Vertebrate Zoology Flashcards
(189 cards)
1
Q
What phylum are vertebrates in?
A
Vertebrates are not in a phylum. They are a Subphylum.
2
Q
What is the ratio of invertebrates to vertebrates?
A
Less than 5% of species are vertebrates. They are important but only account for a small fraction of animal diversity.
3
Q
What is the difference between Porifera and Eumetazoa in the Animal KIngdom?
A
Porifera have a non-symmetrical body whereas Eumetazoa have a symmetrical body.
4
Q
What are the characteristics of Cnidaria and Ctenophora
A
- Diploblastic
- Radially symmetrical
5
Q
What are the characteristics of Bilateria?
A
- Tripoblastic
- Bilaterally symmetrical
6
Q
What two other categories can Bilateria be split into?
A
- Deuterostomia
- Protostomia
7
Q
What are the characteristics of Protostomia?
A
- Include Ecdysozoa and Lophotrochozoa
- Primary mouth
- Schizocoely
- Sprial cleavage and mosaic development
8
Q
What are the characteristics of Deuterostomia?
A
- Include Echinodermata, Hemichordata and Chordata
- Secondary mouth
- Enterocoely
- Radial cleavage and regulative development
9
Q
Chordates are united by five synapomorphies which set them apart from non-chordates?
A
1) Notochord
2) Dorsal nerve cord
3) Pharyngeal slits
4) Endostyle
5) Muscular, postanal tail
These are always found in chordates, at least at some embryonic stage.
10
Q
What is the Notochord?
A
It is a flexible rod of fluid-filled cells to which muscles attach. It provides structural support and allows undulatory movement (swimming).
11
Q
What is the first endoskeletal structure to appear in an embryo?
A
The Notochord. It induces several other structures during development. In most vertebrates it is only in embryo as it is then replaced by vertebrae.
12
Q
What is the Dorsal nerve chord generally?
A
It is a hollow tube. Dorsal, because it forms from ectoderm near the embryos surface.
13
Q
What is the Dorsal nerve chord in vertebrates?
A
A spinal cord, protected by vertebrae. The anterior end swells up and develops into brain.
14
Q
What are Pharyngeal slits in aquatic chordates?
A
They are openings from pharyngeal cavity to outside and are formed by fusion of ecto- and endodermal pockets. They are used for filter feeding or respiration.
15
Q
What are Pharyngeal pouches in four-limbed vertebrates (tetrapods)?
A
They are pockets which do not break through pharyngeal cavity. They form several structures (e.g. Eustachian tube, middle ear cavity).
There are similar structures in some non-chordates, so could be more ancestral.
16
Q
What is the Endostyle in basal chordates?
A
Secretes mucus that traps food particles. Functions in filter feeding together with pharyngeal slits. Some cells secrete iodinated proteins.
17
Q
What is the Endostyle in vertebrates?
A
Gives rise to thyroid gland.
18
Q
What is the Muscular, postanal tail?
A
It was evolved for propulsion in water. Locomotor apparatus could be extended without having to reorganise gut. Leads to increased motility. Improved efficiency in fish by adding fins. Vestigial in humans.
19
Q
The phylum Chordata is split into which three subphylum’s?
A
- Cephalochordata
- Urochordata
- Vertebrata (= Craniata)
20
Q
What are the two main characteristics which make vertebrates different?
A
- The Vertebral column
- The Braincase (cranium)
21
Q
What are the vertebrate innovations?
A
- Strong endoskeleton with large areas for muscle attachment (larger body size, increased speed and mobility)
- Head with brain and sensory systems (sensory, motor and integrative control)
- Enhanced respiration e.g. pharyngeal slits, enhanced circulation and enhanced digestion (higher metabolic rate)
22
Q
What do the vertebrate innovations allow the species to achieve?
A
Gives them the ability to have an active predatory lifestyle.
23
Q
What is a vertebrates neural crest?
A
It is a population of cells active during neurulation. They migrate through embryo on distinct paths. Initially totipotent and form variety of structures. Important in head formation.
24
Q
What are ectodermal placodes in vertebrates?
A
Embryonic tissues from which sense organs are derived. Outgrowth of forebrain interacts with ectodermal thickening.
25
What are examples of ectodermal placodes in vertebrates?
- Optic placode --> Eyes
- Nasal Placode --> Nasal Sac
- Otic placode --> Vestibular system
- Epibranchial placode --> Taste buds
- Dorso-lateral placode --> Other hair cells
26
What is likely to be involved in the vertebrate innovations?
Gene duplications (probably even whole-genome duplications).
27
Why are gene duplications advantageous?
- Neofunctionalization: Gene copy adopts a new function
| - Subfunctionalisation: Removes genetic constrains by splitting pleiotropic genes into separate functions
28
When are gene duplications particularly effective?
If regulatory genes are affected.
29
What are Hox Genes?
Master gene switches that code for transcription factors. Command up to 100 structural genes that form body parts. Control body plan of vertebrate embryos (microRNAs, which regulate gene expression seem to be important as well).
30
Almost half of the known species of vertebrates are what?
Fish.
31
What is the rough definition of a fish?
"A poikilothermic, aquatic chordate with appendages (when present) developed as fins, whose cheif respiratory organs are gills and whose body is usually covered with scales" - Berra 1989
32
Why are definitions dangerous?
There are exceptions/adaptations to the definition. This is due to selection pressures causing adaptions (e.g. eels have no scales, lungfish have lungs).
33
What are commonly mistaken as fish?
- Starfish
- Crayfish
- Jellyfish
34
What is the Ichthyology of fishes?
- Over 30,000 extant species
- 5 classes
- 51 orders
- 482 families
Huge phylum with immense diversity
35
What is a Ostraconderm?
