Evolution, second part

1.  A, C, D

2. There must be phenotypic variation within the population.  It must be due at least in part to genetic variation among individuals .  The phenotypic variation must cause differences in survival or reproduction.

3.  A, C, D

4.  Repeated and constant exposure to a strong source of mortality, such as the death-causing Bt. protein, will rapidly lead to evolution of resistant phenotypes in the target pests.

5.  Repeated and constant exposure to a strong source of mortality, such as antibiotics, will rapidly lead to evolution of resistant phenotypes in bacteria.
 

Evolutionary patterns
1.  Our understanding of the evolutionary relationships among the different bacteria is rudamentary.  This results in a "poorly resolved" or bushy tree.

2.   The Hemichordata (acorn worms and pterogranchs) are the sister group (most closely related group) to the sea urchins, star fish, and other Echinodermata.

3.  The Filicopsida (ferns) are the living group most closely related to the seed plants (Spermatopsida).

4.  In my opinion, the close evolutionary relationship between fungi and animals is most surprising;  until very recently, the fungi were assumed to be more closely related to the plants.  Note that there is no single right answer to this question!

5.  The trees shown (there are three of them) are all models of the possible evolutionary relationships among these three groups.  Note that there are three groups, and thus three possible relationships - and all three have been postulated.  For this reason, the evolutionary relationships presented at the top of the page are represented as a "bush".  No one is sure at this time which two of the three groups are more closely related to each other.

6.  A

7.  On the branch between the "root" of the tree and where peccary and pig branch off from the other mammals.

8.  Note - here I present only a few advantages and disadvantages for each type of data.

Behavior, anatomy and physiology:
disadvantages - you need living or freshly dead animals (behavior and physiology are difficult to study in museum collections!).
                      - behavior and physiology are often strongly influenced by environmental factors, and thus require experimental testing
                      - sometimes differentiating between homology and convergent evolution is difficult
                      - behavior and physiology are exceedingly difficult, and controversial, to infer from fossil remnants
advantages:   -  behavior and physiology are characteristics that are exceedingly rapidly evolving in many organisms
                     - anatomical data are readily available both in museum specimens, fossils, and written descriptions

molecular data (gene sequences)
disadvantages - you need living or freshly dead, well preserved material (in some cases, museum specimens do have intact DNA)
                    -  obtaining sequences can be very expensive (although increasingly less so)
                    - sequences can be highly variable among individuals;  recognizing meaningful patterns within the variation can be difficult
advantages   - the data are not influenced by environmental factors
              - choosing the correct gene or set of genes will allow resolution at different levels within a tree (some genes change much more slowly than others)
               - some genes are very, very old, allowing reconstruction of relationships among very distantly related groups (such as fungi, animals, plants)

fossils
disadvantages - highly biased samples:  fossilization is rare, so only common organisms are likely to be represented in the fossil record
                      - highly biased samples (2):  fossilization occurs most commonly with hard parts, so soft organisms like worms are rarely represented
                      -  distinguishing homologous and convergent evolution can be difficult
                      - data generally restricted to anatomical features
advantages - these are the only data that actually reveal what an ancestral (root) group may have looked like
                  - these are the only data that reveal past levels of biological diversity in any one group

Deep in a tree, the most useful data generally are DNA sequences for highly conserved genes (these are genes where most mutations are not tolerated), and some anatomical data from extant and extinct (fossil) organisms.  High in a tree, the most useful data generally are DNA sequences for variable genes and non-coding regions such as microsatellites (where mutations are tolerated), and physiological and behavioral data from extant organisms.
Genetics
1. A B E

2. A F

3. A B C

4. His anger is not justified: he is likely heterozygous for eye color. The child has one blue allele from its mother & one blue allele from its father.

5. Mendel's law of independent assortment will not hold true if two genes are on the same chromosome. I leave it to you to figure out why.

6. A short life cycle, many offspring (high reproductive rate), inexpensive to keep.

Homeostasis

1.  B, lower in solute concentration than the cell

2. Small organisms, such as slugs and earthworms, loose water to the environment very rapidly (the water moves from the place of high water concentration (the body) to low - the air).   The waxy coating greatly reduces the loss of water, and thereby greatly increased the ability of insects and other  arthropods to live in terrestrial (land) environments ranging widely in humidity.

3.  Open circulatory systems without circulatory organs would be most common in very small organisms, where diffusion is sufficient to move nutrients, gases and wastes through the body.

4.  The much larger monitor lizard should expend much less effort on maintaining body temperature compared to the anolis lizard, because the large size (and therefore low surface-area : volume ratio) mean that it will gain and loose heat very slowly.

