evolution of invertebrates and vertebrates Flashcards
1
Q
what is an invertebrate
A
- lacks a spinal chord and backbone
- lacks bones
2
Q
6 evolutionary events led to the evolution of metazoa
A
- multicellularity
- extracellular digestion
- nervous system
- middle germ cell layer
- bilateral symmetry
- through-gut
3
Q
evolution of multicellularity
A
3 theories
- symbiotic theory, different protozoa join together as symbionts
- colonial theory, asexual reproduction of cells that remain together
- cellularisation, multinucleate protist evolves cell membranes around its nuclei
4
Q
evidence for colonial theory, evolution of mulitcellularity
A
- choaloflagellate is a protists very similar to collar cells
- proterospongia is accumulation of choaloflagellate cells
- sponge contains collar cells
- none of these are closely related to each other
5
Q
embryonic development
A
- embryology recapitulates phylogeny
- blastea = hollow ball of cells
- cells differentiate and rearrange
- blastula forms
- creation of multiple cell layers through invagination or ingression
- gastrula = multilayered embryo
- each cell layer becomes different cell types
6
Q
diploblastic organisms
A
- ectoderm = outer layer, differentiates into epithelium etc
- endoderm = inner layer, differentiates into gut lining etc
7
Q
triploblastic organisms
A
- ectoderm = outer layer, differentiates into epithelium etc
- endoderm = inner layer, differentiates into gut lining etc
- mesoderm = middle layer, forms muscles, organs etc
8
Q
non-bilateria properties
A
- asymmetrical invertebrates
- include basal groups like sponges
- primarily marine
- covered in microscopic pores
- cellular level of organisation, lack tissues and organs
- diploblastic
- sessile
- defensive chemicals
9
Q
structure of sponges
A
- pinacoderm = outer layer of cells, pinacocytes = wide and flattened
- choanocytes = collar cells, line central atrium
- gelatinous non-living matrix in central atrium
- totipotent archaeocytes/ameboid cells within matrix, involved in feeding
- spicules
- porocyte = pore cell
10
Q
sponges, spicules
A
- small SiO2 or CaCO3 structures
- skeleton-like structural support
- secreted by specialised sclerocytes which fuse, lay down spicules then pull apart
- megascleres support sponge
- microscleres support sporocytes
11
Q
sponges, digestion
A
- intracellular
- flagella of choanocytes beat, creating a current to draw in water through pore cell for filter feeding
- food particles trapped in mucous around microvili that make up collar of choanocytes
- water exits through osculum (larger pore)
12
Q
sponges, reproduction
A
- external fertilisation
- choanocytes can differentiate into gametes in breeding season, eggs often retained and larvae released
- planktonic larval form drift around in water column
13
Q
4 phyla in non-bilateria group
A
- poripheria (sponges)
- placozoa
- Cnidaria
- Ctenophora (comb jellies)
14
Q
placozoa
A
- arose from the evolution of extracellular digestion and true epithelium, advantageous for growth and predation
15
Q
evolution of the nervous system
A
- gave rise to neuralia clade
- gave rise to cnidaria
- organisms can swim and respond to the environment
16
Q
Cnidaria structure
A
- epidermis contains epithelialmuscular cells, totipotent interstitial cells, cnidocytes (stinging cells), mucous gland cells, sensory cells that make up nerve net
- mesoglea = gelatinous matrix in between
- gastrodermis lines gastrovascular cavity and contains enzymatic gland cells, nutritive muscular cells, mucous gland cells and some nerve cells
- 2 morphs
17
Q
cnidaria, 2 morphs
A
- polyp, sessile, tentacles pointing upwards
- medusoid, tentacles pointing downwards
- species often travel through both morphs in their life cycle
18
Q
phyla Cnidaria, class hydrozoa
A
- marine and freshwater
- colonial organisms
- polymorphic polyps
- cnidae only present on epidermis
- alternation of generations
19
Q
Cnidaria properties
A
- anemones, corals, hydroids, jellyfish etc
- once thought to be radially symmetrical but now thought to be bilaterally symmetrical (cilliated groove down middle of animal on inside), so possibly not in non-bilateris
- all have stinging cells, cnidocytes
- mostly marine
- tissue level of organisation
20
Q
phyla cnidaria, class scyphozoa (true jellyfish)
A
- all marine
- medusoid stage dominant in life cycle
- thick mesoglea
21
Q
scyphozoa (true jellyfish) life cycle
