Biology 202 : Diversity of Life II
Review: Lectures 2-8
Lecture #2: Introduction to Invertebrates
- Who are the invertebrates: 1) Diploblasts and Triploblasts 2) Protostomes
( Iochotrophozoans and Ecdoysozoans) and Deuterosomes 3) Acoelomates,
Pseudocoelomates and Coelomates( Schizocoelous and Enterocoelous)
- Why study the invertebrates: 1) abundance 2) ecosystem significance 3) food 4)
diseases 5) pests 6) natural products 7) research
- Animals that lack a backbone ( not vertebrates). They Include many phyla and their
taxonomy is regularly changing ( as science is progressing we are finding more and
more ways to sort these organisms and discover that techniques once used are not
reliable). They can be “subdivided” into different groupings based on different
- Tissue Layers: 1) no tissue layers : Placozoans & poriferans( basically collections of
cells, most primitive state of invertebrates) 2) two tissue layers: Diploblasts ( two basic
layers possible interlayer space). 3) three tissue layers ( triploblasts)
- Triploblasts are often further divided into groups based upon the nature of coelom ( an
internal body cavity). 1) acoelomate: no body cavity 2) pseudocoelomate: forms between
endoderm and mesoderm. 3) Coelomate: forms within the mesoderm ( i) Schizocoelous:
splitting of mesoderm ii) Enterocoelous: folding of mesoderm, creating pockets.
- Groups based on the embryonic origin of the mouth: 1) No mouth: Placozoans &
Poriferans 2) Mouth arising from embryonic blastopore ( Protosome = First mouth) 3)
Anus arising from embryonic blastopore ( Deuterostome = Second mouth)
- Protosomes are often further divided into : 1)Lophotrochozoa: combination of two groups
having one of the other of i) lopho: a fan of ciliated tentacles around the mouth ii) troche:
bands of cilia that circle the body of the larva. 2) Ecdysozoa : share an ability to molt.
- Cnidaria :
- Ecdoysozoa: Arthropoda: i) Trilobitomorpha ii) Chelicerata
- Deuterostomia : - They are the most abundant species of eukaryote group (almost ¾ of the 1.75million
- Perform many key ecosystem services : 1) pollination 2) soil turnover 3) dung burial 4)
- Also: 1) Used as food for humans, other animals and other organisms. 2) Diseases of
humans and other animals. 3) Agricultral pests. 4) Sources of non-food products 5)
Models in medicine and research.
- Learning Objectives : 1) Recognize higher level phylogenic relationships of
invertebrates 2) identify the groups that belong within lophotrochozoa( have either a fan
of cilia or a ring of cilia), ecdysozoa( can molt), protosome (Mouth first) and
deuterostomes (Mouth Second) 3) Discuss the roles of specific types of invertebrates in
ecosystems and human biology.
Lecture #3: Protists
- Protists are a polyphyletic group of single celled organisms from 6 ohylogenetically
distinct “super groups”.
- Animal like protitst are protozoans ( found withing 4 of the 6 groups)
- One ( or more ) protists was the last common ancestor of all animals
- How animal like protists are different than plant like protists: 1) metabolism:
chemoorganitrophic, not autotrophic 2) cell structure: cell membranes but no cell wall 3)
organelles: mitochondria( usually) but no chloroplasts ( usually) or other
plastids( usually). 4) activity: movement( via cilia, flagella or pseudopodia)
- How protists vary from other animals: 1) no collagen or chitin( no extracellular matrix) 2)
Unicellular ( though some form aggregates).
- Since they are unicellular, they do not need specialized cells but simple specialized
regions of the membrane that allow for entry / exit of nutrients and waste, locomotion.
- Most of the ususal stuctures are seen in single cells of eukaryotes within additional
features seen in most protozoa: 1) pellicle: microtubule- based network underneath the
plasma membrane. 2) Cytopharynyx: a mouth like region that brings food particles
inwards. Food is internalized by endocyctosis. 3) Cytopyge: anus like region where
empty vacuoles are released via exocytosis.
- Aquatic organism: Marine species are in osmotic equilibrium with seawater. Freshwater
species take on water and must expel it ( via exocytosis of contractile vacuoles) .
Endoparasites are found in the internal fluids of animals
- Free-living “ hunters”( chase down or run into their prey to obtain nourishment) ,
parasites or symbionts - Two types of binary fission in protists: longitudinal and transverse
- Protozoa: 4 groups : 1) Excavata 2) Amoebozoa 3) Rhizaria 4) Chromalveolata.
- Excavata: possess a feeding groove ( cytostome) that brings in suspended food particles
directed by a posterior flagellum, close relatives may lack photosynthesis and use the
flagellum ot obtain nourishment. 3 groups within: 1) Fornicata ( Giardia; giardiasis) 2)
Parabasalia ( Trichomonas vaginalis; trichomoniasis) 3) Euglenzoa ( trypanosome
brucei; sleeping sickness, Leishmania; leishmaniasis)
- Amoebozoa: amoeboid movement via lobopodia, can be multinucleated, mitochondria
with tubular cristate. 3 groups within: 1) Tubulinea( Ameoba; harmless) 2)
Acanthamoebidae ( Acanthanmeobida; usually harmless). 3) Entameobida (Entameoba
histolytica: amoebic dysentery)
- Rhizaria: thin pseudopodia( filopodia) or axopodia (filopodia supported by microtubules).
