FINAL EXAM - HOMEWORKS

The fish taxon that eventually evolved into both lobe-finned fish and ray-finned fish possessed an air-filled sac in its throat. It used this air bladder to [......]. In modern ray-finned fish, this air bladder is used to [......)]; in modern lobe-finned fish, it's used to [.....].

breathe (do gas exchange) float (as a swim bladder breathe (do gas exchange)

Neck bones were lost.

no

Our pelvic bones separated from our leg bones.

no

Skull bones evolved.

no

#4. (2 points) We believe that plants made it easier for animals to then colonize land. Explain how.

plants are autotrophs and thus derive their metabolism from the sun, as well as a partnership with fungi who helped facilitate their expansion on land. Animals such as arthropods are consumers, and need something to eat. If plants didn't exist on land, the land would be devoid of consumable things. Therefore, the existence of plants gave animals the nutritional landscape needed to survive.

This means we should be able to find evidence that bone placement was changing a lot in fossils from around the time mammals were diverging from

reptiles

#1. (1 point) Shubin says "We can dress up a fish only so much without paying a price." What he means is that we are essentially highly elaborate fish that live nothing like typical fish do, so that's inevitably going to create some problems. t or f

true

Many key tetrapod traits evolved in the Devonian Period (390-360 MYA). true or false

true

#1. (2 points) Virtually all Vertebrata share four key features. Name any two of these.

vertebrae neural crest cell

Ray bones were lost but digit bones were added in our limbs.

yees

Our skulls changed shape (from round to flat to round again)

yes

Ribs evolved

yes

Spinal bones became thicker and how they attached to each other and to the skull changed.

yes

We evolved several new ear bones

yes

#3. (2 points) If you made a group of just animals that were "true" tetrapods (the name "tetrapod" makes logical sense for them), what kind of "mistake" group would you be creating, phylogenetically?

A polyphyletic group—you'd be forming a group based on superficial appearance ("four working, walking legs") and not based on the real history of evolution.

There are three extant monophyletic groups of mammals: The Monotremes, the Marsupials, and the Eutherians. Which group are humans a part of? Select one: A. Eutherians B. Marsupials C. Monotremes D. None of the above

A. Eutherians

Your inner ear doesn't just help you sense sound! It has two other functions—what are they? A. It detects how are heads are oriented in space (e.g. whether they're tilted at an angle). B. It detects how quickly the head is accelerating in a given direction (like if you were falling). C. It detects whether our head is bleeding. D. It detects whether hairs on our head are being touched. E. It detects whether we are looking left or right.

A. It detects how are heads are oriented in space (e.g. whether they're tilted at an angle). B. It detects how quickly the head is accelerating in a given direction (like if you were falling).

A. Organisms living on land would be exposed to much more direct sunlight than those living in water. B. Temperatures fluctuate more in water than they do on land. C. Any water available on land is generally going to be less salty than water in the oceans. D. There was significantly more food to eat on land than in the water for predatory organisms. E. Aquatic environments were much more 3-dimensional, since at this time land lacked any plant life or flying organisms. F. Carbon dioxide and oxygen are both more abundant in water than they would be on land. G. Gravity is harder to fight in water than on land. H. Animals living on land couldn't breathe in water at this time, but many aquatic organisms could also breathe in air.

A. Organisms living on land would be exposed to much more direct sunlight than those living in water. C. Any water available on land is generally going to be less salty than water in the oceans. E. Aquatic environments were much more 3-dimensional, since at this time land lacked any plant life or flying organisms.

The primates are distinguished from other mammals by features of our hands and feet. Identify the feature listed here that does NOT distinguish primates from other mammals. A. Our limbs are unusually short compared to those of other mammals. B. We have flat nails on our digits rather than pointy "claws." C. We have ridges ("fingerprints") on the flesh of our digits. D. Our limbs have a joint, bone, and muscle structure that makes us really good at grasping objects. E. One of our digits tends to be spaced apart from the others ("thumbs").

A. Our limbs are unusually short compared to those of other mammals.

#6. (2 points) As we'll discuss, class Mammalia has many features that make it distinct from all other vertebrate classes. Of the possible mammalian features listed below, identify the only two that are false.

