BIOL 2251 final

amniotes

reptiles, birds, mammals - their embryos are protected by external membranes

Mezozoic Era

Age of reptiles

Triassic Period

Part of the Mesozoic Era, the period when dinosaurs first appeared. (248-213 million years ago)

Cretaceous Period

A period when more carnivorous, ferocious Dinosaurs evolved

temporal fenestrae

openings in the temporal region of the skull for jaw muscles

Anapsid

primitive reptile having no opening in the temporal region of the skull

Diapsids

two fenestra in skill - found in birds, reptiles and dinosaurs

Synapsids

A single pair of temporal openings low on the cheeks. Found in mammals and their extinct relatives, therapsids and pelycosaurs.

amniotic egg

amniotic eggs have four extraembryonic membranes:
- amnion
- allantois
- chorion
- yolk

negative pressure breathing

A breathing system in which air is pulled into the lungs when the lung volume is expanded and lower pressure is created.

amnion

Amnion - encloses the embryo in fluid
• Provides cushioning and an aqueous
medium for growth

allantois

Allantois - stores metabolic wastes

chorion

Chorion - surrounds entire contents of egg
beneath shell
• Highly vascularized
• Respiratory surface, along with allantois

yolk

Yolk - nutrient storage
• Forms a yolk-sac placenta in some
species

internal fertilization

Process in which eggs are fertilized inside the female's body

keratin

hard protein material found in the epidermis, hair, and nails

beta keratin

The stiff material in reptiles that makes scales durable and resistant to water loss

How many species of reptiles have been described?

approx. 9,500

What era did the reptiles rapidly diversified?

the triassic period of the mesozoic era.

How do the skin and respiratory system of amniotes differ from early tetrapods?

- They had thicker and more waterproof skin.
- They had rib ventilation of the lungs and used negative pressure breathing.

What are the derived characters of amniotes? Describe each one.

- Amniotic egg
- Thicker and more waterproof skin
- Rib ventilation of the lungs
- Stronger jaws

What derived character is considered the key for the success of tetrapods on land? Why?

amniotic egg

Amniotes are divided into three groups. What are the groups and how do their skulls differ?
What is the significance of the holes in the temporal region of the skull?

The three groups are divided based on the pattern of holes in the temporal region of the skull: Anapsid, diapsid, synapsid.
- Anapsid: Have a skull with no temporal opening behind the orbits.
- Synapsid: A single pair of temporal openings low on the cheeks.
- Diapsid: Skull has two pairs of temporal openings; One pair below the cheeks and another above.

Openings in living species are associated with large muscles that elevate the lower jaw and close it. they indicate a shift from aquatic feeding to terrestrial feeding.

What is the composition of a reptile scale? Is it homologous to fish scales? Why or why not?

Reptile scales are not homologous to fish scales because:
- Reptile scales are made of keratin, while fish scales are made of dentine.
- Reptile scales are formed from the epidermis, while fish scales are formed from the dermis.

feathers

The feather is single unique feature that distinguishes birds from other living animals
- Feathers are very lightweight
- Feathers have remarkable toughness and tensile strength
- Most feathers are vaned feathers that cover and streamline a bird's body; Called contour feathers

keratinized beaks

The outside of a bird's beak is covered in a thin, shiny sheath of keratin

wings

- all birds have forelimbs modified as wings.
- Wings are present for lift and propulsion.

pneumatic bones

Modern birds have light, delicate bones laced with air cavities
• Called pneumatized bones, it is light but strong

theropod dinosaurs

Thomas Henry Huxley classified birds with theropod dinosaurs
• Group of dinosaurs with a long, mobile, S-shaped neck like birds
• Dromeosaurs, a group of theropods that includes Velociraptor, share additional derived characters with birds:
- Furcula
- Lunate wrist bones

Archaeopteryx

The fossil of Archaeopteryx demonstrates
the phylogenetic relatedness of birds and theropod dinosaurs

Neornithes

Living birds (Neornithes) are
divided into two groups:
- paleognathae
- neognathae

