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G12  (last:01-18-2009)
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Evolution Notes 3      posted 01-18-2009
Phylogeny and Cladistics: (Read 13.4)

Traditional Classification: (Taxonomy)

->Linnean Taxonomy -> Organisms were classified according to morphological (structural).
This system was started by Carolus Linneaus long before the sciences of paleontology, genetics, comparative embryology and evolutionary biology were available.
***see 1 a),p606***

Problem:
Groups that share many similar features are often not closely related.
Ex. Turtles share many features with crocodiles, but are distantly related.
Groups that ARE closely related sometimes are very different in their anatomy.
Ex. The closest living relatives of manatees are hippopotamuses.

Modern Classification (Phylogeny):

•Similar to traditional Taxonomy, but improves upon it.
-> Based upon each species EVOLUTIONARY HISTORY.
-> closely-related organisms are classed within "groups" that share a COMMON ANCESTOR ---> This group is called a CLADE.

CLADES (groupings) are based upon:

•Fossil record (shows development of species -> is always improving)
•comparative anatomy (internal and external)
•developmental morphology (comparative embryology)
•comparative genetics (as genomes of more species are sequenced, this becomes increasingly better).

CLADEOGRAM:
• Is a phylogenetic "Family Tree"
->it shows the evolutionary relatedness of a group of organisms.

SYNAPOMORPHIES:
-> Anatomical (or genetic) features shared by a group of species.
-> these are inherited from a common ancestor (in which the feature first evolved)
-> Synapomorphies determine the branching points (nodes) in constructing a family tree of related species.

Note: Shared features (alone) does NOT mean shared ancestry!



Evolution Notes 2      posted 01-18-2009
DIVERGENT/CONVERGENT EVOLUTION: Read 13.3

Divergent Evolution:
• after speciation, differential selection pressures (disruptive selection) cause two species to continue to specialize along different pathways. (evolution is a branching "tree" of life!)

Ex. Ancestral "cat" into: lion, tiger, jaguar, mountain lion, etc.
(over 60 "cat" species worldwide)

Adaptive Radiation: When one ancestral species evolves into three or more species.
• happens when many new habitats become available.
Ex. Darwin's finches.

Convergent Evolution:
• two (or more)species that are NOT closely related become increasingly similar in appearance in response to similar selective pressures.
Ex. Shark/dolphin, bat/bird, etc.
***see Fig. 2, p603***
->result in HOMEOPLASIES (analogous features).
-> features that serve similar function, but have very different evolutionary origins.
Ex. Wing of: bat/bird Flipper of: whale/shark(fin)
Penguin's wing/seal's flipper

Ex. Mammals and birds: both are homeotherms (warm-blooded).
Common Ancestor??? Existed LONG AGO (~230MYA) -> ancestor probably NOT warm blooded - both groups developed this feature independently!
Proof: Many descendant lines (snakes/lizards/crocodiles) are NOT warm-blooded.
***see Fig.2,p607***
What does fossil and genetic evidence show?
->homeothermy evolved separately in birds and mammals after they split off from a common ancestor.

***Read last paragraph, p613***
SINES (Short Interspersed nucleic elements)and LINES (Long interspersed nucleic elements)are ideal phylogenetic tools.
•they are inheritable (when a retrovirus infects the germ cells)
•they are large sequences -> easy to identify
•they are relatively rare
•most retroviruses are very host-specific

Result?
Chances of two different species having the same SINE or LINE by coincidence is EXTREMELY REMOTE!!
-> we can assume both species inherited the SINE or LINE from a common ancestor.

Mitochondrial DNA (mtDNA):
Mitochondria:
•reproduce by binary fission (like bacteria).
•have their own DNA
•can only be passed in the egg (no cytoplasm in the sperm).
->can determine maternal lineage.
->can NOT determine paternal lineage (analysis of Y chromosome can do this though).

Evolution Notes 1      posted 01-18-2009
NOTE: These are only outline notes that cover the important concepts. To properly understand this section, you MUST do the assigned reading!

SPECIATION: Read 12.6 in text.

Species: Is a real (or potential) population capable of interbreeding and producing fertile offspring.

• speciation occurs when two populations become reproductively isolated.

Isolating Mechanisms:

1. Prezygotic (prevent mating from occurring)
Ecological Isolation - populations live in different habitats.
Temporal Isolation - populations are reproductively active at different times.
Behavioral Isolation - populations develop different mating rituals.

(prevent fertilization from occurring)
Mechanical Isolation - anatomical barriers to successful fertilization.
Gametic Isolation - incompatible molecular markers develop on gamete cell membranes.