Bacteria, Archaea and Viruses
1.  Lateral gene transfer is the movement of genetic information between organisms that are unrelated evolutionarily (different evolutionary lineages).  See pg. 488.
2.  Organisms may be much  more tolerant of mutations in metabolic pathways, and these pathways may be much more likely to move "laterally" among groups.  Genes involved in information processing (i.e., DNA replication, transcription and translation) may be much more conserved within a group, and less likely to move laterally among groups.
3.  The release of molecular oxygen as a biproduct of photosynthesis resulted in availability of this compound as a final electron acceptor in the synthesis of ATP.  It is a very powerful (highly oxidized) electron acceptor, and this means that far more energy (more ATPs) are produced per electron donated.  The increased energetic efficiency of this pathway increased metabolic rates, and likely made larger cells and later multicellularity possible.
4.  Ammonia and other nitrogenous compounds released into fields as fertilizers are passed into the Mississippi river drainage as nitrates, and deposited off the coast of Louisiana.  These cause rapid population growth of cyanobacteria and algae off the coast.  When these microorganisms die, the decomposition of their bodies uses up most of the free molecular oxygen dissoved in the water locally, resulting in a biological "dead" zone.
5.  there is no "right" answer to this, just better (and worse) arguments.
6.  Increased virulence (disease-causing capacity) causes hosts to feel bad and die more quickly after infection (It is believed that highly virulent parasites more easily out-compete other less virulent strains when multiple strains infect the same host).  However, dead hosts don't transmit infections very effectively, so high levels of virulence may reduce the transmission of the parasite to healthy  hosts.  Note that this is a theoretical model, and to date little data have been collected experimentally to test it.
7.  HIV mutates rapidly:  the reverse transcriptase is not very accurate (especially compared to DNA synthesis).  This means that it undergoes rapid evolution, within and among hosts, and rapidly evolves evasions to new drug treatments.

Protista

1.  Diffusion and osmosis are effective means of transporting molecules only over short distances.  The complexity of eukaryotic cells such as protista includes organelles that specialize in moving nutrients and waste products into, within, and out of the cell eliminating the reliance on diffusion and osmosis.  Therefore, these cells can be much larger in size.

2.  The bacteria and arachaea lack cytoskeletons, and therefore cannot engulf prey (cannot undergo endocytosis) the way Protistan predators like Paramecium and many  Amoebae can.

3.  Colonial protistans are made of cells that, if separated, can survive individually.  The cells composing a multicellular organism cannot survive long if separated from other cells because some degree of specialization has occurred in cell function.

4.  I leave this to you to explore.

Fungi

1.  A paraphyletic group is a group that includes some, but not all, decendents of a common ancestor.  That Zygomycota and Chytridiomycota are paraphyletic implies that the fruiting body morphologies and life cycles used to characterize these two groups evolved more than once.

2.  Haploid cells have one copy of each chromosome, diploid cells have two, and heterokaryotic cells have two nuclei (one from each parent), each nucleus being haploid.  See figure 29.4 for your answer;  note that in Basidiomycota and Ascomycota the figures are labeled as undergoing "fusion" when the myclelia are still actually heterokaryotic.   True diploidy in both these groups only occurs in the ascus or basidium.

3.  Lignin peroxidase catelyzes the removal of a single electron from a molecule of lignin, destabilizing the molecule and resulting in the degredation of the polymer into subunits.  These reactions are extreemly unpredictable, and therefore the energy lost in degredation of lignin cannot be captured by the fungus.  This is very distinct from most biological degredative processes, wherein digestive enzymes interact with specific substrates, resulting in very controlled reactions easily for energy and carbon collection.

4.  The feedback loop would have a positive (inducing) role of the presence of cellulose and negative (repressing) role of glucose.  Cellulose in the absence of glucose would induce the transcription and/or translation of genes coding for cellulose degredation, and glucose would suppress the transcription and/or translation of these genes.

5.  There are several "mutualisms" that appear to grade into parasitism.  One is the "cleaner fishes" found in many tropical coral communities:  some species will, in addition to removing parasitic arthropods, take an occational nibble of flesh from their "customers".

Plants: introduction

1.  There are multiple correct answers to this.  You ought to be able to use just about any set of data (i.e., gross morphology, histology, life cycles, reproductive structures) and develop a phylogeny that pretty closely resembles those presented in the text book.

2.  Cuticle:  prevents water loss;  stomata:  allow gas exchange when epidermal tissues are cuticle - coated;  pollen:  allows transfer of male gametes without water;  vascular tissue:  transport within the plant of water and nutrients, eliminating dependence upon diffusion and external water;  flowers:  not vital for survival on dry land.  Plants probably could not have "invaded" terrestrial habitats without the evolution of cuticle and stomata, so those are likely the most important, paving the way as it were for the evolution of plants that could survive increasingly challenging environments (thereby escaping competition from other plants).

3.  The group with the "latest innovations" is more successful at obtaining water, nutrients and light, and can competitively exclude the group with the earlier set of "innovations".  For instance, roots are more effective than diffusion over the entire body, so ferns can out - compete mosses for water and nutrients.  Because of the presence of vascular tissue and true leaves,  ferns can also get larger and outcompete mosses for sunlight.

