Vert Bio Flashcards
past this bs exam (194 cards)
1
Q
Define systematics
A
the study of biological diversity using phylogeny
2
Q
Define taxonomy
A
the description, identification and classification of spp
3
Q
Define nomenclature
A
the standardised system of naming taxa
4
Q
Define classification
A
the arrangement and hierarchy of taxa (Kingdom, Phylum, Class etc…)
5
Q
Define phylogenetic systematics/cladistics
A
the shared derived character states constitutes evidence that the spp possessing these features share a common ancestry
6
Q
Define monophyletic groups
A
groups of taxa that consist of a common ancestor plus all descendants of that ancestor
7
Q
Define paraphyletic and polyphyletic groups
A
include a common ancestor and some, but not all, descendants of that ancestor (eg. recent molecular evidence data supports river dolphins as a polyphyletic group as Indian river dolphins do not share the smae common ancestor as other river dolphins)
8
Q
Purpose of phylogenetic tree
A
- other name being cladogram
- shows relatedness of animals
9
Q
What are common features of chordates?
A
- bilateral symmetry
- notochord: dorsal rod of specialised cells
- dorsal nerve chord: hollow tube just above the notochord
- pharyngeal pouches: gill slits
10
Q
What are the three subphyla of chordates?
A
- Urochordata (eg. tunicates)
- Cephalochordata (eg. lancelets)
- Vertebrata
11
Q
Why are vertebrates used as a model for studying evolution?
A
- monophyletic group
- free living
- basic anatomy and development in common
- diversity of form and function can be related to adaptation and evolution
- best-studied eukaryotic group
- good fossil record
12
Q
What are the modern (extant) lower vertebrates?
A
- Myxinoidea & Petromyzontoidea (jawless fish)
> hagfishes and lampreys - Elasmobranchii & Holocephali (cartilaginous fish)
> sharks, rays, skates and ratfishes - Actinopterygii (ray-finned fish)
> bichirs, bowfins, gars, sturgeons, teleosts - Sarcopterygii (lobe-finned fish)
> coelacanths and lungfishes - Lissamphibia (amphibians)
> frogs, salamanders, caecilians
13
Q
What are the extant higher vertebrates: amniotes
A
- Testudines > turtles, tortoises, terrapins - Lepidosauria > tuatara, lizards, snakes - Crocodilia > alligators, crocodiles, caymans Aves > birds - Amniotes arose from a tetrapod amphibian ancestor in the late Devonian period (~370mya)
14
Q
What are common features of vertebrates?
A
- vertebrae: series of bones that make up the backbone, protect the spinal chord and act as attachments for muscles
- postnatal tail: for movement in some vertebrates
- pharyngeal pouches in chordates evolved into:
> gill slits in fish and amphibians
> structures in throat and ears in mammals - vertebral column (backbone; developed from notochord)
- specialised sensory organs
- brain at anterior end of nerve chord
- closed-loop circulatory system (heart, arteries, veins and capillaries)
- myomeres (muscle segments)
- vertebrates are craniates ie. they have a head. Origin of head opened up a completely new way of feeding for chordates - active predation
- cranium: outer shell protecting the brain
- skeleton: made up of backbone, skull etc.
15
Q
What ten systems are vertebrate organs organised into?
A
- skeletal - circulatory
- muscular - excretory
- integumentary - immune
- digestive - nervous
- respiratory - reproductive
16
Q
Class - Agnatha (jawless fish): features and facts
A
- originated around 500mya
- two extant groups: lampreys and hangfish (90-100 spp in total)
- features:
> cartilaginous skeleton
> characterised by absence or paired fins
> seven or more paired gill pouches
> no identifiable stomach or any appendages
> fertilisation and development are external
17
Q
Class - Osteichthyes (bony fish): features and facts
A
- originated 500mya, first appeared around 410mya
- bony fish are an extremely diverse and abundant group with ~25,000 (100 new described each year) spp alive of which 60% are marine
- the largest class of vertebrates in existence today, divided into:
> Actinopterygii (ray-finned fish)
> Sarcopterygii (lobe-finned fish) - all bony fish have scales, gills for respiration and are ectotherms, however some members of the family Scombridae (swordfish and tuna) have some level of endothermy
18
Q
Class - Chondrichthys (cartilaginous fish, sharks, rays, skates and ghost sharks): features and facts
A
- first appeared around 420mya
- ~1200 spp: ~500 sharks and ~600 rays and skates
- jawed fish with paired fins, denticles (scales), skeletons made of cartilage not bone
- gills for respiration
- no gas bladder - will sink if they stop swimming
- fertilisation is internal
- development:
> usually through live birth (ovoviviparous spp)
> can be through eggs (oviparous) - two subclasses:
> Elasmobranchii (sharks, rays and skates): upper jaw not fused to braincase, separate gill slit openings (5-7 gillslits)
> Holocephali (chimaeras/ghost sharks): upper jaw fused to braincase, one gill slit with operculum cover (4 pairs of gills)
19
Q
Elasmobranchs - feshwater + skates and rays
A
- almost all are marine, but:
> 43 spp can tolerate brackish or freshwater
> stingrays, sawfishes and the bull sharks are more tolerant than others and can penetrate far up freshwater rives - the bull shark has been recorded 4,200km from the mouth of the Amazon river
> there are a few (~23) spp of South American river stingrays (Potamotrygonidae) that are entirely feshwater - Batoids (skates and rays)
> flat-bodied with pectoral fins developed into broad flat wang-like appendages
> major difference between skates and rays is how they reproduce:
+ rays are viviparous (live bearing)
+ skates are oviparous (egg-laying), eggs in rectangular cases sometimes called ‘mermaids purses’
> skates normally have prominent dorsal fins while rays have reduced or absent fins
20
Q
What are the various Pelagic zones in the ocean?
A
- Epipelagic: 0-200m. Continental shelf. Lots of light, where most organisms are found
- Mesopelagic: 200-1000m. Twilight zone. Little light but enough for phtosynthesis. Together, epipelagic + mesopelagic = Photic zone
- Bethypelagic: 1000-4000m. Pitch black. Deepest recorded Chondrichthyan: great lantern shark
- Abyssopelagic: 4000m-seafloor
- Hadopelagic: Ocean tenches
21
Q
Shark diagram - refer to notes
A
Shark diagram - refer to notes
22
Q
What is the ideal shape for aquatic locomotion
A
- fusiform, length:depth ratio = 4.5 (spindle-like shape that is wide in the middle and tapers at both ends)
- sharks have ratios between 3 and 8, optimum is 3-7
23
Q
What are the purpose of fins?
A
- used for stabilising, steering, lift and propulsion
- one or two dorsal fins = anti-roll stabilising fins, may have spines or skin glands that produce irritating substance for defence
- pectoral fins for steering and lift
- pelvic fins are also stabilisers, so are anal fins (if present)
- tail region = caudle peduncle + caudal fin. Peduncle may be flattened into lateral keels. Caudal fins provide thrust.
24
Q
Tail types?
A
- heterocercal: vertebrae extend into larger lobe, tail is asymmetrical
- homocercal: vertebrae do not extend into lope, tail more or less symmetrical
- epicercal: upper lobe is bigger (sharks)
- hypocercal: lower lobe is bigger (flying fish)
25
Shark skin features?
- rough due to small rough placoid scales called dermal denticles
- denticles consist of bony plate buried in skin and a raised portion that is exposed
- dermal denticles are homologous in structure to teeth
- form a protective barrier and aid in swimming
- the low sharp-edged ridges of the denticles are parallel to the direction of movement and reduce drag by delaying turbulence
26
Shark teeth features?
- not lodged permanently in jaw, instead attached to a membrane called a tooth bed
- tooth bed membrane works like a conveyor belt, teeth move forward as shark grows, replacing damaged, lost or worn teeth infront
- Cookie Cutter sharks (order: Squaliformes; two spp, small: 40-50cm) attach themselves to prey and spin to cut out 'cookie' of flesh
27
How do you determine a sharks age?
- vertebrae examined - growth rings
- spine growth (not uniform, greater areas of growth can indicate year quality/season)
- oldest shark: Greenland shark, 392 +/- 120 years old
28
Why study elasmobranchs
- protect biodiversity
- top predators - indicator spp
- threatened by:
> fisheries (mainly for fins). Last UK Basking shark fishery closed in 1995, protected in UK since 1999
> shark nets
> incidental catch (bycatch) in fisheries
- little information on abundance and status for most spp
- tourism: swimming with basking, whale and great white sharks
29
What factors are used to model growth and survival?
