birds
DESCRIPTION
Birds. Chapter 42. Origin and Evolution of Birds. Section 42.1. Important characteristics. Feathers – only birds have them! Wings – modified forelimbs Lightweight, rigid skeleton – hollow bones Endothermic metabolism – 104-106 o F Unique respiratory system – most efficient - PowerPoint PPT PresentationTRANSCRIPT
Important characteristics
Feathers – only birds have them!
Wings – modified forelimbs
Lightweight, rigid skeleton – hollow bones
Endothermic metabolism – 104-106o F
Unique respiratory system – most efficient
Beak – no teeth
Oviparity – eggs incubated by parents
Evolution
Similarities to dinosaurs:– Flexible, S-shaped neck– Unique ankle joint– Hollow bones
Birds evolved from small, fast-running carnivorous dinosaurs
Oldest bird fossil - Archaeopteryx
Archaeopteryx
Jurassic period – 150 million years ago
Similar to modern birds because:– Hollow bones
– Furcula: fused collarbone (aka wishbone)
– Feathers
Similar to dinosaurs because:– Teeth
– Claws on forelimb
– Long, boney tail
Origin of flight
Two major hypotheses:1. Ancestors were tree dwellers that ran
along branches and jumped from tree to tree, gliding wings first evolved then the ability to flap came later.
2. Ancestors were land dwellers that leapt after their prey, wings served to trap or knock down prey and over time became large enough to fly.
Feathers
Modified scales
Two main functions:– Provide lift for flight
– Conserve body heat
Types of feathers:– Down feathers – insulation
– Contour feathers – streamline shape, coloration, insulation
– Flight feathers – on wings and tail for flight
Structure of the feather
Follicles: tiny pits that feather develops fromRachis (Shaft): emerges from the follicleVanes: 2 vanes on opposite side of shaftBarbs: branches of the vaneBarbules: projections on the barbs with microscopic hooksKeratin: protein that makes up the feather
Care of feathers
Preening: use beak to rub feathers with oil secreted by the preen gland at the base of the tail.
Molting or shedding of feathers periodically
Skeleton & Muscles
Thin, hollow bones fused together
Sternum: breastbone is attachment point for flight muscles
Pygostyle: last fused vertebrae that supports the tail feathers
Flight muscles account for 50% of bird’s weight
Metabolism
Endothermic therefore require large quantities of food to generate heat
Aquatic birds have a layer of fat to insulate
Cannot go through long periods of time without food
Digestive & Excretory Systems
Path of food: mouth esophagus crop 2-part stomach (proventriculus & gizzard) small intenstine with bile from liver large intestine cloaca vent
Path of wastes: blood kidneys ureters cloaca (mixes with feces) vent
Respiratory System
Highly efficientPath of air: nostrils trachea branched bronchi lungs (25%) or air sacs (75%) Air sacs:– 9 total– Stores excess air– Allows for oxygenated air in lungs during
exhale and inhale
Nervous System & Sense Organs
Large brains (relative to body size)
Some birds have color vision and/or binocular vision
Some birds have a developed sense of smell
Sense of hearing also important
Reproduction
Sperm movement: testies vasa deferentia cloaca female’s cloaca
Egg movement: ovary oviduct fertilized by sperm addition of shell cloaca vent
Nest Building & Parental Care
Lay eggs in nest
Methods of rearing young:– Precocial: active as soon as hatch– Atricial: helpless when born
One or both parents incubate eggs by sitting on them and covering them with their brood patch – Thickened, featherless patch of skin on
abdomen
Migration
Seasonal movement of birds from one habitat to anotherCues to help navigate:– Position of sun and stars– Topographical landmarks– Magnetic field– Air pressure
Ornithologist: biologist that study birds
Diversity
Beak and claws infer diet and habitat
Most widespread terrestrial animal on planet
23 orders of birds
Order Anseriformes
Examples: swans, geese, and ducks
Aquatic
Webbed feet
Flattened bill
Precocial young, care by female
Order Strigiformes
Examples: owls & nocturnal raptors
Sharp, curved beak
Sharp talons
Keen sense of hearing to detect prey
Order Psittaciformes
Examples: parrots, parakeets, macaws, cockatoos, & cockatiels
Live in the tropics
Strong, hooked beak for opening seeds
Two toes forward, two toes backward for climbing & perching
Highly vocal
Order Picformes
Examples: woodpeckers & toucans
Nest in tree cavities
Diversity of bills based upon diet
Same feet as parrots
Order Passeriformes
Examples: familiar birds (robins, blue jays, cardinals, etc)
perching birds: 3 toes forward, 1 toe backward
songbirds: males produce songs to attract mate and warn away other males– Syrinx produces sound at base of trachea
Order Columbiformes
Examples: pigeons & doves
Plump-breasted, small heads
Short neck, legs, and beak
Crop secretes nutritious milk-like fluid to feed young– Crop milk
Order Ciconiiformes
Examples: herons, storks, raptors, & penguins
World-wide distribution– Habitat determines adaptations
Many are wading birds
Order Galliformes
Examples: turkeys, pheasants, chickens, grouse, & quail
Fowl
Terrestrial birds
Plump-bodies with limited flying ability