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Comparative Anatomy & Physiology – Midterm Study Guide
Animal Characteristics & Taxonomy
1. What are some characteristics shared by all animals?
Multicellular, heterotrophic, eukaryotic, no cell walls, cells contain the protein collagen
2. Describe the basic types of body symmetry shown by animals.
Asymmetry: lack of symmetry
Radial symmetry: body parts arranged in circle around a central axis
Bilateral symmetry: left and right sides are mirror images of one another; can only divide in one plane to get
roughly equal halves
3. Compare the body plans of Acoelomate, Pseudocoelomate and Coelomate animals. Give examples of each type
of body plan.
Acoelomate: 3 layers, no body cavity; thin, solid body;
example =
flatworms
Pseudocoelomate: 3 layers, cavity between mesoderm and
endoderm;
example = roundworms
Coelomate: 4 layers, body cavity between 2 layers of
mesoderm;
example: earthworms, mollusks, arthropods,
4. Why is the coelom (body cavity) important?
A body cavity, or coelom, is a fluid-filled space that cushions and protects organs. It gives them space to grow
and change shape, and may act as a hydrostatic skeleton in some organisms.
5. Explain the difference between a protostome and a deuterostome.
Protostome: Blastopore becomes the mouth; all invertebrates except echinoderms are protostomes
Deuterostome: Blastopore becomes the anus and mouth develops later; all vertebrates and echinoderms are
deuterostomes
6. List, in order from largest to smallest, the categories used to classify organisms in biology.
Domain, kingdom, phylum, class, order, family, genus, species
7. What information can be found on a cladogram?
Evolutionary relationships among various organisms are shown. The closer two
organisms are on the diagram, the more closely related they are.
8. What language is used for scientific names? Why? How are scientific names
written?
Latin is often used because it is a universal language and is “dead” (not actively spoken any more, therefore
unchanging)
9. Compare and contrast the classification schemes used by Aristotle and Linnaeus.
Aristotle: classified organisms as plants or animals. Plants were divided according to size, and animals according
to their habitat.
Linnaeus: classified according to physical similarities and developed the classification taxa still used today. He
also developed the 2-part naming system of binomial nomenclature, which gives every organism a unique name
based on its genus and species.
Sponges, Cnidarians, Flatworms and Roundworms
10. What advantages do Multicellular organisms like sponges have over unicellular organisms?
Division of labor allows the cells of Multicellular organisms like sponges to specialize in certain functions thus
increasing their efficiency and allowing for greater complexity.
11. How do sponges feed?
Filter feeding – the collar cells use their flagella to create currents that draw water through the pore cells. Food
particles are filtered out and the waste water leaves the sponge through the Osculum.
12. What is a nematocyst?
A nematocyst is a stinging capsule found in members of the phylum Cnidaria. It helps Cnidarians like jellyfish and
sea anemones paralyze and capture prey.
13. Draw sketches of the polyp and medusa forms of jellyfish.
14. How do jellyfish reproduce?
(see diagram above)
Sexual phase: medusa release eggs/sperm, external fertilization takes place and larva settles to ocean floor.
Asexual phase: larva develops into a polyp that buds into tiny medusa.
15. What is a hermaphrodite?
An organism that contains both male and female reproductive organs.
16. Describe at least 3 ways in which flatworms and roundworms differ in body structure.
Flatworms are usually larger than roundworms
Flatworms are acoelomate, roundworms are pseudocoelomate
Flatworms have only 1 opening to their sac-like gut, roundworms have a tube-like digestive tract with 2 openings
17. Describe some examples of parasitic roundworms and flatworms.
Ascaris (round): eggs found in soil, accidentally swallowed due to poor hygiene. Worm larva travel to lungs, are
coughed up, and then move to the intestines. Very common worldwide.
Hookworm (round): larva in sandy soil burrow through feet and get into bloodstream, end up in intestines. Feed
off the hosts blood. May lead to anemia and/or weakness.
Pinworm (round): eggs transmitted through poor hygiene, worm lives in rectum and female crawls out of anus at
night to lay eggs. Causes intensely itchy bum.
Trichinella (round): larva found in uncooked pork, worms live in hosts muscles causing pain and weakness
Fluke (flat): Larva in contaminated water, burrow into skin of victim. Adult fluke lives in lungs, blood vessels or
liver. Very painful.
Tapeworms (flat): larva found in cysts in uncooked meat. Hatch in intestines and latch on. Grow verrrrry long.
Can cause diarrhea or malnutrition.
18. What is the difference between a primary and secondary host of a parasite?
Primary host: adult worms reside and release eggs into the environment
Secondary host: Larval worms burrow into tissues.
