Zoology Exam 3

Errantia are ____ or _______ worms

Errant, freely running

Where do errantia live?

Freshwater, brackish, marine environments

Errantia are ______ or ______

active scavengers, predators

How do errantia capture prey?

Have jaws with teeth and an eversible proboscis that can shoot out to capture prey and grasp it effectively.

Head (errantia)

Well defined head with many organs

What organs are present in the head of errantia?

Eyes, tentacles, sensory palps

What do errantia use tentacles for?

Chemosensory and mechanosensory information

Where are the sensory palps of errantia located?

Around the mouth

Different eye types of errantia

• Simple eyespots to tell light/dark

• More complex with a retina

• Even more complex with retina, lens, cornea

Why do some errantia have extra retinas?

Sensitive to wavelengths of light found in deeper water

Errantia have segments, what might be located on these segments?

Parapodia

What can parapodia be used for?

crawling, swimming, anchoring in a burrow, and respiration

In bird eggs, what do the yolk and blastodics form together?

All one cell

Where does the embryo develop in a bird egg?

In the blastodisc

What is the purpose of the yolk in a bird egg?

Feeding

What is the purpose of albumin in a bird egg?

Egg white for cushioning the yolk and embryo

What are chalazae?

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

How do cleavage and relative processes occur in an egg?

In a 2D manner

Why does development of an egg happen in a more 2D manner?

The blastodisc is flatter

How is the blastula of a bird egg made?

cleavage occurs in the blastodisc and more cells made in the future posterior of embryo

How is the blastocoele in an egg formed?

Cells from blastodisc drift down to join the shelf until you have a 2 layered blastula with a space in between

What happens after blastula formation of the egg?

Cells move inside for gastrulation → looks like a line

Describe cell migration during gastrulation

Cells move to fill the blastocoele, make the archentron (gut) along a line

The line where cells move in is known as the

primitive streak

What is Hensen’s node?

Located at the anterior end, a thickening of cells located in a pit

Cells that move in at Hensen’s node become special vertebrate cells that make the _____

notocord

What happens to Hensen’s node and the primitive streak as gastrulation continues?

Primitive streak gets smaller and they both retreat posteriorly

What else occurs as the primitive streak retreats?

Cells moving in at its node push anteriorly, laying down notocord

How is the notocord laid down?

From anterior to posterior

What does the notocord do?

Notocord induces ectoderm above it to make nervous system

Once the ectoderm starts to make the NS, what forms first?

The brain

Direction of nervous system development?

Develops anterior to posterior

What else forms during nervous system development?

Neural tube formation

What does the mesoderm do while development occurs?

Forms blocks alongside round tube

The blocks formed alongside the round tube are known as

Somites

What do somites eventually form?

Back muscles and vertebrae

The nephridia are for the

kidney

Lateral to nephridia is the

coelom

Gut formation of egg

Forming below nephridia area and is continuous with the yolk

How does the heart develop in an egg?

Develops from mesoderm centrally in the embryo

How are major arteries and veins formed?

From hearts

Blood vessels out in body form

independently

Blood vessel formation sequence

• mesoderm coalesces into blobs to form blood islands

• then cell around outside from wells of vessels while those in the center make blood cells

• have to grow to find the heart/major arteries to join them

Habitat (Class sedentaria)

Live in tubes

Nutrition (sedentaria)

Detritus feeders

What are the fans made of in sedentaria?

mouthparts

What are fans used for in sedentaria?

• some hold out in water

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

• may be used for respiration

Family _____ are also known as “spoon worms”

Echiura

What do echiura eat?

Detritus

How do echiura eat?

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

Body plan (echiura)

Muscular body covered with a cuticle

Circulatory system (echiura)

Closed

Coelom (echiura)

Big coelom

Excretion (echiura)

Nephridia empty outside and may also be used for gametes

Reproduction (echiura)

Dioecious

Characteristic of male echiura

In some, male is parasitic, living inside the nephridophore to fertilize eggs as they exit

Larva (echiura)

Free swimming

How is the sex of echiura determined?

Based on their settling pattern

If a echiura larva settles on a substrate, they larva will be

female

If an echiura settles on a female, it will form a

male

Citellata have a ____ that is used for _____

clitellum, reproduction

Earthworms, freshwater worms, and leeches are included in order

clitellata

Where do earthworms live?

In interconnecting burrows

If earth worms are in damp weather, how do they sit?

With their head out of their burrow

If earthworms are in dry conditions, what do they do?

burrow deeply, make a mucus burrow and go dormant

Digestion (Earthworms)

mouth, pharynx, crop for storage, gizzard for grinding

Food pathway (Earthworms)

After gizzard → intestine → anus

Respiration (Earthworms)

Through cuticle

Nervous System (Earthworms)

• brain, ventral nerve cords

• giant neurons for quick reaction into burrow

Reproduction (Earthworms)

• line up facing opposite direction

• hold on by embedding seatae into partner and mucus

• sperm released behind eggs

• sperm is deposited into seminal receptacle which is anterior from the egg pore (segment 9)

• Exchange sperm, separate

• The clitellum secretes a cocoon with protective coating that slides anteriorly

Egg location (Earthworms)

Segment 14

Sperm location (Earthworms)

segment 15 (behind eggs)

Fertilization (Earthworms)

1. picks up worm’s eggs

2. picks up sperm from partner from seminal receptacle

3. adds some albumin

4. pastes off worm at anterior end

5. seals up

6. embryos develop and eventually hatch from cocoon

Excretion (Earthworms)

Metanephridia in early segment

Where are leeches typically found?

Freshwater, some are terrestrial

Diet (leeches)

some carnivorous, eating small insects, others suck blood

How do leeches suck blood?

• have chitinous jaws with 3 parts

• Secrete an anesthetic

• Act as anticoagulant

Nervous system (leeches)

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

• Large neurons

• Have been studies for neural circuitry/development

Reproduction (Leeches)

• hermaphroditic

• exchange sperm via penis or hypodermic injection

• clitellum makes a cocoon for embryos

Subphylum sipuncula are also known as ______

peanut worms

Where do peanut worms live?

Marine, can live deep (5000 m)

Body plan (Sipuncula)

• No segments, no setae

How do peanut worms capture food?

Through a proboscis

How does the proboscis of peanut worms work?

Introvert which they pop in and out, mouth inside, surrounded by tentacles

How do peanut worms bring food into their mouths?

Food gets caught on mucus transport by cilia to mouth

Excretion (Peanut worms)

• u-shaped gut with anus emptying below the proboscis

• have nephridia for excretion and for releasing gametes

Where do chaetopterida live?

In u-shaped burrows

How do chaetopterida bring water and food into their burrow?

• They use parapodia as fans

• water and food go in one direction

How do chaetopterida capture food?

animal secretes mucus net

What do chaetopterida do when they’re full?

They roll mucus net up and swallow it

Phylum ____ are known as nematodes

Nematoda

Where are nematodes typically found?

Everywhere, parasitic on plants, animals, or free-living

How do nematodes grow?

They have an external cuticle that they shed

How is the cuticle of a nematode secreted?

by their hypodermis

What is the hypodermal cord made of?

Syncytial cells with cell body that has nucleus located beneath the surface

How many hypodermal cords do nematodes have?

4

Breakdown of hypodermal cords in nematodes?

2 lateral cords, 1 dorsal, 1 ventral

What else are located in the lateral cords of nematodes?

Excretory ducts

What else runs through the dorsal and ventral hypodermal cords?

a dorsal and ventral nerve cord

Muscles of peanut worms

only longitudinal muscles