A. They have a larger diversity of teeth, which are shed and replaced once (or just a couple of times) in a lifetime rather than continuously. B. They have anapsid skulls. C. They are endothermic. D. They have a highly modified version of the amniotic egg (at least in more recent clades). E. They have just one inner ear bone (the stapes). F. They tend to provide significant parental care to offspring. G. They possess red blood cells that lack nuclei to be able to carry more hemoglobin for oxygen carrying. H. They have larger brains relative to body size than other amniotes.

#9. (2 points) The Marsupials also have two distinctive features--what are they?

Adult females possess pouches that young are born into and develop within. , They are almost entirely found in just the Southern and Eastern hemispheres. Marsupials have a pouch (usually on the ventral surface of the mother's body) called a marsupium that the developing young crawl into to suckle and to develop into juveniles. Most marsupials are restricted to Australia--the remaining 100 or so species are native to South and Central America (the Virginia opossum is the only one native to North America).

#2. (1 point) The website you read above mentioned some organisms that are considered tetrapods even though "tetrapod," as a term, doesn't really seem appropriate for them. Provide any ONE example of an organism that is a tetrapod phylogenetically but not literally.

The organisms the website mentions are humans and birds, snakes, and ichthyosaurs, which walk only on two legs, have no legs, or didn't even walk upright, respectively. Other examples that come to mind for me are whales and caecilians, who both evolved from legged creatures but have no legs themselves, and ostriches, which only use two of their limbs for much of anything.

#1. (2 points) Pick any two features listed above and explain why their evolution increased the success of all the mammals that inherited them.

Hair and a fat layer under the skin can conserve water more easily and provide insulation. Diverse teeth allow mammals to eat a wide variety of food, such as plants (flatter teeth) and meat (sharper teeth to tear into flesh), which increase the chance they can eat SOMETHING, which helps them survive.

how sound enters our ear

1. Sound waves are funneled into our ear canal. 2. Waves hit the eardrum, causing it to vibrate. 3. Three bones (the malleus, the incus, and the stapes) rattle as a result. 4. The stapes bobs up and down, plunging the fluid in our inner ear just like a plunger would and making it slosh around like waves in a wave pool. 5. Hairs (NOT nerves! That would be painful) get bent by the sloshing. This bending causes nearby nerve cells to be stimulated, which then send signals to our brain for interpretation.

Both of the functions alluded to in question #4 work in the same way as our perception of sound does. Explain how.

As your head tilts or accelerates, fluid in the other two canals in your snail shell-shaped inner ear slosh around (as do rock-like particles inside them), causing hairs embedded in the fluid to bend. This bending causes nerve cells to send signals to the brain.

While the (accurate) features above gave the primates a number of useful skills, which important skill did these features make our ancestors especially good at?

B. Brachiating

All of the following are key features that the limbs of all limbed animals have except... A. Fourth from the shoulder is five rod-like bones that make up the digits. B. Fifth from the shoulder is a set of five small bones that make up the claws or nails. C. Third from the shoulder is a set of blob-like "wrist" bones that connect the digits to the lower arm bones. D. At the shoulder is one bone that connects the rest of the limb to the body. E. Second from the shoulder is a set of two bones that connect the wrist bones to the first bone of the limb

B. Fifth from the shoulder is a set of five small bones that make up the claws or nails.

#6. (1 point) Which group is the sister taxon of the group we belong to? Select one: A. Monotremes B. Marsupials C. Eutherians D. None of the above

B. Marsupials

answer

B. Their reproductive, digestive, and excretory systems all have separate exits.

answer

B. They have anapsid skulls. E. They have just one inner ear bone (the stapes).

The Monotremes (spiny anteaters and platypuses) have two distinctive features--what are they? A. They have a placenta. B. They have mammary glands but no nipples. C. They are confined entirely to Australia and surrounding islands. D. They lay external eggs. E. They do not have teeth, hair, or nails.

B. They have mammary glands but no nipples. D. They lay external eggs.

Of the options below, select the only one that isn't a difference between lobe fins and ray fins. A. Covering--ray fins tend to be scaly, while lobe fins tend to be covered in skin. B. Usage--lobe fins cannot be used for swimming. C. Ray bones--lobe fins don't tend to have them (or at least as many). D. Muscle content--lobe fins tend to have more. E. Overall shape--ray fins are usually flatter and wider.

