Reading Guide Ch. 18 – Animal Phylums
Note – I’m giving you the Phylum name for some of these and the common name for others. Make
SURE you know all of these different phylums
Sponges
1. What is the phylum name for sponges? Phylum Porifera
2. What are suspension feeders?
Animals that collect food particles from water passed through some type of food-trapping equipment
3. What does the term sessile mean?
Anchored in place (do not move)
4. Why are sponges considered to be the simplest phylum in the animal kingdom?
Not made of tissues
Phylum Cnidarian
1. Provide examples of organisms in this phylum. (We will observe hydra’s under microscopes later
in the year.)
Hydras, jellyfish, sea anemones, and corals
2. What type of symmetry do they have and how many tissue layers?
Radial symmetry (2 tissue layers)
3. How do organisms in this phylum acquire food?
Use tentacles to capture small animals and protists and to push the prey into their mouths
4. What is a gastrovascular cavity, and how does it work?
Mouth is the only opening in the body, so undigested food and other wastes exit through it (what
goes in comes out the same way). It also bathes internal cells like a vascular system providing them
with nutrients. Also acts as a hydrostatic skeleton
5. What is a cnidocyte (the structure from which the phylum gets its name)?
Stinging cells
6. How do corals form?
Secrete a hard external skeleton; Each generation builds on top of the skeletons of previous
generations, constructing characteristic shapes of “rocks” we call coral
**Organisms in the phylum Cnidaria do not have a brain, but rather have a dense collection of nerves
called a nerve net
Flatworms
1.
2.
3.
4.
What is the phylum name for flatworms? Phylum Platyhelminthes
What range of size are flatworms found in? 1 mm to 20 m
What type of digestive system do they have? Gastrovascular Cavity
What is a planarian? (We will observe this species later on in the year under microscopes.)
Free-living (not parasitic) flatworms
5. What is a fluke?
Flatworms that live as parasites in other animals
6. What is a tapeworm?
Parasitic flatworm that inhabit digestive tract of vertebrates (including humans)
a. How can dogs become infected with tapeworms?
Prey species (such as rabbit) can become infected by eating grass contaminated with
tapeworm eggs (grass has tapeworm eggs because tapeworms live in digestive tract).
Dog then eats this prey animal and becomes infested
b. How can humans become infected with tapeworms?
Eating undercooked beef, pork, or fish infect with tapeworm larvae (can reach up to 2
m human intestine)
Phylum Nematode
1. What is the common name for nematodes? Roundworms
2. What is the purpose of a nematode’s cuticle?
Cuticle is tough, nonliving material that covers the body and prevents nematode from drying out (can
also protect parasitic nematodes from host’s digestive system)
3. What is different about the nematodes’ digestive system from the digestive system of the other
phylums discussed thus far?
It has a complete digestive tract (mouth and anus) instead of gastrovascular cavity (one hole for
entering and exiting food)
4. Heartworms, commonly found in dogs, are a species in this phylum. How are they transmitted?
Spread by mosquitoes, which pick up heartworm eggs in the blood of an infected host and transmit
them when sucking the blood of another animal
Phylum Mollusca
1. Provide examples of organisms in this phylum.
Snails, slugs, oysters, clams, octopi, and squids
2. Most organisms in this phylum are soft bodied. What do most possess for protection?
Shell
3. What are the 3 main body parts of molluscs?
1) Foot – functions in locomotion, 2) Visceral mass – contains internal organs, 3) mantle – fold of
tissue that drapes over visceral mass and secretes a shell in molluscs such as clams and snails
4. What is the function of the radula?
Scrape up food into the mouth
5. How do molluscs distribute nutrients and oxygen through their body (a system that is not found
in flatworms or nematodes)?
Circulatory system – organ system that pumps blood and distributes nutrients and oxygen throughout
the body
Specifically, Open Circulatory System
6. Give a brief description for each of the 3 main classes of molluscs and tell what organisms make
up each class.
a. Gastropod –
Largest group; found in fresh water, salt water, and terrestrial environments (only molluscs on lands);
have single, spiraled shell for protection; distinct head with eyes at tips of tentacles
Snails, slugs
b. Bivalves –
Clams, oysters, mussels, and scallops
Shells divided into two halves that are hinged together; suspension feeders – mucus coated gills trap
food particles suspended in water and cilia sweep particles into the mouth; sedentary, living in sand
or mud (may use muscular foot for digging or anchoring)
c. Cephalopods –
Fast, agile predators (which is why they don’t have a shell); beak-like jaws and a radula to crush or rip
prey apart; have long tentacles for catching and holding prey; large brains and sophisticated sense
organs; very complex eyes
Squids and octopuses
*This phylum has the most MARINE organisms
Phylum Annelida
1. What is segmentation and why is it beneficial?
Subdivision of the body along its length into a series of repeated parts (segments)
Allows for greater flexibility and mobility
2. What is the most common organism in the Phylum Annelida?
Earthworm
3. What are the 3 main groups of annelids?
Earthworms, leeches, and polychaetes
4. Explain the difference in how an open vs. closed circulatory system functions (and give examples
of which phylums have each type).
