BIO 202 Exam 3

What is the closest living relative of animals?

choanoflagellates.

What are the 6 things traits that define/characterize animals?   

• Cell structure: multicellularity

• Mode of nutrition: heterotrophy

• Movement: muscle tissue

• Reproduction: sexually

• Development: all animals possess

How have animal body plans changed since the Cambrian explosion?

They haven’t

What is metazoan organization based on?

Complexity:

• Cellular

• Tissue

• Organ

• System

What organism contains no germ layers?

Sponges

What do triploblastic tissues contain?

3 germ layers:

• Ectoderm (outer layer)

• Mesoderm (middle layer)

• Endoderm (inner layer)

What do diploblastic tissues contain?

• Ectoderm (outer layer)

• Endoderm (inner layer)

What does the ectoderm form?

• Epidermis

• Hair

• Nails

• Skin

What does the mesoderm form?

• Notochord

• Skeletal, cardiac, and smooth muscle

• Lining of the coelom

What does the endoderm form?

• Lining of the digestive tract

• Pharyngeal pouches; tonsils, thymus, and parathyroid

What is radial symmetry and what are its benefits?

• Symmetry around a central point

• Can interact with the environment from all sides

What symmetry do Cnidarians, Ctenophores (as adults) and some sponges have?

Radial symmetry

What is Bilateral symmetry and what are its benefits?

• Symmetry across the sagittal plane; only one way to cut it into equal halves

• Well-suited for forward movement and often associated with cephalization

What are the defining features of Protostomes? (bilaterian)

• Spiral cleavage

• Determinate (mosaic) cleavage

• Blastopore becomes mouth

• Two major subgroups: Ecdysozoa & Lophotrochozoa)

What are the defining features of Deuterostomes? (bilaterian)

• Radial cleavage (cleavage planes are either parallel)

• Indeterminate (regulative) cleavage

• Blastopore becomes anus

• Echinoderms & Chordates

What is an acoelomate body cavity?

• no body cavity; space filled with mesodermal cells

• only found in triploblastic animals

What is a pseudocoelomate body cavity?

• body cavity but not a true coelom as its only partially surrounded by mesoderm

What is an eucoelomate body cavity

• Possess a true coelom that’s entirely surrounded by mesoderm

Why do organisms have segmentation?

• allows for specialization of body regions

• allows functional redundancy (When multiple components perform the same function, so losing one doesn’t cause the function to fail)

What is gamete formation? (1st step of development)

• the process by which gametes are formed via gametogenesis

What are the 2 processes of gamete formation?

• Spermatogenesis: one spermatocyte (diploid) produces four sperm (haploid)

• Oogenesis: One primary oocyte (diploid) produces one egg (haploid) and polar bodies; also produces yolk that provides nutrients to the embryo

What are the 2 things accomplished during fertilization?

• Brings haploid genomes together

• Activates the egg to begin development; can be internal or external

What are the four steps of fertilization?

1. Contact; Sperm reaches the jelly coat

2. Recognition; Species-specific proteins bind to receptors on the egg

3. Fusion; Sperm and egg membranes fuse; the sperm enters the nucleus

4. Syngamy; Sperm and egg pronuclei unite forming a diploid zygote

What happens during cleavage?

• A large cell divides without growing

How are tissues layers formed via gastrulation?

• Invagination; the inward folding of the blastula

What are the four ways to distinguish protostomes and deuterostomes

• Cleavage (spiral vs. radial)

• Cell fate (determinate vs. indeterminate)

• Blastopore fate (mouth first vs. anus first)

• Coelom formation (Schizocoely (splitting) vs. Enterocoely (pouching/pinching)

What level of organization do sponges have?

• Cellular (no tissues, no organs)

What is a Pinacocyte?

• flat sponge cell that forms the outer covering of the sponge

What is a Porocyte?

• tube shaped sponge cell that controls water flow through ostia

What is an Archeocyte?

• an amoeba-like cell that delivers nutrients to cells, and differentiates into other cell types

What is a Sclerocyte?

• a cell that secretes spicules

What is a Choanocyte?

• a flagellated cell that generates water current and filters food particles from water

What is the path of water through a sponge?

• Comes in through the ostia (small pores)

• Flows through incurrent canals

• Water enters choanocyte chambers where it is filtered

• Carried toward the spongocoel (central cavity) via excurrent canals

• Water leaves through oscula (large, visible openings)

How do choanocytes generate current and capture food?

• a singular flagellum lined with microvilli (tiny, finger-like projections of the cell membrane; increasing surface area)

What are the features of the asconoid canal system?

• Single, large osculum

• Water comes in through the ostia into the spongocoel, which is lined with choanocytes

What are the features of the syconoid canal system?

• Single, large osculum

• Spongocoel lining is folded back to make radial canals which are lined with choanocytes

• Choanocytes in radial canals rather than spongocoel

What are the features of the leuconoid system?

• No spongocoel

• Complex folding with choanocyte-lined chambers

• multiple oscula

• Most sponges have this system

What are the defining features of Calcispongiae?

