Midterm Flashcards
Is evolution random? Describe why or why not
2
List and describe major problems faced by all animals
Locomotion - dispersion, finding mates Environmental constraints - temperature, humidity Food/Nutrition - finding food Not becoming prey Sex
What is evolution?
The change in frequency of a trait in a given population
Describe how unicellular and multicellular organisms may be considered similar in lifestyle
Each have the same challenges - finding food, getting rid of wastes, not being prey. They just handle them in different ways, with the unicellular organisms using organelles and the multicellular organisms using combinations of similar single cells (organs)
Multicellular animals are known as _____
Metazoans
Bilateral symmetry is highly correlated with _____. Describe this process
Cephalization, the concentration of nervous and sensory tissues and organs on one end of the body, resulting in distinct anterior and posterior
Distinguish between bilateral and radial symmetry. Give examples of organisms displaying each?
Humans are bilaterally symmetrical, whereas organisms like diatoms are radially symmetrical (can be divided on any plane and still be symmetrical)
Why are choanoflagellates considered the precursor to multicellular life?
Choanoflagellates form multicellular groupings of cells embedded in a mucousal matrix. On the outside are the regular choanoflagellates, and on the inside are amoeboid cells that transport wastes
The _______ were considered the first organisms to be diploblastic
Cnidarians
The phrase “isogametes” refers to what? What are they found in?
Gametes that do not have distinct sexes, just combine. Found in some dinoflagellates, volvox
Describe how budding could have given rise to gametes
Budding can occur externally or internally, and buds are typically smaller than the parent organism. Some organisms use buds as gametes, which combine to create a diploid recombinant
Describe the paramecium life cycle
Usually 2N, can undergo binary fission or produce haploid gametes, which combine to form zygote
The ciliophora are otherwise known was the ____
Ciliates
A _______ is a network of cilia that work together
Cirri
Describe the mouths that ciliates often have. How are food vacuoles formed?
May have a cytostome or mouth structure heading into cytopharynx or complex with buccal cavity.
Food vacuoles often form at the bottom of the cytopharynx
Which class of Platyhelminthes is mostly free living?
Turbellaria
Over _____% of Platyhelminthes are parasitic
80%
Are the Platyhelminthes secondarily acoelomates?
Fossil record is very hard to determine for the Platyhelminthes (no bones).scientists are not entirely sure whether the acoelomates condition is ancestral, but it is though that it is ancestral in at least some
What structures are Platyhelminthes lacking?
Respiratory organs, circulatory system
How does gas exchange occur in Platyhelminthes?
Across Body surface, with rate dependent on gradient, permeability of body wall, surface area
How do metabolic wastes leave flatworms?
Diffusing across body surface
Describe platyhelminthes protonephridia
A cup of cilia capped by a mesh cap (called “flame cell”) or a cup with a single flagellum (solenocyte). Cups connect to single excretory pore
Describe the reproductive structures of the Platyhelminthes
All 4 classes are simultaneous hermaphrodites
The larval epidermis is replaced by a _____ in all Platyhelminthes but the ______
Tegument, Turbellaria
How do Cnidarians and Platyhelminths deal with waste material, how does this differ from us?
Has to go back out the same hole it came in, meaning that every so often undigested food may be eliminated from the cavity
How do Cnidarians such as sea anemones prevent their tentacles from drying out
They spit the water out of their gastric cavity, shrivel up and cover themselves with a protective covering, re emerging when conditions have improved.
Platyhelminthes are _____blastic
Triploblastic
The embryonic ________ eventually becomes the mouth in a group called the ________
Blastopore, protostomes
Echinoderms are unique among invertebrates in that they are _______, meaning that the blastopore forms the ______
Deuterostomes, anus
The cavity caused by the rapid division of mesoderm cells is called the ______
Coelom
______ organisms have not developed a body cavity (AKA coelom)
Acoelomate
What drove the evolution of nerve ganglionation in the Platyhelminthes?
