Flashcards in BIOL 321 (Inverts.) Deck (194):
Any named group of organisms distinct enough to be assigned a Linnaean category.
A group of members of a taxon that includes all descendants of their defining common ancestor.
A group of taxon members that does not include all descendants of the common ancestor.
What is the defining characteristic of the current distinct phyla in invertebrate biology?
Each phylum represents a unique body plan.
A group whose members are reproductively isolated from members of all other species.
A rankless, hierarchical biological naming system proposed in 1998 as an alternative to Linnaean classification.
When did the last new phylum-level body plans appear?
250 million years ago(!).
Define convergent evolution.
The process whereby similar characteristics are independently evolved by different groups of organisms in response to similar selective pressures.
Define analogous characters.
Features in organisms of different species that resemble each other as a result of convergent evolution.
Define expressed sequence tags (ESTs).
DNA fragments that are complementary to expressed mRNA.
A family consisting of triploblastic acoelomate and pseudocoelomate animals.
What are the 2 major clades of protostomes?
Ecdysozoa (molting animals) and lophotrochozoa.
What is the main purpose of phylogeny?
Understanding the evolution of specific characteristics within a group of organisms.
Which tells us more about phylogeny: homology or convergence?
The direction of evolutionary change (from ancestral to derived state).
What are the 2 main schools of thought in determining evolutionary relatedness?
Evolutionary systematics (classical taxonomy) and cladistics (phylogenetic systematics).
How are organisms classified using evolutionary systematics (classical taxonomy)?
Subjective analysis of homologous characters for degree of similarity or difference between organisms leads to classification of relatedness.
What are the main problems with evolutionary systematics (classical taxonomy)?
It is very subjective, is not well standardized, requires years of experience with the organisms in question, and often leads to paraphyletic groupings based on an intuitive sense of what is similar or different between organisms.
Change occurring within a lineage of organisms.
Define ancestral (primitive; a.k.a. plesiomorphic) state.
The character state exhibited by the ancestor from which current members of a clade have evolved.
Any derived or specialized character.
A derived character possessed by only one descendant of an ancestor, and thus of no use in discerning relationships among other descendants.
Define Bayesian inference.
A statistical technique used to infer the probability that a particular phylogenetic hypothesis is correct.
A technique for evaluating the reliability of a phylogenetic tree by resampling some characters from the original data set (with replacement) at random.
How does bootstrapping work?
Once a phylogenetic tree has been generated, some characters are resampled with replacement at random. Each resampling gives a new data set with some values duplicated and some omitted. The bootstrap value is the % of resamplings that recover the branch in question.
A group of organisms that includes the most recent common ancestor of all its members and all descendants of that ancestor; every valid clade forms a monophyletic group.
The splitting of a single lineage into 2 or more distinct lineages.
The pictorial representation of branching sequences characterized by particular changes in key morphological or molecular characteristics.
Define derived (apomorphic) state.
An altered state, modified from the original (ancestral) state.
Define homologous characters.
Characters that have the same evolutionary origin from a common ancestor, often coded for by the same genes.
In cladistics (phylogenetic systematics), what is the basis for all decisions about evolutionary relationships between species?
The independent acquisition of similar characteristics from different ancestors via convergence or parallelism, creating the illusion of homology.
A technique for evaluating the reliability of a branch of a phylogenetic tree by deleting some % of information at random and rerunning the analysis; the jackknife value is the % of resamplings that recover the branch in question.
Define node (cladistics).
A branching point on a cladogram.
A group of taxa outside the group being studied, used to 'root' a phylogenetic tree and imply the direction of evolutionary changes.
A principle stating that, in the absence of other evidence, one should always accept the least complex scenario.
Any ancestral or primitive character.
Define polyphyletic grouping.
An incorrect grouping containing species that descended from 2 or more different ancestors; members do not all share the same immediate ancestor (but may resemble each other due to convergence).
Define saturation (cladistics).
A situation in which the gene sequences being compared have experienced so many base-pair substitutions that the phylogenetic signal is largely lost.
Define sister groups.
2 groups of organisms descended from the same immediate ancestor.
A derived character shared by the most recent common ancestor and 2 or more descendants, used to define which species/groups are most closely related to each other.
In cladistics, which characters are the most important to establish evolutionary relationships?
Synapomorphies (homologous derived characters) - and these are the -only- characters used!
How does cladistics (phylogenetic systematics) work?
