Anatomy Exam 1 (From Study Guide)

not fully filled in yet***

phylogeny

the relationship between all the organisms on Earth that have descended from a common ancestor, whether they are extinct or extant

cladogram

a __branching__ diagram showing the cladistic relationship between a number of species.

synapomorphy

shared derived feature

plesiomorphy

shared primitive feature

monophyletic group

sometimes called a clade, includes an ancestral taxon and all of its descendant

paraphyletic group

a group of animals which contains a common ancestor and some, but not all, of the descendants

parsimony

tells us to choose the simplest scientific explanation that fits the evidence. In terms of tree-building, that means that, all other things being equal, the best hypothesis is the one that requires the fewest evolutionary changes.

gastration

an important phase of embryonic development in which the embryo changes from a single-cell layer to an embryo comprised of multiple germ layers. Some fundamental similarities among all chordates are found during this process, at the of which chordate traits are apparent.

visceral

structures associated with the gut (and urogenital tract)

somatic

structures associated with the body wall (includes somite derived structures, but basically everything not gut-related)

coelom

space within the body cavity.

serosa

outer epithelial layer that secretes lubricating fluid into the cavity

sclerotome

formed from the somites (paraxial mesoderm)

forms …

myotome

formed from the intermediate mesoderm

forms muscle

dermatome

formed from the lateral mesoderm

forms the dermis

transverse septum

separates the peritoneal cavity from the pericardial cavity

ventral root

emerge within each segment and contain motor fibers that send signals to muscle

dorsal root

emerge between each pair of segments and contain some motor fibers, but also sensory fibers that transfer signals from peripheral structures to the spinal cord

paedomorphosis

an alternative process to metamorphosis in which adults retain larval traits at the adult stage

direct development/acceleration

when organisms hatch as mini adults

somatopleure

outer body wall

splanchnopleure

gut wall

mesentery

suspend the gut tube in the body

placode

thickening of ectoderm over regions of brain

neurogenic

nerves grow from placodes to reach brain

branchiomere

gill segments

head segments 2-8 in the brain

pharyngeal slit

Gill pouches invaginate at membrane between each pair of branchiomeres to produce these

splanchnocranium

Each gill bar includes 2 large elements on either side of midline joint (dorsal = epibranchial, ventral = ceratobranchial). These elements are derived from neural crest and contribute to the skull as this

neurocranium

sclerotome-derived part of skull ventral to brain.

deuterostome

Any of a major group of animals defined by its embryonic development, in which the first opening in the embryo becomes the anus

protostome

Any of a major group of animals defined by its embryonic development, in which the first opening in the embryo becomes the mouth

heterochrony

a change in developmental timing

organogenesis

the process of formation of organs from three germ layers.

analogous structure

are features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature (compare to homologous structures) and which evolved in response to a similar environmental challenge.

homologous structure

are similar physical features in organisms that share a common ancestor, but the features serve completely different functions

placoderms

The first vertebrate jaws evolved from the ___________________, cranial skeletal elements that develop entirely from neural crest.

homologous

The forelimb of a squirrel is ___________________ to the wing of a bat.

analogous

The wing of a bat is ___________________ to the wing of a butterfly.

buccal

In fishes, there is a single _____________________ cavity surrounding all of the internal organs except the heart; in amniotes, this cavity is further divided to separate the lungs from the other organs.

E, C, B, A, D

List the following items in order of their embryonic anatomical position from dorsal to ventral by writing the letters assigned to the items in the correct sequence.

a.     Pharynx

b.     Notochord

c.     Brain                                             _______________________

d.     Ventral aorta

e.     Dermatocranium

D, B, A, C, E

For the following group of terms, list the items in the order that they first appeared in the geologic record, from earliest to latest, by writing the letters assigned to the items in the correct sequence. 

 

a.     jaws

b.     brain

c.     bone                                              _____________________

d.     lungs

e.     limbs

paraphyletic group

Draw a cladogram that contains a jellyfish, turtle, bat, bird, and crocodile.

Bat is a ____________ to the clade containing crocs and birds.

How is the primitive streak formed?

when the epiblast cells migrate to the center of the embryo

How are each of the germ layers formed?

begins with one thick layer of cells which then deliminates to form two layers, the epiblast and hypoblast. then when the epiblast cells create the primitive streak and move ventrally in between the two layers the mesoderm forms. the epiblast is then relabeled as the ectoderm, and the hypoblast as the endoderm.

Where is the notochord in relation to the primitive streak?

the notochord is located ventrally to the primitive streak.

How do the ventral and dorsal mesenteries form? What do they enclose?

the ventral and dorsal mesenteries are formed by the mesoderms folding down to connect to one another ventrally. The spaces between the two lateral mesoderms then become the dorsal and ventral mesoderm. They enclose the gut tube.

How does the dorsal pancreas form? Does is form into the dorsal or ventral mesentery?

Ventral (caudal) and dorsal (cranial) outpouchings develop at the junction of the foregut and midgut during the fourth week of gestation. The dorsal diverticulum forms this. This then forms into the dorsal mesentery.

What are two ways of determining if a trait is homologous?

1. Context: the content surrounding the feature being examined.
2. Development: looking at the embryo and beginning development of an organism and the feature being examined.

