Lecture 10 Flashcards
Supplying energy requires sustained aerobic metabolism, which achieved by what?
. A highly efficient respiratory system, coupled to a
. Powerful heart and circulatory system
Temperature regulation in birds is important. How is it done?
Adequate cooling to remove heat from physical activity of flight coupled with adequate insulation to maintain body temperature, and good water economy
What are the two main requirements for evolution of early reptiles to birds?
. Increased aerobic metabolism and ability to deliver
. Insulation required for endothermy
In flight, small birds can sustain how many times BMR for many hours. How does this contrast to other small mammals?
10-25timss BMR contrast to small mammals which can sustain an activity level only 5-6times BMR
Unlike mammals, birds function well at high altitudes. What is this a result of?
A result from an efficient respiratory system
What is the most Energetically expensive more of flight?
Hovering with an oxygen requirement 2.5 times of forward flapping flight
Describe the respiratory system in birds (in detail) and how is this shown experimentally?
They have two lungs connected to the outside via trachea, and connected to thin walled air sacs that fill the chest and the abdominal cavity. Air sacs are connected to the air spaces in bones; shown experimentally that birds with a blocked windpipe can still breath, provided there is a connection between a bone and air
Birds have no diaphragm, so what do they do instead? How does this work?
Breathe by raising and lowering the sternum- this enlarges the chest cavity and expands the air sacs
What does the parabronchi consist of?
Trachea- primary bronchi- secondary bronchi- tertiary bronchi
Explain the air flow in the avian system
Bronchi to posterior air sacs to parabronchi and then back to air sacs
Describe the air sacs in birds
. Thin walled (1-2 cell layers thick)
. Extend throughout the body into the bone cavities
. Poorly supplied with blood vessels
. No direct function in gas exchange
. Act as bellows to help pump air through the lungs
The number of air sacs may vary between species but how many do most have?
9
The number of air sacs in some species is 9, but this may vary, where are these air sacs?
. Paired cervical air sacs in the neck- in frigate birds these are used for display- large inflatable red sacs
. Paired anterior thoracic sacs- forepart of body cavity
. Paired posterior thoracic sacs- upper chest
. Paired abdominal sacs- cushion the abdominal organs and carry air to the legs and pelvic bone
. Single interclavicular air sac- branches penetrate the wing bones, sternum and syrinx- pressure in syrinx from the interclavicular air sac is essential for sound production
The pattern of air flow is a 2-cycle process. Explain this process
. Inhalation 1: air enters and posterior (abdominal) sac via trachea
. Exhalation 1: air moves from abdominal sac through parabronchi into the lungs
. Inhalation 2: air enters the thoracic air sacs
. Exhalation 2: air is forced out through the trachea
Flow of air in through the lung in birds is unidirectional. What does this mean?
Air flows continually in the same direction during both inhalation and exhalation
What is ‘inspirational valving’?
Local swellings of contractions of the air conduits which direct the flow of air
What is the unidirectional flow of air through the lungs of birds controlled by/ not controlled by?
Not maintained by mechanical values but by ‘inspirational valving’ (local swellings or contractions of the air conduits which direct the flow of air)
Birds have relatively smaller lungs per unit body mass than non-flying mammals. How does this work?
Lung rigidity allows a higher respiratory surface area through intense partitioning of the parenchymal tissue. Much greater tissue density than an equivalent mammalian lung
Describe avian lungs in two points
. Compact
. Not inflatable
Terminal gas- exchange components are what?
Air capillaries (blind ending tubules)
Describe air capillaries
Blind ending tubules
How does the air flow in parabronchi?
Unidirectional
How does the Surface density of the blood-gas (tissue) barrier differ between avian and mammal lungs?
It is substantially greater in the avian lung than in the lung of mammals
Where is there cross-current flow in avians?
. Cross-current with respect to flow of air in relation to blood flow through arteriolar at the gas-exchange surfaces
Where is there counter-current flow in avians?
Counter current with respect to flow of blood and air through the lungs
What is the efficiency of avian lungs due to?
. Continuous unidirectional
. High gas exchange surface area per unit volume
. Cross-current and counter current air/blood flows through lung
. Thin gas-exchange barrier
What are the two types of parabronchi?
. Paleopulmonic parabronchi- unidirectional flow (more basic birds)
. Neopulmonic parabronchi- bidirectional flow (c. 20% in some passerines)
What is the evidence for basic avian pulmonary design and flow through ventilation in non-avian Theropod dinosaurs?
