Lab 4: Phylum Platyhelminthes (flatworms)

Question 1

What clade(s) do Phylum Platyhelminthes belong to?

Answer 1

Metazoa, Eumetazoa, and Bilateria

Question 2

What kind of symmetry of a flatworm?

Answer 2

Bilateral symmetry; meaning that the animal can be divided into mirror image left and right halves by a single plane that passes along the midline of its body

Question 3

What is the directional term for the head end?

Answer 3

anterior

Question 4

What is the directional term for the tail end?

Answer 4

posterior

Question 5

What is the directional term for the side facing up?

Answer 5

dorsal surface

Question 6

What is the directional term for the side facing down?

Answer 6

ventral surface

Question 7

What is the term that means worms are flattened from the top down?

Answer 7

Dorsoventrally flattened

Question 8

What kind of movement do flatworms use?

Answer 8

undirectional movement

Question 9

What is unidirectional movement?

Answer 9

moving with one part of the body primarily leading the way, identified as the anterior end

Question 10

What does triploblastic mean?

Answer 10

development from three germ layers; the endoderm, ectoderm, and mesoderm

Question 11

Platyhelminths have more ________ bodies than diploplastic animals

Answer 11

complex

Question 12

During cleavage, the embryo is called a _______.

Answer 12

blastula

Question 13

Where does the mesoderm layer form? (Inner, middle, outer?)

Answer 13

between the inner and outer layer; middle

Question 14

What is the opening through which the cells move inward ?

Answer 14

blastopore

Question 15

What does the mesoderm (middle layer) form?

Answer 15

muscles and loosely packed connective tissue called mesenchyme

Question 16

What kind of nervous system do platyhelminthes have? What does it mean?

Answer 16

Centralized; consists of a mass of nerve cells (brain), and a nerve cord

Question 17

What are auricles?

Answer 17

sensory cells that detect water currents, solid objects, and chemicals located in two flap-like projections on the head

Question 18

Sensory cells in the ____ detect changes in the environment

Answer 18

head

Question 19

Do flatworms move with purpose?

Answer 19

Yes, their sensory structures repond to stimuli such as food or light. They choose where to go.

Question 20

What is a cilia?

Answer 20

hairlike structures that exist on a flatworms surface that together move too propel an organism

Question 21

What does the mesenchyme do?

Answer 21

acts as a modified hydrostatic skeleton and is referred to as a mesenchymal hydrostatic skeleton

Question 22

The planaria has what kind of digestive system?

Answer 22

Incomplete; one opening serves as both the mouth and anus

Question 23

What is the feeding strategy of most free-living flatworms?

Answer 23

carnivorous predators (hunt other animals) or scavengers (find and eat dead animals)

Question 24

What is asexual reproduction?

Answer 24

the animal splits in two parts and then through regeneration, grow two whole organisms. The two individuals are genetically identical to one another

Question 25

What is a hermaphrodite?

Answer 25

each individual has both ovaries and testes

Question 26

Do flatworms fertilize their own eggs?

Answer 26

No, they exchange sperm with another worm

Question 27

What are two endoparasites?

Answer 27

-flukes -tapeworms

Question 27

What is a definitive host?

Answer 27

the host in which sexual reproduction occurs

Question 27

What is an intermediate host

Answer 27

host in which additional development occurs, but maturation and sexual reproduction do not occur

Question 28

Is Mesenchyme a non-living tissue.

Answer 28

No, it is made up of cells and considered to be living (unlike mesohyl and mesoglea)

Question 29

The part of the free-living flatworm's body that distributes ingested nutrients to all parts of the body is the:

Answer 29

Gastrovascular cavity

Question 30

T/F: An animal that feeds by predation (hunting food) does not require a centralized nervous system

Answer 30

False

Question 31

Which of the following is true about the way gas exchange constrains the body plans of a sponge, an anemone, and a free-living flatworm?

Answer 31

A sponge and anemone are constrained to each layer of the body wall being only one cell thick, while a flatworm is constrained to having a body plan that has a very high surface area to volume ratio by being very flat and thin.

Question 32

Can triploblasts only have incomplete digestive tracts?

Answer 32

No, some can have complete and others can have incomplete.

Question 33

What gives the flatworm shape and support?

Answer 33

the mesanchyme and body wall

Question 34

What are the steps involved in getting nutrients to the cells?

Answer 34

1. obtaining food by scavenging or predation 2. chemical digestion by the gastrodermis secreting digestive enzymes, then the food being digested in the GVC 3. getting rid of undigested material

Question 35

What makes it possible to distribute food to the large surface area of a flatworm?

Answer 35

The highly branched GVC

Question 36

What helps a flatworm locate food?

Answer 36

Chemoreceptors

Question 37

What ingests the food in flatworms?

Answer 37

the pharnyx

Question 38

If an animal increases in size, the volume increases faster than the surface area, because volume is cubed while surface area is squared. So as volume increases, surface area to volume ratio decreases. Why is this significant for animals doing gas exchange?

Answer 38

When there is more volume and less surface area, the slow process of diffusion cannot occur at a rate fast enough to keep all cells alive.

Question 39

What is a flatworms solution to the surface area to volume dilemma?

Answer 39

By increasing the surface area to volume by being very flat, flatworms provide an extensive surface area for the volume of living cells and can provide oxygen at a rate that keeps up with the demand

Question 40

What is the nitrogenous waste in flatworms?

Answer 40

Ammonia

Question 41

What is asexual reproduction?

Answer 41

production of offspring from a single parent that occurs without the fusion of gametes; offspring are genetically identical

Question 42

What is the cost of hermaphroditism?

Answer 42

Energy expenditure

Question 43

What is the benefit of hermaphroditism?

Answer 43

They can reproduce with any planaria, not just male or female but either

Question 44

What is a tegument in a fluke and tapeworm?

Answer 44

tegument replaces the epidermis in larva and protect from hosts digestive enzymes and once cells fuse, there is no membrane between them so fewer ways for immune system or digestive enzymes to hurt them

Question 45

What are the bristle like projections in flukes and what do they do?

Answer 45

Spines; they help anchor themselves to host tissues

Question 46

What are the projections in tapeworms and what to they do?

Answer 46

microvilli; they increase surface area so more surface area more absorption of the already digested nutrients from the host's digestive system

Question 47

What is the anterior end of a tapeworm called?

Answer 47

scolex; they also have suckers

Question 48

The segments in tapeworms are called

Answer 48

proglottids generated behind the scolex

Question 49

Mature proglottids

Answer 49

when proglottids mature and develop testes and ovaries

Question 50

Gravid proglottids

Answer 50

egg and sperm fuse forming fertilized eggs; at posterior end and break off and leave the definitive host with the feces and an intermediate host will ingest them

Question 51

What strategy do flukes use to increase the number of offspring produced and where does it occur in the life cycle?

Answer 51

they use asexual reproduction to increase offspring , occurring in the intermediate host during their life cycle

Question 52

What strategy do tapeworms use to increase the number of offspring produced?

Answer 52

They produce a large number of eggs using a segmented body structure to release them, enhancing survival chances