Planktonic unicellular or colonial forms . Produce hard shells ( tests or capsules) that
remain on death. 2 groups within: 1) Forminifera: produce chalk shells (tests ) that are
abundant in marine deposits 2) Radiolaria: radially symmetric protoszoans with a porous
wall ( capsule) through which filiopodia extend.
- Chromalveolata: very diverse group ( autotrophic, mixotrophic, heterotrophic). All
possess a unique plastid ( though secondarily lost in some). 4 groups , but we will
consider only the Alveolata, which has 3 main groups: 1) Dinoflagellates ( pigmented
protists; red tide) 2) Apicomplexa ( parasites including Plasmodium; malaria,
Toxoplasma, Crytosporidium) 3) Ciliophora ( ciliated protists such as Paramecium )
- Taxoplasmosis: common in feces of domestic cats. Mothers can pick it up and be
asymptomatic. Fetus can be infected with severe consequences.
- Ciliates : some of the most complex protists, wide distribution in freshwater and marine
systems, most have cili rather than flagella ( used for locomotion and feeding ), rigid
pellicle give fixed shape, distinct mouth ( cytostome) dimorphic nuclei ( macro and
micronucleus), complex feeding and defense strategies. Use trichocysts to make them
bigger and difficult to eat ( defensive mechanism)
- Learning objectives: 1)Identify the various supergroups and major groups of protists
( know their phylogenetic relationships & main features) 2) know the terminology
required to describe the various groups, 3) compare and contrast the main groups
4)know the basic biology of the examples linked to human diseases.
Lecture #4: Multicellularity
- Review of Protozoans = Amoeboza: Tubulinea ( Ameoba), Acanthamoebidae
(Acanthameobida), Entameobida ( Entamoeba). Rhizaria: Foraminifera, Radiolara.
Chromaveolata Alveolata: Dinoflagellates ( Gymnodinium), Apiocomplexa
(Plasmodium; Toxoplasma, Crytosporidium), Ciliophora( Paramecium, Didinium). Excavata: Fornicata(Giardia), Parabasalia ( Trichomonas vaginalis), Euglenozoa
( Trypanosoma; Leishmania)
- Choanoflagellates: ancestors of animals. Prior to 600mya there were no animals, and
the next 100my saw the being of all major phyla in the Cambrian explosion. First true
animals likely arose from an ancestor shared with Choanoflagellates.
- How many times did multicellularity arise? At least 17 eukaryotic clades independently
acquired some form of multicellularity. Most familiar groups are plants, fungi and animals
( metazoans). Also occurred in other eukaryotes , such as ciliates, chrysophytes,
diatoms & green algae. Even bacteria and archae include examples of multicellular
- How do cells come together? The colonial hypothesis suggests cell first come together
by aggregation( suggest that first animals would have been radially sysmmetrical). The
syncytial hypothesis suggests cells just fail to separate following cell division ( suggests
that first animals would have been bilaterally symmetrical).
- What is required to go unicellular to multicellular? First animals probably resembled
modern sponges : simple three dimensional organization with some cell speciallizations (
no tissue layers and no distinct “extracellular space”) . Evolution of more complex
multicellular organism required solutions to a number of challenges: 1) adhesion
between cells ( cell to cell connections ). 2) cell specialization 3) communication
- How cells stick together: 1) Plants: cellulose. 2) Fungi : chitin 3) Animals have no similar
material. So animals use a number of methods to counter this. To counter changes in
cell volume, they have developed Na+K= ATPase to maintain osmotic balance. To
develop intimate interactions between cells , cells developed the ability to produce
membrane proteins that interact with molecules on adjacent cells which gives the cells
the ability to send and recieve transmissions between cells , animal radition coincided
with the invention of collagen ( gives structure)
- Choanoflagellates have 23 gene encoding different cadherins. These proteins allow
animals to attach to each other. They have other functions such as prey capture surface
attachment and signaling.
- Animal evolution included an increase in the number and type of proteins that allow cells
to interact som: 1) provide adhesion between cells. 2) create barriers across cells. 3)
permit communication between cells. 4) anchor cells to a substrate, including
- All cells of a multicellular animal have the same genome: how do cells become different?
Transcriptional control of gene expression & permits cells to have different fates
( differentiation). - How did evolution permit even greater complexity and novelty : 1) gene domain shuffling
( receptor tyrosine kinase gene family) 2) Evolution of gene regulation ( transcriotion
factor control development) 3) gene duplication and divergence ( myosins )
- Tissues types: collection of cells ( one of more types) specialized for a specific function.
- Common types: 1) Epithelial tissues: Squamous ( simple, stratified) cuboidal & columnar.
