- What is the reason that marine reptile tails go side to side, even with extinct reptiles, while marine mammal tails go up and down? Is it morphological or behavioral?
Amphibians and, to a lesser extent, reptiles retain the lateral undulation seen in fish. Mammals are more highly specialized for terrestrial locomotion and have dorso-ventral flexion of the vertebral column. So marine representatives of each group reflect this—
Barbara Pleasant
Extremely good question!!
Well.... - I'm not a zoologist, nor do I play one on television, but I suspect that this difference is anatomical. Marine/aquatic reptiles are derived from fish-like ancestors early in the vertebrate radiation, and likely retain the side-to-side sinusoidal motion seen in "basal' chordates, chondrichthyans and osteichthyans. As you note, caecilians,, salamanders, lizards (and derived "lizards" - the snakes; "the Squamates") all share this sinusoidal walking/slithering mode of locomotion as they are terrestrial tetrapods, or derived from tetrapods (i.e. loss of legs in snakes).
Recall that aquatic/marine mammals have evolutionary histories that included a terrestrial phase, prior to their return to the water where this dorsiventral orientation of body function in mammals (quadrupedal locomotion) became developed differently in mammals than in lower quadrupeds. Since the aquatic habit of marine mammals is secondarily derived from terrestrial forms, the modified mammal dorsiventral locomotion mode is likely preserved in the "up and down" motion of flukes, since these are derived and modified hindlimbs and caudal appendages.
I am cc'ing this reply to a local expert, Dr. Barbara Pleasants, who teaches chordate anatomy, and can probably shed a better light on this explanation than I can.....I hope I am at least close in my interpretation of these differences.
Robert Wallace
- What are Ostracoderms, and how do they relate to the other fish groups?
Lecture 3: origin of fish had a slide on Ostracoderms right after lamprey and hagfish.
- What does fossorial mean?
Digging or burrowing (Dictionary.com)
- How does the orn prefix of ornithischia tie in with birds?
Ornithology: the branch of zoology that deals with birds
Ornith: bird
(Dictionary.com)
- How are members of order Ornithischia “bird-hipped?”
Dr. Adams: see fig. 7.15 of text. Essentially, the pubis bone rotates
posteriorly to be parallel with the ischium. This was not the
condition of saurischians, which had a more triangular arrangement.
Jacque: Although not really emphasized in class, the Saurischians were “reptile-hipped.” The key here is that the “bird-hipped” description of Ornithischians does not refer to any fusion in the hip bones—it is just a way to say, not “reptile-hipped.” The term “bird-hipped” refers to the arrangement of the three bones that compose the hip. Like Dr. Adams mentioned, Saurischians had three bones arranged in a triangle-shape while in Ornithischians, twoof the three hip bones were parallel.
- Can bat wings be defined as patagiums?
Patagium: a wing membrane extending between the body and a limb to form a wing or a wing-like extention as in a bat...
(Dictionary.com)
- Is carapace the correct spelling for the top of a turtle shell?
Dr. Adams: Carapace is correct.
- Is Pleisiosaurs the correct spelling and not plesiosaurs?
Dr. Adams: The spelling in the notes—not on the tree, is correct: Plesiosaurs.
- The notes say that mammal eggs are more similar to reptile eggs than to bird eggs. What details are being compared?
Dr. Adams:structural similarities to reptile eggs: large yolk and a leathery shell
- When reviewing paraphyletic, monophyletic and polyphyletic, we wondered what would happen if the ancestors had a name that didn't apply to any of the decedents. Is there an answer for this?
Dr. Adams: Good question. I am not sure that this has actually ever happened. About the only thing I can think of is something called 'anagenesis.' This is where one species evolves from another species, but the first species no longer exists (think of a single line through time, first called 1 thing and then called something else). Actually, this concept is rather controversial, but it is in the literature.
- From lecture 13
:
This image suggests that giraffes have antlers—not true. If you read the caption in your book, (page 277) they are showing antler formation accompanied by a random insert of a mammal with horns. You may also be interested in page 299 of your book which shows that elephant tusks and walrus tusks are actually teeth!
- Birds have a dermis, right?
