part b: short answer (7–12)
7. what are the two body forms found in cnidarians?
8. name one free-living flatworm and one parasitic flatworm.
9. how does segmentation benefit annelids?
10. what three main body parts are found in most mollusks?
11. give two reasons why arthropods are considered the most successful phylum.
12. list the four main characteristics shared by all chordates.
-6pts

Question

Accepted Answer

### Question 7
# Brief Explanations:
Cnidarians (like jellyfish, corals) have two body forms: polyp (sessile, cylindrical, e.g., coral) and medusa (free - swimming, bell - shaped, e.g., jellyfish).
# Answer:
The two body forms found in cnidarians are the polyp form and the medusa form.

### Question 8
# Brief Explanations:
Free - living flatworms include planarians (they live in freshwater, feed on small organisms). Parasitic flatworms include tapeworms (they live in the intestines of vertebrates, absorbing nutrients from the host) or flukes (like liver flukes, parasitic in the liver of hosts).
# Answer:
One free - living flatworm is Planarian, and one parasitic flatworm is Tapeworm (or Fluke).

### Question 9
# Brief Explanations:
Segmentation in annelids (like earthworms) allows for specialized functions in different segments (e.g., some segments for reproduction, some for movement). It also allows for redundancy (if one segment is damaged, others can still function) and more efficient movement as different segments can coordinate muscle contractions.
# Answer:
Segmentation benefits annelids by allowing for specialization of body regions (different segments can have different functions), redundancy (damage to one segment may not disable the whole organism), and more efficient, coordinated movement through the use of segment - specific muscle contractions.

### Question 10
# Brief Explanations:
Most mollusks (like snails, octopuses) have three main body parts: the mantle (secretes the shell in shelled mollusks), the foot (used for movement, like the muscular foot of a snail), and the visceral mass (contains internal organs like the digestive, reproductive systems).
# Answer:
The three main body parts found in most mollusks are the mantle, the foot, and the visceral mass.

### Question 11
# Brief Explanations:
Arthropods are successful because they have an exoskeleton (provides protection and support, prevents water loss), jointed appendages (allow for a wide range of movements and specialized functions like grasping, walking, swimming), a high level of segmentation (with specialized segments for different tasks), and a well - developed nervous system (allows for complex behaviors and responses to the environment). We can choose two of these reasons.
# Answer:
Two reasons why arthropods are considered the most successful phylum are: 1. They have an exoskeleton which provides protection, support, and helps prevent water loss. 2. They have jointed appendages that allow for a wide variety of movements and specialized functions (e.g., feeding, locomotion).

### Question 12
# Brief Explanations:
All chordates share four main characteristics at some stage of their life: a notochord (a flexible rod for support), a dorsal hollow nerve cord (develops into the central nervous system), pharyngeal slits or clefts (used for filter - feeding in some, or develop into other structures like gills or parts of the ear in others), and a post - anal tail (extends beyond the anus, used for movement in some species).
# Answer:
The four main characteristics shared by all chordates are: a notochord, a dorsal hollow nerve cord, pharyngeal slits (or clefts), and a post - anal tail.

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