, but if the populations can’t, speciation has occurred.

types of sympatric speciation

ecological segregation, genetic sympatric speciation

ecological segregation

species live in the same area, but segregate relative to specific habitat types

genetic sympatric speciation

involves polyploidy - offspring getting one or more extra full sets of chromosomes. if offspring live new species can be formed. rare in vertebrates.

bergmann’s rule

endotherms tend to be larger in cold climates

allen’s rule

extremities of endotherms vary inversely with body size

gloger’s rule

endotherms living in arid regions tend to be lighter in coloration

what’s the oldest vertebrate group? (how old?)

fish, evolved around 530 mya

when were fish dominant/when was the age of fishes?

devonian

what is the most diverse vertebrate group?

fish

describe jawless fishes

jawless, no paired fins, no true vertebral column (notochord), small

what does the myxini (hagfish) eat?

decomposer, so dead/dying animals (though most of diet is marine worms)

what cool things can myxini (hagfish) do?

tie their bodies into knots, produce slime

what environment do myxini (hagfish) live in?

deep marine water

what do lampreys eat?

filter feed as larvae, adults either don’t feed or feed via parasitic rasping into fish.

what environment do lampreys live in?

all breed in freshwater, but some live in saltwater.

describe osteognathostomes

armored carapace made of bone, appeared in the devonian, no paired fins, more derived than extant cyclostomes.

major evolutionary events in gnathostomata

hinged jaws: allowed for more diverse prey types, predatory lifestyles, etc.

paired fins: increased stability for locomotion

describe placodermi

extinct group that was dominant in the devonian, often armored, jaws with teeth, pectoral fins, heterocercal tail, small to very large, speculated ties to sharks.

describe chondrichthyes

cartilaginous fish (sharks, skates, rays, chimera). cartilaginous skeleton, two sets of paired fins, heterocercal tail, placoid scales inferior (V) mouth, no swim bladder

longest-living vertebrate?

greenland shark (can live to 400 years old)

describe acanthodes

extinct group that lived during the 2nd half of the paleozoic, jaws with teeth, heterocercal tail, multiple sets of paired fins, most small

describe osteichthyes

bony fish, largest group of vertebrates, skeleton of bone, thin, overlapping scales, paired fins, swim bladder

describe actinopterygii

ray-finned fishes, fins supported by rays. 2 main subgroups - chondrostei and neopterygii

describe chondrostei

primitive bony fish, skeleton mostly cartilage (secondary bone loss), body either naked or with thick, plate-like scales, rostrum projects past mouth.

describe neopterygii

modern bony fish, most species of fish (over 32,500), incredibly diverse.

describe sarcopterygii

lobe-finned fishes. fins have fleshy base, smallest group, 2 main groups recognized (actinistia and dipnoi), precursors to tetrapods

describe coelacanths (actinistia)

common in devonian, thought to be extinct but rediscovered in 193 off coast of africa, later indonesia.

describe lungfish (dipnoi)

date to paleozoic and devonian, double breathers, 6 living species, during dry periods form cocoon, aestivate in mud, closest living relatives to tetrapods

describe the “rhipidistians”

predaceous, large, and often armored. died out shortly after devonian. ancestral precursors to tetrapods.

what is the order gymnophiona?

caecillians

what is the order urodela (caudata)?

salamanders

what is the order anura?

frogs and toads

what are the characteristics of amphibians?

terrestrial, aquatic, or both; legless and/or gilled larval stage; smooth, permeable skin; egg without shell, generally oviparous with external fertilization

what are the three hypothesis for the switch to land?

predation hypothesis, food hypothesis, competitive avoidance hypothesis

when was the age of amphibians?

carboniferous

what were the problems with moving to land life?

gravity, locomotion, breathing, feeding, reproduction, outer covering, pumping blood, sensory systems

what characteristics did the tetrapodomorphs, or the transitional fish (‘osteolepididae’; ‘rhipidistians’) have that allowed for transition to land?

double breathers, internal nares opening at back of nose connecting nasal passage to throat and lungs, well-ossifed skeleton, primitive pectoral girdle between fins and vertebral column

describe acanthostega

more aquatic than terrestrial, presence of ceratobrachials (= internal fish-like gill), fishlike vertebrae, 8 digits