Dr. Adams: Yes.
- Do reptiles have glands?
Dr. Adams: Very few. Lizards have femoral glands, and some turtles/crocs have scent glands
- Are antlers derived from the dermis or the epidermis?
Dr. Adams: Neither. They are an outgrowth of the skull (skeletal material)
- What vertebrates have chromatophores?
Dr. Adams: All vertebrates have them, but mammals and birds only have
Melanocytes(From Jacque: These are one kind of chromatophores—see question 20) which give us our color
- Female impala do not have "horns.” Are they an exception to the definition of ‘horns’ the way that caribou are an exception to antlers?
Dr. Adams: Antlers are in cervid species and only in males, except the Caribou. Horns are found in bovids (includes impala). In some species both sexes have horns, while in others only 1 sex havehorns.
- Do giraffe horns keep growing? They seem small.
Dr. Adams: Giraffe horns are different. They are bony protrusions covered in
skin, and don't generally keep growing, nor are they shed.
- The diurnal rhythm is the same as the circadian rhythm, right?
Dr. Adams: yes.
- Males have some estrogen, too, right? Is it produced in the testes?
Dr. Adams: Yes, males can have a small amount. Not sure where it is produced or how.
- Is melonoma related to the melatin? Or why are thesewords so similar?
Dr. Adams: melanoma is a malignant tumor in MELANOCYTES (chromatophores).
Melanin is the primary compound in meolanocytes.
- Is melatonin related to melanin?
Dr. Adams: No, melatonin and melanin are not related chemically, though both deal with the body's response to light (one for diurnal cycles and one for 'tanning').
- Can you remind me what it means to have the corpuscle adjust? Does it meanthat the nerves stop firing or that the brain is ignoring the message?
Dr. Adams: Typically, the nerves stop firing.
Jacque from (dictionray.com): Corpuscle: A rounded globular mass of cells, such as the pressure receptor on certain nerve endings.
- Why do nodes of Ranvier exist? Why isn't the whole axon myelinated?
Dr. Adams: If the axon is completely myelinated, there is no way the signal can propagate. Remember that the signal is based on the membrane potential: the charge differential inside and outside the membrane. For myelinated axons, this only happens at the nodes in between the Schwan cells.
- Myelin isn't found in invertebrates right? Where does it show up in the
vertebrates?
Dr. Adams: Invertebrates lack a myelin sheath on their axons.
Jacque: I followed up later, and he thinks that vertebrates have myelin and that the transition to having myelin occurred between inverts and verts.
- Is there a reason that the myelin is oblong instead a perfectly round
circle? Or is this just an artist's depiction?
Dr. Adams: None that I am aware of (and yes, I believe this is an artist's rendition).
- Do all nerves have myelin around them?
Dr. Adams: Yes, I believe so.
- In the desert, is it fair to say that smaller organisms struggle with water loss more than large organisms? If so, do the smaller organisms have more ways of avoiding water loss than the large organisms?
Dr. Adams: Yes, hence certain adaptations, such as convoluted nasal passages in the kangaroo rat (to keep moisture in the body).
- Do flying frogs have a patagium?
Dr. Adams: No, we depend on form, not function, to define a patagium, and the webbing is not large enough.
- What is an example of a chemical synapse? (in contrast to the electrical example of an escape reaction).
Dr. Adams: There are many chemical synapses in the human brain for example.
- Is our hair guard hair or under hair?
Dr. Adams: Not sure if we have guard hair or under hair.
Bill Clark: Mammals have a great variety of adaptations to their hair and I'm not sure you can say that humans have one kind or another. I might say that human hair would be considered under-hair but only because it doesn't function like guard hair. Guard hairs are designed to protect under hair in some mammals. They are evolved into specialized structures like vibrissae (whiskers). While under-hair (on other mammals it's often called fur) usually is pigmented (dark with melanin), guard hairs also take on different pigments for coloration and pattern (skunks). Specialized guard hairs have evolved for defense (porcupines), and wool (curly guard hairs like in sheep), and impressive display (lion's mane).
