BIO FINAL FLASHCARDS

Common Characteristics of Animals

Multicellurlarity

• body composed of many specialized cells

• allows division of labor among cells

Heterotrophs

• cannot photosynthesis

• ingest/absorb nutrients from other organisms for energy

• drives feeding adapatations throughout kingdom

No Cell Walls

• plasma membrane only

• enables flexible movement and cell shape change

Muscle TIssue

• cells that contract, unique to aniamls

• powers locomotion and internal movement

Nerve Tissue

• specialized cells that transmit electrochemical signals

• allow sensation and coordinated response

Extracelluar Matrix (ECM)

• structural scaffolding outside cells (includes collagen)

• supports tissues and unique to composition in animals

Hox Genes

• master regulatory genes controlling body axis pattern

• mutations = major changes in body plan

Similar rRNA sequences

• ribosomal RNA is highly conserved across all animals

• evidence of shared common ancestry

Characteristics of Cell Junctions

• coordinate cell communication and tissue integrity

History of Animal Life

• End of Porterozoic era - first multicellular animals

• CAMBRIAN EXPLOSION - sudden diversification

• First vertebrates (fishes) and plants colonizing land

• Tetrapods move onto land

• Repitles dominate

• Repitles decline and mammal diversity goes on

Cambrian Explosion Theories

1. Favorable Environment - warming temps, rising atm. O2 + aquatic O2 —> development of ozone layer to block UV radiation

2. Hox gene evolution - complex and more varied body types/plans

3. Evolutionary Arms Race- predatory/prey co-evolution drove rapid diversification of both offensive and defensive features

2 Major Categories of Animals

• Invertebrates- sponges, jellyfish, worms, insects, crutaceans

• Vertebrates - amiphibians, fish, reptiles, birds, mammals

Bauplan

• basic body design/ground plan of major taxonomic groups

1. establish evolutionary relationships- framework to organize bauplans and compare them

2. identify functional principals - physcial, chemical, physiological, ect.

3. Integrate structure and function in evolutionary context

Body Symmetry & Planes

• Frontal plane —> divides dorsal (back) from ventral (belly)

• Sagittal Plane —> divides right from left

• Transverse Plane —> divides anterior from posterior

Radial Symmetry

• body parts arranges around central axis → no distinct left and right

• Riadata - animals wit radial symmetry

• Oral surface- mouth facing up

• Aboral surface- opposite the mouth

• Sac body plans

• Sensory structures are scattered around the entire outer body edge (because they encounter the environment from all sides simultaneously)

• Passive movement - not actively pursuing prey

• no central nervous system - nerve net only

Bilateral

• left and right mirror images

• only one plane

• cephalization - concentration of nervous tissue, sensory organs and feeding apparatus in a distinct head

  • encounter environment head first

• drives the evolution of CNS

• suits animals for forward directional movement - active predation and stuff like this

Body Plans

• Sac - one opening and gastrovascular cavity

• Tube-within-a-tube - two openings (one mouth and one anus) complete digestive tract

Metazoa Ground Plan- Tissue Types

Epithelia

• joined cells resting on the basal lamina on ECM

• often ciliated

• cover body surface + line cavities

Connective Tissue

• Cells separate by ECM (made of ground substances + fibers)

• organized into skeleton: endoskeleton (internal) and exoskeleton (external)

Body Cavity (Coelom) Types

Coelom:

• A fluid-filled space surrounding the gut in which internal organs are suspended

• In humans = the abdominopelvic cavity (contains liver, stomach, intestines, etc.)

• Organs are anchored to body wall by mesenteries (bands of connective tissue derived from mesoderm)

Benefits of Having a Coelom:

• More space for internal organ development

• Greater surface area for exchanges

• Better storage capacity

• Supports hydrostatic skeleton (fluid provides pressure for movement)

• Allows increased body size and complexity (bigger = harder to eat)

Aceolomate

• no body cavity

• solid Parenchyma fills body between gut and body wall (endoderm and ectoderm)

• Ex. flatworms

Psuedoceolomate

• cavity present but not fully lined by mesoderm

• only lined on the outside of the mesoderm

• Derived from orginal hollow chamber of blastula (blastocoel)

• “false body cavity”

Eucoelomate

• TRUE coelom fully lined by mesoderm

• fully lined on all sides of the mesoderm-derived tissues

• mesoderm surrounds the gut and lines the body wall with fluid-filled chamber between

• Mesentaries (mesoderm) anchor organs to body wall

Segmentation

• body divided into repeating units - segments/metameres

• allows speclalization of body regions

• Found in Annelida, Arthropoda, Chordata

Benefits of segmentation:

• Provides backup organs — if some segments are damaged, others remain functional

• Allows more efficient movement — body regions can move independently of each other

• Allows specialization of body regions — distinct head, locomotory segments, reproductive segments

• Promotes a more well-defined head end (cephalization)

Body Size

Animals > Protozoan > Prokaryotes

Levels of Organization

1. Cellular Organization

• Phylum: Porifera (sponges)

• Aggregations of cells with specialized functions

• Division of labor between cells, but NO true tissues

• Cells not tightly coordinated into tissues

2. Cell-Tissue Organization

• Phyla: Cnidaria, Ctenophora

• Groups of similar cells arranged in definite layers with a common function = tissue

• Still have many scattered, unorganized cells

• Only 2 tissue layers (diploblastic)

3. Tissue-Organ Organization

• Phylum: Platyhelminthes (flatworms)

• Tissues organized into organs

• An organ = multiple tissue types working together for a very specialized function

4. Organ-system Organization

• Groups: Lophotrochozoa, Gnathifera, Ecdysozoa, Chordates — essentially everyone else

• Groups of organs working together = organ system

• 11 body systems

11 Body Systems

• Integumentary

• Skeletal

• Muscular

• Nervous

• Digestive

• Respiratory

• Circulatory

• Excretory

• Endocrine

• Immune

• Reproductive

Muscular - 3 types of muscle tissue

Cardiac

• Heart (vertebrates)

• Involuntary

• Provides contractility to pump blood through cardiovascular system

Skeletal

• Attached to bones

• Voluntary or involuntary

• Striated; regular arrangement of actin and myosin; primary locomotion muscle

Smooth

• Internal organs

• involuntary

• Most widespread type across the animal kingdom; moves materials through the body

Skeletal - 3 types

Hydrostatic Skeleton

• Fluid-filled body cavity under pressure; muscles squeeze against fluid to produce movement

Exoskeleton

• Hard external covering; muscles attach to inside

  • shell = skeleton

  • muscle on the insud

Endoskeleton

• Internal bony/cartilaginous skeleton; muscles attach to outside

  • muscle around the bones

• Support and maintain body shape

• Attachment point for muscles (lever system)

• Storage of minerals (e.g., calcium in bones)

• Protection of internal organs

• Bone marrow = additional storage and blood cell production (vertebrates)

Nervous System

Sensory reception → analysis → coordinated motor response

• helps keep animal out of danger and centered around around reproduction

• Photorecptors - detect light → eyes

• Chemoreceptors - detect chemicals → smell, taste

• Special senses- eyes, ears, statocysts (balance)

• Simple animals: collections of nerve cell bodies called ganglia

• Vertebrates: brain + spinal cord = central nervous system (CNS)

Endocrine System

• System of scattered organs that produce hormones (chemical messengers)

• Hormones travel throughout the body via the circulatory system

• Produces long-term responses — hours, days, or even years (vs. nervous system = immediate)

• Functions: regulate growth, metabolism, nutrient use, sexual development, sexual functioning

• In humans, sexual regulation begins at puberty and continues throughout most of the lifespan

Circulatory System

Opened Circulation

• pumped into open body cavity found in most invertebrates

• arteries and veins are not connected

• open spaces

• large fluid volume

• low pressure

• exchange in open spaces

Closed Circulation

• blood confined to vessels

• arteries + veins + capillaries are all connected

• small fluid volume

• high pressure

• exchange at capillary beds

What the circulatory system transports:

• Oxygen delivery to all cells (needed for aerobic respiration)

• Nutrients from the digestive system

• Hormones from the endocrine system

• CO₂ removal (byproduct of cellular metabolism)

• Nitrogenous waste (ammonia) removal

Lymphatic System

The least well-studied and least familiar body system — but important!

• A series of vessels that travel alongside veins (always shown in green in diagrams)

• Picks up excess fluid from tissues and returns it to the cardiovascular system

• Maintains constant blood volume

• Absorbs fats from the GI tract that are too large to enter blood vessels directly

• Intimately tied to the immune system via lymph nodes

Lymph Nodes:

• Small bean-shaped structures along lymphatic vessels

• Filter lymph fluid and provide immune defense

• Immune cells encounter foreign material here first

• Swollen lymph nodes = sign of infection (doctor checks neck region because respiratory/oral entry points are nearby)

• Common entry for disease: respiratory passageways and oral cavity → lymph nodes in neck are first line of defense

Only vertebrates have a true lymphatic system. Invertebrates have cellular-based defenses only.

