[BIO 10.01] Module 5

Bilateria

• a large clade that contains almost all triploblasts animals

• can be divided into two clades:

  • protostomes

  • deuterotomes

Platyhelminth

• consists of free-living and parasitic species

  • most free-living flatworms are aquatic, terrestrial flatworms are limited to moist areas

• dorsoventrally flattened bodies

• aceolomate

• have more than one host organism

  • the first host is usually invertebrate while the final host is vertebrate

• Some debate on the validity of the phylum

  • no clear difining feature

physiology of platyheminthes

• free living are either predator Sr scavengers

• parasitic feed on host tissues

• most have an incomplete digestive system

  • the single opening is use for eating and expelling waste

• Digest extracellularly

• tapeworm lack digestive system

• flatworms have a simple excretory system for waste fluid

  • flaggated

• lack a respiratory and circulatory system

  • gas and nutrient exchange is facilitated by diffusion and extracellularly jnctions.

  • this necessitates the flat body plan

  • monoecious / hermaphrodite

  • fertilization is internal

• in some group, asexual reproduction via regeration is common

• have a simple nervous syste

  • longitudinal nerve cords with transverse nerves forming a ladder pattern

• a large concentration of nerve cells can be

turbellaria

• mostly free living

• inhibit marine freshwater an moist terrestrial habitats

• move with a combination of cilla and muscular

monogenia (monogenetic flukes)

• all species are parasitic

  • mainly external parasites of fish

  • attatched to the host with hooks

• only have one host during their life cycle

trematoda (flukes)

• internal parasites

• Life cycle involves a primary host and one or more secondary host

  • primary host is a molusk

• causative agent for several diseases

schistosomiasis

• common in tropical and subtropical countries, especially in areas with poor water quality and sanitation

  • contact with infested water allows the larvae to enter the skin

  • schistosomiasis is prevalent in the PH

cestoda

• internal parasites

  • live in the digestive tract of the host

• lack a digestive system

• attatch

• infection in humans typically occurs through consumption of poorly cooked or uncooked pork, beef, and fish
  

proglottids

• segments that facilitate reproduction

• mature detach and are passed in the feces of the host

Annelida (segmented worms)

• exhibit metamerism

• ceolomate

• inhabit marine, freshwater, and terrestrial habitats

  • terrestrial species inhabit the soil
    

metamerism

• True segmentation

annelida physiology

• each segment has chaetae/setae that aid in movement

• has complete digestive system with specialized organs

• pair of methanephirida

• gas exchange is cutaneous

• has a closed circulatory system with aortic arches for pumping blood

• nervous system is well developed with two ventral chords and a nerve ring around the pharync

• monoicious or dioecious

  • monoicious have permanent gonads
    

chaetae/ setae

polychaeta (bristle worms)

• mostly marine

• have multiple chaetae per segment

• lack clitellum

parapodia

clitella

• have fewer, reduced chaetae or no chaetae

• clitellum is present

clitellum

oligochaeta

• earthworms

• reduced state

• earthworms are beneficial to the soil

  • earthworm activities mixes topsoil and subsol

  • are the intestine of the soil
    

hirudinea

• leeches

• completely lack setae

• possess anterior and posterior suckers

• either predatory or parasitic

• were used traditionally for blood letting throughout history

• leeches are used in modern medicine as well

  • are used to relieve congestion in reattatched appendages while the blood vessels heal
    

Mollusk

• mostly marine phylum with 900000 described sepcies

mollusk anatomy and physiology

• soft bodied

• varied body plans

• shared characteristics:

  • foot

  • visceral mass

  • mantle

• most have an open circulatory system

  • cephalapods have a closed circulatory system

• most are dioecious

  • some are hermaphoditic

• larvae are typically free swimming trochophore larva

foot

• adapted for movement or attatcmment to surfaces

• usually located on the ventral surfacce

• movement is typically

• foot is modified in some groups

  • attachment disk in limpets

  • siphon in cephalapods

visceral mass

• contains most of the mollusk's internal orgnas

• digestive, nervs, excretory, reproductive organs

• found above foot

mantle

• tissue that extends outward from the visceral mass

• secretes the shell

• contains sensory receptors

• the space between the visceral mass and thee mantle is called the mantle cavity

