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
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
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
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
