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a group of organisms that form a clade, consisting of a last common ancestor and all of its descendants.
A group that contains its last common ancestor but does not contain all the descendants of that ancestor
A uniquely derived shared character.
character that also exists outside the taxon of interest because it is ancestral.
A taxonomic group of any rank, such as a species, family, or class.
organisms or groups of organisms that share an immediate common ancestor and are placed in the same taxonomic group
a monophyletic group.
A point at which lines or pathways intersect or branch; a central or connecting point
segment of a stem between two nodes
represented as a node which has more than two immediate descending branches
hypothetical last common ancestral interbreeding population of the taxon labeled at a tip of the cladogram.
Numerical Taxonomy. How does numerical taxonomy group organisms?
- A method of classification by which similarity is determined by considering phenetic characters (characters responsible for an entity's appearance). Characters are selected without regard to an entity's evolutionary history.
- attempt to classify organisms by observable traits
- The problem is that as a wide variety of statistical programs were developed to analyze the data, they would give different answers. And different investigators would come up with different answers, and this was what the method was originally developed to avoid.
Cladistics. How does cladistics group organisms?
- A classification method in which the members of a taxa have been grouped together on the basis of phylogenetics, -the members of the taxa share a more recent common ancestor with each other than with the other members of any other group
- Grouped by genetics
How/Why do plesiomorphies make paraphyletic groups look alike?
Key Concepts of the Tree thinking challenge?
Name some of the ways that the biological trees do not represent phylogenetic trees as well as we think they should.
- Biological trees are thicker at the base then they are at the tips, while evolution actually represents a single species at any point in time continues to branch out.
- Biological trees oriente themselves toward the sun whilest evolution is actually a more random process.
- derived from common decent
- share external positions and connections
- share internal structure and
- intermediates that bridge disparate characters
What is "insertae sedis", and which taxa are we relatively unsure of where they fit on the tree.
- a taxonomic group where its broader relationships are unknown or undefined
- Placazoa-the argument in this case is whether the derived features that define eumetazoans were secondarily lost in Placozoa (Which would make them eumetazoans, or whether they never had them
Why is Placozoa so hard to place in the
Whether the derived features that define eumetazoans were secondarily lost in Placozoa (Which would make them eumetazoans), or whether they never had them
What are the arguments for a basal position vs.
a more derived position?
- 1) There are colonial freshwater choanoflagellates called Proterospongia. These things, although not a direct ancestor of sponges, give us a look at how sponges might have evolved from colonial flagellated eukaryotes.
- 2) There are fossil sponges that are over 600 million years old. These are the oldest animal fossils.
- 3) Molecular phylogenies have placed sponges at the base of the metazoan tree. There have been conflicting studies about the monophyly of sponges, but a recent and large study has found Porifera to be monophyletic.
What are the synapomorphies for Metazoa?
- Multicellularity (but other eukaryotes also multicellular)
- Extracellular matrix (ECM) that provides structural support
- Intercellular cytoplasmic communication
- Septate and desmosomal junctions between cells
- Extracellular production of cross-linked collagen
What are the synapomorphies for Eumetazoa?
- expanded gut
- Embryonic layers
- Bodies with definite axes
Synapomorphies for Porifera
- an aquiferous system with external poresmineral spicules
- high cellular mobility and totipotency
Synapomorphies for Cnidaria
- Possess true tissues organized into germ layers, and an embryo that goes through a gastrula stage
- Gut, nervous system, distinct cell layers
Synapomorphies for Echinodermata
What is wrong with using the presence or
absence of a coelom for classification?
What happened to the 5 kingdom
It is non-monophyly. First, it was discovered that not all prokaryotes are alike, and they are split into massively diverse groups, Archaea, and Bacteria. Then, protists, and “plants” are not monophyletic.
What are the three groups of sponges?
- Calcarea: Calcium carbonate
- Hexactinellida (glass sponges): siliceous
- Demospongia (90% of all): Silica with spongin
What are the four groups of Cnidarians?
- Hydrazoa- Hydra and Physalia (Portuguese man-of-war.)
- Scyhozoa- True Jellies
- Cubazoa-Box Jelly Fish
- Anthozoa-Sea anemonies and corals. The ‘flower’ animals
What are the five groups of Echinodermata?