• Calcium carbonate spicules

• Mostly small and shallow water; all 3 canal systems

What are the defining features of Hexactinellida (glass sponges)?

• 6-rayed silica spicules

• Mostly deep sea

What are the defining features of Demospongiae?

• Silica spicules (not 6-rayed), spongin, or both

• Most living species; freshwater & bath sponges; leuconoid

What are the defining features of Homoscleromorpha?

• Small silica spicules, or none

• have a basement membrane; the closest thing to epithelium

How do sponges reproduce?

• Both sexual and asexual

• Asexual via bud formation/fragments

• Sexual: hermaphroditic; fertilization

What are the four things that have allowed sponges to persist for so long?

1. Spicules; skeletal elements that make sponges hard and unpleasant to eat

2. Chemical defenses; toxic/foul-tasting compounds that deter predators & competitors

3. Regeneration

4. Microbial partners; symbiotic bacteria take u; a share os sponge biomass and help produce defensive chemicals

What is the defining trait of Lophotrochozoans?

• have either a permanent lophophore feeding apparatus or a trochophore larvae

What are the defining traits of Phylum Platyhelminthes?

• 1st appearance of bilateral symmetry; Flatworms

• Triploblastic; acoelomate body cavity and a blind (one-way) gut

What is the importance of Platyhelminthes having a flattened body?

• Higher surface area to volume ratio

• Since they have no respiratory or circulatory system, it allows cells to get nutrients & oxygen via simple diffusion

Is there a nervous system present in Platyhelminthes? Are they able to excrete waste and osmoregulate? 

• They have a nervous system, one of the earliest appearances of cephalization, and eye spots (Ocelli)

• Excretory/osmoregulatory system works via flame cells (protonephridia)

What are the defining features of Class Turbellaria?

• Mostly free-living

• Muscles and cilia for movement

• Some gliding over mucous from adhesive glands

What are the defining features of Class Monogea?

• Ectoparasites, mainly of fish

• Single host (direct life cycle)

• Attach to gills and feed on body fluids

• Only damaging in crowded conditions

What are the defining features of Class Trematoda?

• All parasitic flukes (endoparasitic in vertebrates)

• Suckers and hooks for adhesion; minimal sense organs

• Indirect life cycle with a intermediate and definitive hos

• Important parasites of humans and domestic animals

What are the defining features of Class Cestoda (tapeworms)?

• All endoparasites, usually in the vertebrate gut

• No mouth or digestive tract

• Hooks and suckers for attachment (Scolex)

• Usually 2 hosts

What are the defining features of Phylum Bryozoa?

• Moss animals; mostly aquatic sessile organisms; Both freshwater and marine (shallow)

• Bilateral symmetry; radial & mosaic (determinate) cleavage

• Coelomate

How do Bryozoans feed and reproduce?

• Filter feeders

• Asexual: budding

• Freshwater; Statoblasts: hard-shelled asexual capsules that survive freezing and drying

• Sexual; hermaphroditic

What are the features shared by radial animals?

• radial symmetry

• diploblastic; contain tissues

• most have blind guts; ctenophores exception

What are the morphological differences between the polyp and medusa body forms?

• The polyp is the sessile, tube-like form

• The medusa is the free swimming, umbrella-shaped form

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What are advantages of having a life cycle with both polyp and medusa life forms?

• Division of labor; the polyp can stay put in a favorable environment, feed and perform asexual reproduction while the medusae performs sexual reproduction, allowing for better dispersal and the opportunity to get to a better habitat?

Where do you find the cnidocytes and how do cnidocytes and nematocysts work in prey capture and defense?

• Cnidocytes are specialized stinging cells that are found in the epidermis

• When the cnidocil (modified cilium) detects touch or pressure, the operculum (lid) opens, leading to the cnidocytes discharging the nematocyst

What are the defining features of Class Hydrozoa?

• Commonly colonial; organized as a branching stalk of polyps

• Medusa stage present; typically includes polyps and medusae

• Asexual via budding; Sexual fertilization with medusa

What is the life cycle of Hydrozoans?

A polyp colony asexually buds medusae. Medusae release gametes; fertilization produces a planula larva, which settles and becomes a new polyp colony.

What are Gastrozooids, Gonozooids, and Dactylozooids?

• Gastrozooid: feeding polyp

• Gonozooid: reproduction polyp

• Dactylozooid: defense and prey capture polyp

What are the defining features of Class Scyphozoa?

• True jellyfish, mostly floating

• Medusa dominant

• Move by pulsing the bell

What is the life cycle of a scyphozoan (true jellyfish)?

Adult medusae release gametes, and fertilization produces a ciliated planula larva. The planula becomes a small polyp (scyphistoma) which buds and releases juvenile medusae called ephyrae. Ephyrae grow into adult medusae.

What are the defining features of Class Cubozoa?

• Box jellies with bells

• Dominant form: medusa

• Fast swimmers; can produce fatal stings

WHat is the life cycle of Cubozoans?

Adult medusae release gametes, producing a planula larva. The planula settles as a small polyp, which can bud more polyps. Each polyp then metamorphoses entirely into a single juvenile medusa, which grows into an adult.

