essay questions

What evidence supports evolutionary relationship between birds and theropods?

Bipedal posture, hinge, like ankles, hollow bones, and S shaped neck

Fercula (wishbone) and three fingered hands appeared in primitive theropods

What is the Significance of archaeopteryx?

Showed that birds were related to a group of reptiles. It had a long lizard like tail, bearing a pair of feathers on each joint and with its wings it had two free claws.

Serves as a missing link, but multiple feather diners and birds live at the same time

feathers look like modern flight feathers

How did feathers evolve before powered Flight?

Early feathers called Proto feathers were hair like filaments that are considered to be the earliest stage of feather evolution. Elaboration of these structures into the more complex branching and vein feathers of modern birds occurred in the micro raptor, theropod. They were likely used for display and Thermo regulation as well as egg brooding

Compare and contrast birds with their dinosaur ancestors

Similarities- Feathers, wishbones, egg, brooding, by pedal posture, hinge, like ankle, hollow bones, S shaped neck, aversion of the pubic for forward movement, three fingered hands, ability to fold the forearm against the body, also elongated arms which became wings

Differences - keeled breastbone, highly reduced tail, no teeth

Explain the concept of exaptation And provide examples from bird evolution

Exaptation Is an evolutionary trait that originally evolved to serve one purpose, but was co-opted to perform a completely different function.

Feathers were used for insulation camouflage and display, but were co-opted and structurally modified to create aerodynamic surfaces. Through natural selection it was molded specifically for flight after species success with the trait

Describe major evolutionary changes that facilitated the development of flight

Pneumatic bones as they are light, but strong, bone fusion allows for sturdy bones that can handle mechanical stress, keeled sternum which is a enlarged blade like and serves as an anchor point for pectoral, muscles, feathers their asymmetrical and create air foils which allows for lift and thrust, pygostyle short tail that allows for a fan of feathers for steering and stabilization, air sack system, which maximizes oxygen every breath, for chambered heart that allows for oxygen rich blood to be delivered to demanding flight muscles, and lastly, the loss of teeth bladder, and an ovary to reduce weight. They also started to create uric acid instead of fluid and urine to reduce the amount of water weight.

What is the impact of the crustaceous Paleo gene extinction event on bird evolution?

Avian radiation – beak birds that eat nuts seed detritus outlasted their meat and insect eating counterparts. The reduced competition and predation allowed them to spread rapidly.

How did fossil evidence contribute to our understanding of avian evolution?

Dinosaurs were similar features have been discovered as well as dinosaurs with feathers at each stage of development. This should changes overtime in common age ancestry.

what is the significance of the furcula and pygostyle?

The pygosyle Provided a point where multiple feathers could attach and fan out allow, allowing for stabilization and steering.

Fercula Act as a strut to brace the shoulders. It prevents shoulders from collapsing during downstroke and provides a spring like action in the upstroke, aiding in energy efficiency, and muscle attachment for the pectoral.

Skeletal anatomy of birds and theropod similarities

Wishbone, hollow bones shaped neck, reverse pubes, three fingered hands and ability to fold forearms.

What are the major skeletal adaptions that facilitate flight?

Pneumatic bones, bone fusion, keeled sternum, pygostyle

The function of pneumatic bones in birds

Reduce overall body weight, boost, oxygen circulation by acting as an extension of air sacks, and assist with body temp regulation

Avian vs mammal respiration

Mammals draw air in through the trachea into the lungs where the muscular diaphragm facilitate inhale and exhale. The cellular respiration occurs within the sacs in the lungs were oxygen and is inhaled, and carbon dioxide is exhaled in a by directional system.

Birds as a one-way system that utilizes air sacks for storage and movement without the use of a diaphragm

Discuss the structure and function of the avian air sac system

Birds have nine air sacks that serve as Bellows to store air that allow a continuous stream of air to pass through the lungs in a one-way flow. They are connected to their pneumatic bones and remove excess heat as the bird breathes. It can be described in four cycles:

1 inhale- Air moves through the trachea, bronchus, long, posterior thoracic and abdomen sac.