4.  Gas exchange necessarily increases water loss, because it exposes unprotected tissue to the dry air.  Water is a vital component of photosynthesis, so keeping the photosynthetic apparatus isolated from the gas exchange area would decrease the rate of water loss by the tissues.
 

Plants anatomy

1.  mosses:  parenchyma and collencyma, no vessels or tracheids.  Functional groups:  epidermal, ground tissue
ferns:  all three functional groups of plant cells (but no vessels only tracheids and sieve tube members), all three functional groups of tissue
herbaceous angiosperms:  all three functional groups of plant cells (vessels instead of tracheids), all three functional groups of tissue.

2.  Primary growth is "up" - elongation of stems and roots.  Secondary growth is "out" - widening of stems and roots.

3.  Pluripotent and totipotent are adjectives describing the ability of a cell to produce daughter cells of diverse developmental fate (diverse specialization).  Pluripotent cells can develop into diverse cell types, but not all possible tissues in an organism.  Totipotent cells can produce daughters that can develop into all cell types in the organism.

4.  They are sedentary, and must respond to their environment and environmental changes in situ.  These responses may involve changes in body form such as production of new branches or new roots, which might require development of novel structures - for instance, roots where a branch touches the ground.

5.  In shady environments, a plant may invest more into stems and leaves compared to a sunny environment with roots showing the opposite pattern.  In moisture gradients, there may be more investment into roots (and less into stems and leaves) with increasingly dry conditions.

6.  Variables to be controlled for to test the model "variation in species X is due to genetic variation":  all environmental variables (soil, light, water) and age variables (all plants should be of the same age and developmental stage).

Variables to be controlled for to test the model "variation in species X is due to environmental variation":  genetic variables (use clones or randomize if cloning is not possible), age variables.

7.  B

8.  Not the best test to make this distinction as both the environment from which you collected the seedlings and the genetic background of the seedlings are uncontrolled for (although the latter is randomized across treatments).

9.  top of leaves

10.  (secondary) xylem
 

Plant transport
 

1.  The osmotic or solute potential of a fluid is measured relative to pure water, which is defined as having a solute potential of zero.  By definition, the movement of water into solutions less pure than distilled water is measured as a negative number.

2.  In the xylem, osmosis "loads" water into the vessels or tracheids.  In phloem, osmosis causes water to move into the phloem after sucrose has been "loaded" by active transport, increasing the pressure potential and causing the fluid to move away from the source.

3.  Xylem fluids consist mostly of water and minerals, with little protein or sugar content.  Feeding exclusively on this fluid means that even a small organism like an insect will need a lot of time to reach maturity.  Phloem fluids include relatively high quantitites of sugar as well as some proteins (which are also transported in the phloem).  Thus this food source is much richer and the insects require much less time to acquire the nutrients necessary for maturity.

4.  C, D, E, F

5.  B, C, D, E, F

6.  B, E

7.  The protoplast would compromise the hydrogen bonds among water molecules,  and between the water molecules and the walls of the tracheids or vessel elements.

Plant senses

1.  plant species:  controlled for (both species in all three treatments);  light quantity:  controlled for;  light quality:  manipulated;  plant genotype:  ambiguous (one would hope that either all specimens of each species were clones, or that the genotype was randomized across the treatments;  the text does not specify);  rate of elongation:  measured;  position of individual in chamber: randomized (implied by question in figure description).

2.  I would expect there to be some sort of touch- (or pressure) sensitive sensory system. However, this is just my opinion.  Other possibilities include a chemosensory receptor - this has the down-side that chemosensory systems are usually very specific and reliance on this alone might limit recognition of all possible hosts.   In either case, I would expect it to be membrane-bound and located in the epidermis of the stem (there are no leaves in this plant).   There are various pathways that could be taken to test these hypotheses;  if you want to discuss your particular experiment(s) then email me!

3.  A knock-out mutation is a mutation that creates a gene that is completelly disfunctional.  Most often, it is in the protein coding region of the gene in question, although in some cases it is in the regulatory regions for that gene (making it so the gene cannot be "turned on" for transcription).  In the heterozygous condition, it may have little effect on the protein composition of the plants, because the functioning copy may be able to produce enough gene product to compensate.  In this case, it would be fully recessive.  In the homozygous recessive genotype, no protein product of this gene would be present in the plant.

You test for the presence of a knock-out mutation by examining the homozygous mutant for response(s) that would be mediated by the gene in question, and by testing the tissues for the protein product of the gene you are interested in.

4.  In order to fully verify that a particular protein is the sensory system that is being studied (or at least a component thereof), the scientist needs to remove it from the plant and then test for the predicted change in response with and without the protein.  Merely determining that a protein is in one conformation when a plant has one behavior, and a different conformation when the plant has a different behavior, is necessary but not sufficient evidence that the protein is the actual sensory receptor for the response.

