COMPANA: Comparative Anatomy N01B
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
Comparative Anatomy
01 - Introduction to Comparative Vertebrate
Anatomy ● Incorporates different disciplines such as:
○ Zoology: Study of animals.
Lecture Outline ○ Physiology: Study of function.
I. What is Comparative Anatomy? ○ Histology: Study of tissues.
II. The Phylum Chordata: The Big Five ○ Genetics: Heredity and its effects on
III. The Craniate Body: General Plan variation and development.
IV. Craniate and Vertebrate Characteristics ○ Embryology: Processes from
fertilization to parturition.
What is Comparative Anatomy? ○ Evolution: Natural selection and
adaptation.
Comparative Anatomy
○ Paleontology: Historical record of past
● Studies the descriptive and functional
anatomy (fossils).
morphology of vertebrates:
○ Ecology: Organism-environment
○ Descriptive: Structure of vertebrates.
interactions.
○ Functional: Significance of the
○ Physics: Study of angles in different
structure.
bones.
● A study of evolution → phylogeny:
○ It can be considered as vertebrate
evolution.
● Confusion between morphology and
anatomy:
○ Morphology: Structural evolution.
○ Anatomy: Description of structures.
Anatomy vs. Morphology
Main Significance of Comparative Anatomy
● To comprehend the structural basis of
biology.
● To probe the ancient past and study
evolution.
● To develop appreciation of vertebrates.
● To develop dissection skills.
COMPANA: N01B 1
, COMPANA: Comparative Anatomy N01B
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
● To understand man’s place in the ○ Examples: Frog, Newt.
vertebrate world, without emphasis on man ● Birds:
himself. ○ Characteristics: Feathers, wings,
beaks; lay eggs; warm-blooded.
○ Examples: Wren, Swan.
● Mammals:
○ Characteristics: Fur or hair; feed young
with milk; warm-blooded.
○ Examples: Cow, Human.
Invertebrates
(Animals without a backbone)
● Protozoa:
○ Characteristics: Single-celled,
The Phylum Chordata: The Big Five microscopic organisms.
Conventional Zoology ● Flatworms:
○ Characteristics: Simple, soft bodies.
○ Examples: Tape worm, Flukes.
● Annelid Worms:
○ Characteristics: Segmented bodies.
○ Examples: Earthworm, Leech.
● Echinoderms:
○ Characteristics: Spiny sea creatures.
○ Examples: Starfish, Sea urchin.
● Coelenterates:
○ Characteristics: Soft bodies, stinging
cells.
○ Examples: Jellyfish, Sea anemone.
Vertebrates
● Molluscs:
(Animals with a backbone)
○ Characteristics: Soft bodies, most
● Reptiles:
have shells.
○ Characteristics: Dry, scaly skin; lay
○ Examples: Snails, Limpet.
eggs on land; cold-blooded.
● Arthropods:
○ Examples: Snake, Crocodile.
○ Subcategories:
● Fish:
■ Arachnids: Eight legs, no
○ Characteristics: Scales; gills for
antennae. Examples: Spider,
breathing; cold-blooded.
Scorpion.
○ Examples: Shark, Tuna.
■ Crustaceans: Mostly sea
● Amphibians:
creatures; two pairs of
○ Characteristics: Moist, slimy skin; lay
eggs in water; cold-blooded.
COMPANA: N01B 2
, COMPANA: Comparative Anatomy N01B
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
antennae. Examples: Crab, ○Found in Actinopterygii (ray-finned
Lobster. fish).
■ Insects: Six legs, wings, one 8. Lobed Fins
pair of antennae. Examples: ○ Found in Actinistia and Dipnoi.
Bee, Ladybird. 9. Limbs with Digits
■ Myriapods: Many legs and ○ Present in Amphibia (frogs).
body segments. Examples: 10. Amniotic Egg
Centipede, Millipede. ○ Present in Reptilia (e.g., lizards, birds).
11. Milk Production
○ Unique to Mammalia (e.g., mammals).
Groups Explained
● Chordates: Includes all descendants of the
common ancestor with a notochord.
● Craniates: Chordates with a head.
● Vertebrates: Craniates with a vertebral
column.
● Gnathostomes: Vertebrates with jaws.
● Osteichthyans: Bony vertebrates (e.g.,
ray-finned fishes).
● Lobe-Fins: Vertebrates with lobed fins.
● Tetrapods: Lobe-finned vertebrates with
Phylogenetic Tree of Chordates
limbs.
1. Ancestral Deuterostome
● Amniotes: Tetrapods with amniotic eggs.
○ Base of the phylogenetic tree.
2. Notochord
○ First major evolutionary feature.
○ Found in Cephalochordata and
Urochordata.
3. Common Ancestor of Chordates
○ Shared by all chordates.
