Section 29.3 (Exam 2)

Question 1

What are the two major bilaterian goups?

Answer 1

Protostomes and Deuterostomes

Question 2

What are some bilaterian synapomorphies?

Answer 2

Anterior-posterior axis

Triploblastic

Centralized nervous system

Question 3

Name the 6 members of the non-bilaterian groups. (Monoblastic and diploblastic as well.)

Answer 3

Glass sponges
Demosponges
Calcareous sponges
Ctenophores
Placozoans
Cnidarians

Question 4

What are the characteristics of sponges?

Answer 4

Monoblastic, asymmetrical

Some specialized cells, but no true organs

They have spicules as skeletal elements

Mostly marine and filter feeders

Built around a water canal system

Made of choanocytes

Question 5

What are the three types of sponges

Answer 5

Glass sponges
Demosponges
Calcareous sponges

Question 6

Glass sponges and demosponges have spicules made of _______________.

Answer 6

silicon dioxide

Question 7

Calcareous sponges have spicules made of __________________.

Answer 7

calcium carbonate

Question 8

Describe the sponges water canals. How is water brought in? How does it help sponges eat food?

Answer 8

Water is brought into canals by beating choanocyte flagella. Choanocytes then capture food particles from this water.

Question 9

The body plan of sponges is an aggregation of _____________________________.

Answer 9

cells around a water canal system

Question 10

How do sponges reproduce?

Answer 10

Asexually through budding and fragmentation.

They can also reproduce sexually by releasing their gametes (sperm and egg) into the water, and the water carries them to one another.

Question 11

Can sponges self-fertilize?

Answer 11

Sponges cannot self-fertilize.

Question 12

What are Ctenophores also known as?

Answer 12

comb jellies

Question 13

What are some characteristics of ctenophores?

Answer 13

Radially symmetric, diplobastic

Two cell layers separated by a gelatinous mesoglea

Complete gut

Have ctenes

Question 14

Ctenophores may have been the earliest lineage to split from other animals. Which other group were ctenophores thought to be closely related to?

Answer 14

Cnidarians

Question 15

What are ctenes?

Answer 15

comb-like rows of cilia

Question 16

How do ctenophores move?

Answer 16

They move through the water by beating the cilia of their ctenes.

Question 17

How do ctenophores feed?

Answer 17

Ctenophores have feeding tentacles. These tentacles have cells that discharge an adhesive which can capture prey.

Question 18

What do ctenophores eat, and where do they live?

Answer 18

Ctenophores feed on planktonic organisms.

They are all marine.

Question 19

What are the characteristics of Placozoans?

Answer 19

4 distinct cell types, diploblastic

Their mature stage is asymmetrical

No mouth, gut, or nervous system

Question 20

Placozoans were once thought to be the sister group of all other animals, but this isn’t supported by _____________________.

Answer 20

phylogenetic analyses

Question 20

Placozoans aspects of structural simplicity may be secondarily derived. What does this imply?

Answer 20

Placozoan ancestors were more complex.

Question 20

What are the 3 groups of cnidarians?

Answer 20

Anthozoans (sea anemones, sea pens, and corals)

Scyphozoans (jellyfish; all marine)

Hydrozoans

Question 21

What are some common characteristics of cnidarians?

Answer 21

Mostly marine

Gut is blind, with one opening, also functions as a gastrovascular cavity

Incomplete gut; Two-staged life cycle

Tentacles have nematocysts

Question 21

What is the function of a gastrovascular cavity in cnidarians?

Answer 21

digestion, circulation, gas exchange, and as a hydrostatic skeleton

Question 22

Why is the cnidarian gut considered incomplete?

Answer 22

It only has one opening

Question 23

What are the two stages of the cnidarian life cycle?

Answer 23

Polyp and medusa

Question 24

How do polyps reproduce?

Answer 24

They produce male or female medusae asexually via budding of the mature polyp.

Question 25

How do medusa reproduce?

Answer 25

They produce polyps sexually.

Question 26

What does the fertilized egg of cnidarians develop into before becoming a polyp?

Answer 26

A free-swimming ciliated larva called a planula

Question 27

What is a planula?

Answer 27

A free-swimming ciliated larva

Question 28

How does a planula become a polyp?

Answer 28

The planula, or free-swimming ciliated larva, settles to the ocean floor and grows into a polyp.

Question 29

Cnidarian tentacles have nematocysts. What are nematocysts?

Answer 29

Specialized cells that inject toxins into prey organisms. These cells also have a stylet, or a barb, that keeps them anchored to the prey.

Question 30

Which organisms are considered anthozoans?

Answer 30

Sea anemones, sea pens, and corals.

Question 31

Name a characteristic of sea anemones that they don't share with all other anthozoans.

Answer 31

They are solitary

Question 32

Name a characteristic of sea pens that they don't share with all other anthozoans.

Answer 32

They are colonial with two types of polyps.

Question 33

What are the two types of polyps that sea pens have?

Answer 33

Primary polyps that anchor in the sediments Secondary feeding polyps that are produced by budding

Question 34

Name some characteristics of corals.

Answer 34

sessile; colonial polyps secrete matrix of organic molecules, aids in skeleton formation living polyps form on top of skeletal remains of other corals

Question 35

How do coral skeletons form?

Answer 35

Coral polyps secrete a matrix of organic molecules on which they deposit calcium carbonate, which forms a skeleton.

Question 36

How are coral reefs formed?

Answer 36

Living polyps form a layer on top of a growing mass of skeletal remains, which forms coral reefs and islands.

Question 37

Where do corals grow?

Answer 37

Shallow, nutrient-poor, tropical waters.

Question 38

How can corals survive in nutrient-poor and shallow waters?

Answer 38

Endosymbiotic dinoflagellates live within them. All they need for energy is sunlight.

Question 39

Why do coral reefs need clear surface water?

Answer 39

If the surface of the water is obstructed, the corals will not receive enough sunlight for their dinoflagellates to produce enough energy.

Question 40

Why are coral reefs threatened by rising CO2?

Answer 40

Increasing ocean temperatures and ocean acidification. (decreasing pH)

Question 41

Why is increasing ocean temperatures and ocean acidification bad for corals?

Answer 41

Ocean warming causes coral bleaching. Acidification can cause calcium carbonate skeletons of corals to dissolve.

Question 42

Why is excess nitrogen in runoff bad for corals?

Answer 42

It can lead to overgrowth of algae, which can suffocate corals—eutrophication

Question 43

Which organisms are considered scyphozoans?

Answer 43

jellyfish

Question 44

Name some characteristics of scyphozoans.

Answer 44

All marine Medusa stage dominates, individuals can be male or female Fertilized egg becomes planula

Question 45

What are some characteristics of hydrozoans?

Answer 45

Polyps usually dominate, but some have only medusae Mostly colonial, connected polyps share one gastrovascular cavity Some polyps specialized for feeding, other produce medusae

Question 46

How do the medusae in a hydrozoan develop?

Answer 46

Asexually within an enlarged secondary reproductive polyp.