2) connective tissue : loose, fibrous , cartilage & bone. Adipose tissue, Nervous tissue &
Muscle tissue: skeletal, cardiac & smooth.
- Patterns of Organization: 1) Asymmetry: absence of a central point or axis. 2) Symmetry:
arrangement of parts around a central point of axis. Types of Symmetry: 1) Radial:
where any plane passing oral-aboral divides the organism into mirror images. 2)
Bilateral: where a virtual plae could divide the organism into two mirror images,
- Animals tend to move in one direction ( towards anterior). Often some degree of
cephalization ( anterior concentration of sensory, nervous & feeding structures)
- Embryonic Development: 1) Cytoplasmic organization: single cells, no organization. 2)
Diploblastic: two cells layer formed during embryogenesis. 3) Triploblastic: three cell
layers formed during embryogenesis.
- Why is a coeolom important to animal evolution? 1) more space for organ development.
2) more SA for diffusion. 3) can be used as a storage area. 4) can be hydrostatic
skeletons. 5) can be route for expelling waste and/or gametes. 6) body size an increase
independent of body mass.
- Protosomes: first mouth, mouth forms at the embryonic blastopore, (ecdysozoa &
- Deuterostomes: second mouth, blastopore become anus, and mouth forms secondarily,
( echinoderms, hemichordates & chordates).
- Learning objectives : 1) Define important terms such as: a) protosome, b) deuterostome,
c) diploblast, d) triploblast, e) coelomate, f) acoelomate, g) bilateral symmetry, h) radial
symmetry. 2)Apply these terms to specific groups, 3) Compare different ways animal
tussues are organized. 4) compare different developmental patterns and the implications
for the origin of body cavities, 5) Discuss what must happen for organisms to transition
from uni to multicellular, 6) Disucss advantages and disadvantages for uni and
Lecture #5: Soft Things
- Porifera, Cnidaria &Ctenophora: the most basic of all animals
- Placozoa(flat animals): one species is a free living sheet of cells, cilia propel the animal
over substrate, phylogeny is unsolved( assigned to various groups based on
morphology, DNA and development). - Myxozoa (slimy animals): Once considered a protozoan ( may or may not be a
cnidarian), 300+ speices of simple parasites, Myxoblous cerebralis cause whirling
disease in salmon.
- Porifera ( Sponges)
- means pore bearer, about 9000 species in 3 classes: 1) Calcarea ( calcareous sponges).
2) Hexactinellida( glass sponges). 3) Demospongia ( bath sponges) Spongillidae is the
sole freshwater family (23 genera)
- Body plan: No tissues or organs: just cells , including pinacocytes ( porocytes),
amoeboid (mesenchyme) cells, choanocytes. Non-cellular bits: mesohyl layer (like jello),
spicules & sponging ( for support).
- Cell types: Pinacocytes make up body wall. Specialized porocytes form pores and
myocytes are contractile. Amoeboid cells move trhouhg mesohyl layer responsible for
reproduction, spicule formation & food particle transport. Choanocyte uses its flagellum
to generate water currents.
- Reproduction: Sexually and asexually. Asexual: fragmentation, budding or cysts
( gemmules are cysts of ameobiod cells that survive after death of adult). Sexual:
Monoecious ( eggs and sperms produced at different times), gametes arise from meiosis
of diploid cells ( choanocytes and amoeboid cells), sperm broadcast to water but oocytes
may be released or retained in mesohyl, zygotes develop into flagellated larvae, settle
and develop into juvenile sponges.
- Physiology: 1) Digestion: cell by cell. 2) Excretion: cell by cell. 3) Nervous system: no
nerves , but have genes needed for neuronal function. 4) Circulation: choanocytes
create “outer” current but no circulatory fluid inside. 5) Respiration: cell by cell.
- Cnidaria ( Nettle , as in the spiky plant)
- 9000 species divided into 5 classes: 1) Hydrozoa (Hydra, Obelia) , 2) Scyphozoa (True
jellyfish: Aurelia, 3) Cubozoa (box jelly fish), 4) Anthozoa ( anemones , soft & stony
corals), 5) Staurozoa (stalked jellyfish).
- General Features: Radial or modified, biradial symmetry. Cnidocytes ( stinging cells).
Diploblastic: epidermis & gastrodermis.
- Reproduction: Most are dioeciosu and show “alternation of generations”. Two stages : 1)
polyp stage: sessile form with asex. 2) medusa stage: motile with sex.
- Hydrozoans: Nematocyts only in the epidermis. Gametes released directly into the water
( not via gastrovascular cavity). Acellular mesoglea. Polyps form colonies with some
becoming specialized ( feeding, budding, or defence). Hydra is an exceptional
hydrozoan: 1) freshwater species, no medusa stage, polyps can bud or untake meiosis
to form gametes for sexual reproduction. - Hydrozoa: a colony of different specialized polyps: 1) pneumatophore ( gas bag), 2)
dactylozooid (defence) 3) gonozooid (reproduction