mantle cavity

• houses the respiratory organs such as gills and lungs

ctenidia

• gills in mollusks

radula

• found in all mollusk's except bivalves

• file like teeth made of chitin for scraping food prior to digestion

veliger

caudofoveta and selenogasteres

monnoplacophora

• one plate

• one caplike she'll covering the dorsal side

• simple radula

monophlacophora

gastropoda

• stomach foot

• largest class of mollsks

• snails, slugs, conhches, limpets, sea butterflies

• only class with terrestrial species

• are either shell-bearaing or have a reduced shell

  • shelled are asymmetrical with a coiled shell and twisted visceral mass

  • have a head with eyes on tenticles
    

cephalopoda

• head foot

• octopses, squid, cuttleflish, nautilus

• include shelled and reduced shell groups

  • reduced shell is internal

• predatory with beaks

• Hae complex nervous systems and eyes

  • higl levels of intelligene

    • octopuses are capable of observational learning and tactile exploration

  • have vivid and sometimes rapidly changing coloration

  • have a closed circulatory sytem

  • produce dark ink for defence
    
    

chromatophores

• color changing cells in cephalopods

cephalopoda circulatory system

• two hearts for mobbing blood through gills

bivalvia

• two valves

  • two part shells fused with ligaments on the dorsal side and opened and closed by muscles

  • oyesters, muscles, scallops, clams

  • freshwater and marine

• lack a radula

• filter-feeders

• some species have eyespots along the edge of the mantle

schaphopoda

• boat feet

• also known as tusk shells or tooth shells

• single conical schell on both ends

• lack crenidia

ecological significance of mollusks

• are important food source

  • 6o million tones of mollusks were harvested from the Eastern US in 2014 amounting to 2.68 billion USD

• are threatened by ocean acidification

  • high levels of acidity affect the availability of calcium

  • shelled mollusk's are vulnerable to increases in acidity

Crustacea

• the second largest

Crustacea General characteristics

• only arthropod group with two pairs of antennae

• most have a cephalothorax and abdomen

• many have a carapace

• exoskeleton is reinforced with calcium carbonate

• biramous appendages
  
  

carapace

• a plate that covers the cephalothorax

Malaco

Isopoda (isopods)

• the only crustaceans with fully terrestrial species

• dorsoventrally flattened

• no carapace

• many species can roll into ball for protection

amphipoda

• lack a carapce

• laterally compressed

• typically marine with some beach dwelling, freshwater and parasitic species

Euphausiacea (krill)

• only 90 species but are important as planktonic organisms

• most are bioluminescent

• major part of the diets of many fish and baleen whales

Decopada

• 18,000 species

• crabs, lobsters, crayfish, true shrimp

• 5 pairs of walking legs

• size ranges from a few mm to 4 meters

• economically important

  • numerous species are food sources

• crabs have a variety of forms

  • distinguished by a broad cephalothorax and reduced abdomen

• The crab body plan evolved multiple times outside of the true crabs (Brachyura)

Carcinization

• the process of non-crab crustaceans independently evolving crab like forms

Hexapoda

• most numerous group of arthropods

• 6 walking legs

  • all legs are uniramous

• 3 tagmata

  • head

  • thorax

  • abdomen

• 2 classes

Class insecta

• the largest group of animals

  • around 1.1 million currently describe

  • found in almost every habitat that supports life

    • few are truly marine; some are

insect anatomy and physiology

• the only invertebrates capable of flight

• usually have 2 pairs of wings attatched to the thorax

  • some groups have 1 or none

  • true flies have modified hindwings called halteres that aid in balance during flight

• The head typically contains: a

  • 1 pair of compound eyes

  • 1 pair of antennae

  • 3 ocelli

• legs are modified for special purposes

• have varied diets

  • most feed on plants

  • some feed on dead animals or hunt other animals

• many are parasitic

  • some parasitic insects are parasitized by other insects

• have an open circulatory system

• insects breathe with

• have keen senses

ocelli

• Simple light detecting organs

Sucking mouthparts

proboscis

Chewing mouthparts or mandibles

are adapted for seizing and crushing food

sponging mouthparts

mouthparts with a large pair of lobes for consuming liquid food

compound eye

• composed of thousands of clusters of photoreceptor cells

insect development

• a few insects such as silverfish undergo direct development

• many insects undergo metamorphosis

• two types of metamorphosis

  • hemimetabolus

metamorphosis

hemimetabolous

• incomplete metamorphosis

• the larva stage is called a nyh and the wings develop externally over successive molts

• aquatic nymphs have trachea gills and

holometabolous

• complete matamorphosis

• occurs in 3 distinct stages

  • larva (growth)

  • pupa (differentiate)

  • adult (reprodction)

• 88% of them go through this

larva

• worm like in shape

• usually have chewing mouthparts

pupa

adult

• winged stage

• do not undergo

Eusocial insects

• have complex social structures regulated by chemical and tactile communication

• are differentiated by castes

• seen in honey bees, ants, and termites

• in ants and termites, the workers and soldiers are wingless

• ants have economic behavioral patterns

  • forcing other ants to do work

  • farmining fungi

  • sewing nests with silk

  • simple tool use Hu

Bees Queen

sexually nature female, only one per hive

Bees Drones

Bees Workers