2. Exhale - The abdomen contracts, forces air from the abdomen sack, through the lungs, into the bronchi, and eventually air capillaries were cellular respiration occurs

3. 2nd inhale - Air is driven from Longs and through the cervical anterior air sac

4. 2nd exhale - air is driven from lungs, moves through the trachea and nostrils

Explain how the pectoralis and supracoracoideus muscles function during flight

The pectoralis is contracted, where it pulls down on the humorous bone in each wing, creating thrust and lift

Immediately after the supracoracoideus, which is connected by a tendon to the top of the humorus, works like a pulley to lift the wing when the muscle contracts

Describe the digestive track of birds and the function of each major organ

Esophagus food travels through to the crop which is able to store food as a pouch, then moves to the proventriculus or “true stomach” that secretes gastric juices before moving into the gizzard, a muscular organ that serves as the birds “teeth” to grind down food. It is then digested through the small and large intestine and waste is excreted through the cloaca

What is the significance of the four chambered heart?

The four chambered heart separates oxygenated blood from the deoxygenated blood Allowing for the maximum amount of oxygen to be delivered to the flight muscles. This fuels metabolic rates sustained powered flight and maintained warm blooded lifestyle

Compare the avian and reptilian skeletal system

very different - hollow bones vs dense bones, birds have fewer bones due to fusion, reptiles have teeth and jaws and separate uninfused bones, no keel, etc.

Describe adaptations of bird anatomy that reduce body weight

No teeth, loss of organs - no bladder, switched to uric acid to reduce fluids carried, only one ovary in female

Discuss the role of the syrinx In bird communication

It enables the birds to Create complex songs, territory, calls, and mimics by vibrating soft tissue and membranes as air flows through

Describe the evolutionary origin of feathers and the evidence supporting their dinosaur ancestry

First feathers were flexible, hollow tubes

Second Evolved into clusters of hollow tubes (barbs) Without a central shaft

Third bars developed, and the basis of the bars used together into a central shaft called a rachis

Fourth, there was a development of small hooks on the barbules (hooklets) That interlock like Velcro to create a smooth surface on either side of the fully developed rachis

Lastly, feathers evolved a Symmetric beings that support flight by creating a strong leading wing edge. This feather was on Archaeopteryx.

Many dinosaur fossils from China and Canada have been discovered with feather traces. Many theropod dinosaurs had stage one and two feathers, but some like Ornithomimus had large feathers, likely used for a display..

Discuss the hypothesis that feathers evolved initially for insulation

Early feathers were not capable for supporting flight because they were more simple Hair like filaments. It is thought that many early theropods Were warm blooded, so this likely helped retain heat

Compare the structure and function of down and flight feathers

Down feathers have loose barbs and lack a rachis. They are flexible and this allows them to remain under flight feathers to create air pockets for warmth and buoyancy in water fowl. Flight feathers are stiff with a rachis, vanes, barbs, barbules, and hooklets that create wind resistance from their zipper like makeup used for flight

Explain how feather structure contributes to flight performance

Looking at the vanes microscopically, Coming off of the rachis are barbs with barbules and Hooklets. The Hook act like a zipper, which allows for the barbules to interlock creating a continuous windproof structure that prevents air from passing through.

Asymmetrical veins-Flight feathers have a narrow, stiff leading edge and broader flexible trailing edge. This acts as an airfoil to improve flow and reduce turbulence

Tail feathers are arranged in a fan shape that helps steer and stabilize

coverts, by overlapping, transition of air over wing, which reduces drag

Describe the anatomy of a typical feather

Calamus - A hollow tube that turns into a rachis in most feather types is A solid flexible, central stem that runs the length of the feather providing structural support.

Spanning from either side of the rachis Are the veins. The vein gives the feather. It’s flat sale like shape creating surface area needed for flight and insulation.

The veins are composed of hundreds of parallel, microscopic branches called barbs. They branch off the rachis in a V form. Barbules branch of the barbs and in some cases (pennaceous feathers) have booklets that branch of of the barbules that allow barbules to interlock together to make a windproof structure.

Explain the importance of molting and bird biology

Since feathers are dead structures that cannot repair themselves when damage birds will shed their old feathers and a process called molting. Since a healthy coat is vital, they shed all their feathers each year and grew a new set..

Compare pigment based and structural coloration and feathers

Pigments absorb a certain wavelength and reflect others while structural coloration are produced by the way air filled structures within the feather refract light.