Respiratory System

• Goal is to get O2 and get out CO2

• Pulmonary Ventilation- the physical act of taking in air and expelling air (breathing)

• Respiratory and circulatory systems are connected

Digestive System

Sac Body Plan (Incomplete Digestive System)

• Only ONE opening — serves as both mouth AND anus

• Cannot eat continuously (must stop to expel waste first)

• Cannot have highly specialized gut regions

• Associated with quieter, less active lifestyles

• Example: Cnidaria, Platyhelminthes

• The single cavity = gastrovascular cavity (gastro = digestion + vascular = transport; one cavity does BOTH)

Tube-Within-a-Tube (Complete Digestive System)

• TWO openings — mouth at one end, anus at other

• Can eat continuously — waste exits while new food enters

• Allows regional specialization of gut:

  • Ingestion region

  • Mechanical/chemical breakdown region

  • Absorption region

  • Waste elimination region

• Associated with more active, complex lifestyles

• Example: Annelids, Molluscs, Vertebrates

Excretory System

Nitrogen waste comes from breaking down proteins

Ammonia

• Most toxic

• lots of water needed for diffusion

Urea

• intermediate toxicity

• less water needed

Uric Acid

• least toxic

• virtually no water needed

• bird droppings are semi-solid white paste —> allows maximum water conservation in dry environments

Different anmals have different excretory structures

Reproductive

The reproductive system is fundamentally different from all other body systems:

• All other systems = necessary for individual survival (homeostasis)

• Reproductive system = necessary for species survival (passing genes to the next generation)

• An individual can survive without reproducing — but the species cannot survive if NO members reproduce

• Brings egg and sperm together → passes traits to next generation

• Meiosis produces haploid gametes (sperm and egg)

• Fertilization → diploid zygote

• Zygote undergoes mitosis → multicellular embryo → adult

• All somatic (body) cells contain the same DNA as the original zygote

• Giant Panda = 42 chromosomes | Humans = 46 chromosomes

Protosomes vs Deuterosomes

Protostomes

• Mouth = first opening

• spiral cleavage

• Determinate = cells fate is fixated early

  • if you seperate one blastomere it cannot form a complete organism

• Mosiac embryo

• Schizocoely = splits from solid mesodermal mass

  • mesoderm forms a solid mesodermal band between ectoderm and endoderm

  • split widens over time and creates fluid-filled coelom lined on all sides by mesoderm

Deuterostomes

• Anus = first opening, mouth.= second

• radial cleavage

• Indeterminate = cells remain pluripotent

  • pluripotent stem cells - can differentiate into ANY cell types and retain ability to divide

  • seperated blastomeres CAN each form complete organisms - basis of identifical twins

• regualative embryo

• Enterocoely - pouches from gut wall

  • mesoderm forms outpocketings that pinch off the archenteron (primitive gut wall)

  • mesodermal ouch expand and fuse → become the coelom

  • also lined on all sides by mesoderm

IN THE END BOUTH PRODUCE TRUE EUCOELOMATE

• end result is identical

• Blastomeres = cells produced at the 8-cell stage of cleavage

Molecular Classification of Animals

• compates DNA, RNA and amino acid sequences

• fewer distances = more closely related

  • SSU and rRNA- universal in all organisms

  • evolves slowly
    

Why the 18S ribosomal subunit (SSU rRNA)?

• Universal in ALL organisms

• Changes very slowly — used in molecular clocks

• Highly conserved because disrupting it = organism can't synthesize proteins = death

• Only neutral or beneficial mutations survive over long periods

• more closely related organisms have fewer sequence differences

• GK-PID

  • linking/scaffolding protein related to DNA synthesize enzymes

  • Its critical role: orients the mitotic spindle and keeps cells dividing in the correct plane

  • Without this, cells would divide randomly ("willy nilly") and could not form an organized, structured body

  • Essential for transitioning from single-celled organisms → organized multicellular body

  • Also connected to DNA synthesis genes and enzymes

Hox Genes

• found in all animals

• also called homebox or developmental genes

• control body axis and segment identity during development

  • establish anterior to posterior body axis

  • give rise to limbs and appendages

• gene duplication in Hox cmplex may have driven evolution complex body forms

• Invertebrates- 1 cluster of Hox Genes

• Vertebrates- 4 clusters of Hox genes

Collagen

• Most important structural protein in any animal's body

• Humans have 27 different types of collagen

• Found in: skin, nails, hair, joints, bone coverings, tendons, ligaments, muscles

• Tendons = connect muscle to bone (collagen)

• Ligaments = connect bone to bone (collagen)

• Key in forming bone, cartilage, endoskeletons, and exoskeletons

• A tough, rope-like protein — critical because animals have no cell walls

• Part of the extracellular matrix (ECM) that surrounds all animal cells

Animal Cell Junctions

Anchoring Junction

• holds cells together through intercellular filaments - provides mechanical strength

Tight Junction

• Create impermeable barriers; regulate passage of materials (e.g., blood-brain barrier)

Gap Junctions

• Allow communication between cells; electrical AND chemical signals pass through

Heterotrophy in Animals vs Fungi

How Food is Taken in

• Animals- Swallowed whole or in bites; food taken INSIDE the body first

• Fungi- Food stays outside; digestive enzymes released ONTO food

Where Digestion Happens

• Animals- Inside tissues/gut (intracellular or extracellular in gut cavity)

• Fungi- Outside the body (extracellular)

Metamorphosis

Metamorphosis = a dramatic change in body form across an animal's life cycle

• Example: Frogs — eggs laid in water → tadpoles (aquatic, gills) → tadpoles grow limbs, lose tails, trade gills for lungs → adult frogs (terrestrial)

• Seen in: Molluscs, Arthropods, Annelids, Amphibians, and other vertebrates

• Evolutionary advantage: Larvae and adults occupy different habitats and eat different food → they do NOT compete with each other → allows large numbers of both life stages to coexist

Early Development Stage

• After fertilization, the zygote undergoes repeated mitotic divisions

• Forms a blastula = a hollow ball of cells

• Blastocoel = the fluid-filled inner chamber of the blastula

• Blastomeres = the individual cells on the outside of the blastula

• The blastula → further development → germ layers → organs → full organism

Germ Layer

Germ layers arise during embryonic development and give rise to all tissues, organs, and systems.

Diploblastic (2 layers)

• Found in: Cnidaria

• Ectoderm (outer) + Endoderm/Gastroderm (inner)

• Mesoglea = non-cellular jelly-like layer between them (NOT a true germ layer)

Triploblastic (3 layers)

• Found in: All other animals (Bilateria)

• Ectoderm → skin, nervous system

• Mesoderm → muscles, skeleton, circulatory system, most internal organs

• Endoderm → lining of digestive tract, respiratory tract, many glands

Gastrovascular Cavity Vs True Gut

Gastrovascular Cavity

• 1 mouth which is also the anus

• Both digestion + transport of nutrients throughout body

• No specialization

True Gut

• 2 - mouth + anus

• digestion only

• circulatory system handles transport

• Regional specialization possible

Cleavage, Gastrulation & Early Development

Cleavage

• Cleavage = rapid mitotic divisions after fertilization

• Cells divide so fast they have no time to grow between divisions → cells get progressively smaller

• Zygote → 2 cells → 4 cells → 8 cells → 16 cells → 32 cells → blastula (hollow ball)

The 8-Cell / 32-Cell Stage

• 8-cell stage = key point where protostome vs. deuterostome cleavage pattern becomes visible

• By the 32-cell stage in protostomes, genetic fate of each cell is already determined

Gastrulation — The Most Important Developmental Event

• Gastrulation = cells migrate inward → creates inside vs. outside cell populations → forms the primitive gut

• Creates the archenteron = the primitive gut in the embryo — KNOW THIS TERM

• Creates an opening = the blastopore

• The blastopore's fate distinguishes protostomes from deuterostomes

• establishes gut and seperates germ layers

Phylogenetic Tree

Common Ancestor: Choanoflagellates

Metazoa: true multicelluar animals

• Parazoa

• Placozoa

• Cnidaria

• Ctenophora

• Bilateria

  • Lophotrochozoa

  • Ecdysozoa

Invertebraes Importance

Medical- direct/indirect cause of many human, animal and plant diseases

Ecological- near the base of most food webs in virtually all habitats

Scientific- mode organisms for studying gene expression, cell divsion, aging, embryonic development, fertilization, ect

Applied- source of unique chemicals and commercial products

Environmental Monitoring- indicators of ecosystem health and wellbeing

Sponges (Porifera)

Chanocytes - flagellated collar cells —> beat flagella to derive water current andphagocytose food (strucutally simliar to choanoflagellates)

Archaeocytyes - Amoeba-like stem cells can become ANY other sponge cell type → deliver good, produce sperm, eggs and spicules

Pinacoctyes - Flat cells forming the outer body surface → make up rest of the ostia

• cells are loosley assocaited and NO true tissue

• permantely attached and cannot move (sessile filter feeders)

• all like activity depends on water flow

• no nervous, sensory or locomotor structures (flagella beating not coordinated)

Spicule Chemistry (used to classify sponge groups)

Spongin

• collagen like portein

• flexible bath sponges = dried spongin

Siliceous

• silica

• explored for fiber optic qualities → glass sponges given as wedding gifts

Calcareous

• extracted from seawater

Mesohyl- non-living jelly like matrix between layers

• cells wander through it and contain spicules

Sponge Reproduction

• Asexual: fragmentation (break one = get two) or budding

• Sexual: Archaeocytes → sperm + egg → fertilization in mesohyl → planula larva (free-swimming) → settles → new sponge

• Gemmules: Freshwater sponges only are resistant capsules that can serve freezing winters and regenerate in spring

Sponge 3 Body Types

• Asconoid

  • simplest

  • ostia → flagellated spongocoel → osculum

  • must be small

• Syconoid

  • intermediate

  • Ostia → incurrent canal → flagellated canal → atrium → osculum

  • tubular

• Leuconoid

  • most complex

  • Ostia → incurrent canals → flagellated chambers → excurrent canals → multiple oscula

  • largest colony

Velocity & Water Flow

• Velocity flow is inversely porportional to the cross-sction area of flagellated chambers

• Leuconoid sponges have the smallest chambers —> greatest cross-sectional area —> slowest water flow rate → more time to feed → most successful sponges

• Fast flow means less time to feed so small organism

Cnidaria

Classification:

• Cell Tissue organization

• Radial symmetry

• Diploblastic

• Sac body plan

• Mostly in marine environments some freshwater

• Cnidocyte - specialized CELL (whole stinging unit)

• Cnida - fluid-filled capsule inside the cnidocyte (organelle)

• Nematocyst - coiling stinging threat inside the cnida

  • used only once

  • dead jellyfish on beach can still sting bc nematocyst remain functional after death

• Operculum - the trapdoor/lid keeping the nematocyst coiled inside

• Cnidocil - the trigger/hair on the outside of the cell

Firing Sequences:

