Lecture 1 DA Introduction Flashcards
On a phylogenetic tree, what are nodes?
Points where a species seperates into two, into branches.
What is a species at a node of a phylogenetic tree called?
Inferred species.
What are sister taxa?
Those species more closely related versus the rest of the tree.
What are evidences needed for constructing phylogenetic trees (4)?
Fossil records Traits: -genetic sequences -comparative -architecture/morphology -development
What is an ancestral character? Does it reveal relationships within the group?
Character shared by all taxa in a grouping. Doesn’t reveal relationships.
What is a derived character? Does it reveal relationships within the group?
Character that arose after an ancestor. Does reveal evolutionary relationships.
What is a shared-derived character? Does it reveal relationships within the group?
A synanomorphy, shared by all descendants of an ancestor due to common descent.
What is a synanomorphy?
A character shared by all descendants of an ancestor due to common descent.
How are synanomorphies useful for phylogenetic trees?
Used to define clades/groups.
What is homology?
Similar structure due to a common ancestor.
What is analogy?
Structures that are only superficially similar, and not due to a common ancestor.
How do analogous structures arise?
Via convergent evolution.
What are some ways species can be grouped?
Based on cell orginisation - uni/multicellular
Based on body symmetry
Number of embryonic tissue levels (ecto/endo/meso)
What is a protostome?
The first hole in embryological development becomes the mouth.
What is a deuterostome?
The first hole in embryological development becomes the anus.
What is the problem of using solely deuterostomes and protostomes as a classification in making phylogenetic trees?
Gives conflicting phylogenies.
What is a monophyletic clade?
A grouping including all the descendants of a common ancestor.
What is a paraphyletic clade?
Grouping that doesn’t include all descendants of a common ancestor, will have some from another ancestor as well, but not that ancestor itself.
What is a polyphyletic clade? How do they arise?
Neither a para or monophyletic clade, happens due to convergent evolution.
What are protozoa like?
Eukaryotic, mostly unicellular and some colonial.
Are protozoa motile?
Yes, via flagella and cilia.
What are metazoa like?
Eukaryotic and multicellular
Do metazoa have differentiating cells?
Yes
Which phylum do sponges belong to?
Porifera
Of the three domains of life, which two are more closely related and why?
archaea and eukarya, due to the presence of histones.
What did animals arise from?
Choanoflagellates
Animal and fungi kingdoms came from which protozoa?
Opisthokonta
What are choanoflagellates like?
Loose association of cells, are colonial and genetically identical.
Do choanoflagellates have cell differentiation?
No
Can individual choanoflagellates of a colonial group survive on their own?
Yes
What are choanoflagellate sfunctionally very similar to?
Sponges.
How do choanoflagellates feed?
Filter feed by beating flagella to drive a current through a collar of filtering microfibrils.
What is the simplest metazoan?
Phylum porifera
Do porifera cells have differentiation?
Yes, but only some
Do phylum porifera have any organs?
No
Are phylum porifera symmetrical?
No
How do phylum porifera filter feed?
Via choanocytes, very similar to choanoflagellates.
Do phylum porifera have totipotent cells?
Yes
If a sponge is broken down, can a single cell survive on its own?
Yes
If two different sponges were broken down to culture and mixed, what happens?
They will seperate from each other and reform.
What is the environment of sponges and are they motile?
Entirely aquatic, and motile.
They are anchored and called sessile.
Where do choanocytes line?
The inside of cavities of sponges.
What forms the outer wall of a sponge?
Pinacocyte.
What is the mesohyl?
Space between a pinacocyte and choanocyte.
What cell can be found within the mesohyl?
Archaeocyte.
What is an archaeocyte, and is it motile?
Totipotent sponge cells, and is motile.
What is a spicule?
Reinforcement of sponges
What is a spicule made of, and what secretes it?
Caclium carbonate or silica.
Secreted by archaeocytes.
What is spongin and what is it made of?
Reinforcement made of collagen.
What is the architecture of spongin?
Arent interconnected, but do overlap for reinforcement.
What are the three sponge body architectures?