4. Head Development
○ First seen in Myxini.
5. Vertebral Column
○ Found in Petromyzontida.
6. Jaws and Mineralized Skeleton
○ Found in Chondrichthyes (e.g.,
sharks).
7. Lungs or Lung Derivatives
Overview of Chordates Phylogeny
COMPANA: N01B 3
, COMPANA: Comparative Anatomy N01B
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
1. Chordata (Animals with a Notochord at ■ Features: Cartilaginous
Some Stage of Life) skeleton, placoid scales.
○ Features: Notochord, dorsal hollow ○ Osteichthyes (Bony Fishes):
nerve cord, pharyngeal slits, postanal ■ Actinopterygii: Ray-finned
tail, and endostyle. fishes.
■ Sarcopterygii: Lobe-finned
Subdivisions of Chordates fishes (e.g., coelacanths,
lungfishes).
1. Protochordata (Invertebrate Chordates)
○ Cephalochordata: Tetrapoda (Four-Limbed Vertebrates)
■ Examples: Lancelets.
■ Features: Simple chordate 1. Amphibia:
characteristics without a ○ Examples: Frogs, salamanders.
cranium. ○ Features: Limbs adapted for terrestrial
○ Urochordata: locomotion.
■ Examples: Tunicates. 2. Amniota (Amniotic Egg Development)
■ Features: Sessile adults with ○ Mammalia:
chordate features present in ■ Examples: Humans, cows.
larvae. ■ Features: Hair, mammary
2. Craniata (Chordates with a Cranium) glands.
○ Divided into Agnatha (jawless ○ Reptilia:
vertebrates) and Gnathostomata ■ Subgroups:
(jawed vertebrates). ■ Lepidosauria (Lizards,
snakes).
Key Lineages ■ Testudines (Turtles).
■ Crocodilia
1. Agnatha (Jawless Vertebrates) (Crocodiles).
○ Myxini: ■ Aves (Birds).
■ Examples: Hagfishes. ■ Features: Amniotic eggs, skull
■ Features: Slime glands, fenestrae, Beta-keratin in skin.
accessory hearts.
○ Petromyzontida:
■ Examples: Lampreys.
■ Features: Sucker-like oral disc,
7 pairs of gills.
2. Gnathostomata (Jawed Vertebrates)
○ Chondrichthyes:
■ Examples: Sharks, rays,
chimaeras.
COMPANA: N01B 4
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
Comparative Anatomy
01 - Introduction to Comparative Vertebrate
Anatomy ● Incorporates different disciplines such as:
○ Zoology: Study of animals.
Lecture Outline ○ Physiology: Study of function.
I. What is Comparative Anatomy? ○ Histology: Study of tissues.
II. The Phylum Chordata: The Big Five ○ Genetics: Heredity and its effects on
III. The Craniate Body: General Plan variation and development.
IV. Craniate and Vertebrate Characteristics ○ Embryology: Processes from
fertilization to parturition.
What is Comparative Anatomy? ○ Evolution: Natural selection and
adaptation.
Comparative Anatomy
○ Paleontology: Historical record of past
● Studies the descriptive and functional
anatomy (fossils).
morphology of vertebrates:
○ Ecology: Organism-environment
○ Descriptive: Structure of vertebrates.
interactions.
○ Functional: Significance of the
○ Physics: Study of angles in different
structure.
bones.
● A study of evolution → phylogeny:
○ It can be considered as vertebrate
evolution.
● Confusion between morphology and
anatomy:
○ Morphology: Structural evolution.
○ Anatomy: Description of structures.
Anatomy vs. Morphology
Main Significance of Comparative Anatomy
● To comprehend the structural basis of
biology.
● To probe the ancient past and study
evolution.
● To develop appreciation of vertebrates.
● To develop dissection skills.
COMPANA: N01B 1
, COMPANA: Comparative Anatomy N01B
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
● To understand man’s place in the ○ Examples: Frog, Newt.
vertebrate world, without emphasis on man ● Birds:
himself. ○ Characteristics: Feathers, wings,
beaks; lay eggs; warm-blooded.
○ Examples: Wren, Swan.
● Mammals:
○ Characteristics: Fur or hair; feed young
with milk; warm-blooded.
○ Examples: Cow, Human.
Invertebrates
(Animals without a backbone)
● Protozoa:
○ Characteristics: Single-celled,
The Phylum Chordata: The Big Five microscopic organisms.
Conventional Zoology ● Flatworms:
○ Characteristics: Simple, soft bodies.
○ Examples: Tape worm, Flukes.
● Annelid Worms:
○ Characteristics: Segmented bodies.
○ Examples: Earthworm, Leech.
● Echinoderms:
○ Characteristics: Spiny sea creatures.
○ Examples: Starfish, Sea urchin.
● Coelenterates:
○ Characteristics: Soft bodies, stinging
cells.