Mollusks and Segmented Worms
19. What is the mantle?
The mantle is a membrane that covers and protects the internal organs of Mollusks. In mollusks that have a
shell, it is the mantle that creates the shell by secreting calcium carbonate.
20. How do closed and open circulatory systems differ from one another?
Closed: All blood is contained within blood vessels, very efficient blood flow because oxygen-rich blood can be
directed to the body’s cells while oxygen-poor blood can be directed to the lungs or gills.
Open: Only some blood is contained within blood vessels; most blood is pumped into the empty spaces that
surround the organs within the body of the organism; less efficient because oxygen-rich and oxygen-poor blood
mix together
21. Why are the Cephalopods considered to be the most advanced mollusks?
They have an advanced nervous system with a large brain and excellent eyesight
They have a closed circulatory system with 3 hearts and can circulate blood efficiently
They can move quickly through jet propulsion when the squirt water out of their funnel and move backwards
quickly
They can use ink to confuse predators
22. Contrast how gastropods and bivalves feed.
Gatropods use a tongue-like scraping organ called a radula to feed on algae or plant material. Bivalves are filter
feeders that use mucus-covered gills to trap food particles from the water.
23. What is the most distinguishing characteristic of Annelids? Why is it important?
Annelids are segmented worms. Segmentation allows for more efficient movement (hydrostatic skeleton) and
allows certain body regions/segments to specialize in particular functions.
24. How do annelids reproduce?
Annelids are hermaphrodites that each contain male and female sex organs. They exchange sperm with one
another and use their clitellum to secrete a mucus cocoon around their fertilized eggs.
25. Describe three different classes of Annelids.
Earthworms live in the soil, important in Agriculture
Leeches are external parasites that live in streams, ponds, etc. They use suckers to attach to their host, inject
the host with an anesthetic and an anticoagulant that keeps blood from clotting. Some are used in medicine.
Polychaetes (Bristleworms) have many tiny legs called parapodia; live in aquatic environments
26. Explain why earthworms are beneficial to the soil.
Earthworms burrow through the soil, which loosens and aerates the soil. This allows plant roots to grow more
easily and also allows for more oxygen and water to penetrate the soil. Also, the earthworm’s waste, called
“castings”, help to enrich the soil with nutrients.
Arthropods & Echinoderms
27. What are the most distinguishing characteristics of arthropods?
Advantages: Good protection and support of body tissues, protects from drying out
Disadvantages: Cannot grow in size so the arthropod must molt the old skeleton and grow a new one underneath
the old one. They are vulnerable to predators during the molting period because their new exoskeleton takes a
while to harden, and their muscles cannot work well when the exoskeleton is soft.
28. What are the advantages and disadvantages of an exoskeleton?
Advantages: protection from predators, waterproof and resists internal water loss, most are lightweight
Disadvantages: Some are bulky and inflexible, must shed through the process of molting in order to grow.
Molting is dangerous because the muscles cannot work properly until the new exoskeleton hardens.
29. Compare and contrast complete and incomplete metamorphosis.
Complete: four stages—egg, larva, pupa, adult (butterflies, moths, beetles, bees)
Incomplete: three stages – egg. nymph, adult (grasshoppers, praying mantis)
Complete metamorphosis allows for less competition because the larva and adult eat different types of food.
30. How do arachnids and insects differ in terms of body structure?
Arachnids have 2 body regions, cephalothorax and abdomen, 4 pairs of walking legs, no antennae and no
mandibles
Insects typically have 3 body regions, head, thorax, abdomen, 3 pairs walking legs, 1 pair antennae, up to 2 pairs
of wings and mandibles for eating
31. What are 3 types of respiratory structures found in arthropods?
Tracheal tubes in insects – air enters via spiracles on the abdomen
Book lungs in arachnids
Gills in crustaceans
32. How do millipedes and centipedes differ in terms of body structure?
Millipedes have 2 pairs of legs per segment
Centipedes have 1 pair of legs per segment
33. Give some examples of crustaceans.
Crayfish, crabs, lobsters, shrimp, pill bugs
34. How do arthropods positively and negatively impact humans?
They help us by pollinating crops, they can be used as food or can produce food (like honey), they can help
control other pests through integrated pest management (like ladybugs are used to control aphid populations)
Some arthropods are vectors for disease (mosquitoes for malaria, zika, etc.) and insects can also destroy crops
35. Describe some feeding methods and some defense mechanisms of echinoderms.
Starfish are carnivores that eat other organisms by pushing their stomachs out of their mouths. Sea urchins eat
algae, and feather stars, brittle stars and sea cucumbers filter food particles out of the sand or water.
Echinoderms can defend themselves by giving off toxins, shedding an arm (and regrowing it later), poking
predators with their spines, or expelling internal organs to confuse predators.