2. Postzygotic (prevent offspring from transmitting their genes)
Zygotic Mortality - Zygote fails to develop (genetic incompatibility).
Hybrid Inviability -poor health-> fail to survive to reproductive age.
Hybrid Infertility -offspring healthy, but infertile.

***see Table 1 & 2 pg572-573***

Parent Population
(isolation)

Population A Population B
l l
l l (genetic drift)
l l
V V
Species A Species B

SPECIATION: When individuals from separate populations are brought together -> if reproduction fails to occur, speciation has happened.

Note: Since evolution is ongoing, there are many populations that are in that "gray area" of partial success (protospeciation).





Attendance and Due Dates      posted 02-13-2008
In a University preparation subject such as this, attendance is critical to success. If you are absent for a legitimate reason (school event, illness or family emergency), you are expected to write missed tests IMMEDIATELY upon your return. It is the student's responsibility to make arrangements for missed tests. Students that are not legitimately absent will be given a mark of zero on missed tests.
Late assignments will be deducted result in mark deductions (see latest school late policy). Make sure you hand in assignments on time! Once an assignment has been marked and returned to the class (usually 3 to 5 school days after the due date)any assignments not handed in will be worth zero. Remember - you have an entire week after being given an assignment to hand it in before the due date. The due date is the LAST day to hand it in without deductions.
If you know you will be absent on the due date of an assignment, it is your responsibility to hand it in early or make arrangements with your instructor BEFORE it is due.






Kidneys 4      posted 10-31-2007
KIDNEY DISEASES;

Kidney Stones:

Cause -> Minerals precipitate out of blood (calcium oxalate and calcium phosphate)
• lodge in renal pelvis
• damage ureters and urethra while passing through system
Treatment:
• ultrasound (powerful focused beam breaks up the stones)
• surgery in extreme cases
See Fig 2 p 358

Diabetes mellitus:

Cause -> Islets of Langerhans beta cells (pancreas) produce inadequate insulin
• in liver: insulin signals conversion of excess glucose -> glycogen (storage)
When there is not enough insulin:
• proxiaml tubule cannot reabsorb all the excess glucose in the blood -> glucose in filtrate draws H2O INTO the nephrons (by osmosis)
Result:
• excess urine volume
• thirst (to replace lost H2O)
• loss of glucose --> anemia
Disease is now controlled by insulin injections.
NOTE: This disease is covered in more detail in the endocrine section of the course.

Diabetes Insipidus (NOTE: This is NOT a form of diabetes mellitis!!!)

Cause -> destruction of ADH-producing cells OR destruction of nerves from hypothalamus to the pituitary gland.
Result:
• No ADH released (therefore H2O is not reabsorbed in nephrons)
• urine output increases (up to 20L/day!!)
• thirst (to replace lost water)

Brights Disease (Nephritis):

• group of diseases that cause inflammation of the nephrons
• proteins leak into the damaged nephrons -> draws H2O into the nephrons (by osmosis)-> excessive urination

Dialysis: Used where kidney function is impared -> mimics function of the nephrons.
2 Types:
1. Hemodialysis
• ~4hr session
• must be repeated 2 - 3 times /week
• uses semi-permiable membrane + fluid mixtures to mimic kidney function
• blood flow: radial artery -> dialysis machine -> vein
2. Peritoneal Dialysis
• ~2L of dialysis fliuds are pumped into abdominal cavity
• peritoneal membrane acts as semi-permiable membrane
• after 2 - 6hr fluid is drained
• may be repeated several times/day
• can be carried out at home.

See Fig.3 p359

Kidney Transplant
• over 85% success rate
• kidney is transplanted into groin
->connected to femoral artery and vein
-> ureter connected to bladder
• single kidney can function for entire body (redundancy)
Possible Problems:
•rejection -> controlled with immune-supression drugs.

See Fig5 and Fig 6 p361



Kidneys 3      posted 10-31-2007
Regulation of Blood Pressure

**Kidneys play a PARTIAL role in regulating blood pressure (BP)**

Sensor
Juxtaglomerular Apparatus (pressure-sensitive cells in lining of afferent arteriole)

If BP is LOW:
• renin released (by juxtaglomerular apparatus)
• renin converts blood protein angiotensinogen (inactive form) into angiotensin (active form)
• angiotensin has two effects:
1. blood vessels constrict ---> raises blood pressure.
2. causes adrenal glands to release aldosterone -> nephrons (regulator) increase reabsorbtion of Na+ ions -> H2O follows Na+ (by osmosis)-> H2O reabsorbed into blood -> blood volume increases -> BP increases.

