L2 - Taxonomy and Asymmetrical animals Flashcards
What are the two divisions to the Linnaean system?
Binomial and hierarchical
What is the theory of evolution?
Species are not immutable - they change or adapt. The agent that produces these changes is natural selection.
What is the definition of phylogeny?
Evolutionary history
What is the definition of systematics?
Study of biology in evolutionary context
What is the definition of cladistics?
An examination of the order in which organisms evolved - it draws phylogenetic trees called cladograms
What is Taxon 1?
Monophylogeny
What is Taxon 2?
Paraphylogeny
How can we study evolution and produce these cladograms?
By examining the structure (morphology) of fossils
What are newer techniques for studying evolution?
Evolution is all about genetic change, e.g. mutations - sequence differences in nucleic acids leading to changes in protein seq. Nucleic acid sequencing - usually 18S rRNA. Developmental biology e.g. Hox genes that regulate development, this is known as molecular evolution.
Do new techniques for studying evolution tell us the time of divergence?
Perhaps - if evolution occurs at a linear rate
What is an example of a molecular clock?
Evolution of cytochrome c. In this case the molecular clock keeps good time.
How did animals first evolve?
Most likely evolved from choanoflagellates. Consist of choanocytes, unlike multicellular animals, all cell function similarly and separately.
What are the theories of animal evolution?
Colonial protist, an aggregate of identical cells. Hollow sphere of unspecialised cells, beginning of cells specialisation, infolding, digestive cavity, grastrula-like ‘protoanimal’
How do true animals differ from choanoflagellates?
Multicellularity - integration of cells (communication) and differentiation. Germ cells - spermatozoa and eggs - haploid. Collagen - a glycoprotein to hold cells together
What are some examples of Parazoa?
Porifera - sponges, Placozoa - ‘flat animals’
Stage 1 of True animals from choanoflagellates?
Parazoa - animals with no tissue differentiation - gave rise to modern day sponges. Eumatazoa - all other animals with true tissues
Stage 2 (Radiata) of True animals from choanoflagellates?
Radiata - Animals with radial symmetry and diploblastic larvae. Diploblastic - ectoderm (outer layer) and endoderm (gut etc)
What are some examples of Radiata?
Cnidaria - hydra, jellyfish, sea anenomes, corals. Ctenophora - comb jellies.
Stage 2 (Bilateria) of True animals from choanoflagellates?
Bilateria - animals with bilaterial symmetry and triploblastic. Triploblastic - ectoderm (outer layer), mesoderm (connective), endoderm (glandular).
What are the steps in development in bilaterial animals and formation of 3 layers?
Zygote, Cleavage, B-cell stage, Cleavage, Blastula (hollow ball), gastrulation, gastrula (blastopore, ectoderm, endoderm, mesoderm, archenteron)
What makes up the Ectoderm (outer layer)?
Cells of the epidermis, neuron of brain, neuron of peripheral nervous system.
What makes up the Mesoderm (middle layer)?
Cells of the notochord, skeletal muscle cells, kidney tubule cells, red blood cells
What makes up the Endoderm (inner layer)?
Pancreatic acinar cells, thyroid follicular cells, lung alveolar cells
What do the triploblastic layers need to be considered in?
Their complexity in the bauplan.
What are the three further classifications, based on how the mesoderm is organised within the body?
Coelamate animals, Pseudocoelomate animals, Acoelomate animals.
How is the Mesoderm organised in Coelomate animals?
Coelom (fluid filled space) lined by mesoderm
How is the Mesoderm organised in Pseudocoelomate animals?
Tissue not completely lined by mesodermal cells
How is the Mesoderm organised in Acoelomate animals?
No coelem
Stage 3 of True animals from choanoflagellates?
Protostomes - molluscs, annelids, arthropods
Deuterostomes - echinoderms, vertebrates
What are the steps in stage 3 of True animals from choanoflagellates for Protostomes?
Spiral cleavage, 4-cell embryo with cell excised, development arrested and determinate cleavage, blastopore becomes mouth.
What are the steps in stage 3 of True animals from choanoflagellates for Deuterostomes?