- distribution
- abundance
- population structure
- biology
- mortality
- ecology
- behaviour
- human impact
30
Swimming and buoyancy - Dynamic lift? (shark related)
- fish denser than water will sink - must generate dynamic/static lift
- can create dynamic lift by using their (airplane wing-like) pectoral fins or inclining their bodies at an angle of attack
- they need to move forward to create the lift, but this increases drag, increasing energy expenditure
- may be energetically 'cheaper' to be a bottom-dwelling spp, however most hover just above the sea floor
- degree of dynamic lift decided by size and shape of pectoral fins
31
Swimming and buoyancy - Static lift? (shark related)
- storing light materials creates static lift
- most (bony) fish create static lift with their swimbladder
- sharks don't have a swim bladder, so:
> they use low density cartilage
> low density lipids (fat and oil eg. squalene: 860g/l)
> oil is bulkier than air but is easier to use to regulate buoyancy, Lift provided by oil varies a little with depth as changes in ambient pressure have little effect on volume of oil - more consistent buoyancy
> oil is stored in liver and muscles, but have to trade-off as oil is also a food store for adult and embryo
> sharks regulate oil to balance their weight in water (however exact process not know)
32
Elasmobranch gills
- all sharks have 5-7 paired gills
- gas exchange occurs at gills, oxygenated water must flow over the gills for respiration to occur
- water enters through the mouth (or the spiracle), into the pharynx, over the gills and exits through the gill slits
- respiratory gas exchange takes place on the surface of the gill filaments as the water passes over the gills and out
33
Spiracle
- essentially a first gill slit
- opening behind the eye
- provides oxygenated blood directly to the eye and brain through a separate blood vessel, and/or to pump water through the gills
- absent in many sharks eg. front swimming sharks
- larger in bottom dwelling sharks
- in rays the spiracle is larger and more developed and is used to actively pump water over the gill, allowing the ray to breathe whilst buried in the sand
34
Elasmobranch senses: Ampullae of Lorenzini
- they are small vesicles and pore (electroreceptors), that form part of an extensive subcutaneous sensory network system
- found around the head and appear as dark spots
- each ampullae contains multiple nerve fibres that are enclosed in a gel-filled tubule (glycoprotein with electrical properties) which has a direct opening to the surface through a pore
- the ampullae detect weak magnetic fields produced by other fish
- since all living creatures produce magnetic fields by muscle contraction, sharks may pick up electrical stimuli from their prey
- this allows sharks to detect eg. prey hidden in the sand
- ampullae may also be used to navigate to the electric fields of the ocean currents and earths magnetic field
- (REFER TO DIAGRAM)
35
Elasmobranch senses: Lateral line
- the lateral line along with the ampullae of Lorenzini comprise the electrosensory component of the sharks sensory system
- the lateral line allows the shark to orient to particle movement or sound
- it consists of structures called neuromasts that are located in canals that lie just beneath the surface of the skin or the scales
- similar to the ampullae of Lorenzini there are pores that open to the outside and movement caused by prey can be detected by the neuromasts
- there are also 'Pit organs' - surface neuromasts
- the lateral line canal lies just beneath the lateral line which is open to seawater by tubules connected to the surface by pores, bundles of neuromasts lie in a gelatinous dome which is partially exposed to the lateral line canal
36
Elasmobranch Senses: Hearing
- sharks have a sharp sense of hearing, possibly being able to hear prey many miles away
- a small opening on each side of their heads (not the spiracle) leads directly to the inner ear through a thin canal
- the lateral line shows a similar arrangement, which is open to the environment via a series of openings called lateral line pores
- this a reminder of the common origin of these two vibration- and sound-sensing organs that are grouped together as the acoustico-lateralis system
- in bony fish and tetrapods the external opening to the inner ear has been lost
37
Elasmobranch Senses: Smell and taste
- sharks have sophisticated olfactory senses, located in the short duct between the anterior and posterior nasal openings, with some spp able to detect as little as one part per million of blood in seawater
- sharks are are attracted to the chemicals found in the guts of many spp, and are often found near sewage outfalls
- some spp eg. nurse sharks, have barbels (whisker-like tactile organ near their mouth) that increase their ability to sense prey
38
Why the hammer in hammerhead sharks?
there are two basic thoughts:
- hydrodynamic advantages (head is flattened on lower surface and rounded on upper and therefore may increase lift)
- sensory enhancement:
> nostrils of most spp are located near the tips of the hammer and have specialised grooves which channel scent-bearing water to the nostrils
> by having nostrils mounted far apart they can sample the water column in stereo
> the ampullae of Lorenzini are distributed over the entire under surface of the hammer, and the width of the head may work as a 'metal prey detector'
39
Elasmobranch osmosregulation
- the blood and other tissue of sharks and Chondrichthyes in general is isotonic (same or similar salt concentration) to their marine environment
- due to the high concentration of urea and trimethylamine N-oxide (TMAO), allowing them to be in osmotic balance with the seawater
- this adaptation prevents most sharks from surviving in freshwater
40
Elasmobranch osmoregulation: Bull shark
- the bull shark is an exception to normal osmoregulation, it has developed a way to changes its kidney function to excrete large amounts of urea and allow it to move far up rivers
- despite this reduced solute concentration in freshwater, Lake Nicaragua Bull sharks still have body fluids more than twice as 'salty' as typical freshwater fish
- they must, therefore, experience a massive influx of water. The water influx is almost certainly dealt with by the kidneys, resulting in copious excretion of dilute urine.
- an early measurement of urine production by a freshwater sawfish indicated a daily flow rate of 250ml/kg of body mass - more than 20x that of a normal Elasmobranch
41
Elasmobranch thermoregulation
- most sharks are ectotherms - their internal body temperature matches that of their environment
- members of the family Lamnidae, such as the shortfin mako shark and the great white shark, are endothermic and maintain a higher body temperature than the surrounding water
- in these sharks, a strip of aerobic red muscle located near the centre of the body generates the heat, which the body then retains via a countercurrent exchange mechanism a by system of blood vessels called the rete mirabile
42
Elasmobranch thermoregulation: rete mirabile
- lateral artery carrying blood from heart
- lateral vein coming out carrying warm blood
- they are in close proximity, heat exchange, blood in lateral vein artery up
- core remains warm - more efficient muscles
43
Elasmobranch reproduction example: Porbeagle
- sharks are sexually dimorphic
- males (have):
> pelvic claspers which are modified pelvic fins used for sperm delivery
> claspers are rolls of cartilage that become stiffened with calcium in adults
> paired testes, the right one is more developed than the left, which even be absent
- females (have):
> no claspers but a cloacal opening (as do the males) between the pelvic fins
> paired ovaries, left side is often reduced and releases very few or no eggs
- mating (ex. porbeagle)
> during copulation males meet face to face
> the male inserts one of his claspers into the cloaca of the female
> the spermatosphores are forcefully ejected by contracting organs known as siphon sacs which use seawater to carry the spermatophore
44
How to access data? (samples)
- samples from dead animals (fossils, fisheries catch and bycatch)
- samples from living animals:
> catching live animals
> field work:
+observations (behaviour, ID)
+tagging (mark-recapture, and various radio/acoustic-data tags, tissue samples)
45
Patterns in Elasmobranch distribution
- some spp have very limited distribution eg. northern river shark is a spp of requiem shark found in tidal rivers in northern Australia
- others range across ocean basins (eg. whale, basking, blue, salmon and great white sharks)
46
How to investigate population structure
- morphometrics (some skeleton structure that is selected for and shows measurable differences between non-interbreeding populations)
- genetics and DNA forensics:
> using polymerase chain reaction (PCR) amplification of mitochondrial DNA (mtDNA) and nuclear DNA followed by restriction enzyme analysis to generate a form of DNA fingerprint (for spp, individuals or populations)
> using or a combination of direct sequence comparison and clustering approach to determine similarities between DNA sequences from samples of unknown origin to reference spp (phylogenetic approach)
- ecological: stable isotopes, contaminants and parasites
47
Life history of Elasmobranchs
- shark lifespans vary by species:
> most live to 20 to 30 years
> Greenland shark: 392 years old
- unlike most bony fish, sharks are K-selected reproducers, meaning they produce a small amount of well-developed young as opposed to a large number of poorly developed young
- fecundity in sharks ranges from 2 to over 100 young per reproductive cycle (every 1-3 years)
- sharks mature slowly compared to other fish, eg. lemon sharks reach sexual maturity at around 13-15 years old
- annual rate of increase between (
48
Conservation of Elasmobranchs
- by January 2014, 1041 of all chondrichthyans had been evaluated at a global scale and only 23% of the spp are categorised as being safe, or of "least concerned"
- it is estimated that 40-100 million sharks are killed each year due to commercial and recreational fishing. Sharks are eaten around the world and in many places regarded as a delicacy (eg. fins in China and Japan). Icelanders ferment Greenland sharks to produce hakarl (sharks buried in the ground for months to ferment)
- shark fins is a big business. In 2010, CITES rejected proposals from the US and Palau that would have required countries to strictly regulate trade in several spp of sharks. Majority of delegates (but not the needed 2/3), approved the proposal. China and Japan led the opposition
- 2013: CITES added a variety of sharks to Appendix 2
49
Conservation ecosystem effects: what happens to the ecosystems if large-scale apex predators are removed?