5.  If the signal transduction pathway has been compromised by the effort to create a knock-out mutation, or if the hormone coding gene has been mutated, the mutant would have the expected behavior without the genotype showing alteration in the sensory protein.  The wrong protein would be identified with the sensory system.

Plant hormones

1.  Synergistic interactions are where the presence of both (or multiple) hormones, the affect is increased.  Antagonistic interactions are where the presence of multiple hormones decreases the affect of each (they work in opposition).

2.  This is a thought question.

3.  Goal present (to understand the cause of the change from stem meristem to inflorescence meristem)
Model:  there is a chemical cue (hormone) transported in the vascular tissue produced in response to appropriate light cues
Data:  exposure of one leaf to a light would cause flowering of all connected tissue even though they were genetically unrelated
Evaluation;  the data support the model
Revision:  none needed

4.  light quality:  controlled for (somewhat ambiguous);  soil quality:  controlled for (one "super plant");  light quantity:  controlled for total light intensity (somewhat ambiguous), manipulated day length;  plant genotype: manipulated;  hormone type:  neither manipulated, nor randomized, nor measured (unimportant to this study)

5.  Since the plants were of different genotypes, it showed that the message could travel through the vascular tissue and was independent of the genetic make-up of the individual stem.

6.  E;  7.  A;  8.  C, F;  9.  B;  10.  D

11.  Hormone systems wherein alteration could result in miniaturation include:

Auxin - shift point at which a response is initiated (change sensitivity)
Gibberelins - reduce quantity of one or several of these hormones to reduce size
 -- increase quantity of one or several of these hormones to stimulate flowering at a smaller or less mature size
Abscisic acids - increase quantity of one or several of these growth- inhibiting hormones

Plant reproduction

1.  Alternation of generations refers to the life history pattern where there are two independent, different types of individuals that occur alternately in the life cycle.  In the plants, it si the gametophyte (haploid) alternating with the sporophyte (diploid).  (Similarly complex life histories are found in some arthropods and marine invertebrates).

2.  The cues that a plant uses to determine when to flower or when to germinate are expected to have evolved to be cues that will favor successful reproduction:  Cues that are related to the best time for pollination, the best physiological conditions for fruit development, etc.  The cues for flowering and germination might be the same in species found in situations where seeds do not enter dormancy - either short-generation time temperate plants (where there are multiple generations in a single growing season), or in areas of the tropics where the rainy season is long enough to allow germination and establishment of the seedling before the dry season begins.  The cues would be expected to be different any place where seeds enter a dormant period to survive drought, cold, or other conditions that would jepardize seedling survival.

3.  3.  Label each of the following as (A) parent sporophyte tissue  (B) parent gametophyte tissue  (C) offspring sporophyte tissue (D) ambiguous

stigma -- parent sporophyte
ovary-- parent sporophyte
ovule-- parent sporophyte
stamen-- parent sporophyte
megaspore - parent gametophyte
egg- parent gametophyte
micropile - ambiguous
microspore- parent gametophyte
generative cell- parent gametophyte
sperm- parent gametophyte
endosperm-- offspring sporophyte
zygote-- offspring sporophyte

4. - if you have problems with this, email me.  This is a straight-forward Punnet's square answer (assume that the genes involved are *not* linked).

5.  All clonaly produced offspring will be identical.

6.  Limiting access to only one or a few pollinators improves the chances that a visiting pollinator is coming from another flower of the same species, which in turn increases the chance that this pollinator will be carrying pollen from the same species and will in turn carry this individual flower's pllen to another flower of the same species.

7.  Having only one or two flowers that offer nectar rewards limites selfing, because the pollinators will bemoving among individual plants not among flowers within a plant.

8.  Self pollinating is cheap in terms of pay-off to pollenators (zero) and least effective at producing genetically diverse offspring.  It doesn't waste a lot of pollen however.

Wind pollinating is also cheap for pay-off to pollenators (zero), and quite effective at producing genetically diverse offspring.  However, it is very wasteful for pollen:  there is no "guidance" to where the pollen will land, and thus large quantities likely must be produced to assure the arrival of any male gametophytes at a conspecific female gametophyte.

Animal pollenation is expensive int erms of pay-off to pollenators (pollen and nectar), quite effective at producing genetically diverse offspring, and the less wasteful for pollen so long as the pollenators are "faithful" and visit a series of flowers of the same species on a given foraging trip.  It may not produce quite the ssame range of genetically diverse offspring as wind pollenation.
 

Animals:  introduction

1. Dissociate the cells:  if the organism is a multicellular one, the cells will not survive if separated (many sponges, the cells will re-aggregate to reform the individual!);  if the organism is a colony of unicellular protists, the cells will survive if separated.

2.  All animals are derived from a single common ancester, and the group "Animalia" includes all decendents of that ancester.  The group Protista does not include all decendents of the common ancestor:  fungi, animals, and plants branch off in the midst of Protista.