Paleognathae

Paleognathae are large, flightless,
ostrichlike birds and kiwis
• Called ratite birds
• Have a flat sternum with poorly developed pectoral muscles

flat sternum

Ratite flightless birds have this type of bone.

ratites

ostrich, kiwi, emu; flightless birds

keeled sternum

helps to increase power, large flight muscles attach here.
- one of the main things that differentiates flying birds from flightless birds.

contour feathers

vaned feathers that cover and streamline a bird's body are called contour feathers

quill shaft

calamus. the hollow, tubular, and hard basal part of a bird's feather that attaches it to the skin follicle

vane

the flattened, weblike surface on either side of a bird feather's central shaft

barbules

microscopic, hair-like filaments that branch off the barbs of a feather

preening

in birds, the act of grooming and maintaining their feathers

downy feathers

The primary function of downy feathers on a bird is to form a layer of insulation to keep a bird warm.

air sacs

- Air sacs are specialised structures found in birds used for respiration.
- connected to the bird's trachea, or windpipe, and are used to store and exchange gases during respiration.

parabronchi

Finest branches of the bronchi do not terminate in alveoli but are tube-like parabronchi through which air flows continuously.

crop

a muscular pouch located on the front of a bird's neck. It is an enlargement of the esophagus and serves as a storage place for food.

gizzard

thick-walled muscular pouch below the crop in many birds for grinding food.

Proventriculus

- The first of the two chambers in the stomach of a bird.
- The proventriculus secretes an acid used for breaking down food.

Cloaca

- It acts as a waste elimination chamber for both urine and feces.
- Mating involves bringing cloacal surfaces in contact.

Overexploitation

Practice of harvesting or hunting to such a degree that remaining individuals may not be able to replenish the population.

How many species of birds have been described?

over 10,500

What are the structures shared by all birds?

- All birds have forelimbs modified as wings
- All birds have hindlimbs adapted for walking, swimming or perching
- All birds have beaks
- All birds lay eggs

What are the adaptations that facilitate flight?

A birds entire anatomy is designed around flight
- Wings are present for lift and propulsion
- Respiratory system must meet intense metabolic demands of flight
- Bones provide a light but rigid airframe
- Digestion and circulation must meet high-energy demands of flight
- Nervous system must have superb sensory systems for headfirst, high-velocity flight

Explain the significance of the discovery of Archaeopteryx. What are the bird characteristics and the reptilian characteristics?

significance is that it demonstrated the phylogenetic relatedness of birds and theropod dinosaurs.

What is the beak of a bird made of? What are the hypotheses for the loss of teeth in modern birds?

- Beaks are mostly made of bone and covered in a thin layer of keratin.
- One of the major reasons for the loss of teeth in birds may be incubation period. Basically, they argue that birds are under evolutionary pressure to speed up embryonic development so vulnerable incubation time periods are shortened.

Bard

part of the birds feather where the quill shaft and vane connect too

Describe the breathing process in birds and explain why it is so efficient.

Birds have a directional respiratory system with looped airways that allow air to flow in one direction, while blood flows in another. This efficient mechanism maximizes gas exchange and enhances oxygen uptake, critical for sustaining the high metabolic rates required for flight.

What structures make up the digestive system of birds, and what are their functions?

- Beak: Grasping and manipulating food.
- Esophagus: Transports food to the crop.
- Crop: Stores food temporarily.
- Proventriculus: Secretes gastric juices and enzymes.
- Gizzard: Grinds food mechanically.
- Small Intestine: Digests and absorbs nutrients.
- Pancreas and Liver: Produce enzymes and bile for digestion.
- Large Intestine: Absorbs water and some nutrients.
- Cloaca: Expels waste from the body.

What are the main threats to bird populations, and what conservation actions have proven successful for bird protection?

- Causes of bird extinction include habitat destruction and hunting.
- Wetlands conservation efforts and conservation funding have paid off with healthy waterfowl populations.
- Hawks and falcons benefited greatly from focused conservation policy, such as Endangered Species legislation and the banning of harmful pesticides such as DDT.

pelycosaurs

An extinct group of early synapsids that lived during the Permian period, and included some of the first large terrestrial predators.