- lack of prey regulation - ecological instability
- ecosystem shift
- possible cascading effects
- loss of important indicator spp on the health of the marine system
50
Actinopterygii - ray-finned fish: Facts and features
- have "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterise the class: lobe-finned sarcopterygii
- actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the 30,000 spp of fish
- they are distributed throughout freshwater and marine environments from the deep sea to the highest mountain streams
- extant spp range in size from 8mm to massive Ocean Sunfish at 2,300kg and the long-bodied oarfish a 11m
51
Teleosts (Actinopterygii): facts and features
- by far the most dominant living fish are the teleosti
- most advanced of all the living bony fishes
- teleosts account for 96% of all living fish
- exhibit the greatest variation in habitat types, body plans, foraging and reproductive habits of any fishes
- first arose around 200mya (early Mesozoic)
- only group to utilise plant material in all its forms
- (can) produce light and electricity
- >24,000 spp (to date)
52
What are otoliths?
- stony concentrations situated in part of the ear system at the base of the brain
- carry a complete record of fish growth as they are deposited gradually throughout life
- shape of large otoliths is spp dependent (diagnostic)
53
Fish scales: Placoid
- primarily for protection
- placoid is comprised of dentine and enamel
- sharks
54
Fish scales: Cosmoid
- probably evolved from fusion of placoid scales
- consist of two layers of bone:
> inner layer of dentine-like cosmine
> outer layer of vitrodentine
55
Fish scales: Ganoid
- usually rhomboid in shape
- have articulating peg and socket joint between them
- modified cosmoid scales
- consists of a bony basal layer, a layer of dentine, and an outer layer of ganoine (an inorganic bone salt)
56
Fish scales: Cycloid/Ctenoid
- in the majority of teleost fish
- ctenoid found in eg. trout and herring
- cycloid found in eg. sole and perch
- two main regions:
> a surface 'bony' layer, comprised of an organic framework impregnated with calcium based salts
> a deeper fibrous layer comprised mainly of collagen
- they grow throughout the fishes life
- they provide a growth record of the fish and may also show spawning
57
Respiration in teleosts
- gills covered by bony plate - operculum
> provides protection
> space between gill and operculum - opercular chamber
- less gills
58
Gas bladder
- gas filled sac located in the dorsal region of the body cavity
- volume can be increased/decreased
- there are two types: physostomous and physoclistous
- in both swimbladders there is a gas gland with a rete mirabile, counter-current multiplier arrangement of capillaries, which allows gas to be trapped in the swimbladder
59
Gas bladder: Physostomous
- more primitive
- connection retained between swim bladder and gut
- allows fish to fill up the swim bladder by "gulping air", gas can be removed similarly
60
Gas bladder: Physoclistous
- connection to the digestive tract is lost
- fish have to either rise to the surface to fill their bladders or introduce gas (usually oxygen) to increase buoyancy (via the bloodstream)
61
Gas secretion in swim bladders
- amount of gas that blood can carry depends on pH
- more pH (alkaline), more oxygen can be stored
- lower pH (acidic), haemoglobin has to give up oxygen, less O2 stored
- counter-current system between closely associated artery and vein:
> CO2 taken up by arterial blood coming in
> CO2 dissociates to carbonic acid
> proteins released which lowers pH
> so oxygen is given up
- swim bladder wall embedded by guanine crystals making it impermeable to gas (so all oxygen lost enters swim bladder)
- rate of secretion can be altered by blood flow (therefore gas flow)
62
Locomotory types
- fish move by a variety of means, simplest are positive drifters
- four types of locomotion, characterised by how much of and what body parts are involved in propulsion
- whether the fins undulate or oscillate (snake vs caterpillar)
63
Anguilliform
- involves sinusoidal undulations
- seen in most eels, dogfish and may fish larvae
- occurs in fish with very flexible bodies
- all but head contributes to propulsion
- as the wave moves more posteriorly it increases in amplitude
- speed (freq) of the wave remains constant - always exceeds speed of forward movement
- faster waves --> faster swimming
- slow because of long bodies and involvement of anterior regions in propulsion
- segments creating push force also waste energy by pushing laterally causing drag
64
Carangiform (sub carangiform)
- only posterior propels to avoid 'self braking'
- use ligaments to transfer force from muscle to tail
- functional hinge: connecting tail to peduncle maintains tail at ideal angle of attack (10-20 degrees) during powerstroke
- advanced thunniform swimmers have originating from narrow peduncle and have lateral keels to create a more streamlines shape - less drag
- within the carangiform swimmers tail deign varies as fish become more advanced (subcarangiform --> thunniform):
> thunniform - high aspect ratio, minimal drag, sustained swimming, stiff
> subcarangiform - low aspect ratio, for rapid acceleration and can aid hovering, tail has intrinsic musculature to help control shape
65
Ostraciform
- only body moves while whole body stays rigid
- contract muscle on one side then the other
- this type of fish relies on armour not speed
- the caudal fin is small and not differentiated into distinct lobes - isocercal
66
Swimming with fins: oscillatory
- tetraodontiforms - flap their dorsal and anal fins synchronously (sunfish)
- labriform - row their pectoral fins, pushing it with the broad blade then feathering it in the recovery phase (parrot fish)
67
Swimming with fins: undulatory
- amiiforms - undulations pass along dorsal fins (seahorses)
| - balistiform - both dorsal and anal fins undulate
68
Colonising the land: obtaining oxygen from the air
- the evolution of lunglike sacs in response to the inadequacy of gills for respiration in the oxygen-poor waters set the stage for the invasion of land
- some bony fishes were able to supplement their gills with lung sacs when oxygen levels were low
- this ability allowed them to breathe air and leave the water temporarily
- the lobe-finned fish (class: sacropterygii) were the first lineage to evolve jointed fins
69
Sarcopterygii - lobe-finned fish: facts and features
- fleshy, lobed, paired fins, joined to the body by a single bone
- the fins differ from other fish - attached on a fleshy, lobe-like, scaly stalk extending from the body
- the scales consisting of dentine-like cosmine and keratin
- pectoral and pelvic fins resemble tetrapod limbs. These evolved into legs of the first tetrapod land vertebrates; amphibians
- they have two dorsal fins with separate bases, as opposed to the single dorsal fin actinopterygians (ray-finned fish)
- many early sarcopterygians have a symmetrical tail
- all possess teeth covered with enamel
70
Colonising the land`
- the lungfishes (class Dipnoi) were important predators in shallow-water habitats in the Devonian, but most lineages died out
- the six surviving spp live in stagnant swamps and muddy waters in the southern hemisphere
- they have lungs and gills; can burrow in mud when ponds dry up, and survive many months in an inactive state while breathing air
- some descendants of early fish with jointed fins began to use terrestrial food sources and over time fully adapted to life on land
- this lineage is believed to have given rise to the tetrapods: the four-legged amphibians, reptiles, birds and mammals of today
71
Origin of Tetrapods
- the proto-tetrapod evolved from a sarcopterygian, with Dipnoans (lungfish) as closest extant relatives
- most likely ancestor was an Elpistostegid (extinct group):
> crocodile-like flattened body
> no dorsal or anal fin
> dorsal eyes
> reduced tail
> pectoral girdle and fins attached to opercular bones over gills
72
The closest relative of Tetrapods?
- a Devonian fossil found on Ellesmere Island (arctic Canada) in 2006 may represent an intermediate between a finned fish and a limbed tetrapod
- pectoral girdle and fins separated from opercular bones and skull
73
Feeding advantages of separating the pectoral girdle from skull
- once the pectoral girdle is free from the skull greater mobility is possible in the skull
- this is enhanced by the architecture of the two occipital condyls and the presence of the atlas
- the snout and jaws became elongated (seen as relative shortening of otic-occipital region)
- there is improved articulation of the jaw, and expansion of the primary palate
74
Advantages of terrestrial life - why did lobe-fins evolve into limbs?