3.  Both exoskeletons and endoskeletons have descrete joints, allowing movement to be more directed than the hydrostatic skeleton permits.  There are likely other valid answers to this question.

4.  Bilaterally-symmetrical animals have a well-defined "head" or "front end", and they can move forward (that end first), allowing concentration of the sensory organs in the area that first encounters a new environment.  This makes foraging much more efficient for an active, mobile animal, and perhaps increases the diversity of niches that these foragers can enter (types of food, habitats, time of day for foraging, etc.).

5.  Radial symmetry is favored for animals with sessile life-styles because they are waiting for things to come to them:  with radial symmetry, sensory organs can be deployed in all directions, improving the efficiency with which both prey and predators are detected.

6.  Protostomate:  spiral cleavage, point of gastrulation becomes mouth;  coelom develops from splitting  of mesoderm. (note this is a correction)
Deuterostomate:  radial cleavage, point of gastrulation becomes anus, coelom develops from outpouching of presumptive gut.  Note that this is a correction.
I would argue that neither group is more evolutionarily advanced:  the deuterostomate lineages include the arguably more complex vertebrates, but the protostomate lineages include the most diverse animal group (the insects).

7.  Coelomate animals have coeloms that are entirely lined with mesoderm, so that the gut is surrounded by muscle and suspended by dorsal and ventral tissues (mesentary).  The pseudocoelomate animals have coeloms that are between the gut (endoderm) and the muscle wall (mesoderm), with no mesentary tissues.  The coelomate body "plan" may be advantageous because of the muscles around the gut (allowing independent muscle contractions to move material in the digestive tract), because the mesentary tissues keep organs in place, and because in organisms without hard skeletal elements, a fully-muscle lined coelom is better controlled as a hydrostatic skeleton.   The pseudocoelomate body plan is traditionally considered ancestral because it is less complex than the coelomate body plan;  this hypothesis has been supported by recent phylogenetic reconstructions using DNA sequencing.

8.  Vertebrates are drawn at the far right through tradition, and this does not reflect a position in the "ancestral/derived" continuum. at least with respect to the echinoderms, and to the protostomate lineages.

9.  Acoelomate:  flat worms (planaria, tape worms, etc).  Psuedocoelomate:  nematodes (round worms), rotifers, bryozoans (frequently mistaken for seaweed!).  Protostomate:  insects, crustacea, molluscs, arachnids, among others;  Coelomate:  echinoderms (starfish, sea urchins, crinoids and sea cucumbers, among others), vertebrates.

10.  The anolis will gain and loose heat more rapidly, so would be expected to monitor more closely, and move more frequently between sun and shade than the monitor lizard.

11.  C (meiosis), E (geese need water).

Adaptation

1.  Natural selection is differential survival or reproduction based upon genetically-based phenotypic variation among individuals.  Evolution is change in the mean phenotype of a population:  you cannot measure the mean of an individual, and you cannot (for our purposes!) have differential survival or reproduction among populations.  An adaptation can be considered to be a phenotype that increases the differential survival or reproduction of an individual in it's natural habitat (improved fitness) and is best measured by comparison to other individuals or species in the same habitats with different phenotypes.  A population or a species becomes "adapted" through the process of natural selection among individuals.  Acclimation is the process whereby an individual adjusts its phenotype to suit the habitat in which it occurs.  Note that acclimation can be an adaptation.

2.  This is meant to provoke thought, and there is no one right answer.

3.  Evolution through natural selection requires genetic variation among individuals that produces phenotypic variation among individuals, and the phenotypic variation yeilds differences in fitness.  If there is no genetic variation for a particular characteristic, that aspect of phenotype cannot change through natural selection.  If a gene does not exist for a particular characteristic (such as a protein to actively transport water or oxygen), then this characteristic cannot evolve.

4.  This means that characteristics or atributes must develop from existing atributes: although feathers might make it easier for a bat to fly, they cannot simply grow feathers instead of fur.  Morphological example:  marine mammals have never evolved to have gills, but instead have evolved a suite of circulatory and respiratory adaptations of the mammalian anatomy to cope with living in an aqueous environment.  Cellular example:  there are no active pumps of water, so the movement of water must be accomplished by altering the solute gradient to favor water movement through osmosis.

5. There are many examples of these;  here to get your thoughts going are one example of each from plants.  See what you can come up with for animals!  Evolutionary (genetically based) trade-offs in plants:  seeds cannot be both light enough for wind transport and large enough to provide large endosperm stores.  Environmentally-induced trade-off in plants:  some plants will reproduce asexually, and only shift resources to sexual reproduction when the environment is good for seedling germination and survival.

Water balance
1.  You should come up with a diagram wherein the fluids at the end of the parallel veins and arteries have equal temperature, and the fluids at the ends of the counter-current veins and arteries have nearly fully exchanged their heat loads.