36. What are some functions of the water vascular system?
Gas exchange, circulation, excretion, movement, feeding
Fishes and Amphibians
37. What four features are found in all chordates at some time in their development?
Notochord, dorsal hollow nerve cord, Postanal tail, pharyngeal slits
38. List some distinguishing characteristics of fishes.
Fins, scales and gills
39. Describe the three classes of fishes.
Jawless fishes: lampreys and hagfish; cartilage skeleton, long slender bodies and circular mouths; lampreys are
external parasites similar to leeches
Cartilaginous fishes: sharks, rays and skates; cartilage skeleton, sharks are top ocean predators
Bony fishes: largest group of fishes; bony skeleton and flexible fins, have a swim bladder and opeculum to cover
gills and help with breathing
40. Why was the development of jaws a significant evolutionary adaptation in fish?
It allowed fishes to take larger bites of food and become the top predators in their environment
41. What is the swim bladder? What types of fishes have one?
An inflatable organ that fills with gases and allows fish to control their depth
Found in bony fishes (not in sharks and other cartilaginous fishes)
42. What is the lateral line?
An organ that allows a fish to sense motion and vibration in the water
43. What does the name “amphibian” mean?
“Double/dual life”
44. Why are amphibians dependent on water?
Their thin skin must remain moist for respiration and they depend on water for reproduction so that their eggs do
not dry out and die
45. Describe the three orders of amphibians.
Frogs and toads, largest group of amphibians
Salamanders, resemble lizards but lack scales and claws
Caecilians – legless, burrowing amphibians found in the tropical rainforest
Amniotes
46. How are reptiles better adapted for a terrestrial existence than amphibians?
Reptile skin is dry and scaly to prevent water loss and
47. Why was the evolution of the amniotic egg so significant?
It allowed reptiles, birds and mammals to move to areas without water since they didn’t need to return to water
for reproduction. It also protected the egg from injury and drying out.
48. Describe some adaptations of birds that enable them to fly.
Feathers to provide lift, large 4-chambered heart to circulate blood efficiently, rapid metabolism, air sacs
attached to lungs for improved efficiency of gas exchange, hollow bones and large flight muscles attached to a
sterna keel bone.
49. Describe the structural and functional differences between down feathers and contour feathers.
Contour feathers contain interlocking components that create a smooth, solid surface for better airflow over the
surface. These feathers are found mostly on the wings and the surface of the bird’s body. Down feathers are
smaller and lack interlocking components. Instead, they are fluffy and soft, and trap air close to the bird’s body
in order to provide insulation.
50. What part(s) of a bird can give clues to its diet?
The beak shape and the foot shape are adapted to food sources. Example: hook shaped beak and sharp claws of
a hawk enable it to tear into the flesh of small animals
51. What is the difference between an endotherm and an ectotherm?
Endotherms are warm-blooded and control their body temperature internally, while ectotherms are cold-blooded
and have a body temperature that is influenced by their environment.
52. Describe how leg position in reptiles differs from leg position in amphibians and mammals.
Compared to amphibians, reptile limbs are better positioned slightly under their body and mammal limbs are
positioned completely under the body in order to better support body weight and allow for faster movement.
53. Describe the two circuits of blood vessels found in amniotes.
Pulmonary – blood flow between heart and lungs
Systemic – blood flow between heart and rest of the body
54. What are two main characteristics that all mammals have in common?
Hair/fur and mammary glands that produce milk and allow for extended care of young
55. What are some differences between placental(eutherian), marsupial and monotreme mammals?
Monotreme mammals lay eggs; very few living species (platypus and echidna)
Marsupial mammals have 2 developmental periods – first in uterus then in the pouch
Placental mammals develop in the mother’s uterus only; these are the most common type of mammal
Fetal Pig
56. How can you tell the difference between a male and female pig without dissection?
Male: urogenital opening just caudal to the umbilical cord and external scrotum to hold the testes
Female: Urogenital papilla and opening just under the tail
Both males and females have teats and an umbilical cord
57. Why is the fetal pig useful to study in anatomy and physiology?
Low cost, plentiful by-product of the pork industry
Very similar to humans
Can be used for human drug testing, surgical practice
Can also be used for human skin grafts and human heart valve replacements
58. What are some internal anatomical differences between the pig and man?
Female pigs have 2 uterine horns that expand the volume of the uterus and allow for multiple piglets in a litter.
Female humans do not have uterine horns.
The pig’s large intestine is shaped differently (spiral in pigs), and the pig lacks an appendix.
59. Name the organs that food would pass through as it travels the length of the digestive tract of the pig.
Mouth  Esophagus Stomach  Small intestine  Large intestine  Rectum  Anus
60. Name the organs that urine would flow through as it travels through the urinary organs of the pig.
Kidney  Ureter  Bladder  Urethra
Diagrams
The Sponge
A.