○ Examples: Jellyfish, Sea anemone.
Vertebrates
● Molluscs:
(Animals with a backbone)
○ Characteristics: Soft bodies, most
● Reptiles:
have shells.
○ Characteristics: Dry, scaly skin; lay
○ Examples: Snails, Limpet.
eggs on land; cold-blooded.
● Arthropods:
○ Examples: Snake, Crocodile.
○ Subcategories:
● Fish:
■ Arachnids: Eight legs, no
○ Characteristics: Scales; gills for
antennae. Examples: Spider,
breathing; cold-blooded.
Scorpion.
○ Examples: Shark, Tuna.
■ Crustaceans: Mostly sea
● Amphibians:
creatures; two pairs of
○ Characteristics: Moist, slimy skin; lay
eggs in water; cold-blooded.
COMPANA: N01B 2
, COMPANA: Comparative Anatomy N01B
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
antennae. Examples: Crab, ○Found in Actinopterygii (ray-finned
Lobster. fish).
■ Insects: Six legs, wings, one 8. Lobed Fins
pair of antennae. Examples: ○ Found in Actinistia and Dipnoi.
Bee, Ladybird. 9. Limbs with Digits
■ Myriapods: Many legs and ○ Present in Amphibia (frogs).
body segments. Examples: 10. Amniotic Egg
Centipede, Millipede. ○ Present in Reptilia (e.g., lizards, birds).
11. Milk Production
○ Unique to Mammalia (e.g., mammals).
Groups Explained
● Chordates: Includes all descendants of the
common ancestor with a notochord.
● Craniates: Chordates with a head.
● Vertebrates: Craniates with a vertebral
column.
● Gnathostomes: Vertebrates with jaws.
● Osteichthyans: Bony vertebrates (e.g.,
ray-finned fishes).
● Lobe-Fins: Vertebrates with lobed fins.
● Tetrapods: Lobe-finned vertebrates with
Phylogenetic Tree of Chordates
limbs.
1. Ancestral Deuterostome
● Amniotes: Tetrapods with amniotic eggs.
○ Base of the phylogenetic tree.
2. Notochord
○ First major evolutionary feature.
○ Found in Cephalochordata and
Urochordata.
3. Common Ancestor of Chordates
○ Shared by all chordates.
4. Head Development
○ First seen in Myxini.
5. Vertebral Column
○ Found in Petromyzontida.
6. Jaws and Mineralized Skeleton
○ Found in Chondrichthyes (e.g.,
sharks).
7. Lungs or Lung Derivatives
Overview of Chordates Phylogeny
COMPANA: N01B 3
, COMPANA: Comparative Anatomy N01B
2ND SEMESTER | ACADEMIC YEAR 2024 - 2025 | PROF. Michael Ples
1. Chordata (Animals with a Notochord at ■ Features: Cartilaginous
Some Stage of Life) skeleton, placoid scales.
○ Features: Notochord, dorsal hollow ○ Osteichthyes (Bony Fishes):
nerve cord, pharyngeal slits, postanal ■ Actinopterygii: Ray-finned
tail, and endostyle. fishes.
■ Sarcopterygii: Lobe-finned
Subdivisions of Chordates fishes (e.g., coelacanths,
lungfishes).
1. Protochordata (Invertebrate Chordates)
○ Cephalochordata: Tetrapoda (Four-Limbed Vertebrates)
■ Examples: Lancelets.
■ Features: Simple chordate 1. Amphibia:
characteristics without a ○ Examples: Frogs, salamanders.
cranium. ○ Features: Limbs adapted for terrestrial
○ Urochordata: locomotion.
■ Examples: Tunicates. 2. Amniota (Amniotic Egg Development)
■ Features: Sessile adults with ○ Mammalia:
chordate features present in ■ Examples: Humans, cows.
larvae. ■ Features: Hair, mammary
2. Craniata (Chordates with a Cranium) glands.
○ Divided into Agnatha (jawless ○ Reptilia:
vertebrates) and Gnathostomata ■ Subgroups:
(jawed vertebrates). ■ Lepidosauria (Lizards,
snakes).
Key Lineages ■ Testudines (Turtles).
■ Crocodilia
1. Agnatha (Jawless Vertebrates) (Crocodiles).
○ Myxini: ■ Aves (Birds).
■ Examples: Hagfishes. ■ Features: Amniotic eggs, skull
■ Features: Slime glands, fenestrae, Beta-keratin in skin.
accessory hearts.
○ Petromyzontida:
■ Examples: Lampreys.
■ Features: Sucker-like oral disc,
7 pairs of gills.
2. Gnathostomata (Jawed Vertebrates)
○ Chondrichthyes:
■ Examples: Sharks, rays,
chimaeras.
COMPANA: N01B 4
