BIOL 205 Lab Midterm

phylogenetic tree

hypothesis of a the evolutionary relationships among different organisms (based on shared morphological, behavioural, biochemical, and genetic characters)

if a common ancestor between two taxa is more recent, what would we expect?

expect more traits for them to share

taxon (plural: taxa)

named group of organisms

phenotypic character

feature of an organism that can be observed (e.g. eye colour, jointed appendages)

minimum number of character states to construct a useful phylogenetic tree

2 (could be presence or absence of that character)

character vs character state

character - the attribute being observed (e.g. eye colour)

character state - the manifestation of that character found in a taxon (e.g. blue eyes)

phenotypic characters can be __________

morphological (anatomical structures like muscles or gills)

developmental (such as pattern of cell cleavage, or formation of the coelom)

behavioural (nest-building in birds)

biochemical (enzyme pathways)

shared character

when 2 or more taxa have the same character state for a character

homologous characters

shared characters that were inherited from the same character in a common ancestor

e.g. If structure X in one species and structure Y in a different species both arose from the same structure in the common ancestor of these 2 species, then we can say structure X and Y are homologous

are shared characters always homologous? explain

No, shared characters aren’t always homologous

also possible that 2 taxa have a shared character because of convergence (convergent evolution) meaning that these taxa each inherited this character state independently during different evolutionary events as opposed to having inherited this character state from a common ancestor

what kinds of evidence would support your hypothesis that a shared character in two taxa could be homologous?

• Must have evidence that this character is derived from the same character in the most recent common ancestor of the two taxa

• This can be supported by finding structural and positional similarities, ????

why is it difficult for biologists to find evidence for homologous characters (rather than a result of convergence?) (5)

1. Shared characters may be convergent

2. Some characters are only present during certain stages of an organism’s life cycle (therefore must investigate ALL life cycle stages)

3. Sometimes character in one taxon will have a completely different function than its homologous character in another taxon

4. Sometimes a character in one taxon will look completely different than its homologous character in another taxon

5. Sometimes, during the evolutionary history of a taxon, a character may be secondarily lost

ways to classify character states

• Ancestral (plesiomorhpic) - same as in out-group character state

• Derived (apomorphic) - different than out-group character state

synapomorphy

= shared derived character state

an apomorphy (derived character state) that is shared by 2 or more taxa and their most recent common ancestor = synapomorphy

by definition, synapomorphy is a homologous character

Plesiomorphy

ancestral character state

Symplesiomorphy

a plesiomorphy that is shared by 2 or more taxa

By definition, symplesiomorphies are homologous characters

in-group vs out-group

In-group = taxa we are analyzing

Outgroup = taxon of organisms that is closely related to, but not part of, the in-group

parsimony & parsimonious phylogenetic tree

• Parsimony = simplest explanation possible

• Parsimonious phylogenetic tree = explains the shared derived characters with the fewest possible number of evolutionary changes

name the different types of symmetry

• Bilateral symmetry - humans (when you cut in half along longitudinal axis, the right and left halves would look similar)

• Radial symmetry - water bottle or starfish (has 1 central axis around which all the structures are arranged)

• Asymmetrical - no body axis and no plane of symmetry (no way to cut in half such that the two halves would appear similar)

Name the 3 major taxa of Porifera (sponges) and which are most common to spot

• Calcarea (calcareous sponges)

  • Not as common to spot - very SMALL

• Hexactinellida (glass sponges)

  • Not as common to spot - live in deep, cold-water environments

• Demospongiae (demosponges)

  • Most common type of sponge

important component of endoskeleton in sponges

spicules

do sponges hav a specialized nervous system, digestive system, or excretory system? what do they use?

No; their bodies are built around a system of water canals called the aquiferous system

Choanocytes (in sponges) do what? Properties?

