AVES

Evolutionary History and Characteristics

Biology 1123

By: Jonathan Shute, Ryan Carver, Hilary Smith & Mary Ann Kavanaugh

Ancestry

Archaeopteryx:- From the Jurassic Period- Feathers around tail and arms- Had teeth and long, bony tail

- Reduction of anatomical elements to reduce weight

- First to disappear – bony tail, reduced to a ‘pygostyle (final few caudal vertebrae fused into a single ossification) supporting feathers and musculature

- Cretaceous – more changes in skeletal structure to improve flight

LINEAGES

Paleognaths

- Ostriches, emus, kiwis

- Loss of flight happened independently

Neognaths Galliformes: turkeys, chickens Anseriformes: ducks, geese,

swans

-Defining cladistics trait between reptiles and birds is flight

Modern birds are classified in Neornithes, which are divided into two categories:

CHARACTERISTICS OF AVES

WHY WINGS EVOLVED

The evolution of wings is highly debated within the scientific community. The most widely accepted hypothesis are:

-To escape predators-To aide bipedal animals in jumping higher-To help move from place to place safely-To attain access to new habitat, food sources, and unoccupied niches

A FORMULA FOR FLIGHT: WINGS AND FEATHERS

There are 3 main types of feathers:1)Filoplumes2)Contour feathers3)Down feathers

-Feathers evolved from scales, and are composed of keratin.

-Feathers are strong and flexible, allowing the Aves to produce lift, and forward movement.

Feathers have many evolutionary advantages like:-Thermoregulation-Camouflage-Waterproofing-Flight!

Wings and feathers aide birds in their primary mode of locomotion: flight.

Flight is achieved with the help of a lightweight skeleton and hollow bones, along with a modified forelimb.

The highly modified forelimbs that are characteristic of all birds, are essential to flight. The wings are used to lift, glide, flap, and drag.

hum= humerus, r= radius, u= ulna, c= carpus, mc= metacarpus, I-III= numbered digits

VISION

- Most important sense for birds- Eye is not spherical, flatter

shape enables more of visual field to be in focus

- Lens is pushed further forward than in reptiles

- Four types of colour receptors- Ability to perceive violet-

ultraviolet part of the spectrum

- More light receptors in the retina than other mammals, more nerve connections between the photoreceptors and the brain

Certain bird groups have specific modifications…

Diurnal birds of prey Nocturnal birds Water birds

REFERENCES:- Memorial Universityhttp://www.mun.ca/biology/scarr/Bird_Wing_Types.htm- Phys. Orghttp://phys.org/news/2013-02-birds-evolved-ultraviolet-vision.html

-University of California, Berkley http://evolution.berkeley.edu/evolibrary/article/evograms_06http://www.ucmp.berkeley.edu/vertebrates/flight/evolve.html

- Scientific Americanhttp://

www.nature.com/scientificamerican/journal/v293/n1/box/scientificamerican0705-56_BX5.html

- Shipman, P. (1998)Taking wing: Archaeopteryx and the evolution of bird flight. The Auk, 115(3),

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