2.  There will not be any net water movement (no osmosis), but there will be diffusion if there are channels for the ions in question and if the solutes on either side of the membrane are different.

3.  A shark has no net loss or gain of water, but must maintain the correct electrolytes through selective secretion by the salt gland (they tend to acquire sodium chloride).  A dolphin has net loss of water and net gain of soduim chloride, and must conserve water while excreting sodium chloride.

4.  Sodium-potassium ATP ase is a transmembrane enzyme that "burns" ATP to move sodium and/or potassium against the concentration gradient into or out of the cell.  Three sodiums ions move for every 2 potassium ions.  It is located in the basal membrane of the shark gland epithelium, and this surprised biologists because it meant that the sodium was being pumped away from the gland lumen rather than into it.

5.  Biologists are assuming that oabain has narrow effects, affecting only sodium/potassium ATPase. Further question:  this is itself a model (hypothesis).  Is it testable?

6.  The molecular process of water and salt balance in insects also relies heavily on sodium/potassium ATPase.  What does this imply about the evolutionary origin of this enzyme - is it recent or ancient?

7.  exoskeleton with waxy covering, trachae can be closed, excretion of uric acid.

Excretory system

1.  In both organs, liquid is filtered into the proximal end of the tubule from the blood, and then water removed and solutes selectively removed to result in a concentrated solution.

The bird salt gland consists of straight tubules (not bent into loops, nor convoluted as in the nephron), arrayed so that the blood flow through the capillary vessels is in the opposite direction to the flow of liquid in the lumen of the tubule.  Concentration of the salt solution occurs through counter-current exchange between the tubule and the capillary, and is primarily (if not exclusively) through passive osmosis and diffusion.

 The mammalian nephron consists of a proximal tubule shortly after the fitrate enters the system, wherein the body recovers nutrients that are valuable, and deposits wastes.  The tubule then makes a hair-pin turn into and returning from the center of the kidney, the loop of Henle.  In the length of this loop, a combination of osmosis, diffusion, and active transport of salt establishes a concentration gradient from the medulla to the cortex.  The liquid in the lumen of the tubule when it returns to the medulla of the kidney is isotonic but not iso-ionic with the liquid in the proximal convoluted tubule.  Concentration of the wastes occurs when the liquid flows through the collecting tubule, which passes through the cortex and looses water due to osmosis.

2.  See table 39.1 in the text.

3.  See figure 39.9 and 39.14

4.  This is a thought question with no single right answer.

5.  The proximal tubule recovers nutrients from the blood filtrate through absorption.  Absorption can only take place at the surface of the lumen of the tubule, and hence is limited by surface area.  The tubule surface is convoluted to increase the length (and hence surface area) without greatly increasing the volume it occupies, and the cells have microvilli (see fig. 39.11).

6.  In the proximal tubule.

7.  Aldosterone was not discussed in the text and we didn't have time in class, so this will only address ADH (the two hormones are complimentary, by the way).  ADH increases the permiability of the collecting tubule, thereby increasing the amount of water recovered by the kidney.

8.  Monitoring kidney function involves sensing blood pressure at the glomerolous and monitoring the sodium ion content of the blood.

Nutrition and digestion
1.  Digestion of food by enzymes and absorption of nutrients are processes that rely heavily on diffusion, which declines rapidly with increasing surface area: volume ratio.  See figure 40.11 for the anatomical adaptations that increase surface area.  In the kidney, microvilli are present in the proximal convoluted tubule to increase the surface area for reabsorption of nutrients in the filtrate.

2.  Vertebrate herbivores that can eat a diversity of plant parts and / or a diversity of plant species will more easily meet their nutritional requirements than specialist herbivores (insects or vertebrates) that eat only one part of one plant species.

3.  You might expect the surface area:volume ratio to be much greater in the herbivore, to maximize the digestion and absorption of all available nutrients from the low-yield plant diet.  For the second part of this question, consider the relative importance of evolutionary history  and diet in the evolution of gut morphology (closely related species may be similar due to relatedness rather than diet).

4.  The leptin may not be the key hormone involved in setting the set point, and our understanding of the molecular interactions of leptin with receptors and subsequent points in the hormone cascade is lacking detail.  These results indicate that mice, while useful models, are not perfect models for understanding obesity in humans.

5.  This is a question that I leave to you to consider.

Gas exchange

1.  The energy demands of flight would favor the evolution of any anatomical features that would improve the efficiency of gas exchange.  Unidirectional air flow, greatly reducing the residual volume of air in the lungs and thereby increasing the pO2, has higher effeciency than mammalian or reptilian "sac" lungs.  Counter-current exchanges in fish improve efficiency because water is both very viscid compared to air, and has much lower pO2 than air.  The counter-current flow of water and blood maximizes the exchange of gases (particularly, the movement of oxygen into the blood).

