Vertebrates 2 Flashcards
What are the fish that gave rise to the tetrapods often known as?
Tetrapodomorph fish
The spiracular region is the beginnings of a tetrapod … …
middle ear
Tiktaalik was discovered in … …
arctic canada
- dates to 383MYA
… -> Tiktaalik -> Tetrapods
Panderichthys
Tiktaalik had reduced … …, allowing more … flexibility, larger … and a longer …. It also had flexible pectoral fins that may have acted as …
gill covers, head, ribs, snout, props (bones homologous to tetrapod limbs)
Name two of the first tetrapods (from 365MYA)
Acanthostega and icthyostega
- had pelvis, limb formation, ribs
- although still had long tail and operculum
- had polydactyly
What is the most basal described tetrapod (described recently)?
Parmastega
- eyes on top of head
- spiracle on top of head - for gaining air?
These tetrapods had features advantageous to life … …. It is important to distinguish the evolution of tetrapods and the evolution of terrestrial vertebrate life as 2 separate events
in water
Name a fish that uses fins for walking
Frog fish (type of angler fish)
Tetrapod like tracks have been found before panderichthyes
which really throws a spanner in the works dunnit?
Reduction of digits in birds and mammals is usually associated with…
high speed running (e.g. ostriches and some artiodactyls e.g. antelopes)
What are the two ways in which number of digits can be reduced?
- Reduced expression of a gene called PTCH1
- Cell death (apoptosis)
convergent evolution is shown in these ways of reducing digits (e.g. pigs and cattle reduced gene expression, camels and horses cell death)
The amniotes are all tetrapods except…
amphibians
Which tetrapods gave rise to the amphibians?
Batrachomorphs
temnospondylls and lepospondylls
What are the three amphibian groups?
- urodeles, anurans, caecilians
Amphibians have … skin
permeable - susceptible to water loss and vulnerable to things in their environment
The African clawed frog has…
a lateral line and fish like eyes as it is a purely aquatic animal
Anuran body form evolved because of advantage in…
swimming with hind legs
Anurans have reduced … and an enlarged … called a …
vertebrae, pelvis, urostyle
Toads hop more than they jump, leaving them vulnerable to predation. Therefore, many have evolved…
poison gland in their skin for protection
Caecilians are either … or …
burrowing, aquatic
- why they have lost limbs
Unlike anurans and urodeles, caecilians have …
scales
Amphibians have the … … and the …-… … in their ears
papilla amphibiorum, operculum-columella complex
Amphibians gained … rods in their retina, in addition to the .. rods (excluding caecilians)
green, red
Amphibians have … teeth
pedicellate (dentine separated by connective tissue)
Amphibians have a … … muscle which causes their eyes to bulge forward, enlarging their … …, and allows the bilateral turning of their eyes for hunting
levator bulbi, buccal cavity
Caecilians have … fertilisation and…
internal, give birth to live young or lay eggs
Female caecilians can give birth to up to … offspring, which have up to … the body length of adults. Energy for growth is first supplied by yolk, then by the mother (“… …” secretions from walls of oviducts)
nine, 60%, uterine milk
Foetal caecilians have foetal … for scraping the oviduct walls for nourishment (evolved several times independently)
dentitions
Axolotls are a … species
paedomorphic
Urodeles fertilise internally using … made of a … base with a sperm cap
spermatophores, gelatinous
Salamanders display … and … cues for mate attraction
visual, pheromonal
Salamanders transfer pheromones by … … in aquatic environments and skin slapping, biting or rubbing in terrestrial species
tail fanning
Most urodeles have aquatic eggs and larvae. Purely terrestrial species are …
ovoviviparous
In some species of urodele, paedomorphosis depends on….