- adaptation to temporary and shallow pools
- foraging above water surface (insects, plants)
- juvenile dispersal movements
- escape from predatory fish
- new semi-terrestrial (amphibious) foraging niches available
75
Consequences of terrestrialisation
- smell
- reproduction
- circulation with multiple respiratory structures
- skeletal solutions to terrestrialisation:
> pectoral girdle is divorced from back of skull (implications for sound conduction)
> undulatory locomotion
> suspension of vertebral column
> regionalisation of vertebral column
> organisation of amphibian vertebrae
> suspension of internal organs
> reorganisation of the skull
76
Adaptations to transition to life on land?
- no buoyancy in air, so weight-bearing is crucial
- movement facilitated by limbs, to apply force to the land surface for propulsion
- gills collapse in air, so lungs are required for gas exchange (symplesiomorphy: already present in a common ancestor with Dipnio)
- water loss as evaporation in air required production of concentrated urine in kidneys (also providing a route for nitrogen excretion as insoluble uric acid salts)
77
Buccal pump - extracting oxygen from air
- opens mouth, depresses buccal floor drawing in air, closes opercular
- closes mouth, air held in buccal cavity
- presses buccal cavity (becomes smaller), air is pumped into lungs - positive pressure system
- elastic recoil causes air to move back into buccal cavity
- air then exits via mouth and operculum
78
Adaptations to terrestrial life
- supporting vertebral column
- zygopophyses evolved which are regions of the vertebra that fit against the preceding vertebra, allows bending inwards but doesn't let the vertebral column sag, allows sufficient support
- NOTE: zygapophyses are absent in modern aquatic animals (a later evolutionary reversal)
79
Tetrapod skeleton: Acanthostega
- stem tetrapod, late Devonian ~360mya
- low, sprawling animal
- large tail fin, suggests amphibious lifestyle
- separation between pectoral girdle and skull
- definite limbs with 8 fingers
- weak zygapophyses
- little vertebral regional differentiation
80
Tetrapod skeleton: Ichthyostega
- another stem tetrapod, late Devonian ~360mya
- stronger zygopophyses and stronger sacral connection
- differentiation between vertebrae, abdominal region with large ribs to protect internal organs
- smaller tail fin
- more robust limbs
- still likely to be amphibious as rear limb is paddle-like
- reduced digits, 7 toes on hind limb
81
Non-amniote tetrapods
- early tetrapods tended to be scaled (like their sarcopterygian fish ancestors)
- superficially crocodile-like
82
Temnospondyls: sister group to modern amphibia
- most non-amniote tetrapods were wiped out in the Permian/Triassic mass extinction (250mya)
- but some Temnospondyls survived until the early Cretaceous (130mya)
- Lissamphibia (liss=smooth) diverged from them in early Triassic
83
Amphibians (extant)
- they have two-phase life history
- there is usually a free-living aquatic developmental stage
- there is usually a terrestrial juvenile/adult stage
- they have cutaneous respiration (via the skin) (high SA/V ratios, dependence on water)
- terrestrial adults have lungs
- aquatic larvae and neotenic forms have gills
- lungs employ force pumps - they have no diaphragm
84
Lissamphibian (Urodela, Anura and Gymnophiona) teeth
- pedicellate teeth - crown and base made of dentine with uncalcified area inbetween
- the tooth has a crown and pedicel, as the crown wears, it breaks off and is replaced by a new one
85
Amphibian skin
- moist (mucus), permeable skin, poison glands
- they have two types of skin gland:
> mucous gland - maintains moist skin for respiration
> granular glands - produce toxic secretions
- epidermis is minimal
86
Amphibian hearing
- like other tetrapods, amphibians have Basilar Papilla, but they also have a larger 2nd Amphibian Papilla:
> Basilar Papilla: 1200-1600Hz
> Amphibian Papilla: 200-800Hz
- operculum - columella complex (two bones transmitting sound to inner ear)
87
Amphibian vision: rods
- adult amphibians typically have 4 types of photoreceptors
- 2 types of rods:
> "red" rods: contain rhodopsin - green wavelength
> "green" rods: unique to amphibians - the blue wavelength
> some possess a third type of rod photoreceptor that contains the purple-receptive porphyropsin. Most commonly found larval amphibians and in spp that remain aquatic throughout life - UV range
- changes during metamorphosis and the breeding season
88
Amphibian vision: cones
- adult amphibians typically have 4 types of photoreceptors
- 2 types of cones:
> single cones: contain pigment that has peak absorbance at 580nm - the yellow wavelength
> double cones: consist of two cones fused together - one contains rhodopsin, the other contains the same yellow responsive pigment as the single cones
- changes during metamorphosis and the breeding season
89
Amphibian/reptile colouration
- colour - pigment cells
- melanophores: black, brown reddish
- iridophores: reflect light
- xanthopores: yellow, orange or red
90
Urodela - salamanders and newts: facts and features
- unspecialised body form
- undulate swimming
- paedomorphosis common (retain juvenile features)
- 400 spp
- troglodytes common (cave-dwellers)
- precise courtship ritual for spermatophore transfer
- paedomorphosis ex: Axolotl - larvae fail to metamorphose, so adults remain aquatic and gilled. Almost extinct due to urbanisation.
- Mole salamander - can delay metamorphosis depending on resources even after reaching sexual maturity
91
Anura - frogs and toads: facts and features
- 3750spp
- an=without, uro=tail, without tail
- enlarged hind legs
- urostyle - fused posterior vertebrae
- fast, powerful, hindlimb muscles
- specialised section of the brain
- use both lungs and skin to extract oxygen from the environment
- Dart -poison frogs:
> Family: Dendrobatidae
> batrachotoxin
> lethal dose for 68kg human is ~100ug
> 10x more toxic than tetrodoxin (TTX from pufferfish)
> brightly coloured to warn predators of their toxicity
92
Gymnophiona - caecilians: facts and features
- legless and either burrowing or aquatic
- tropical southern hemisphere distribution
- dermal scales
- internal fertilisation
- nests or viviparity
- elaborate gills in some aquatic spp
93
Amphibian repoduction
- external or internal fertilisation
- water or land
- larvae or miniature adults initially
- parental care (often male):
> attached to adults
> mouth or stomach brooders
> ovo-viviparous
- courtship
> pheromones
> dimorphism
> advertisement (mating) calls
> strong sexual selection through mating competition (usually by female choice)
94
Amphibian adaptations to the environment
- pond/stillwater larvae stockier with larger gills
- stream types slender; more hydrodynamic with smaller gills
- terrestrial types have form much more similar to adults
- newt metamorphoses to a frog
95
Fully colonising land (reptiles)
- two features stopped dependence on aquatic environments:
> the evolution of an egg with a shell impermeable (for the most part) to water (but allows gas exchange)
> a combination of traits that decreased water loss, such as skin that is impermeable to water loss (apomorphy) and kidneys that could excrete concentrated urine (plesiomorphy shared with Lissamphibia)
- the vertebrates that evolved these traits are known as the amniotes (after the type of egg they produce)
96
Amniote eggs
- leathery or have a calcium-impregnated shell (birds) that prevents the evaporation of fluids from within, but allows O2 and CO2 to pass by diffusion
- the eggs store large quantities of yolk that allow the embryo to attain a relatively advanced state of development before it hatches
- amniote eggs have 4 extra-embryonic membranes:
> amnion - surrounds the embryo itself
> chorion - surrounds the embryo and yolk sac and fuses with the egg for gas exchange
> yolk sac - surrounds yolk which nourishes the embryo
> allantois - evolved to store nitrogenous waste and aid gas exchange between embryo and egg surface (grows as embryo develops)
97
Main groups of Reptilia
- Synapsids (mammal-like reptiles, including ancestors of mammals)
- Sauropsids (lizard-like reptiles):
> Anapsids - "parareptiles" including testudines (turtles, tortoises)
> Diapsids - archosaurs (dinosaurs, crocodiles, birds), lepidosaurs (lizards, snakes)
98
Relationship of amniotes - REFER TO DIAGRAM (L7)
REFER TO DIAGRAM (L7)
99
Archosaurs: dominated the Mesozoic Dinosauria
- Saurischia:
> Sauropodomorphs (Apatosaurus, Diplodocus)
> Theropods (Tyrannosaurus, Velociraptor, Birds)
- Ornithiscia:
> Ornithopods eg. Hadrosaurs (duckbills)
> Pachycephlasaurs (thick head)
> Stegosaurus (plated) and Ankylosaurs (armoured)
> Ceratopsians (horned)
100
Saurischians vs Ornithischians
- difference in shape of pelvis
- Ornithischians have hips very similar to current birds
- however birds arose from Saurischians
101
Reptiles: facts and features
- early amniote lineage that arose and diversified during the carboniferous period (360-290mya)
- although traditionally called a class, they are a paraphyletic group
- some spp are ovo-viviparous (have eggs that do not develop shells and are retained within the females body until they hatch
- some evolved a placenta that nourishes the developing embryos
- have skin covered with keratinised scales that reduce water loss, they exchange gas by the lungs and have a divided heart with chambers that separate oxygenated and deoxygenated blood
102
Archosaurs: old lizards
- the crocodilians (subclass: crocodilia) are confined to tropical and warm temperature environments
- they spend much of their time in water but build nests on land or on floating piles of vegetation
103
Testudines: facts and features
```
- shell is the primary characteristic
> carapace
> plastron
- 2 groups:
> Cryptodires
+200 spp
+retract head vertically
+snapping turtles, marine turtles, tortoises, terrapins
> Pleurodires
+50 spp
+ retract head horizontally, snake heads