- Asteroidea- Sea stars, starfishes
- Ophiuroidea (Ophio =snake) -Brittle stars (=serpent stars), basket stars
- Echinoidea (Echin = spiny)- urchins, sand dollars, sea biscuits
- Holothuroidea (holothur =polyp) -Sea cucumbers
- Crinoidea- sea lillies
A multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid or mollusk
Animals in which the first opening that appears in the embryo becomes the anus while the mouth appears at the other end of the digestive system. Main groups include chordates and echinoderms.
- 1. 543-490 mya
- 2. 290-248 mya
- 3. 206- 144 mya
- 4. 99-65 mya
- 5. 543-248 mya
- 6. 248-65 mya
- 7. 65- present
How old is the Earth?
How long ago did the metazoan body plan form? About what era?
- 1 BYA-500 MYA
- Most likely the before or the very begining of the Paleozoic
The outermost layer of cells or tissue of an embryo in early development, or the parts derived from this, which include the epidermis and nerve tissue
the inner germ layer that develops into the lining of the digestive and respiratory systems
the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue
Which groups of animals have all three embryonic layers?
- Cnidarians and Sponges diploblastic (lack mesoderm)
- Protostomes and Deuterostomes are triploblastic
Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure known as the gastrula.
- Phagocytosis (immune system)
- Totipotent (forms other cell types)
- Movement of water and food filtering
- located inside lining of spongocoel
- Outter layer of spong, can expand and contact to alter sponge size
- Produce collagen
Pores that allow for water enterance only
Openings in the spone which allow for water exit only
Made of choanocytes
large, central cavity of sponges
Chanocytes and Choanoflagellates relationship
- Choanocytes are responsible for the movement of
- water and much of the filtering of food in sponges. – developed from choanoflagellates (flagellated cells)
How does water move in a sponge? Where does the water enter, and where does it exit? What draws it in?
outside -> ostium -> incurrent canal -> prosopyle -> radial canal-> apopyle -> atrium -> osculum -> outside
Flagellated cells in the ostium create suction pressure.
Asconoid, how many oscula?
- The choanocytes are restricted to the wall surrounding the atrium, flagellated spongocoel is a simple tube, perforated by pores.
- The porocytes connect the atrium with the outside
- Have multiple inlet pores (ostia), but they have
- only one exit—the osculum
Syconoid, how many oscula?
- The walls around the atria of syconoid sponges are folded.
- Each fold becomes a radial canal.
- These canals are lined with choanocytes.
- This increases the surface area and hence the density of choanocytes in the sponge.
Leuconoid, how many oscula?
- Shaped kind of like an asymmetrical rock/lump.
- The mesohyl proliferates, leading to a proliferation of small, flagellated chambers lined with choanocytes.
- Loss of the spongocoel (atrium), replaced by a large number of excurrent canals, and multiple oscula.
How do sponges eat?
- Pull water in (chanocytes)
- Separate the energy containing carbon compounds, such as algal cells, from the inorganic, or mineral, content in the water.
- Archeocytes engulf large molecules
Placozoans are the most simply organized animals we know
of. Whether this simplification is ancestral or secondary, we do not know.
Can secondary loss be a synapomorphy?
- Attempt to explain evolution of metazoans from protists. Flagellated protozoans unite to form a plate-like metazoan organism.
- The one-layered protist form evolves to the two-layered “placula.”
- Cells of the upper layer form
- the ectoderm, while cells of the lower layer (orange) adopt a feeding function and later invaginate to form the entoderm
1. Do Sponges have sexes?
3. From which cells do their gametes come from and
4. how do they get together?
- 1. Yes but most are hermaphrodites
- 2. No organized gonads
- 3. Archaeocytes and/or choanocytes become egg precuser and are phagocytized by nurse cells (archaeocytes) which becomes an egg.
- Sperm develop from choanocytes
- 4. Spermatozoa are ejected from the osculum and travel through the water, ending up at another sponge and fertilization occurs internally in the mesophyl
What are the three mechanisms of asexual reproduction?
- 1. Budding
- 2. Fragmentation
- 3. Gemmules (spongillidae): Gemmule formation is primarily among freshwater sponges in order to survive difficult seasons
What are gemmules?
Gemmules are internal buds, resistant to desiccation, freezing and anoxia.
