Birds are originally thought to be descended from therapod dinosaurs. Although there are contentions of this.
This was happening 150 million years ago sponges 400 million years ago!
Archaeopteryx was first discovered in 1861- 2 years after origin of the species- contained both reptile and bird features.Earlier discoveries of feathers on reptiles have been found and it is thought that these developed due to an the need to keep warm- these in turn evolved in flight adaptionsExaptation- a "pre-adaptation": a feature that has evolved in one environment, but which turns out to be beneficial in a new, changed environment. The limbs and lungs of lobe-finned fishes, which had evolved before one line of these fish developed into amphibians, are examples of exaptations.http://sci.waikato.ac.nz/evolution/glossary.shtml#ExaptationWhy did the bird develop-at a time when there was an evolutionary exlposion
Birds is a truly messy lineage due to many failed evolutionary adaption's being present in the fossil record.
Water diving birds have smaller air pockets allowing them to dive deeper
Barbed- allows for a strong yet lightweight structureArticle to hand out- feather evolution- discuss- 5 mins to read
Feather overlap like roof slates to provide waterproofingFiloplume found at the base of neckBristle feathers provide protection to birds eyesDowny feathers have no barbs- fluffy = lots of air pockets= warmth!
2 pigments responsible for bird egg colourOocyan- which is derived form pile and is responsible for blue/green shadesProtoporphyrin- blood derivative which is responsible for spots, patterns and some general colour
Where do birds nest?2 pigments responsible for bird egg colourOocyan- which is derived form pile and is responsible for blue/green shadesProtoporphyrin- blood derivative which is responsible for spots, patterns and some general colour
• Archaeopteryx- Cretaceous (first bird- like fossil), but had:- Clawed forelimbs- Teeth- Long tail with vertebrae• Weak flyer• Their evolution is still hotly contested among scientists
Small digression-•Potential that bird ancestors were in fact crocodiles•New evidence that dinosaurs came after birds in theevolutionary scale•Continually new fossil discoveries•Always open to interpretation and debate•See here
FlightA variety of slow motion clipsSparrowIn FlightDuckDipper underwater
• Modern birds have developed a variety of means to enable efficient flight• Honeycombed bone structure (reduced weight)• Absence of some organs (right ovary)• Toothless (food ground in gizzard)• Efficient lungs and heart• Well developed sight (best of all vertebrates)• Large brains - complex behaviour• Very muscular pectoral muscles anchored to keel on breastbone• Fused digits - even airflow• Wings and feathers
Flight- evolutionThree Theories:• Cursorial - used speed from running to gain momentum• Arborial - claws on wings enabled climbing and then gliding• Pouncing proavis - ancestors pounced on prey from trees etc. Developing wings let them steer.
Anatomy and Physiology – gas exchange• Extremely complex• Pharynx has a voice box called a syrinx.• This is located between the trachea and the bronchi.• Bronchi link to air sacs in the thorax and abdomen and both lead to the lungs.• Lungs are made of parabronchi, a series of tubes.
Anatomy and Physiology – gas exchange• There are two ventilatory cycles to move a volume of air into and out of the bird.• This respiratory method is the most efficient in the vertebrate classes. Birds have a high metabolic rate.• This system also allows them to fly at high altitudes – some geese can fly at over 9000m.
Physiology – thermoregulation• Birds regulate their body temperature between 38 and 45 C. Below the lower range birds become torpid (slow, sleepy) and eventually die. Above the upper range and they die of heat exhaustion.• Heat maintained by fluffing feathers.• Feet have little musculature or blood supply to prevent heat loss.
Anatomy and Physiology – vision• Birds have rods and cones in their retinas.• Birds can double focus – that is, they can focus near and far.• Binocular (3D vision) depends on location of eyes.
Anatomy and Physiology – hearing• Birds have sensitive hearing.• No external ears but adapted feathers to allow sound through.• Hearing range 100 – 15000 Hz• For humans it is 20 – 17000 Hz.
Anatomy and Physiology – excretion• Kidneys are paired and lead to the cloaca.• Kidneys cannot concentrate salt so bird relies on salt glands near the nostril.• Kidneys produce uric acid as opposed to urine.
Finding a mate• Territories established by most male birds.• Courtship – plumage colours and appendages.• Different pairing arrangements• Monogamy Usually for the season, sometimes for life (swans, eagles, etc). Happens when resources are present.
Anatomy and Physiology – reproduction• Birds are oviparous• Have paired gonads• Usually only the left ovary develops.• Ovary is enveloped by ostium (funnel) that collects egg.• Egg is fertilised in oviduct.• Fertilised egg is passed to shell gland.• Except for certain waterfowl and ostriches, no penis – sperm is passed by aligning male cloaca to the female cloaca.