A
- adult medusa is dioecious (either male or female)
- external fertilisation forms ciliated planula larvae that swim around
- planula larva settle and develop into scyphistoma
- scyphistoma undergoes strobilation releasing young jellyfish (ephyrae)
22
Q
phyla cnidaria, subclass octocorallia
A
- soft octocorals
- 8 pinnate (feather like) tentacles
- 8 longitudinal septa
- thick mesoglea
- internal calcium skeleton
23
Q
phyla cnidaria, subclass hexacorallia
A
- 6 tentacles
- stony sclerotinia corals
- secrete calcium skeleton that the coral sits on top of
- have spriocysts (modified cnidocytes used to catch prey)
24
Q
Ctenophora phyla
A
- comb jellies
- younger lineage than placozoa and cnidaria but less complex, possibly shows secondary simplification
25
Q
characteristics of eubilateria
A
- bilateral symmetry
- triploblastic
- organs
- centralised nervous system with ‘brain’
- cephalisation
26
Q
coelomate phyla
A
- vast majority of eubilateria
- Spiralia, arthropoda, chordata etc
- coelom = fluid filled cavity bounded on both sides with embryonic mesoderm
27
Q
acoelomate phyla
A
- lack coelomic cavity
- e.g. Platyhelminthes
28
Q
Platyhelminthes
A
- basal phylum of eubilateria
- acoelomate
- varied group, no defining synapomorphies
- incomplete gut, one hole (secondary simplification)
- advanced osmoregulatory organs, protonephridia
29
Q
pseudocoelomate phyla
A
- lack true coelomic cavity, only bounded by embryonic mesoderm on one side
- e.g. Rotifera, Nematoda, Priapula
30
Q
Protostomes
A
- determinate development, cell fate is fixed from embryo
- presence of a coelom formed through schizocoely in development
- includes spiralia, ecdysozoa etc
31
Q
Spiralia
A
- protostomes that undergo spiral cleavage, cell twists when it undergoes cell division
- not a true ranked taxon
- includes Mollusca, annelida, platyhelminates etc
32
Q
taxon ecdysozoa
A
- has an exoskeleton that is often calcified
- moults cuticle at least once in life cycle to be able to grow (ecdysis)
- e.g. Phylum arthropoda
33
Q
Phylum arthropoda
A
- non-calcified exoskeleton secreted by epidermis
- procuticle made of chitin
- epicutlicle, waxy lipoprotein kayer for protection
- segmented body with a pair of jointed legs at each segment (tagmatisation)
- complex gut with specialisation
- compound eyes
34
Q
subphyla crustacea
A
- arthropods
- e.g. crabs, lobsters
- head and thorax fused (cephalathorax), covered with calcified carapcace
- 2 pairs of antennae
- nauplii larvae
35
Q
subphyla myriapods
A
- arthropods
- e.g. millipedes, centipedes
- cannot close spiracles so exclusively found in damp environments
36
Q
subphyla hexapoda
A
- arthropods
- e.g. class insecta
37
Q
properties of class insectica
A
- wings (if present) on last 2 segments of thorax
- thorax segments prothorax, mesothorax, metathorax
- tympanal organs
- tracheal system for gas exchange
38
Q
subphyla chelicerata
A
- arthropods
- include arachnids
39
Q
lophotrochozoa taxa
A
- 5 phyla that produce a larvae type called tropophore and possess a lopophore
- platyhelminthes, rotifera, nemertea, annelida, mollusca
40
Q
phylum annelida
A
- includes earthworms, leeches, ragworms, sipubunculans
- most long and thin, adaptation for burrowing
- specialised through gut with regionalisation
- closed circulatory system with blood vessels (as long and thin)
- defining feature is bristles, chaete
- majority have metameric segmentation
41
Q
annelida, metameric segmentation
A
- body comprised of many repeating units
- protostomium = first segment, contains sensory structures
- peristomium = second, has mouth
- metameric segments
- pygmidium = fourth segment, contains anus, organism grows from here
42
Q
properties of phylum mollusca
A
- includes snails, slugs, cephalopods, bivalves
- very diverse
- open circulatory system, haelocoel
- visceral mass, organs concentrated into hump
- mantle = sheet of tissue covering visceral mass
- metanephridia = complex kidney-like filtering organs
- e.g. class gastropoda
43
Q
class gastropoda, shell
A
- vast majority have coiled (typically clockwise) shell containing visceral mass
- useful for predator evasion
- size constrain means they have lost duplicate organs
- attached to shell via collumellar muscle, enables it to contract into shell
- torsion, internal organs rotated 180 degrees, anus is next to head
- some organisms such as nudibranchs have no shell, so have detorted