- not many species,
- skeletons made of calcium carbonate (no spongin).
- They occupy shallow water, and are
- important in reef building.
- Have syncytial cells (largest in metazoa), which the cell membranes are lost, so that the cells merge together.
- These are luconoid.
- Skeletons are siliceous.
- Deep water, cosmopolitan.
- Most diverse group, in
- terms of number of species and diversity of habitats and shapes. - 90% of all sponges
- Some are freshwater.
- Skeletons of Silica and Spongin.
- Algal symbionts contribute nutritients.
What special characteristics do eumetazoans have?
- embrionic cells,
- a digestive tract,
- bodies with distinct symmetry,
- true epithelia with basal lamina and
- cell junctions
What does the epithelium make it possibe for Eumetazoans to do?
- The opening of an embryo's central cavity in the early stage of development.
- Protostomes- becomes mouth
- Deuterostomes- becomes anus
An embryo at the stage following the blastula, when it is a hollow cup-shaped structure having three layers of cells
In the text document, I talked about the uncertainty of phylogeny, and how we do not know for sure where the ctenophores go. If they go with Cnidaria, in a monophyletic group, then the name “Coelenterata” is valid. If not, then the name is not. What do I mean by this?
We do not name paraphyletic groups, only monophyletic ones.
What is bootstrapping?
Bootstrapping provides some indication of how strongly the data support particular nodes on the tree. The closer they are to 100, the more strongly the data support that particular node
Cnidaria Body plan
- Lined sac with a regulated digestive
- compartment (coelenteron)
- Radial: major axis is oral-aboral.
- blind gut – (single opening, not a tube)
- True epithelial tissue with basal lamina, cell
- Epidermis covers outside
- Gastrodermis lines coelenteron
What is the coelenteron?
body cavity of a cnidaria and ctenophore, which is used as a stomach, an excretory organ and as a primitive vascular system.
What are the five funcions of the coelenteron?
- enzymes are secreted into it
- digestion begins extracellularly and is completed intracellularly
- Fluid Transport
- ciliated gastrodermis circulates its contents
- Hydrostatic Skeleton
- circular and longitudinal ‘muscles’ operate against
- the fluid in it
- Brood Chamber
- females may release eggs into the coelenteron
- and gestate them
- involved in volume regulation and release of
- metabolic wastes
- ammonia diffuses into the coelenteron and then
- exits the mouth
How many layers do cnidarians have, what are they?
Two, epidermis and gastrodermis
What is mesoglea?
- Thick and jelly-like or very thin
- Connective tissue
- Acellular or with amoebocytes
- 90% water, collagen, proteoglycans, sometimes spicules
What is alternation of generations in Cnidarians?
- flower-like, columnar
- usually attached by pedal disc
- Medusae (bells, jellies)
- flattened, mouth-down
versions of polyps
** the mature state is which ever produces gametes
Body plan of Cnidaria (3 layers)
- outer- epidermis
- middle- connective tissue
- inner- gastrodermis
A layer of extracellular matrix on which epithelium sits and which is secreted by the epithelial cells
Nervous system of cnidarians?
- Well developed but not centralized (no brain)- forms a net
- The nervous system allows them to respond to touch, light, gravity, and chemicals, so there are nerve cells specialized for all of these different stimuli.
- The nerves are connected to muscles.
How are cnidocytes structured and work?
- Epithelia cells unique to Cnidaria
- The inside of the cell is hypertonic (compared to sea water) and is controlled by osmosis
- The capsule contains toxin and coiled inverted tube, usually with spines or barbs
- Once the cell has been triggered (combination of mechanical and chemosensory signals)
- water enters the capsule and increases the pressure on the inverted tube
- the tube is turned inside out by squeezing and shoots from the capsule, releasing a toxin
What are the two stimuli required to trigger the discharge of cnidocytes?
Mechanical and chemical
3. High osmolarity
- 1. having a greater osmotic pressure than another
- 2, having a lesser osmotic pressure than another
- 3. high solute conent
individuals have just one of at least two distinct sexes
Where are gametes in cnidarians come from?
gametes are derived from interstitial cells
Where does fertilization occur for Cnidarians?
Some cnidarians retain the fertilized embryo inside the coelenteron, while others release gametes into the water, where they are fertilized without parental care”.
