CVA Exam 1

What is the difference between comparative and functional anatomy? Give examples of each.

Comparative anatomy allows us to see ourselves in a broader biological context and helps us form hypotheses to explain patterns observed in nature. An example of this is comparing muscle scars on bones. Functional anatomy focuses on form vs. function. An example of this is EMG, when a muscle is turned on vs. off.

What are the two mechanisms that Charles Darwin proposed?

1. Descent with modification

2. Natural selection

What can you compare anatomy across to explore evolution and adaptation?

Taxa

Who invented comparative anatomy?

T.H. Huxley

Adaptation is a _______ (where evolution tinkered through time) and ______ (anatomical structure)

Process, product

Evolutionary descent leads to __________.

Phylogenies

Match the term to its definition:

A. a monophyletic group that includes a single common ancestor and all of its descendants (living and extinct)

B. connects an ancestor to its descendants and represents a lineage or group of organisms changing over time.

C. Represents the most recent common ancestor of all the lineages that come off from that point

Terms: node, clade, branch

A: clade

B: branch

C: node

Differentiate between allopatric vs sympatric speciation.

What type of clade is this? Define which type of clade this is.

Paraphyletic: a clade that includes a common ancestor and some but not all of its descendants.

What type of clade is this? Define which type of clade this is.

Monophyletic: includes a single common ancestor and all of its descendants (living and extinct)

What type of clade is this? Define which type of clade this is.

Polyphyletic: a grouping of organisms who are put together based on shared characteristics but do not include a direct common ancestor.

What term goes with this definition?

• A group of individuals that descend from a common ancestor that evolved through time and possibly split.

Lineage

Does it matter if you rotate the taxa on a phylogeny?

No, because rotating it does not change the evolutionary relationships.

True or false:

• Humans evolved from chimpanzees. We do not share a recent common ancestor.

False. Humans did not evolve from chimpanzees. We’re evolutionary ‘cousins’ & share a recent common ancestor that was neither chimp nor human.

If humans did not evolve from chimpanzees, what is our shared ancestry and how did we accumulate traits during the evolution of homo sapiens?

We are evolutionary cousins who derived from a common ancestor. Over time our adaptations led to bipedalism, big teeth, bigger brains, tools, speech, etc. There was a gradual accumulation of traits and extinctions.

Match the terms with the definitions: (apomorphy, plesiomorphy, autapomorphy, synapomorphy)

A. a self-derived trait that is unique to a specific group. Can diagnose a terminal taxa. Ex: Speech in humans

B. a pre-existing ancestral trait that was present in distant ancestors. Present in outgroups. Ex: having a backbone when looking at fish

C. A shared derived trait that is shared by two or more groups or species. Can diagnose a group. Ex: presence of four limbs in tetrapods

D. A derived trait that evolved from an older ancestral form. Ex: hair in mammals

A - Autapomorphy

B - Plesiomorphy

C - Synapomorphy

D - Apomorphy

Can synapomorphies become plesiomorphies?

Yes.

What term do we use to separate derived vs. ancestral characters? Define this term.

Homology: similarity in structure, sequence, or form due to a shared ancestry or common origin.

What are the two ways we know something is a homology?

Outgroup vs ingroup and careful comparisons of embryology, anatomy, & genetics among many taxa reveal them.

Differentiate between ingroup and outgroup.

Outgroup - basis of comparison; does not have the trait.

Ingroup - has the trait; group is under study.

Define homoplasy. What is it the opposite of?

Shared trait that two or more species have in common, but which did not come from their common ancestor. It is the opposite of homology, and the traits are functionally similar, but they evolved independently.

Match the term to the statement. (homology vs. analogy)

A. traits arose independently (do not have shared phylogenic history)

B. share ancestry

A - analogy

B - homology

What are cladistics and why is it important?

Method of classifying organisms into groups called clades. It shows how traits within clades change through time. It is important so that we can re-trace the history of life.

Define parsimony.

the fewest number of steps required (means that the simplest explanation is likely the correct one.)

What group is the outgroup to Chordata?

Hemichordata

What are the big 5 Chordate synapomorphies?

Dorsal hollow nerve cord (process sensory info and coordinate movement)

Notochord (swimming)

Post-anal tail (beyond anus)

Endostyle (feeding and respiration)

Pharyngeal slits (feeding and respiration)

What are the three embryonic tissue layers that deuterostomes have?

Ectoderm, mesoderm, and endoderm.

Which of the three trait is being compared between the protostomes and deuterostomes?

Protostomes: spiral, 45 degrees, early fate

Deuterostomes: radial, 90 degrees, later fate

Cleavage

Which of the three trait is being compared between the protostomes and deuterostomes?