2.  The mixiing of fresh air with the residual volume of air that is always present results in a pO2 in the lungs that is significantly lower than the pO2 of the atmosphere.

3.  Many invertebrates have copper ions in their respiratory pigments, while vertebrates have iron ions.

4.  I would expect to find respiratory pigments in insects with gills, since they must use circulation of the hemolymph to move oxygen to their tissues and this will be much more efficient if the oxygen molecules are bound to a molecule rather than dissolved in the hemolymph.

5.  No, the oxygen dissociation curve would be a simple assymtotic function (see figure 41.10a).  This is because there could be no co-operative affects among molecules.

6.  Do the exercise, and you'll see what happens.  It makes sense, because the shift you observe results in the increased release of oxygen into the tissues:  since tissue acidity increases with increased metabolism (pH goes down), and iincreased metabolism reflects increased use of oxygen by the mitochondria, this makes adaptational "sense" as well as chemical.

7.  I don't know the answer to this one, but it is an interesting phenomenon and it does make physiological sense:  the affinity of the hemoglobin for Oxygen is lowered and fever would involve increased metabolic activity, requiring more oxygen.

8.  The term oxygen reserve refers to the 75% of the oxygen that is not normally released by the hemoglobin in the tissues.   This reserve provides a source of additional oxygen should survival require sudden increased metabolic activity (production of ATP).

9.  The higher affinity of fetal hemoglobin for oxygen means that it can "pull" oxygen from the maturnal hemoglobin, allowing the mother to supply the fetus with oxygen.

10.  You would expect the dissociation curve to be steeper: there would be a higher affinity of the hemoglobin for oxygen (the curve will be to the left of the human hemoglobin curve).  This is because there is less oxygen at higher altitudes (lower pO2).

Circulation

 1.  Compare figures 41.12 and 41.15.  Also see links for echinoderms and flatworms.

2.  Both crocodiles and birds, and mammals, are descended from ancesters that had three chambered hearts.

3.  No to both questions.

4.  The septum is evolutionarily favored because it prevents mixing of oxygenated and deox; oxygenated blood.  I would expect more fully developed ventricle division in groups with greater activity levels:  active hunters rather than ambush hunters.  This will not necessarily be correlated with phylogeny because foraging "styles" are not necessarily correlated with phylogeny.

5.  The aorta and the kidney.

The nervous system

1.  Yes
2.  Actively transported:  sodium, potassium;  passively channeled:  potassium, sodium, chloride;  not moving:  organic anions
4.  First comparison:  type of neuron controlled for;  type of channel controlled for, neurotransmitter manipulated, genotype controlled for
Second comparison:  type of neurton controlled for, type of channel controlled for, neurotransmitter manipulated, genotype controlled for
Third comparison:  type of neuron manipulated, type of channel controlled for, neurotransmitter manipulated, genotype controlled for

5.  A, B, D

6.  Chemically-mediated synapse:  advantages are allows for signal summation (local processing), variable response mediated by same chemicals (neurotransmitter) allows same signal to be used in different contexts, disadvantages are slower speed of transmission.

7.  Your answer should include the following facts:

Sensory systems

note:  in content review questions, #2 correct answer is d and #5 correct answer is d
1.  Mechanoreceptors are sensory neurons that respond to motion.  Senses that utilize these organs include (but are not limited to) hearing, balance, touch, propriosensing (knowledge of where one's limbs are).

2.  A variety of correct answers, including:  Mechanoreceptors are used to monitor blood pressure.  Chemosensors are used to monitor blood chemistry.

3.  The octopus eye is very similar to the figure on pg. 835, except that the layers of neurological tissue are to the outside and the photoreceptor cells to the inside of the spherical eye.  All characteristics apart from the rhodopsin in the photoreceptor cells are the result of convergent evolution, as no common ancestor to vertebrates and octupi have this kind of eye.

4.  potassium channels.  I ask this not because I expect you to memorize such trivia, but because I think it is really interesting that there is this difference with "normal" nerve cells.  What is the explanation in the book for why opening potassium channels leads to depolarization in this system?

5.  The postsynaptic nerve membrane may depolarize or hyperpolarize in response to acetylcholine, depending upon the pair of nerves involved.  The second half of this problem is an open question.

6.  When ATP is eliminated from the system, the bond between actin and myosin becomes fixed (the myosin can only release the actin through interaction with ATP).   The bond can only be broken with the proteins start to degrade.

Hormones

1.  There are diverse correct answers for this question.  If you want to know if you are on the right track, email me.

2.  Note that this question was re-worded 26 April.
Steroids are lipid-soluble, and can freely pass through the cell membrane.  Once bound to the receptor, they interact directly with the chromasomes, influencing gene transcription. This response is relatively slow to start and stop.  Polypeptide hormones are water-soluble, and therefore cannot pass through the membrane.  They bind to cell-membrane receptors, initiating a cascade.  These hormones can lead to rapid changes in physiology, that are equally rapidly reversed.

