Final Flashcards
What is Homology?
A hypothesis where relationships between physical form comes from a common origin
What are criteria we might use to hypothesize homology between organisms?
Position (similar muscles in similar places)
Development (limb buds look similar across organisms and diversify into things such as fins and legs later on)
What is Meckel-Serres Law of Development?
Scala naturae; through development, every organism passes through the adult form of the lower organism (ontogeny recapitulates phylogeny)
What is Karl Ernst von Baer’s Law of Development?
General characters of a large group appear earlier in embryo than specialized characters; so instead of passing through the forms of “lower” forms, it separates
What is Darwin’s laws of development?
Embryology is evidence of descent; shared traits due to common ancestry
What are the 6 steps to “build an animal?”
- Cleavage
- Blastula formation
- Gastrulation
- Neurulation
- Somitogenesis
- AP Patterning (Conferring Identity)
Explain what happens during Cleavage
- Cleavage is the first step of development -> getting to more than one cell.
- A zygote is a single diploid cell
Explain the two types of cleavage
Holoblastic: Total cleavage where cell division happens across the entire zygote (lampreys, mammals, amphibians)
Meroblastic: Partial cleavage where the embryo forms on top of undivided yolk (birds, reptiles, hagfish)
Describe what happens during the second step, the formation of a Blastula
Axes and cell fates are determined.
- Zygotic transcription begins
- Breaking up of the radial symmetry occurs via cortical rotation from sperm, thus establishing an ORGANIZER!
Explain what an “organizer” is during the blastula formation; NOT gastrulation yet
The organizer is different for different organisms, but the gray crescent is important for determining dorsal vs ventral sides
Describe what happens during Gastrulation (step 3)
The separation of outside versus inside occurs
- Germ layers are created (the 3 layers), and the archenteron (“old gut”) folds in due to the blastopore inducing the cavity
- The organizer is what emits signals for gastrulation! Has different names for different organisms (The Shield for fish, hensen’s node for birds, the node for mice)
Explain what happens during step 4, Neurulation
Getting the neural ectoderm inside (we need our neural tube and brain inside)
During Neurulation, the Neural Crest comes into play. Explain some of the important points on the Neural Crest
- Neural Crest cells migrate down channels: They follow the semaforin attractant molecule
- Neural Crest cells differentiate and form gill arches, cartilage, pigment, sensory neurons, smooth muscle, and adrenal cells
- Placodes & Lateral Lines
What are placodes?
Thickenings of the ectoderm for sensory
What are lateral lines?
- Occur in all anamniote vertebrate clades (Lamprey, sharks, fish)
- Neuromast network
- It is a placode that migrates along the entire body; neural crest might be signaling for the lateral line movement (not proven yet)
Explain what happens during Somitogenesis, the 5th step
The mesoderm is patterned (muscles)
- Body segmentation, with differentiation happening and then somitogenesis moving anterior to posterior
- There is a somitogenesis clock (self-regulating)
Explain what happens during AP Patterning (step 6)
Hox genes are highly conserved and give each segment identity (determines placement of axial structures and limbs)
- Basically confers anterior and posterior identity to the somites we just formed
Explain the Phylotypic Stage
Early on in development, embryos are robust and incredibly variable.
Later on in embryo development, they are constrained to certain forms (chickens need to look like chickens etc.), but highly variable/specialized
But, somewhere in between these two stages, you need a set of basic genes (like hox genes being highly conserved) -> conserved gene expression
Explain how the somitogenesis clock builds diversity
Fate switching (slower in short bodies, faster in snakes)
What is systematics?
The scientific study of the kinds and diversity of organisms and all relationships among them = Diversity AND organization of diversity! It is predictable and retrievable
Explain nested versus exclusive hierarchies (regarding trees)
Exclusive: Linear progression with each rank being its own thing (like military ranks -> a Seargent is not also a private, corporal, etc anything lower)
Nested: Sounds like the name, more specialized groups are contained in larger wider groups
What is catastrophism?
Everything created is how it is; there is NO descendant species (they are all fixed)
Homology vs Analogy
Homology: Common ancestry
Analogy: Same function, convergence
What is cladistics?
Technique for characterizing a hierarchy of groups
What are the three “axioms” of cladistics?