Protostomes: mesoderm forms as lateral cords

Deuterostomes: mesoderm forms as out pockets

Mesoderm formation

Which of the three trait is being compared between the protostomes and deuterostomes?

Protostomes: mouth develops from this

Deuterostomes: anus develops from this

Blastophore fate

Which clade do these examples of basal deuterostomes come from?

A. sea stars, brittle star, sea urchin, and sea lily

B. acorn worms (contain pharyngeal pores, also a filter feeder that lives in burrows)

C. amphioxus (lancelets - contain myomeres which are striated segments of muscle)

A. Echinoderms

B. Hemichordata

C. Cephalochordata

True or false: Hemichordata, Chordata, and Cephalochordata all have the big 5 synapomorphies.

True

True or False:

Cephalochordata (Amphioxus - Branchiostoma & lancelets) adults have the big 5 chordate synapomorphies. The blood flow resembles craniates, not arthropods which are protostomes. They float as larvae and then swim as adults because of the notochord and myomeres.

True

Which Chordata subphylum does the description correlate to:

• adult has big 5 traits

• contains myomeres

• float as embryo and swim as adults

• increased activity and cephalization

• blood flow resembles crainiate, not arthropod (protostome)

Cephalochordata (Amphioxus - Brachiostoma & Lancelets)

Which Chordata phylum does the description correlate to:

• acornworms

• outgroup to Chordata

• key feature is pharyngeal pores

• they burrow into mud and are filter feeders found in intertidal environments

Hemichordata

Which Chordata subphylum does the description correlate to:

• larval version features all of the big 5 synapomorphies; adults do not

• adults are sessile filter feeders that have endostyle and pharyngeal slits (only two features retained)

Urochordata (tunicate)

What are paedomorphic traits? Which clade shows proof of this?

Juvenile traits that stayed into adulthood. Urochordata (tunicates)

What are the 12 Craniata synapomorphies?

1. ______ crest

• Neurogenic ______

• Braincase

• Complex ____ organs

• ______ nerves

• Tripartite ____

• Complex endocrine system

• Muscularized __

• Differentiation & regionalization of gut & _____

• Gills

• Heart

• Hemoglobin

• 
  

• Neural crest

• Neurogenic placodes

• Braincase

• Complex sense organs

• Cranial nerves

• Tripartite brain

• Complex endocrine system

• Muscularized gut

• Differentiation & regionalization of gut & organs

• Gills

• Heart

• Hemoglobin

How does the neural crest form and what does it form into?

Forms from the ectoderm pinching off from neural crest cells separating and migrating. These cells form many different things ranging from parts of teeth, scales, motor neurons, sensory cells, pigment cells, and gill arch skeleton, etc.)

What are the neurogenic placodes?

A placode is a thickening in the ectoderm layer that turns into separate layers and migrates inward. They are found in the head and they form sensory receptors such as the lateral line, and cranial nerves.

What group is the most basal of the living Craniates, and is a sister group to the rest of the Craniates?

Myxiniformes (Hagfish)

Are sensory tentacles a synapomorphy or autapomorphy of Myxiniformes (Hagfish)?

Autapomorphy

These characteristics are apart of which Craniate clade?

• numerous skin glands that produce lots of slime (apomorphy)

• sensory tentacle (synapomorphy)

• keratinized teeth

• scavengers

• have all 12 craniate characteristics which distinguish them from tunicates & cephalochordates (amphioxus lancelets)

• basal craniates that lack jaws, paired appendages, bone, and vertebrae

Myxiniformes (Hagfish)

These characteristics are apart of which Craniate clade?

• sister group and basal group to all other vertebrates; basal because they have notochords as adults, lack bone & paired appendages, and have rudimentary neural arches.

• some live in sea; breed in rivers (anadromous)

• Ammocoetes are the larvae

• poisonous adults that release venom (parasites)

Petromyzontiformes (Lampreys)

True or false: the three Vertebrae synapomorphies are

• vertebrae

• 2 semicircular ducts

• radial fin muscles

True

Are the characteristics of having no mouth and a rasping oral disc a synapomorphy or autapomorphy of Lampreys?

Autapomorphies

These characteristics are apart of which Craniate clade?

• had large head shields and plates along the trunk

• first group where we see cellular bone (cells in matrix), presence of them unites them to the Gnathostomes

• extinct

Osteostraci

Are the characteristics of heterocercal tail and cellular bone (cells in matrix) a synapomorphy or autapomorphy of Osteostraci?

Synapomorphy

These characteristics are apart of which Craniate clade? Contains 5 synapomorphies.

• jaws (allow for increase size & activity)

• paired nostrils

• 5 gill slits

• jointed gill arches (visceral arches)

• 3 semicircular ducts that help with balance & locomotion

• (also have cellular bone which unites them with Osteostraci)

Gnathostomata

Waht clade did jaws originate from and how did they evolve?

