Bio 2 Exam 3

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Porifera (main features

• have a simple anatomy

  • have 2 layers, around 15 cell types

  • choanocytes

  • spicules

  • not true tissues (cells are not determined)

• no symmetry in adult (but yes in larvae)

Adult and Larvae Symmetry (Porifera)

• adults - have no symmetry

  • essentially retain genes to be symmetrical but just don’t do it

• larvae - can have radial or bilateral symmetry

  • larva disperses

Choanocytes (collar cells)

• create a water flow

• catch microbes and tiny detritus

Spicules

• are interlocking spikes made of calcium material

• act as support

• help deter feeding from other animals

Practice Question (Phylogenetic Trees) - According to Wang et al. (2010) the oldest fossil sponges, recently found in S. China, had silica (glass) spicules.  This discovery

• does not support the tree here

Microbial Symbioses (mutualism)

• photosynthesis (zooxanthellae)

• colors

• toxins

Medicinal Sponges

• can be used to treat diseases

• e.g. the rope sponge picture here (Aplysina cauliformis) , can be used to treat tuberculosis

obligate symbiosis

• the sponge - provides housing for the shrimp

• the shrimp - provides cleaning service , and eats uneaten microscopic food

Kairou-Douketsu

• young male shrimp enters sponge first

• then female shrimp enters sponge

• shrimp couple mate for life

• they grow together and cannot leave

Cnidaria

• radial symmetry in adult

• 2 “true” tissue layers

  • epidermis, gastrodermis, mesoglea between

• cnidocytes

• medusa and polyp

• incomplete gut - they eat macroscopic food

• organismal integration :

  • nerves

  • muscle

• planula larva

Cnidocytes

• are stinging cells

• discharged from cnidaria to immobilize prey

Medusa & Polyp

• a species can have either one or both of them in their life cycle

• medusas are free flowing

• polyps are often attached to a surface or other polyps

Cnidarian Sample Life Cycle

• both medusa mate and produce an offspring called a planula

• the planula settles and grows and becomes a polyp

• the polyp produces tiny stacks of medusas and eventually buds them off

• the medusas grow until they are mature enough to mate and the cycle begins again

Practice Question (Life Cycle) - In its life cycle, the moon jelly has

• A dioecious medusa stage

Practice Question (Life Cycle) - The life cycle of Pelagiathat you viewed (and shown below) is different from that of Aurelia (on the right) in that Pelagia has no

• Polyp

Practice Question (Cndiarian Phylogeny) - Diversity of cnidarians is associated with changes in:

• sense organs & the life cycle

Corals with colonial polyps

• these polyps have zooxanthellae (dinoflagellates) which :

  • are mutualistic photosynthetic protists

  • they produce most of the food used by coral

Coral Reefs

• coral polyps secret limestone to build the reef, they are essentially ecosystem engineers

• the reefs provide food and protection for fish

Coral bleaching (loss of zooxanthellae)

• hypotheses of what causes it :

  • contagious disease

  • higher ocean

    • temperatures —> heat stress on symbiont

  • adaptation ?

    • gamble to obtain better symbiont strain ?

Sea Jellies (jellyfish)

• most are predators

• prey of sea turtles

• look similar to plastic bags

Box Jellies (cubozoa)

• perform a courtship dance

• have image-forming eyes

Fate of blastospore

• in protosomes :

  • blastospore becomes the mouth

• in deuterostomes :

  • blastospore becomes the anus

Bilaterians

• Deuterostomes

  • radial cleavage

  • blastopore becomes anus

• Protostomes

  • can have either spiral cleavage or idiosyncratic cleavage

  • blastopore becomes mouth

Echinoderms

• habitat : all marine

• pentaradial symmetry as adult

  • larva bilateral symmetry

• endoskeleton

• water vascular system

• simple organ systems

• no head or brain

Echinoderm Symmetry

larvae : bilateral

adults : pentaradial

Epidermis with Spines & Pedicellariae

• tube foot : movement , feeding, respiration

• calcareous plate : provide protection

• spines : provide sea urchins protection against predators, locomotion , sensing

• pedicellariae : tube foot of sea urchins

Echinoderms unique water vascular system

• movement

• feeding

• defense

• “circulation”

• gas exchange

• uses sea water as blood & as hydraulic fluid

Practice Question (Echinoderm Evolution) Echinoderms are limited to marine environments—none have made the transition to freshwater.  This constraint is most likely because of their

Water Vascular System

Practice Question (Echinoderm Phylogeny) - According to this phylogeny, diversity in echinoderms is associated with changes in their

Morphology and Symmetry

Sea Stars

• very common

• are predators

• evert stomach , digest prey before ingesting

Crown of thorns

• great barrier reef

• coral predator up to 25cm

• prey of triton’s trumpet snail

• trumpet snails are sold as bags or ashtrays to tourists , this allows for the sea star to continue destroying the coral reef since there is no predator to stop it.