Cnidocil is stimulated by touch or chemicals → operculum opens up —> nematocyst fires outward with force (like a bullet- super fast) → pierces the predator/prey → injects toxin

Cnidarian Body Parts

Dimophism- two body forms (polyp + medusa)

• homologous structures

Nerve Net - found at multiple body levels

• no centralized brain

• diffuse nervous system throughout the body

Nutritive Muscular cell - gastrodermis

• moves materials along the gut wall

Mesoglea- jelly part of the jellyfish

• non-living

• between the epidermis and gastrodermis

• NOT a tissue layer

Gastrovascular cavity- single opening (mouth=anus)

• digestion is both extracelluar and intracelluar

GFP (green flourescent protein)

• widely used in biology as celluar dye to highlight genes and cells under UV light

• important tools of molecular biology

Cindarian 2 Body Forms

Polyp:

• Sessil - mouth faces up

• Tubular/cylindrical

• Attached to substrate

• Ex. Coral

Medusa:

• Free-swimming- faces down

• Bell-shaped/umbrella

• Pulses through water

• Ex. Jellyfish

4 Classes of Jellyfish

• Scyphoza “True” Jellyfish

• Cubozoa - Box Jellies

• Hydrozoa

• Anthozoa - “Flower Animals”

Class Scyphozoa

• Dominant life stage is medusa

  • thick mesoglea

• Float in the open ocean

  • some are very large

• Bell/umbrella shaped with tentacles around the rims

  • sub umbrella is the underside of the bell

• Manubrium- hanging stalk mouth structures with oral lobes

• stomach is divded into gastric pouches in the gastrovascular cavity

• Rhopalium- sense organ cluster

  • statocyst: gravity/orientation detection

  • Ocelli: Light-sensitive eye spot

• Locomotion- muscular contractions push water under bell → animal moves up → bobs down (passive bobbing motion)

• Seperate sexes

• Life Cycle:

  • planula larva → Scyphistoma (polyp) → strobilaiton (budding of medusa) → Ephyra (juveline medusa) → adult medusa

Ex. Moon Jelly

Life cycle:

Egg + sperm are released into the water column → fertilize into the diploid zygote → planula larva are ciliated and free swimming → settle onto the solid surface → Scyphostoma (poylp stage) attached to solid surfaces with mouth up and can last up to 2 yrs+ → strobilation (asexual budding) → strobila (stack of juvenile jellies = ephyrae) are all gentically identical clones → ephyrae break off one by one (juvenile medusa) and enter the water column → grow to become adult medusa (male or female with sperm/egg)

• Planula larva = ciliated free-swimming larval stage; looks like a fuzzy football

• Scyphostoma = the polyp stage; sessile; undergoes strobilation

• Strobilation = asexual budding process; stacks of ephyrae bud off the scyphostoma; all are clones

• Ephyra = juvenile medusa; released when strobilation ends; scyphostoma then disappears

• Moon jelly (Aurelia) = local species; polyp stage lasts ~2 years; gonads visible from above — pink = male, white = female

Class Cubozoa

• Box-shaped medusa with tentacle at 4 corners

• medusa stage ONLY

• active and powerful swimmers

  • can hunt prey

  • have true eye lenses for primary prey = fish

  • must kill quickly to subdue fast prey

  • box shape enhances swimming efficiency

• EXTREMELY DANGEROUS- most venomous marine animals

• Toxic

  • Dermonecrotic: destroys skin tissue

  • Cardiotoxic: disrupts heart function

  • Neurotoxic: disrupts nervous system

• Causes Irukandji syndrome

  • very painful

  • can be fatal

  • difficult to see in the water

  • austrialian lifegaurd where full wetsuits to protect against transparent box jellies in water column

• found in warmer watters

Hydrozoa

• in marine and freshwaster

• Colony of polyps that are enclosed by hard chitinous covering (perisac)

• when larvae settle they give rise to branching colonial ind.

  • all genetic clones

• Division of labor among poylp types

  • Gastrozooid: feeding polyp

    • extends beyond perisac covering and has nematocyst bearing tentacles

    • capture food, share food via common gut

  • Gonozooid: Reproductive poylp

    • buds off new poylp asexually and produces medusa stage sexually

  • Dactylozooids: defensive poylp

    • bear powerful nematocysts for defense + prey capture

• all colony members are connected by a common gut

  • feeding polyp captures food and shares it with entire colony

  • tiny medusae bud off gonozooids → release gametes → fertilize → planula larva → settles → new colony (every member is a clone)

Anthozoa

• Polyp ONLY

• Most diverse cnidarian class

• Includes hard and soft corals

• Large gastrovascular cavity that has internal partitions (septa)

• Siphonoglyph: ciliated grooves that drive water into the gastrovascular cavity

  • pumps water in and out

  • when threatened anemone expels water → deflates to small size → looks like a balloon bubble → no tentacles visible

  • when threat passes → siphonglyph pumps water back in → re-inflates → tentacles extend to feed

• Muscles are both circular and longitudinal

  • some movement capability

Anemones Asexual Reproduction:

• whe anemone moves from one location to another it leaves behind pedal disc

  • dense aggregation of clones

  • Division of labor of clone colonies:

    • inner colony- focused on reproduction

    • outer colony- focused on defense

  • colonies actively fight neighboring colonies

• Acontia: potent nematocyst-bearing threads that can be expelled through pores for defense

Coral Types

• Ahermatypic

  • no reef building

  • has CaCO but doesnt build reefs

  • coolor deeper water = habitat

• Hematypic

  • reef buidling

  • secretes calcereous cups to build reef structure

  • warm, shallow clear tropical waters = habitat

• Each coral = a series of tiny polyp clones sitting in calcium carbonate cups (corallites)

• Living tissue covers the entire surface of the calcium carbonate framework

• At night = tentacles extend into water column to feed (mouths visible as "hungry mouths")

• Egg and sperm also released through the same mouth opening

• Coral types: staghorn coral, brain coral, plate coral — each with a different CaCO₃ architecture

Coral-Zoozanthallae Symbiosis

What zooxanthellae provide to coral:

• Photosynthesis (using CO₂ + H₂O + nutrients from coral + sunlight) → produces organic matter (glucose) + O₂

• Provides 20–90% of the coral's total energy needs

• Drives calcification — the laying down of CaCO₃ to build reef structure

• Calcification is faster in light than dark, faster in younger corals; varies by season and temperature

What coral provides to zooxanthellae:

• Protection from herbivores

• Physical home (living within coral tissue)

• Nutrients: nitrogen and phosphorus from coral metabolism

• CO₂ + H₂O from coral respiration

Byproducts managed:

• Coral has protective enzymes to neutralize oxy-radicals, free radicals, and H₂O₂ produced by zooxanthellae metabolism

• Coral feeds at night and relies on zooxanthellae for daytime energy production — a tightly coordinated cycle

Requirements for this symbiosis to work:

• Warm water (corals live near their upper temperature limit)

• Clear water (sunlight must penetrate — only reaches ~100 ft / 30 m depth)

• Normal marine salinity

• Normal temperature

Coral Bleaching

Bleaching mechanism:

1. Perturbation (usually temperature rise) → zooxanthellae become stressed and leave the coral tissue (they can swim — they are flagellated dinoflagellates)

2. Zooxanthellae stay nearby if perturbation is brief → coral can reclaim them and recover

3. If perturbation lasts more than a few days → coral tissue dies without energy supply

4. Living tissue stripped away → only white CaCO₃ skeleton remains = bleached coral

5. Dead reef = white; the CaCO₃ can be implanted into the human body (used in jaw replacements — bone remodels it as if it were natural bone)

6. Over time, the dead CaCO₃ skeleton erodes away entirely

Causes of bleaching:

• Temperature increase (primary driver — even 1–2°C sustained rise)

• Ocean acidification — CO₂ dissolves in water → carbonic acid → lowers pH → dissolves CaCO₃

• Disease sweeping through coral populations

• Sedimentation blocking sunlight/photosynthesis

• Pollutants (including sunscreen — extremely toxic to coral; even small amounts devastating)

• Salinity changes

• Tidal exposure (left dry too long)

• Physical damage (humans walking on reef, boat anchors)

• Predation — Crown of Thorns sea star (Acanthaster planci) motors across reef consuming coral polyps; can reach very high densities and cause massive destruction

Ocean Acidification

Normal Ocean Chemistry (Pre-1850)

• Normal ocean pH = 8.2 (slightly alkaline)

• CO₂ + H₂O → carbonic acid (H₂CO₃) → releases H⁺ ions + bicarbonate ions

• H⁺ ions + carbonates + calcium → calcium carbonate (CaCO₃) → builds shells and reef

• Result: thick shells, healthy corals, healthy ecosystem

Current & Future State

• Current ocean pH ≈ 8.1 — a drop of just 0.1 pH units

• pH is a LOGARITHMIC scale — a 0.1 drop = ~30% increase in hydrogen ions

• "Acidification" does NOT mean the ocean is acid (acid = below pH 7) — it means it is becoming LESS alkaline

• If pH reaches 7.8 → thin shells, dead coral (not there yet but heading in that direction)

How Acidification Damages Coral & Shellfish

1. More CO₂ from human industrial activity → dissolves in ocean → more carbonic acid → more H⁺

2. Extra H⁺ drives formation of bicarbonates instead of carbonates

3. Less carbonate available → organisms can't build CaCO₃ shells/skeletons

4. Existing CaCO₃ (reef, shells) is dissolved by acidified water → like osteoporosis (minerals leached from bone)

5. Dead reef CaCO₃ = porous, degraded, eventually eroded away entirely

Organisms affected beyond coral: Echinoderms, molluscs (clams, oysters), arthropods (crustaceans) — ALL rely on CaCO₃ for shells

Ecological Consequences

• Fewer fish + MORE jellies — jellies are "weedy" species; thrive under changing ocean conditions