ecological conditions
All frogs are …
carnivorous
The tibia and fibula of anurans are …
fused
- for extra leg strength
The amphibian life cycle we know and love is…
only really common in temperate regions
There is less predation pressure…
on land than in aquatic habitats
-> requires various, often convergent adaptations against desssication
Increasing egg and larval size enhances…
their survival rate
Another way to enhance survival is to increase…
parental care
- this has also evolved many times convergently
- trade-off of production of fewer, more costly eggs with longer developmental time vs many eggs
Foam nests are produced from secretions from the …
oviduct - frothed up by males and females hind legs - protects eggs from drying out and hides them fro predators - has evolved six times across different continents
Some frogs lay eggs on leaves that…
overhang water, so they fall in once they hatch - has evolved 3 times - sometimes folded into large leaves, sometimes guarded by male
Some terrestrial frogs display … and some even display … or … brooding
ovoviviparity (and 3 true viviparity), mouth, stomach
Male poison dart frogs often have (and defend) territories of up to several hundred m2. They have terrestrial egg clutches, and tadpoles hatch and…
climb onto their parent’s (male or female) back, where they are transported to aquatic sites. Small ephemeral water bodies are usually predator-free, but also contain no food, so some species feed tadpoles with unfertilised eggs
For reproduction, frogs (mostly) communicate …
acoustically (unlike pheromones and visual cues in salamanders) - generally only males call - amplified by vocal sack in circle around frog
What are the pros and cons of acoustic signalling?
Pros - easy, circumvent obstacles, works in the dark
Cons - usually travel short distances and cover short time periods. Can attract predators. Costly to produce
Tungara frogs - whines or whines+chucks
Chucks increase predation risk but males who produce more chucks chosen by females
- only one male - no chucks only whines
- more males = Whines+chucks
Frogs that live in very noisy environments, e.g. waterfalls, use … signals
visual - e.g. lifting legs (evolved convergently 3 times)
When did the most amniote diversification occur?
Permian period
There was a division of the tetrapods into the … (which gave rise to the amphibians) and the … (which gave rise to the amniotes)
batrachomorphs, reptilomorphs
The diversification of the tetrapods was thought to be driven by the radiation of … and possibly increased diversification of …
insects, vegetation
The Amniotes (during the permian period) diversified into the … (which gave rise to the mammals) and the … (which gave rise to all the other amniotes (reptiles and birds)
Synapsids, sauropsids
What is the main feature that draws together the amniotes?
The amniote egg - 3 extraembryonic membranes (chorion, allantois, amnion) - no larval stage - has to be laid on land (egg is porous and we don’t want no drowning up in here)
What is the allantois for?
Waste products + gaseous exchange (as heavily vascularised)
What is the amnion for?
Encloses and protects embryo, prevents dessication
What is the chorion for?
Encloses everything including yolk, embryo and allantois - for gas exchange
The ancestral amniote shell was rather …, whereas modern bird and lizard shells, for example, have … deposits, making them more robust and less vulnerable to desiccation
leathery (had to be buried to keep them damp and prevent dessication), calcium
The amniote egg has increased … … for gaseous exchange and increased …, meaning larger eggs can be produced, meaning larger adults can be produced
Surface area, support
What are some main derived features of amniotes?
- Thicker, keratinised skin, with more lipids (more waterproof). Elaborations on skin, such as scales, hair and feathers (keratin) - anatomical placode forms all of these (thickening of the epidermis) - homologous structures
- costal (rib) ventilation - more dependent on lungs for respiration - allows longer neck - allows more complex nerves controlling forelimb
- Temporal fenestration - may allow muscles to expand and strengthen
There are two groups of diapsids:
Archosaurs - birds, dinosaurs, crocodilians (turtles are sister group)
Lepidosaurs - lizards, snakes, tuatara
non-amniotes required larger head for … rather than … respiration
buccal, costal
Turtles are … but look …
diapsid, anapsid
The turtles (Chelonia) have a … above their vertebrae and a … below, which are bony plates. Elaborations on these plates, made of keratin, are called …. The vertebrae and ribs are actually attached to the …
carapace, plastron, scutes, carapace
There are no … in modern day turtles
teeth
Odontechelys had a … but not a developed …, which suggests an aquatic origin because…
plastron, carapace, predators may have attacked from below (this would not happen on land)
Turtle lungs are attached to their …, which is controlled by muscles that expand or compress it. This is how the lungs are inflated or deflated.
viscera (gut)
It is believed turtles use …, … … and … for navigation
light, wave direction, magnetism
Turtles show …-… … determination
temperature-dependent sex
- males at low temps, females at high
- thought to be ancestral amniote condition
In lizards, females are produced at … temperatures and males at … temperatures
low, high
Usually the larger sex is produced at the … temperature
higher
Where are tuataras found?
New Zealand (surrounding islands)
Tuataras are … animals, which is unusual for a lizard
nocturnal (low body temp) - as feed on insects - live in seabird burrows
The squamates are the…
lizards and snakes - represent >95% of all living reptiles
The squamates have a … … skull
modified diapsid - loss of bottom arch in lizards and loss of top arch as well in snakes
What is the largest lizard?