- Paraphyletic group (two groups)
- Heavily armored jawless fishlike vertebrates
- Dominated Silurian and Devonian
- Covered with bony plates and scales
- Surfaced in enamel and dentine like teeth
- Protection from invertebrate predators
- Lacked pectoral fins, probably poor swimmers
36
What are the class known as Myxini?
- Hagfish or slime eels
- Contentious systematics (6 genera with 43 species)
- Temperate marine species
- Almost unchanged in 400my
- nostril just for smelling
37
What are the characteristics of Hagfish slime?
- Produce copious volume of thick slime
- Slime glands
- Thread cells + keratin
Function: suffocate prey (although unlikely as they would be bad at catching live prey), protection while feeding (from infection or from predators), competition for food, stabilize burrow
38
What are the feeding characteristics of Hagfish?
Scavengers (poor eyesight, excellent sense of smell, sensory barbels for finding prey)
Agnatha --> jawless (rasping dental plate)
Knot tying (for feeding and slime removal)
39
What are additional facts about Hagfish?
- Iso-osmotic
- Scaleless
- No lateral line
- single 3 chambered heart and 3 single chambered accessory hearts
40
What are the class known as "Cephalospidomorphi"?
- Lampreys
- 6 genera with 41 species
- Temperate freshwater and marine
41
What are general Lamprey biology characteristics?
- Jawless (central mouth surrounded by disc of teeth, anticoagulant - stops wound healing and flow of blood to feed on)
- No scales
- Reasonable sight
- Single nostril
- No stomach
- No paired fins
42
What is the reproduction characteristics of a Lamprey?
- Semelparous (only reproduce once)
- Male builds nest
- Ammocoete larvae (toothless filter feeders, burrowers, for up to 7 yrs)
- Transform into adults (non-parasitic form, 6months no feeding)
- Parasitic form (up to 3 years)
- All spawn in freshwater
43
How to Lampreys damage their host?
Rasp through skin and parasitize host. Take up to 30% of their own weight in blood daily. Normally fatal for host before or after detachment through blood loss or infection.
44
Where did jaws on fish evolve from?
Evolved from the agnathan gill arches losing gill slits, which then they became smaller and robust and finally moved forward and teeth formed. Jaws allow:
- active hunting and capture of prey
- crushing of shells
- defense against predators
- lead to a decrease in armor
45
How are agnathans limited (e.g. lampreys and hagfish)?
Limited to planktivory, detrivory, parasitism and microcarnivory due to being jawless.
46
What are the class "Chondrichthyes"?
- Sharks, rays, and ratfish
- Cartilage skeleton
- ~900 species
- 2 subclasses (Holocephali and Elasmobrachii)
- Multiple exposed gill openings
- Placoid scales
- Oil filled liver for buoyancy (takes months to change buoyancy)
- Upper jaw not fused to braincase
- teeth not fixed to the jaw (go through thousands of teeth in their lifetime)
47
What are the subclass "Holocephali"?
- Chimaeras
- 30 species (diverged 360mya)
- Marine (80 - 3000 meters)
48
What are chimeras?
- Cartilage skeleton
- Internal fertilizations
- Oviparous (lay eggs)
- No swim bladder (have oil filled liver instead for buoyancy)
- Poison spine containing venom
- Teeth (crushing plates)
- Single gill cover with 4 slits
- Mix of sharklike and bony fish structures
49
What are two super classes in the Chordata?
- The Agnatha (containing the Myxini and Cephalospidomorphi)
- The Gnathostomata (containing the Chondrichthyes, Sarcopterygii, Actinoptergygii, Amphibia, Reptilia, Aves and Mammalia)
50
What are the subclass "Elasmobranchii"?
- Sharks (~400 species)
| - Skates and rays (~500 species)
51
What are the characteristics of sharks?
- 7 orders (~400 species)
- Cartilaginous skeleton
- 5 or 7 gill slits
- Internal fertilization
- Placoid scales (energetically efficient and quiet)
- Replacement dentition
- Marine (mostly, bull sharks in rivers)
- Advanced sense (Olfaction - smell, Electric, Low frequency sound)
52
What are the characteristics of Chondrichthyan Teeth?
- Modified denticles
- Continually replaced (conveyor belt, outer teeth moving in towards the mouth, lemon sharks grow a new row every 8 days)
- Design varies with prey (fish eaters have sharp teeth, mollusc eaters have flat crushing teeth)
53
What are the characteristics of Rays and Skates?
- 1 order (~500)
- Dorso-ventrally flattened
- Ventral gill openings - underside of body, not good for swimming on top of soft sediment, need adaptions
- Enlarged pectoral fins
- Crushing teeth or no teeth
- No anal fin
- Marine and freshwater
54
What are the characteristics of Elasmobranch reproduction?
- Oviparity (Skates and some sharks, mermaid's purses)
- Ovo-viviparity (most common, dogfish, tiger shark ect, yolk-sac viviparity, no extra nutrition)
- Viviparity (great white shark, hammerhead shark, Yolk-sac viviparity, extra nutrition)
55
What are the characteristics of the Early bony fish?
- Acanthodii
- 20-200 cm
- Marine and freshwater
- All extinct
- Water column feeders
- Armour reduced to small overlapping scales
- Cartilaginous (some ossification e.g. reinforced with bone)
56
What are the characteristics of the class "Sarcopterygii"?
- Lobe-finned fish (fin muscles are on the fin itself)
- 3 Orders with 7 species (6 lungfish, 1 coelacanth)
- Survivors of once abundant Devonian group
- Heavy enamel scales
57
What are the characteristics of Lungfish?
- Subclass Dipnoi
- Well represented in fossil record
- 6 extant species (1 Australian, 1 South American, 4 African)
- Freshwater
- Aestivation (hibernation to avoid heat/dry conditions)
- Construction of mud and slime cocoon
- Physiological changes (breathe air, lower heart rate, retain urea, metabolise body tissue, weight loss)
- Last up to 8 months
58
What are the characteristics of Coelacanths?