• Pump water through water canals (aquiferous system)

• Each cell has a flagellum → beat flagella to generate water current → water current brings food particles into sponge’s aquiferous system → food particles are captured and engulfed by choanocytes (phagocytosis)

• Water current generated by choanocyte’s beating flagella also carries undigested waste and nitrogenous wastes OUT of the sponge, and supplies it with water flow for gas exchange

3 structural categories of sponges + features

• Asconoid

  • 1 chamber (spongocoel) lined with choanocytes

• Syconoid

  • Many small chambers lined with choanocytes

  • Incurrent canal

• Leuconoid

  • Many small chambers lined with choanocytes - some can contain billions of choanocyte chambers

  • Incurrent + excurrent canal

What structural category of sponges do species of Calcarea sponges have as adults?

• Some asconoid as adults

• Some syconoid as adults

• Some leuconoids are adults

What structural category of sponges do sponges in the taxa Hexactinellida and Demospongiae have as adults?

Most are leuconoid (although some Hexactinellida are classified as complex syconoid as adults)

Most sponges are ________, so almost all adult sponges are ________

demo sponges, leuconoid

Pinacocytes (sponges)

flattened cells that form a single layer to line the inner and outer sponge surfaces

Exopinacocytes vs Endopinacocytes

• Exo - line the outer surface of a sponge

• Endo - line internal surfaces like incurrent & excurrent canals

In asconoid sponges, the spongocoel is lined with what type of cells?

choanocytes and endopinacocytes

In syconoid and leuconoid sponges, the spongocoel is lined with what type of cells?

endopinacocytes (but not choanocytes - instead, they line the choanocyte chambers)

Mesohyl

• Inner layer between pinacocytes and choanocytes

• Contains framework of collagen (protein) fibres, spicules, large variety of cells (e.g. amoebocytes and eggs)

Calcarea

• Very small

• Live in shallow marine environments

• Has calcareous (CaCO3) spicules

In sexual reproduction of sponges, where do sperm and eggs form from

• Choanocytes → sperm

• Amoebocytes in mesophyll → eggs

Hexactinellida

• Live in deep marine enviornments

• All spicules composed of silicon dioxide (H2Si3O7)

• Often called glass sponges because they have siliceous spicules and glass is also composed of silicon dioxide

• Six-rayed (hexactinal) spicules

Demospongiae

• Live in a wide variety of environments (some freshwater or some marine)

• Has a proteinaceous spongin (organized framework of collagen fibrils) skeleton, alone or in combination with siliceous spicules

gemmules (sponges - demospongiae)

example of asexual reproduction; produced at the beginning of winter and can survive much colder temperatures than their parent sponge

micropyle

thin region of the spongin casing which lacks spicules (in demospongiae)

If you drop some HCl on a spicule and it begins to bubble CO2, what does this tell you?

That it is calcarea (its spicules are made of CaCO3 which reacts with HCL to produce CO2)

How does a medusa swim?

Muscles lining the bell contract and decrease the volume of subumbrellar space (cavity under the concave side of the bell). This forcefully pushes water and drives the medusa forward, allowing it to freely swim.

what type of symmetry is present in the polyp and medusa stage of an adult cnidarian?

radial symmetry

Polyp vs. Medusa life stage in Cnidarians

• Polyp - sessile (don’t move)

• Medusa - pelagic (free swimming)

What type of digestive system do cnidaria have?

Incomplete digestive tract - just one opening (GVC opening)

Structures present in asconoid sponges + trace the water flow in Asconoids

Structures:

• Ostium

• Choanocyte layer

• Spongoceol

Water flow:

Ostium → spongocoel (lined with choanocyte layer) → osculum

Structures present in synconoid sponges + trace the water flow in Synconoids

Structures:

• Incurrent canal

• Choanocyte layer

• Spongocoel

Water flow:

Incurrent canal → spongocoel → osculum

Structures present in leuconoid sponges + trace the water flow in Leuconoids

Structures:

• dermal pore

• incurrent canal

• choanocyte chamber

• excurrent canal

• spongocoel

Water flow:

Dermal pore → incurrent canal → choanocyte chamber → excurrent canal → spongocoel → osculum

Compare and contras sexual and asexual reproduction in sponges, based on examples viewed in lab

Sexual reproduction:

• Involves formation of sperm from choanocytes & eggs from amoebocytes in the mesohyll

  • Gamete formation & fertilization

  • (see pg.13)

Asexual reproduction:

• Involves gemmule production (e.g. in Spongilla) - gemmules can survive much colder temperatures than their parent sponge which usually dies during the winter —> during autumn, archeaocytes gather in the mesophyll and undergo mitosis —> the resulting large mass of archeocytes get surrounded by trophocytes —> archeocytes engulf trophocytes (phagocytosis) to obtain nutrients —> archoeocytes get surrounded by tough spongin casing supported by spicules (micropyle = thin region of sponging casing lacking spicules) —> parent sponge dies and degenerates, scattering the gemmules into the sediment —> when conditions improve in spring, gemmules hatch (micropyle will open and archoecytes exit the spongin casing to form new sponge)

Do Cnidarians have a specialized circulatory or respiratory system? If not, what do they use?

No; they use simple diffusion instead

What are important physical features to use simple diffusion?

• Thin tissues (which makes sense as lots of cnidarians are see-through)

• High surface area to volume ratio

What are the 2 tissue layers present in adult cnidarians?

• Gastrodermis

• Epidermis

Compare and contrast the anatomy of representative medusozoans and anthozoans in this lab

(Hydrozoa: Hydra, Pennaria, Obelia // Scyphozoa: Aurelia // Anthozoa: Metridium)

Aurelia (Scyphozoa):

• Branched radial canals (part of GVC)

• Ring canals (connected to gastric pouches by the radial canals)

• Oral arms of manubrium

• Rhopalia

• Statocysts (sensory structure - georeceptors for balance)

• Ocelli (photoreceptors - light sensing)

• Tentacles

• Gonads

Metridium (Anthozoa):

• GVC partially separated into many smaller chambers by mesenteries (aka septa) (thin walls)

• Mesentaries lined with gastrodermis

• Aconita (white threads) extend from edges of mesenteries

  • Each acontium contains thousands of glutinant nematocysts - when disturbed it may release acontia to defend itself

Compare and contrast the life cycles of representative medusozoans and anthozoans in this lab

(Hydrozoa: Hydra, Pennaria, Obelia // Scyphozoa: Aurelia // Anthozoa: Metridium)

lowkey see the pdf pages for life cycles

Hydrozoa:

Scyphozoa:

• Sexual reproduction during medusa stage (results in production of planula larva, and will eventually form a tiny polyp: scyphistoma)

• Aurelia life cycle:

  • Asexual phase: Planula larva (from zygote) → Scyphistoma → Strobila → (sexual phase)

  • Sexual phase: Ephyra (young medusa) → Medusa (sexually mature) → produce egg, sperm and zygote formation —> planula larva (asexual)

Anthozoa:

• Lack medusa stage

• Polyp stage - can undergo asexual reproduction but also sexual reproduction

  • Sexual reproduction → results in production of planula larva stage which settles, attaches, and grows into a new polyp

Predict how differences in and/or changes to the anatomical structures of these representative cnidarians would affect function in these animals

(Hydrozoa: Hydra, Pennaria, Obelia // Scyphozoa: Aurelia // Anthozoa: Metridium)

Describe movement and feeding behaviour in Hydra (Hydrozoa) and sea anemones (Anthozoa)

Compare and contrast the structure and function of different types of nematocysts

What is the importance of the surface area to volume ratio of an animal, for processes such as gas exchange with the environment and nutrient absorption?

What is the type of cnidae (of the 3 basic types) that is found in all cnidarians (except for myxozoa)?

Nematocysts

1. What is the outer body surface lined with in Cnidarians?

2. Do they have a GVC? Characteristics of GVC?

3. What forms the lining of the GVC?

1. Epidermis

2. Yes, they have a GVC; GVC only has one opening (GVC opening) through which food enters and waste is removed

3. Gastrodermis

What is between the epidermis and gastrodermis of cnidarians?

A layer of either mesoglea or mesenchyme

Mesoglea vs. mesenchyme (in Cnidarians)

Mesoglea = Jelly-like matrix that does NOT contain living cells

Mesenchyme = Jelly-like matrix that DOES contain living cells

Hydrozoans, Scyphozoa, and Anthozoa have (mesoglea or mesenchyme)

• Hydrozoans → mesoglea

• Scyphozoa & Anthozoa → mesenchyme

What is the basic adult body form or a cnidarian? What is their symmetry?