Synapomorphy: Shared features with a hierarchical pattern
Parsimony: Hierarchical pattern expressed economically in branching diagrams (fewest changes across a tree)
Phylogenetic Systematics: Nodes symbolize shared homologies
What is a phylogeny?
Evolutionary relationships among a set of taxa
What’s apomorphy vs plesiomorphy? And what about synapo & symplesio morphies?
Apomorphy: deriver character
Plesiomorphy: Primitive character
Synapomorphy: shared derived character (homology)
Symplesiomorphy: shared primitive character (cannot define groups)
What does homoplasy look like on a tree?
Where a character appears on tree multiple times (usually referred to like convergent evolution)
What germ layer is the excretory system from?
Mesoderm
What does the excretory system do?
Regulates composition of interstitial fluid bathing cells
Cells produce waste (like nitrogen) & excretion removes this metabolic waste
Why is it called urinogenital system?
Because reproductive system usually connected with developing excretory ducts
Briefly outline Kidney development
- Kidneys develop from NEPHRIC RIDGES (or mesomeres) that are between the lateral plate (big smooth muscle ventral) and somites (patterned muscle segments on dorsal side)
- The nephric ridge is segmented into nephrotomes (they each have nephrons and renal tubule)
Explain a cross-section of an organism’s kidney region
Moving outwards from the Neural Tube (ectoderm derived), we have a dorsal aorta directly below. Connecting the aorta is a small tube that goes to the coelom, a mesoderm-derived pouch. Where the tube and mesoderm connect is the cup where the Glomerulus is. On top of the mesoderm coelom thing is the Archinephric duct, which is separated from the Neural tube by somites.
What direction do kidneys develop?
Segmentally, front to back! PRONEPHROS -> MESONEPHROS -> METANEPHROS
Explain the layout of a renal tubule
Proximal end: the renal capsule (cup-shape) which envelopes capillary group known as the glomerulus (enters = afferent anteriole, exits = efferent anteriole)
Renal Corpuscle is connected to the rest of the tubule (proximal, intermediate, and distal tubules)
Explain how fluid is filtered from the glomerulus to the renal capsule
Hydrostatic pressure; the afferent arteriole is larger than the efferent arteriole. This is INDISCRIMINATE filtration, so you get both waste and things you want to keep (such as water) coming through
So, with fluid passing from glomerulus to renal capsule, we are also having things we want to keep pass through as well. How does reabsorption to get these things back happen?
Reabsorption occurs further down in the renal tubule with interactions between tubule and capillaries.
Explain the differences in how reabsorption works between Chondrichthyans/diapsids, Fish/Lissamphibia, and mammals
Chondrichthyans: Efferent arteriole from the glomerulus comes down and has capillary bed with supply from it and the “renal portal vein” which then all go back to the posterior cardinal vein
Fishes: The renal portal vein is the only supply to the capillary bed around the tubule. the glomerulus efferent renal arteriole goes back to the caudal vena cava (same as posterior cardinal vein p much)
Mammals: NO renal portal system. Only the efferent renal arteriole from the glomerulus is used, but it establishes a loop and creates a COUNTER-CURRENT! (efficient scrubbing)
Explain renal tubule evolution
Branchiosoma: the tubules open into coelom recess (external glomeruli), cilia move the waste into archinephric duct
Elasmobranchs (sharks): renal capsule connects to coelom but its a narrow funnel with cilia between the coelom and the renal capsule, so still cilia action, but better
Go over the evolution of kidney development, from the hypothetical to metanephros
Hypothetical Ancestor: Holonephros, a full set of functional segmented tubules which drain into the archinephric duct. (most similar to hagfish/caecilians)
Head Kidney: All vertebrates start with anterior renal tubes and then the archinephric duct grows to cloaca, which forms a head kidney. HOWEVER, this head kidney is only functional in cyclostomes and lissamphibians to this day (non-functional in sharks and amniotes). The head kidney + rest of the segmented nephrons posterior are the PRONEPHROS (fully functional and segmented vs Holonephros)
Mesonephros: The pronephros regresses as the ducts develop and form more tubules further towards the tail. The tubules with common origin unite into a COLLECTING DUCT. The mesonephros is functional in all vertebrate embryos and larvae. This is also when the anterior part of the opisthonephros is co-opted for sperm ducts.
