ZOO 2090 lecture post midterm Flashcards
What are the main groups of modern amphibians?
Hint: 3
- Frogs and toads
- Salamanders (and newts)
- Caecilians
What are the types of glands found in amphibian skin and what are their function?
- Mucous glands –> secrete mucus to help with cutaneous respiration
- Granular glands–> secrete poisonous alkaloid compounds for defense
What are some characteristics of the amphibian skin? Explain their significance briefly.
- Skin is thin.
- allows for easier gas exchange (cutaneous respiration) - More terrestrial forms have more keratin (fibrous protein).
- keep it from drying out
- good for defense (less tearing of skin) - Some caecilians and toads have bone elements in the dermis.
- for protection
Often, amphibians go through metamorphosis during development (eggs –> water –> some mixed –> terrestrial).
However, some species have their entire developmental process in the egg, and come out as adults. Why might this be adaptive?
- Breaks link with adult forcing them to always be around water to reproduce
- Eggs can be up in trees for protection, with no ponds nearby
*This is a derived state found in the tropics
What kind of teeth do amphibians have? How are they divided?
- Pedicellate teeth
- Crown (dentified tip) of calcified dentin aries from the pedicel (base), connected by the uncalcified suture
Amphibian teeth are homologous to mammal teeth in the way they are derived. True or False?
False.
Amphibian teeth are not homologous to mammalian teeth (enamel, dentin, etc), they arise differently.
What are some characteristics of the species in the order Anura?
(limbs, tail, tympanum?, fertilization)
- Paired limbs
- Absence of tail (adults)
- Jumpers
- Tympanum usually present to transmit sound to inner ear
- External fertilization, except in Ascaphus–extension of male cloaca
What is are some characteristics of the Anura skull?
- Flattened, open, with big jaws
- Palate is highly reduced
- Allows eyeballs to drop into oral cavity
- Significance: helps force food down throat - Hyomandibula becomes the stapes
- Significance: Sound transmission, works with tympanum in inner ear
What are some key differences in the axial skeleton of anuras that makes it specialized?
- Vertebrae
- fewer
- different kinds
- sacral & pelvic girdle have close affinity
- Urostyle –> fused vertebrae - Atlas –> allows for winder range of motion in head
How many vertebrae does the axial skeleton of an anura have?
9 or less
What is a urostyle and where is it found?
Urostyle –> post sacral vertebrae fused into a rod-shape
-found between the two elongated illium bones of the pelvic girdle
What are some main features of the anura appendicular skeleton?
- Pectoral girdle and radius/ulna are used to absorb the shock of landing
- Tibia/fibula and ankle bones are also fused for sturdiness
- Increase in length of hind limbs –> characteristic of jumpers
In frogs, both the tibia/fibula and the radius/ulna are fused. True or False?
True.
Tibia/fibula –> sturdiness
Radius/Ulna –> shock absorbance
What order are salamanders part of?
Order Caudata
What are some characteristics of salamanders?
limbs, type of feeding, tympanum?, fertilization
- Paired limbs and a long tail
- Suction feeding in water and projectile tongue on land
- No tympanum present
- Fertilization can be external or internal by means of spermatophore transfer
How many pre-sacral vertebrae do salamanders have?
10-60 (have a long back)
What are some characteristics of the salamander skeleton?
- Flattened opened skull with large orbits
- Poor ossification
- Reduction and loss of bones is common
What kind of locomotion do salamanders have?
Dual locomotion.
What order do caecilians belong to?
Gymnophiona.
Why do caecillians have a solid and compact skull?
Hint: they have no limbs or girdles
They have this kind of skull so that they are able to burrow.
How many trunk vertebrae do caecilians have?
60-285, but tail is short/ absent.
What are some characteristics about caecilians?
Habitat, Fertilization, hatchlings
- Restricted to tropical habitats
- Internal fertilization
- Hatchlings are aquatic or terrestrial
How do caecilians compensate for reduced eyes?
They have paired tentacles in the front of their head, which help with chemosensation in dark tunnels.
What is a “Frogamander” and how does it contribute to our evolutionary knowledge about amphibians?
The “Frogamander” is a fossil found of a species that has features excursively from frogs and features exclusively from salamanders, but not both.
It links salamanders and frogs to one phylogenetic line (have affinity with temnospondyii).
What are the hypotheses of amphibian origin? Give a brief description of each.
- Polyphyletic hypothesis
- Eocaecilia with Lepidospondyii
- Anura and Caudata with Temnospondyii - Monophyletic hypothesis
- Affinity of Eocaecilia with Anura and Caudata (Temnospondyii origins)
What is the main reason there are conflicting hypotheses about amphibian evolution?