44
Q
class gastropoda
A
- molluscs
3 recognised groups - prosobranchs (marine)
- opisthobranchs (marine)
- pulmonates (terrestrial)
45
Q
gastropoda, radula
A
- radula = toothed tongue used for feeding
- secreted from radula sac
- rasping mechanism
- supported by muscular odontophore
-can be modified into harpoon drill etc - strongest biological material
46
Q
Deuterostomes
A
- undergo radial cleavage (cell does not twist during cell division)
- development is indeterminate/regulative
- coelom formed through enterocoely (pouches form coelom)
- 1st pore formed anus, 2nd pore formed mouth
- includes Echinodermata, hemichordata and chordata
47
Q
Phylum Echinodermata
A
- include starfish, brittle stars, sea urchins etc
- majority marine
- no head or circulatory system (secondary simplification)
- photoreceptors
- adults have pentaradial symmetry, larvae are bilaterally symmetrical
- water vascular cavity with fluid-filled cavity derived from coelom
48
Q
Echinodermata anatomy
A
- dorsal anus, ventral mouth
- 2 stomachs, cardiac and pyloric
- pyloric stomach branches to the pyloric caeca, with papulae to increase surface area
- madreporite = opening that filters water into vascular system
- pedicellariae = extension of water vascular system to clean surface of animal
49
Q
Phylum hemichordata
A
- halfway between echinodermata and chordata
- lack a notochord, but have a dorsal hollow nerve chord
- bilaterally symmetrical
- pharyngeal gill slits
- open circulatory system
- complete complex gut
50
Q
properties of phylum chordata
A
- non-vertebrates and vertebrates, all non-vertebrates are marine
- notochord = dorsal flexible rod of tissue derived from embryonic mesoderm
- dorsal hollow nerve chord
- bilaterally symmetrical
- pharyngeal gill slits
- postanal tail
- complex gut
- Urochordata, cephalochordata and craniates
51
Q
paedomorphosis
A
- larvae become sexually mature before reaching adult form
- neoteny = retention of larval/embryonic characteristics past reproductive maturity
- progenesis = accelerated development of reproductive organs relative to somatic tissue
- theory of how chordates evolved
52
Q
subphyla urochordata/tunicates
A
- colonial, solitary or pelagic
- e.g. class Ascidacea
53
Q
class Ascidiacea
A
- urochordate
- sea squirts, sessile filter feeders
- heart
- large ciliated pharynx with gill slits (stigmata)
-endostyle (thyroid-like) secretes iodine rich mucous net that traps and digests particles - produces pelagic ‘tadpole’ larvae with notochord present in tail
- notochord degenerates when larvae undergoes metamorphosis
54
Q
cephalochordates
A
- chordates that have all chordate features present in adults
- e.g. branchiostoma
55
Q
properties of craniates
A
- chordates that have a cranium (skull)
- neural crest
- raised metabolism
- heart with at least 2 chambers
- haemoglobin in red blood cells
- kidneys
56
Q
neural crest
A
- embryonic source of many unique craniate characteristics
- pluripotent
- forms peripheral nervous system and myelin sheath
- migrates out of neural plate to form autonomic nervous system, skull, bones etc
- neural plate fuses into neural tube, forms central nervous system
57
Q
fossil origins of vertebrates, conodonts
A
- ‘cone teeth’
- abundant over 300mya
- no jaw
- soft, slender bodies
- probably hunters
58
Q
craniates, class myxini
A
- hagfish
- least derived surviving craniate lineage
- cartilage skull
- lacks a jaw
- lack vertebrae
- snake like swimming through muscles pushing against notochord
- small brain, eyes and ears
- nasal opening connects with pharynx
- keratinous tooth like formations
- mostly bottom dwelling scavengers
- water-absorbing slime glands, slime repulses/suffocates
59
Q
properties of vertebrates, vertebrae
A
- craniates that have a vertebral column
- some vertebrates have vertebrae made of cartilage
majority have vertebrae that enclose the spinal chord and take up role of notochord - supports body
- protects nervous system and brain
- can grow and repair
60
Q
origins of bones and teeth
A
- vertebrate skeleton originally evolved as a structure made out of unmineralised cartilage
- mineralisation may have begun in mouth as feeding mechanisms transitioned from filter feeding to predation, as they then needed a way to break down particles
- earliest mineralised structures found are conodont teeth
- armour is then derived from dental mineralisation