Polyp or medusa (both have radial symmetry)

What type of life cycle do many cnidarians have?

Dimorphic life cycle - consisting of 2 distinct adult body forms (polyp & medusa)

Medusae are generally ___________, and their general shape is bell shaped with a ____________ located under the _________ side of the bell

pelagic

subumbrellar space

concave

Polyps are generally _________, often using a _____ ______ or related to structure to attach to hard surfaces. Most polyps are _______, although in some species, the pedal disc can be used to move very slowly along hard surfaces.

benthic

pedal disc

sessile

what type of reproduction do polyps use and are there exceptions? what about for medusae?

• Polyps - generally reproduce using asexual budding (although anthozoan polyps also reproduce sexually)

• Medusae - generally reproduce sexually

in what taxa do polyps remain connected at the tissue level to form a large multi-pulp colony? Why do they do this? Provide an example within the taxa that we observed in lab

• Many hydrozoans form multi-poly colony

• Genetically identical polyps can have different functions: feeding, reproduction, defence

• e.g. Obelia

Nematocyst structure and describe the process when it discharges

• Composed of a long thread that is coiled within a capsule

• When nematocyst is stimulated (either chemically or mechanically) it discharges and the capsule opens

• As capsule opens, one end of the thread is rapidly launched out of the capsule and other end remains attached to the capsule

Tentacular bulbs (and how they compare to rhopalia)

Tentacular bulbs contain a statocyst, ocelli, and chemoreceptor, but unlike rhopalia, they are not located between a pair of lappets.

A tentacular bulb is located at the base of each tentacle.

3 major nematocyst types

penetrant (penetrating), volvent (entangling), and glutinant (adhesive)

what are the branches of the copulatory canal (in snail)

2 branches: Blind diverticulum & Bursa Copulatrix

1. Scaphopod muscular foot function

2. Polyplacophora (Chitons) ventral foot function

1. to burrow into soft sediments such as sand on the ocean floor

2. Ventral foot allow chitons to cling to hard surfaces without being swept away by waves

Mollusc basic characteristics

• complete digestive tract (with mouth and anus)

• ventral muscular foot

• a calcareous shell secreted by the mantle

• a mantle cavity

• a radula for feeding

• pairs of gills called ctenidia (singular: ctenidium; the ‘c’ is silent)

Cestoda life cycle

• Gravid proglottids released into intestine of human host (definitive) and leave body through feces

• Proglottids break releasing eggs

• Egg becomes embryo

• Embryo becomes onchosphere

• Onchosphere eaten by pig

• Onchosphere sheds coating and burrows into intestinal wall

• Moves to circulatory system and skeletal muscle

• Becomes invaginated cysticercus

• Human eats pig (muscle)

• Cysticercus invaginates in digestive tract and hooks onto wall using scolex

Platyhelminthes traits

• Incomplete gut (GVC)

• Acoelomate (because they are triploblastic animals that do not have a coelom)

• Monoecious (each individual can produce both eggs

  and sperm)

• Reproduce through mutual cross-fertilization

Cnidaria: the GVC is partially divided into many smaller chambers by what?

Mesenteries (aka septa)

describe what happens when a nematocyst is stimulated (cnidarians)

it gets discharged, and the capsule opens. As capsule opens, one end of the thread is rapidly launched out while the other remains attached to the capsule.

Which Cnidarian group contains the “true” jellies and have a prominent medusa stage?

Scyphozoa

Medusa stage of scyphozoans (scyphomedusae)

• GVC has 4 gastric pouches

• Radial canals of GVC are extensively b ranched

• Radial canals connect the gastric pouches to the ring canal

• Rhopalia (sensory structures containing statocysts = georeceptors, ocelli, chemoreceptors)

  • Each rhopalium is located between 2 flaps (lappets)

• Manubrium has 4 elongated arms (whereas in hydromedusae it is central, tubular, and shorter)

When does sexual reproduction in Scyphozoa occur? What does it result in?

• Occurs in medusa stage

• Results in production of a planula larva (which do NOT feed will eventually settle and form a small polyp = scyphistoma)

Hydrozoa prominent life stage? Reproduction?