Compare organisms from one group to a closely related taxon (the outgroup) that lies outside the taxa being studied, assuming the outgroup's characteristics represent the ancestral condition, then create a branched cladogram with the least complex (parsimonious) pathway.
How does convergent evolution affect cladistics?
Convergence can create the illusion of false homologies, so that even the most parsimonious tree standing up to statistical analysis can be completely wrong.
What is the difference between cladistics and classical taxonomy w.r.t. molecular data?
Cladistics takes molecular data into account; classical taxonomy does not.
In cladistics, what do differences in base pair sequence represent?
Evolutionary events by mutation (change, insertion, or deletion) of base pairs.
In cladistics, what do base pairs represent w.r.t. ancestral/derived characters?
Each base is a distinct character, so genome comparison compares 100s to 1000s of characters.
What are the problems with cladistics?
Relationships defined depend on the methodology (equipment, stats tests, etc.) used and can be hard to replicate; assumptions of outgroups as ancestral can be wrong; evolution is rarely parsimonious; and molecular data is another realm of problems!
What are the problems with using molecular data in cladistics?
Molecular change/evolution is not uniform even within the same organism, and sequence addition/deletion events can mess up sequence alignment, making comparisons between organisms inaccurate.
What kind of phylogenetic trees are generated from organisms with gene sequences that evolve unusually quickly?
Trees have longer branches that are grouped more closely together - not because the animals are closely related, but because of the rapid evolution of those sequences.
In cladistics, how can base pair comparisons lead to false homologies?
There are only 4 bases to choose from, so molecules from unrelated organisms are very likely to resemble each other by convergence.
What are the benefits of cladistics over classical taxonomy?
Its clear methodology is easy to analyze and duplicate, and less specialized experience with the organisms in question is needed.
What is the limitation of the fossil record in terms of defining evolutionary relationships between organisms?
Issues resolvable by fossils are usually limited to questions within phyla, not among them.
Which is better for understanding evolutionary relationships between different phyla: molecular data or the fossil record?
Molecular data: changes in DNA sequences provide the best chance of understanding relationships among phyla, while the fossil record is limited to relationships within phyla.
Living on land.
Living in the ocean.
Marine organisms living between the physical limits of high and low tides, and thus exposed to air periodically.
Marine organisms living below the low-tide line and thus exposed to air only under extreme conditions, if ever.
Organisms capable of locomotion.
Organisms that are immobile.
Organisms exhibiting only limited locomotory capabilities.
Aquatic organisms with negligible locomotory powers w.r.t. the movement of the medium they live in, and are thus forced to drift or wander.
Define suspension feeders.
Organisms that feed by removing small food particles from the surrounding medium.
Define deposit feeders.
Orgnisms that feed by ingesting sediment, digesting the organic component as the sediment moves through the digestive tract.
Symbionts living near or on the body of the other participant.
Symbionts living within the body of the other participant.
A symbiotic relationship in which both symbionts benefit.
A symbiotic relationship in which only 1 symbiont benefits, but the other is neither benefited nor harmed.
A symbiotic relationship in which the parasite is absolutely metabolically dependent on the host; a parasite may or may not substantially impair the host.
What are the 3 types of symbiotic relationships?
Mutualism, commensalism, and parasitism.
Define transitional forms (w.r.t. symbiotic relationships).
Stages in the evolution of relationships between organisms (e.g. from parasite to predator when the host is killed).
The process of producing many different cells of different types to form an embryo.
What are the 4 basic types of metazoan tissues?
Epithelial, connective, muscle, and nervous tissue.
Which is the most important type of metazoan tissue?
What is the function of epithelial tissue?
It forms the lining of outer surfaces and internal compartments, acting as an interface between compartments and between the organism and its environment.
What are the 3 key features of epithelial tissue?
Intercellular junctions, basal lamina, and apico-basal polarity.
What is the function of intercellular junctions in epithelial tissue?
To control the exchange of material between epithelial cells.
What is the function of basal lamina in epithelial tissue?
Collagen threads act as a specialized connective tissue connecting epithelial cells to their associated structures.
What is the significance of apico-basal polarity in epithelial tissue?
The difference in structures and type and direction of materials secreted and absorbed on either side of the epithelium lets the epithelium control interactions between the organism and the environment, or between different compartments.
What is the basic structure of connective tissues?
Various fibrous proteins (usually collagen) form an extracellular matrix in which cells can freely move about.