B. Usage--lobe fins cannot be used for swimming. Here's a more extensive explanation: Overall shape is one—a ray fin is flatter and wider, whereas a lobe fin is more tube-like. Function is another—while both are useful for paddling and swimming, a lobe fin can also be used to "flop," a movement useful if you are a bottom dweller and need to scoot through mud. Lobe fins also have considerably more muscle than ray fins (to enable "flopping") and are generally covered in skin rather than scales. Many, though not all, bearers of lobe fins lack ray bones as well, as the name would imply. Lastly, some lobe-finned fish and their descendants acquired the first arm bone of later tetrapods, which contributed even more to the tube shape of the lobe fin.

The fact that modern humans are bipedal, like our ancestors, but not as active as those ancestors creates a problem. This problem is... A. Our leg muscles are no longer strong enough for us to climb trees as easily as our ancestors could. B. The nerves in our legs are no longer as sensitive to pain as they were in our ancestors. C. Our feet and ankles cannot perform as many different movements as they could in our ancestors. D. By the time our blood gets to our feet, it's under low pressure. Without us being active, this blood pools instead of being squeezed back up to the heart. E. The veins in our legs have gotten wider over time, which makes them move blood too quickly.

By the time our blood gets to our feet, it's under low pressure. Without us being active, this blood pools instead of being squeezed back up to the heart.

#4. (1 point) Is the amniotic egg in mammals an ancestral trait or a derived trait? What about the placenta? A. Both are ancestral B. Both are derived C. The amniotic egg is ancestral; the placenta is derived D. The amniotic egg is derived; the placenta is ancestral

C. The amniotic egg is ancestral; the placenta is derived Though all mammals have it, the amniotic egg is not unique to mammals--this makes it ancestral. Now, the modifications we have made to it, including fashioning much of it into a placenta (at least in non-monotremes)--those modifications are derived because they are exclusive to (new in) us.

#7. (1 point) Which group is the most basal? A. Eutherians B. None of the above C. Marsupials D. Monotremes

D. Monotremes

#5. (2 points) Primates also have distinctive features related to our heads--which of the following is NOT one of these? A. Our brains are larger for our body size relative to other mammals. B. Our eyes face more directly forward rather than off to the side compared to most other mammals. C. Our eyes are relatively close together. D. Our faces are longer, more rounded, and more angled than those of other mammals. E. Our noses and jaws are shorter than those of most other mammals.

D. Our faces are longer, more rounded, and more angled than those of other mammals.

#2. (1 point) Consider the very different limbs possessed by animals such as bats, whales, kangaroos, and penguins. These limbs differ from one another in all the following ways except... A. The sizes of the limbs. B. The functions of the limbs. C. The shapes of the bones in the limbs. D. The numbers of bones in the limbs. E. The order of the bones in the limbs.

E. The order of the bones in the limbs.

#2. (2 points) Though they are not closely related, birds and mammals share a couple key features. Which of the following is NOT one of those features? A. They both have a 4-chambered heart to more powerfully supply their systems with blood. B. They both have a high metabolic rate and must eat a high-calorie diet to sustain themselves. C. They both have relatively large brains and are relatively good at learning. D. They tend to have a more omnivorous diet than other vertebrate groups. E. They are both poikilothermic.

E. They are both poikilothermic.

When we are intoxicated (or hungover), one common side effect is the "spins," in which we feel like the room is spinning. Explain what causes this sensation.

Ethanol in alcoholic drinks is thinner (less dense) than the fluid in our inner ear. As it diffuses into our blood and then into our ear canals, it mixes with the fluid there and makes it less dense (and thus easier for it to move). Because our ear hairs are now experiencing easier movement than normal, our brains *think* we are moving, tilting, or falling when we actually aren't. When the ethanol diffuses back out again later, it causes the remaining fluid to slosh around again (like you see when you add alcohol to water), leading to a second round of the spins.

#3. (2 points) We believe that fungi made it easier for plants to then colonize land. Explain how.