- sarcopterygii (class)
- Peaked during mesozoic era
- Well known from fossil record
- 1 species (Latimeria Chalumnae)
59
What is the shared trait and different trait of the Sarcopterygii and Actinopterygii?
Shared:
- Bony fish (Teleostomi/Osteicthyes)
Non-shared:
- Fins (Sarcop is lobe finned fish, Actinop is ray finned fish)
60
What are some general sensory systems of fish?
- Vision
- Mechanoreception (hearing, lateral line)
- Chemoreception (smell, taste)
- Electroreception
61
How is vision used in fish?
Used for:
- Predator recognition
- Individual recognition
- Schooling
- Sexual selection
Eyes are well adapted to the environment
62
What are the characteristics of fish eyes?
- Similar to other vertebrates
- Light passes through cornea (thinner, no focal action)
- Iris controls amount of light entering the eye (Elasmobranchs can adjust the iris, teleost's cannot)
- Lens focuses images into retina (fish moves lens back and forth, terrestrial vertebrates change the curvature)
- Choroid region (highly vascularised area behind the retina)
- Tapetum lucidum reflects light back and gives a second chance to catch any beams of light that are going in through the front of the eyeball (reflective guanine crystals, holocephali, elasmobranch, coelacanth, some teleosts)
63
What are four problems fish need to deal with in terms of vision?
- Reflection
- Refraction
- Absorption
- Diffraction
64
How do fish adapt to the problems with vision in water?
aerial vision which can be seen in the mudskipper
Four-eyed fish
65
Why do we think Archerfish can account for refraction?
Can spit water at prey and knock it down in to the water. Can also jump out of water and catch prey.
66
What is Attenuation?
- Light penetration in water
- Short wavelengths travel further (red disappears by 5 metres, the yellow, then blue and green penetrate to the greatest depth)
- In coastal waters the photic zone may be as little as 15m
67
What are the basic fish characteristics of light sensing cells and light intensities?
Rods for low light intensities. Cones are for higher light intensities (red=600nm, green=530nm, blue=460nm, UV=380nm)
Cell type correlates with habitat. Nocturnal and deep sea fish may have only rods. Shallow water fish normally have red, blue and green cones to cover the wide range of wavelengths. Fish at intermediate depths have blue and green cones.
68
What are the characteristics of deep sea fish?
Mesopelagic fish:
- Live in an environment with a very low light level
- Large eyes maximise any available light
- Looking for bioluminescent flashes
Bathypelagic fish:
- Live in a totally dark environment
- Trend for reduction in eye size
69
What is Bioluminescence in the sense of fish?
Nearly all deep sea fish have blue bioluminescence - blue light travels much further than red light.
Bioluminescence can be used to counter shade (top half dark, bottom half light
The dragonfish has blue and red light
No other deep sea fish have red receptive rods (sneak up on potential prey, send signals without attracting predators)
70
How is hearing and sound used in fish?
Used for: courtship, foraging and parental care
Sound carries much further in water than in air, fish only hear low frequency sounds (below 3kHz). Involves the inner ear and the swim bladder (inner ear attached to swim bladder and swimbladder acts as a big drum).
Fish sounds can be classified by how they are made:
- Stridulatory sounds
- Hydrodynamic sounds
- Swimbladder sounds
71
What are stridulation sounds?
Made by rubbing parts of the body together, usually grinding teeth or scraping spines
- Grinding teeth (grunts)
- Scrape spines (catfish)
72
What are hydrodynamic sounds?
Caused by rapid water displacement. Analogous to the rush of a passing vehicle. Common in schooling species.
73
What are swimbladder sounds?
Vibration of muscles attached to the swim bladder. Rapid release of air from the oesophagus. Helps to amplify other sounds (grinding of pharyngeal teeth).
74
What are Lateral lines?
Vibration detection system (Neuromasts). Luttle holes which allow interconnectivity between the outside water and the inside of the fish. Neuromasts are used to detect the direction of movement.
Used for:
- Orientation
- Prey detection (blind cave fish)
- Predator assessment (inspection)
- Schooling
- Absent in Myxini
- Found in Lampreys and all extant Osteichthyes and Chondrichthyes
- Found on the trunk and the head
- Position of pores useful to distinguish similar species
- "Feeling at a distance"
75
How to fish use Chemoreception?
- Olfaction (smell) and Gustation (taste)
- Often extremely sensitive
- Distinction between olfaction and gustation less clear than in terrestrial vertebrates
Used for:
- Migration and homing
- Alarm signal
- Kin recognition
- Sex pheromone
- Finding food
76
What are the nasal sacs in fish?
Agnathans have 1 naris, Gnathostomes have 2 nares.
Teleost, lamprey and elasmobranch nasal sacs are blind-ended
Hagfish, chimaeras and lungfish have nares that connect to the pharynx or oral cavity (breathing)
The more folds in the olfactory epithelium the better the sense of smell
77
What are the taste buds like in fish?
Receptor organs of the gustatory system. Found in the mouth and pharynx.
Teleost's also have taste buds on barbels and fins
Some catfish have taste buds over the whole body.
78
What are the two types of use of electricity in fish?
- Electroreceptive fish
| - Electrogenic fish
79
What are electroreceptive fish?
Can detect electric fields which are created by all living things (e.g. sharks, paddlefish, sturgeon can detect these)
Ampullae of Lorenzini are the openings into the electro receptive cells
prey location
navigation - nocturnal - turbidity
sexual selection
80
What is the subclass "Chondrostei"?
- "Primitive" bony fish
- 2 Orders
- Polypteryformes (Birchirs and Reedfish, 10 species all confined to West African swamps)
- Acipenseriforms (Sturgeon - 23 species, Largest FW fish, Paddlefish 2 species)
81
What is the subclass Neopterygii?
