Practical Lab 3

Question 1

Name and describe the germ layers

Answer 1

Ectoderm: surface layer, gives rise to outer covering of animal

Mesoderm: middle layer that forms muscles and most other organs

Endoderm: innermost layer, lines primitive gut, gives rise to lining of digestive tract and related structures such as liver or lungs

Question 2

What distinguishes an acoelomate body plan?

Answer 2

Complete lack of coelom (cavity between digestive tract and outer body)

Question 3

What distinguishes pseudocoelomate body plan?

Answer 3

Has a fluid filled cavity called pseudocoelom, only partially covered by mesoderm cells

Question 4

What distinguishes the coelomate body plan?

Answer 4

Has a fluid filled coelom lined with mesoderm. Mesoderm joins together to suspend organs in coelom

Question 5

Identify this body plan. Name a phylum it is present in

Answer 5

Acoelomate. Phylum: platyhelminthes

Question 6

Identify this body plan. Name a phylum it is present in

Answer 6

Pseudocoelomate. Phylum: Nematoda

Question 7

Identify this body plan. Name a phylum it is present in

Answer 7

Coelomate. Phylum: Annelida

Question 8

What is the latin name of the nematode studied in the lab?

Answer 8

Ascaris lumbricoides

Question 9

How does one distinguish male and female Ascaris?

Answer 9

Male - have curved posterior end, are thinner

Female - straight tail, thicker

Question 10

How do you tell the difference between the posterior and anterior end of a female Ascaris?

Answer 10

The anterior should have three lobes (lips) for the mouth

Question 11

What does the female genitalia look like in Ascaris?

Answer 11

A long coiled tube that starts at a gential pore then gets smaller and smaller as it differentiates. Initial portion: vagina, bigger portion: uterus, middle portion: oviduct, end portion (thinnest): ovary

Question 12

Describe male Ascaris genitalia

Answer 12

At the edge of the anus there is a copulatory spicule (hook-like appendage to hold female open), this attaches to the cloaca (multi-purpose collecting duct for feces and sperm), which is linked to the seminal vesicle, then the thick vas deferens, and from there the very thin testes

Question 13

Describe the digestive system of Ascaris

Answer 13

Starts with a muscular pharynx, then a thin, ribbon-like (flat-looking) intestine stretching to the anus

Question 14

Nematodes typically live in the _______ spaces of aquatic sediments and soils

Answer 14

Interstitial

Question 15

In what part of humans do Ascaris live?

Answer 15

Mature Ascaris live in the intestines, feeding. Larvae will eventually burrow into the alveoli of the lungs

Question 16

What is the common name of annelida?

Answer 16

Segmented worms

Question 17

What is the latin name of the Earthworm?

Answer 17

Lumbricus terrestris

Question 18

Each segment of the earthworm is divided by ______

Answer 18

Septa

Question 19

What is the peritoneum?

Answer 19

Mesodermal epithelium lining the coelom

Question 20

Small, bristle-like appendages on most annelids are called _____

Answer 20

Setae

Question 21

Name the four classes of phylum annelida

Answer 21

Oligochaeta (includes earthworms), polychaeta (includes clamworms), hirudinea, archiannelida

Question 22

What is the purpose of the clitellum and where is it located?

Answer 22

The clitellum surrounds worms during mating, making a cocoon for fertilized eggs. It’s located on the dorsal surface about halfway down the worm but closer to the posterior

Question 23

The mouth and anus are on the ______ surface of the earthworm

Answer 23

Ventral

Question 24

Describe the difference between the crop and the gizzard in earthworms/annelids

Answer 24

The crop is a wide organ that is a storage stomach. It is soft and squishy.

The gizzard is located posterior to the crop and is tough and muscular. It is used to grind up soil

Question 25

In annelids, on the dorsal surface if the intestine is a longitudinal groove known as the _________

Answer 25

Typhlosole

Question 26

Describe the nephridia of annelids

Answer 26

Multi-purpose organs very similar to nephrons that function in both osmoregulation and removal of nitrogenous wastes.

It is primarily a series of tubes

Question 27

Describe the digestive system of the earthworm

Answer 27

It starts with a large, muscular pharynx. This is followed by the esophagus, which goes into the crop (storage stomach), followed by the gizzard (muscular organ for grinding dirt), the gizzard is followed by the intestine

Question 28

Describe the circulatory system of the earthworm

Answer 28

INternal transport occurs in the coelomic fluid, within a closed circulatory system. The fluids may contain respiratory pigments (hemoglobin) to carry oxygen. The Earthworm has five pairs of pseudohearts surrounding the esophagus as well as a long ventral blood vessel.