Komodo dragon (3m long)
What is the smallest lizard?
Dwarf gecko (1.6cm long)
Smaller lizards tend to be … and larger lizards tend to be …, with the exception of monitor lizards (including Komodo dragon) which are …
insectivorous, herbivorous, carnivorous
The komodo dragon is an ambush predator. They do not have a particularly strong … …, although their skull is very resilient to …. Their venom is…
bite force, stress, homologous to that of venomous snakes
Komodo dragons have a … … which allows them to ventilate their lungs independently of their movement, allowing them to move faster than many lizards
gular pump
It is believed that … reduction in lizards has evolved over … times
limb, 60
Snakes are believed to have branched from the lizards in the … period, due to becoming burrowing/digging lizards
cretaceous
Snakes have many … …, due to a change in gene expression (oct4 - when inserted into mice they develop more thoracic vertebrae and reduced limbs)
thoracic vertebrae
Snakes lack … and … … (but they are vestigial in pythons and boas)
pectoral, pelvic girdles
Snakes have an incredibly … jaw due to many … of ….
flexible, points, articulation
The main 2 types of immobilisation carried out by snakes are…
using venomous fangs or constriction (reduces oxygen supply to organs
Alligators tend to be found in…
the new world (apart from the chinese alligator)
Gharials are found in…
india, indonesia, malaysia
Crocodiles have a … skull and teeth in …, as well as a … … which separates the nostrils from the mouth.
diapsid, sockets (thecodont), secondary palate (can open mouth underwater and doesn’t interfere with breathing - most reptiles don’t have - also have gular valve)
Crocodilians have sensory structures around their mouths and heads. They are extremely sensitive to touch and vibrations. Why may this be?
- Sense vibrations from prey
- Careful handling offspring during parental care
Gharials largely feed on ….
fish
Other crocodilians, including the false gharial, are..
more generalist feeders
Crocodilians have been seen displaying … behaviour
play (socially and on their own + with objects)
Crocodiles can both … and …
walk, gallop
What are some defining characteristics of birds?
- bills
- feathers
- wings
- hollow bones
- gizzards with stones in (instead of teeth)
- warm blooded (slightly warmer than ours)
There are around … species of birds
10,000
What are the three main theories on the phylogenetic origin of birds?
- Direct descendants of crocodilians
- Descendants of unknown group within the archosaurs
- Descendants of the Therapoda (small, carnivorous dinosaurs) - became established through phylogenetic analysis and fossil discoveries in the last 20 years - in particular Dromeosaurs, which couldn’t fly but had feathers
Feathers are modified …
scales
Feathers may have evolved for…
- sexual selection (melanosomes preserved in fossils)
- insulation (may well have been warm blooded) - convergent to fur
Birds evolved probably sometime in the … period, but diversified in the … period
jurassic, cretaceous
Through time along the dinosaur lineage there is a common trend of…
becoming smaller (to birds)
Birds have achieved their small size partly through …, shown by…
paedomorphosis, the fact that there is less difference between the juvenile and adult skull of bird-like dinosaurs as you go further along the archosaur lineage. Archaeopteryx juveniles had very similar skulls to adults.
Birds have larger … relative to body size and larger …, with much of the brain devoted to …
brains, eyes, vision
Raptors have a … second toe
hyperextendible
On the front of a bird’s wing is the …, used for directing airflow over the wing
alula - very reduced first digit
What features do birds share with reptile dinosaurs?
- Scales
- Egg-laying
- Bipedal
- S-shaped neck
- Tridactyl foot
- Wishbone and fused sternum (Therapods)
- Digitigrade posture (toes bear weight)
When was the first archaeopteryx fossil discovered?
1861 (most valuable fossil specimen on the planet)
- 11 more have been found since (12 in total)
What are the reptile features of archaeopteryx?
Thick bones, toothed jaw, no fusion of vertebrae
what are the avian features of archaeopteryx?
Well-developed feathers (including asymmetrical wing feathers), three fingers, s-shaped neck, wishbone (fused clavicle)
Why are wing feathers asymmetrical?