Relationship determination is often dependent on the characters used in comparison.
(different character = different phylogeny determination)
+Amphibians show complex patterns of morphology during development.
What is Heterochrony and Paedomorphosis, and how does it relate to evolutionary determinations of amphibians?
- Heterochrony–> changes in the timing and rate of developmental events between ancestors and descendants
ex. Mountain form retains larval morphology at reproduction -no metamorphosis into terrestrial form - Paedomorphosis–> larval characteristics of ancestors appear in adults of descendants
Why can paedomorphosis mislead us? (amphibian evolution)
- Two unrelated groups with the same aquatic lifestyle could show loss of bones and reduction in ossification to help with buoyancy
- Might conclude they are closely related - Choice of characters to determine origin and relationships of modern amphibians is hotly debated
- Molecular data suggest modern amphibians arose from common ancestor (not polyphyletic)
What are some characteristics of early amniotes?
(time period, skeleton, jaw/teeth)?
- Evolved in the early/mid-Carboniferous (360-330 mya)
- Were often small (~20 cm long) and had a slight but highly ossified skeleton.–“lizard like”
- The jaws, teeth and neck are modified for improved predation
What is the evolution of amniotes? (Cambrian, Devonian, Carboniferous)?
Cambrian: -first vertebrate, first chordates Devonian: -age of fishes (diversity) -early tetrapods Carboniferous: -first amniotes
What are synapsids and sauropsids?
Synapsids: mammals
Sauropsids: reptiles and birds
What are the types of diapsids?
Lepidosaurs –> lizards and snakes
Archosaurs –> dinosaurs, birds, crocs
What are some characteristics of the amniote cleodic egg?
- a semi-permeable shell which allows gases to pass (O2, CO2), but keeps fluids inside
- Extra-embryonic membranes
What are the functions of the extra-embryonic membranes in amniote eggs?
- Protection and gas transfer:
- Amnion surrounds the embryo with water
- Chorion surrounds the embryo and yolk sac - Respiration and waste storage:
- Allantois fills with waste as yolk proteins are used
What is the significance of the cleidoic egg?
3/4
- Allowed full development of the organism on land and loss of the larval stage
- Living on land led to more efficient respiration (gas exchange)
- Allowed embryo to become larger before hatching compared to amphibians
- More energy invested in each egg
What are some other derived characters of amniotes? Give a brief description of each.
(Hint: skin permeability, lungs, body support)
- Low skin permeability
- greater variation in skin (keratin)
- presence of lipids - Ventilation of lungs aided by ribs (costal)
- allowed for a long neck to draw air through a long tube
- space for elaboration of the nerves that supply the forelimb - Body support
- increased apparent weight (gravity) on land required stronger/stiffer skeletons
What were the benefits of the loss of lumbar ribs in many amniotes?
- No ribs in the way of hindlimb forward movement
- Allowed vertical plane flexion of the column
- easier limb oscillation
- rapid locomotion
What are the new joints in the atlas and axis vertebrae? What is their functional significance?
- Skull-atlas joint
- vertical nodding and horizontal tilting of the head - Atlanto-axial joint
- twisting movement
*This configuration sets up better movement
How do the reduced centra and processes benefit amniotes?
They are able to maintain bony strength of neck while allowing cranial mobility.
Amniotes have to deal with gravity when it comes to the support of their body (which is suspended between its legs). How do they do that?
Amniotes use vertebral column as a “bridge” between support posts (increases support strength):
- Trunk verterbrae–> held in an archer’s bow-like arch by abdominal muscles and sternum
- Cervical vertebrae –> held in a violin bow-like reversed arch by neck ligaments
How are early amniotes (dinosaurs) able to stand upright? Give a brief description of each obstacle they faced/ character their bodies needed.
(2)
- Need to balance heavy body parts against each other
- Hip acts like a fulcrum - Requires a firm vertebral column
- Vertebrae likely tied together by strong ligaments between neural spines
How did amniotes deal with mechanical forces acting on the vertebral column due to axial muscles?
(2)
- Direction and height of vertebral neural spines are modified
- Spines are parallel with forces imposed by axial muscles
- Spine height is proportional to leverage needed to stabilize column - Ligaments join shoulder neural spines to skull and neck vertebrate and help support a heavy head e.g., bison
How did limb posture change in mammals and dinosaurs? How did these changes benefit them?