Asconoid
Syconoid
Leuconoid
Describe asconoid architecture.
Water enters through pores called ostea, into a central cavity, called the spongocoele, and exits out the top called osculum.
Describe syconoid architecture.
Like asconoid, but the walles are folded like villi, increasing surface area covered by choanocytes.
Looks like an inverted intestine.
What is a spongocoele?
Central cavity to which ostea lead.
What is an ostea?
Pores through which unfiltered water is taken in.
What is an osculum?
Main exit through which filtered water exits.
What is the simplest sponge body architecture?
Asconoid
What is the least common sponge body architecture and why?
Asconoid, as it is limiting due to increasing surface area ratio.
How can asconoid sponges adapt their architecture?
Avoid being spherical, ie branching, flattening
Where does filtering take place in asconoid sponges?
In the spongocoele.
Does filtering take place in the spongocoele in synocoid?
No, it takes place between the folds of the wall where the choanocytes are found.
Describe the leuconoid architecture.
Body is a solid mass, with many canals within it, entering through many ostea and exiting through many oscula. Has no single spongocoele in the middle.
Which of the three sponge architectures has the greatest surface area?
Leuconoid.
Which of the three sponge architectures reaches the biggest mass and is the most common?
Leuconoid.
Do leuconoids have spongocoeles?
No, they dont. They can have false spongocoeles in which the walls form a tubular, spongocoele-like structure, but isnt really one.
Can sponges reproduce asexually?
Yes, if a piece isbroken off, it will regenerate.
What are gemmules? Is this sexual or asexual?
Cyst-like structures that can form dormant cysts. Asexual.
Can sponges reproduce sexually? Explain.
Yes, they are hermaphrodites (monoecious), and gametes are produced by archaeocytes.
Sperm is shed into the water, but eggs are retained. Sperm of other sponges are filtered, recognised, engulfed but not digested. They revert to an archaeocyte, enter the mesohyl, differentiate to a sperm cell, recognise the egg, and fertilise it.
What forms after sexual reproduction in sponges?
Parenchymula larva.
What is a free swimming larva called?
Blastula/blastocoele.
What happens when a blastula/blastocoele finds a suitable anchor?
Invaginates, develops ostea, canals and oscula.
When a blastula invaginates, is it gastrulating? Why?
No, this isnt gastrulation. Sponges dont have tissue layers, where gastrulation is tissue layer development.
How are classes of sponges derived?
Derived via spicule and spongin architecture, rather than sponge body architecture.
What are the three classes of spones?
Calcarea
Hexactinellida
Desmospongiae
Homoscleromorpha
What is the spicule architecture and water environment of calcarea?
CaCO3 spicules, small sponges, entirely marine.
What is the spicule architecture and water environment of hexactinellida?
Silica spicules, ‘glass’ sponges, deep sea.
What is the spicule architecture and water environment of calcareadesmospongiae?
Can have silica spicules, spongin fibres or both, and also both fresh and sea water.
What body architecture do all desmospongiae have?
Entirely leuconoids.
Which sponge class forms ~80% of all sponge species?
Desmospongiae.
What is the spicule architecture and water environment of homoscleromorpha?
No skeleton, or silica spicules.
Small group and marine.
What can be said of the pinacoderm of homoscleromorpha?
Considered to be truee tissue, with proper cell-cell communication.
How are sponges useful regarding their toxin release?
They are compounds that cannot be synthesised, and harvesting from sponges is unsustainable due to minute quantities produced.
How are the toxin compunds of sponges thought to be produced?
By symbiotic bacteria, rather than the sponges themselves.
Besides toxin study, what is another use for sponges?
Bath sponges.
Are all sponges filter feeders? Explain.
Yes, but there is an exception;
A carnivorous sponge, with really long spicules to snag prey, which it then surrounds and digests.
What is the first metazoan?
Phylum placozoa.
What is the cell structure Is it motile? How does it feed?
Is only 2 cell layers thick, and covered in cilia for motion, Simply engulfs food particles.
Are the cell layers of phylum placozoa true tissue?
Yes.