Gnathostomata; they evolved from an anterior gill arch that lay close to the mouth opening.

• 1st arch: mandibular arch made of cartilage or endochondral bone

• 2nd arch: hyoid arch that helps support upper and lower jaws.

• 3rd - 7th arches: gill arches, pouches, and slits

These characteristics are apart of which Craniate clade?

• active predators

• optic pedicel (small cartilaginous prop that supports back of the eye - shared with chondrocytes)

• cartilaginous skeleton

• jaws

• heterocercal tail

• contain extinct, fish-like organisms called Placodermi

Placoderms

These characteristics are apart of which Craniate clade?

• clade contains sharks, skates, rays, and chimaeras

• prefix means cartilage

• have unique placoid scales (acellular bony base)

• fin rays of cartilage (syn)

• vertebral centra (syn)

• sub-terminal mouth (syn)

• teeth in palatoquadrate & mandibular cartilage in their jaw

Chondrichthyes

These characteristics are apart of which Craniate clade?

• well ossified skeletons

• lungs/swim bladder (syn)

• fin rays (= lepidotrichia) (syn)

• includes things like reptiles and mammals in addition to typical fish

• contains 2 subclades - Actinopterygii and Sarcopterygii

Osteichthyes

These characteristics are apart of which Craniate clade?

• basal members include sturgeon, gar, bowfin, teleosts fishes & bichirs

• synapomorphy of ganoid scales (covered by 3 layers of a hard enamel like substance)

• most fish in a more derived group Teleostei with cycloid and ctenoid scales that reduce drag of water

• key innovation is pharyngeal jaws (2nd set of jaws for Teleost)

Actinopterygii

These characteristics are apart of which Craniate clade?

• only extant lobe-finned fish (coelacanth)

• name comes from the presence of muscular fins/limbs

• called living fossils

• commonly known as lobe finned fishes that have a humerus, femur, and cosmoid scales

• basal to special sub group Rhipidistia

Sarcopterygii (Coelacanth)

These characteristics are apart of which Craniate clade?

• lungfish (dipnoi) & tetrapods

• labyrinthodont teeth (enamel folds forward) (syn)

• name means paraphyletic

• dipnoi (lungfish) autapomorphies - breath air w/ gills or lungs, muscularized limbs & walking gait

Rhipidistia

These characteristics are apart of which Craniate clade?

• represent transition to terrestrial lifestyle in chordates

• represents amphibians, reptiles and mammals

• 4 limbs with digits (syn)

• presence of zygapophyses - interlaced bones on the vertebrae (syn)

• sacral vertebrae that transfer weight to pelvic girdle and legs (syn)

• lack skull - pectoral girdle connection (syn)

• earliest known organism: Ichthyostega & Acanthostega (lived at water/land interface and made short ventures onto land, had many digits, lateral line, & lungs and internal nares (choana))

• Temnospondyls showed transition to modern (living) amphibians, had unique columella & tympanum

Tetrapoda

Which living fish looks like the extinct Ichthyostega and Acanthostega and had choana and leg like fins?

Tiktaalik

These characteristics are apart of which Craniate clade? These are some autapomorphies.

• reduced digit number to 5 or fewer

• bimodal life history (larvae)

• short ribs

• incomplete ossification of carpal and tarsal bones

• amphibian papilla (inner ear)

• 
  

Amphibia/Lissamphibia

These characteristics are apart of which Craniate clade?

• reptiles and mammals

• development of amniotic egg

• evolutionary significance for amniotic egg allowed for major radiation of animals, and no larval stage (can invade land & carry its own water and energy).

• amniotic egg contains 4 membranes

• - yolk sac (nutrition)

• - amnion (fluid-bath protection)

• - allantois (collects waste)

• - chorion (allows gas exchange)

• dry, heavily keratinized skin

Amniota

These characteristics are apart of which Craniate clade?

• have scales or feathers

• 2 clades (Testudines & Diapsida)

• Testudines are anapsids that have no temporal fenestrae, beak or teeth, and have fused elements (turtles)

• Diapsida are lizards, snakes, gators & birds, have two temporal fenestrae (holes of temporal region of skull)

Sauropsida (Reptilia)

These characteristics are apart of which Craniate clade?

• Malleus, incus, and stapes

• cochlea, dentary/squamosal jaw joint, hair, and mammary glands

• 3 major clades

• - Monotremata (platypus & echidnas) have 1 opening for fecal & urogenital products, only mammals to lay eggs.

• - Metatheria (marsupials - kangaroos, possums, etc.) have placenta but unique developmental pattern, embryo in pouch

• - Eutheria (placental mammals - humans, dogs, etc.) have long embryonic & fetal development, unique placenta with O2 and nutrient exchange

Mammalia