What are the defining features of Class Anthozoa?

• All polyps, no medusa stage

• Sea anemones. corals

• Calcium carbonate skeletons

• Have zooxanthellae (symbiotic algae) living in their tissues

What is the symbiotic relationship between anthozoans and zooxanthellae?

Zooxanthellae supply sugars and other nutrients and boost calcification. The coral provides shelter, CO₂, and nitrogen wastes.

How do anthozoans reproduce?

Sexually: gametes are released by broadcast spawning (external fertilization) or brooded internally, forming a planula larva that settles as a new polyp. Asexually: budding, fragmentation, longitudinal fission, and pedal laceration.

What are the defining features of Ctenophores?

• Comb-like plates (cteno)

• Colloblasts (specialized glue cells found on tentacles)

• Complete gut

How do ctenophores reproduce?

Mostly sexually. They are hermaphrodites whose gametes are released through the mouth or body wall for external fertilization. Development is direct(no polyp or medusa stage). Asexual reproduction is rare, though some can regenerate or fragment.

What are the 6 defining traits of molluscs?

• Radula (rasping feeding organ)

• Mantle (secretes shell)

• Muscular foot for locomotion

• Complete respiratory system with gills or lungs

• Circulatory system with a heart

• Ciliary tracts

What are the 3 parts of mollusks body plan?

• Head-foot (contains feeding, locomotory, and sensory organs)

• Visceral mass (contains digestive, circulatory, respiratory, and reproductive organs)

• Mantle (secretes shell)

What are the mollusks embryonic features?

• Triploblastic (3 germ layers)

• Protostomes (1st mouth)

• Spiral & Mosaic Cleavage

• Coelomates (via schizocoely)

Most molluscs have an open circulatory system. What does that mean and how does it compare to open circulatory systems?

• An open circulatory system means blood isn’t always confined to vessels

• In a closed circulatory system, blood stays confined to vessels

What is the process of torsion and what are the pros and cons?

• The anus comes toward the mouth creating the mantle cavity

• Pros: Protection

• Cons: Fouling

What is the process of coiling and what are the pros and cons?

• Coiling is the winding of the shell into a spiral

• Pros: Mobility, Less Stress due to weight, Protection

• Cons: Asymmetry (leading to organisms losing organs on one side to balance), Imbalance, Limited flexibilty

What are the defining traits of Gastropoda?

• If present, shell is in single piece (except nudibranchs)

• Undergo torsion in larval stage (veliger)

• Undergo coiling of shell and visceral mass

How do Gastropods feed and perform respiration?

• Feed with a radula

• Some use cilia or mucous for food capture

• Usually one efficient gill or lung

How do Gastropods reproduce?

• Usually dioecious, some hermaphroditic

• Internal fertilization

• Offspring encapsulated in egg cases/capsules

What are the defining traits of nudibranchs?

• Show detorsion; no shell

• Warning coloration

• Get defenses such as nematocysts or toxins from cnidarians and sponges

What are the defining features of Class Bivalvia?

• 2 shells (valves)

• Most are filter feeders (no radula)

• No head (reduced cephalization)

• Most marine

• Open circulatory, excretory, and respiratory systems present

How do Bivalves open and close?

• Dorsal ligament (opening)

• Adductor muscles (closing)

How do Bivalves move?

• Foot is extended between valves, blood is pumped, causing it to swell and act as an anchor

• Some bivalves are sessile

How do Bivalves reproduce?

• Most dioecious; some hermaphroditic and some oysters can chnage sex

• Broadcast spawners (eggs & sperm released into water); one oyster can release 1 million eggs

• External fertilization

What are the defining traits of Class Cephalopoda?

• All marine & carnivorous

• Shell reduced; absent in Octopus

• Highly modified foot, moved toward head

• Locomotion via jet propulsion through siphon

What is a siphon?

• Tube-like structure near the head

• Modified mantle cavity opening; main outlet for water

• Central to jet propulsion

How are Cephalopods composed?

• No cilia on gills

• Large brain; complex eyes with excellent eyesight (colorblindO

• Ink gland for defense

How do Cephalopods reproduce?

• Dioecious; courtship via colorful displays

• Male’s modified arm (hectocotylus) transfers sperm packets (spermatophores)

• Large, yolk-rich eggs

• Direct development

• Semelparous (breed once and die)

How do cephalopods communicate?

• Chromatophores (pigment cells in the skin)

• Expand and contract to induce color changes

What are the defining traits of Annelida?

• 1st appearance of segmentation/metamerism

• Coelom segmented w/septa (thin will of tissue)

• Setae (bristle-like structures composed of chitin) for locomotion or an anchor

• Complete digestive system, nervous system, excretion, closed circulation, respiratory system

• Trochophore as ancestral larval form

What are the traits of Annelid embryonic development?

• Triploblastic

• Protostomes

What unites Clade Ctillata?

• All possess a reproductive structure called the clitellum

• Ring of secretory cells around the body

What is the difference between oligochaetes and leeches?

• The clitellum is always visible in oligochaetes; present only during the reproductive seasons in leeches