• Jellies feed on larval fish → fewer larvae → fisheries collapse

• Ocean acidification + jellyfish blooms = compounding collapse of marine food webs

Ctenphora

• Exclusively marine

• Largest aniaml to move solely by ciliary locomotion

  • only uses beating of cilia

• 8 comb rows (ctenes) of long fused cilia covering the body

• Iridescent Rainbow Shimmer

  • seenin comb jellies

  • light diffraction - scattering of light

  • not bioluminescence

  • fragil, transparent, gelatinous body

Tentacles & Colloblasts

• 2 long retractable tentacles bearing specialized cells called colloblasts

• Colloblasts- unqiue to ctenophores

  • shaped like a harpoon with large sticky end

  • shoot out → stick to prey → tentacle retracts → prey brought to mouth

• No nematocysts

  • consume cnidarians and steal for thier own defense

Feeding & Diet

• Voracious predators- feed on larval fish

• can see one transparent ctenophore glowing inside another that it is consuming

• No natural predators

Nervous System:

• Apical sense organ at the top of body

  • brain strcuture that control coordination and ctene beating + gravity detection

• mouth located at the bottom (opposite end of the apical sense organ)

Gut

• first animal approaching a complete gut

  • mouth at one end and 2 anal pores

  • represent early tube-within-a-tube body plan

Reproduction

• hermaphroditic - all individuals have both male and female orgnas

  • just need to find another ind to spawn

• spawn into water column

• NO HOX GENES

Ctenophores as Ecological Disasters

• Invasive species

• American ctenophore are accidently introduced into the Black Sea

• complete collapse of anchovy fishery - still has not recovered

• millions of fish displaced and consumed by ctenophores

• no natural predators in new environments

Lophotrochozoa

• major protostome clade within bilateria

Lophophore

• crown of ciliated tentacles surrounding the mouth

• used for filter feeding

Trochophore

• free-swimming larva within a band of cilia around the middle

• conical top and bottom

Phylum Plastyheminthes - Flatworms

• No specialized circulatory or respiratory system

  • must exchange nutrients + O2 and CO2 across the body surface

• wider the flatworm the thiner it must be to maintain SA:V ratio for diffusion

• Requires moist/aquatic environment to stay hydrated and allow diffusion

Class Turbeilaria - Free-living flatworms

Body plan (cross-section):

• Gut (incomplete — mouth only, no anus) runs through center

• Parenchyma = solid mass of cells and fibers (mesoderm) fills ALL space between gut and body wall — acoelomate

• Ventral surface = ciliated; beats cilia through a slime track for locomotion

• Two types of locomotion:

  1. Cilia beating through slime track (gives name "Turbellaria" — turbulence they create)

  2. Waves of peristalsis from circular + longitudinal muscles sweeping down the body

Sensory structures:

• Auricles = chemosensory pits on either side of head; detect chemicals → find food / avoid danger

• Ocelli = eyespots (photoreceptors); detect light and dark only — NOT image formation

• Positively chemotactic = drawn toward food chemicals

• Negatively phototactic = move AWAY from light (avoid overheating)

Nervous system:

• Ladder-type nervous system = distinct anterior brain connected to two lateral nerve cords running the length of body; transverse fibers connect them like ladder rungs

Excretory system:

• Flame cells = first excretory cells in animal evolution

• Cilia flicker/beat → draw fluid under negative pressure into canals → exits through pores

• Function: eliminate nitrogenous waste AND maintain osmotic balance

Reproduction:

• Asexual: Regeneration — only need 1/32 of the body to regenerate a whole animal

  • Cut head off → grows back; cut tail off → grows back; cut both → both grow back

  • Notch cut in anterior end → grows two heads

  • Important model organism for regeneration research (though axolotls now more common)

• Sexual: Hermaphroditic; both male AND female organs present in one individual

  • Usually NOT self-fertile (prevents inbreeding)

  • Penis fencing = two planarians fight with penis, trying to stab the other; the one who gets stabbed has to carry the eggs (greater energy investment = disadvantage)

  • Sperm production occurs before egg production (sequential hermaphroditism)

Class Trematoda - Flukes

Adaptation for Parisitism

• Penetration glands - helps larvae into host tissue

• Cyst-forming ability - survive outside the host

• Suckers and hooks- adhesion organs for attachement inide the host

• Huge reproductive capacity- needed because getting from host to host is difficult

• Usually hermaphroditic

Schistosomiasis- Life Cycle

• seperate males and females

• males are shorter and fatter

  • gynecological canal running down body

• female lives inside the males canal

  • cannot devleop or reproduce without pairing

• male does most of the feeding (blood + tissue from blood vessels of human gut/bladder)

• adults will live in human blood vessels for to 20 years and reproduce

adult worms in human blood vessles (gut/bladder) → lay thier eggs → eggs exist in feces or urine and contaminate local water → miracidium larva (cilitated) immediately penetrates the snail (intermediate host) → sporocyst (lose cilia with asexual cloning inside snail → mass reproduction) → burst out snail → penetrate human skin → migrate to blood vessles and mature to adult worms

• 2/3 of eggs get trapped in host tisue

• trapped eggs cause chronic inflammation, liver damage, bladder cancer, GI tract damage and reproductive harm

• damns and tilapia farming → more nail habitats → more transmission

Class Cestoda - Tapeworms

• ulitmate paratsites → give up enitre digestive system to maximize reproduction

  • no gut - absorb nutrients directly through tegument (body surface) from host intestine

  • one tapeworm per host

Body Structure:

• Scolex = attachment head; has hooks AND/OR suckers; embeds in intestinal wall

• Proglottids = repeating body segments; each = a reproductive factory with hundreds of testes + hundreds of ovaries = potentially millions of eggs

• Self-fertilization is routine (don't need another tapeworm) AND cross-fertilization between segments is possible

Beef/Pork Tapeworms Life Cycle:

gravid proglottids breaks off → egg pass human feces → contaminate grass/soil → oncospere larva (from egg) ingested by cow or pig → penetrates gut wall → travels to muscle → Cysticercus (bladder worm cyst) forms in muscle = measly pork/beef → human eats undercooked/raw meat → cysticercus excysts in intestine → grows into adult tapeworm

Beef tapeworm (Taenia saginata):

• Causes taeniasis — mild GI symptoms (vomiting, diarrhea, weight loss) or often none at all

• Relatively harmless

Pork tapeworm (Taenia solium) — FAR more dangerous:

• The EGGS (not the worm itself) are the problem

• If eggs enter the human body (from contaminated food/water, or from an infected household member not washing hands) → eggs treat humans like pigs → cysticerci form in human muscle, joints, eyes, and BRAIN

• In the brain = neurocysticercosis

• Symptoms: sudden-onset epilepsy, severe neurological symptoms, death in serious cases

Rotifera

• free living in freshwater and marine environments

• pseudocoelomate (false body cavity)

• Ecologically = fish food, imporntant plankton component, used in pollution monitoring

Anatomy

• Corona = crown of cilia at anterior end; looks like a rotating wheel

  • Role 1: Locomotion — beats cilia to move through water

  • Role 2: Feeding — sweeps food (bacteria, algae) toward mouth

• Mastax = muscular pharynx (throat)

• Trophi = chitinous jaws INSIDE the mastax; species-specific shape used for identification; grind food

• Complete digestive tract (mouth → gastric glands → salivary glands → stomach → intestine → anus)

• Telescoping foot with toes → used for attachment to substrates (grass blades, other organisms)

Cryptobiosis — Suspended Animation

• Rotifers can lose ~90% of their water and enter a state of suspended animation (cryptobiosis)

• Remain dormant for long periods; revive when water is added

• Similar principle to sea monkeys (actually a type of shrimp/brine shrimp in arthropods)

Parthenogenesis

Amictic Cycle (Asexual — "A cycle") — default mode:

• Adult females produce diploid amictic eggs via MITOSIS (no fertilization needed)

• All hatch into adult females → all clones

• Purpose: Rapid population growth to exploit favorable conditions (spring/summer)

Mictic Cycle (Sexual) — triggered by environmental stress:

• Triggers: decrease in food supply, shorter photoperiod, lower temperatures (= approaching winter)

• Adult females switch to producing haploid mictic eggs via MEIOSIS

• If unfertilized: haploid egg matures in hours into a haploid male (just a bag of testes; cannot feed; short-lived; only function = produce sperm via meiosis)

• If fertilized: haploid egg + haploid sperm → diploid resting egg (winter egg)

• Resting eggs survive winter freezing; hatch into adult females in spring → amictic cycle restarts

Advantages of parthenogensis:

• grows population extremely rapidly (every individual can reproduce)

• takes advantage of good conditions fast

Disadvantages:

• all offspring are clones → no genetic variation → population is vulnerable if conditions change

Annelida

Chaetae vs Satae

Chatae- chtinous bristle-like hairs projecting from the body

• aid in movement and anchoring

• polychaetas- MANY chaetae per body segment

• Oligochaetes- few chaetae per body segment

• Leeches will have no chaetae at all

Satae- sensory hairs projecting THROUGH the exoskeleton

• allows arthropods to feel

Closed Ciruclation

• blood allows inside vessles

• small fluid volume

• high pressure

• more efficient

• have capillaries connected to arteries

Double Transport System

• circulatory and coelomic fluid BOTH carry nutrients, gases, and wastes

• some annelids have respiratory pigment in their blood to enhance O2 transport

• Five pairs of aortic arches in earthworms - the “heart's” pumping the blood

• Dorsal blood vessel + ventral blood vessel run the length of the body

Nervous System: Ventral Solid Nerve Cord

• Upgrade from the ladder-type of flatworms → now a ventral SOLID nerve cord

• Giant axons = very large diameter neurons that allow extremely rapid nerve impulse conduction

  • The bigger the axon diameter, the faster the impulse travels

  • Giant axons = rapid escape responses

  • Axons in annelids are NOT myelinated (myelination comes with vertebrates)

• Leeches produce serotonin — similar to human neurotransmitters → valuable for neuroscience research

Polychaetes

Body Segments:

• Prostomium = very first anterior tip

  • overhangd the mouth

  • specialized senory functions

• Peristomium = second segment

  • bears the mouth, may have jaws

• Parapodia

  • fleshy lateral extensions of the body wall (extensions of the coelom)

  • paired on each segement

  • Functions: locomotion (swimming, crawling), gas exchange, waste removal

  • Some modified into gills for enhanced gas exchange

Why segmentation + hydrostatic skeleton works:

• Each segment's coelom is separately sealed by septa → independently pressurized

• Circular + longitudinal muscles in EACH segment act as antagonistic pairs

  • Circular muscle contracts → segment elongates (lengthens and narrows)

  • Longitudinal muscle contracts → segment shortens (shortens and widens)

• Each segment can move independently from others → conserves energy; allows head end to probe while tail end anchors

• Peristalsis = waves of alternating circular and longitudinal muscle contractions sweeping down the body → same mechanism that moves food down YOUR esophagus to stomach and through intestines

Diversity

• mosr succesful annelid body form → greatest diversity, more adaptable

• Errant polychaetes are mobile predators

  • firworm chaetae have toxins → burning sensation if touched

  • clam worms have chitinous jaws and WILL bite humans

• Sedentary polychaetes are stationary

• Pogonophora (beard worms)

  • live in hydrothermal vents

  • brigh red from hemoglobin

  • trophozone packed with chemosynthetic bacteria

Trochophore Larva

• free-swimming, top-shaped bands of cilia with complete digestive systems

• gets heavier as more segments are added → settles out of water column → metamorphosis → adult

Oligochaetes

Internal anatomy (earthworm cross-section):

• Typhlosole = internal dorsal fold projecting into the intestine lumen → increases absorption surface area

• Crop = specialized segment for food storage

• Gizzard = specialized segment for mechanical grinding of food

• Dorsal + ventral blood vessels running the length of the body

• 5 pairs of aortic arches = the "hearts"

• Nephridia = true kidney-like organs repeated in each segment; filter coelomic fluid

• Ventral nerve cord sending fibers to each segment

• Septa visible internally; annuli (rings) mark segments externally

• The entire coelom is the fluid-filled space outside the gut — fluid pressure = hydrostatic skeleton

Challenges of terrestrial reproduction:

• Cannot release gametes into water (drying = gamete death)

• No ocean to support free-swimming larvae

• Solution: clitellum handles ALL reproductive challenges

Clitellum — Three Functions:

1. Secretes mucus → protects sperm from desiccation during transfer between mating worms

2. Secretes the cocoon → tough protective case; worm crawls through it depositing eggs + sperm inside → fertilization occurs within cocoon

3. Secretes albumin into the cocoon → feeds the developing young

Mating process:

• Two worms align in opposite directions (head of one next to tail of other)

• Each worm's clitellum is opposite the other worm's anterior end

• Worm crawls completely THROUGH the cocoon → cocoon seals up → sits in soil → hatches as tiny juvenile earthworms (direct development — no larvae)

Clitellata group:

• Oligochaetes keep clitellum permanently

• Leeches have clitellum only seasonally (only during active reproduction)

Leeches

• Usually in freshwater some in moist terrestrial areas and some in marines

• no chaetae

• dorsally flattned body with muscular body wall

• no peristalsis

  • move by looping locomotion

  • anterior sucker grips → posterior releases → body loops up → poster grips → anterior releases and extends

Feeding

• Tri-irradiate jaw = 3 cutting plates arranged like a peace sign/Mercedes-Benz symbol; hundreds of tiny teeth; leaves distinctive 3-pronged wound

• Anesthetic in saliva → host doesn't feel the bite

• Hirudin = powerful anticoagulant → keeps blood flowing into leech gut

• Can expand to twice their body size when engorged with blood

• No digestive enzymes of their own → rely entirely on symbiotic bacteria in gut to slowly digest the blood meal

• Specialized kidneys remove ~40% of the water from ingested blood → concentrate the protein/cells

• Highly folded gut → can expand dramatically for storage

• Feed only once per year (or every 18 months) — takes that long to digest one blood meal

• Find mammalian prey by sensing body temperature

Leeches Medical Use

• Used medicinally since middle ages

• can get prescription today for leeches

• leech wound bleeds for 10 hours after removal

Reattachment Surgery

• severed finger or toe can be sewn back but veins cannot be or capillaries

• leeches remove pooled blood so tissue can get oxygen until veins regrow

Plastic Surgery

• remove coagulated/bruised blood from delicate facial tissue to promote healing

Leech Nervous System

• simple and large

• easy to record them

• great model for neuroscience research

• Leeches produce serotonin → help to understand the function of the neurotransmitter

Phylum Mollusca

• hard shells that fossilize well which means that have an excellent fossil record

• tremendous diversity bc they are flexible and adaptable

• second largest invertebrate group

Radula - Feeding Structure

• Radula - chitinous ribbon studded with teeth → rotates out over a cartilaginous support called the odontophore

• Teeth scrape food off surfaces; as teeth wear down, new ones are produced continuously

• Teeth form varies by species → highly diagnostic for identification

• Some species have radula teeth impregnated with iron for scraping hard rock surfaces (e.g., chitons)

• Absent in bivalves (they filter-feed instead)

Open Circulatory System

• Heart pumps hemolymph (blood) through vessels → into open hemocoel (body spaces)

• Blood bathes organs directly; not confined to vessels

• Exception: Cephalopods (squid, octopus) have CLOSED circulation

• Reduced coelom — limited to area around the heart and gonads

Counter Current Exchange

• Molluscs = first animals we see with true respiratory gills

• Gills operate on counter-current exchange:

  • Blood flows through gills in one direction

  • Water flows over gill surface in the opposite direction

  • Result: blood always encounters water with MORE oxygen than itself → maintains maximum O₂ concentration gradient at all times → highly efficient O₂ extraction

The Mantle

• Mantle = a unique tissue layer found only in molluscs

• Three functions:

  1. Secretes the shell (if present)

  2. Forms the mantle cavity — a chamber housing the gills (aquatic molluscs) or lung (terrestrial pulmonates)

  3. Lines the shell internally

Larval Development

• Trochophore larva

• veligar larva = second larval stage

  • small shell beginning to form

  • ciliated lobes for swimming → gets heavier → settles → metamorphoses into adult

Mollusca - Shell Strcutre

Shell Evolution

• hells evolved as protective devices against predation — one of the driving forces behind the Cambrian Explosion (arms race between predator and prey)

• Also protect against desiccation (drying out) — critical for intertidal and terrestrial gastropods

• Shells are calcium carbonate extracted from the water column; secreted by the mantle epithelium

• Shell grows with the animal's body over time → you can age a clam by cross-sectioning the shell and counting growth rings (like tree rings; laid down seasonally)

Shell Layers

Periostracum

• outermost, thin, sometimes brownish anfd flaky

• protects inner CaCo3 from erosion

• gradually worn away

prismatic Layer

• bulk of the shell

• chalky

• densely packed vertical prisms

Nacreous Layer

• innermost later

• direct contact with body

• grows thicker overtime

• mother of pearl

Pearls:

• foreign body irritates the mantle

• mantle walls it off with layer upon layer of nacre

• forms a pearl

• more uniform + bigger which makes it more valbule

Ocean Acidication effects on shells

• Rising CO2 → less carbonate available → shells getting progressively thinner over time → threats to all shell-building organisms

H.A.M

Hypothetical Ancestral Mollusc

• theoretical generalized creature used in biology to illustrate shared features of modern Molluscs

Bivalva Mollusc

Adductor Muscles

• powerful muscle that close the two shell valves

• can keep shell closed for days without expending energy

• what you eat in scallop

• scallops- one of the few bivalves that can swim by clapping valves

  • row of blue eyes along shell margin that detects movement

• No head and no radula

  • filter feeders

  • cilia on the gills beat to draw water in through incurrent siphon → food trapped in gills → water exists through excurrent siphon

    • siphons are passive channels

• gills are both feeding organs and respiratory organs

• byssus threads = protein fibers secreted by the foot

  • solidify on contact with water → anchor mussels to rocks in intertidal zones

• Red tide danger

  • bivalves concentrate toxins from toxic algal bloom in their tissues

  • unaffected themselves

  • dangerous to mammals and humans who can eat them

Gastropoda

Radula

• Herbivores — scrape algae off rocks

• Carnivores with harpoon radula — cone snails inject venom through a single-use radula tooth (never reloaded; replaced after one use)

• Carnivores with boring radula — have a proboscis that secretes digestive enzymes AND makes a perfectly round hole through another bivalve's shell

  • if you find a shell with a round hole, it was eaten by a predatory gastropod

• Omnivores/scavengers — eat essentially anything including each other

Operculum = a plate on the muscular foot that seals the shell opening when the animal retracts fully inside

• Animal connects to shell apex by a single muscle (columellar muscle)

• Shell chambers get progressively larger toward the body chamber

• Operculum = the "trapdoor" that closes off the shell

Shell Chirality

• most shells are coil right-handed

• some are coil left-handed and is genetically determined

• shells have holes at the apex to let waste products exit

Terrestrial Gastropods

• mantle fucntions as a lung

• lay eggs with direct development on land (cannot use water to support larvae)

Nudibranches

• no shell as adult

• steal nematocysts from hydrozoans

  • incorporate cnidocytes into their own dorsal projections for defense

  • other animals get stung when they touch them

  • brightly colored

Cephalopoda

Evolutionary History

• used to be top ocean predator during paleozoic era

• replaced by fishes

• most complex invertebrates

Locomotion- Jet Propulsion

• water drawn into mantle cavity

• edges of mantle seal down

• water forcefully ejected through siphon

• direction siphon points = direction of travel

• more force out means faster movement

  • fast in general

• gill flow is direct and branchial hearts push blood through gills

  • counter-current exchange is most efficient

  • active predators need very rapid O2 delivery

  • accessory branchial hearts sit on top of each gill → pumps blood directly through gills at high speed → supports fast + active life

• Direct development - larval stages happening inside eff and hatchinlings look like tiny adults

Ink Sac

• All cephalopods EXCEPT Nautilus have an ink sac

• Ink = dark melanin-based fluid, discharged through the anus

• Forms a smokescreen in water; has narcotic qualities that stun predators/prey

• Very dark, very sticky — "don't break the ink sac during dissection"

Spermatophore + hectocotylus

• Male packages sperm into a spermatophore

• Transfers it to female using modified arm = hectocotylus

• Sometimes the hectocotylus breaks off inside the female

Modern Cephlapod Groups

• Nautilus

• Cuttlefish

• Squid

• Octopus

Phylum Nematoda- Roundworms

Ecdysozoa

• The second major Protostomia clade (separate from Lophotrochozoa)

• Defined by ecdysis = molting of the cuticle

• Two major phyla: Nematoda (roundworms) + Arthropoda (insects, crustaceans, etc.)