The bilaterally symmetrical, streamlined shape with distinct anterior and posterior encouraged “cephalization” or the evolution of a head region with focus on sensory functions
The nervous system in the flatworm goes through ________, with densely packed ______ that bear resemblance to a central nervous system
Ganglionation, ganglia
The Platyhelminths are ____ symmetrical
Bilaterally
Describe the differences in lifestyle between organisms in a high humidity environment (water) and a low humidity environment (land)
high humidity - Can absorb oxygen through skin surfaces or exposed respiratory surfaces, can let young loose earlier in their lives, can fertilize externally, excrete ammonia
Low humidity - must excrete urea or uric acid, have internalized respiratory surfaces (or else they’d dry out), internal fertilization, protected embryonic development
Describe the differences in lifestyle between organisms in a high density environment (water) and a low density environment (land)
high - no need for rigid skeleton, filter feeding possible, favours external fertilization and dispersing larval stages
low - Rigid skeleton needed, must move to find food, internal fertilization, sedentary developmental stages
Describe the differences in lifestyle between organisms in a low compressibility environment (water) and a high compressibility environment (land)
low - Pressure changes transmitted uniformly, allows for pressure sensitivity
high - Pressure changes not easily transmitted, hydroskeletons not useful
Describe the differences in lifestyle between organisms in a high specific heat environment (water) and a low specific heat environment (land)
High - temperature stable, enzymes efficient
Low - temperature fluctuates, must have enzymes that can tolerate that or different enzymes for different temperatures
Describe the differences in lifestyle between organisms in a high viscosity environment (water) and a low viscosity environment (land)
High - Organisms sink slowly, more energy required to move
Low - Less resistance to moving, faster falling rates
Describe the differences in lifestyle between organisms in a high nutrient content environment (water) and a low nutrient content environment (land)
high - Salts/nutrients available for direct absorption, adults need not invest much in offspring
Low - cannot directly absorb nutrients, offspring must be well supplied, harder to find nutrients
Describe the differences between waste excretion methods (ammonia, uric acid, urea)
Ammonia - used by aquatic animals, high toxic but can easily diffuse in water. Requires a lot of water to excrete
Urea - Used by many land animals such as mammals. Uses some water to excrete, less toxic than ammonia and requires a little energy to convert
Uric acid - Used by birds and reptiles, requires little water to excrete and is far less toxic than ammonia, less toxic than urea
Briefly describe what a cell membrane is
Selectively permeable barrier between cell and environment, fluid and flexible (thanks to lipids), but rigid (thanks to cholesterol and saturated lipids)
Describe the difference between flagella and cilia
Flagella - Long, move in a whiplike motion, propel from base to tip or tip to base
Cilia - beat together (sequentially) in large numbers, are short and stuff, move in an oar-like motion
Describe the structure of flagella
Move because microtubules inside slide past each other, with microtubules on one side contracting/shortening while the other expands to create a back and forth whip-like motion
Base to tip movement of flagella results in a ____ motion, whereas tip to base movement of flagella results in a ____ motion
Pull, push
Briefly describe the movement of rows of cilia
Cilia are swept like an oar in one direction (power stroke), at the end the structure of the cilia is altered and the cilium becomes soft and is pushed back into the starting place
Why is it advantageous for large organisms to be streamlined (teardrop shape) in water, but for small organisms to be spherical?
More drag is produced when an organism has higher surface area. Streamlining shape makes for the highest speed with the least amount of energy exerted
a spherical form is helpful for smaller organisms because of reduced pressure drag and the desire to stay afloat in the water column.
Large particles requiring breakdown in a cell enter by ______
phagocytosis
Describe receptor-mediated endocytosis
Cells absorb molecules by inward budding of the cytoplasm at specific receptor sites
How does food pass through protozoa?
Food vacuole is formed when food particle is engulfed, vacuole holds high concentrations of digestive enzymes (functions as a gut), making digestion more efficient. Nutrients are absorbed and undigested material is exocytosed
A food vacuole is otherwise known as _____
phagosome
The ____ is the permanent site of food vacuole formation in ciliates
cytostome
____ vesicles take H+ ions to food vacuoles so digestion can occur (more efficient in acidic environments) in ciliates
Acid vesicles
the _____ is the anus equivalent in ciliates
cytoproct
Single celled organisms must be ______
aquatic
What happens to a single celled organism with no water-permeable membrane or contractile vacuole?