- vertebral column and ribs fused to carapace
- limb girdles inside shell
- diaphragmatic ventilation
- pharyngeal and cloacal respiration (aquatic spp)
- temperature-dependent sex determination:
> cool for males
> warm for females
```
104
Diapsids: facts and features
- marine lineages (extinct)
> Plesiosaurs (ribbon reptiles)
> Ichthyosaurs (fish reptiles)
- terrestrial lineages (living) - Lepidosaurs
> Sphenodontida (Tuatara)
> Squamata (lizards, snakes)
> tuatara are a sister group to lizards, this group was diverse in the Mesozoic, but only two spp exist today on 30 small islands off New Zealand
> Squamata include lizards (3000 spp), snakes (2500 spp) and amphisbaenians (150 spp)
105
Snakes: facts and features
```
- specialise in:
> locomotion
> prey capture
> swallowing
- ecological types:
> fossorial (burrowing)
> epigean (living at soil surface)
> aquatic
- consequences of diameter reduction:
> left lung reduced or absent
> gall bladder posterior to liver
> right kidney anterior to the left
> gonads offset (variable)
- a huge meal leads to a massive changes in a snakes metabolic rate, and some internal organs increase greatly in size (liver >200%)
- locomotory types:
> lateral undulation
> rectilinear (scales move against internal lining, moves straight forward)
> concertina (oscillatory)
> side winding
- snake feeding specialisations:
> skull with 8 flexible links
> asymmetrical kinesis
> constriction (for asphyxiation)
> venom (toxins)
```
106
Snakes: venomous snakes
- fast moving with thin bodies
- 3 morphologies:
> Opisthoglyphagous - "back fanged", one or more enlarged tooth near near rear of the maxilla, may have a groove to inject saliva
> Proteroglyphous: hollow fangs on front of maxilla, permanently erect, short teeth erect
> Solenoglyphous: only teeth on maxilla are long hollow fangs, maxilla rotates to allow jaw closure
- venoms, may include one or more of:
> proteinases (tissue destruction)
> hylaurodinases (tissue permeability)
> amino acid oxidases (tissue destruction)
> phospolipases (cytolytic)
> polypeptides (neurotoxic)
107
Feathers
- types:
> down
> flight
> contour
> semiplumes
- down feathers are also known as 'teleoptiles' (true feathers)
- components:
> keratin
> melanin
> carotenoid pigments (physical colours)
- white - a 'colour' generated by reflection of all wavelengths; blue colours formed by reflection of incident light from turbid porous layers over melanin
- iridescent colours (eg. Hummingbirds) are generated by interference
- feathers are dead structures, but during growth are well endowed with blood vessels
- an individual flight feather has an aerofoil cross section for lift
108
Feather uses
- contour feather: no flight function therefore symmetrical each side of shaft, cover the entire body
- down/(smaller) powder down feather: soft and fluffy, trap air to create a layer of insulation next to the bird's body
- bristle feather: stiff shaft and barbs only at base, or not at all. Occur most commonly around the base of the bill, eyes, and as eyelashes
- filoplumes: hairlike feathers; very fine shaft with a few short barbs at the end. Typically covered by other feathers, may function as pressure and vibration sensors
- semiflume: fill in between contour and down feathers
109
Feather arrangement
- refer to slide w/ picture
- bones arranged like a vertebrate forelimb: humerus, then radius (inside) and ulna (outside), then the 'hand' which has reduced number of digits
- the flight feathers attached to the hand are the primaries, there are usually ten of them (I-X) in most spp, these generate power
- the flight feathers inserted into the ulna are the ulna are called the secondaries, these generate lift so are very important for level flight
- pterylae: (contour feathers, flight feathers) discrete tracts of feathers growing down the body and wings
- spaces in between - apteria: covered with down and semiplume feathers at edges - atleast in northern temperate spp that need to conserve heat. Tropical spp tend not to have feathers at apteria.
110
Birds and dinosaurs - fossil evidence
- dinosaur fossils have been found with quill knobs
- birds are closely related to dinosaurs
- we now know spp such as Velociraptor had feathers on their bodies
111
Arrangement of the wing
- the primaries are covered by greater primary coverts, which are covered by median primary coverts, covered by lesser primary coverts
- the secondaries are covered by greater coverts, covered by median coverts, covered by lesser coverts
- both lesser coverts and lesser primary coverts are covered by marginal coverts on the leading edge of the wing
- the alula is an important flight surface attached to the bone of the thumb (next to lesser primary coverts) and can move independently relative to the rest of the hand of the bird
- emargination: different flight feathers have different uses in flight
112
Feathers and glands
- feathers are epidermal structures
- the skin of birds is thin, loose and dry
- no sweat glands, the only cutaneous gland is the uropygial gland
- the uropygial gland (preen gland) is used to keep feathers in good order, found at the base of the tail. Waxes, fatty acids, fat and water to coat feathers and keep them in good condition.
113
Feather structure
- calamus or quill: the part that lies under the skin
- rachis: the central shaft
- barb: go out either side of the rachis
- barbules: potrude from the barbs with hooks on their surface
- hooks: attach to the barbules together in between barbs forming a relatively discreet surface
114
Evolution of feathers: stages and uses
```
- potential stages:
> filamentous --> down --> vaned
> OR strap (elongated scale) --> vaned --> downy
- uses (possible):
> flight (not supported evidence)
> insulation (most likely)
> display
> prey capture (unlikely)
> waterproofing (maybe)
> temperature regulation (not just insulation)
```
115
Evolution of feathers: example
- Protopteryx fengningensis
- most primitive known Enantiornithes, extinct group of birds dominant in the Mesozoic era
- strap or strip-like tail feathers resemble both reptilian scales and modern feathers
- evolutionary model for early stages of feathers:
> elongation of scales
> appearance of central shaft
> differentiation of vanes into barbs
> appearance of barbules and barbicels
- but the tail could be a secondary derived feature
116
Additional flight surfaces
- tail:
> minimises drag, imparts control, additional lift at low speed
> tail feather shape dependent on place in tail, outer feathers are aerofoil
> control and lift
> increased maneuverability
- feet: webbed feet on auks (ducks, swans etc.) - these also generate lift and impart control and stability
117
Moulting
- def: periodic shedding of the epidermal structures called shedding
- why moult?
> feathers worn out
> worn feathers insufficient in flight
> also inefficient for insulation
> also inefficient for waterproofing
> dull, not good for attracting a mate
- wear results from:
> abrasion (rocks, vegetation)
> UV damage
> bacterial activity
> mallophaga (feather lice)
> general wear and tear
- structural strength of feathers increased by melanin, feather wear can change colours (display) both in visible and UV spectrum
- plumage sequence: nessoptile --> juvenile --> adult
- moult types:
> partial (body only)
> full (body and flight feathers)
- juvenile moult usually partial
- moult cycle: first is a nestling PJ moult, then breeding full moults onwards
118
Moult progress
- dorsal: from centre of dorsal tract, down body then up to crown
- ventral: from centre of ventral tract (either side) then down the body
- on the wings:
> primaries moult to the distal end of the wing
> secondaries moult to the proximal end of the wing
> tertials moult to the distal end of wing
> some water birds moult all flight feathers at once as they can sit on the water relatively safe from predators
> when feathers drops out the preceding feathers will be nearly full grown
119
Bird migration
- birds are mobile: they can move to follow resources, within a season (eg. hard weather movements) or between seasons (seasonal migrants)
- in Europe/Asia 5 billion birds are involved in autumn migration each year
- Bristle-thighed strip of Alaska, winter in Pacific ilsands - minimal sea crossing of 2000 miles
- small, new world warblers can fly non-stop for 86 hours from north to south America
- true migrants: move long distances; retain historical patterns of dispersal
- cost vs benefits:
> costs - increased mortality risks, imperative to get back to breed in time
> advantages - favourable conditions elsewhere may lead to higher survival or greater breeding success
120
Fuel for migration
- mainly fat: small migrants can increase their body mass by 150% by obtaining subcutaneous and intra-abdominal fat eg. garden warbler - normal weight is 16g, autumn weight might be 26g, an increase of 60%
- flight muscle mass needs to be increased to generate additional power to carry extra fat load
- some extra protein load can be metabolised during flight as fuel and to maintain optimal power and weight
- birds with this much fat may be able to fly 2000km in a single flight. Birds such as these have to cross the Sahara desert, this requires a single flight of 600 miles if it is done all at once
- fat has twice the energy per gram metabolised than protein or carbohydrate
- protein also metabolised, necessary for fat metabolism
- some spp reduce weights or body organs, consequences for refueling
121
Migratory behaviour
- stimulated by changes in photoperiod, which results in hormonal changes, particularly an increase in thyroid hormone (TH)
- note that increase in TH also stimulates moult - we don't understand the fine details of how these separate processes are controlled
- there are three important processes in migratory spp: migration, moult and reproduction - in general these are done one at a time
122
Migration and navigation: how do we know where birds go?