• Separated from Lophotrochozoa by both molecular AND morphological evidence

• Ecdysozoan sperm = crawls like an amoeba (NO flagellum) → internal fertilization required; sperm cannot swim

• Adapted to dry environments more than any other invertebrate group — cuticle provides desiccation protection

VERY ABUNDANT

Ecological Roles

• free-living or saprophytes (feed on decomposing organic matter)

• critical for breaking down dead organic matter and cycling nutrients back to higher trophic levels

• help keep fungal and bacterial pops. in check

Nematoda Body Plans

• slender, cylindrical, elongated & tapered at both ends

• maintain round shape in cross-section due to very high internal presure

• non-segmented

• generally colorless

Body Cavity

• pseudocoelomate or acoelomate

• single internal cavity running the entire body length

• fluid under very high pressure = hydrostatic skeleton

Eutely

• species specific fixed number of cells

• once the cell number is reached the cells lose the ability to divide

• consequences: cannot regenerate well if they get injured

Nervous Systems

• brain encircles the pharynx

• dorsal and ventral nerve cords running the length of the body

• muscles brank to connect to the nervous system

Locomotion

• only longitudinal muscle

• thrashing and whipping sinusodal locomotion

• working against rigid cuticle → provides resistance to push again

• need something to push off on → found in soil inside host bodies

• worm thrashing side. toside is a nematod

cuticle

• tough outer protective layer

• shed 4 times during development

Nematods- Parasites of humans

Giant Roundworm

• large parasite found in human intestine

• consequence severite depends on worm buden, species, and host nutritional status

Hookworm

• found in southeastern United States

• high infection rates due to poor sanitation

Body Strcuture

• mouth has hooks/teeth or cutting plates

• male has a hook at posterior end for identifiation

• female is larger

• copulatory spicules on male for sperm transfer

How you get infected

1. infected person feces contaminate soil (poor sanitation - no septic system)

2. eggs hatch in soil → larvae shed (L3 stage - infective)

3. L3 larvae crawl up blades of grass

4. Enter human body by penetrating bare skin

Symptoms:

• iron deficiency

• abdominal pain

• loss of appetite

• more severe in children and pregnant women

Hookworm Life Cycle:

infected persons feces contaminate the soil → eggs mature in spoil (L1 larvae) → molt and become L3 “filaiform larvae” → crawl up grass blades and wait for host

Cutaneous Phase

larvae penetrate bare skin (even tough skin) → enter blood stream → travel to heart

Pulmonary Phase

heart → pulmonary circulation → lungs (blood vessels) → larvae molt through L1 to L4 (maturation) → L4 larvae cross into air sacs and crawl up bronchioles to bronchi to Trachea —> irritate trachea making you cough and swallow them

Intestinal Phase

pass through stomach and resist gastric juice → attach to small intestinal lining → hook onto lining with hooks/cutting plates → feed on blood and tissue (1-2 days) → release and move to new spot (each wound bleeds for 10 days after worm has move on) → massive continue blood loss

Guinea Worm

• drining contaminated water containing copepods infected with guinea worm larvae (microscopic cannot be seen or felt)

Life cycle

female worm matures in human tissue (along with bones for a year) → creates a blister on skin surface → blister causes intense burning sensation → person submerges in water to cool it → worm detects water and releases thousans of live larvae into water → larvae infect copepods in water → human drink copepod-infected water and cycle continues

• no treatment

• capture the worms head as it emerges from blister

• takes minimum 2 weeks to remove

• if worm breaks can cause anaphylatic shock

Elphantiasis

• caused by filarial worms

• transmitted by mosquitos

• live in lymphatic vessels → block lymph fluid flow

• fluid accumalates in tissue space → limbs swell

• stretching of skin → breakdown → susceptibility to fungal and bacterial infections

• worm infection can be cured but the limb cannot be restored once swollen to this state

Pinworm

• most common worm parasite in the US

• female lives in the large intestine

• at night travel to anal opening to lay eggs → causes itching → person scratches → eggs under fingernails → if hands not washes can spread eggs and cause reinfection

River Blindness

• larval worms crawl across the surface of the eye → cumulative damage → blindess

Heartworms

• transmitted by mosquitos to dogs

• worms reproduce and fill blood vessels of the heart

• silent killers- dog may show only coughing, exhaustion, fainting and weight loss

• death from heart failure as blood vessels become completely blocked

Phylum Arthropoda

• largest group of living animals

  • most abundant, diverse and widespread

• found in every major biome

• only invertebrates capable of flight

  • first to colonize land

• “the age of insects”

• both arthropoda and nematoda are ecdyszoa

  • shedding of cuticle

  • ameboid sperm → crawls and internal fertilization required (sperm cannot swim)

Arthropoda Key Characteristics

Jointed Appendages

• freely moveable, give tremendous flexibility including flight

Exoskeleton of chitin

• ridgid, protective

• prevents dessication

• does NOT grow with the body → must shed

Segmented body

• segments fused into function unit - TAGMATA

Striated Muscle

• works faster, more forceful and under nervous system control

Open Circulatory system

• hemocoel- large open body cavity → heart pumps hemolymph through vessels into hemocoel where it bathes organs directly

• hemocyanin- copper-based respiratory pigment (blue when oxygenated)

Seperate Sexes

Developed NS

• sophisticated brain

• compound eyes

• complex sensory systems

Tagmata

• Arthropod segments are fused into larger functional units called tagmata:

• Head - sensory reception + feeding

• Thorax - Locomotion (legs + wings)

• Abdomen - Houses internal organs → associated with reproduction

Exoskeloten

• Epicuticle (outermost)

• Exocuticle

• Endocuticle

• Epidermis (innermost living layer)

• protection from predators + physical damage

• prevents dessication

• acts as exoskeleton for muscle attachment and support

Satae

• sensory hairs

• project through layers of exoskeleton

• connection to the nervous system

Chitin Composition

• Crustaceans: chitin + calcium salts → very hard (shells, claws)

• Insects: chitin + tanned proteins → lighter but tough

• Both nitrogen-containing polysaccharide base

Molting -Ecdysis

• exoskeleton does not grow with the animal - > must shed periodically to allow growth (ecdysis)

Pre-molt

• old cuticles start to thin → enzymes break it down from below

• epidermis begins cell division simultaneously

• New cuticle forms underneath the old one (highly folded — too big for current body)

• Animal is NEVER left without SOME degree of exoskeleton

Molt Point

• Old cuticle ruptures (usually at dorsal surface of thorax/carapace)

• Animal backs out of old cuticle

• Takes in air (terrestrial) or water (aquatic) → expands new cuticle to slightly larger size

• Animal is vulnerable during this period → males often guard females during molting to protect them AND for reproduction (often the only time mating can occur)

Post-molt

• New cuticle thickens

• Proteins become tanned (hardened)

• Calcium salts deposited (crustaceans)

• Animal grows INTO the new cuticle over time

• controlled by hormones

Arthropods Muscles

Have both smooth and striated muscle

Striated

• same as your skeletal muscle

• works faster and produces more forceful contractions

• under VNS

• arranged in antagonistic pairs across joints

  • flexor muscle contracts → joints flex (bend)

  • extensor muscle contracts → joints extend (straightens)

Athropoda Respiratory Systems

Aquatic- gills (similar to molluscs)

• blood and water flow

Terrestrial

• archnids - book lungs

  • functions similarly to tracheal system

• insects

  • tracheal system

  • network of tubes with openings via spiracles leading to air sacs and allwoing passive air flow

Tracheal System

• Spiracles = small openings on body surface → lead into trachea (tubes)

• Trachea branch into smaller tracheoles → lead to air sacs

• O₂ diffuses from air sacs to cells; CO₂ diffuses from cells to air sacs

• Every cell must be in close proximity to an air sac

• No pumping device — air flows passively

• Size limitation: tracheal system limits how large terrestrial arthropods can be (every cell must be near a tube)

Arthropods Excretory Systems

Aquatic

• green glands- located in the head

• concentrate environmental contaminants

Terrestrial

• Malpighian tubules- produce semi-solid uric acid waste mize with digestive system waste

Malpighian tubules:

• Terrestrial arthropods produce uric acid (like birds and reptiles)

• Uric acid = semi-solid waste → maximum water conservation

• Critical adaptation for life on land

• Same reasoning as bird droppings being semi-solid

Green glands in lobsters:

• Concentrate pollutants from surrounding water

• Why lobsters from dirty water (even Boston Harbor at its dirtiest) still had safe edible meat — the contaminants end up in the green gland, not the muscle

Class Crustacea

• Primarily aquatic; mostly marine

• Some freshwater (crayfish, water fleas, copepods)

• Very few terrestrial (pill bugs = most notable exception)

• Enormous ecosystem and economic importance

• Includes: shrimp, lobster, crab, crayfish, barnacles, copepods, krill, Daphnia, pill bugs

Defining Features:

• Biramous appendages = two branches per appendage (bi = two, ramus = branch)