Practice Question (Great Barrier Reef) - You can help conserve the Great Barrier Reef by doing all of the following except:

Biocontrol of the Triton’s trumpet snail

Sea Urchins (Echindoidea)

• no arms

• spines

• solid test (fused skeleton)

• omnivores , graze algae

Practice Question (Fertilization) - Sea urchins are ____ and achieve fertilization by ____.

Dioecious; spawning w/o mating

Sea Cucumbers (Holothuroidea)

• are soft-bodied

• 1° pentaradial

• secondarily 2° bilateral

• sediment, filter feederd

• are often toxic, which they use as a defense strategy to not be eaten

Practice Question (Symmetry) - Echinoderm larvae have ____ symmetry, while adult sea urchins and sea stars have ____ symmetry.  The sea cucumber adult symmetry is secondarily ____.

Bilateral; radial; bilateral

Sea Pig

• abyssal (100m underwater)

• detritus (decaying matter) feeders

Headless Chicken Monster

• abyssal

• feeds on detritus (decaying matter)

• swims to escape predators (theory)

Chordates

• notochord

• dorsal hollow nerve cord

• post-anal tail

• Pharyngeal slits (homology with hemichordates)

• segmentation - convergent with annelids and arthropods phyla

• closed circulatory system

• are dioecious

• habitat

  • marine

  • water-to-land transition

  • land-to-water transition

Notochord

• flexible rod

• collagen

• muscle attachment

• function (allowing for movement)

• maybe be replaced by bone (derived)

Practice Question (Nerve Cord) - Why does dorsal hollow nerve cord form here?

• it happens as a result of different layers talking to each other telling each other what to do

Practice Question (Notochord) - The notochord is the same as the spinal cord.

False (they are different)

Practice Question (Nerve Chord) - Recall the 3 chordate synapomorphies.  The dorsal hollow nerve cord

• is dorsal to the notochord

Pharyngeal slits

• ancestral

• function

  • feeding

  • breathing

Practice Question (Vertebrae) How do vertebrae develop ?

• the non segment notochord seperates into disks

• the segment muscle block secret a calcium phosphate

Practice Question (Notochord) - Do you have a notochord?

• yes, because it becomes the intervertebral discs

Urochordate (Sea Squirt) anatomy

• siphons

• filter : pharynx

  • slits

  • muscus

  • stomach

Practice Question (Sea Squirt) - With its two siphons and a filter, a sea squirt (Urochordate) obtains food most like a

• Bivalve

Urochordate larva has chordate features

they have a :

• dorsal hollow nerve cord

• notochord

• tail

• pharyngeal slits

• larvaceans : adults retain larva-like features

Ray-Finned fishes

• have complex jaws : two sets of them

  • oral (protrude) - used for suction feeding and grazing

  • pharyngeal (grind)

• have vast diversity (because they are the right size for it)

Innovation of Ray-finned fishes

• eyes + lateral line - senses

• fins - ability to maneuver

• swim bladder - helps with buoyany

• schooling - helps with behavior

Tetrapods (amphibians, mammals, reptiles) - Adaptations to Land

Earliest

• lungs

• limbs

Later

• tough skin

• internal fertilization

• amniotic egg

• flight

Land First - shrinking waterhole hypothesis

limbs and lungs may have evolved from the necessity of having to find new bodies of water as old waterholes dried up.

Limbs First - Woodland Hypothesis

limbs and necks were selected for by scavenging and hunting in shallow-flooded woodlands

Practice Question (Tetrapods) - Paleontologists have calculated that the legs of early tetrapods could not have supported their weight on land.  This mostly supports

The “shrinking waterhole hypothesis”

Reptile Adaptations to Land

• egg shell + internal membranes

  • used for protection, nourishment, gas exchange, and wasted

• keratin scales

  • derived later : feathers and haie

• internal fertilization

• amniotic egg

• parental care

  • clade (crocs/dinos/birds)

Practice Question (Reptiles) - All of the following are adaptations of reptiles, and are shown here, except:

larva stage

Convergent Evolution

• Australia isolated for 40 million years

• Placental and Marsupial animals

Practice Question (Flatworms) - For Platyhelminthes, having a coelom is ____ and not having one is