(2)
- Limbs are situated under the body
- Increased efficiency of limb swing during rapid locomotion - Digit and limb position also allowed inward rotation
- Forward thrust was better aligned with the direction of movement
Amniotes vary in the number of fenestrae they have behind the orbit. What could have caused this?
- Early splits in amniote evolution (mid-Carboniferous)
- Evolution to reduce skull weight and provide attachment edges for jaw muscles
What are the different categories of temporal fenestrae?
3
1. Anapsid--> no temporal fenestrae (earliest amniotes and turtles) 2. Synapsid--> one lower temporal fenestra (extinct synapsids and mammals) 3. Diapsid--> two temporal fenestrae (reptiles, birds, dinsosaurs)
What are the dorsal carapace and central plastron of turtles made up of?
Dorsal carapace and ventral plastron made up of fused bony elements covered by keratin scutes, attached on the sides.
What are the two major components of the turtle body plan?
- Shell: vertebrae, ribs, osteoderms, scutes (keratin)
2. Position of scapula: inside of rib cage
What are the two hypotheses for turtle body plan evolution?
- Gradual transformation
- evidence from fossil records - Rapid evolution via changes in developmental regulation
-positioning of scapula & ribs
start to see intermediate forms of body plan
What are the 3 main types of Lepidosaurs?
- Tuatara
- Lizards
- Snakes
Snakes evolved before lizards. True or False?
False.
What are some skull adaptation in lizards and snakes?
4
- Loss of temporal bar(s) around fenestrae
- Lizards: Lower absent
- Snakes: Upper and lower absent - Opening up of skull
- Allows bigger food to be swallowed - Transcranial joint(s) across the top of the skull
- Snakes: Front of orbit (single)
- Lizards: Rear of orbit and back of skull (double) - Ability of quadrate bone to rotate about dorsal connection with braincase
Describe the two steps of cranial kinesis in lizards. What is the function significance?
- Opening –snout tips up
- Closing –snout tips down
•Equal perpendicular force of both jaws on food item
-keep food/ prey in mouth
Describe cranial kinesis in snakes.
- Lower jaw is loosely hinged
- Two sides of mandible can come apart (only connected by muscle and skin)
- Skull and upper jaws are moveable
- Moveable quadrate bone links jaw and skull
What are the 4 types of crawling locomotion? Give a brief description of each.
- Lateral undulation
- Moving waves push sideways against contact points
- Generates a reaction force with a forward component (lateral components cancel out) - Concertina movement
- Energy costly
- used in narrow spaces (tunnels)
- involves stationary coils wedging the animal into place while free body parts move forward - Sidewinding (colubroidsnakes)
- used over sandy soil
- body contacts 2 or 3 straight tracks at a time with different segments in succession as they are released from previous track
- only segments between tracks are moving - Rectilinear movement
- slowest, but discreet
- used by many snakes
- Requires specialized muscles progressively lifting and bringing forward ventral scutesto peg them to the ground
- Body not in contact with ground is moved forward within very distensible skin
What are some physical characteristics of crocodilians?
- nostrils, eyes and ears on the head
- Eyelid is transparent
- Bony flaps in throat
Crocodilians are able to regulate body temperature by lying with its mouth open. True or False?
True.
How many chambers does the heart of a crocodilian have?
4.
What is the most important skill about Pterosaurs? How did they gain this ability?
They were the first vertebrate group to evolve powered flight.
- Used membranous wings supported by elongated forelimb
- Early forms had long tails and elongated forelimb
- Later forms lost tail and teeth; had projection at back of head
What are the two major groups of dinosaurs? How are they distinguished?
Two major groups: Saurischia and Ornithischia
Distinguished by the structure of the pelvic girdle
- Saurischia: girdle bones radiate outward from the centre
- Ornithischia: ischium and part of pubis are parallel and project backwards
What kind of diet did Saurischians have? Give some examples from the 3 groups.
Herbivourous and carnivorous
Examples: 5.Apatosaurus, Diplodocus)
- bipedal (e.g., Tyrannosaurus, Velociraptor)
- Archaeopteryx, birds likely evolved from this group
What was the diet of Ornithiscians? Give some examples from the 4 groups.
All herbivorous
Examples:
- Ankylosaurs and stegosaurs
- Duck-bills
- Head-buters
- Triceratops
What were some skeletal adaptations that giant dinosaurs had to have?
(3)
- Shortened pillar-like limbs (weight support)
- Reduction/shortening of wrist/fingers and ankle/toes
- Elongated necks -more, longer, but lighter cervical vertebrae
Who was the biggest Archosaur competitor of the early dinosaurs?