How does the liver form? Does is form into the dorsal or ventral mesentery?

In chordates with lungs, these develop as ventral outpockets of the gut, dorsal to the heart. In reptiles (including birds) and mammals (including humans), extra folds of serosa separate the lungs from portion of coelom enclosing liver, providing distinct pleural and peritoneal cavities. The liver develops within the ventral mesentery.

The transverse septum divides the coelom into what cavities?

the peritoneal cavity from the pericardial cavity

How to sense organs develop?

they develop in association with thickening of ectoderm over regions of brain

Where does the nasal placode develop from?

lies over the telencephalon

Where does the otic placode develop from?

lies over the myelencephalon

Where does the lens placode develop from?

lying over the diencephalon

How are gill slits produced?

Gill pouches invaginate at membrane between each pair of branchiomeres to produce this

What synapomorphies distinguishes deuterostomes and protostomes?

deuterostomes form the anus of the organism first while protostomes form the mouth of the organism first

What synapomorphies unites the Cephalochordates, Urochordates, and Vertebrates?

1. DHNC
2. notochord
3. post anal tail
4. pharyngeal slits

In what cavity is the heart formed?

pericardial cavity

What structure joins the liver to the transverse septum?

diaphragm

How do the lungs develop? Where are they in relation to the heart?

In chordates with lungs, these develop as ventral outpockets of the gut, dorsal to the heart. In reptiles (including birds) and mammals (including humans), extra folds of serosa separate the lungs from portion of coelom enclosing liver, providing distinct pleural and peritoneal cavities. The lungs are located dorsal to the heart.

What is the function of the serosa?

it secretes lubricating fluid into the cavity

Are birds tetrapods, quadrupeds, or both? Explain.

birds are theropods this is because of some of their bones, feathers, furcula, tail, and hallux

How are the pleural and peritoneal cavities formed?

extra folds of serosa separate the lungs from portion of coelom enclosing liver, providing these cavities

List two ways that protostomes and deuterostomes differ in development. Be clear in saying which groups show what patterns.

List two ways that protostomes and deuterostomes differ in development.

Describe the segmental organization of the head. What structures are present in each branchiomere?

There are 8 segments in the head. Each containing a branchiomere. The branchimere contains 4 structures itself, the Cranial Nerve, Aortic Arch, Branchiomeric Muscles, and Skeletal (Gill) Arch.

Explain the evolutionary changes in the number of digits present on early versus later tetrapods. What likely led to this difference?

Early tetrapods had around 8 digits. Today, most have 5 or less digits. The 5 digits on the hand and foot that are so common wasn’t ancestral → instead, it might have evolved through a developmental truncation, where the arch of development that produces digits just stopped early.

How is it that someone who is “paralyzed from the neck down” is still able to breathe? (Hint: think about nerve connections to the mammalian diaphragm).

A mechanical respirator, a clear box filled with pumps and tubes, connects to his throat and breathes for hi

What are the three types of mesoderm and what does each form?

paraxial, intermediate, and lateral plate. paraxial becomes the sclerotome, myotome, and dermatome. intermediate becomes the kidney and gonads, and the lateral plate becomes the splanchnic somatic and extra embryonic.

What are the three types of paraxial mesoderm and what does each form?

Paraxial becomes the sclerotome which becomes the skeleton. the myotome which becomes muscle. and the dermatome which becomes the dermis.

What are the four synapomorphies of Chordates?

1. DHNC
2. notochord
3. post anal tail
4. pharyngeal slit

What are the three sections of the brain? What does each differentiate to become?

forebrain/prosencephalon, midbrain/mesencephalon, and hindbrain/rhombencephalon. The prosencephalon becomes the telencephalon and the diencephalon. The mesencephalon stays the same. And the rhombencephalon becomes the mesencephalon and myelencephaon.

List the three groups (subphyla) that make up the Chordata. Which two are most closely related?

Urochordata, cephalochordate, and vertebrata. Urochordata and vertebrate are the closest related.

In what taxonomic group do we first find bone?

Ostracoderms (Jawless vertebrates)

What are the two major features that characterize gnathostomes?

1. Second pair of paired fins
2. Horizontal semicircular duct in ea

mesoderm

germ layer notochord

ectoderm

germ layer epidermis

mesoderm

germ layer heart

mesoderm

germ layer lungs

ectoderm

germ layer neurocranium

mesoderm

germ layer dermis

mesoderm

germ layer vertebral column

mesoderm

germ layer blood vessels

endoderm

germ layer connective tissue of gut

endoderm

germ layer anal canal

endoderm

germ layer lining of digestive tract

mesoderm

germ layer mesentries

ectoderm

germ layer brain

endoderm

germ layer gonads

ectoderm

germ layer spinal chord

mesoderm

germ layer reproductive ducts

ectoderm

germ layer dermatocranium

mesoderm

germ layer skeletal muscles

endoderm

germ layer lining of urinary bladder

ectoderm

germ layer cranial nerves

mesoderm

germ layer coelom

endoderm

germ layer kidney

ectoderm

germ layer spinal nerves

mesoderm

germ layer liver

ectoderm

germ layer optic nerves

endoderm

germ layer pancreas