B.
C.
D.
E.
F.
Amoebocyte
Collar cell (choanocyte)
Epidermal cell
Osculum
Pore cell (porocyte)
Spicule
Osculum
Epidermal cell
Collar cell
Pore cell
Amoebocyte
Spicule
A.
B.
C.
D.
The Hydra
Basal disk
Bud
Mouth
Tentacle
Tentacle
Mouth
Bud
Basal disk
The Planarian
A.
B.
C.
D.
E.
Cilia
Eyespots
Gastrovascular cavity
Mouth
Pharynx
Eyespots
3. Mouth
Cilia
4. Pharynx
5. Gastrovascular cavity
The Clam
A.
B.
C.
D.
E.
F.
G.
H.
Anterior Adductor muscle
Digestive gland
Foot
Gills
Gonad
Intestine
Mantle
Stomach
Digestive gland
Stomach
Anterior adductor muscle
Mantle
Foot
Gills
Intestine
Gonad
The Squid
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
Anus
Arm
Eye
Gills
Gonad
Heart
Ink sac
Mantle
Pen
Stomach
Tentacle
Water jet/siphon/funnel
Gonad
Heart
Gills
Anus
Water jet/siphon/funnel
Cilia
Ink sac
Stomach
Pen
Esophagus
Eye
Arm
The Earthworm
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
Aortic arches
Brain
Crop
Dorsal blood vessel
Esophagus
Gizzard
Intestine
Mouth
Nephridia
Pharynx
Seminal vesicles
Ventral nerve cord
Gizzard
Esophagus
Intestine
Crop
Dorsal blood vessel
Aortic arches
Pharynx
Mouth
Ventral nerve cord
Brain
Seminal vesicles
Nephridia
The Grasshopper
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
Abdomen
Antenna
Compound eye
Head
Mouth
Ovipositor
Simple eye
Spiracle
Thorax
Walking leg
Head
Thorax
Antenna
Simple eye
Compound eye
Ovipositor
Mouth
Walking leg
Spiracle
Abdomen
The Crayfish
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
Abdomen
Antenna
Antennule
Carapace
Cephalothorax
Cheliped
Compound eye
Maxilliped
Swimmeret
Telson
Uropod
Walking leg
Antennule
Antenna
Compound eye
Cephalothorax
Carapace
Abdomen
Telson
Cheliped
Maxilliped
Walking legs
Swimmerets
Uropod
The Starfish
A.
B.
C.
D.
E.
F.
G.
H.
I.
Madreporite
Ampulla
Anus
Digestive gland
Gonad
Madreporite
Radial canal
Ring canal
Stomach
Tube foot
Digestive gland
Anus
Gonad
Ring canal
Radial canal
Stomach
Tube foot
Ampulla
The Fish Internal
The Fish External
A.
B.
C.
D.
E.
F.
G.
H.
I.
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
Anal fin
Caudal fin
Dorsal fin
Gills
Lateral line
Mouth
Operculum
Pectoral fin
Pelvic fin
Brain
Gallbladder
Gills
Gonad
Heart
Intestine
Kidney
Liver
Spinal cord
Stomach
Swim bladder
Urinary bladder
Dorsal fins
Lateral line
Mouth
Caudal fin
Operculum
Gills
Anal fin
Pectoral fin
Pelvic fin
Kidney
Swim bladder
Spinal cord
Brain
Gonad
Gills
Heart
Liver
Gallbladder
Urinary bladder
Intestine
Stomach
The Frog Internal
Anatomy
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
Anus
Cloaca
Esophagus
Gallbladder
Large intestine
Liver
Pancreas
Small intestine
Spleen
Stomach
Esophagus
Liver
Gallbladder
Stomach
Pancreas
Small intestine
Large intestine
Spleen
Cloaca
Anus
The Amniotic Egg
A.
B.
C.
D.
E.
F.
G.
Allantois
Amnion
Amniotic fluid
Blood vessels
Chorion
Embryo
Yolk sac
Amniotic fluid
Amnion
Embryo
Chorion
Allantois
Blood vessels
Yolk sac
A.
B.
C.
D.
E.
F.
G.
H.
I.
Word Bank
Diaphragm
Heart
Intestines
Larynx
Liver
Lung
Spleen
Thymus gland
Thyroid gland
Thymus gland
Larynx
Thyroid gland
Lung
Diaphragm
Liver
Heart
Spleen
Intestines
Liver
Gallbladder
Pancreas
Stomach
Spleen
Large intestine
Small intestine
Mesentery
Rectum
Anus
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
Word Bank
Anus
Gallbladder
Large intestine
Liver
Mesentery
Pancreas
Rectum
Small intestine
Spleen
Stomach