Clearly humans have evolved somewhat different hair characteristics on parts of our bodies like our heads. Not only does the greater density of hair there keep us warm (at least it kept cavemen warm), we comb it, spike it, perm it, color it, etc to function in display just like other mammals.
- If vertebrates defend territories, do they spend more time in theirterritories relative to their home range?
Dr. Adams: Yes.
- Can vertebrates have more than one territory?
Dr. Adams: Actually, I'm not sure, but my guess is no. Because a territory is defended, it is difficult to imagine a scenario where they could simultaneously defend 2 locations. Home ranges is another story
- Is there a certain amount of time a vertebrate has to spend somewhere before it's included in their home range?
Dr. Adams: This is a good question... without a good answer. As a concept, it is up to the animal to determine what it's home range is. For the scientist, it is thus a matter of them figuring out what the animal is doing. I'm sure that there are definitions out there for how long an animal must be in a location before it can be considered a home range, but my guess is that definition changes from species to species.
- Obviously, territories are 'marked' to help defend them. (I think we were referring to chemical displays here). Are home ranges marked, too?
Dr. Adams: Typically not.
- What is the difference between an inclusive and exclusive boundary?
Dr. Adams: An inclusive boundary is a maximum estimated size. For instance, if ALL locations where you find individual X are used to calculate the polygon for a home range, then you are using an inclusive approach (i.e. use all the data). An exclusive approach would be analogous to using only those locations where you have a > 90% chance of finding the animal (or a 75%... whatever your personal cut-off value is). Thus, it is more of a conservative estimate, as it excludes some locations which may not be part of the home range, but are more transient points between parts of the home range.
Jacque: To illustrate the inclusive/exclusive boundary point, I want to provide an example. If we find many places (represented by dots) where a bobcat has been, we can connect the outside dots to create a polygon (polygon approach). This polygon would be an inclusive boundary if everything between the points is considered the home range. This polygon is exclusive if bodies of water are excluded from the polygon. Since it is unlikely that the bobcat will be in the water (even though the water is in the home range) the body of water would essentially be crossed out of the home range.
Do not consider inclusive/exclusive to be associated with Dr. Adams’ illustration in class. He discussed the polygon approach (which I reviewed above) and the quadrant approach. Dots represent places where a vertebrate has been in both approaches. However, in the quadrant approach, a map is divided into a grid. Any rectangle within the grid that contains a dot is considered to be part of the home range. So one dot causes a whole rectangle to be added to the home range area. This approach is meant to cover the idea that a vertebrate does not leap between the dots where its location is recorded—this approach assumes that the vertebrate spent time near the dot as well.
- How far can electric signals go? Would it be farther than tactile communication and unobstructed visual communication?
Dr. Adams: Yes
- When talking about acoustical properties, would intensity essentially be the same as loudness?
Dr. Adams: Yes
- Can you think of two examples: one where a vertebrate uses wave tactile communication and one where a vertebrate uses vibrations tactile communication?
Jacque: Dr. Adams initially couldn’t think of any, but he later said that our examples from SI were acceptable, see 39 and 40.
- Would an example of wave tactile communication be schooling fish?
Dr. Adams: Yes, I suppose one could say that
- Would an example of vibration tactile communication be a snake receiving vibrations from the ground?
Dr. Adams: Yes, the snake example is a good one.
- When talking about allometry, we said that metabolic rate can be measured by measuring oxygen consumption and by measuring energy consumed. Would one measure energy consumption by simply noting how much a vertebrate ate?
Dr. Adams: Yes, that is one way (of course, you need to supply the food of known caloric properties to do a direct translation).
- Do snakes have a breeding season?
Dr. Adams: Some do, yes.
- Do you know of a vertebrate that exhibits protoandry? (perhaps the name of the fish your wife spoke about)?
Dr. Adams: Off the top of my head, no.
- Stereotypically, inbreeding is bad. But some recessive alleles could carry good traits, right?
Dr. Adams: Agh, good point: some recessive alleles do carry beneficial traits. However, the vast majority are alleles of negative effect, and an increase of inbreeding 'exposes' them by generating homozygous recessive individuals.
- When vertebrates needs energy for shivering, can they stop or reduce anabolic processes to conserve energy?
Dr. Adams: Not typically.