LAB 14: PHYLUM ANNELIDA

phylum annelida

segmented worms

what are the 3 major groups of annalida?

polychaeta, leeches, oligochaeta

based on the phylogenetic tree, what 2 key points separate phylum annelida from the rest?

trochophore larva & protostome development

are annelids protostomes or deuterostomes?

protostomes

what does having trochophore larva suggest?

suggests an evolutionary relationship with mollusks

what is the order of early development in animals?

morula, blastula, gastrula

morula

solid ball of cells

blastula

hollow ball of cells; blastocoel = space

gastrula

archenteron is the new space formed

what cleavage do protostomes have?

spiral and determinate

what does the blastopore develop into in protostomes?

mouth

what is the body cavity in triploblastic animals called?

coelom

peritoneum

adult tissue that comes from mesoderm

coelom

a fluid or air filled space separating the digestive tract from the outer body wall

what are the functions of the coelom?

absorb shock (protects organs), acts as hydrostatic skeleton, for support

what does the mesoderm layer become in triploblastic animals?

peritoneum

what does the group polychaeta mean?

many hairs

setea

hair/bristles made of chitinous hairs; used for attaching to the ground

parapodia

projections of the body wall, increases surface area; used for swimming/crawling & gas exchange

true or false? polychaeta have a well-developed head with eyes and antennae

true

what does each segment have a pair of for movement?

parapodia

do leeches have hairs/setae?

no

are leeches parasitic or predators?

predators

true or false? leeches are dorsoventrally flattened with suckers on both ends

true

how do leeches feed off victim's blood?

slice victim's skin, force proboscis into cut w. anticoagulant, & blood is sucked into leeches body

what medical uses do leeches have?

reattached limbs and reconstructive surgeries (anticoagulant & blood flow)

what does the group oligochaeta mean?

few hairs

what group is the earthworm in?

oligochaeta

peristalsis

series of muscular contractions, using both longitudinal & circular muscles

how do animals in the oligochaeta group move?

burrow with peristalsis & use setae as anchors to the ground

how do animals in the oligochaeta group feed?

they live in the soil & crawl & eat their way through it; they are herbivores/scavengers & feed at night

are oligochaetas hermaphroditic?

yes, but they do outcrossing

how can earthworms be bad for the environment?

they are invasive species that can damage the local ecosystem

how does the coelom act as a hydrostatic skeleton?

it holds an incompressible fluid & the volume of the fluid in the coelom remains constant

the earthworm organism has a tube within a tube. what is the inner tube?

a complete digestive tract

what does each segment have in an earthworm?

an excretory system (nitrogen waste) and separate muscles (longitudinal & circular)

true or false? earthworms have a complete digestive tract, no nervous system, and incomplete circulatory system

false

what separates the coelomic fluid in one segment from other segments?

septum

what is the advantage of a segmented worm?

controlled movement; each muscle contraction in one segment doesn't alter the hydrostatic pressure in the next

true or false? the earthworm has a thick, multi-layered body wall

true

what is the body wall of the earthworm composed of?

circular & longitudinal muscles

regarding the body wall of an earthworm, what is under the epidermis?

circular muscles

regarding the body wall of an earthworm, what is under the circular muscles?

longitudinal muscles

regarding the body wall of an earthworm, what is under the longitudinal muscles?

petrionium

what is the outermost layer of cells in the intestine?

chloragogen tissue

what is the function of chloragogen tissue?

metabolism

what is the typhlosole?

the infolding of the intestine

what is above the intestine when looking at a cross section of an earthworm?

dorsal blood vessel

what is below the intestine when looking at a cross section of an earthworm?

ventral blood vessel

where are nephridia found in a cross section of an earthworm?

on each side of the intestine suspended in the coelom

what are the components of an earthworm's nervous system?

a bilobed dorsal ganglia (brains) & a ventral nerve cord

do annelids have a complete digestive system?

yes

from dorsal to ventral, what is the order of the parts of the digestive system?

mouth - pharynx - esophagus - crop - gizzard - intestine - anus

3 multiple choice options

anatomy of an earthworm: what is the esophagus covered by?

3 pairs of seminal vesicles

what is the function of the crop in an earthworm?

where food is stored

what is the function of the gizzard in an earthworm?

grounds the food

true or false? earthworms have a closed circulatory system

true

what is the function of the circulatory system?

transports nutrients, oxygen, & metabolic wastes

what are the major circulatory pumps of the circulatory system in an earthworm?

dorsal and ventral vessels

what is the role of hemoglobin in an earthworm's circulatory system?

dissolved into the blood, carrying oxygen around the body

how many hearts (aortic arches) do earthworms have?

5

what is the function of skin or gills in the circulatory system of an earthworm?

gas exchange

what is the function of the nephridia?

where fluid (nitrogenous) waste is processed

how do earthworms reproduce?

worms line up inverted from each other & hold citella together and exchange sperm

what is the function of the clitellum?

provides mucus for the transfer of sperm and later creates a cocoon for eggs

what comes OUT of earthworm after reproduction?

sperm made in testes, matures seminal vesicles, leaves vas deferens

what comes IN earthworm after reproduction?

seminal receptacle recieves incoming sperm

reproduction of an earthworm: what does a slime tube form after eggs fertilize?

egg cocoon

true or false? egg and sperm are secreted into the mucus sheath created by the clitellum. external fertilization takes place.

true

are there free-living larvae in oligochaetes?

no

what develops first in protostomes? mouth or anus

mouth (head first)

what does it mean if you are triploblastic?

you have 3 germ cell layers

what does vermiform mean?

worm shaped

what does metameric segmentation mean?

repeating similar segments

how many pairs of nephridia are present per segment within an earthworms excretory system?

one pair

what is the only system an earthworm lacks?

the respiratory system

how does respiration take place in an earthworm?

through skin even when it has a cuticle

what is the organ system in a tube in an earthworm?

digestive system

what does each segment within an earthworm contain?

a repetition of excretory & muscles (also connections to the nervous system & circulatory system)

what are other major phyla with segmentation?

arthropoda and chordata

a coelom must be lined on all sides by which of the embryonic tissue layers during development?

mesoderm

the earthworm intestine has muscles & blood vessels associated with it. what benefit do these muscles provide?

help food move into intestines

what is the role of blood vessels within the intestinal walls of earthworms?

blood vessels transport nutrients throughout the body

what is the evolutionary advantage of having a typhlosole?

it increases the surface area of the intestine so nutrients can be absorbed more efficiently

what effect would contraction of the circular muscle layer have on the length & width of the earthworm?

length increases & width decreases

what if the longitudinal muscles contracted? how would this effect the length & width of the earthworm?

length decreases & width increases

the crop is an adaptation which allows for food storage. why is this advantageous to earthworms?

allows them to go long periods of time without eating, less likely to be eaten by predators on the surface

why did a more complex circulatory system evolve in annelids?

a complex circulatory system is needed to efficiently transport oxygen & nutrients to each segment