Fungi would provide plants with nutrients given they are "foragers" relative to plants who are more or less stationary. This gave plants the nutrients by "chilling out" in their roots. They would provide them with water and nutrients in exchange for carbohydrates. Plants would thus have the nutrients they would need to grow.

answer

Here's a more complete explanation: Fungi are heterotrophs, so they could take advantage of the life already present on land as a food source. They are also capable of eating both living and dead organic matter, so they were flexible diet-wise. There were also not large decomposers on land at this time, so there was a large niche available they could fill (no competitors). Their bodies are also very thin, so they did not have to invent (or re-engineer) a gas exchange system to be able to breathe on land. They also live in soils, where they remain moist and relatively shielded from conditions like bright sunlight and weather that they would have needed to contend with aboveground. They do not have to "stand up" (fight gravity) or resist being toppled over by winds like plants or walking animals would need to either. Given that fungi also reproduce primarily asexually, they were likely able to spread very rapidly relative at first. Also, having chitin cell walls helped to make foraging through soils easier and also helped fungi resist drying out.

#9. (1 point) If you were walking through a forest in central Africa 2 million years ago, it is possible you could have encountered as many as five other members of our genus on your walk! Describe how this makes you feel.

It makes me sad that we have lost our evolutionary brothers and sisters. I've always wondered what other species would say if they could "talk" to us, or communicate somehow. While there aren't ginormous differences between say, Homo ergaster and Homo sapiens, I do think there would be a difference in perspective given there were enough differences to recognize interspecies distinctions.

Choose any one of the other three clades of Eutherian mammals and try to identify a feature that most of them share that could serve as evidence that they are a clade that all share a single common ancestor (Note: This is not easy! If it were, these clades would be firmly established by now). The three clades are: The Proboscidea, Sirenia, Tubulidentata, and the Hyracoidea The Rodentia, Lagomorphia, and the Primates The Carnivora, Cetartiodactyla, Perissodactyla, Chiroptera, and the Eulipotyphla

Proboscidea/Sirenia/Tubulidentata/Hyracoidea: They tend to live on or around the African continent (some live in areas of the world that used to be near Africa when the continents were connected). Most are herbivorous. Some possess strange teeth shapes (elephants and aardvarks). The best one I could come up with, though, is that they all have limited reliance on their limbs for obtaining food (they use their mouths, teeth, or trunks instead). Rodentia/Lagomorphia/Primates: Many groups prominently use their incisors (the sharp, blade-like teeth at the front) for eating, often to rip plant material into bite-sized pieces. Very few are carnivorous--most are herbivorous although some (primates, rats, etc.) are omnivores. Many of them have the capability of escaping very quickly--either by hopping or else by climbing trees. Carnivora/Cetartiodactyla/Perissodactyla/Chiroptera/Eulipotyphla: This is not an easy one because this is a very diverse group! Many have heavily modified limbs (hooves, wings, or paddles). Most are highly agile either on land, in the air, or in water (horses, dolphins, cats, bats, etc.). Most are larger-bodied, which may explain why these seem to be the most recent lineage of mammals--mammals had to wait for dinosaurs to die out before they could evolve niches once occupied by large dinosaurs. They are also the most diverse in part because they colonized a huge swath of land (Eurasia and North America).

#8. (1 point) While the hominins were different than other hominids in many ways, one especially important difference was our...

Relatively large brain cases within our skulls.

What strange action was Tiktaalik capable of performing? Why would being able to do this action be useful?

Shubin notes that Tiktaalik had all the structures needed to do "push-ups;" it was able to use chest muscles to push itself off the ground, and its fins were able to bend to facilitate this (see the picture on page 40). This was likely useful because Tiktaalik was then able to lift itself up and over obstacles in shallow water or even "flop" its way from one shallow stream or pond to another entirely out of water. To get even more detailed here, we might note that this may have been adaptive because it allowed Tiktaalik to largely avoid the feeding frenzy taking place in deeper water at this point in time by making it better-adapted to living in extremely shallow water instead.

the classes that make up clade Vertebrata are primarily distinguished from one another by differences in 1) how their skeleton is constructed, 2) what environments they use, and 3) how their reproduction works. #2. (2 points) In one sentence each (explain any 2 of the three), explain why significant evolutionary changes to an organism's skeletal system, preferred habitat, and/or reproduction is likely to lead to evolution of a very new kind of organism (large-scaleevolutionary change).