- Major group of ray finned fish appear during the late Permian
- Radiated during Mesozoic era and increased in species richness
- 3 Groups (Semionotiformes - Gars, Amiiforms - Bowfin, and Teleostei (modern bony fish)
82
What are the characteristics of Gars (Semionotiformes)?
- 7 species in North and Central America
- FW piscivorous predator
- Breathes air using swim bladder
- Ossified skeletons
83
What are the characteristics of Bowfins (Amiiformes)?
- 1 species in Eastern North America
- Breathes air using swim bladder
- FW omnivore (eats everything up to small mammals)
- Peg-like teeth
- Elongate dorsal fin
84
What are the characteristics of Teleosteii?
- Modern bony fish
- 4 major radiations (Osteoglossiformes, Elopiformes, Clupeiformes, Euteleostei)
- ~25,000 species
85
What are the reasons for telestean success?
- Reduction in bony elements therefore lighter and less energetically costly (fusion or loss of bones)
- Shift in the position of the dorsal fin (split into 2 sections, Anterior hardened spiny section and Posterior flexible section)
- Placement and function of paired fins
- Swim bladder modification (finer control of buoynancy)
- Feeding apparatus modification (pharyngeal teeth - crushing and grinding)
86
What are the characteristics of the subdivision Osteoglossomorpha?
- Bony tongues
- Considered the most primitive telesots
- 6 families with 217 species
- Tropical freshwater
- Found in all continents except Antarctica and Europe
- Knifefish and elephantfish
87
What are the characteristics of Elopomorpha?
- 24 families with 801 species
- Diverse group (united by long lived leptocephalus larvae
- Metamorphosis to juvenile stage
- Marine and freshwater (migratory)
- Ladyfish, European eel and Tarpon
88
What are the characteristics of the subdivision Clupeomorpha?
- 5 families with~357 species
- Some of the worlds most abundant and commercially important fish
- More advanced jaw structures
- Herring and Anchovy
89
What are the characteristics of the subdivision Euteleostei?
- This is the largest and most diverse subdivision with over 22,000 species
- Milkfishes and pufferfish
90
What is reproduction like for fish?
- Incredible range of reproductive strategies
- Most species are dioecious and have external fertilisation and external development, however there are a lot of alternatives
91
What is sperm competition like in fish?
"Sperm competition is the competition between the ejaculates of different males for the fertilisation of a given set of ova" - Parker 1970
High sperm competition in herring and low sperm competition in seahorses
92
What are the 4 levels of parental care in fish?
- No care
- Defence of eggs
- Care of eggs in body cavity
- Giving birth to live young/care of fertilised eggs in reproductive tract
93
Why do fish invest parental care?
Increases the chances of offspring survival. However is energetically costly (decreases parents fecundity)
Takes many forms:
- Behavioural (brood hiding and nest guarding)
- Physiological (internal development)
94
How do fish display no parental care?
- Eggs are fertilised and abandoned
- Oviparous
- Mass spawning events (herring spawn randomly, male Cod have territories within school)
- Massive number of eggs released, however very high egg losses
95
How do fish display defence of eggs in parental eggs?
- Nest building
- Chasing predators of eggs or fry
- Fanning of eggs to provide oxygen and remove waste
- Prevention of desiccation
- Cleaning of the eggs
- Covering the eggs with algae
96
How do fish display care of the eggs in their body in parental care?
- Can have the eggs anywhere in the body but not the reproductive system
- Mouthbrooders (most common place to keep eggs). found in 6 families - Cichlids, jawfish, marine catfish, gourami's. Most often male that broods the eggs. Some cichlids allow the young back in the mouth after hatching.
- Seahorses and Pipefish
97
How do fish display giving birth to live young in parental care?
- Ovo-viviparity
- Viviparity
- Requires internal fertilisation
- over 50% of elasmobranch, less than 0.1% of teleosts
98
What is Ovo-viviparity in fish?
- eggs are fertilised internally
- young develop inside the female
- depend upon yolk for development
- female provides no extra nourishment
99
What is viviparity in fish?
- eggs are fertilised internally
- young develop inside the female
- female provides extra nutrition (placenta, ovarian secretions, extra eggs or embryos)
- ~100 species (Coelacanth, Guppies, All rays, sand tiger shark)
100
What is internal fertilisation like in fish?
Most fish are external fertilisers
Internal fertilisers need some form of intromittent organ (claspers in sharks and gonopodium in guppies) `
101
What is Parker's Lottery Model?
Geoff Parker worked on sperm competition in yellow dung flies - idea is that the more tickets you have in the lottery, the higher your chance of winning.
The model assumes that the sperm from the two ejaculates mix in the spermetheca.
102
What is a tetrapod?
Vertebrate with four weight bearing limbs
Four limbs with single bone in proximal position (close to the body) and two bones in distal (further away)
Doesn't have to mean a primarily terrestrial animal
103
What groups are possible for the tetrapod's to come from?
Sarcopterygians - lobe finned fishes
Extant:
- lung fish dipnoans
- coelacanths
Extinct:
- Rhizodonts 7m long
- Osteolepiformes
- Elpistostegids
104
What are the characteristics which make lungfish a good example of where tetrapods came from?
- Possess simple lungs and modified fins
- Heart partly divided into left and right half as in true land vertebrates
- Vomeronasal system (VNS)
105
What are the characteristics which make lungfish a bad example of where tetrapods came from?
- Limb structure (dont have radius, ulna, humerus, wrist, or fingers)
- Lack teeth in margins of the skull (found in first amphibians)
106
What are good and bad reasons for why coelacanths could be the group tetrapods came from?
- Have an air sac (well in Latimeria fat filled)
- Alternate tetrapod-like limb movements
- But no maxillary bones!