Water flows in, organism pops
What happens to a single celled organism with no contractile vacuole but a water permeable membrane
Water can flow out, but solutes are lost, cell can die
What happens in a single celled organism with a contractile vacuole and a water permeable membrane
Water can leave as it enters, preserving cellular solutes
Describe the size of protists
All single celled, small with high surface area:volume ratio, between micrometers and millimetres wide
Describe the difference between the protist endo and ectoplasm
Ectoplasm - gelatinous outer region of cytoplasm
Endoplasm - more fluid inner region of the cytoplasm
Why are freshwater environments so hard for protists to live in?
Solute concentrations inside the cell will be much higher than outside, must develop ways to pump water out of the cell and retain solutes
The protists are important from a health standpoint because….
alot of the biggest killers throughout history have been protists
What is the Parasitologist’s Dilemma?
Cost of studying cures for parasites is that more humans exist to destroy the environment
how are protists grouped together?
Based mainly on locomotion, hotly debated
What are the different types of flagellates
Phytoflagellates (have flagella and chloroplasts) - dinoflagellates, euglena, volvox
Zooflagellates (lack chloroplasts, usually parasitic) - choanoflagellates, Trypanosoma
List the types of protists
Flagellates, Sarcodines, Sporozoans, Ciliates
Describe the sarcodine protists
use pseudopodia to move. Includes amoebas, slime molds
Describe the sporozoan protists
Move by body flexion (all are parasitic as far as we know), some use flagella or pseudopods
Includes plasmodium
Sarcodines can form outside layers called _____
Tests
Describe the ciliate protists
Use cilia, are structurally complex, includes paramecium and stentor, two of the most complex organisms
Describe parasitism?
Net cost to host, net benefit to parasite
Describe commensalism
no netcost to either part, net benefit to one
Describe mutualism. Give an example of a mutualistic protist relationship
No cost to either, benefit to both. protists live in the guts of wood feeding termites, digesting cellulose
In what situations do protists undergo sexual reproduction?
When environmental conditions are good, asexual reproduction is enough to raise numbers, but sexual reproduction may be needed to introduce genetic variability
Describe schizogony/merogony
Otherwise known as multiple fission, occurs when multiple nuclear divisions are followed by the division of the cytoplasm and organelles. Karyokinesis then cytokinesis
If an organism produces 2 buds it is referred to as ______
If an organism produces more than two buds it is referred to as _______
Endodiogeny, endopolyogeny
Describe isogametes
Gametes that are not distinctly male or female
Describe how protist gametes may have given rise to anisogamy
slowly over time, some gametes may have evolved to be larger (like eggs) and some to b e smaller (like sperm)
Describe the reproductive cycle of paramecium
can undergo transverse binary fission whenever they choose, 2N individual undergoes meiosis into gametes (which conjugate)
Describe the life cycle of organisms such as malaria parasites
zygote (2N) undergoes meiosis to produce haploid spores (typically with the intention of protecting the organism in a transition between environments), then replication occurs and some change forms into male and female gametes, which form diploid zygotes. May only reproduce sexually every few cycles
Describe, in detail, the life cycle of malaria. Starting from human infection
Sporozoites in mosquito saliva are inserted into host, making their way to the liver. In the liver they undergo asexual replication (schizogony) to produce schizonts (liver cells full of replicated parasites, burst open). Tropohozoites make their way into the blood and consume contents of the red blood cells (erythrocytic schizont), There something triggers the transformation of some to the trophozoites into gametocytes. Female (microgametocyte) and male (macrogametocyte) enter a mosquito when it bites a human. Seek each other out in the mosquito’s blood. Form diploid ookinete, undergo sporogony (more asexual reproduction) to produce a diploid oocyst, which then bursts. The sporozoites find their way to the mosquitos salivary glands and the process repeats.
Describe different ways in which ciliates obtain prey
Attack prey by injecting trichocysts, attach tentacles (haptocysts) to prey, filter feed using cilia
Crown of cilia is referred to as _____
Oral cone
The outside of the sponge is referred to as ____
Pinacoderm
Sponges are referred to as _____ instead of metazoan. Describe this
Parazoan, no true germ layering, lack organs, have different cell types
Most sponges are found in _____ water
marine
Sponge cells are _____, meaning they can change form and function when needed
totipotent
Briefly describe sponge larbae
Motile, flagellated, diploid, often planktonic
What is the sponge alternative to nerve cells?