- the endoskeleton then becomes mineralised, starting from the skull
61
Q
fossil origins of craniates, haikouella
A
- emerged 530mya in the cambrian explosion
- not a true craniate as no skull or ear organs
- suspension feeders
- large well formed brain
- small eyes
- muscle segments along body
- respiratory gills in pharynx
62
Q
fossil organs of craniates, Myllokunmingia
A
- more advanced chordate
- regarded at true craniate as has ear and eye capsules as part of skull
63
Q
other properties of vertebrates
A
- skull
- well developed circulatory system
- internal organs suspended in coelom
- 3 part brain (forebrain, midbrain, hindbrain)
- duplication of hox gene complex
- neural crest cells
- underwent another gene duplication after branching off from craniates, transcription factor (DIx genes), possibly lead to innovations in nervous system and skeleton
- aquatic vertebrates have fins stiffened by fin rays
64
Q
class petromyzodontia
A
- lampreys
- oldest living vertebrate lineage
- majority freshwater
- jawless (agnatha)
- development of an oral hood with keratinous teeth
- cartilage skeleton, no collagen, stiff protein matrix instead
- notochord persists in adults
- cartilagenous pipe around notochord, partially encloses nerve chord
- pairs of cartilage projections related to vertebrae extend dorsally
65
Q
petromyzodontia feeding mechanisms
A
- larvae are freshwater suspension feeders
- most adults are parasitic on fish
- round jawless mouth with rasping tongue digests blood and tissues from rasping wound on fish
- anti-coagulant secreted from oral gland
66
Q
later fossil vertebrates
A
- emerged during Ordovician, Silurian and Devonian
- paired fins
- inner ear, 2 semicircular canals for balance
- no jaw but muscular pharynx to suck in other organisms/detritus
- armoured, mineralised bone and spines
67
Q
Gnathostomes, properties
A
- vertebrates that have jaws
- diverse, outnumber agnatha
- additional replication of hox genes (4 clusters)
- other gene clusters duplicate, increasing genetic and developmental complexity
- enlarged forebrain, complex olfaction and vision
- aquatic gnathostomes have a lateral line system ( sensitive to vibration, early versions in some jawless vertebrates)
68
Q
advantages of jaws
A
- active predation, can capture and bite prey
- herbivory
- gripping and slicing food, especially when paired with teeth
- chewing facilitates breakdown and digestion of food
- mouth brooding
- nest building
- mate grasping
- improved gill ventilation
69
Q
evolution of jaws
A
- from branchial arches, skeletal rods that support gills
- first gill arch evolves into upper and lower jaw
- second gill arch supports/suspends jaw
- evolution of hyoid bone that supports tongue
70
Q
gnathostomes, fossil history
A
- emerged mid-Ordovician ~470mya
- paired fins and tail, jaws with large bite force
- placoderms = earliest gnathostomes, plated/armoured, became extinct in early carboniferous E.g.
Dunkleosteus - acanthodians = marine and freshwater organisms in Devonian era, probably sister group to the bony fish (dermal operculum, hyoid attachment, true dermal teeth)
71
Q
gnathostomes, Chondrichythyes class
A
- cartilage skeletons (secondarily derived, traces of bone found)
- skeletons often impregnated with calcium
- sharks , rays and skates
- ratfish/rabbitfish
72
Q
shark properties
A
- fusiform streamlined body shape
- forward propulsion from trunk and caudal fin
- dorsal fin acts as stabiliser
- paired pectoral and pelvic fins for tilt
- no swim bladder
- hylostylic jaw extension, upper jaw is only attached by ligaments so sharks can grip and pull back prey
- cloaca
73
Q
cloaca
A
single external opening for reproduction and waste removal
74
Q
buoyancy in sharks
A
- have no swim bladder so buoyancy is maintained through combination of oil in their liver and continuous swimming
- continuous swimming also forces water across gills, keeping them oxygenated
- when sharks are resting on bottom of sea floor, they open and close jaws and use muscles in pharynx to squeeze and pump water across the gills
75
Q
sensory physiology of sharks
A
- sharp black and white vision
- olfaction through nostrils (dead-end cups)
- electrophysiology for detecting electrical fields around them such as muscle contraction of prey
- no eardrums, entire body transmits sound to inner ear
76
Q
Feeding mechanisms of sharks
A