NOPE
107
What are good and bad reasons for why rhizodonts could be the group tetrapods came from?
- Hint of digits
- fangs
However
- Teeth are curved
- Shoulder girdle is different
- Up to 7m long
NOPE
108
What are good reasons for why osteolepiformes could be the group tetrapods came from?
- Structure of the limb-like fin
- Structure of their teeth
- Dermal bones (head)
- Maxillery bones
- Found in Scotland
109
What are good reasons for why elpistostegids could be the group tetrapods came from?
- elpistostegid is similar to a subgroup of osteolepiforms
- Like osteolepiformes but also have pelvic bones like a tetrapod
- Dermal bones matched those of first tetrapods
- Presence of Labrythodont tooth. Found in only two groups of vertebrates: lobe-finned fish and early amphibians (complex foldings of the pulp cavity wall)
YES we think
110
What is another feature that suggests affinities of the tetrapods to the lobe fins in general?
Cosmoid scale - layed scale with bones, spongy bone, cosmine (enamel like substance), vitro-dentine on top (N.B. Lost in extant coelacanths and lungfishes)
Tetrapods have a similar structure but it has become more bony
111
When did the first tetrapods evolve?
- Bona fide tetrapods at 375 mya
- Ambiguous material before that
- "Modern" amphibian ancestors ~250 mya
- However trackways found ~390 mya??
- Late Devonian - first tetrapod appears (Eifelian)
112
How do we know time scales of fossils?
Relative position of sediments - conodonts
Radioisotope absolute dating of igneous rocks
113
Were tetrapods marine or freshwater?
Fossils mainly freshwater. Only one wholly marine Permian "amphibian" known. Only one genus of modern amphibians "marine".
But some more recent specimens come from presumed brackish tidal areas. Lungfishes and coelacanths known from marine environments. Also how did they disperse? There could be big tidal ranges in the Devonian.
Many tetrapods use urea to get rid of their nitrogenous waste - marine exaption?
New fossil footprints found in a marine sediment. Parmastega is marine.
114
How and why did a terrestrial tetrapod evolve from an aquatic ancestor?
Honest answer: we will never know for sure
Devonian environment and habitat of tetrapods ancestors.
Key Innovations in these ancestors
Advantages of a terrestrial lifestyle driving evolution.
Recent evidence suggests early tetrapods came from a Euryhaline environment
115
What was the Devonian environment like?
- Warm and wet climate
- Numerous warm, shallow swamps
- Very high diversity of fish
- Plants colonizing terrestrial habitats
Diversity of terrestrial insects
O2 high
2018 - discovery of tetrapod's in Devonian Antarctic circle
116
What traits of ancestral tetrapods could have led to a terrestrial colonization?
Key Innovations in osteolepiform and related fishes:
- Well-developed limbs, moving through shallows and propping-up out of water
- Lungs, oxygen availability in swamp habitats. Choana (connection between external nostril and buccal cavity)
117
Why did tetrapods move onto land?
THEORY 1
An early theory: the drying pond (A.S. Romer)
- Devonian may have been a period of seasonal droughts
- Evaporating ponds may have stranded animals
- Crawling over land to other water sources
- Devonian not necessarily that arid
THEORY 2
take advantage of greater oxygen availability (unlikely 'cos there wasn't that much extra oxygen until later)
THEORY 3
Take advantage of better food availability
THEORY 4
Reduced predation
THEORY 5
Burrowing in mud
THEORY 6
Increase in body temp
allows more rapid digestion
Speeds development
THEORY 7 - NEWISH
Woodland hypothesis
- Early tetrapods evolved in marine/lagoonal environments, with preference for non-calcarous soils... later they expanded into wet woodlands also with non-calcareous soils. These don't preserve very well hence Romers Gap.
- Not really a functional explanation
118
What are characteristics of early tetrapods?
- Obtaining oxygen from air (greater reliance on lungs (presumably), active pumping
- Gill arches and muscles supporting them reduced. But hyoid used for buccal pumping (initially).
- Reduced muscles used to get tongue to move
- Ribs for exhalation
- Flat heads (indication of shallow water)
- Dehydration modifications in epidermis
119
What are the effects of gravity on locomotion of tetrapods?
Locomotion:
- Air less dense than water. Thus, need to support body against gravity
- Vertebral column becomes a sturdier arch with vertebrae delevoping stronger interlinkages (zygopophyses). More insertion points for muscles.
- Limb girdles become supportive (pelvic by direct connection to vertebral column and pectoral by strong muscular sling connected to skin and trunk). Pectoral girdle distinct from skull. Animals had the beginning of necks.
- Ribs enlarged to make torso more rigid.
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Other changes:
Fishy hyomandibular (used to support jaw and open operculum) bone becomes the stapes stuck to brain case (useless but later becomes one of the bones of the inner ear)
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How many fingers/toes did tetrapods have?
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Hindlimb of ichthyostega 7
Acanthostega forelimb 8, hindlimb probably 8
Tulerpeton from russia 6 fingers
Strange numbers in other fossils
Fixing at 5 come slater
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121
Why fix at 5 fingers/toes for tetrapods?
- Fluke
| - Or is this number a compromise to make wrist and ankle joints stable and flexible enough to walk on land
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What is Romers Gap?
Worlwide gap in the fossil record of 15-20 million years in lower carboniferous (mississippian)
- Dearth of fossils because of an end devonian extinction?
- Lack of oxygen?
- Lack of sampling localities
- Now being filled by discoveries some in scotland
123
What are groups of early amphibians?
- Taxonomy in flux. Paleozoic ones often called labyrinthodonts
- Traditional story - two groups temnospondyls and lepospondyls
nowadays its unsure
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What are Crassigyrinus?
- Secondarily, Aquatic 2m giant predatorial aquatic beast from scotland
125
What are Temnospodyls?