Have protein receptors that can respond to other organisms, changes in chemistry
_____ cells line the pores of sponges
porocyte
The inner cavity of porifera is the _____
spongocoel
Adjacent to the choanocyte layer in sponges is the acellular _______
mesohyl
Why is the mesohyl of sponges not a true tissue layer?
Acellular, gelatinoous, not formed from embryonic mesoderm (sponges don’t have mesoderm)
Describe the living cells inside the mesohyl
Amoeboid archaeocytes move via pseudopodia. Used in digestion of food captured by choanocytes can store digested food, may give rise to sperm and eggs, can specialize to eliminate wastes or secrete supportive structures
Describe the asconoid sponges
Simplest. Radially symmetrical, extremely small and vase-like in shape. Have osculum leading to atrium.
Describe syconoid sponges
Have invaginations and evaginations produced by folding in the choanoderm and pinacoderm. choanocytes now in folded chambers, not open in atrium. Enables organism to grow on smaller surfaces, increases surface area for choanoderm layer, connect to outside with a system of simple canals
Describe leuconoid sponges
Have secondary folding, thickening of mesohyl, canals become chambers with openenings called prosopyls. Exits called apopyle. Increased surface area and complexity. Water flow no longer uniform. Allows choanocytes to interact with small amount of water (optimal food intake). Sponges can grow much larger. Pinacocytes on outside can tighten to allow water in or out to control water flow
Cells that secrete spicules are called
sclerocytes
Describe sponge cell types
Pinacocytes - epithelial in function. Include porocytes (surround ostia openings into atrium), basopinacocytes (base of sponge body), endopinacocytes (line incurrent canals)
Choanocytes - feeding cells
Myocytes - Muscle-like contractile cells
Skeleton - spongocytes (secrete spongin), sclerocytes (secrete spicules)
Rhabdiferous cells (secrete slime/mucous)
Archaeocytes - totipotent amoeboid cells aiding in transport, excretion
Describe a monaxon spicule
one axis, one point of origin
Describe Porifera class Calcarea
Spicule composed of calcium carbonate only, spicules generally the same size and ship, monaxons with 3 or 4 points. Found at shallow depths, have little colour. Grow in clusters. Only living asconoids found in this class.
Why is it that sponges with calcium carbonate spicules cannot live at great depths?
Calcium carbonate crystallizes under low pressure
Describe Hexactinellida sponges
Spicules have six points (thus, hex) and are made of silica (triaxon). Trabecular network for body structure - as cells in pinacoderm and choanoderm mature, cell walls break down and they become one continuous multi nucleate cell. This increases the efficiency of cells moving across the sponge.
Larger than Calcarea, usually symmetrical, superficially syconoid/leuconoid. Don’t often grow in clustersOsculum covered by a sieve plate of silica spicules (can trap small fish/shrimp and force reproduction)
Describe Demospongiae sponges
Most sponges (95%), includes the commercial “Spongiidae”. Brilliant colours. Silica spicules associated with or replaced by collagen (spongin) skeleton (contain a bit of chitin too). Spicules are never triaxon. All are leuconoid, some encrust, some are goblet/urn shaped. Live in marine and freshwater.
Describe Family Clionidae of the sponges. To what Class do they belong?
Class: Demospongiae.
Clionidae are boring sponges which penetrate into calcium carbonate shells of molluscs (amoebocytes dissolve protein and calcium carbonate)
Describe the Spongillidae sponges. To what class do they belong?
Class: Demospongiae.
Have zoochlorellae protozoans in their body that enhance cell growth by transferring nutrients
Briefly describe the phylogeny of sponges. Why are they placed in their own group?
- Very ancient, have close affinity to protozoans (ex. choanoflagellates), unique among other metazoans (aquiferous system)
- Significantly unlike other metazoans
- Molecular work suggest monophyly of metazoans
- Relationships among classes not resolved
- Hexactinellida may represent it’s own subphylum
How do sponges defend against predators
Chemical defense secretions (allelochemicals)
Describe sexual sponge reproduction
Involves meiosis (many are hermaphroditic). Male gametes are expelled into the environment, eggs retained in the tissues and when fertilized, either released or brooded to larval stage (which is then released as a planktonic form). Planktonic larvae settle out, undergo the equivalent of gastrulation (that higher metazoans go through - folding/invagination) and develop into adult form.