Question 29

Describe the reproductive systems of the Earthworm

Answer 29

Earthworms are hermaphroditic. The worms attach their clitella and exchange sperm. The small, bulb-like seminal receptacles hold sperm whereas the large seminal vesicles produce it. Testes are inside the vesicles and sperm transfers to the male genital pore via vas deferens.

Female organs include a pair of ovaries connected to the female genital pore

Question 30

What are the defining characteristics of the Clamworm?

Answer 30

Retractable jaws.
Fleshy appendages called parapodia on each segment (which have setae)

Question 31

Describe the digestive system of the Clamworm

Answer 31

The system starts with jaws that are used for catching prey, followed by the mouth, then a muscular pharynx, which leads to the esophagus. On either side of the esophagus are two esophageal caeca. Then comes the stomach-intestine.

Question 32

How are the parapodia used in repiratory/circulatory functions?

Answer 32

They function like primitive gills, being the primary site for gas exchange. The beating motion of parapodia brings in new oxygen-rich water.

Question 33

What two special features help make Arthropoda so successful?

Answer 33

Rigid exoskeleton and jointed appendages

Question 34

What are the latin names of the aquatic and terrestrial Arthropoda we covered?

Answer 34

Aquatic - Cambarus sp.

Terrestrial - * Romalea sp. *

Question 35

Describe the external anatomy of the crayfish

Answer 35

Body is divided into the anterior cephalothorax and a posterior abdomen. A chitinous exoskeleton protects the body. The carapace covers the cephalothorax. The rostrum is the extension of the head, and stalked eyes are located on either side of the rostrum.

The abdomen has several segments and ends with the “tail” end, the telson. There are swimmerets (little legs) on each segment of the abdomen.

Question 36

How can one externally tell a male crayfish from a female?

Answer 36

In male crayfish, the first two pairs of swimmerets are elongated to form a trough-like channel for the transfer of sperm.

Question 37

Describe the digestive system of the crayfish

Answer 37

Mouth > esophagus > stomach (inside the stomach are teeth that form the gastric mill for grinding food) > intestine (runs from stomach through the abdomen) > anus.
There is a yellow digestive gland near the somach that occupies much of the posterior part of the cephalothorax

Question 38

Describe the osmoregulatory/excretory processes of the crayfish

Answer 38

The green gland (located under the stomach - actually pink) functions in osmoregulation. The mandibles (cute little hands) on the ventral side of the crayfish shuffle food into the mouth.

Aquatic arthropod waste is in the form of ammonia.

Question 39

Describe the respiratory/circulatory system of crayfish

Answer 39

They have gills for respiration. They have an open circulatory system with a pinkish heart which recieves blood from the homocoel and pumps it to the rest of the body, bathing the organs. The heart has two tiny holes called ostia where blood re-enters the homocoel.

Question 40

Describe the reproductive systems of the crayfish

Answer 40

Ovaries are orange and coarse, whereas testes are white. They are lateral to the anterior portion of the intestine. (or sometimes closer to the heart)

Question 41

What are insects characterized by?

Answer 41

Three body regions (head, thorax, abdomen), one pair of antennae, and six legs

Question 42

How can one externally determine the sex of the Romalea ?

Answer 42

The posterior end of the female is modified to lay eggs and is called an ovipositor

Question 43

Describe the digestive system of the grasshopper

Answer 43

Mouth > pharynx > esophagus (brings food from the pharynx to the crop) > crop (stores chewed food) > stomach (attached to six double finger-shaped digestive glands, the gastric caecae) > intestine (lying over the intestine are hair-like Mapighian tubules) > rectum > anus

Question 44

Describe the osmoregulatory and excretory systems of the grasshopper

Answer 44

The Malpighian tubules serve as excretory organs, and wastes are removed by the hindgut. The waste is in the form of uric acid.

Question 45

Describe the reproductive system of the grasshopper

Answer 45

The gonads are dorsal to the intestine (near the Mapighian tubules). Males have two testes composed of slender tubules called follicles and are above the intestine. Each testis is joined to a longitudinal vas deferens.

Each ovary (quite large and distinct) is composed of several tapering egg tubes which produce the ova. Each ovary is joined to an oviduct, leading to the vagina.