- Main carboniferous tetrapod's
- extinct group of labyrinthodont amphibians
- survived for ~150my to Cretaceous
- Prinosuchus (9m long amphibian from permian of brazil)
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What are Lepospondyls?
Aistopoda: snake like amphibians Carboniferous to Permian
N.B. Not all Lepospondyls were snake-like
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What are Lepospondyls?
Aistopoda: snake like amphibians Carboniferous to Permian
N.B. Not all Lepospondyls were snake-like
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what are Lissamphibia?
Modern amphibians
Monophylectic or polyphylectic?
Arguments for monophyly from Lepospondyls. Some late 1990's quantitative analyses supported this
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Polyphylectic arguments:
frogs and toads come from temnospondyls
BUT
Salamanders and caecilians come from the lepospondyls because they have husk like vertebrae (probably untrue)
OR
All three groups have separate origins
OR
Frogs and Salamanders arose from the temnospondyls and caecilians arose from the lepospondyls.
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Arguments for monophyly from Temnospondyls:
They share;
- Skull without internasal bone
- Possession of pedicellate teeth like some (juvenile) temnospodyls
-Small apical fossa with the vomers that meets the premaxillae
- Infraorbital canal looped over lacrimal bones
In summary: No consensus but frogs and salamanders are closely related... :/
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What are some amphibian characteristics?
1. Pentadactyl limbs: with associated modifications to girdles, ribs, and vertebrae (can be secondarily lost).
2. Hyomandibular bone modified as stapes, forming ear ossicle (other things have this)
3. Urinary bladder present (other things have this)
4. Heart three chambered (divided auricles, single ventricle) and with conus arteriosus
5. Fat bodies in their gonads (reptiles have these)
Amphibian defining features (relative to fish):
6. Loss of fin rays
7. Loss of operculum
8. Loss or great reduction of dermal scales
9. Loss of external gills and lateral lines, EXCEPT in some predominantly aquatic forms
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What are defining features that are unique amongst extant verts?
1. Pedicellate teeth (crown with sheath where new crown grows, secondary loss ahs occurred, some occur in some temnospondyls)
2. Operculum-plectrum complex (the ear system of amphibains. Plectrum (or columnella) derived from the hyoid arch of fishes).
3. Papilla amphibiorum region in the ear for hearing sounds at less than 1000HZ
4. Salamanders and anurans have specialised green rods in eyes. Caecilians dont have them
5. structure of lavator bulbi muscle: this is a thin muscle in the floor of the orbit innervated by the 5th cranial nerve, that causes the eye to bulge outward and to enlarge the buccal cavity. There is also a retrator bulbi muscle
6. Cutaneous repiration
7. Glandular skin
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What are amphibians?
The class Amphibia contains around 8431 living species with new ones being discovered all the time
767 salamanders - order caudata
7449 frogs and toads - order anura
215 caecilians - order gymnophiona
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What are Albanerpetontids?
4th group of lissamphibia (went extinct in the Pleistocene)
First appear in the Jurassic
Amphibian chameleon like animals
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What are the characteristics of frogs and toads (anurans)?
Tail-less (except for larvae), usually long hindlegs, webbed and unclawed toes and smooth or warty glandular skin
Size range goes from 1cm to over 30cm
Worldwide distribution except for polar regions
21 anuran families
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What is the frog skeleton like?
Built for jumping
- Stiff vertebral column
- Hind-legs elongated
- Attached muscles are fast and powerful
- Solid urostyle
- Pelvis fastened to vertebral column
- Fusion of tibia and fibula (reason thought to be because of the amount of pressure caused by jumping)
- 4 digits in their hands and 5 in their feet
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What is the Anuran evolution (frogs and toads)?
Triadobatrachus massinoti from the Triassic of Madagascar 250mya. In Triadobatrachus the radius and ulna (bones of the forearm) were not fused to each other; niether were the tibia and fibula
Features that clearly link Triadobatrachus to frogs:
1. an anteriorly directed ilium
2. reduction in number of presacral vertebrae (to 14)
3. fusion of the frontal and parietal into a frontoparietal bone
4. toothless dentary bone in the lower jaw
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What were the earliest true frogs?
- Prosaliris bitus
| - from the early Jurassic (188-213 my)
136
What are salamanders (urodela or caudata)?
Superficially resemble lizards in form but have glandular skin, smooth and roughened with tubercle, lack true claws and tail this is laterally flattened
Size range is fro 4cm to over 1.5m
Mostly found throughout the northern hemisphere
10 extant families (Abystomatidae, sirenidae, cryptobranchidae)
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What was the evolution of salamanders?
salamanders appear in the Jurassic in North America and Eurasia
Extant forms also in North America and Eurasia with one family in South America
Presumably the radiation of salamanders occurred in Laurasia and the invasion of South America was a late event (evidence suggests Miocene invasion)
138
What are the Caecilias?
Limbless and worm-like or snake-like and very short tail.
Skin has minute imbedded bony dermal scales, lidless eyes covered by skin (and bone in some species).
Eyes are reduced or simple in structure. Most burrow in damp soil or decayed wood, while some are aquatic. Fertilisation is internal
Varied reproduction tactics evident between species:
1. Eggs developing into free larvae
2. Direct development
3. Viviparous
139
How did Caecilians evolve?
Chinlestegophis jenkinsi Triassic North America
- Legged caecilians Eocaecilia micropodia
- More modern forms from the upper cretaceous of bolivia and the paleocene of brazil.
140
What are the characteristics of amphibian development?
Most amphibians require an aquatic habitat to reproduce.
The amphibious mode of life (movement from terrestrial sites to aquatic environment to breed) is presumed to be the ancestral pattern.
Eggs deposited in water, hatch into free-swimming larvae (tadpoles) and then later metamorphose into land stage.
141
What is respiration like in aquatic larvae of amphibians?