Describe asexual reproduction in sponges
Gemmules forms in response to adverse environmental conditions. Archeocytes surrounded by spicules and spongin (protective shell) form gemmule. Parent disintegrates. When growth conditions prevail again, cells divide, emerge through micropyle (hole in gemmule) and a new sponge is formed
What is significant about the “cladorhizid” sponges?
Used to be their own class, now placed in Demospongiae. They live deep in the ocean and are carnivorous, entrapping small crustaceans and absorbing them. They have no ostia or oscula
Briefly describe phylum Cnidaria
Most are marine. All are radially symmetrical. Mouth is surrounded by tentacles leading to gastrovascular cavity. Body consists of two cell layers (epidermis and gastrodermis), all possess Cnidae (ex. Nematocysts), include polyp and medusa forms
What is the mesoglea of Cnidarians
Middle,gelatinous cell layer, not a true cell layer, located between the epidermis and gastrodermis
Which Cnidarians are not marine?
Hydra and related hydrozoans
What are the major groups within the Cnidaria
Hydrozoans, Scyphazoans, Anthazoans
Briefly describe class Scyphozoa
Usually medusa body form, mesoglea thick and gelatinous (hence, jellyfish).
Briefly list the tissues that the Cnidarians possess. How does this differ from sponges?
Endoderm - lines gut
Ectoderm - forms body covering
Mesoglea - Connective tissue-like layer of jelly/fibrous material
Posses a true gut (which porifera do not have), including coelenteron, gastrovascular cavity (which serves digestive and vascular-circulatory function)
Describe cnidarian tentacles
Tentacles surround oral aperture to aid in food procurement. They are rvaginations of the body wall
Describe the major body types of the Cnidarians
Polyp - Sessile, tubular, have crown of tentacles (ex. corals, hydroids), medoglia is thin, basement membrane between epidermis and gastrodermis
Medusa - Motile, pelagic, tentacles surround oral opening (which points downward), umbrella shaped, thick mesoglea (makes up bulk of body mass)
How do Cnidarian polyps often arrange themselves?
Colonially
Describe the cells that give the Cnidaria it’s name
Cnidocytes. Located through gastrodermis and/or epidermis. Can be found (potentially many in number) in musculoepithelial cells. Contain organelles called Cnidae, which can be discharged explosively for a variety of functions. Nematocysts are the most common type.
Describe the structure and use of cnidocytes
Cnidae consist of rounded, proteinaceous capsule with a hinged operculum capping it. Within the sac is a long coiled tube, and during discharge this tube shoots out, turning inside out as it does so. Often osmotic pressure is used to expel cindae.
Describe the interstitial cells of Cnidarians
Embedded between musculoepithelial cells, just below surface. Are small cells with large nuclei. They are totipotent and can give rise to sperm/eggs
The release of Cnidae is triggered by _____, a form of sensory cilia. Which classes are they found in?
Cnidocils, found in Hydrozoa and Scyphozoa
What are the three major classes of Cnidarians and how are they differentiated based on their cnidocytes
Hydrozoans, Scyphozoans, Anthozoans.
Scyphozoans and Anthozoans has gastrodermal cnidocytes
How at Nematocysts fired?
Osmotic pressure. Ca2+ ions released into capsule so that water generates hydrostatic pressure.
What functions do Cnidae serve?
Can release toxins, simply grab prey, stick to surfaces, penetrate surfaces.
Where are mucous secreting cells found in the Cnidaria and why are they important?
Found in the epidermis and gastrodermis. Especially important near the mouth as they allow for the passage of food
How does the nervous system of Cnidarians differ from sponges
It exists
How are nerve cells arranged in Cnidaria? How do they function.
Arranged in a net (plexus) with no concentration at any point. 1 net slowly releases multipolar neurons (which transmit actions along each arm). The other quickly releases bipolar neurons which coordinate action in circular muscles and aid in immediate physical response.
Nerve cells have chemo sensory function, proprioreception, photo reception, or pigment molecules (can take up certain kinds of light, cause neutron to be pulled in a certain direction which can cause a physical response)
What structures sense physician external stimuli in the Cnidarians?