Feedback:
• BP rises
• juxtaglomerular apparatus stops secreting renin.

Note: See Fig 2 p354

pH Balance

Accumulation of excess H+ ions (from cellular metabolism) is the common condition -> causes blood acidosis (low pH)
• body pH remains constant between 7.3 and 7.5

Controller
• cells lining the nephrons

H2O + CO2 <--> H2CO3(carbonic acid) <--> HCO3- (bicarbonate ion) + H+

• H+ ions are excreated by two methods:
1. combined with nitrogen (from deaminated amino acids) --> NH3 (amonia)-> excreated in urine
2. combined with phosphate ions --> HPO4 -2 -> excreted in urine

NOTE:
•bicarbonate ions (HCO3-)are now combined with excess H+ ions to lower blood pH

HCO3- + H+ --> H2CO3 --> H2O + CO2 (CO2 exhaled in lungs).

See Fig. 3 on p355

Kidneys 2      posted 10-30-2007
WATER BALANCE

Increased exercise
or decreased intake ---> decreased urine output
Increased warter intake ---> increased urine output

1. Monitor: Osmoreceptors in the hypothalamus
Water loss (blood) -> increased concentration of solutes (hypertonic environ.) -> osmoreceptor cells shrink (by osmosis) -> send nerve signal to pituitary (Also triggers thirst sensation)

2. Controller: Antidiuretic hormone (ADH)
• produced in the hypothalamus
• stored in the pituitary gland
• released into blood stream -> kidneys
when released:
Kidneys increase water reabsorbtion -> more water retained -> urine more concentrated

#. Regulator Nephrons
NOTE: 85% of all water is reabsorbed in the proximal tubules (passive - you have NO control over this)
Remaining 15%:
• No ADH present -> excreted (lost)
• ADH present -> distal tubule becomes more permeable to H2O -> NaCl in the extra cellular fluid draws water out of the nephron (into the ECF) by osmosis -> water moves from ECF into the blood stream (osmosis)

Feedback:
As blood water content increases -> osmoreceptors (in hypothalamus) swell (hypotonic environment) -> Signal to pituitary (to release ADH) stops.
Result:
• more water excreted (no reabsorption in distal tubule)
• urine becomes more dilute (higher H2O content)

NOTES:
• know the diagrams on p350. Know what moves passively and what moves actively.
• remember - you cannot actively pump H2O out of the nephron, but if you actively pump NaCl out, the H2O will follow (by diffusion)!!!



Kidneys - Note 1      posted 10-29-2007
NOTE: These are only the "Essential Basics" of this unit. It would be expected that you will read Ch 7 and make thorough notes on this material before attempting the test.

Excretory System (Homeostasis)

Production of Wastes (catabolism)
• Large organic molicules -> small organic molecules.
-> prod. energy (ATP, heat)
Small Molecules
NH3 (ammonia) -> from deamination of amino acids (proteins) - very toxic - 0.005mg/L can cause death!!!
2 NH3 + CO2 ----> NH2-(C=O)- NH2 (urea) + H2O
Urea is 100 000X LESS toxic than ammonia
• 330mg/L can be present in the blood.
• excreted as urine.
Also...
Uric acid
-> from catabolism of nucleic acids
-> in higher apes (and a few other mammals)
• common in birds
Gout
• uric acid crystals lodge in the joints -> pain, swelling, inflammation

Other Wastes:
• Carbon dioxide (CO2) -> prod. by cellular respiration
-> dissolves into blood -> exhaled by lungs.

Functions of the Kidneys:
1. Filtration and excretion of wastes.
2. Control of water balance.
3. Control of blood pH

Filtration of Wastes.
• Occurs in the glomerulus and nephrons. (See Fig2 p347)

Glomerulus
• small caplliary bed -> VERY high blood pressure 8kPa (~2kPa in normal capilliary beds) -> ~20% of blood plasma "leaks out" through capilliary walls.
NOTE: Large particles can NOT leak out!
• plasma proteins
• red blood cells
• platelets

Bowman's Capsule
• Forms end of nephron
• Surrounds the end of the nephron -> absorbs fluid leaked from the glomerulus.

REABSORBTION
Volume of filtrate = 120mL/min.
Would Require -> void the bladder every 3 to 4 min!!
-> 1L of water intake every 10min to replace water losses.
*** out of every 120mL of filtrate, 119mL is reabsorbed in thenephron -> only ~1mL/min of urine is produced.