The larval stage, that develops from the egg. Cnidarian larvae are a solid ball of ciliated cells with no central cavity.
- Hydras and Physalia (Portuguese man-of-war.)
- Alt. of generations (except hydra)
- True Jellies
- Alt. of Generations (medusa dominates)
- Medusa = sexual Polyp = asexual
Sea corals and anemones
Which classes of cnidarians have alt. of generations?
Hydrozoan polyps are polymorphic. What are the two forms?
Feeding and asexual
How is the Hydra unusual?
Does not have a medusa form
Why might have the medusa stage been lost in Hydra?
Why would box jellies need such toxic posions?
designed to do is kill or imobilize prey immediately. kill immediately, or you will lose it.
Cubozoans have complex eyes in bunches of ____ eyes of different types
- ** Ocelli detect light, while the lens eyes can create an image.
- derived from common decent
- 1. share external positions and
- 2. share internal structure and
- 3. intermediates that bridge
- disparate characters
How are soft corals and fan corals different from the hexacorals?
In hard corals, the epidermis secrete a calcareous exoskeleton and that the coral polyps inhabit cups in the exoskeleton.
How are these coral colonies interconnected?
1.What do algae have to do with corals? What is coral bleaching?
2. Ocean acidification?
- 1. Corals contain symbiont photosynthetic
- algae. This algae providing the coral animals with nutrients. Certain stressful conditions can interfere with the photosynthesis process or even cause the symbiont to be expelled. (bleaching)
- 2. As CO2 is dissolved, oceans are decreasing in pH as humans turn fossil fuels back into carbon dioxide, and are now 0.1 pH lower than the pre-industrial oceans.
What is a dinoflagellate?
The algae that symbiots with corals
Ctenophores are also know as _________
How do ctenophores catch pray?
Most ctenophores use sticky cells called colloblasts, that are like cnidocytes, in that they ensnare prey from the tentacles, but they are sticky, not venomous. Some cnidarians engulf prey (without colloblasts), and the 2 classes of ctenophores are divided according to how they catch prey.
How do Ctenophores reproduce?
Most entirely planktonic most hermaphroditic, can self-fertilize. Ctenophores may have very rapid generation times. After attaining adult size, they will spawn eggs and sperm daily (for weeks), as long as there is sufficient food available in the plankton.
What group are protostomes and deuterostomes a part of?
Who is in the deuterostomes class?
echinoderms and chordates
The coelom is lined by ______ that is dervied from ________
What is a coelom? What does it have to do with triploblasty?
What are ossicles? How do they differ among the groups?
- Ossicles are calcareous secretions, not true bone, but true endoskeleton.
- Asteroid (seastar) ossicles are like armor plates or they are rods.
- Echinoids: derived ossicles that are fused into thin plates that surround almost their entire body, and forms a rigid hollow endoskeleton. If you look at an urchin, you will see a five part symmetry to their plates
- Ophiuroids, the brittle stars, have a couple different types of ossicles. Some are scales like shields for protection. Others are very much like vertebrae in the arms, and these are used like a snake would use its vertebrae.
- Muscles connect and operate the vertebrae-like ossicles.
- Holothuroids, the sea cucumbers have only microscopic remnants of ossicles embedded in dermis. Their body wall differs much from the other echinoderms.
- Crinoids are stalked. In the stalk, or column,
- are ossicles called columnals that look like beads or lifesaver candies. These are the support for the stalk.
How do echinoderms alter the rigidity of their bodies?
- mutable connective tissue- Under neural control, they make or break cross links between collagen fibers
- Asteroids autotomize arms, meaning, if something tries to eat one of their arms, they can release that arm.
- Ophiuroids can split of part of their disk to asexually reproduce.
- Echinoids lock their spines for defense using this tissue.
- Holothuroids can basically liquefy their bodies. If you look at a sea cucumber, it will seem rigid. Some sea cucumbers can also eject some of their guts when attacked. The lost parts can regrow.
- Crinoids use their connective tissue to attach to the substrate.
Water Vascular System
How does it control locomotion, feeding respiration and excretion?
Asteroids, How do they eat?
- Using their podia to grip a shellfish and their muscular arms to open it, they can then evert their stomach into the shellfish and begin digestion outside of their body.