Modified cilia which project from musculoepithelial cells. Have nerve cells at the base
Describe in detail the cells of the Cnidarian gut
Muscular cells - at right angles to body axis, can contract to make body thinner. Have one cilia per cell. Most common and highly developed near hypostome (mouth) and tentacles.
Nutritive cells can also help digestion.
Enzymatic cells:
Gland cells - secrete digestive enzymes for extracellular digestion of large prey items (further digestion is intracellular)
Mucus-secreting cells - concentrated around mouth
Nerve cells - function in killing prey that is still alive when it enters the gut
How does gas exchange/waste excretion occur in Cnidarians?
Occurs across body surface (epidermis and gastrodermis). The body is only 2 cell layers thick so direct excretion is easy.
How do Cnidarians move?
By contraction of musculoepithelial cells in the epidermis, followed by nutritive muscle cells in gastrodermis.
Forces are transmitted to water in the gastrovascular cavity, promoting movement
What do Cnidarians eat?
Almost all are carnivorous although some keep symbionts for extra energy. They feed primarily on small crustaceans and other plankton
Describe the feeding mechanisms of Cnidarians
Mucus lubricate mouth and it distends for swallowing. Enzymatic glands secrete enzymes that reduce prey to particles that can be engulfed and digested completely within cells
Describe Hydra reproduction
Asexual-
Budding occurs by evagination of body wall, new tentacles and hypostome form and new organism eventually detaches. Some may stick to parent as a colony.
Cells of gastro/epidermis remain totipotent so in the case of injury they can regenerate organism.Cell division in hydra is continuous at hypostome.
Sexual-
Uses ovaries or testes, which grow on the sides of the organism (develop from interstitial cells). Egg cells erupts from epidermis, fertilized by testes. Fertilized egg undergoes mitosis and forms a chitin shell. Hydra emerges in spring
Which class of Cnidaria is considered the most primitive?
Hydrozoans
Describe the features that characterize class Hydrozoa of the Cnidarians
May only have medusa or hydra, have no cnidocytes in the gastrodermis
This group does not have fertilization in the gastrovascular cavity: gametes are produced in the epidermis (or may be produced in gastrodermis but then shed directly to exterior
Describe the unique look of the Portugese Man o’ War (physalia). What class is it in?
Is a hydrozoan.
Is a floating polyp-colony with polyps specialized for feeding, reproduction, etc. One poylp can contain thousands to millions of nematocysts - cause major damage to human skin. So it is not a medusa!
Describe the generalized body plan of polyp-colony Hydrozoans
The G-V cavity and tissue layers of attached polyps are continuous. Stalk called hydrocaulus and oral end called hydranth.
Feeding polyps armed with nematocysts and tentacles catch prey, then transfer it to to other polyps for digestion,
Dactylozooids - Defensive polyps exist with cnidocytes
Gonozooids - Reproductive polyps, usually lack mouth/tentacles, give rise to medusae by budding
Describe how Hydrozoa (Cnidarians) sometimes have gonads?
Medusae can remain attached as reproductive structures (called sporosac)
Describe the structure of medusae
Called hydromedusae. Upper surface is called “exumbrella”, underside called “subumbrella”. Underside has an inward projecting shelf called a velum (aids in restricting opening for propulsion). Oral opening hanging down called manubrium
Describe class Scyphozoa
Usually medusa body form, mesoglea thick and gelatinous (hence, jellyfish), also partly cellular. Medusa is the dominant form. Manubrium drawn into long, frilly arms each with nematocysts. Cnidocytes are in gastro and epidermis. Have no velum (but do have similar “velarium”)
How do Scyphozoans swim?
Muscle fibres of swimming bell contract to decrease fluid under bell. Water is forcefully expelled from the bell and the animal is pushed forward. The bell recoils to it’s resting state, drawing the organism back slightly (but not enough to negate forward movement)
Describe the gastrovascular cavity of the Scyphozoans
Divided into gastric pouches by septa, which may be drawn out into gastric filaments with cnidocytes/gland cells. Organisms can be trapped in mucous and brought to the oral opening by cilia
Describe the nervous structures of Scyphozoans
Include sensory light balancing organs (statocysts), light receptors (ocelli) and sometimes touch receptors (sensory lappets)
Describe reproduction in Scyphozoans
Gonads develop in gastrodermal tissue (basically in gastric pouches). Individual medusae are usually male or female, and fertilization occurs. A planula larvae is the result, which attaches to a substrate then becomes a scyphistoma. This is a polyp form with the same egenral body plan as the medusa. The scyphystoma may produce more by budding.