More aerodynamic - asymmetrical feathers suggest ability to fly
In the most recent archaeopteryx specimen there is evidence of…
a hyperextendible second toe as seen in dromaeosaurs (but not present in modern birds)
Archaeopterx had a longer … than modern birds, a smaller …, and a much smaller …
tail, braincase, sternum
Removing archaeopteryx from the base of the aves to nest within Deinonychosauria implies…
that typical flight evolved at least twice, or was subsequently lost or modified in some deinonychosaurians. (we know that flight evolved twice in the reptiles already though - think of the pterosaurs)
Give early examples of birds/bird-like therapods
- Mononykus - mongolian specimens with strange forelimbs and no ability to fly, but otherwise similar to other known birds
- Iberomesornis - early cretaceous bird from central spain. Structural advancements in forelimbs and tail compared to archaeopteryx, including ossified sternum and a pygostyle
- Enantiornithes (opposite birds)
- Hesperornis - early flightless sea birds
In 1999 National Geographic were approached with a new specimen claimed to be the link between birds and non-bird dinosaurs: “Archaeoraptor”. However..
subsequent analysis showed that this specimen was artificially composed of a Dromaeosaur and an early bird
Modern birds diverged around …
150MYA
The ability of birds to … is tightly linked with their success as the most … group of terrestrial vertebrates
fly, diverse
- given birds niche opportunities not otherwise available
What are the advantages of flight?
- Can escape predators
- Can migrate (to exploit different niches at different times of year) - rather than hibernation
- Efficient way of foraging as can cover larger area
- Can move quickly (peregrine is fastest animal at 200km/h in stoop)
- Can colonise otherwise inaccessible habitats e.g. remote islands
- Cost-effective locomotion (gliding)
What are the constraints of flight?
- anatomical restrictions
- Energetically costly
- Limits size and weight (Muscular power needed to take off increases by factor of 2.25 for each doubling of biomass)
Many dinosaurs had feathers. Flight possibly evolved in more than one lineage.
yes
What are the two main theories for the evolution of flight?
- Cursorial - running (stabilisation and/or catching prey) - tended to be more supported by archaeologists
- Arboreal - from the trees down - getting from one place to another
What is the WAIR theory?
Wing-Assisted Incline Running - displayed in modern brids such as pigeons and partridge juveniles
Until recently, it was considered more likely that flight evolved from a … stage where wings were used for prey capture:
- … morphological evidence of climbing abilities
- lack of … in locations where Archaeopteryx was found
- Spread of feathered forelimbs was originally probably for … during running
- Archaeopteryx could most probably glide, but its ability for … in flight is in doubt due to the likely lack of a … …
cursorial, ambiguous, trees, stabilisation, flapping, flexible wrist
However, what are the problems with the cursorial origin of flight theory?
- max running speed is 2m/s (from footprints) but estimated min flying speed is 6m/s
- supplying high energy demands of flight (flight against gravity)
- problem of explaining origin of the ‘flight’ stroke in an earthbound organism
Hoatzin offspring have…
claws - evidence for arboreal evolution - similar to archaeopteryx
What is Feduccia’s claw arc analysis?
Climbers, perchers and ground-dwelling birds have different depths of of claw arc. He concluded that Archaeopteryx was an arboreal, climbing bird that glided from heights
- forelimbs correspond with climbers, hind limbs correspond with perchers
In 2001 and 2002, new specimens of dromaeosaurs were discovered in China (genus Microraptor) - they had … similar to archaeopteryx and … similar to ancient arboreal birds. However, their … were feathered. A four limbed flight would make more sense if early birds were …
forelimbs, hindlimbs, hindlimbs, arboreal
- late jurassic
What are feathers primarily made of?
B-Keratin (beta) - >90%
1% lipids, 8% water, pigments
Filoplume feathers and bristles are used…
as sensory receptors
A wing functions as both an aerofoil (… …) and forward motion (…). Their shape, area and position can be modified, making them more aerodynamically complex than aeroplanes
lifting surface, propeller
How does an aerofoil wing work?
Bottom surface of the wing pushes the air forward and down, creating an area of high pressure below the wing and low pressure above –> lift
The alula produces a … in front of the airfoil to reduce …
slot, turbulence
Slots between feathers on wing tips reduce tip …
vortex (stalling)
The … feathers generate thrust and the … feathers generate lift
primary, secondary
A bird’s lung is…
one-way
Colours and patterns are important for … … and …, and are generated through a combination of … and … characteristics
sexual selection, crypsis, pigment, structural
Iridescence is created by…
the interference of reflections from many layers of melanin platelets - change in colour viewed from different angles
Evidence remains … in arboreal vs cursorial theories
equivocal
