Midterm Study Guide RNR 3018

What are key evolutionary innovations of amphibians?

Development of Limbs: Amphibians were the first group of vertebrates to develop limbs, enabling them to leave the water and conquer the land.

Lungs: The sarcopterygian ancestor of amphibians possessed lungs, which provide the ability to breathe air. This trait appeared in bony fishes well before the fish-tetrapod transition.

Metamorphosis: Amphibians typically start out as aquatic larvae with gills known as tadpoles. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs.

Skin Respiration: Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin.

What are key evolutionary innovations of reptiles?

Development of Lungs and Legs: These are the main transitional steps towards reptiles.

Hard-Shelled External Eggs: The development of hard-shelled external eggs replacing the amphibious water-bound eggs is the defining feature of the class Reptilia and is what allowed these amphibians to fully leave water.

Scales or Scutes: Reptiles are defined as animals that have scales or scutes.

Ectothermic Metabolisms: Reptiles possess ectothermic metabolisms.

What are key evolutionary innovations of birds?

Feathers: The evolution of feathers is a key innovation in birds. They provide insulation, enable flight, and are used in display and camouflage.

Beak: The bird beak is a key evolutionary innovation that allowed birds to diversify into a range of ecological niches.

Powered Flight: The ability for powered flight is a major evolutionary innovation in birds.

Respiratory System: Birds have a unique respiratory system that is highly efficient and adapted for flight.

What are key evolutionary innovations of mammals?

Differentiated Teeth: Mammals developed differentiated teeth with precise occlusion, which was crucial for capturing arthropods and crushing their exoskeletons.

Hard Palate: The development of a hard roof of the mouth created a dedicated airway to the lungs, allowing mammal ancestors to eat and breathe at the same time.

Spine Structure: The change from a spine that bends from left to right to one that enables bending up and down ultimately allowed mammals to take in more oxygen as they moved, helping them run faster.

Variety of Tooth Shapes: The variety of tooth shapes — incisors, canines, premolars, and molars — made it possible for mammals to eat many kinds of food.

Milk Production, Warm-Bloodedness, Hair: These are very familiar mammalian characteristics.

Jaw Joint: A joint in the jaw that makes chewing possible was a major evolutionary turning point.

Middle Ear Bones: The transformation of two bones in the reptile jaw, which migrated to the middle ear to become two members of a famous trio, the hammer and anvil.

Skeletal features of amphibians - salamanders

• Short neck (1 vertebra)

• Short ribs along entire trunk

• Little modification for attachment of pelvis to vertebral column

Skeletal features of amphibians - frogs

• Adult frog skeleton modified from the amphibian plan-

  • Much reduced trunk

  • No tail

  • Modified pelvis and hindlimb

Skeletal features of reptiles - Crocodilians

• Primitive trait:

  • no cranial kinesis (or is this secondary?)

• Derived trait:

  • skull openings for muscle attachment

  • teeth in deep bony sockets

• Discreet neck (as in all reptiles)

• Ribs only on the thorax

• Vertebral column not modified for pelvis

Skeletal features of reptiles - turtles

• Primitive traits:

  • no skull openings for jaw muscle attachment

  • no cranial kinesis

• Derived trait:

  • teeth lost

Skeletal features of reptiles - Tuatara, lizards, and snakes

• Derived trait in tuatara

  • skull openings for jaw muscles

• Derived trait in squamates

  • kinetic quadrate

• Additional derived trait in snakes

  • kinetic upper jaw

Snakes have long neck and rib bones unlike amphibians

Cranial kinesis

• refers to the ability of an animal’s skull to move relative to its braincase or other skull components.

  • Unlike humans, whose skulls are relatively rigid, animals with cranial kinesis exhibit flexibility and mobility in their skull structures.

skeletal features of birds

• No teeth - saves weight

• Dinosaur skull

• Modified hand and wrist

• Giant sternum for attachment of flight muscles

• Reduced tail- saves weight

• Dinosaur pelvis

• Bird bones are also hollow to save weight

Skeletal features of mammals

The path from reptiles to mammals- about 250 mybp. This animal is in Therapsida, a clade that includes mammals.