- The largest sharks and rays are suspension feeders e.g. basking sharks
- Most are carniverous, so have several rows of teeth
- Teeth move to anterior as old ones are lost
- Have a shorter digestive tract than many vertebrates
- Evolved spiral valve to help with digestion of meat, a corkscrew-shaped ridge in intestine that increases surface area and slows digestive transit
77
Q
reproductive strategies of sharks
A
- various reproductive strategies
- oviparous, ovoviviparous or viviparous
78
Q
Oviparous
A
= eggs in protective coat hatch outside body
79
Q
Ovoviviparous
A
= fertilised egg retained in oviduct, nourished by yolk, offspring hatch in uterus
80
Q
Viviparous
A
= offspring develop in uterus, nourished by mother, birth live young
81
Q
Rays
A
- Different lifestyle to sharks
- Mostly bottom dwellers, feed on molluscs and crustaceans
- Flattened shape
- Enlarged pectoral fins for propulsion
- Whiplike tail, many have venomous barbs
82
Q
Osteichthyses
A
- Include bony fish and tetrapods
- almost all have an ossified endoskeleton with a hard calcium phosphate matrix
- 2 clades which evolved in the Devonian era, Actinoperygii and sarcopterygii
83
Q
properties of bony fish
A
- operculum
- swim bladder
- most have bony scales, different to tooth-like shark scales
- mucus secreting glands reduce drag
- lateral line system
- diverse reproductive strategies
84
Q
operculum of bony fish
A
- Protective bony flap covering gill chamber
- Movement of the operculum and contraction of the muscles surrounding the gill chamber draws water through the mouth and pharynx and out between the gills
85
Q
buoyancy of bony fish
A
- maintained by the movement of gases between the blood and the swim bladder
- very efficient
- swim bladder evolved from early lungs in some lineages
86
Q
Actinopterygii clade
A
- ‘ray-finned fish’
- Bony rays support fins, modified for manouvering and defence
- Originated in freshwater then spread to seas
- Many then returned to freshwater
- Some species are both freshwater and sea e.g. salmon
87
Q
Sarcoptergyii
A
- ‘lobe-finned fish’
- Pectoral and pelvic fins have rod-shaped bones surrounded by a thick layer of muscle
- Evolved in brackish water such as coastal wetlands, used lobe fins to swim and ‘walk’ across substrate
3 extant lineages - Coelacanths (actinistia)
- Lungfish (dipnoi)
- Tetrapods
88
Q
Coelacanths (actinistia)
A
- part of Sarcopterygii clade
- Secondarily derived cartilagenous skeletons
- 2 species, originally thought to have become extint ~65mya
89
Q
Lungfish (dipnoi)
A
- part of the Sarcopterygii clade
- Evolved in ocean, now all 6 species are freshwater species in stagnant ponds and swamps
- Have lungs connected to pharynx, come to surface to gulp air
- Also have gills, main gas exchange organ
- Adapted to dry seasons by burrowing in mud
- closest living relatives to tetrapods
90
Q
Evolution of tetrapods
A
~360mya
- Pectoral and pelvic fins evolved into limbs and feet in one lobe-fin lineage
- Supports weight on land and transmits muscle generated forces to ground to allow for locomotion
- Lineage also retained adaptations for aquatic life
Devonian and Carboniferous
- Greater diversity of tetrapods emerged, most still tied to water
91
Q
Acanthostega, evolution of tetrapods
A
~365mya
- Fully formed legs, ankles and digits
- Bones supporting gills
- Tail-rays supporting fin
- Weak pectoral and pelvic girdles
- Possibly unable to support body, hypothesis that it slithered out of water occasionally
92
Q
Other changes to the tetrapod body plan
A
- Head separated from body by neck
- Originally 1 vertebrae, can only move head up and down
- Evolution of second vertebrae allowed side to side movement of head, useful for predator detection
- Bones of pelvic girdle fused to backbone, forces from hind legs can be transferred to the whole body
- Extant tetrapods have no gill slits, embryonic pharyngeal gill slits give rise to other structures
93
Q
class amphibia
A
3 orders
- urodela (tailed)
- anura (tailless)
- apoda (legless)
94
Q
Urodela
A
- Tailed, e.g. newts, salamanders
- Some entirely aquatic, others on land as adults or throughout life
- Walk with a side-to-side bending body motion
- Trot gait, diagonally opposed limbs
- Paedomorphosis e.g. Mexican axolotl
95
Q
Anura
A
- Tailless e.g. frogs
- More specialised for moving on land
- Adults have powerful hind legs and elastic muscles
- Tongue for prey capture and feeding
