Birds Flashcards (Class Aves)

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Questions and Answers

What is the diagnostic trait that distinguishes the class Aves?

Feathers.

The evolution of feathers was prompted by which selection pressure?

Thermoregulation constraints associated with endothermy.

Which statement is correct?

Birds evolved wings in order to fly.

Birds have wings; therefore, they can fly. (correct)

When did birds first appear in the fossil record?

In the Jurassic (150 mya). Signup and view all the answers

When did birds radiate?

In the Eocene (54 mya). Signup and view all the answers

Why didn't the birds 'inherit the earth' after the decline of the dinosaurs?

They were already in the air. Signup and view all the answers

What are the subclasses of class Aves?

Archornithes, Neornithes, Passerines, Ratites, Carinates. Signup and view all the answers

What characteristics do birds share with reptiles?

Eggs and scales. Signup and view all the answers

What are the selective advantages of flight?

Predator avoidance, ability to escape weather and changing food supplies, ability to exploit difficult prey. Signup and view all the answers

How did bird flight begin?

Ground-up or cursorial theory; tree-down or arboreal theory. Signup and view all the answers

What is the ground-up (cursorial theory)?

Posits that flight arose in small, bipedal terrestrial theropod dinosaurs that sped along the ground. Signup and view all the answers

What is the tree-down (arboreal theory)?

Flight originated when species living in trees developed the ability to glide. Signup and view all the answers

What adaptations make flight economically possible for birds?

Feathers, hollow bones, specialized muscles, and efficient respiratory system. Signup and view all the answers

What limits the size of birds that can fly?

Wing loading, flight speed, and surface/volume ratio. Signup and view all the answers

What flight styles do birds exhibit?

Elliptical wings, high-speed wings, slotted high lift wings, high aspect wings. Signup and view all the answers

What are the anatomical adaptations of flightless running birds like the ostrich?

Distal limb extensions, reduced number of toes, reduced surface area of foot. Signup and view all the answers

Besides flight and thermoregulation, what other functions do feathers provide?

Insulation, defense, display, camouflage, waterproofing. Signup and view all the answers

Why are birds the only vertebrates which do not have species that reproduce by viviparity?

They could not have affected the initial evolutionary transition to egg retention. Signup and view all the answers

Why is monogamy and parental care more pronounced in birds than other vertebrates?

Their young are tiny, helpless, and require extensive parental care. Signup and view all the answers

Why do some birds migrate and how do they navigate?

Cost/benefits of migration and navigation through various clues. Signup and view all the answers

What is the adaptive significance of territorial behavior in birds?

Resource holding strategy influenced by ecological factors. Signup and view all the answers

Study Notes

General Characteristics of Birds

Diagnostic trait of birds (Class Aves) is feathers, made of keratin, not found in other animal classes.
Feathers enable thermoregulation and are crucial for endothermy.

Evolution of Birds

Birds first appeared in the Jurassic period (150 million years ago) and radiated in the Eocene (54 million years ago).
Selection pressure for the evolution of feathers was driven by thermoregulation needs.
Evolution is not goal-oriented; chance mutations guide evolution, influenced by natural selection.

Flight and Adaptations

Flight provides advantages such as predator avoidance, escape from adverse conditions, and access to difficult prey.
Theories on the origin of bird flight include ground-up (cursorial) and tree-down (arboreal).
- Ground-up suggests terrestrial theropods developed flight while chasing prey.
- Tree-down posits gliding evolved into active flight from trees.

Anatomical Adaptations for Flight

Birds possess a series of adaptations including:
- Various types of feathers (contour, flight, down, powder-down).
- A lightweight skeleton with pneumatic bones.
- A powerful muscle system with mass centered for efficient flight.
- Adapted digestive system with a beak suited for diet.
- A four-chambered heart and high blood pressure support active metabolism.
- A respiratory system with air sacs for continuous airflow.
- Excretory adjustments for water conservation (uricolitic) and salt management.

Limitations of Flight and Bird Size

Bird size and ability to fly are constrained by wing loading, flight speed, and surface-to-volume ratio.

Flight Styles

Birds exhibit a variety of flight styles differentiated by wing shape: elliptical, high-speed, slotted high-lift, and high-aspect wings.

Flightless Birds' Anatomy

Flightless birds, like ostriches, display adaptations such as elongated limbs, fewer toes, and reduced foot surface area for running efficiency.

Functions of Feathers

Feathers serve multiple roles beyond flight: insulation, defense, display, camouflage, and waterproofing.

Reproductive Strategies

Birds are unique among vertebrates in lacking viviparous species; historical reproductive strategies led to egg-laying retention.
Monogamy and parental care are prominent due to the helpless nature of hatchlings requiring extensive care.

Migration strategies balance costs and benefits, supported by navigation methods, including celestial guidance and magnetic cues.
Research indicates navigational behaviors in migratory shorebirds through studies conducted on starlings.

Territorial Behavior

Birds, such as the Pacific golden-plover, exhibit territoriality for resource holding, influenced by ecological factors in their habitats.

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Description

This quiz features flashcards focused on Class Aves, detailing key characteristics that define birds, such as feathers. It also explores the evolutionary pressures that led to the development of these unique features. Perfect for students looking to enhance their understanding of avian biology.