Zoology Exam #3

What class of animals features an eversible proboscis?

Class errantia (pleistannelida phylum)

Where can animals from the errantia class be found?

Brackish water, FW, ocean

Describe the nervous system of animals in the Errantia class.

They have a well-defined head with many sensory organs

• eyes

• Tentacles for chemo/mechanical receptors

• Palps around the mouth for taste

What are the uses of parapodia?

Swimming, crawling, anchoring, and respiration

Describe eyes of animals in the Errantia class.

Range from simple eye spots (light receptors) to even more complex with retinas, lenses, corneas

• may have extra retinas sensitive to wavelengths of light found in deeper water

Where are parapodia found?

On every segment (errantia class)

What type of larvae do errantia class organisms have?

Trochophore

Describe reproduction in the Errantia class of organisms.

• gonads appear temporarily during breeding season

• Use external fertilization

• Swim to surface at dawn/dusk and females secrete a pheromone to attract males creating masses (spawn in groups)

What is special about the nerius cone variety of Errantia worms?

They grow large eyes and gonads during breeding season

Are Errantia class animals deocious or monoecious?

Dioecious

What is the blastodisc?

where the embryo develops in a bird egg

Why is the yolk so important in bird eggs?

It serves as food for the developing embryo

What are chalazae?

thickened “ropes” through the albumin which hold the egg yolk in the center of egg

What is the Albumin?

An egg white for cushioning in bird eggs

Where does cleavage occur in bird eggs?

In the blastodisc

What is special about the cleavage stage, the blastula, and gastrulation in bird eggs?

They are done in a more 2-D way due to the blastodisc being flatter 

When is the blastula made in bird eggs?

As cleavage occurs in the blastodisc

Where are additional cells made in bird eggs?

In the future posterior of embryo

What is the “shelf” in bird eggs?

the thickening projects anteriorly as a shelf. cells from the blastodisc above also drift down to join the shelf

Describe how the blastocoele forms in bird egg.

Cells drift down to join the shelf until a 2 layered blastula with a space in between, the blastocoele, forms

What happens in gastrulation?

cells from outside move inside

What does gastrulation look like from the top?

you see a line and cells are moving in, into this crease to fill the blastocoele, make the archenteron (gut)

What is the primitive streak?

The line where cells move in during gastrulation (bird eggs)

What is on the anterior end of the bird egg?

A pit and a thickening of cells

What happens to cells that move into Hensen’s node?

They become special vertebrate cells that make the notochord - mesodermal 

What happens to the primitive streak as gastrulation progresses?

It gets smaller: the primitive streak and Hensen’s node retreat posteriorly  

What does the notochord do?

induces the ectoderm above it to make the nervous system, which develops A —> P

What happens as the primitive streak and Hensen’s node retreat posteriorly?

cells moving in at the notochord push anteriorly as streak retreats, laying down the notochord (A→P)

What do somites become?

back muscles and vertebrae

What is found laterally to the somites?

metanephridia for the kidney

What is found laterally to the nephridia?

The ceolom

What forms somites?

Alongside the neural tube, the mesoderms forms blocks, which are somites

When are blood islands formed?

When the mesoderm coalesces into blobs

What is developing below the ceolom in bird eggs?

gut is forming below and it’s continuous with yolk

Where does the heart form in bird eggs? What forms from the heart?

develops from mesoderm centrally in the embryo. Major arteries and veins form from the heart 

Do all blood vessels form from the heart in bird eggs?

No, blood vessels out in the body form independently

What happens after blood islands form?

They have to grow into find the heart/major arteries to join them 

What class do earthworms and leeches belong to?

Sedentaria

What is the major characteristic tuberculosis-dwelling worms have?

fans made from mouthparts; some hold them out in water

What are fans used for? (Sedentaria class)

• some may extend them over the substrate to pick up food 

• May be used for respiration 

What family of worms is also referred to as “spoon worms”?

Echiura

Why are Echiura worms called “spoon worms”?

They extend a ciliated “spoon-like” proboscis out onto the substrate to collect detritus 

Describe the body of a worm in the Echiura family.

muscular body covered with a cuticle 

Describe the circulatory system of worms in the Echiura family.

have a closed circulatory system

What does the nephridia do in worms of the Echuria family?

empty waste outside and may also be used for gamete release

Describe the male worm in the Echuria family.

a little parasite living inside the nephridia pore so when the female releases the eggs, the male is there to fertilize them and out they go 

What is the larva like in the Echiura family?

Free-swimming

Describe how sex is determined in the Echiura family.

• if they settle on the substrate, they become female

• if they settle on a female, they become male

Which family of worms’ sex is determined based on where they settle?

Echiura family

What is special about the blastula in bird eggs?

It’s completely flat

Do ispoods select one environment over the other?

Yes, Isopods prefer darker environments over those with light

Which class of animals is “lip foot”?

Chilopoda

Which class do centipedes belong in?

Chilopoda

How many segments can centipedes have? And how long will they be?

15-193 segments and can reach lengths up to 30cm.

Describe the feeding habits of Centipedes.

They are carnivorous and have modified appendages with long poisonous claws on them just behind the head, which they use to inject venom into prey.