- Often have distasteful/poisonous toxins for predator evasion
- Colouration for defence, warning/mimicry, camouflage
96
Q
Apoda
A
- Legless e.g. caecelians
- Secondarily derived
- Nearly blind
- Tropical
- most burrow in moist forest soil
- Some species are freshwater
97
Q
Life stages of amphibians
A
- Anuran larval stage = tadpole (aquatic herbivore)
- Metamorphose into adults, legs, lungs, external eardrums develop, digestive system adapts to carnivory, gills (and lateral line system in may species) disappear
- Urodele and apodan larvae are carniverous and look like the adults
98
Q
Habitats of amphibians
A
- Most live in damp habitats or burrow under vegetation
- Keeps skin moist for gas exchange
- Some terrestrial species lack lungs (breathe only through skin and through oral cavity
99
Q
Other adaptations of tetrapods for terrestrial life
A
- a ribcage to ventilate lungs
- More efficient than throat based respiration
- Amphibians supplement breathing through the skin with breathing with the buccal cavity
- May have allowed amniotes to abandon respiration via their skin
- They then could evolve less permeable skin, giving them more ability to conserve water and therefore live on land
100
Q
reproductive strategies of amphibians
A
- Most have external fertilisation
- Lay shelless eggs in water/a moist environment
- Won’t lose water through dessication
- Various types of parental care including mobile nurseries (back, mouth, stomach brooding)
- Some ovoviviparous, some viviparous
101
Q
main characteristic shared by amniotes
A
- evolution of a terrestrially adapted egg = amniotic egg
- 4 extraembryonic membranes: yolk sac, allantois, amnion, chorion
- Most reptiles and some mammals also have a shell (leathery or calcified)
- Unclear evolutionary reasons, but may have allowed size and strength of egg to increase
102
Q
properties of amniotic egg
A
- shell, protection against damage/ water loss, permeable for gas exchange
- Amnion and chorion (surrounding embryo) are vascularised, allowing for gas exchange
- allantois allows for excretion of waste and is also vascularised
- albumen for nutrition and protection
- yolk for nutrition
103
Q
Amniote fossils
A
- Ancestor ~370mya
- Found in dry climates
- Herbivores (grinding teeth)
- Predators
- no fossils of amniotic eggs found
104
Q
properties of reptilian clade
A
- Keratinous scales, protection against damage and dessication
- Most lay shelled eggs on land, therefore have internal fertilisation
- Many are viviparous
- Most are ectothermic, behavioural thermoregulation
- Birds are endothermic, metabolic thermoregulation
105
Q
Earliest living reptiles
A
- Oldest fossils ~310mya
Parareptiles - Large, stocky, quadripedal
- Plated for defence
- Extinct by end of triassic ~200mya
106
Q
Diapsids
A
- Diversified as parareptiles were dwindling (Triassic)
- Most obvious derived diapsid character = pair of holes each side of the skull behind eye socket (temporal fenestrae)
- 2 main lineages, Lepidosaurs and Archosaurs
107
Q
extinct lepidosaurs
A
Marine reptiles e.g. giant mososaurs
108
Q
extant lepidosaurs
A
- Tuataras, lizards and snakes
- Modified diapsid skull
- 2 extant lineages, Sphenodontians and Squamates
109
Q
Sphenodontians
A
- Tuataras, 1 species
- Lizard-like reptiles
- Relatives ~220mya over many continents
- Now only 30 islands off New Zealand, not found on main island due to rodent introduction
- ~50cm
- Eat insects, small lizards, bird eggs, chicks
110
Q
squamates
A
- lizards and snakes
- ~7900 species
111
Q
Lizards
A
- Mostly small
- Jaragua lizard is 16mm long
- Komodo dragons ~3m (Indonesia)
- Hunts deer and stalks wounded prey, toxins in bite
112
Q
snakes
A
- Legless (secondarily derived
- Some species show remnants of pelvic girdle and limb bones
113
Q
movement of snakes
A
- Normal, lateral bending (Sidewinding, concertina)
- Rectilinear, grips ground with belly scales and pushes self forward, useful for prey ambush
114
Q
Extinct archosaurs
A
- On land dinosaurs diversified into 2 main lineages
- Ornithischians
- Saurischians
115
Q
Ornithischians
A
- Herbivores
- Many have anti-predator defences such as tail clubs and horned crests
116
Q
Saurischians
A
- Long necked giant tree browsers
- Theropods = bipedal carnivores
e.g. Tyrannosauras rex, bird ancestors
117
Q
Extant archosaurs
A
Crocodilians, 23 extant species
(Alligators, crocodiles and gharials)
118
Q