Respiration occurs across the skin and gills of aquatic amphibian larvae.
142
What is amphibian skin like?
Water relations and respiration can be carried out across the highly permeable amphibian skin. Many important features of amphibian skin:
- Protects against abrasions and pathogens
- Absorbs and releases water
- Helps control body temperature through secretions and colour change
- Poisons in skin help protect against predators
- Skin colour important to deter predators
- Provides some desert species with a water-loss resistance protective cocoon.
Potential problem: desiccation
143
What is the structure of amphibian skin?
Amphibian skin can contain many cell types and structures, including pigment cells, mucous, poison glands, blood vessels and nerves in connective tissue matrix
144
What are poisons in amphibian skin?
Poison glands found over the entire body of bufo species (toads) is used as a defence against predators.
145
What are water relations of amphibians?
Problems with amphibian skin is dehydration:
- dry skin reduces permeability to water and gas
- reduces oxygen uptake across skin and ability to use evaporative cooling to maintain body temperature
Amphibian possess several tricks to keep hydrated
- amphibian kidney and bladder
- pelvic patch
- absorption of water from relatively dry soil (e.g. desert frogs)
- behavioural strategy avoid dry conditions (aestivation)
146
What are the characteristics of amphibian kidney and bladder?
Amphibian kidneys produce a urine hypo-osmotic to blood
- which means the urine is dilute
- water can be reabsorbed from the bladder
- terrestrial species have larger bladders for water storage
147
What is the pelvic patch in amphibians?
Highly vascularised skin in pelvic region responsible for large part of amphibians water absorption across skin
In deserts, species can absorb water from soil during aestivation.
148
How do frogs use calling to attract mates?
Song is used by male frogs to advertise to and attract potential mates and establish territories. It is a very important characteristic used by females to select males for copulation.
149
What is the Amplexus in frogs?
amplexus is the mating position
During mating in frogs, males grab hold of the females (amplexus) with their powerful fore-arms and release their gametes over the eggs as they are released.
Males of some species develop huge powerful fore-arms and nuptial pads during the breeding season.
150
How do some newts use courting to attract mates?
Males of several newt species use ritualised courting displays to encourage the females to copulate with them. They deposit a spermatophore on the substrate and if they are successful the female will suck it up into their urino-genital duct.
151
What are different amphibian reproductive strategies?
Salamanders - Internal fertilisation
Caecilians - Internal fertilisation (90%), little known about courting and mate attraction
Frogs - External fertilisation
- Most lay unprotected mass of jellied eggs - jelly swells with water and helps to protect them
But they are a favourite food of insects, fish, wading birds
Parental care has evolved independently in all 3 groups
152
What is parental care like in amphibians?
Egg tending has evolved independently in caecilians, salamanders, and anurans. The attending parent may contribute to several of the eggs in several ways.
1. Guarding against predation
2. Reducing desiccation threat by coiling around them and coating the eggs with skin secretion or by urinating on them
Eggs of Assa darlingtoni are deposited on moist soil and guarded by the males. After 11 days, the eggs hatch and the tadpoles swim into one of the two hip pockets of the males, where they remain until metamorphosis.
Tiny Darwin frog of chile and argentina broods young in their vocal sac. The eggs are laid on land and develop for the first 10-20 days on moist ground. Attending males then engulf their eggs in their enlarged vocal sacs until the young (5-15) metamorphose.
Some frogs feed their young. Some frogs have pouch brooding.
153
Leglessness has evolved many times in which tetrapods?
- Aistopodes
- Microsaurs
- Aphiumid salamanders
- Caecilians
- Snakes
- Slow-worms and other legless lizards
154
What is an amniote?
Includes all reptiles, dinosaurs, mammals, and birds
Refers to unique structure of their egg (or derived from these structures i.e. mammalian placenta)
Amniotic egg possesses three extraembryonic membranes
155
What is the Amniote egg?
The embryos of reptiles, birds, and mammals form three (major) extraembryonic membranes: the amnion, allantois, and chorion.
The amnion protects the embryo in a fluid-filled cavity that prevents dehydration and cushions mechanical shocks.
156
When did first amniotes evolve?
Anthracosaurs (lineage probably leading to reptiles) arose early Carboniferous.
Earliest amniote fossil derives from the late Carboniferous period about 300 mya.
Rare in Carboniferous period about 300 mya
"Modern" reptile lineages arose between 100-300 mya
157
What are the closest ancestors of amniotes?
Amniotic membranes dont fossilize, so skeletal features are used to decide which fossils are amniotes. These include:
- loss of labyrinthodont teeth
- several features of the skull that reflect more complex jaw musculature
- stronger rib-cage, with costal muscles for breathing
- presence of an astragalus
- are the fossils part of known seperate lineages which were definitely amniotes (assumes amniotic egg evolved once)
- egg fossils known from Triassic
158
What was Seymouria?
A reptile-like amphibian
Fully terrestrial anamniote found early Permian
- Initial confusion over whether seymouria is reptile or amphibian
- lacks some of the key features of early amniotes (plus fossil larvae with gills found)
- considered transitional form of amphibian to reptile
159
What was Diadectomorpha?
closest ancestors of amniotes
Complex jaw musculature
Intervertebral articulations
Reptile-like amphibian from the late Carboniferous period
Highly specialised teeth for grinding food
All fossils have shown extensive tooth wear - grinding
Unusually for an early tetrapod, diadectes was a herbivore
160
What are stem-reptiles?
Possessed scales and reptilian limbs and girdle
Skull long, high and with large orbits
Pointed nose, probably insectivore
161
How did these close ancestors to amniotes become more terrestrial?
1. Structure of the skin - must be more waterproof
2. More efficient lungs - reduced aquatic and cutaneous respiration, elastic lung hydraulically sealed to ribcage
3. Reduce reliance on water for breeding
4. Amniotic egg
162
What are advantages of waterproof skin?