Metanephros: Amniote mesonephros is transitional, so later on in development the uretic bud at the caudal end grows and forms tubules and the ureter (homologous to posterior opisthonephros). Separates from the archinephros! Ureter -> bladder
Explain iso, hypo, and hyperosmolar organisms and the flow of water + ions
Isosmolal: Salt concentration is the same inside as outside (hagfish)
Hyposmolal: Blood is less salty than ocean water, so ions are always flowing in and water out, so need to drink more!
Hyperosmolal: Sharks; blood is more salty than ocean, so water inflows
TELEOSTS in FRESH WATER: Water constantly entering, need to piss
TELEOSTS in SALT WATER: Water leaving body, NEED TO DRINK! Excretes salt out through gills
Steno- vs Euryhaline
Stenohaline: narrow tolerance of salinity (freshwater fish have leaky gills allowing for ion exchange, no need to drink water due to it flowing in)
Euryhaline: broad tolerance of salinity (regulate levels of urea in blood)
What are the two generalized systems of respiration?
Tidal flow and unidirectional flow
What are lungs derived from?
Endoderm
Explain the oxygen cascade
It is the diffusion of O2 across a partial pressure gradient (the PO2 is lowest in the mitochondria, slowly higher up to lungs, but still way lower than the air, allowing for efficient O2 uptake)
Compare concurrent with countercurrent flow
Concurrent: the flows are the same directions, with one tube being deoxygenated, the other oxygenated, so towards the ends of their lengths they are both about the same amount (50%)
Countercurrent: Oxygenated tube flows one direction while the deoxygenated tube flows the opposite direction. This allows for each tube to range from 0 - 100% at each end! Near total exchange
What method of flow via gills allows for countercurrent exchange? (Tidal or unidirectional)
Unidirectional! Can optimize the pO2 differential, as the water through gills flows only one direction = counter current can be created
Hemi vs Holobranch
Hemi: gill lamellae on one side
Holo: Gill lamellae on both sides
Why gain lungs?
More available oxygen! Air has wayyy more oxygen than water
Our lungs are tidal flow - how is this style of inefficient gas exchange combatted?
There is so much oxygen in the air that we can handle stale air
Negative vs Positive pressure ventilation via lungs
Negative: Air sucked in (such as expansion via intercostals and contraction of diaphragm) -> mammals, lizards
Positive: Breath is pushed into the lungs (such as decrease in buccal volume) -> gulping and swallowing air (frogs).
How do mammals respirate while running?
Locomoter posture changes allow running and breathing
Explain the types of flow in avian respiration briefly
Cross-current exchange in lungs
Unidirectional flow in air sacs
Walk through the steps of avian respiration
- First breath, air enters the first air sac
- Breathes out, air moves from first air sac across lungs (cross-current exchange region)
- 2nd Inhale, air moves from lungs to next air sac
- 2nd Exhale, air moves from air sac back out
All of this is happening with continuous air, so it isn’t just one piece of air in the lungs and sacs at a time!
Outline the parts of parabronchus units (avian respiration)
Central lumen for air entry, surrounded by a mantle of tissue (capillaries)
Explain cross-current exchange in avian lung
The lumen direction = air flow, whereas the blood flows perpendicular.
Air is repeatedly meeting deoxygenated blood! there is a constant differential of partial pressures. (see diagram on slide 50!)
What type of lung are crocodile lungs?
Negative pressure
Compare and contrast the cardiovascular and lymphatic systems
CV: O2 to cells, waste removal, intercellular signaling
Lymphatic: Plasma filtered & returned to blood, adaptive immune response, Lymphocyte generation & memory storage
Outline the parts of the blood & subsequent functions of blood
Plasma: fluid
RBCs: Containers for hemoglobin
WBCs: Defense mechanism
Platelets: Clotting factors
Functions:
Respiration
Immune response
Nutrition
Excretion
Hormone Transport
etc.
Relaxed vs Taut states of Haemoglobin
Relaxed: High O2 affinity
Taut: Low O2 affinity
Explain layers of Vessels & capillaries vs arteries/veins
Arteries (away) / Veins (towards)
(Outside) Connective tissue -> Smooth Muscle -> Endothelial (inside)
Capillaries:
(outside) Membrane -> Endothelial (inside)
How do our vessels move blood after it has gone to capillaries and is moving slowly with low pressure?