evolution of crocodilians
A
- Emerged during Triassic
- Early crocodilians were small, terrestrial quadripeds with long slender legs
- Later adapted to aquatic habitats, evolution of upturned nostrils
119
Q
properties of tesdudines
A
- Turtles, terrestrial and aquatic species
- Anapsid, no temporal fenestra
- Box-like shell
- Head retraction
Earliest turtles could not retract heads
Retraction mechanisms evolved independently
Pleurodires
Fold neck horizontally
Cryptodires
Fold neck vertically
120
Q
testudine shells
A
- Most are hard for defence
- Clavicles and ribs fused to carapace (dorsal side of shell)
- Plastron = ventral side of shell
- Absence of transitional fossils to show evolution of shell
- Molecular data suggests that testudines are related to crocodilians
- Plates of archosaurs possibly became more extensive and started to form a shell
- Other data suggests they are perhaps a sister group to birds
121
Q
Head retraction in testudines
A
- earliest turtles could not retract heads
- Retraction mechanisms evolved independently
- Pleurodires fold neck horizontally
- Cryptodires fold neck vertically
122
Q
origin of birds
A
- Cladistic analysis from fossils shows they evolved from theropods
- Feathered theropod fossils show feathers evolved before flight
- Feathers possibly for insulation, mating or camouflage
123
Q
Evolutionary theories of flight in theropods
A
- Cursorial (ground-up): small running dinosaurs gained lift from feathers, aided predatory lifestyle
- Arboreal (trees down): dinosaurs climbed trees and glided, aided by feathers
124
Q
Theropods evolved into birds by 150mya
A
Archaeopteryx:
- Feathered wings
- Ancestral characteristics (teeth, clawed digits in wings, long tail)
Later Cretaceous bird fossils:
- Lost teeth and clawed forelimbs
- Acquired short feathered tail
125
Q
extant birds
A
- neornithese clade
- 11000 species
- 32 orders
- variety of forms
- most have similar fusiform body shape adapted to flight
- beak shape highly adapted to diet
- foot structure highly adapted to lifestyle
126
Q
neornithese clade, derived characteristics and modifications for flight
A
- wings with feathers made of beta keratin
- no urinary bladder
- females of most species have one ovary
- males have small gonads apart from during breeding season
- toothless (secondarily derived)
127
Q
Advantages of flight
A
- Enhances hunting and scavenging
- Escape mechanism
- Ability to migrate long distances
128
Q
birds, evolution of high metabolic rate
A
- as flight is energetically expensive
- Evolution of endothermy
- Feathers and fat for insulation
- Lungs have tubes to elastic air sacs, improving respiration
- 4 chambered heart
129
Q
Order Sphenisciformes
A
- Flightless penguins
- powerful pectoral muscles
130
Q
Ratites
A
- In order Struthinioformes
- Flightless, adaptations for cursorial locomotion include long legs
- Sternal keel absent (attachment for flight muscles)
- Small pectoral muscles
E.g. ostrich, emu, kiwi etc
131
Q
synapsids
A
- evolutionary origin of mammals
- one lowered temporal fenestra on either side of skull
- 3 radiations of lineage
132
Q
1st radiation of synapsid lineage
A
- Palaeozoic era
- evolution of pelycosoaurs (primitive)
- include sailbacks and sphenacodontids
- Beginning of 3 boned middle ear in sphenacodontids
133
Q
2nd radiation - Paleozoic
A
- evolution of therapsids (more derived)
- Upright posture, limbs drawn in so they can be used like levers, also helps to free up respiratory muscles
- Increased jaw musculature
134
Q
evolution of cynodonts
A
- Triassic
- Most derived therapsid, but still not a true mammal
- E.g. Triethelodon
- Size reduction to rat sized
- Evidence of endothermy
- turbinate (nasal) bones, increases airflow, reduces water loss
- Secondary palate, can swallow and breathe at the same time
- Reduced ribcage restricted to anterior allowed evolution of diaphragm
- Still conflict between hearing a chewing as jaw bone involved in channeling sound (mammalian inner ear bones evolved from synapsid jaw joint)
135
Q
3rd radiation of synapsids
A
- Cenozoic
- Evolution of true mammals
- Earliest mammals very small, shrew sized
- Lived alongside dinosaurs until late Triassic
136
Q
Features of early mammals
A
- Small, <100mm
- Nasolacrimal duct
- Evolution of fur for insulation
- Precise occlusion = molars fit together, helps with mastication
- Diphyodonte = two sets of teeth