3.  The releasing factors are hormones produced in the hypothalamus that act on other endocrine tissue.  The examples discussed in the text all concerned releasing factors that caused the anterior pituitary to release hormones, such as the gonadotropin releasing hormone that causes the release of follicule stimulating hormone and leutinizing hormone.

4.  The cascade initiated by a hormone results in signal magnification.

5.  The G proteins are intermediary messengers, transmitting information from a polypeptide hormone receptor to adenylate cyclase.  They are membrane bound.

6.  The adrenal gland cortex produces steroids involved in responses to long-term stress, that alter many aspects of physiology (basically, resetting homeostatic set-points).  It makes evolutionary sense for these massive and slowly reversed changes to be controlled by the CNS.  The adrenal gland medulla produces steroids involved in response to short-term stress such as accidents or attacks.  These responses need to be mounted rapidly, and disappated rapidly, and it makes "sense" for them to be under local control.

7.  Both insulin and glucagon are water-soluble hormones, and cascades are initiated when these hormones bind to their respective cell-membrane receptors.  Why does it make sense that these hormones are not steroids?

Note content review problem #1 correct answer is "c" not "d".

Reproduction

1.  Gametes (eggs, sperm) are produced through meiosis from stem cells referred to as spermatogonium or oogonium (sperm, egg respectively).  The meiosis of the spermatogonium produces four sperm, the meiosis of the oogonium produces one egg (the other products of each meiotic division do not mature).  The zygote is formed through the fusion of the egg and sperm nuclei, and is diploid, single-celled.

2.  Many invertebrate and some vertebrate females have sperm storage organs so that copulation can be temporally separated from fertilization (which refers specifically to the fusion of the egg and sperm).  If, as in many insects and some spiders, the sperm storage organ (spermatophore) is a blind sac (one having just one opening), it is likely that the sperm from the last male to copulate will be used first.  Thus, it may be benificial for a male to guard a female or use other means to prevent other males from mating with her.

3.  If the increased reproductive success of the male outweighed the costs in terms of decreased survival, sexual selection could lead to evolution of characteristics that compromise male survival.

4.  The sperm are less expensive physiologically, and more numerous, than the eggs in most organisms.  (Note - does this also apply to plants?  If so, when would you expect "sex-switching" plants to switch from one sex to the other?)

5.  A.  evolution of new mating signal will not occur (there is stabilizing selection for the current chemicals)
B.  evolution of new mating signal will not occur:  there is no genetic basis for variation in phenotype
C.  evolution of male size and behavior could occur, mediated by the genetically-based preferences in oviposition site expressed by mothers.

6.  calling males:  both;  satellite males:  receivers;  receptive females:  receivers

Note:  quote ("") marks refer to behaviors that may or may not be genetically determined, or may be caused by a fixed response to environment.  In other words, although I use the term "choice" and "decision", you should be aware that this is anthropomorphic and the males may not really exercise any conscious decisions.

7.  Satellite males may be the same size or smaller than calling males.  They could be the same size, if the "decision" to behave as a satellite depends primarily on the presence or absence of predators.  They could be smaller, if the "decision" to behave as a satellite depends primarily on male competition (wherein larger males are dominant).

8.  Yes, because if there is no competition, no other males singing, then females will not come.  Therefore, one would expect any male to call.  If there is competition and males are already calling, then females are being attracted and a male may "choose" to behave as a satellite.

9.  because they mimic the hormone conditions of pregnancy, and have a inhibitory affect on the hypothalamus' production of GnRH.

10.  Humans have "hidden" ovulation, with no overt phenotypic indications of when an individual is most fertile.  This makes the calendar-based "rhythm" method prone to error if any variation in cycling occurs.

11.  LH, leutinizing hormone.

12.  Pro, progesterone

13.  D

14.  C

15.  C, Follicle stimulating hormone, FSH

Immune system

1. The humoral immune response involves the B cells and the production of antibodies;  see figure 46.10 and 46.11b for full details.  The cellular immune response involves the T cells;  see figure 46. 9 and 46.11a for full details.

2.  The pathogen is the infectious organism (most often, viral, bacterial or fungal).  The antigen is a protein or other organic molecule that is part of this organism such as a protein component of the viral shell or bacterial cell membrane.  The epitope is a specific part of the organic molecule that is "recognized" by a B-cell or T-cell receptor, and that can bind to an antibody.  A processed epitope is the epitope that is presented by a B cell or phagocytotic cell on the MHC.

3.  The model of clonal selection is the concept that the body is filled with "roaming", inactive B and T cells.  If one of these cells encounters an antigen (specifically, the epitope on an antigen) that it "recognizes" (that binds to its receptor protein), it will start to produce daughter cells with identical receptors that recognize the ssame antigen.

4.  Variation in both is produced through gene splicing during cell maturation.  See figure 46.8.