  • Each appendage has an upper branch + lower branch attached to body

  • Contrast with uniramous appendages (insects) = ONE branch only

• 5 pairs of walking legs on the thorax

• Two pairs of antennae (long pair = antennae; short pair = antennules) — sensory

• One pair of compound eyes (may be on stalks for mobility)

• Cephalothorax = head + thorax fused into one region

• Carapace = hard dorsal shield covering the cephalothorax (non-segmented)

Lobster Example:

• Chelipads- first pair of walking legs modified into large pincer claws for defense + feedings

• Walking legs- 4 remaining pairs behind chelipads

  • Swimmerets- appendeges on abdominal segments

  • first pair in male modified for clasping female

  • female used to hold eggs

• Uropods- broad, flap-like tail appendages

• Telson- central tail piece

• Escape response- tail flip pushes water under tail -? shoots animal backward rapidly

• Carapace notch- is lobster is too small, notch the carapace and release it

  • notch tells other fisherman it has been measuresd

Lobster Internal Anatomy

• Ventral Solid Nerve Code- well-developed brain anteriorly

• Linear GI tract

• Heart with ostia- open circulation

• Gills ventilated as animal walks

Lobster Diet

• Scavengers that will be anything

• rubber bands on claws are to prevent them from eating others in captivity

Other Crustaceans

• Krill = feeds whales; critical marine food web link

• Copepods = intermediate hosts in guinea worm life cycle; part of marine zooplankton

• Daphnia (water flea) = freshwater; used in lab studies

• Barnacles = cement their heads to substrate; extend feathery jointed legs into water for filter feeding

• Pill bugs = only truly terrestrial crustaceans; roll up like armadillo when threatened

Class Chelicerata

• mostly terrestrial

• includes spiders, scorpions, ticks, mites, horseshoe crabs, sea spiders

Defining Features

• NO antennae (key difference from crustaceans — no appendages on head)

• All appendages attach to cephalothorax (head + thorax fused)

• Chelicerae = first pair of appendages; feeding devices; modified into fangs in spiders

• Pedipalps = second pair of appendages; modified in horseshoe crabs for male to grip female during reproduction; may have sensory or reproductive roles

• 4 pairs of walking legs = 8 legs total → identifies spiders, scorpions, ticks, mites

• Abdomen hangs off the back (contains most internal organs + silk glands in spiders)

Respiratory Systems

• terrestrial chelicerates: book lungs working similarly to tracheal system

Ticks

Black-legged tick - vector for lyme disease

• common in the US

Lone Star tick

• will actively hunt down host

• bite can cause alpha-gal allergy

  • allergy to red meat that is permanent

• Alpha-gal = carbohydrate found in mammalian meat

  • all red meat becomes toxic

Horseshoe Crab

• horseshoe-shaped carapace (non-segmented)

• long tail-like telson

• book gills under abdomen

• compound eyes + simple eyes

• pinhile camera-like eye → contributed to understanding vertebrate vision

Ecological Importance:

• adults migrate into shallow water in late spring to breed

• female lays eggs on beach → critical food source for migrating shorebirds

Medical Importance

• LAL = Limulus Ambeocyte Lysate test

• Amebocyte clot instantly in the presence of bacterial endotoxins

  • Bright blue blood

• Horseshoe cravs like in bacteria-rich ocean with open circulation → bacteria spread everything

  • clotting walls off bacteria locally

• Clotting reaction turned into test

  • freeze-dried blood cells + medical device/pharmaceutical → if it clots there are endotoxins present

Spiders

spider silk

• Stronger than steel by weight

• More elastic than Kevlar

• Up to 7 different silk glands in one spider; each produces a different type of silk (web construction, egg cases, wrapping prey, dragline)

• Silk solidifies on contact with outside air

• Web-building is genetically inherited — spiders spin correct webs on their first attempt

• Drugged spiders (caffeine, LSD) spin incorrect/disorganized webs — used to study nervous system effects

spider venom

• neurotoxic

  • acts on the nervous system

  • disrupts nerve impulse

• hemolytics

  • acts on blood cells

  • ruptures red blood cells

Black Widow

• Largest spider in the USA

• female eats male after coupulatoin

• red hourglass on abdomen

• leading cuase of death by spider bites

• not agressive → bites defensively

• Venom mechanism: promotes release of acetylcholine → intense muscle cramps + respiratory distress

Sydney Funnel Web Spider

• Australian

• hunts you down

• very large with long fangs

• Venom: open sodium channels → prevents nerve impulse conduction

Brazilian Wandering Spider

• Venom: produces serotonin + multiple ion channel deficits

Brown Recluse

• white violin shape on abdomen

• hemolytic venom:

  • red wound at bite site

  • toxin spreads → capillary beds disrupted → RBC rupture

  • Bullseye pattern - bite wound in center surrounded by spreading red ring

  • Tissue death (necrosis) in affected areas

Spiders can regulate venom injection

• bigger prey = more venom spent

• smaller prey = less venom used

Subphylum Uniramia

Uniramia = appendages with only ONE branch

• crustaceans are biramous

• two major groups

  • hexapoda (6 legs)

  • myriapoda (centipedes - many legs)

Myriapoda- Cenipedes and Millipedes

Centipedes

• dorsoventrally flattened

• one pair of legs per body segment

  • legs project out to the side

• have poison glands

  • inject toxins when they bite on prey

• prey: insects, worms, anything that moves close to them

• habitat: basement, drains, dark/damp areas

Millipedes

• body is rounded

• two pairs of legs per body segment

  • legs pushed downward

• slow-moving deposit feeders

  • feed on decaying matter on forest floor

• no toxins

  • defense is to curl up in a ball

• sometimes kept as pets

Hexapoda

• 3 pairs of legs

• 0-2 wings

• 1 pair of antennae

• 1 pair of mandibles

• compound eyes

• tympanum = hearing organ allowing detection of sound waves

• Tracheal system for respiration

  • malpighan tubules for excretion

• ventral solid nerve cord + well developed brain

Malpighian tubules — key adaptation for life on land:

• Located at junction of midgut and hindgut

• Produce uric acid as nitrogenous waste (semi-solid)

• Uric acid combined with digestive waste → exits together

• Allows maximum water conservation

• Also reduces weight → important for flight

Inset Metamorphosis

1. Ametabolous

• no metamorphosis

• what hatches from eggs = tiny version of the adult

  • gets bigger with each shed

• wingless insects

• silverfish: eat paper, fabric, cereal, photographs, glue, wallpaper

  • report to librarians if seen

  • very destructive in abandoned buildings

2. Hemimetabolous

• incomplete/gradual metamorphosis

• “hald metamorphosis”

• what hatches = nymph that resembes adults but smaller and different coloration

  • no wings

• Wings develop externally from wing buds as animal sheds through successive nymph

• reproductive organs grow internally across nymph

• Ex. dragonflies, grasshoppers, cockroaches

  • many have aqutic nymph stages + terrestrial adult stage

3. Holometabolous

• complete metamorphosis

• Four stages = egg → larva → pupa → adult

• larva and adult are dramatically different from one another

  • different mouth parts

  • different locomotion

  • different food resoruces

  • no competition between larva and adult

• huge numbers able to coexist with each other

Life stage detail:

• egg - laid in water on land

• larva - worm-like and walks on legs

  • chewing mouthpart

  • actively growing and feeding

  • cannot fly

• pupa (chrysalis)

  • encased in cacoon

  • non-feeding

  • intense body reorganization over winters

  • imaginal discs groups of cells within pupa activated to build adult structure while larval structure broken down

• adult - flying

  • new mouthparts

  • short-lived

  • primary function = reproduction that dies

Adult mouthpart examples:

• Butterflies/moths: long siphoning tube (proboscis) for nectar from deep floral tubes

• Female mosquitoes: piercing mouthparts to draw blood meal (needed for egg production); males feed on nectar

• Grasshoppers: chewing mouthparts for plant material

Why holometabolous is so successful:

• Larvae exploit one environment/food source

• Adults exploit a completely different environment/food source

• No intraspecific competition between life stages

• Allows enormous populations of both

Deuterostomia

• Blastopore → becomes the ANUS (mouth forms from second opening)

• Radial cleavage (90° cell divisions; uniform cell size)

• Indeterminate cleavage → regulative embryo (cells remain pluripotent → basis of identical twins)

• Enterocoely = coelom forms as outpocketings from archenteron (gut wall)

• All are eucoelomate (true body cavity)

Two major deuterostome groups:

1. Echinodermata — sea stars, urchins, cucumbers, sea lilies

2. Chordata — cephalochordates + urochordates + vertebrates

Phylum Echinodermata

• Exclusively marina

Key Characteristics:

1. Pentamerous Radial Symmetry (as adults)

• 5-part symmetry or multiples of 5 (10, 15, 20 arms/rows)

• SECONDARY radial symmetry — larvae are bilaterally symmetrical

• At metamorphosis, larva cements itself down → converts to radial symmetry as adult

• Radial symmetry → sensory structures scattered throughout body (no head)

2. Endoskeleton

• Internal calcium-rich ossicle plates with spines projecting outward

• First endoskeleton seen in invertebrates

• Ossicles articulate (have joints); some more movable than others

3. Mutable Connective Tissue

• Unique to echinoderms; controlled by calcium signaling

• Can switch from soft/pliable → rigid/firm in seconds

• Enables autotomy: drop a limb to escape predators (wall it off instantly)

• Sea stars/brittle stars drop arms; brittle stars have NO organs in arms (expendable)

• Being studied to understand arthritis and cartilage diseases

4. No Cephalization

• No head — consequence of radial symmetry

• Nervous system = central nerve ring with radiating branches

5. Extensive Coelom — Water Vascular System

• All physiology depends on this unique system (see below)

6. Regeneration

• Sea stars: need only 1/5 of central disk + 1 arm to regenerate complete animal

  • Regenerating piece = comet (one arm + disk fragment)

  • Never cut up a sea star and throw it back — you will get TWO sea stars

Echinoderms Water Vascular Systems

• Controls- Locomotion, feeding, attachment, sensory reception, excretion and respiration