What does it mean when an organism is dioecious?
two sexes
How does a polyp-like Scyphystoma produce medusa bodies?
By a process called “strobilation”. The body column of the polyp divides transversely, and many medusa-like models are formed stacked on top of one another. They break away as “ephyra”, which eventually become fully formed medusae
Describe class Anthozoa of the Cnidarians
includes sea anemones and corals, which are most of the cnidarians! All are marine and they are exclusively polyp formed. Can be solitary or colonial. Can reproduce both sexually and asexually. Polyps have an internal cavity divided by septa, and the pharynx penetrates into GV cavity. Gonads are gastrodermal
Describe the gastrovascular system of the Anthozoan Cnidarians
mouth opens to tubular pharynx and one or two siphonoglyph grooves. The cavity is divided by septa (unlike hydrozoans). They can be primary/complete mesentaries (attach to pharynx) or incomplete mesenteries (extend only partway through cavity). Incomplete mesenteries bear mucous cells, nematocysts and cells for digestion/phagocytosis. Mesenteries also contain the gonads
Describe the sea anemones
Large, solitary polyps that are brightly coloured. Oral disk bears many tentacles. Slit shaped mouth with ciliated siphonoglyph at one end allows water to enter GV cavity. Can contract and withdraw when threatened/inactive. Septa increase internal surface area for digestion, gas exchange, etc. Cnidocytes on tentacles may be used aggressively against other anemones.
Describe shape changes in the sea anemone
Siphonoglyph allows water to be slowly pumped into GV cavity as longitudinal muscles are relaxed and circular muscles contract (lowers width, raises height).
In the event of a predatory threat, the mouth can be opened, longitudinal muscles rapidly contracted and the anemone introverted to protect itself
Describe reproduction in Anthozoan Cnidarians
Asexual fission occurs.
Sexual -
Some are hermaphroditis but male/female gametes are produced asynchronously so self fertilization is uncommon. Often internal fertilization (with variable development before larval release). Typically the released larva is a planula, The larva then settles and becomes a new polyp.
Describe the stony corals (Madreporarian)
Grow in calcareous cups with sclerosepta (to anchor polyps), skeleton is completely outside polyp. Polyps are small, colonial, and usually interconnected. Most have zooxanthellae to provide nutrients. Corals compete with each other for substrate (use allelochemicals)
Describe the Octocorals
Includes Sea Pens, Sea Pansies, Sea Fans, Pip Corals.
Are colonial polyps with 8 tentacles, each of which is pinnate or as side branches. Polyps are joined by connective tissue called coenenchyme with gastrodermal tubes. Skeleton is internal - spicules or fused mass, may be rigid OR flexible. Some bend in relation to water current (Sea Fans). Probably feed on small particles. Reproduce similarly to anthozoans
What are the primary characteristics of the platyhelminthes?
Bilaterally symmetrical, dorsoventrally flattened, lack a coelom, do not have organs or a circulatory system, one opening to gut, filter wastes with protonephridia, connective tissue called parenchyma, usually hermaphoriditc
The _____ is one of the only Platyhelminth species that has separate males and females
Fluke
What is unique about the male-female relationship in the Schistosomes (of the Platyhelminthes)
Females live in a groove in the male’s body
List and briefly describe the 4 major Platyhelminthes classes
Trematodes - parasitic flukes
Monogenea - Uncommon parasitic flatworms with 1 generation
Cestoidea - Tapeworm
Turbellaria - Free living flatworms
How do the smallest Platyhelminths move?
Ciliary action
How does the connective tissue of Platyhelminthes differ from Cnidarians?
It is cellular in nature
How does waste removal in the Platyhelminthes differ from Cnidarians?
There are structures (protonephridia) used for filtration
Platyhelminths secrete mucous pellets called _____. What are the functions of these?
