Chapter 33: Pt 1. An Introduction To Invertebrates

Question 1

Invertebrates are animals that lack a back bone. They account for ___% of known animal species.

Answer 1

95%

Question 2

_________ are basal animals that lack true tissues.

Answer 2

Sponges

Question 3

Define sessile

Answer 3

Fixed in one place, immobile.

Question 4

Sponges have organized cells supported by a skeleton made of 3 different things. What are they?

Answer 4

1. Spongin fibers
2. Calcareous spicules
3. Silica spicules

Or sometimes, no skeletal structure at all.

Question 5

How do sponges eat?

Answer 5

They are suspension/filter feeders.

• choanocytes create a current that draws water in through the sponge’s pores into the spongocoal and out of the osculum
• food particles from the water get trapped in the mucus that coats the projections
• food is transferred to amoebocytes

Question 6

How do sponges break down the food particles?

Answer 6

Phagocytosis

Question 7

In some reef systems, sponges are __________ feeders - taking in enough biomass to double every 2-3 days.

Answer 7

voracious

organisms who devour great quantities of food

Question 8

Sponges have a chamber called an _______, which consists of many spongocoel and choanocytes.

Answer 8

atrium

Question 9

What is the mesophyl?

Answer 9

The center layer of a sponge, between the outer and inner layer of cells.

Question 10

Both the outer and inner layer of a sponge’s wall have contact with water. What does this mean?

Answer 10

Gas exchange and waste removal can occur by diffusion across the cell membranes of both the inner and outer wall.

Question 11

What are amoebocytes?

Answer 11

Cells that move through the mesophyl. They take up absorbed food and carry nutrients to other cells.

Question 12

Sponges have three body types. What are they and what are their differences?

Answer 12

1. Asconoid
   
   • smallest, simplest body design.
   • looks kind of like a tear drop.
2. Syconoid
   
   • middle sized, somewhat complex design.
   • looks like the tear drop, but has flagellated canals along the sides.
3. Leuconoid
   
   • largest, most complex design.
   • looks like a typical sponge with many oscula.

Question 13

How do sponges contribute to the antibiotics we have today?

Answer 13

There are many bacteria that live within the sponges that help with antibiotics.

Question 14

Sponges are refuges

What does this mean?

Answer 14

They provide habitats for a wide variety of animals

Question 15

What phylum do sponges belong to?

Answer 15

Phylum Porifera

Question 16

Define eumetazoa

Answer 16

Clade of the animal kingdom that includes all multicellular animals except sponges

Question 17

What is gastrovascular cavity?

Answer 17

Cavity in the body that digests food and transports nutrients throughout the body
- only has one opening, mouth and anus are the same

Question 19

What are cnidarians?

Answer 19

A phylum of animals belonging to the clade eumetazoa

• jellyfish, anemonies etc.

Question 20

What are characteristics of cnidarians?

Answer 20

• Two body types
  > sessile polyps
  > motile medusas
• Simple diploblastic, radial body plans
• Central digestive compartment (gastrovascular cavity)
• Mouth and anus are same opening

Question 21

What is the body plan of a cnidarian?

Answer 21

Sad with a central digestive compartment (gastrovascular cavity)

Question 22

What is a polyp?

Answer 22

A sessile cnidarian that adheres to substrates.
- they extend their tentacles to catch prey

E.g., sea anemone and hydras

Question 23

What is a medusa?

Answer 23

A motile cnidarian that swims freely.
- their tentacles face downward for locomotion

E.g., jellyfish

Question 24

What are the 3 layers of a cnidarian’s wall?

Answer 24

Epidermis
Mesoglea (gel-like)
Gastrodermis

Question 25

What is a unique trait to cnidarian tentacles?

Answer 25

They are composed of cnidocytes
- cnidocytes are cells that consist of specialized organelles called nematocysts that eject a stinging thread to catch prey

Question 26

True or false:

Cnidarians have no brain

Answer 26

True

Question 27

Electrical synapses dominate in Cnidarians with nerve nets. What does this mean?