- Starfish have a complete gut, meaning it is a tube with a separate entrance and exit.
- Mouth, esophagus, eversible cardiac stomach, pyloric stomach, rectum, anus-Gut lined with ciliated epithelium
Ophiuroids, how do they eat?
- Carinvores, but they have a gut that is a blind sac (no rectum or anus).
- Their snake-like arms may be used to grab prey and move it to their mouth. They may also use their podia like a conveyor belt to move particles deposited on the sea floor or suspended in the water into their mouths.
- Digestion and absorption occur in the stomach.
Holothuroid, how do they eat and breathe?
- Holothuroids take up particles deposited on the sea floor or suspended in the water. Their tentacles are modified feet, and along these tentacles are adhesive papillae for collecting food.
- Respiratory trees are extensions of the intestine that essentially increase surface area of permeable membrane.
- The cucumber pumps water in and out of its anus extracts the oxygen and lets out carbon dioxide.
Echniodia, how do they eat?
- Irregular urchins feed on particles that are deposited on the sea floor. They embed themselves in an angle in the sea floor and tube feet move food to the mouth.
- Regular urchins are grazers (urchins)- Long, suckered podia– 5 teeth in a jaw apparatus (Aristotle’s lantern)
Crinoids, how do they eat?
Crinoid arms have channels on their many arms that are ciliated to move particles. - suspension feed
Reproduction of Echinoderms
- Best developed in brittle stars
- The disk divides (fission)
- Arm with 20% of disk can produce a new star
- Sexual by far the most common:
- Gonochoric (males and females)
- External fertilization
- Typically both sexes free spawn gametes
- A few species brood; female retains eggs and embryos– Some brittle stars brood in the genital bursae
- There is some parental care
Two classes of hemichordata
the Enteropneusta and the Pterobranchia.
Hemichordates animals have a stomochord that looks like a notochord, but it is uncertain if these features have the same evolutionary origin.
Fish are ______.
How are Urochordata and tunicates related to chordates?
- Urochordate adults lose or reduce some of their chordate
- synapomorphies, but these are present in the larva.
What are Ascidians?
ascidians have a few well-developed organs, but most of their space is taken up by the pharyngeal basket, which is derived from the ancestral gill slits
Thailaceans have what important group in there? How do they feed? How does this affect the available food for other animals?
- Salps, are very effective filter feeders.
- They can take up much of the carbon-containing particles in the open water, thereby taking energy away from other animals, for example, krill.
- Salps do not make good food for many animals, including whales, so it is a problem that so much energy is being tied up in salps and no other animals.
- The feces of salps is also important in ocean carbon cycling.
Appendicularia are tadpoles but they become sexually mature. What is padeomorphosis ? Why's it important?
- The retention by adults of traits previously
- seen only in juveniles
- Supports information of phylogenies.
Cephalochodates (lancelets) retain all chordate synapomorphies as adults which is a case of ______.
What came first skull, or jaws?
Skull then jaws
Was the movement onto land monophyletic or paraphyletic?
What did the amnion do for tetrapods?
Allowed them to lay eggs on land without drying out
How are amniotes divided?
By the amount of hole in the skull behind the eyes.
the study of non-avian reptiles, and amphibians
What are the characteristics that define Mammalia?
- Notochord, post anal tail, pharyngeal gill slits,
- dorsal hollow nerve cord.
- Extant Mammals are defined by ear bone and jaw characters.
Which "dinosaurs" are not really dinosaurs?
When did synapsids become endothermic? What is the supporting evidence?
- Gorgonopsia are speculated to be endothermic
- Mesozic Era
What is important about plate tectonics? Australia? South America?
Australia was completely isolated 135 million years ago. All it had were monotremes and marsupials. Eutherians evolved later, and never made their way to Australia (Pangea split), until humans came and brought dogs, and rats. Also, notice that in the Cretaceous, North and South America were separated, and only joined when Panama connected them, about 5 million years ago. This resulted in the movement of Eutherians into S. America, and a mass extinction of marsupials. But there are still a lot of marsupials in S. America, and the opossum is one of the marsupials that migrated North, when Panama formed.
- egg laying mammals. Have fur, three inner ear
- bones, and produce milk. Only one cloaca.
Snakes and lizards are also called _________