Rhabdites. The function is to aid in ciliary movement and dry out around the organism, preventing water loss
Describe Class Turbellaria of the Platyhelminthes
Dorsoventrally flattened, quite small, primarily aquatic (mostly marine), Usual live in interstitial areas in benthos. Dvidied into Archoophorans and Neophorans.
Describe the primary difference between the two major groups of Turbellaria in great detail!
Archoophorans - Entolecithal (yolk inside embryonic cells), development may include planktonic larva (usually direct).
Neophorans - Ectolecithal (yolk cells separate from/exterior to embryonic cells, all held within egg capsule), yolk deposited in ovum by yolk cells, development always direct. Some species have separate “yolk glands” called Vitellaria.
Describe the Archoophoran (Turbellaria) reproductive plan
Acoels - have “ovaries” and “testes” that are not necessarily distinct, just embedded in the body cavity. Have a simple copulatory bursa for holding sperm and a simple seminal vesicle and penis
Macrostomida - Testes/ovaries start to become distinct, accessory male reproductive glands (prostate gland) and a penis developed to insert into female gonopore
Polycladida - Multiple branches of overies/testes with distinct uterus
Describe the Neophoran (Turbellaria) reproductive plan. Describe the flow of sperm from testis to female parts
Simple - Lateral oviducts join into common oviduct (serves as site of fertilization)
Have separate organs near genital structures for making yolk protein (Vitellaria).
Testis > vas efferns > vas deferns > seminal vesicle (male) > seminal receptacle (female)
How do Turbellarians undergo asexual reproduction?
Paratomy - formation of 2 or more zooids (buds) along body axis. Fission occurs in multiple places and the organism buds off.
Architomy - Transverse splitting of the body into several pieces, each of which regenerates to form a complete individual AFTER fission
Why is Dugesia sp. considered more “advanced” than hydra?
Have a true mesoderm and are triploblastic.
Describe the digestive systems of Turbellarians
Consists of gland cells and phagocytic cells. May be simple and unbranched or highly branched with diverticula (increased surface area for absorption as well as functioning as a circulatory system), excretion via protonephridia (simple filter cells)
Describe the filtration that occurs in the protonephridia of Turbellarians
Only very small molecules can make it through cells. followed by selective reabsorption of water, toxic materials, etc.
Describe the structure of a flame cell
Walls of cells (1 cell thick) capped by another cell. Water is pushed through the nephridiopore (the hole at the end of the “flame cell” to create negative pressure in the cell. This causes small molecules+water to enter via small slits between the cells making up the walls
Describe the different pharyngeal patterns found in the Turbellarians
Simple - opening directly leads to digestive cavity. Food is not actively pulled into mouth
Plicate pharynx - Mucular pharyngeal tube within a cavity - probably originated as folding of pharynx. Can be protruded
Bulbous pharynx - Pharynx bulges out and cavity is small, separated from the digestive system by a muscular septum
What do Turbellarians eat?
Scavenge, predate, graze, are parasitic, or graze on periphyton
Describe the muscles of the Turbellarians. How do these differ from the Cnidarians?
Platyhelminthes - Circular muscles are directly under epidermis, with longitudinal muscles more inward
Cnidarians - opposite of that
How do Diagonal muscles aid in the movement of Turbellarians?
Contract along edge of organism to undulate, producing crawling movement
How do Turbellarians move?
Ciliary movement - Tiny cilia inch flatworm along
Undulation - Forces generated by undulation of diagnoal muscles
Muscular creeping - circular muscle contraction, squeezing and thrusting the body forward (similar to snake locomotion).
Ditactically - Extending parts of body like amoeba
Contraction - By expanding and contracting muscles in order to move through a substrate (like interstitial spaced in benthos)
Peristalsis to mix gut contents - gut contents mixes to cause forward motion
Secretion of mucous strings - elastic mucous pulls worm from one spot to another
somersaulting - Longitudinal muscles are used in a movement called “looping”. Flatworm attaches to a substrate using duogland organ, inching forward with the opposite end. Then, it attached on that end and releases attachment on the first one.
how do the eyespots of Dugesia work?
Not enough nerve cells to form an image so they just respond to high or low levels of light
How is the nervous system of Dugesia arranged?
Longitudinal, highly innervated genitalia and pharynx, compact near anterior (cephalized). Have distinct eyes, and cells for sensing pressure changes and chemicals.