Answer 27

If you touch the tentacle of a cnidarian, the entire cnidarian will retract because it cannot exactly sense where it is being touched.
- echinoderms do the same, have radial nerves in each arm.

(Humans do not do this; if you touch someone’s hand they will retract their hand only, not all of their limbs.)

Question 28

What are characteristics of sponges?

Answer 28

• No true tissues or organs
• No symmetry
• No nerves, muscles, mouth or digestive system
• Sessile
• Reproduce sexually and asexually
• Filter feeders

Question 29

What are the 4 classes of Phylum Cnidaria?

Answer 29

Hydrozoa
Scyphozoa
Cubozoa
Anthozoa

Question 30

What are the characteristics of Class Hydrozoa?

Answer 30

• Has polyp and medusa stages
• Marine (a few freshwater)

E.g., Portuguese man-of-wars, freshwater hydras, Obelia

Question 31

What are the characteristics of Class Scyphozoa?

Answer 31

• Live as medusas (polyp stage is absent)
• Marine
• up to 2m in diameter

E.g., true jellyfish

Question 32

What are the characteristics of Class Cubuzoa?

Answer 32

• Live as box-shaped medusa
• Marine
• complex eyes, potent venom

E.g., box jellies, sea wasps

Question 33

What are the characteristics of Class Anthozoa?

Answer 33

• Live in polyp stage, medusa stage absent.
• Marine
• mostly sessile, many colonial
• secrete hard exoskeleton

Question 34

What are bilaterians?

Answer 34

A phylum of animals belonging to the clade eumetazoa with bilateral symmetry

Question 35

What are the phylums of the clade Bilateria?

Answer 35

Lophotrochozoa
Ecdysozoa
Deuterostomia

Question 36

What are the 4 phylums of lophotrochozoans?

Answer 36

1. Phylum Platyhelminthes
2. Phylum Rotifera
3. Phylum Mollusca
4. Phylum Annelida

Question 37

What are the characteristics of the phylum platyhelminthes? What are the classes?

Answer 37

• Triploblasts
• Bilaterial symmetry
• Dorso-ventrally flattened
• Gastrovascular cavity
• No blood vessels or structures for gas exchange
• flat bodies = large surface area for gas exchange

Classes:

1. Turbellaria - flatworms
2. Cestoda - tapeworms
3. Trematoda - flukes

Question 38

Describe the body of a turbellaria (flat worm).

Answer 38

• Two eyespots
• Two ventral nerve cords (lined along its stomach)
• Ganglia (where the nerve cords meet at the head)
• Gastrovascular cavity (food enters through the mouth and pharynx)
• needs water/damp environment

Question 39

Explain the life cycle of a parasitic trematode, Schistoma (bilaterians in the phylum platyhelminthes).

Answer 39

1. Male and female flukes (trematodes) reproduce sexually in a human host.
2. Human excretes feces and the fertilized eggs within the feces develop into larvae (with water contact) and infect snails as their new host.
3. Flukes reproduce asexually in the snail and the larvae swim freely in the water.
4. The larvae penetrate the skin of the humans working in the ponds and infect them again.

Question 40

What are monogeans?

Answer 40

Parasites of the phylum platyhelminthes that infect fish

• life cycle is the same as a trematode, except we injest infected fish instead.

Question 41

What are the characteristics of tapeworms (phylum platyhelminthes, class cestoda)?

Answer 41

• lack a digestive system
• absorb nutrients from host’s intestine
• sexually reproduce and humans excrete the fertilized eggs
• mostly infect vertebrates

Question 42

Describe the body of a tapeworm (phylum platyhelminthes, class cestoda).

Answer 42

• has a head (scolex) with suckers and hooks
• body segments (proglottids) contain eggs that break off as they ripen with eggs
• lack gastrovascular cavity
• hermaphrodites (but still cross mate)

Question 43

What prevents tapeworms from being digestive while they live in the intestine?

Answer 43

They have a protective mucus layer