Open – blood is pumped through vessels that open into body cavities where organs are bathed
directly in blood
Closed (which annelids and vertebrates have) – blood remains enclosed in vessels as it distributes
nutrients and oxygen throughout the body
5. How is an earthworm’s heart unique?
Not really a “heart” – simply an enlarged region of the dorsal blood vessel plus five pairs of segmental
vessels near the anterior end
6. How do earthworms move (include the function of the bristles in your description).
Coordinating contraction of longitudinal and circular muscles (working against coelomic fluid that acts
as a hydrostatic skeleton); bristles provide traction for burrowing
7. Are earthworms male or female? Both (hermaphrodite)
8. How do earthworms gain nutrients?
Eating their way through soil, extracting nutrients as soil passes through digestive tube
9. How are earthworms beneficial to humans?
Castings (feces) and aeration provided improves the soil
10. Explain the process by which blood sucking leeches feed.
Use razor-like jaws to slit animal then sucks the blood (host doesn’t feel it because leech secretes an
anesthetic as well as anticoagulant into wound)
Phylum Arthropoda
1. Provide examples of organisms in this phylum.
Crayfish, lobsters, crabs, barnacles, spiders, ticks, and insects
2. Why is this considered the most successful animal phylum?
Most species diversity, geographic distribution, and sheer numbers
3. What are 3 traits that lead to the great success of this phylum?
Segmentation, hard exoskeleton, and jointed appendages
4. What is an exoskeleton?
External skeleton that protects the animal and provides points of attachment for muscles that move
the appendages
5. What is molting?
Shedding old exoskeleton and secreting a large one as an arthropod grows
6. What are the 3 body sections all arthopods are divided into?
Head, thorax, abdomen (although in arachnids the head and the thorax are fused so they are only
have 2 segments)
7. What type of circulatory system do arthropods have? Open circulatory system
8. Arthropods are divided into 4 major lineages. List these 4 lineages and provide the major
organisms that make up each of these lineages.
1) Chelicerates (chele meaning claw) – scorpions, spiders, ticks, and mites (arachnids)
2) Myriapoda - Millipedes and Centipedes
3) Crustaceans – lobsters, crayfish, crabs, shrimps, barnacles
4) Insects - Grasshoppers, butterflies, beetles, flies, bees, moths
9. What are the differences and centipedes and millipedes?
Millipedes eat decaying plant matter and centipedes are carnivores with a pair of poison claws
Insects are the most diverse class of animals in the world (comprising over 70% of all animal species).
They are in the arthropoda phylum, and we will focus on them here.
10. Distinguish between complete and incomplete metamorphosis.
Complete – change from larval to adult with formation of pupa for transition
Incomplete – transition from larval to adult occurs through multiple molts but no pupa
11. During complete metamorphosis, what is each stage (larvae and adult) specialized for?
Larval – eating and growing, Adult – reproduction and dispersal
12. Why do genetic mutations generally only affect one body section of an insect (an example being
how the grasshopper evolved hind legs specialized for jumping without affecting the other
legs)?
Insects have a modular body plan, each embryonic segment is a separate building block that develops
independently of the other segments
13. What kinds of eating are insect mouthparts specialized for?
Chewing for plant material (grasshoppers), biting and tearing prey (praying mantis), lapping up fluids
(houseflies), or piercing and sucking fluids (mosquitoes)
14. How many pairs of legs do most insects have (which is different than the characteristic 8 legs of
arachnids)? 6 legs
15. Insects are the only arthropods that can ___fly__________?
16. How are insect wings different than those of birds and bats?
Insect wings are extensions of the cuticle so they can fly without sacrificing any legs (so movement on
land still effective) whereas bird and bat wings are modified limbs so they only have a single pair of
walking legs and are clumsy on land
*Note: This phylum by far has the most species / organisms (most because the class Insecta is in this
phylum)
** Note: To distinguish between insects and arachnids, consider a) number of legs, b) presence of
antennae, and c) presence of wings
Phylum Echinodermata
1. Provide examples of organisms that make up this phylum.
Sea stars, sand dollars, and sea urchins
2. What type of symmetry do they portray as larvae and as adults?
Bilateral as larval and radial as adults
3. What is an endoskeleton?
Hard calcium-containing plates that form the internal skeleton under the thin skin of the animal
4. Describe the water vascular system.
Network of water-filled canals that branch into extensions called tube feet
5. How does a sea star feed?
Grips oyster or clam with its tube feet and positions its mouth next to the narrow opening between
the two valves of the shell. The sea star then turns its stomach inside out, pushing it through its
mouth and into the opening of the mollusc’s shell. The sea star’s stomach proceeds to digest the soft
parts of the mollusk inside the mollusc’s shell
Phylum Chordata
1. What physical characteristic do almost all organisms in this phylum separates them from all of
the phylums discussed thus far? (In other words, why are the organisms in this phylum called
vertebrates while all other phylums are invertebrates?)
Backbone
2. What are the 4 features that are distinctive features used to identify members of the phylum
Chordata?
1) Dorsal, hollow nerve cord (spinal cord)
2) notochord, a flexible, supportive, longitudinal rod located between the digestive tract and the
nerve cord (backbone)
3) pharyngeal slits in the pharynx, the region just behind the mouth
4) Muscular post-anal tail