- ringing with light, uniquely numbered metal rings, important tool for ornithological research and conservation- started in 1909
- resightings (metal rings or colour rings or other marks)
- retraps
- recoveries of dead birds
123
Amniote skull types
- amniotes are four limbed tetrapods with waterproof eggs
- anapsids: (ie. turtles) have no temproal fenestra
- synapids: (ie mammal-like reptiles) have a single fenestra (hole in the skull behind eye)
- diapsids (ie. lizards and snakes) have two fenestras
124
Pelycosaurs: facts and features
- abundant terrestrial forms in the late carboniferous/late Permian 9320-265mya)
- herbivores and carnivores with primitive heterodonty (different teeth)
- relatively long limbed with parasagittal gait (compared to other reptiles)(their limbs moved parallel to their body)
- elongated neural spines on vertebrae (weight-bearing and thermoregulation)
125
Pelycosaur: Dimetrodon limbatus
- type of Pelycosaur
- neural spines (back-sail) thought to have had a thermoregulatory function:
> allowed organisms to warm up quickly in the morning
> large surface area to allow heat to dissipate quickly
> may have angled the sail away from sun to cool down or altered blood flow to stay warm at night
- inhabited well-vegetated lowland ecosystems
- larger of the spp were top predators
- carnivore, fed on aquatic organisms and terrestrial tetrapods
126
Therapsids
- worldwide occurrence in late Permian (240mya) before the breakup of Pangea
- longer limbed, more upright stance, rib reduction
127
Cynodonts: facts and features
- complete loss of lumbar ribs
- secondary palate, creating nasal passage with turbinal bones (heat exchanger?)
- greater heterodonty, dentary expansion and zygomatic arch (allows new zone of muscle attachment for stronger bite)
- articular-quadrate jaw articulation, later cydodont have no articluar and quadrate, only bottom jaw with squamosal bone (hinge)
128
Mammals: features
```
- synamorhpies (defining nodes in cladograms: shared derived character traits):
> 8 - enlarged dentary
> 9 - prismatic enamel tooth surface
> 10 - dentary: squamosal jaw articulation
> 11/12 - tribosphenic cheek teeth
> 13 - placenta
- tribosphenic cheek teeth
> huge roots
> very varied surfaces (hypocones, metacones, paracones)
> fit together, advanced teeth
- mammalian middle ear
> embryology shows homologies:
+articular = malleus
+quadrate = incus
> stapes also (only in reptiles)
```
129
Monotremes (ie. Platypus)
- egg laying with extended maternal care: incubation followed by lactation from tufts of hair
- Cretaceous fossils (140mya) from Australia and south America have tribosphenic cheek teeth (molars)
- Platypus (1 spp) nests in burrow, 2 eggs from functional left ovary, 16 weeks of maternal care; young have temporary molars
- Echnida
> 2 spp, Australia and New Guinea
> lays a single egg and incubates it in a pouch (homoplastic/convergent with marsupial condition)
130
Diversity of marsupial forms
- about 334 extant spp, 70% in Australia and rest in south America, few in central and north America
- representative types that morphologically and ecologically similar to placentals occurring elsewhere
- convergent evolution on a grand scale
131
Marsupial characteristics: distinct from monotremes
- separate anus and urinogenital sinus (vs dual function cloaca)
- testes in scrotum outside body wall (vs internal)
- paired lateral virginae and bifid penis
- placenta, gestation (vs. shelled eggs incubated externally)
- discrete mammary glands with teats (vs diffuse tissue)
132
Marsupial characteristics: foetal development
- all marsupials develop a choriovitelline (yolk sac) placenta (convergent/homoplastic with Eutherian condtion)
- some bandicoots also briefly develop a chorioallantoic placenta (homologous with Eutheria and some reptiles)
- gestation of 10-20 days
- birth through medial canal
- precocious young migrate unaided to teat, usually in pouch
- initial permanent attachment, with secondary palate allowing simultaneous breathing and swallowing
133
Mammals: skull and teeth
- heterdonty very evident
- dental formula 5.1.3.4 (i.c.pm.m) = 50
- no tympanic bulla apparently around ear apparatus (possum)(allows for more teeth)
134
Mammals: cheek tooth specialisations
```
- Bunodont:
> flattened for crushing in omnivores
> large root
- Lophodont:
> ridged grinding surfaces
> cement, dentine, enamel all exposed, gives uneven surfaces
- Hypsolodont:
> open rooted for continuous growth
> constantly sharpened
- Selendont (ie deer)
> crescent shaped molars
> convergent with hysodonty in functional anatomy
- Sectorial cheek teeth
> slicing canassials
> associated with tight jaw articulation
> eg. cats, dogs etc.
- Incisor specialisations
> gnawing: open-rooted, enamel only on anterior surface, so self-sharpening
> enamel on both sides
> different jaw articulation positions for gnawing and grinding
```
135
Hindgut vs foregut fermenters
- Hindgut
> food chewed once
> fermentation of glucose --> sugar in cecum and colon, also absorbed here
> rate of passage = 48 hours, cellulose utilisation = 45%
- Foregut fermenter (ruminant)
> food chewed several times
> fermentation + absorption in rumen and cecum
> rate of passage = 80 hours, cellulose utilisation = 60%
136
Limb structure: forelimb
- scapula (shoulder)
- (then) humerus
- (then) radius + ulna
- (then) carpal bones
- (then) metacarpal bones
- (then) phalanges
137
Limb structure: hindlimb
- pelvis (hip)
- (then) femur (+ patella [kneecap])
- (then) tibia + fibula
- (then) tarsal bones
- (then) metacarpal bones
- (then) phalanges
138
Stance and gait
- plantigrade (quite slow):
> ie. beaver, humans
> phalanges, metatarsals, tarsals and calcaneal heel on ground
- digitigrade (elongated; more power + acceleration)
> ie. dog
> phalanges on ground
> metatarsals, tarsals and calcaneal heel raised
- unguligrade
> ie. pigs
> all risen (stand on toe nails)
> heavy proximal and little distal musculature (lots of muscle at top of leg), extremities moved via tendons, great speed and endurance possible; cursorial (running gait)
- Graviportal
> ie. elephants
> massive columnar limb bones
> to resist crushing under own body weight
- Perissodactyla: odd-toed ungulates
- Artiodactyla: even-toed ungulates
139
Why did cursorial herbivores evolve?
- Hyp 1: evolutionary arms race between predator and prey?
> pursuit carnivore mammals only appear in the Pliocene (5mya), long after larger long-legged ungulates do so
- Hyp 2: low productivity grasslands replaced high productivity woodlands, requiring wider-ranging to find food
> Oligocene (30mya) in south America, early Miocene (20mya) in north America; late Miocene (10mya) in Eurasia
> cursorial ungulates appear at these times on each separate land mass
140
Limb structure variation
- fossorial adaptations (digging/burrowing):
> short, massive limbs
> specialised claws and teeth
> ie. molerat, mole
- arboreal adaptations:
> gripping feet and claws
> tails for balance
> opposable thumbs (primates) + prehensile (gripping tail)
- volant forms (gliding):
> patagium (flight membrane)
> ie. flying squirrels
- flight:
> patagium stretched over phalanges of forelimb and to tail (uropatagium), ultrasonic system for orientation and prey capture
- amphibious forms:
> tail as propeller and rudder
> paraxial swimming
> ie. otter
- mainly aquatic forms:
> axial swimming
> substantial forelimb props, hindlimb rotated forward on land
> (true seals): forelimbs reduced, hindlimbs permanently reflected backwards
- Completely aquatic:
> Cetacea
> Odontoceti (toothed whales): sperm, killer etc.