Madreporite (aboral surface) filters particles from incoming water → stone canal adjusts pressure as animal moves between different depths in water → ring canal is the circular cal running around the central disk → polian vesicles (balloon-like fluid storage structures) → Tiedemann’s bodies filter fluid and store defensive immune cells → radial canals run the length of each arm (5 canals/5 arms) → lateral canals branch off the radial canals and have one-way valves in the water only → ampulla is the muscular bulb above eahch tube foot that works like a pipette bulb → tube feet (podia) is the hollow muscular tubes that have tiny sucker tips

How tube feet move:

• Ampulla contracts → water pushed into tube foot → foot extends

• Ampulla relaxes → water retracted → foot retracts

• ~2,000 tube feet work together in coordinated stepping motion

• Enough suction force to climb vertical walls AND pry open bivalve shells

Pedicellariae:

• Tiny pincer-like structures on aboral surface; movable ossicles open/close like tiny jaws

• Some on stalks; some have toxins

• Function: clean and protect body surface; protect dermal branchiae

Dermal branchiae (papulae):

• Projections of the coelom through the ossicle plates

• Function: gas exchange (respiration) and excretion — equivalent to parapodia in polychaetes

Ambulacral grooves:

• Channels running along the oral (under) surface of each arm

• Contain the tube feet and lateral canals

• Named for their role in locomotion ("ambulacr" = to walk)

Sea Star Stomach Systems

• Cardiac stomach = can be EVERTED (pushed out through the mouth) to digest prey externally; retracts back in after digestion

• Pyloric (gastric) stomach = upper stomach; connects to digestive ceca in each arm

• Digestive ceca (pyloric ceca) = finger-like extensions running into each arm; secrete digestive enzymes; absorb nutrients; allow sea stars to digest prey larger than their mouth

Echinoderm Classes

Asteroidea - Sea Stars

• 5+ arms, stomach eversion, autonomy, sucker tube feet

Ophiuroidea - Brittle Stars

• arms sharply distinct from disk

• no organs in arms

• fast movers

Echinoidea- Sea urchins, sand dollars

• no arms

• round/flat body covered in spines

• tube feet between spines

Holothuroidea - Sea cucumbers

• elongated

• soft

• no visible spines

• Evisceration is (specialized,, voluntary defensive mechanism)

Crinoidea- Sea lilies, feather stars

• filter feeders

• arms with pinnules

• oldest class

Phylum Chordata - Corded Animals

• All vertebrates are chordates

• NOT all chordates are vertebrates

• Two invertebrates chordate groups precede te vertebrates

Three Chordate Groups

1. Cephalochordata (lancelets) — invertebrate

2. Urochordata (tunicates/sea squirts) — invertebrate

3. Vertebrata — all backboned animals

Craniata (Clade)

• the clade that includes ALL animals with a cranium (skull)

  • hagfishes and all vertebrates

• hagfishes technically have a cranuim but lack true vertebrae → places at craniate but basal to vertebrata

• All craniates have cranium encasing the brain, neural crest cells (unique embryonic cell population), complex sensory organs

5 Defining Characteristics:

ALL 5 MUST BE PRESENT AT SOME POINT DURING DEVELOPMENT (not all necessarily in the adult)

1. Notochord

• Dorsal elastic supporting rod extending the length of the body

• Semi-rigid body of cells in a fibrous sheath

• Provides support and axis for muscle attachment; flexible

• In vertebrates: replaced by the vertebral column (intervertebral discs = notochord remnants)

2. Dorsal Hollow Nerve Cord

• Dorsal, hollow, fluid-filled, tubular structure

• Anterior end enlarges to form the brain

• Shift position from ventral solid to dorsal hollow

• Fluid = cerebrospinal fluid (CSF); fills ventricles, covers brain surface

• Originates from ectoderm

• KEY CONTRAST: all invertebrates = ventral SOLID nerve cord; chordates = dorsal HOLLOW nerve cord

3. Pharyngeal Pouches (Gill Slits)

• Perforated slit-like openings leading from pharyngeal cavity to outside

• Originally evolved as filter-feeding device: water in mouth → over gills → out slits; food trapped

• Evolved into gills in fish for gas exchange

• In terrestrial vertebrates evolved into:

  • Parathyroid glands (calcium/phosphate balance)

    • embeded in thyroid gland

    • span trachea in neck rgiona nd regulates calcium balence

    • too much or too little calcium has serious physiological consequences

  • Eustachian tubes (connect ears to throat)

    • runt from the middle ear to throat to equalize pressure on either side of the eardrum

    • if fluid blocks them the eardrum can’t vibrate → muffled hearing

    • “Ear popping”

  • Thymus, tonsils, other neck/jaw structures

4. Post-Anal Tail

• Tail extending posterior to the anus at some developmental stage

  • added to the body behin the end of the GI tract

• Initially evolved for propulsion in water

• Present in ALL chordates at some point

• In humans: visible in embryo; coccyx = adult remnant

5. Endostyle / Thyroid Gland

• In invertebrate chordates: endostyle = ciliated groove that produces mucus for filter feeding; also secretes iodinated compounds

  • group of cells that secrete iodinated hormones

• In vertebrates: becomes the thyroid gland — secretes iodinated hormones (T3, T4) for metabolism regulation

  • thyroid gland = butterfly-shaped gland spanning from the trachea in the neck region

  • functions to maintain metabolism, control long-term body processes, ect.

• Without iodine cannot make function thyroid hormones → goiter = enlarged, buldging thyroid gland

Cephlachordata - Lancelets

• Elongate

• fish like body

• Retain all 5 chordate characteristics as adults

• notochord and nerve cord run the entire length of the body

• filter feeders → use pharyngeal gill slits to trap food

• possibly the closet invertebrate relative to vertebrates

Urochordata - Tunicates

Adults

• Sessile; encased in a tunic (tough outer covering made of tunicin — a cellulose-like polysaccharide)

• Filter feeders via pharyngeal gill slits

• Adults retain only TWO of the five chordate characteristics:

  1. Pharyngeal gill slits

  2. Endostyle

• Adults have NO notochord, NO nerve cord, NO tail

Tadpole Larva

• Free-swimming

• Possesses ALL FIVE chordate characteristics (notochord, nerve cord, pharyngeal slits, tail, endostyle)

• Looks like a tiny tadpole — hence the name

Paedomorphosis

• evolutionary process in which larval or juvenile features of an ancestral organism are retained in/displaced to the adult forms of its descendants

• proposed by Garstang in the 1920’s

  • larval stages are subject to evolutionary forces too

Vertebrata

All vertebrates have 5 chordate characteristics

Vertebral Column

• backbone

• replaces/supplments notochord

• series of articulating vertebrae

Cranium

• bony or cartilaginous skull protecting the brain

Endoskeleton

• internal skeleton that grows with the body

• made of cartilage or bone

Integument

• epidermis + dermis (2 skin layers)

Ventral heart

• closed circulation

• 2 circuits

• red blood cells with hemoglobin

Well-developed coelom

• body cavity that houses organs

Paired Kidney

• for osmoregulation and waste removal

Brain

• 10-12 pairs of cranial nervse

• complex sensory + motor control

Endocrine System

• hormonal regulation

Sexes

• seperate

Multiple clusters of hox genes

• more than invertebraes

• greater complexity

Cyclostomata = Jawless Vertebrates

• Agnatha = jawless vertebrates

  • cyclostomata (circular mouth)

  • earliest vertebrates

  • Have SOME vertebrate characteristics but NOT all → still grouped with vertebrates because of what they do have

  • Feed on all types of other marine organisms; some commercial/economic importance

Hagfishes ("Slime Eels")

• exclusively marine

• Lack: eyes, jaws, fins, and true vertebrae

• Have a cartilaginous skull + notochord (no vertebral column)

• Scavengers — feed on dead/dying animals on ocean floor

• Blind; keen senses of smell and touch

• Live in burrows on the bottom

• Rasping tongue (no true jaw)

  • rasp away tissues of dead/drying fish

  • deceptive feeding strategy: will enter a fish through the anus and eat it from the inside out → fishermen sometimes find hagfish inside intact fish when filleting

• Produce enormous quantities of slime as defense (instantly fills water around predator)

  • coat body instantly; other animals cannot get through the slime mass; fills bucket with disgusting slime

• Used in fish traps

• Skin used commercially: boots, golf bags ("eel skin" products)

Lampreys

• Marine AND freshwater

• Naked skin (no scales); dorsal fins

• Notochord + rudimentary vertebral column (more derived than hagfish)

• Parasites on fish — attach with sucker-like oral disc with rasping teeth

  • raps through scales

  • suc body fluids and release anticoagulant to keep fluids floating

• Well-developed eyes

• Important parasites on commercially valuable fish species

• Introduced into the Great Lakes → enormous consequences; devastated commercial fish populations

• Ammocoetes larva — blind filter-feeding larval stage; lasts 3–17 years in sediment before metamorphosing into parasitic adult

  • all 5 chordate characteristics are visible

  • 7 pairs of gill slits visible down body of adult lamprey

Gnathostomes - Jawed Vertebrates

Why Jaws Matter

• Jaws allowed more efficient prey capture

• Can handle larger prey items than filter-feeding or rasping

• Accompanied by development of 2 pairs of appendages (pectoral + pelvic fins/limbs)

• Jaws evolved from gill arches — 2 pairs of gill arches were lost; others modified (3rd and 4th gill arches became jaw components)

  • gill arches- skeletal rods that support the gill slits

Placoderms — Early Jawed Fishes (EXTINCT)

• Placodermi = first jawed vertebrates in the fossil record

• Had heavy bony armor plating covering head and front of body

• Had paired fins — first vertebrates with this feature

• Ancestral lineage leading to all modern jawed vertebrates (Gnathostomes)

• The cartilaginous fishes (sharks) evolved from bony ancestors like placoderms by retaining cartilage rather than ossifying it