• Ancestral ; derived

Platyhelminthes : main features

• 3 tissue layers

• No coelom

• Incomplete gut

  • branched

• Little or no cephalization

• Organ systems

  • nervous

  • excretory

• Monoecious (hermaphroditic)

Platyhelminthes Phylogeny

• turbellarians

• trematodes (flukes)

• cestodes (tapeworms)

Practice Question (Acoela) - Acoela were once classified as “Turbellaria.”  Considering the Acoela in their present place on the phylogeny, the original “Turbellaria”

• Polyphyletic

Adaptations of Parasitism

• Cephalization (decrease)

• Digestive System (decrease)

• Reproductive (decrease)

Pork Tapeworm (Cestoda)

functions

• anterior end attached to wall of gut

• posteriorly repeated sections

  • 1) produce gametes

  • 2) fill with fertilized eggs (embryos)

  • 3) are shed in feces

A head is formally defined by

• anterior head

• sense organs

• brain

Segmentation in 3 animal phyla

• distinct, repeated body modules

• specialized for different functions

• developmentally patterned by Hox genes

Pork tapeworm (cestoda) parts

• scolex : hooks and suckers for attachment to gut wall

• proglottids : detachable “packets” of eggs

Practice Question (Tapeworm) - Although it has no sense organs, the scolex of a tapeworm is its head (T/F), and its body shows  “true” segmentation: patterned special-ization of body segments for various functions (T/F).

• False; false

Pork Tapeworm Life Cycle

• Pigs become infected by eating contaminated food or water containing tapeworm larvae, and they act as the intermediate host allowing the larvae to develop in a cyst inside their tissue.

• Eventually the larva hatches inside the tissue becoming an adult tapeworm, and if we eat this meat raw or undercooked, we will get the tapeworm. We are now the definitive host to the adult tapeworm who lives inside our intestines and steals our nutrients.

• Humans also help the tapeworm reproduce by passing its eggs into the environment through our poop, starting the cycle over again.

• The advantage of an internal parasite having more than one host in their life cycle is that it ensures their survival, if something happens to their first host (the pig) they can just attach to another one and live off them instead (the human).

Tapeworm and Cysticercosis

• If humans ingest the egg directly from contaminated water or food instead of the already adult worm from the pig tissue, the larvae will develop a cyst inside our tissues like the brain or eyes

Practice Question (Mollusks) - Based on phylogeny, all of the following are homologies of mollusks except

• No body cavity

Mollusks : Main Features

• Mantle

• Muscular Foot

• Radula

• Cephalization in some

• Reduced coelom

  • nervous

  • excretory

• Well developed organ systems

• Trochophore Larva

Mollusks (Radula)

• used for grazing plants, algae, or animal tissue

Trochophore Larva

• feeding : complete gut

• marine plankton

• no larva : freshwater, land

Practice Question (Mollusk Phylogeny) - According to the characters shown on this tree, mollusk diversity seems to be related to changes in

• the shell, the body form, the circulatory system

Bivalves

• have 2 shells

• abductor muscles

  • shucking cuts

  • huge in “scallops” they swim by opening and closing their shell

• no radula

• not cephalized

Bilvaves : filter feeders

• have an incurrent siphon

• use gills as filter

• excurrent siphon

Gastropods

• herbivores

• grazers

Solar powered sea slug

• chloroplasts from Vaucheria

• litorea

• has v. litorea genes

• can maintain chloroplasts

Triton’s trumpet snail

• found in great barrier reef

• eats crown of thorns sea star

• sea star eats coral

Cephalopods

• are active predators

• avoid predation themselves by camouflage

Squid social & communication

• color

• body language

Practice Question (Mollusks) - The mollusk clade with the most diversity (disparity = difference among them) in how they obtain food is

• Gastropods

Chitons

• weird mollusks

• wandering meatloaf

• 8 plates in shell

Annelida (segmented worms)

• unique segmentation with septa

• setae

• hydrostatic skeleton

• complete processing gut

• well developed systems

  • closed circulatory system

  • ventral nervous system

  • complex musculature

• trochophore larva

Segmentation + complex musculature

• segments divide coelom into fluid filled compartments

• complex muscles can squeeze in different directions

• elongate

• contract

Are Polychaetes (marine worms) a clade ?

• NO

Bobbit Worm

• predator “polychaete” with cephalization

• parapodia : locomotion

• sit and wait

Earth Worms : ecosystem engineers

• mixing

• organic matter

• aeration