Skeletal system: Chordates have a notochord, which allows them to have more structural support for their body. This allows them to have a body which fosters more movement, which can out swim prey. Tetrapods had appendages, which allowed them to have better movement on land given they can "flop." Amniotes have a rib cage, which allows them to breath much easier on land given their lungs are anchored to bone. Preferred habitat: Chordates lived primarily in the ocean, and were amongst the first organisms to be predatory, namely a notochord and teeth, which was enabled a recursive cycle of more energy (more predation) --> can afford to expend energy on those innovations, which increased the likelihood of it use. Tetrapods lived in shallow water (Tiktaalik) and on land, which allowed them to evade the waters which were infested with predators. This gave them access to new environments which their physiology had to react to, such as more agile limbs.

Even though we call the lineage we share with amphibians, reptiles, birds, and other mammals the "tetrapods," this is actually maybe not the most accurate name for it. Why not?

Tetrapods are defined as organisms with four feet. This is not necessarily the best name because the clade includes organisms which don't have four feet. Snakes are descendants of reptiles, and thus included in the clade even though they don't have any feet. The same with birds.

There are four groups of living primates. The only taxon listed that is not a primate is the .... The group of primates humans belong to is the

[Sloths]. [Apes].

Compared to other hominoids (great apes), hominids (human-like apes) have two distinct features. One is shrunken canine teeth (likely due to eating less meat). The other is ..... (Hint: Consult the left-hand side of page 747 in your textbook). The change in our skeletal system that had to happen to enable this feature was the ....

[bipedalism] [movement of our foramen magnum toward the center of the skull].

It is inaccurate to call chimpanzees the ancestors of the hominids. This is because

[chimpanzees are extant, just like we are, not a "past" taxon].

The problem that this makes human males prone to is

[hernias].

As such, the term we should apply to chimpanzees relative to us hominids is that they are our

[sister taxon].

Human gonads sit down near the pelvis rather than up near the liver, as they do in sharks. This is because

[they need to be external (and cool) for our reproductive system to work].

#3. (2 points) One interesting feature shared by mammals is our temporal fenestrae--holes in our skulls behind our eyes. Our jaw muscles pass through these "windows" (to "defenestrate" a person is to throw them out a window--True fact!) and anchor to our temples. In class, we considered several hypotheses for why these holes exist. Which of the following was NOT one of them? a. To allow our jaw muscles to be longer and have more spots for anchorage, thus enabling them to contract more powerfully for a stronger bite. b. To save us time/energy/resources during the construction of our skulls, or to make our skulls lighter overall. c. To enable a wider array of facial expressions. d. To provide our facial and jaw muscles more room within which to expand and contract. e. These evolved for no particular reason--they are an evolutionary "accident" (the null hypothesis we must always consider until we can disprove it!)

c. To enable a wider array of facial expressions.

#3. (1 point) One key feature that evolved within the Vertebrata is the amniotic egg. The amniotic egg was so useful primarily because it defended embryos from being easily eaten by predators.

false

During this Period, shallow wetlands and waterways happened to be common along ocean coastlines worldwide because the Earth's climate was warm and wet at that time.....This fact likely enabled the evolution of tetrapods primarily because it allowed them access to warmer waters, which hold more oxygen than cooler waters do. true or false

false

Ray bones evolved to become the digit bones of tetrapods. (Ask Google if you need to) true or false

false

Shubin notes that Darwin's hypothesis logically leads to a pretty surprising but powerful prediction—if all tetrapod limbs have a single origin, then every single part needed to produce our limbs must have evolved for the first time in the common ancestor all tetrapods share. true or false

false

true or false #3. (1 point) The advantage of having three ear bones instead of just one is that it allows us to hear much quieter sounds.

false

true or false The "lateral line" system in fish is analogous to the system in our inner ears--it looks similar and performs a similar function, but it's not built from the same

false

Briefly summarize one other health problem our evolutionary past creates for us--this can either be one from this chapter or one you happen to know of (or find by Googling!).

hiccups: a signal from the brain stem, the "central pattern generator," which arrives at breathing muscles and commands them to breathe in a pattern. This system was derived from fish, except it didn't have to travel as far because, well, they were fish and were much smaller. The signal travels from the brain stem near our neck to reach the diaphragm, and in the process passes by neck muscles which can cause spasms. If the path was more rational, it would go more directly to the diaphragm. but because we come from fish and are basically one biological "duct tape job" throughout our history, we run into this problem.

Fish have no ear bones, reptiles have one, and mammals have three. We think we got our extra two ear bones from our ancestor's....

jaw