• Reptilian vertebral column and ribs

• Mammalian limb orientation- under the trunk

• Mammalian and reptilian skull characteristics

Mammalian skull characteristics

• Zygomatic arch

• Coronoid process of dentary

• Heterodont dentition

Reptilian skull characteristic

• Jaw articulation at the rear of the jaw on the articular

Evolution of the mammalian jaw

• Appearance of heterodont teeth, some with multiple roots

• Loss of jaw bones (articular moves to the middle ear, only dentary remains)

• Enlargement of coronoid process

General characteristics of amphibians

• Glandular skin produce toxins and mucous (highly variable among species)

• True middle ear with columella (transmits vibrations for hearing- also in reptiles and birds)

• One neck vertebra (no neck vertebrae in fish, multiple in amniotes)

• No dermal bone (a fish trait- fish scales are dermal bone)

• No claws (an amniote trait)

• Eggs cannot resist desiccation

• Highly variable respiration- lungs, gills, skin

General characteristics of reptiles

• Specialized neck vertebrae

• All breathe with lungs

• Keratinized epidermal scales and claws

• Internal fertilization

• Amniote egg (or live birth)

• Strong olfaction

• Some return to marine life (no amphibians are marine)

• Some with temperature dependent sex determination

American Alligator - biology is typical of crocodilians

• Endemic to SE US

• May reach >5 m and live >50 years (!)

• Apex predators

• Nest on mounds in marsh vegetation

• Winter in deep holes dug laterally into banks

• Nest temperature determines sex (warmer -> males)

• Females guard nests

• Communicate vocally

Turtle Biology

• Lay eggs on land

• Usually no parental care

• Unusual life history with high adult survival and very low survival before adulthood

• Bony shell usually covered with keratinized epidermal scutes that are periodically shed (except softshells and leatherback)

• Bony shell plates fused to ribs and vertebrae

• Eat plant and animal material

Lizard Biology

• External ears (lacking in snakes), but rarely communicate vocally

• No LA lizards are aquatic

• Most lizards (all LA lizards) lay eggs, either one at a time (anoles) or clutches of up to 50

• Some lizards (e.g. skinks) show parental care of eggs, others (e.g. anoles) do not

• All LA lizards eat animal prey

Snake Biology

• Highly modified jaws and skull

• Diverged from lizards ~100mya (?)

• Some with vestigial pelvis

• Live bearing or egg laying

• Eat animals only

Bird biology

• 4 chambered heart- separates blood with oxygen from blood without oxygen

• Endothermy (warm-blooded)-

  • allows fast metabolism at any environmental temperature

• Oviparity- lay eggs one at a time

• No urinary bladder

• Muscular gizzard- replaces teeth to grind food

• Short gut

• Large brain

• Excellent vision

These are traits related to:

• high mobility

• high energy requirements

• diurnal activity

Characteristics of mammals

• Uniquely modified skull (jaw, ear, zygomatic arch)

• Heterodont dentition

• Specialized skeleton, especially feet

• Hair (another type of keratinized epidermis)

• Dermal muscles

• Mammary glands (and other skin glands)

• Endothermy

Skin glands unique to mammals

• Mammary glands – provide nourishment for young during postnatal growth (milk stimulated by endocrine system)

• Sweat glands – promotes evaporative cooling and eliminates waste – typically restricted in location

• Sebaceous glands – secretions lubricate hair and skin

Mammal Hair (also called pelage)

• Keratin-based product of epidermis

• Critical for endothermy

• Pelage patterns important for communication or crypsis

• Hair oriented by dermal muscles

Endothermy - Circulatory system

• Complete separation of systemic and pulmonary circulation (4 chambered heart, 2 chambers receive blood and 2 pump blood)

• Many mammals can alter heart rate

  • Hibernation

  • Carnivore lethargy, alarm bradycardia (‘freezing’)

  • Bats – resting and active heart rates differ by 500 beats per minute, and change within 1 second

• Only in endotherms, with high oxygen demand, is it critical always to separate oxygenated blood (coming from the lung) from deoxygenated blood (coming from the body’s capillary beds)

Endothermy - Fat and energy storage

• Not unique to mammals, but important for energy storage, source of heat and water, and insulation

• Temperate mammals typically have localized fat storage

• Boreal and aquatic species store fat subcutaneously over the body

Endothermy - Respiratory system

• Diaphragm – unique to mammals

• Heart and particularly lungs are large relative to body surface- required for endothermy

• Exchange of gases occurs via alveoli, where oxygen enters bloodstream

• Lung surface- humans have 70 m2 of lung surface, about 40 times the surface area of the body

Family Viperidae

• ~250 species worldwide except Australia

• Derived venom-injecting through elongated hollow fangs

• Hemotoxic venom – local tissue damage

• Loreal pits detect heat to 0.2 degrees C

• Vertically elliptical pupils in North American viperids

• Triangular head

Annual cycle for birds

• breeding

• molt

• migration

• molt

• migration

What is a photoperiod? (Regulation of cycle in birds)

Photoperiod refers to the duration of daylight or the length of time that a bird is exposed to natural light during a 24-hour period. It plays a crucial role in regulating various physiological processes in birds, particularly their reproductive cycles.