Archosaur competitor of early dinosaurs -Crurotarsans
-Died out by chance, despite their larger range of phenotypes and similar evolutionary rates to dinosaurs
Why did dinosaurs prevail during their time?
Dinosaurs prevailed because of one or several key adaptations which allowed them to take advantage of empty niches.
When did the K-T mass extinction occur?
The end of the Cretaceous period.
Around when did Aves first originate?
the Jurassic (~170 mya) (They likely evolved from dinosaurs)
What is the advantage of wings/flying?
Flyers can gain access to flying prey, escape from non-flying predators, and have unrivaled migratory abilities.
Do all aves use wings to fly?
No. Locomotion is varied -wings exclusively to swim (e.g., penguins) or not used (e.g., ostriches)
What are the hypotheses about the origin of flight?
Older ideas:
- Arboreal hypothesis: gliding from tree to tree
- Cursorial hypothesis: running start and lifted off the ground for insect foraging
New ideas:
1. Use wings to scale inclined objects and trees
What are the skeletal adaptations in birds?
Skull, Neck, Backbone, Pelvic girdle
Skull:
-Reduced number of bones and thinner bones; no teeth (beak). Light weight
Neck:
- Exceptional flexibility -compensate for the loss of fore limbs.
- Heterocoelous cervical vertebrae
Backbone:
-Very rigid to minimize the number of muscles needed to maintain the streamlined body during flight, thereby reducing the energy consumption
Pelvic girdle fused with synsacrum:
-Bipedal; no symphysis (pelvic bones not fused) so large outlet for massive eggs
What are the different types of vertebral centra in Archosaurs? Where are they found?
1. Acoelous (most mammals) 2. Amphicoelous (fishes, some salamanders, some lizards) 3. Procoelous (anurans, most living reptiles) 4. Opisthocoelous (most living salamanders) 5. Heterocoelous (birds)
What is the synsacrum of birds make up of?
- Thoracic vertebrae
- Lumbar vertebrae
- Sacral vertebrae
- Caudal vertebra
What is significant about the sternum in birds?
It is ossified and well pronounced keel (carina) to provide attachment for flight muscles.
What is the main similarity of the integument of sauropsids? (reptiles and birds)
They both have epidermal derivatives.
Do reptiles have glands in their integument? If yes, what are they used for?
Relatively few glands –dry integument
-Glands produce poisons, pheromones as signals for sex, identity, navigation
Do birds have glands in their integument? If yes, what are they used for?
Single large gland -uropygial gland produces oily secretion for transfer to feathers
-Waterproofing, well developed in aquatic birds
What are a few characteristics of reptile epidermal derivatives?
Have well developed epidermal keratinized (horny) scales (scute)
- continuous folds of epidermis
- shed regularly in lizards and snakes
- protection from desiccation
- Used for locomotion (snakes)
What are a few characteristics of bird epidermal derivatives?
- Scales in places without feathers
- Claws at the ends of digits
- Beaks often include tooth like protuberances (not true dermal teeth)
- Feathers for thermoregulation, locomotion and attract mates
Mammals evolved many years after the first reptiles. True or False?
False. Mammals originally evolved before reptiles, but weren’t too diverse/ abundant until afterwards.
What kind of synapsids are Pelycosaurs?
Pelycosaurs are basal synapsids. (basal amniotes)
What reptiles arose in Carboniferous before lineage and eventually led to modern reptiles?
Pelycosaurs.
How many temporal openings do Pelycosaurs have? How does this differ from their ancestral reptiles lineage?
Pelycosaurs have a single temporal opening. Their reptile lineage had two.
What are some physical characteristics about pelycosaurs?
- Still had a sprawling posture
- Some had a broad “sail” along the back made of extended neural spines and skin.
*They used sails for thermoregulation, and possibly mating, but it’s difficult to know for sure.
Cynodonts are currently existing mammal-like reptiles. True or False?
False. They are extinct mammal-like reptiles.
What are some changes in the cynodonts jaw that allowed chewing in multiple directions?
- Adductor differentiates into masseter and temporalis muscles
- Muscles expand and invade larger areas of the skull roof bones
Compare the occipital condyles and hindlimbs of pelycosaurs and cynodonts.
Pelycosaurs:
- One occipital condyle (like reptiles)
- Hindlimb is still far out from body
Cynodonts:
- Mammal-like double condyles (greater neck mobility)
- Hindlimb is modified to a semi-erect position closer to the body (greater stride length)
What do cynodonts use nasal turbinates for?
They use nasal turbinates for regulation of heat and water exchange.
What is the significance of a secondary palate evolving in cynodonts?