> Mysticeti (baleen whales): blue, right etc.
> Sirenia
+Dugong, manatee (4 spp)
+related to elephants
+trophic marine and estuarine distribution
141
Biogeography
mammalian distributions have been affected by two phenomena:
- vicariance: earth history, continental drift eg. monotremes in New Guinea and Australia
- dispersal movements eg. marsupials in Australia
142
Historical biogeography of marsupials
- mid-Cretaceous (100mya) origin in north America
- constituted half the mammal spp there in the late Cretaceous (65mya: KT boundary)
- Eocene (55mya) fossils in Australia, with earlier ones in Antarctica
- also present in Eurasia and north Africa until Miocene (20mya)
- after 100my of separation, north and south America rejoin in Pliocene (2.5mya) via the Panamanian isthmus
- the 'Great American Interchange' then commenced involving dispersal of both marsupials and placentals to/from north and south
- invasion of south America by placentals from the north did not cause rapid extinction of endemic marsupials
- many placental and marsupial mammals moved north from south America (eg. Capybara to central America)
- some went further north (eg. porcupine)
- Virginia opossum reached Canadian border in 1950s
- later Pleistocene extinctions throughout norht America were at the hands of man ('overkill hypothesis') and/or a consequence of climate change
143
Novacek tree
- 4 or 5 clusters, Xenartha quite different from other placentals
- new information has modified the tree, Xenartha not on their own, new Afrotheria clade
144
Eutherian phylogenetics
- molecular (mtDNA sequence) data and morphological characters generate different cladograms
- Paenungulates (elephant, hyrax, sirenia) close to ungulates on morphology, but a separate stem group on molecular evidence, including hyrax and sirenians
- homologies vs homoplastys
- bats close to primates on morphology, but close to ungulates on molecular evidence
- tree shrews, flying lemurs and primates emerge as close relatives on both cladograms
145
Advantages of air over water as a respiratory medium?
- mass of medium
- viscosity of medium
- high rate of diffusion in air
- O2 is relatively easy to access and fairly constant in air
- air has low heat conductivity and low heat capacity
- for equivalent amount of O2, an animal would have to move 25,000x the volume of water than air
146
Current marine mammals
```
- Cetacea (whales, dolphins + porpoises)
> Mysticetes (Baleen whales) - 14 spp
> Odontocetes (Toothed whales) - 76 spp
- Pinnipeds (seals)
> Otariidae (sea lions and fur seals) - 13 spp
> Odobenidae (walrus) - 1 spp
> Phocidae (true seals) - 18 spp
```
147
Cetacean general adaptations
- morphological adaptations; 3:8 ratio (D:L)
- increased insulation
- circulatory adjustments
- counter-current heat exchangers
- adaptations for osmoregulation
- sensory adaptations
- diving capabilities
148
Cetacea: long lived and low recruitment
- long lived (18-100+ years)
- relatively late sexual maturity and seasonal breeding
- single calf per breeding event
- cetaceans breeding interval = 1-4 years
- calf and juvenile natural and anthropogenic mortality
- dolphins and porpoises population growth about 1-4% per year
- large cetaceans can be higher 1-10%
149
Age determination of toothed mammals
- age needed to determine/estimate life history parameters
- reading decalcified, sectioned and stained teeth
- Growth Layer Groups (GLGs)
- complete GLG = 1 year
150
Age determination of baleen whales
- reading Growth Layer Groups (GLGs) in ear plugs
- complete GLG = 1 year
- grow per year
151
Right whales: facts and features
- 4 spp + pygmy right whale
- forage by moving through water column just under the surface filtering as they go
- can be identified by their blows
- normally lack dorsal fin
152
Delphinidae (dolphins): facts and features
- 38 spp
- coastal and offshore spp: common vs Indo-Pacific Bottlenose
- small vs large size: Indian Ocean Humpback dophin (2m) vs Killer whale (6-7m)
- small vs large groups: Sousa sp. (1-5) vs spinner dolphin (500-1000)
- fluent vs stable groups: bottlenose dolphin (fission-fusion) vs killer whale (maternal groups)
- all echolocate and communicate
- generally non-migratory, females stay in natal ares, males roam larger areas
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Phocoenidae (porpoises) - 6 species
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- 6 species
> Harbour porpoise
> Burmeister's porpoise
> Vaquita
> Spectacled porpoise
> Finless porpoise
> Dall's porpoise
```
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Cetacea - general reproductive biology and social structure
- lack of information on mating and reproductive behaviour of many cetaceans in the wild
- in general, cetaceans have polygynous and promiscuous mating systems. Most have seasonal reproduction. Large testes indicate sperm competition. Male competition and mate guarding indicative of polygynous mating system. Females do most of the investment and all the parenting.
- Mysticetes do not often group together, form schools or pods. Group foraging humpback whales and competitive mating groups in humpback and right whales are exceptions. Reversed sexual dimorphism - females larger in most spp.
- Odontocetes on the other hand form various types of more or less stable groups depending on species and activity
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Group living in Odontocetes
- offshore living in smaller odontocetes (eg. Pilot whales, spotted, spinner and bottlenose dolphins) live in larger groups (100-1000 individuals)
- large group advantages:
> protection against predators
> easy to find mates
> cooperative foraging
- large group disadvantages:
> competition for prey
> risk of inbreeding (if all breeding occurs within group)
> risk of extirpation if subjected to large scale mortality event (eg. human caused pollution, hunt, fisheries bycatch, military sonar) or disease outbreak (eg. virus)
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Cetacean hair
- hair of Oratiids (+sea otters and polar bears) has two layers: outer protective guard hairs and inner soft underfur hairs
- Phocid and walrus lack underfur and instead have blubber
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Cetacean moulting
- all phocid seals, the sea otter, and the beluga whale, are known to undergo an annual moult. As many phocids are pelagic for most of the year, the short moult period ashore likely serves a different purpose: an annual opportunity to repair and renew their pelt and epidermis
- the moult varies amongst pinnipeds. The lanugo (baby fur) is moulted in the uterus of hooded, harbour and bearded seals before birth. The in utero moult of the lanugo reflects a secondary adapatation to breeding on land. More recently it has been argued that prenatal moulting, like prenatal blubber disposition, is instead an adaptation to enabling newborn pups to enter cold water without adverse consequences.
- in all other pinnipeds the natal coat is moulted at various stages up to a few months of age
- after this moult, the adult pelage is shed and replaced annually
- moulting takes place during the summer and autumn (Dec-Apr/May) in the southern hemispehere
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Overheating prevents distribution in warmer habitats
- in contrast to the fat reserves of adult seals and whales, most pinniped pups are born with very little blubber and must develop a covering of fatty insulation quickly to survive eg. harp pups born on open pack ice make good use of sunlight , which is reflected by their translucent (white) hairs onto their dark skin
- the distribution of pinnipeds towards the equator is limited by their inability to thermoregulate at elevated temps, especially during periods on land (ie. during parturition, nursing, and the post-weaning fast and for some spp during the annual moult)
- it is important to remember that the same anatomical adapatations (ie. blubber) that conserve while in the water inhibit heat dissipation when out. When temps are high seals enter the water and rest in tidepools and caves
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Cetacean and pinniped reproduction
- need to find mates
- substrate for giving birth
- optimal time for pup survival
- the benefits of an annual reproductive cycle have led to delayed implantation in pinnipeds, sea otters and polar bears
- in all placental mammals, embryonic and fetal development occurs within the mothers uterus during extended gestation periods. Pregnancy is maintained by the production of chorionic gonadotropin until birth occurs
- nursing periods range from 4 days in hooded seals to several years in some otariids, walruses, polar bears, odontocetes and sirenians
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Cetacean and pinniped potential for population growth
- the number of offspring a female mammal produces is is determined by her frequency ( which is never more than once per year) and the duration of her reproductive lifetime
- in polar bears, it also depends on the number of cubs produced during each pregnancy which is normally reduced by age (all other marine mammals normally produce a single offspring per pregnancy)
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How to investigate population structure?