- Not good at evaporative cooling
- Ears lack pinna (outer part)
- Low metabolism, suited to nocturnal lifestyle (cooler at night)
- Probably insectivorous and solitary
- Large olfactory lobes. more sophisticated sensory processing
- start of evolution of lactation
137
Q
nasolacrimal duct
A
- Channel between tear ducts and nasal cavity
- Important for pheromones, olfactory sensing and cleaning eyes/fur
- characteristic anatomical feature of early mammals
138
Q
early mammals, evolution of lactation
A
- No nipples, secreted on to fur
- Not yet a food source for young
- Antimicrobial, possibly for protecting eggs laid in nest
139
Q
key features of mammals
A
- Hair/fur for insulation, communication, camouflage, sensation
- lactation and suckling
- variety of skin glands
140
Q
mammalian skin glands
A
- Variety of skin glands
- Apocrine, eccrine and sebaceous
- Functions include lubrication, waterproofing, olfactory communication and thermoregulation
- Mammary glands evolved from skin glands
141
Q
Suckling
A
- Unique mammalian feature
- reflex
- Must be able to make a seal with mouth and breathe and swallow at the same time
- Facial muscles required
- evolution of mobile lips and cheeks, used for other functions like communication later in evolutionary history
142
Q
benefits of lactation and suckling
A
- Paternal care not required
- Offspring do not rely on seasonal food supply
- Provides care outside uterus (marsupials)
143
Q
evolution of lactation and suckling alongside precise occlusion and diphyodonty
A
- lactation and suckling evolved before precise occlusion and diphyodonty
- Diphyodonty precedes precise occlusion
- Feeding on milk requires no teeth so reduces number of sets of teeth needed
- Having no teeth allows jaw growth and eruption of permanent teeth in an almost adult sized jaw
144
Q
major mammalian lineages
A
- Allotheria (extinct multituberculates)
- prototheria
- theria
145
Q
prototheria
A
- infraorder Ornithodelphia
- order monotremata
- oviparous (lay eggs)
- cloaca
- shoulder girdle has retained ventral elements, secondarily derived sprawling stance
146
Q
Platypus
A
- prototherian
- 1 species
- Semi-aquatic
- Eat aquatic invertebrates
- Australian
- Venomous spurs
- Leathery ‘beak’ with electrosensitive pores
147
Q
Echidna
A
- prototherian
- Insectiverous, long sticky tongue
- Short-nosed echidna
1 species
Australian
Eats ants and termites - Long-nosed echidna
3 species
New Guinea
Eats earthworms
148
Q
Metatheria
A
- Traditionally order marsupiala, now 4 recognised orders
- Geographically split
- 1 order in New World (Americas)
- 3 orders in Australia
- Inflected jaw
- Epipubic bones retained
- Primitive dental formula: I5/4 C1/1 P3/3 M4/4
149
Q
Australian methatherian orders
A
- Dasyurids, carnivores e.g. Tasmanian devil
- Peramelids, insectivorous e.g. bandicoots and bilbies
- Diprotodontians, modified lower incisors, 3 radiations: possums, koalas, kangaroos
150
Q
theria
A
- metatheria and eutheria
- Viviparity = give birth to live young
- Nipples
- At least 2.5 coils of cochlea (improved hearing)
- Pinna = external ears
- Tribosphenic molars
- Urogenital and alimentary openings
- Derived shoulder girdle, ventral elements lost, scapula moves independently
- increases stride lengths, allows for specialised gaits
151
Q
Eutheria
A
- May be referred to as placental mammals, but some metatheria have modified placentas
- Rapid radiation so phylogeny obscure
- Auditory bulla surrounds ear
- Herbivores had a post-orbital bar that stabilises the jaw
- Lost epipubic bones, possibly aiding the birth of larger offspring
- Primitive dental formula: I3/3 C1/1 P4/4 M3/3 (usually fewer incisors and molars than metatherians, but more premolars)
152
Q
Biogeography of mammals
A
- Radiation peaked in cenozoic era as land masses separated
- vicariance and dispersal
153
Q
Vicariance of mammals
A
- Populations separated by physical processes
- Distinct mammalian faunas on each continent
154
Q
Dispersal of mammals
A
- Active movement of populations
- Mammalian faunas mixed when continents rejoined
155
Q
Convergent evolution of therians
A
- Eutherian and metatherian mammals share body forms and habits
- Evolved similar characteristics to suit similar environmental conditions, no common shared ancestors
156
Q
Humans, evolution of bipedal locomotion
A
- Frees up upper limbs
- Energy efficient running
- Ideal head position to scan horizon