What is the function of connective tissues?
To hold other tissues together and maintain shape and structural integrity of the body.
What is the function of nervous tissue?
To transmit information throughout the body by cell signalling.
What 2 types of filaments make up muscle tissue?
Actin and myacin.
What is the function of muscle tissue?
To facilitate movement.
Which tissue types do all metazoans have?
All have epithelial and connective tissue, but not all have nervous or muscle tissue.
What are the 5 lineages of metazoans?
Porifera, cnidaria, ctenophora, placozoa, and bilateria.
What organisms are included in Porifera?
What organisms are included in Cnidaria?
Jellies, anemones, and corals.
What organisms are included in Ctenophora?
What organisms are included in Placozoa?
What organisms are included in Bilateria?
Bilaterally symmetric organisms.
When did the 5 lineages of metazoans most likely diverge?
Define trichotomy (cladistics).
A 3-branch split on a cladogram that indicates some unresolved division from a previous ancestor.
Which metazoans have no nervous or muscle tissue?
Porifera and Placozoa.
What is the difference between the larval and adult forms of sponges (Porifera)?
The larval stage is motile, but the adult is sessile (permanently attached to some hard surface).
What type of feeding mechanism is used by sponges (Porifera)?
Suspension feeding (on bacteria, phytoplankton, etc.).
Define aquiferous system.
A body plan consisting of either a single water canal or a series of interconnected water canals.
What body plan is unique to sponges (Porifera)?
A less sophisticated form of epithelial tissue found in sponges (Porifera) capable of filtering material via intercellular junctions.
What is the simplest body plan found in sponges (Porifera)?
Vase (asconoid; single water canal).
A large opening in a sponge through which water is excreted.
The inner water canal found in a vase sponge.
The small pores in the outer layer of a sponge.
The inner epithelial layer of a sponge, which absorbs food particles from the atrium by phagocytosis.
The outer proto-epithelial layer of a sponge, interfacing with the environment.
How does suspension feeding occur in an adult sponge?
The motion of choanocyte flagella drives water inside through pores, catching food particles in choanocyte microvilli for phagocytosis, and then out through the osculum.
The connective layer between inner (choanoderm) and outer (pinacoderm) epithelial layers of a sponge, made up of archaeocytes.
The cells forming the connective layer (mesohyl) between the epithelial tissues of sponges.
What 2 skeletal elements are found in sponges (Porifera)?
Spicules and spongin.
Skeletal elements of different shapes and mineral composition found in sponges (Porifera).
Skeletal elements made of branched ropes of collagen-like fibres found in sponges (Porifera).
What 2 minerals commonly make up spicules?
Silica and/or calcium carbonate.
A multinucleated cell that can result from multiple cell fusions of uninuclear cells.
What are the defining characteristics of phylum Porifera?
Microvillar collars surround flagella, with units arising from either single cells or syncytia (multinucleated cells).
A type of cell or organism with the ability to alter its shape, primarily by extending and retracting pseudopods.
The ability of an individual organism to distinguish its own tissues from those of another.
What are the functions of collar cells in sponges?
Generate currents to maintain seawater circulation; capture small food particles; capture incoming sperm for fertilization.
What layers make up a sponge body?
Spongocoel (inner cavity); choanoderm (inner layer made of choanocytes, or collar cells); mesohyl (acellular layer filled with archaeocytes); pinacoderm (outer layer made of pinacocytes).
Define gemmules (Porifera).
Dormant sponge structures made of clustered nutrient-storing cells encapsulated by a thick protective covering which hatch after some time to form new clonal sponges.
The attachment of the larvae of barnacles, etc. to a surface.
How do sponges use chemical compounds to discourage predation and fouling?
Either directly, or by modifying the species composition of adjacent bacterial communities.
What are the 3 levels of sponge construction, from least to most complex?
Asconoid, syconoid, and leuconoid.
What are the 4 classes of phylum Porifera?
Calcarea, Demospongiae, Hexactinellida, and Homoscleromorpha.
What are the distinguishing features of class Calcarea (phylum Porifera)?
Spicules made only of calcium carbonate; this class is the only class to contain all 3 sponge body types and contains the only living asconoid forms.
What are the distinguishing features of class Demospongia (phylum Porifera)?
Nearly all leuconoid, with spicules made of spongin and/or silica, but never calcium carbonate; it is the largest class and contains all freshwater species.
What feature is unique to freshwater species in class Demospongia (phylum Porifera)?