- morphometrics
- genetics (eg. mtDNA and/or microsatellites)
- ecological: stable isotopes, contaminants and parasites
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Abundance/population size
- define area to be covered
- line or strip transects using vessel or aerial survey (airplanes, helicopters or drones)
- mark-recapture of individual animals eg. grey seal surveys are conducted during their annual moult
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Foraging ecology
two scales:
- ranging behaviour - where do they go to forage
- foraging itself - what do they do when they get there
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Foraging problems
- navigating in a featureless environment
- spatial distribution of prey
- environmental factors ie. tide
- prey distributed vertically as well as horizontally
- prey are not normally visible from the surface
- physiological limitations
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Why is oceanography important
- determines the location of food
- sites of primary production:
> sunlight (summer vs winter, depth etc)
> nutrients
- prey is patchy, need to locate high density patches
- factors:
> major currents dominated by gyres and wind patterns
> great ocean conveyor belt
> oceanic features:
+coastal upwelling - wind driven
+bathymetry - upwelling caused by currents and bottom structure
> fronts - water with temp and/or salinity discontinuity colliding
> eddies - result from circulation patterns
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SST and productivity
- sea surface temp higher at equator
| - primary productivity higher at poles
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El Nino Southen Oscillation
- El Nino: warm water 'tongue' of west coast of south America, thermocline drops
- La Nina: the opposite - thermocline increases
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Warm water anomaly 2005
- Californian sea lions 2003-2004: stayed close to coast
- 2004-2005: went further out into deeper water
- warm water due to reduction in upwelling, prey stayed further out to sea
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Diving behaviours definitions
```
- dive: the period of submersion
> descent
> bottom line ~ foraging time
> ascent
- surface: time spent at surface between dives
- dive cycle: dive + surface
- dive bout: a group of dives
```
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Some factors affecting foraging behaviour
- prey species
- prey movements and location (benthic vs pelagic)
- bathymetry
- time of the year
- sex of animal
- time of day
- physical state of the animal
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Prey migration
- many prey undergo diel migration
| - deep in day, shallow at night
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Constraints on diving
- light levels
- predators
- diving ability
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What do they eat?
```
- pinnipeds:
> feed primarily on fish and squid
> crabeater and antarctic fur seals krill specialists
> birds and other pinnipeds
- cetaceans:
> krill and invertebrates
> fish or squid
> other marine vertbrates
```
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Dentition in pinnipeds
- sharp, predatory: grey and leopard seals, californian sea lion
- crab eater seal: sieve-like teeth to catch krill
- majority of Cetacea have simple, conical teeth, to hold onto slippery prey
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Dive shapes
- soft/hard - square: benthic (to the sea floor)
- 'V': feeding in the water column, normally more simlar to square with wiggles (changing depth to chase prey)
- don't say whether they were successful
- skewed-right/left: skewed-right are negatively buoyant so descend quickly, skewed-left are positively buoyant so ascend quickly
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Foraging in relation to prey
- prey rise in water column at night
- most dives take place at night
- if diving takes place in the day it is far deeper
- Australian sea lion:
> doesn't forage at certain ties of the day
>as it is a benthic forager, prey is immobile (vertically)
- Elephant seal:
> spends most of its time submerged
> foraging dives down to 500m
> also travelling dives which are shallower
> processing dives for digestion etc. as they don't spend time at surface
>females:
+strong diel foraging behaviour
+deep diving during the day
+forage on deep scavenging layer (DSL)
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Pressure effects
- hydrostatic pressure: pressure at depth due to weight of the water column
- Boyle's law: how pressure changes as a function of depth
- prevention of lung collapse:
> a surfactant is produced, lowering surface tension of liquids, allowing alveolis to come apart more easily
> cartilaginous support: sacs of cartilage surrounding avleolar sacs
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Breath hold diving
```
- storing oxygen "on board" in:
> lungs
> muscles
> blood
- reduce oxygen usage
- aerobic vs anaerobic metabolism
- these animals breathe out before a dive to reduce buoyancy
```
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Dive duration is correlated with?
blood volume
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Blood must be used efficiently during dives
- more to muscles
- less to digestive tract
- cardiovascular system in pinnipeds:
> enlarged spleen (stellate plexus), lots of associated blood vessels, acts as oxygenated blood store
> stellate plexus connected to posterior vena cava
> vena cava connected to hepatic sinus (sinus meaning 'pool') a storage organ
> caval sphincter portions blood to the heart during dive, spleen volume reduces during dive
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Dive efficiency
- increase in body size, proportional to blood volume, but blood use increases more slowly with increasing body size, therefore more efficient
- more efficient swimming, streamlined
- hypometabolism:
> vasoconstriction and redistribution of blood
> 50% of resting metabolism costs due to organs
> increase tolerance to hypoxia
> Bradycardia (slowing of the heart)
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Bradycardia in different animals
- most animals undergo bradycardia
- largest effect in seals
- however all measurements are due to forced dives
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Is the measured dive response real?
```
- forced dives:
> no control over duration
> maximum response (fear)
- natural dives:
> animals control effort, duration and oxygen use
>graded response
```
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Aerobic Dive Limit (ADL)
- is the maximum duration that an animal can sustain aerobic metabolism. After this point, an animal would have to rely exclusively on anaerobic respiration/metabolism
- ADL is calculated from two factors:
> the usable oxygen stores
> the metabolic rate of the animal during submersion
* these variables are rarely known but can have a significant bearing on the interpretation of the diving behaviour
- ADL sudden 'switch' - refer to graph in notes
- ADL gradual 'switch' more likely - refer to graph
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Physiological changes from forced dive
- in example: seal submerged for 20 minutes
- O2 levels drop
- CO2 levels increase
- lactic acid levels remain low until the animal is allowed to surface (at 20 minutes), at which point they shoot up, because:
> blood supply to muscle has stopped
> muscles utilising anaerobic metabolism, producing lactic acid
> BUT muscles aren't receiving blood, lactic acid isn't seen
> until resurfacing where all muscles are flushed with blood, called the 'lactic acid flush out'
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What happens when O2 stores are depleted?
- lactic acid is present
- how does it deal with lactic acid
> oxidise lactate at the surface - increases recovery time
> recycle lactate back to glucose at the surface - increases recovery time
> oxidise lactate during subsequent dives - reduces dive duration
> recycle lactate during dive - reduced dive duration
> all scenarios sub-optimal
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In the field
- animals who utilise ice holes can be transported to a secluded ice hole meaning they can only use a singular hole
- labs can be built around these
- means animals are diving naturally
- not all dives are for foraging ie. drift dives of northern elephant seals including belly-up phase
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Lactate and recovery after diving
- diving animals don't always utilise the dive response
- no increase (above normal levels) of lactic acid up to 20 minutes (Weddell seal)
- first recorded ADL
- shown as little to no recovery time <20 minutes, above this there is recovery due to lactate because of anaerobic metabolism
- 13-24 minute dives: no lactate increase
- 20 minute forced submersion more similar to ~40 minute natural dive
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Diving efficiency: aerobic vs anaerobic
- 20 minute aerobic dive with 2 minute surface interval: 140 min dive with 14 min above water
- vs 60 minute anaerobic dive with 100 minute surface interval
- far more efficient to maintain physiology within their aerobic capacity
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Diving efficiency - optimising diving
- shallow, short travel distance, longer time spent foraging - foraging/dive time = high proportion of dive spent foraging, low cost of travel = high efficiency
- deep, long travelling time, short foraging - f/Dt = low proportion of dive spent foraging = low efficiency
- deep, short travel time (faster swimming), short foraging - f/Dt = high proportion of dive spent foraging but high cost of travelling - low efficiency
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Lactate levels during repetitive diving
- animals can dive straight away after a previous ADL-exceeding dive
- however subsequent dive duration is vastly shortened
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Blood parameters and muscle physiology during dive in Weddell seal
- blood oxygenation drops during dive, replenished during recovery
- blood acidity:
> no change in short dives
> after longer dives blood acidifies once animal resurfaces
- blood supply to (swimming) muscle decreased during dive after 20 mins, eventually bottoms out
- bradycardia (in seals) may be not related to anaerobic metabolism but instead to access oxygen attached to myoglobin (which only releases O2 when surrounding levels are low)
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Heart rate changes associated with diving in the grey seal
- they are ambush predators, sit and wait for prey to pass while resting on the sea floor
- heart rate drops massively (bradycardia)
- to access oxygen attached to myoglobin
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Monitoring diving seabirds
- metabolic rate increases during diving
- O2 stores not depleted (within ADL) as they are able to dive straight away again
- only at 2x BMR are dive ADLs big enough
- possible explanations:
> O2 stores are larger (very unlikely)
> O2 usage must be lower than expected
- how is BMR reduced?
> some data infer that dive reflex is involved but we have discounted anaerobiosis, diving may be strenuous but:
+stroke and glide, have to swim up
+ use buoyancy to ascend, but must swim down
+ so likely to be active at least during portions of the dive
> what about thermoregulation?!
+body temperature declined during diving in ruddy ducks
+temp changes in king penguins:
->parts of the body reduce in temperature
->stomach, abodmen (top) and abodmen (bottom) reduced in temp
->abodmen (bottom) reduced to 18 degrees C