Cross-sectional valves & pumps (remember the reverse valves for giraffe heads)
What are the three parts of a heart?
Atrium (blood enters)
Ventricle (blood pump to aorta)
Pericardium (covering of heart)
Compare circulation of: Amphioxus, Tunicate, Hagfish, Shark/Teleost, and 3 & 4 chambered hearts
Amphioxus: No heart, colorless blood
Tunicate: Heart tidal pump, NO circuit
Hagfish: 5 hearts, tons and tons of blood; Frank-starling reflex allows the different hearts to self-adjust (feedback into pressure)
Shark/Teleost: four parts (sinus venosus, atrium, ventricle, conus arteriosis) & S-shaped
3 chambered: Lizards & lissamphibia; partial separation of flow
4 chambered: mammals, birds, crocs; complete division between ventricles
Whats the Foramen of Panizza?
Opening between vessels that is OPEN when a crocodile is holding its breath (blood bypasses lungs; stabilizes oxygen)
Compare the venous system in embryo vs adult in gnathostomes
EMBRYO
Vitelline -> yolk
Cardinal <- body
Subintestinal -> loop
ADULT
Vitelline -> liver
cardinal -> break into subcardinals
Subintestinal: no longer connect
Fetal vs Adult Mammalian Circulation
Umbilical Vein carries oxygen from the placenta –> liver; 50% of the blood bypasses the liver and goes to the right atrium (foramen ovale between the atria allows flow between the atria)
Adult: double circulation (foramen ovale held closed by pressure, but often fused); the ductus arteriosus is now a ligament
Compare endo with dermal skeleton
Endo: cartilaginous
Dermal: Compact layered bone (includes dentine and enamel); not preformed in cartilage (some exceptions like baby skull)
What parts of a fish skull are endo and dermal skeleton?
neurocranium: endo
Viscerocranium (palatoquadrate, arches, articular): Endo
Dermatocranoim (mandible, palatine etc): Dermal
What germ layers is bone made from?
Mesoderm & Neural Crest (dentine for example)
What are the three components of living bone
- mineralized framework
- fibrous collagen component
- soft tissue
Explain endochondral bone structure (and also explain osteocytes/lacunae formation)
Inner Layer: Cancellous bone (spongy)
Outer Layer: Compact (cortical) bone with nutrient supply; the Canaliculi are tiny canals which are surrounded by osteocytes (which are osteoblasts that completed cell division and are in lacunae)
What are Osteons
Osteons are concentric rings of bone cells and layers of matrix around a nutrient blood vessel in the cortical bone
What is trabecular?
cancellous bone unit + rod and hydroxyapatite
Why do fish have so many ribs?
Ribs form in the myosepta, which act as levers, transferring force (axial bending)
What is sesamoid bone?
inter-membranous bone (knee cap)
Outline bone growth steps
Chondrocytes proliferate & calcify
osteoblasts establish growth center
osteoclasts remodel & trabeculae grow
What are the layers of dermal bone?
(innermost)Lamellar aspidin
Spongy acellular bone
Dentine Tubercles(outermost)
What bones are dermal bone in bony fish?
Scales, skull roof, fin rays
What is dentine?
Tubular mineralized bone (teeth)
Organic and liquid portions higher than enamel
odontoblasts deposit!
odontoclasts RESORB!
What is enamel?
Hard, mineralized, prismatic bone
Mostly inorganic
Ameloblasts deposit! Cross-ply enamel
Comes from ECTODERM!
Compare scales and teeth
They are separated; similar, but teeth develop differently and are ordered
What is cartilage?
Avascular supporting tissue
Chondrocytes deposit
Comes from mesoderm and neural crest
No remodel, No repair
What is collagen and what are the 2 types?
Proteins with structure (connective tissues)
Type 1: Teeth, bone, scar tissue, blood vessels
Type 2: Hyaline cartilage (joint surfaces)
What are the three types of cartilage?
Hyaline: Articular surfaces (type 2)
Fibro: Pubic symphysis (type 1 typically)
Elastic: Flexible (ear, epiglottis)
How do sharks live so long if cartilage doesn’t repair?