Radial cleavage, 4-cell embryo with cell excised, normal embryo and normal embryo, indeterminate cleavage, blastopore becomes anus
Stage 4 of True animals from choanoflagellates?
Lophotrochozoa - consists of lophophorates, annelids, molluscs
Ecdysozoa - are named for ecdysis (moulting). All secrete a non-living cuticle, strongly supported as a separate clade by molecular evidence such as similarities in DNA.
Stage 5 of True animals from choanoflagellates - What are the sub-kingdoms of Parazoa?
No true tissues, collection of cells. Come between colonial protists and metazoans, sponges show some cell differentiation. Consists of two phyla - Porifera (sponges) ~10,000 spp or Placozoa
What is Placozoa?
It is a sub-kingdom of Parazoa, basal form of inveterbrate, simplest in structure of all non-parasitic metazoa. Classed into a single species, Trichoplax adhaerens, although there is enough genetic diversity that thetre are probably a lot of morphologically similar species
What is Porifera?
It is a sub-kingdom of Parazoa, sessile with porous bodies and choanocytes, lack a true tissues and organs, and have no body symmetry, mostly suspension/filter feeders, a few carnivores. Have water intake and outlet openings connected by chambers lined with cells with whip-like flagella (choanocytes). Mostly marine, a few freshwater. Range from tidal zones to >8,800m depth. Bodies consist of a non-living jelly-like mass sandwiched between two main layers of cells.
What are the layers in Porifera called and what are their functions?
Pinacoderm - Outer layers, made up of Pinacocytes. Atrium - cavity in the centre. Pores formed by porocytes, cells which surround a ‘hole’ = Ostium. Atrium lined with choanocytes. Gelatinous layer between pinacoderm and choanocytes = Mesohyl. Wandering cells in mesohyl = Amoebocytes, which ingest food and secrete spicules. Spicules of silica or calcium carbonate. Spongin = similar to collagen, forms organic skeleton
What are the three basic body plans in Porifera? And in what way are they classified?
Asconoid, syconoid, leuconoid. Classified morphologically ; related to degree of folding complexity.
What is the Asconoid body plan in Porifera?
Simplest radial form ; tubular shape, relatively small, <10cm length.
What is the Syconoid body plan in Porifera?
Syconoid sponges have more elaborate infoldings of the body wall
What is the Leuconoid body plan in Porifera?
Highly infolded ; possess flagellated chambers
What are the four classes of Porifera? And how are they classified by?
Calcarea, Hexactinellidae, Demospongiae, Homoscleromorpha. Classified based mainly on skeleton composition
What is Calcarea?
A class of Porifera, calcareous sponges, body form can be Asconoid, syconoid, leuconoid. Spicules are calcite and may be individuals or large masses, massive exoskeleton made of calcite, no spongin fibres.
What is Hexactinellidae?
A class of Porifera, glass sponges, body form is Leuconoid. Spicules are silica and may be individuals or fused, no massive exoskeleton, no spongin fibres.
What is Demospongiae?
A class of Porifera, majority of sponges, body form is Leuconoid. Spicules are silica, massive exoskeleton in some species made of aragonite, spongin fibres are in many species.
What is Homoscleromorpha?
A class of Porifera, tropical sponges, body form is Leuconoid. Spicules are silica, no massive exoskeleton, spongin fibres are in many species.
What are the Parazoa (Porifera and Placozoa)?
Asymmetric
What are the two branches of Eumatazoa? And how are they classified?
Bilateria and Radiata. Based on their symmetry and embryonic development.
What are Bilateria properties (Eumetazoa)?
Bilateral symmetry, have surfaces : dorsal (upper), ventral (lower), anterior (head), posterior (rear/tail/arse end), left and right, cephalisation, (sensory structures at anterior end)
What are Radiata properties (Eumetazoa)?
Radial symmetry, have surfaces : oral (mouth), aboral (no mouth)
During embryology what does the Radiata develop?
2 germ layers : the ectoderm & endoderm = diploblastic
During embryology what does the Bilateria develop?
3 germ layers : ectoderm, endoderm & mesoderm = triploblastic