Contractile vacuoles to eliminate water from the cytoplasm (the only other organisms with these are protozoans).
What are the distinguishing features of class Hexactinellida (phylum Porifera)?
Bodies supported entirely by interconnected 6-rayed spicules of silica and chitin; syconoid or leuconoid; the entire sponge is syncytial (multinuclear), with no contractile elements (so no pinacoderm).
What are the distinguishing features of class Homoscleropmorpha (phylum Porifera)?
A distinct basal membrane under a ciliated epithelium.
What feature of freshwater sponges is unusual for freshwater invertebrates?
A free-swimming larval stage.
What are the distinguishing features of phylum Placozoa?
Small, multicellular, amorphous, mobile animals with no body cavity, digestive system, or nervous system, made of 2 layers of ciliated epithelial cells with a layer of multinucleated contractile cells in between; only 1 described species.
What is the difference between phylums Porifera and Placozoa?
They have similar body plans, but placozoans are fully mobile (planktonic for part of their lives, and are adapted to glide along hard surfaces by cilia and contractile fibre cells).
What is significant about the genome of phylum Placozoa?
Placozoans have the smallest nuclear genome of any known animal, but the largest mitochondrial genome, and their genome contains genes for transcription factors and signalling genes involved in early embryonic development and cell fate determination in most other animals.
A unicellular heterotroph very similar to choanocytes; possible sponge ancestor.
Which is the most important cell type in poriferans? Why?
Choanocytes: their beating flagella bring in oxygen and food and eliminate waste.
Which class do carnivorous sponges belong to?
How do carnivorous sponges feed?
Spicule-covered tendrils extending from the mesohyl entangle prey; cells from the body flow out and encase it, then secrete digestive enzymes to digest it.
What key structural feature is missing from carnivorous sponges?
What class of sponges was only recently (1990s to 2000s) rediscovered building reefs--the first known since the Cretaceous period?
What conditions are required for establishing a new hexactinellid reef?
High current densities, high silica content in the water, and clean surfaces.
How does glaciation support the formation of new hexactinellid reefs?
By providing clean surfaces for new reefs to build upon.
What is the key ecological impact of hexactinellid reefs?
Their 3D structure in otherwise featureless sediment provides protection and nursery grounds for smaller organisms, promoting biodiversity.
What major vein of research has been conducted on boot sponges?
Propagated membrane depolarization as an intercellular communication mechanism; localized electrical activity has been shown to induce a whole-body arrest of water flow.
Why have boot sponges been used to investigate electrical activity and communication in sponges?
Boot sponges are hexactinellids: their tissues are all syncytial, so any signal would only need to pass through a single continuous membrane.
What organisms are included in phylum Cnidaria?
Anenomes, corals, hydroids, and jellyfish.
Living at the bottom of a body of water.
Living in the water column of a body of water.
What key feature is unique to cnidarians?
What kind of nervous system do cnidarians have?
True nerve cells loosely organized in a nerve net, with signals conducted radially outward from sensory cells; some cnidarians have bundled nerve cells (like ours).
What is the main overall difference between poriferan and cnidarian digestion?
Cnidarians have a true gut for initial digestion; poriferans rely on choanocytes embedded in the inner body wall.
What are the functions of the cnidarian gastrovascular cavity?
Digestion, circulation, and hydrostatic skeletal support.
Why is radial symmetry a good functional adaptation for animals with sessile or sedentary lifestyles?
It allows them to gather food, exchange gases, and react to stimuli around the entire circumference of the body.
What is the difference between poriferan mesohyl and cnidarian mesoglea?
Cnidarian mesoglea contains much more water than poriferan mesohyl, accounting for the characteristic texture and consistency of cnidarian body walls.
Coiled projectile tubules secreted by cnidarian cnidocytes.
Modified cnidarian epithelial cells that secrete cnidae.
A modified sensory cilium on the outer surface of a cnidarian cnidocyte that acts as a trigger for ejection of cnidae.
What chemical process is hypothesized to cause cnidarian cnidocytes to eject their cnidae?
When triggered, Ca++ enters the cnidocyte capsule, increasing the water pressure within; the pressure forces the capsule to turn inside-out, ejecting the cnidae tubule within.
What are the 3 functional categories of cnidarian cnidae?
Glutinants (release sticky stuff), volvents (wrap around prey), and penetrants (stab things with poison).