What about ducks?

• Long distance migrants have relatively fixed timing of migration

• Short distance migrants (like ducks, or robins) may show variation within the migration period due to local conditions- but they still respond to photoperiod

Timing of breeding

• latitudinal variation

• variation among species

• Timing of breeding is an evolved response to match food availability to energy needs of reproduction

• Breeding duration is more narrow at higher latitudes and higher elevations

• Variation among species is greatest in the tropics, least at high latitudes

Migration

predictable seasonal movements (most migrants)

Nomadism

unpredictable aseasonal movements (rare in temperate zone)

Facultative migration

a combination (American Robins, ducks)

Evolution of migration

• Migration route reflects evolutionary history of the species

• Migration can evolve rapidly or disappear

• Timing is changing with global climate change

• The sexes within a species often differ in winter distribution or timing of migration

Hyperphagy

• migratory fattening - innate

  • varies with distance to travel and barriers to cross

  • stopover sites can be critically important

Zugunruhe

• nocturnal restlessness - innate

  • varies with distance to travel

• Speeds- 25-50 km/hour, plus tailwinds

• Range- up to 9 days straight (usually >12 h for Gulf crossing)

Daily timing of migration

• Hawks, swallows, swifts - by day

• Cuckoos, hummingbirds, most songbirds - by night

• Shorebirds and waterfowl - day or night

Why the differences in daily migration?

• Different bird species occupy distinct ecological niches and habitats. Their feeding preferences, nesting requirements, and foraging strategies vary significantly.

• Food availability

• Photoperiod and Circadian Rhythms

• Evolutionary History and Genetics

Homing

the ability of certain animals to return to a specific place when displaced from it, often over great distances. This behavior can occur in any compass direction and at any season. Homing is usually associated with shorter distances and shorter periods of time, often daily, and typically involves a return to a home base after a journey in search of food or mates.

Migration

the regular, repeated mass movement of animals for breeding or avoidance of climatic extremes. It usually involves longer distances and longer periods of time.

Navigation for birds

• Visual landmarks - important for local movements

• Celestial navigation - sun, stars

  • Sun compass - use position of the sun for direction (requires an internal clock)

  • Geomagnetism (magnetic fields)

• Olfaction - mostly used for local movements

Birds have well defined annual cycles

All birds:

• Breeding

  • territory establishment (singing)

  • courtship

  • nest construction

  • egg laying and incubation

  • care of nestlings and fledglings

• Molt

Migratory birds:

• Migration to wintering grounds

• Molt (usually just body feathers)

• Migration to breeding grounds

Dentition and dental formulas

I = incisor

C = canine

P = premolar

M = molar

(U = upper, L = lower)

The numbers are read as how many of either incisors, canines, premolars, or molars. It is read in that order as well.

For example,

U 5 1 3 4 26 ← This is the upper row. It is saying that there are 5 incisors, 1 canine, 3 premolars and 4 molars on each side of the mouth, so there is 26 in maxillary.

L 4 1 3 4 24 ← This is the lower row. It is saying that there are 4 incisors, 1 canine, 3 premolars, and 4 molars, and there is 24 in the mandibular totaling 50 in all Didelphis (opossums)

maxillary

the teeth in the upper jaw

mandibular

the teeth in the lower jaw

In Canidae, the ____ is a special premolar on the maxillary and a molar on the mandible

carnassial

Ungulates are highly specialized for plant diet

• Often lose upper incisors

• Usually lose canines

• Long, flat molars and premolars with irregular surfaces

Armadillo skull- bizarre (As are all Xenarthra skulls- anteaters, sloths)

Armadillo have peg-like teeth. These peg-like, single-rooted teeth are often not classified as incisors etc:

U 0 0 { 8 } 16

L 0 0 { 8 } 16 = 32 Dasypus

Hispid Cotton Rat skull- typical rodent

Highly derived- loss of lots of teeth

• Elongated incisors

• No canines or premolars

• Few broad molars

U 1 0 0 3

L 1 0 0 3