Dimetrodon

A well-known genus of pelycosaur that lived during the early Permian period, fossils can be found in Oklahoma.

Therapsids

an extinct group of reptiles from which mammals evolved

Cynodonts

The only therapsid group that survived to enter the Mesozoic

heterodont teeth

specialized teeth to facilitate breaking down food to speed up digestion

turbinate bones

reduced heat and water loss from expired air

secondary palate

enabled breathing while eating

Diaphragm

sheet of muscle that separates the chest cavity from the abdominal cavity in mammals, plays a key role in breathing. comes from loss of lumbar ribs

epidermis

outermost layer of skin

dermis

layer beneath the epidermis containing blood vessels , nerves, hair follicles etc

hair

characteristic of mammals , grow from hair follice which starts in the dermis.

under hair (dense)

- provides insulation by trapping a layer of air.
- almost impossible to wet in aquatic mammals

guard hair (coarse)

protect against wear and provide coloration

sweat glands

tubular coiled glands that are involved in thermoregulation

scent glands

Vary in location and function and can be used for communication

sebaceous glands

produce a lipid mixture that conditions the hair

mammary glands

modified sweat and sebaceous glands, occur in all females but are rudimentary in males

diphyodont

condition of having two sets of teeth during a lifetime, common in most mammals

monotremes

Egg laying mammals, include platypus and echidnas, found in Australia and New Zealand

echnidas

A type of monotreme also known as spiny anteaters, characterized by their spiny coat and long, sticky tongue used for catching ants and termites.

platypus

A semi-aquatic monotreme with a unique combination of features, including a duck-like bill, webbed feet, and the ability to detect electric fields.

Marsupial

A group of mammals that give birth to relatively undeveloped young, which then complete their development in a pouch (called a marsupium) on the mother's belly. koala. kangaroo

Marsupium

an external abdominal pouch in most marsupials where newborn offspring are suckled

Placental animals

Mammal whose young complete their embryonic development within the uterus, joined to the mother by the placenta. humans, whales.

Compared with marsupials, eutherians have a more

complex placenta

eutherians have a more complex placenta. What are the extraembryonic membranes that form the placenta in eutherians?

chorion, allantois. Chorioallantoic

placenta in marsupials

choriovitelline

What are some key characteristics of Dimetrodon discussed in class? Is it considered a reptile? Why or why not?

no. a mammalian like reptile. synapsid.

Are reptiles considered the ancestors of mammals? Why or why not?

Mammals did not evolve from modern reptiles; instead, mammals and reptiles share a common, ancient ancestor (an amniote). Mammals diverged into the Synapsida lineage.

List and describe the key adaptations found in cynodonts.

Evolved features supporting a high metabolic rate
- Specialized jaw musculature permitted a stronger bite
- Heterodont teeth improved food processing for variety of foods
- Turbinate bones in nasal cavity aided body heat retention
- Secondary palate enabled breathing while eating
- Loss of lumbar ribs correlated with evolution of diaphragm

List and describe the parts of the hair. List modifications of the hair for different uses.

Mammals have two kinds of hair forming their pelage (furcoat)
- Dense and soft under hair serves as insulation by trapping a layer of air
- Coarse, longer guard hairs protect against wear and provide coloration

What is the function of under hairs and guard hairs?

- In aquatic mammals, Under hair is so dense it is almost impossible to wet
- Guard hairs adhere to each other when wet, forming protective layer over under hair.

Describe the dental modifications that occurred from early synapsids to mammals, and explain the significance of these changes

uniform, rapidly replaced teeth to specialized, occluding dentition. Unlike most other vertebrates, mammals do not continually replace teeth. They have have the diphyodont pattern.

What is the function of each chamber that forms a ruminant stomach?

Reticulum - particle seperation occurs

Rumen - digestion aided by microbes and food is formed into small balls of cud

Abomasum - digestive acid break down food

Omasum - water absorption