- Division of food and air passages by secondary palate
* Means you can eat and breathe at the same time.
Give a few characteristics of the first mammals. (Time period, diet, thermoregulation, parental type)
- Arose in late Triassic (~210 mya) from cynodont ancestor (beginning of continental drift)
- Small insectivores displaying agile, rapid movements -Endothermy with enlarged brain for better hearing and smell
- Feed young milk from mammary glands
- Extended parental care of young
Early mammals had a large brain relative to their body size. True or False?
True.
What kind of complex integumentary glands did mammals have? Give a brief description/ function of each.
- Sebaceous
- alveolar glands
- oily/waxy secretion often with hair
- waterproof hair and protect skin from drying - Sweat
- tubular
- osecrete water, salts, urea
- some important for thermoregulation
What kind of specalized glands arose from sebaceous/ sweat glands in mammals?
- Mammary glands:
- Develop along the milk line during embryonic development
- Number and location of nipples varies across species
- Provide nutrition for young offspring - Scent glands:
- Defense, sexual recognition
Claws, hoofs, nails, horns, antlers, and hair in mammals are derivatives of the _______.
Claws, hoofs, nails, horns, antlers, and hair in mammals are derivatives of the INTEGUMENT.
Hyomandibula bone (_______ (Hint: number) branchial arch) supports jaws in fishes.
Hyomandibula bone (SECOND branchial arch) supports jaws in fishes.
Hyomandibula becomes the ________ in amphibians –sound transmission in middle ear
Hyomandibula becomes the STAPES in amphibians –sound transmission in middle ear
Jaw articulation between _________ (upper) and _______ (lower) in bony fishes, amphibians, reptiles and birds.
Jaw articulation between QUADRATE (upper) and ARTICULAR (lower) in bony fishes, amphibians, reptiles and birds.
In mammals, the lower jaw is now made up of a single bone called the ______.
In mammals, the lower jaw is now made up of a single bone called the DENTARY.
Jaw joint in mammals is between the dentary and the _______.
Jaw joint in mammals is between the dentary and the SQUAMOSAL.
In mammals, what are the quadrate and articular now a part of?
They are now a part of the middle ear.
What bones make up the middle ear of a mammal?
3
- Stapes: was hyomandibula in fish
- Incus: was quadrate
- Malleus: was articular
Mammals have teeth with specialized functions. What are these teeth called?
- incisors,
- canines,
- premolars
- molars
Mammal dentition can tell us a lot about a mammals diet. True or False?
True.
Mammals arose in the late Triassic (~210 mya). What are the traditional and modern views about their evolution in regards to the K-T extinction?
- Traditional view:
- Early mammals were small shrew-like animals
- A few lineages existed in specialized ecological niches amongst the dominant dinosaurs
- Evolved into diverse lineages after extinction of the dinosaurs (niches became available) - More recent ideas:
- Mammals started to diverge beforethe K-T extinction!
What is the association between the loss of dinosaurs and the diversification of mammals?
Increased diversification of mammals after loss of dinosaurs.
Did true mammals remain as small insectivores amongst the dominant dinosaurs without diversification into other lineages?
No! Many diversification events but often unsuccessful.
What are the three groups of living mammals? Give a brief description of each.
- Monotremes
- Mammalian characteristics of hair, endothermy and suckling of young
- Lack nipples and external ears
- Embryos develop in leathery eggs (primitive amniote character)
- Limited diversity - Metatherians (marsupials):
- Found predominantly in Oceania (~200 species)
- Give birth to tiny young who suckle until they grow much larger, often in a specialized pouch of the mother
- ~100 species in the Americas, only one in North America (Virginia opossum) - Eutherians (plancentals):
- Most diverse and widespread group of mammals
- Radiated extensively after the KT extinction but limited diversification during last 50 my!
- Prolonged gestation of embryo in uterus with placenta
What does the development of embryos in leathery eggs of monotremes suggest?
Suggests earlier mammals also laid eggs.
The duck-billed platypus and four species of echidnas (spiny anteaters) in Australia/New Guinea are part of what group of mammals?
Monotremes.
What caused the strange distribution of Placentals?
-Distributions correlate with isolation of continents as they drifted away from the earlier supercontinent (Pangea)
Where did placentals and marsupials likely arise before the continental drift?
Placentals: likely arose in Asia –> migrated to africa –> into north and south america
Marsupials: likely arose in what would become north america
How did marsupial migration cause its diversity?
Mostly found in south america and australia.
- Got into south america due to physical connection of continents
- South american group is genetically different from australian group because they went on their own evolutionary paths after separation (convergent evolution)