Prominent polyp stage (either colonial or solitary) - reproduces asexually (and gives rise to asexually produced medusa stage called a hydromedusa)

Hydromedusa reproduction?

• Sexual but short life span; polyp stage persists much longer

• Sexual reproduction results in production of planula larvae

Which Hydrozoa species have solitary polyps? Large colonies?

• Solitary - Hydra

• Large colonies - Obelia & Pennaria

Describe planula larvae in hydrozoans?

Lecithotrophic - obtain their nutrients from yolk (therefore, don’t feed)

Gastrozooid vs gonozooid function (obelia)

Gastrozooid - polyps specialized for feeding

Gonozooid - polyps specialized for production of gonophores (structures that develop into medusae)

Perisarc and Coenosarc (obelia and pennaria - Hydrozoa)

Perisarc = chitinous exoskeleton secreted by epidermis

Coenosarc = living tissue located inside perisarc

Examples of differences in medusa stage of Scyphozoa and Hydrozoa (scyphomedusa vs. hydromedusa)

• Most hydromedusae have a velum (= thin membrane that determines the size of the opening into subumbrellar space) while scyphomedusae don’t

• Hydromedusae have tentacular bulbs as their main sensory structure(contain statocyst, ocelli, chemoreceptor, but unlike rhopalia in scyphomedusae, they aren’t located between a pair of lappets - but rather located at the base of each tentacle)

Hydra (Hydrozoa)

• Atypical life style for Hydrozoa

• Have secondarily lost their medusa phase (because they live in freshwater, the free-swimming Medusa would probably just be washed away downstream - advantage)

• Polyp stage responsible for both asexual and sexual reproduction

• Epidermis, gastrodermis, mesoglea (jelly like matrix w/o living cells)

Groups in Cnidaria phylum we learned (bolded only)

• Anthozoa

• Medusozoa

  • Hydrozoa (e.g. Hydra)

  • Scyphozoa (true jellies)

Groups in Platyhelminthes phylum we learned

• Polycladida (polyclads - free living)

• Rhabdocoela (rhabdocoels - free living)

• Tricladida (triclads - free living)

• Neodermata (parasitic)

  • Monogenea (monogenetic flukes)

  • Trematoda (digenetic flukes)

  • Cestoda (tapeworms)

Platyhelminthes contains a large group of dorsoventrally flattened animals commonly known as flatworms. Flatworm characteristics

• Bilaterally symmetrical

• Cephalization (development of head)

• Triploblastic (endoderm, mesoderm, ectoderm)

• GVC

Tricladida (Platyhelminthes)

• Free-living flatworms

• GVC has 3 main branches

• Cylindrical pharynx

• Ovaries produce eggs but vitelline glands produce yolk

Polycladida

• Free-living flatworms

• Monoecious (like all flatworms)

• Many branches from GVC

• Ruffled pharynx (Triclad have cylindrical)

• Ovaries produce both egg and yolk

Rhabdocoela

• Free living

• Bulbous pharynx

• Simple, sac-like GVC without branches

• Ovaries produce eggs but vitelline glands produce the yolk

Neodermta

• Parasitic flatworms

• Modified epidermis called tegument (no cilia, cells fuse together)

• Ovaries produce eggs but vitelline glands produce yolk (like triclads and Rhabocoela)

Has 3 subgroups (all parasitic): Monogenea, Trematoda, Cestoda

Trematoda

• Flukes

• 2-3 hosts

• Endoparsites

• Oral sucker (anterior end) and ventral sucker (posterior end)

Cestoda

• Tapeworms

• Flattened parasites living within intestines of vertebrates (definitive host)

• Lost GVC

• Outer tegument for nutrient absorption

• Scolex (adults, anterior end) - hooks and/or suckers to attach to intestinal wall of host

• Proglottids - contains complete set of male and female reproductive organs

Groups within Mollusca phylum that we learned

• Gastropoda

• Polyplacophora

• Scaphopoda

• Bivalvia

• Cephalopoda

Mantle

thick sheet of skin that forms the dorsal body and grows outwards to form folds

Mantle cavity

space in between mantle folds and rest of the body