. Cervical and abdominal air-sax systems with bone pneumatisation
. Thoracic skeletal prerequisites of avian-style aspiration pump
. Specialisations imply the existence of the basic avian pulmonary body plan in basal neotheropods
. Flow through ventilation of the lung probably a general Theropod characteristic
What is the output of an avian heart and how much goes where? (Compared other parts to how much goes to the legs and explain why there is a difference)
10-20% goes to the legs and the brain. Legs get 3 times the (direct) output of the pectoral muscles, and twice of the brain: mainly for purposes of heat dissipation
Describe an avian heart, compare it to a mammalian heart and why there is a difference
Double circulatory system, 4-chambered heart (unlike reptiles). 50-100% larger and more powerful than for a mammal of equivalent size; larger stroke volume than mammalian hearts; ventricles empty more completely; heart generates higher blood pressure. Heart had to sustain high levels of activity for long periods, deliver fuel and remove toxic waste products
Where are down feathers very important? Where is important not to have down feathers?
In the artic and northern temperature species and it is important for tropical species not to have it
Why is the colour of down feathers important?
Is important with respect to the absorption and reflection of heat; feather position and quality; cooling effects of convective heat loss
Explain how avians dissipate heat (when does it take place and where)
During flight via the thinly feathered central surface of the wings; feet via a network of vessels; countercurrent arrangement of vessels in the head to keep the brain cool
How do avians save heat?
Countercurrent vessels in legs coupled with an arteriovenous shunt to avoid the network of vessels important in heat dissipation
What does the digestive system of avians consist of?
. Oral cavity
. Oesophagus
. Crop
. Stomach: 2 chambers
Explain the oral cavity in avians and why it is the way it is
Has no teeth
Teeth require a heavy jaw bone for support, therefore losing teeth is probably an adaption for flight; tongue and bill whale specialised for different feeding modes
What can the oesophagus do in pigeons?
Produces a nutritious fluid called pigeon milk which is used to feed the nestlings
What is the function of the crop is avians?
Stores and softens food and regulates the flow of food through the gut, therefore does one of the functions that the stomach of mammals does
Name the two chambers of the stomach and what their function is
The proventriculus: An anterior glandular portion, the proventriculus, secreting the peptic enzymes and maintaining an acidic environment
Gizzard: a posterior muscular gizzard used for grinding food, can contain a keratinised layer for grinding
Where is the syrinx located?
The junction of the trachea and the two primary bronchi
Describe the syrinx and how it works
. A unique avian organ (located at the junction of the trachea and the two primary bronchi)
. Via the bronchi; two separate sound sources that can be modulated independently
. Song is achieved by changing the diameter of passageways and tension of tympaniform membranes (which vibrate)
. Pressure in the interclavicular air sac maintains tone in the tympaniform membrane
What are the gonads? What colour are they? How do they change over the course of the year?
. They are paired testes in males
. Vary in colour; cream-coloured to dark Greg or blackish (black due to the presence of melanoblasts)
. Small during most of the year but expand by 400 times during breeding season
In the testes of avians what produces the sperm?
Seminiferous tubules
How does the sperm leave the testes in avians?
Through rete tubules, vas’s efferentia, epididymis and then vas deferens
What happens to the vas deferens in breeding season and why does this happen?
Distal parts of the vas deferens coiling in the vicinity of the cloaca expand as spermatophore storage and maturation organs
What do target cells do?
. Promote development, growth and maintenance of male reproductive organs
. Promotes development of male secondary sex characteristics
What happens to the ovaries in breeding season?
They enlarge, usually only the left ovary develops but can be both in some raptors, kiwis etc.
What does the oviduct do?
Opens to the ovary as a funnel-shaped ostium
What is ovulation?
Release of an egg from a mature follicle
Describe avian eggs (is coating, how it moves etc.)
. Extensive food reserves in the form of concentric layers of yolk; picked up by ostium into Magnum
. Egg receives a coating of albumen (~3 h)
. Egg passed into the isthmus, where the shell membranes are deposited (1 h)
. Egg moves to the uterus, or shell gland, where the calcareous shell is added and the pigment is added in characteristic patterns
. Egg passes into the vagina and cloaca for laying
What do yolks consist of?
21-36% lipids and 16-22% proteins ( the rest is water)
Yolk is suspended in the egg centre by what?
Twisted strands of protein fibres called chalazae
Describe the yolk of an avian egg
. Energy-rich supply of food
. 21-36% lipids and 16-22% proteins (with the rest being water)
. Yolk is suspended in the egg centre by twisted strands of protein fibres called chalazae
. Also contains maternal antibodies to protect embryo
. High levels of pigments (yellow carotenoids)- antioxidants to protect antibodies and other important proteins
Describe the albumen
. 90% water and 10% protein
. Embryos water supply and ‘shock- absorber’
. Buffers embryo from sudden changes in temperature
What are the two shell membranes attached to the shell?