Calcified cartilage (areolar, in rings along spine)
Tesserae
What are tesserae?
Calcified cartilage plates around cartilage skeleton (GEL SANDWICH)
Outline the parts of a neuron
Cell body (the circle part), dendrites (receptive part), Axon w/ sheath (conducting), and terminal arborization (transmissive)
What are the gaps between the glial schwann cells that form the myelin sheath?
Nodes of ranvier
What is special about lamprey axon?
No myelin sheath; they have larger axon for increasing speed
What is the C-start response?
giant axon from hindbrain to tail; think of fish response forming a c-shape with body
What are the three parts of the brain
Prosencephalon (forebrain) -> this is the combo of the telencephalon and diencephalon
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
Of the tripartite brain, what is the important parts of each of the 3 regions?
Hindbrain: Medulla oblongata, Cerebellum (note in lampreys no real differentiation)
Midbrain: Tegmentum, Optic Lobes
Forebrain:
- Diencephalon: hypothalamus, epithalamus
- Telencephalon: Cerebrum
What part of the brain is enlarged with electric fish?
Cerebellum
What does medulla oblongata do?
Reflex centers for respiration, heartbeat, intestinal motility
What does the cerebellum do?
Input from sensory systems; coordinates muscle activity
What does the tegmentum do?
Floor of midbrain and similar function to medulla oblongata; locomotor movements
What is the caudal portion of the forebrain divided into (and what are their positions?
Epithalamus: dorsal
Thalamus: Lateral
Hypothalamus: Ventral
What does epithalamus do?
Parietal-pineal complex (circadian rhythm)
What does the thalamus do?
Relay sensory info to the telencephalon (rostral part of forebrain)
What does the hypothalamus do?
Visceral integration; temperature, water, appetite, metabolism, etc
What is the telencephalon?
Rostral part of forebrain (cerebral and olfactory)
What are pallium and subpallium?
Both are gray matter of the cerebrum (part of the telencephalon)
General layout of cranial nerves
Hindbrain:
- Vagus (sensory motor)
- Glossopharyngeal (sensory motor)
- Auditory (sensory)
- Facial (sensory motor)
- Abducens (motor)
- Trigeminal (Sensory motor)
Midbrain:
- Trochlear (motor)
- Oculomotor (motor)
Forebrain:
- Optic (sensory)
- Olfactory (sensory)
Inner ear structure in hagfish vs lamprey vs gnathostomes
Hagfish: 1 duct
Lamprey: 2 ducts
Gnathostomes: 3 ducts
Describe the general parts of inner ear structures
- Semicircular ducts filled with endolymph, with ampullae at the ends of each duct
- Cristae are then in each ampulla
- maculae are larger patches, which are overlain by statoconia or otoliths
briefly outline hearing specialists vs vocal taxa
Hearing is linked to acoustic communication; vocal organisms have specialized hearing systems, and species that listen but don’t make sound are also a thing.
Quiet water: high sensitivity
Noisy water: low sensitivity
Explain the cochlea
In mammals, an extension of tube outside the cochlear (outside is perilymph, inside is endolymph). Sound waves travel down and across the cochlear
Macula Neglecta, what is it and who has it?
Elasmobranchs listen through their heads; the macula neglecta is a connection between canals that allows for semi directional low frequency sound detection
How is the lateral line and hearing similar?
- Both receive signals with hair cells (stimulated by liquids move across their surface)
- Develop from adjacent placodes
Gross anatomy of eyeball
Fibrous tunic (outer layer)
Vascular Tunic (middle nutritive layer)
Retina (inner layer with photoreceptor)
What are the parts of the fibrous tunic in the eye?
Sclera: opaque white portion, which can contain sclerotic bones
Cornea: avascular transparent layer at front of eye
What are the parts of the vascular tunic in the eye?
Choroid: lines posterior and nourishes retina
Iris: pupil and aperture
Ciliary body: anchors lens
Rods vs Cones
Rods: rhodopsin and absorb light
Cones: iodopsins and spectral absorption
briefly outline how different organisms focus theyre eyes (the two methods)
1: Moving lens closer or further from retina
- Lampreys (lens back), Sharks (protractor lentis), Actinopts (retractor lentis)
- Distorting lens shape (focal length), but keeping distance fixed
- Amniotes