What is the function of cnidarian interstitial cells?
They remain undifferentiated within the interstitial tissue and can be called upon to divide by mitosis and become various cell types as needed (especially for replacing cnidae).
Why are cnidarian interstitial cells crucial to cnidocyte function?
Cnidae are 1-use-only, so they need to be replaced whenever they are ejected.
What are the 2 major subphyla of Cnidaria?
Anthozoa and Medusozoa.
Which cnidarians are included in subphylum Anthozoa?
Anenomes, soft corals, and stony corals.
What life stages do anthozoan cnidarians undergo?
Polyp only (but with more complex morphology than polyps in other groups).
The cell type forming the poriferan pinacoderm, a proto-epithelial layer covering the outer surface of the sponge.
A flagellated cell type forming the poriferan choanoderm, a proto-epithelial layer lining the internal water canals and chambers of the sponge.
Which is the most complex poriferan structural grade?
What is the difference between calcarean and demosponge choanocytes?
Choanocytes are typically larger in members of Calcarea than in members of Demospongiae.
What type of growth is characteristic of local (PNW) intertidal sponges?
Most are encrusting demosponges.
How do sponges avoid being overgrown by other sessile animals?
By secreting defensive chemicals, either toxic or just gross.
How does acid testing identify sponges?
The acid test differentiates between calcareous and siliceous skeletal elements, so is a good indicator of class membership: acid dissolves CaCO3, but not silica.
What is different about poriferan epithelial tissue compared to most other animals?
The poriferan epithelium has no basal lamina.
What are the 6 major classes within phylum Cnidaria?
Staurozoa, Hydrozoa, Scyphozoa, Cubozoa, Octocorallia, and Hexacorallia.
Which cnidarian classes are included in subphylum Medusozoa?
Staurozoa, Hydrozoa, Scyphozoa, and Cubozoa.
Which cnidarian classes are included in subphylum Anthozoa?
Octocorallia and Hexacorallia.
What makes Staurozoa different from other cnidarians in subphylum Medusozoa?
They have no free-living medusa stage.
What feature separates Medusozoa from Anthozoa within the cnidarians?
Medusozoans have a linear mitochondrial chromosome, while all other cnidarians have a circular mitochondrial chromosome.
Why is alternation of generations an inaccurate way of identifying cnidarian subphyla?
Most medusozoans have a free-living medusa stage, but all members of class Staurozoa and some members of class Hydrozoa are lacking the medusa stage and are polyp-only.
A small, knob-like sensory organ found in scyphozoans (true jellyfish) containing a statocyst, a pigment spot with photoreceptor cells, and chemoreceptor cells.
Define planula larva.
A ciliated, non-feeding, free-swimming larval stage in the cnidarian life cycle formed after fertilization that eventually settles and develops into a polyp.
The polyp form of the scyphozoan (true jellyfish) life cycle that reproduces asexually to form more scyphistomae, and eventually medusae (by strobilation).
In scyphozoans, what happens during strobilation?
The oral end of the scyphistoma undergoes sequential transverse fissions, with segments forming immature medusae that eventually break off and swim away to mature.
An immature medusa released from a scyphozoan scyphistoma after strobilation.
What is the difference between scyphozoan and hydrozoan gametes?
Scyphozoan gametes arise from the gastrodermis, while hydrozoan gametes arise from the epidermis.
Which cnidarians have oral arms in addition to tentacles?
What is the difference between scyphozoan and hydrozoan mesoglea?
Scyphozoans have amoeboid cells in their mesoglea, but hydrozoans do not.
What is the difference between scyphozoan and hydrozoan gastrodermis?
Scyphozoans have cnidocytes in their gastrodermis, but hydrozoans do not.
In hydrozoan medusae (hydromedusae), a rim of muscular tissue projecting inward along the peripheral margin of the bell that allows quick, agile movement.
What is the difference between scyphozoan and hydrozoan sensory structures?
Scyphozoans have sensory structures in the rhopalia studding the bell, while hydrozoans have concentrations of sensory cells at the base of the tentacles.
What is the difference between scyphozoan oral arms and regular tentacles?
Oral arms have no cnidocytes and are used for feeding only.
A colony of hydrozoan polyps.
A feeding hydrozoan polyp specialized for capturing and digesting food.
A non-feeding, reproductive hydrozoan polyp specialized for budding off medusae.
A defensive hydrozoan polyp.
The living tissue of a hydrozoan colony.