1. Survive drier habitats (radiate into new niches for tetrapods
2. Dont need to frequently return to water
3. Allows basking in sun and behavioural thermoregulation
163
What is behavioural thermoregulation?
Regulation of body temperature by shuttling between sun and shade
Water-proof scales of reptiles allow maintenance of high body temperatures without dehydration
164
How is reliance reduced on water for breeding?
1. Internal fertilisation - chambers in female and penis in male
2. Water-proof self contained egg (amniotic egg)
165
What are the three lineages that separated the amniotes in the late Carboniferous?
Three linages distinguished on the basis of their skull structure, in particular the temporal fenestrae behind the orbits.
- Anapsid
- Diapsid
- Synapsid
166
What is the function of temporal fenestrae?
Temporal fenestrae are large holes in the side of the skull. The function of these holes has been strongly debated for many decades. Several theories:
1. Support greater jaw musculature and allow an increased gape
2. Lighten the overall mass of the skull for greater mobility
3. Conserve the extra calcium that would be required for the bone
167
What occurred at the Permian radiation?
Decrease in diversity of amphibians BUT major radiation of reptiles throughout the Permian
Major reptiles filling niches previously occupied by amphibians
Permian climate was dryer and hotter
168
What were the dominant group in the Permian?
Synapsids.
Major radiation in Permian and Triassic
Led to mammals
169
What were the Paleozoic Synapsids?
First synapsids occur in the Upper Carboniferous (Pennsylvanian). Lizard like with identical teeth except for the presence of canines in some species.
Major radiation in the Permian: the pelycosaurs (mostly but not all sail backed).
170
What are anapsida?
Ancestral condition nice solid skulls
| Extinct ones pariesaurs (could include the first truly erect tetrapod 260mya
171
What are Caroniferous Diapsids?
Carboniferous diapsids known only from two genera from Kansas Petrolacosaurus Spinoaequalis
Low diversity in lower Permian but in upper Permian bit of a radiation
172
What are the two major lineages appear from ...?
- archosauromorpha (semi-erect later sometimes erect)
| - lepidosauromorpha (semi-erect or sprawlers)
173
What was the Great Permian Extinction?
Retiles were very diverse in Permian but at the end of the Permian approx 248 mya greatest extinction event in recorded history
90-95% marine species extinct
48 tetrapod families in last 5 mya of Permian - 36 of these went extinct (approx 75%)
174
What were the Diapsids like in the Triassic?
Lepidosauromorpha - Not very important in Trassic apart from marine euryapsids (possibly have origins here)
Archosauromorpha - Rhynchosaurs dominant diapsid animals of lower Triassic
- Archosaurs including Crurotarsi, ornithodirans and some other things
175
What was the rise of the archosaurs?
Archosaurs "ruling reptiles" of the mesozoic evolved from more primative reptiles in the latest Permian.
Archosaurs showed dramatic changes in posture, becoming more erect. Many held body off ground when running
176
When was the divergence of the archosaurs?
Mid-Triassic period the Archosaurs seperated into two main groups
One lineage off to the crocodiles and one towards dinosaurs and birds
The two lineages possessed strikingly different ankle anatomies
177
What are Pterosaurs?
Archosaurs gave rise to two independent radiations of fliers - the birds and the pterosaurs (winged-animals)
- range from sparrow-sized to 13m
Many modifications to lighten skeletal structure (e.g. the pteroid supports the anterior flight membrane
178
What where the early dinosauria?
Oldest dinosaurs described from the earliest stages of the triassic approx 230-225 mya.
Dramatic radiation during last 20 mya of Triassic dinosaurs are primitively bipedal
179
When was the divergence in early dinosaurs?
The two lineages can be seperated on the basis of the structure of their hips;
- the "reptile-hipped" Saurischia (sauropods and theropods)
- the "bird-hipped" Ornithischia
180
What are the Saurischian Dinosaurs?
Theropods
Lineage that led to the birds. Three major ecological general types of Theropods:
1. Large predators
2. Fast-moving predators that attacked small prey
3. Fast-moving predators that attacked prey larger than themselves
e.g. Tyrannosaurus, Baryonix
181
What were ornithischian dinosaurs?
Diverse group of herbivorous dinosaurs prevalent in the Jurassic and Cretaceous period.
e.g. Stegosaurus
182
What are features of all dinosaurs?
Primitively bipedal
Erect
Feathered?
183
How do we predict dinosaur behaviour?
Footprints - mode of walking, socialisation, predator-prey relationships
Nests found Maiasaura in Montana, colonial breeders
184
What was dinosaur metabolism like?
Endothermic versus Ectothermic physiology
Several lines of support for the non-avian dinosauria being endothermic:
- Dinosaurs found at high latitudes
- Erect gait and could run at high speed (up to 60 km/hr)
- Dinosaurs have more similar bone structure to birds and mammals than other ectotherms
- Theropods were feathery possibly other ones were as well
- Carbonate clumped isotope paleothermometry: bodies were warm
185
What were dinosaur bone and growth rates like?
From analyses of dinosaur bone structure it appears that has very high growth rates, as fast as mammals and birds.
186
What were dinosaurs predator - prey ratios like?
Dinosaurs had low predator to prey ratios that are similar to mammals which further supports dinosaurs being endothermic.
187
What adaptions to birds have for thermoregulation?
- Lack sweat glands as evaporation wouldn't work due to feathers and sweat would also impair feather function.
- In order to regulate their heat birds will have behavioural thermoregulation by standing in shade or standing in the sun, panting, huddling together etc.
- Birds also have efficient heat exchange system in their feet.
188
Why is breeding and moulting not done at the same time for birds?
Both energetically expensive (moult ~15% and breeding 50% more extensive) therefore are done at different times