. Inner and outer shell membranes
. Protect egg from bacterial invasion and help prevent rapid evaporation of moisture from the egg
What are the three extra-embryonic membranes that support the embryo?
. Amnion
. Chorion
. Allantois (or allantois sac)
What does the extra-embryonic membrane amnion do?
Surrounds only the embryo; inner layer of cells secretes amniotic fluid in which the embryo floats; fluid keeps the embryo from dying out and protects it
What does the chorion do?
Surrounds all embryonic structures and serves as a protective membrane
What does the allantois (or allantoic sac) do?
Rows larger as embryo grows, fuses with the chorion and is called the chorio-allantoic membrane-permits has exchange and excretion- has storage of nitrogenous wastes- uric acid
What is it called when the chorion fused with the allantois (or allantoic sac)?
The chorio-allantoic membrane
Describe the shell of an avian egg
. Protects the embryo
. Contains pores to permit gas exchange
. Generally white in cavity-nesters and coloured and patterned in open nesters
. Colour due to pigments secreted by cells in the wall of the uterus: biliverdin (blue/green), protoporphyrines (red/black/brown)
Why does the egg shell of an avian egg contains pigments?
. Camouflage- open/ ground nesting species
. Maternal recognition- prevention of blood parasitism
. Strengthening the shell (protoporphyrines)
Describe brood patches in avians (what happens to it, function, temp)
. Changes in appearance and function of the central (abdominal, breast) skin of birds
. Function- to transfer heat to the eggs during incubation
. Feathers are good insulation, so don’t want them between bird and egg
. Swollen skin increases area of contact for heat transfer
. Brood patches temperature is 42 degrees C (in Oystercatchers)
What is brood patch development closely linked to?
The stage of breeding (can occur in both sexes in stages of breeding (where both sexes incubate)
Describe what happens to brooding patches through the stages of breeding (in order)
. Loss of drowsy feathers (defeathering) from breast and belly- nest building and before egg laying is complete
. Epidermal cells proliferate- epidermis expands in area and increases 2-5 times in thickness
. Dermal blood vessels increase in thickness and muscularity (vascularisation)
. Oedema and vascularisation regress during late incubation, brooding or as the young leave the nest
. Feather papillae are reactivated and feathers re-grow, a process that often occurs at the same time as the post-nuptial moult
Different stages of brood patch formation are controlled by hormones. Explain (give hormones and how it works)
. Rising levels of oestrogen in the early stages of breeding initiate defeathering of the brood patch
. Epidermal hyperplasia and vascularisation are also a response to oestrogen, possibly in combination with prolactin and progesterone
. Subsequent oedema results from a combination of oestrogen and prolactin or progesterone
. High oestrogen levels also suppress post-nuptial moult, a mechanism ensuring that moult and breeding do not occur at the same time
Brood patches can be used as an indicator of breeding and progression. Why is this?
. Body mass increases in relation to brood patch development
. Brood patch stages correlate with female reproductive stages
Explain what happens during hatching/ the hatching process
. Just before hatching (~2 days) chick inside the egg begins to breathe with its lungs
. Air space at round end of egg: chick makes a hole in membrane to breathe
. Vocalisations- synchronise hatching, prenatal awareness/ bonding
Begay is used to break the egg when a chick hatched?
Egg tooth is used to break a hole in the shell
What does it mean if a species is semi-precocial? Give examples of species that are
Hatch with eyes open, covered with down, capable of leaving the nest soon after hatching (wall/swim), but stay at the nest and are fed by parents. Percocial but nidicolpus
Gulls and terns
What does it mean if a species is precocial?
Hatched with eyes open, covered with down, leave the nest within two days
What are the 4 types of percocial species? Give examples for each
. Precocial 1 (megapodes) totally independent of their parents
. Percocial 2 (ducks and shorebirds) follow their parents but find their own food
. Percocial 3 (gamebirds) follow their parents and are fed by them
. Percocial 4 (rails and grebes) follow their parents and are fed by them
What does it mean if. Species is semi-altricial?
Hatch covered in down incapable of departing from the nest and are fed by parents
What are the 2 types of semi-altricial hatchings? Give examples
. Semi-altricial 1 (hawks and herons) chicks hatch with their eyes open
. Semi-altricial 2 (owls) hatch with the eyes closed
What does it mean if a species is altricial?
Hatched with eyes closed, with little or no down, incapable of departing from the nest, fed by the parents. All passerines are altricial