Describe centipede’s long walking legs.

There is one pair of legs per segment, held lateral to the body and the last pair extends backwards and performs a sensory function

Which class of animals are “double foot”?

Diplopoda

Descibe the feet of millipedes.

two pairs of appendages per segment: these are located ventrally on the body.

Descibe the collum Segment found in a millipede.

• located behind the head

• lacks legs and gives the animal enough strength to burrow and plow through detritus

What is one difference between centipedes and millipedes?

Centipeds have class and inject posin into their prey whereas millipedes have no claws and do not inject potion into their prey but they do release nasty chemicals from their repugnatorial glands

Which order of organisms includes earthworms, FW worms, leeches?

Clitellata

Where do earthworms live?

• interconnecting burrows 

  • damp weather, sit with their heads out of the burrows 

  • dry conditions, burrow deeply, make a mucus burrow and go dormant

What structure is used in earthworm reproduction?

Clitellum and through the cuticle

Describe earthworm digestion.

have a mouth, pharynx, crop for storage, a gizzard to grind, intestine, and an anus

Describe the earthworm’s nervous system.

brain, ventral cords, giant neurons for quick retraction into their burrows 

Describe earthworm excretion.

Through metanephirida, found in every segment

Describe reproduction in leeches.

• hermaphroditic, exchange sperm by only a penis or hypodermic injection 

  • use clitelleum makes a cocoon for embryos 

Describe the nervous system of the leech.

• have 21 pairs of ganglia (1 pair/segment)

  • large neurons 

  • have brain studied for neural circuitry/development 

Describe feeding habits of leeches.

• some are carnivorous, others suck blood 

  • have chitinous jaws (3 parts) 

What do leeches secrete?

• an anesthetic and an anticoagulation

Why are spinuncla in their own subclass now?

They have no segments and no setae 

What subphylum has peanut worms?

Sipuncula

Describe feeding habits of peanut worms.

• proboscis = introvert, which they pop in and out 

  • mouth inside surrounded by tentacles 

    • catch organic matter on the tentacles mucus —> transported by cilia to the mouth 

Describe digestion of peanut worms.

• U-shaped gut with anus emptying below the proboscis 

Describe reproduction in peanut worms.

• deicious; gametes released through nephridia (also used for excretion) 

Describe feeding habits of animals in the subphylum Chaetopteridae.

• Parapodia used as fans to bring water (plus food) into and out of the burrow water + food go in one direction 

  • captures food when full, they roll it up and swallow it 

Where can animals in the subphylum Chaetopteridae Be found?

Living in a U-shaped burrow

What are some of the parasitic nematodes that affect humans?

• ascaris

• Hookworms

• Trichina

• Flarial worms

Descibe how Trichina infect humans.

make a muscle cell become a nurse cell and can live 10-20 years

What do hookworms do?

Suck blood in human (or animal) intestines

Why is ascaris such a significant human Nematode parasite?

It infects 1.27 billion humans

Describe digestion in the Ecdysozoa CLADE

• mouth —> muscular pharynx  that sucks in food 

  • intestinal wall is only one cell thing

    • waste exits anus by muscular contractions squeezing and blasting it out

What phylum of animals can be found everywhere?

Nematodes

What is required before animals in Ecdysozoa can grow?

They must shed their external cuticle

Describe how animals in the Ecdysozoa clade have an external cuticle.

secreted by their epidermis, which is called a hypodermis 

What forms the hypodermal chord in Ecdysozoas?

syncytial cells with cell body that has nucleus located beneath the surface: these are cell gathered together into a hypodermal chord

In Ecdysozoa, there are 4 hypodermal chords. Explain.

• 2 lateral cord: these also run the excretory ducts

• 1 dorsal

• 1 ventral   

  • In the dorsal and ventral cords, they run a dorsal and ventral nerve cord

Describe muscles in Ecdysozoas.

Only longitudinal so the animals whip along

In Ecdysozoas, instead of nerve chords sending nerves to muscles, what happens?

muscles send extensions (non-contractile) to contact the nerve cord because muscle cell body with nucleus below this and extends arm that is non-contractile to meet a nerve cord 

Which phylum of animals includes the “horsehair worms”?

Nematomorpha

Which phylum includes the “penis worms”?

Priapulida

Which phylum includes “velvet worms”?

Onycophora

Which phylum is the “water bears”?

Tartigrade

Where can Tartigrade be found?

live in water film on mosses and lichens

Describe gas exchange in the Tartigrade.

Across the body wall

Describe how Tartigrades move.

uses some muscle, hydrostatic skeleton

Describe a tartigrade’s reproduction process.

Molt a cuticle that covers the body; as they molt eggs come off too

• diecious, but in some, no males found

Describe how and what tartigrades eat.

• may be carnivorous (eat Rotifers or nematodes) or may eat plant juices

• the mouth has stylets or little knives for piercing food. Muscular pharynx sucks out juices

Describe the body plan of animals in the Nematomorpha Phylum.

• outer cuticle, longitudinal muscles only, have hypodermal pores like nematodes 

What must adult Nematomorphas do?

those who use crickets or grasshoppers as hosts must get host to enter water because adults reproduce in water