The Embryo Room
What do the pharyngeal (gill) slits found in human, bird, and fish embryos suggest?
A) All these animals can breathe underwater.
B) They all share a common aquatic ancestor.
C) These structures will eventually become wings.
D) It is a random coincidence of development.
B) They all share a common aquatic ancestor.
Why are the wings of a dragonfly and the wings of a hawk considered analogous?
A) They both have the same internal bone structure.
B) They evolved from a common ancestor that had wings.
C) They serve the same function (flight) but are built differently.
D) They are both made of feathers.
C) They serve the same function (flight) but are built differently.
The "one bone, two bones, many bones" pattern in vertebrate limbs is evidence for:
Analogous structures
Descent with modification
Spontaneous generation
Convergent evolution
Descent with modification
A scientist finds a non-functional pelvic bone inside a whale. This is called a:
Homologous structure
Analogous structure
Vestigial structure
Embryonic structure
Vestigial structure
Scientists study both adult skeletons (comparative anatomy) and growing embryos (embryology). Why do they look at both to figure out how closely related two species are?
C) Together, they provide multiple independent lines of evidence for common ancestry.
Which species would look similar for the longest period of time during embryonic development?
A human and a fruit fly
A snake and a mouse
A cat and a dog
A fish and a bird
A cat and a dog
The streamlined body shapes of sharks (fish) and dolphins (mammals) are the result of:
Divergent Evolution
Convergent Evolution
Artificial Selection
Shared Skeletal Structures
Convergent Evolution
Which pair represents a homologous relationship?
A butterfly wing and a bat wing
A human arm and a whale flipper
A shark fin and a dolphin fin
An insect leg and a horse leg
A human arm and a whale flipper
Why do vestigial structures like the human tailbone still exist?
A) They are preparing to grow into new limbs.
B) They are still essential for survival.
C) They were inherited from an ancestor and haven't fully disappeared.
D) They are caused by mutations in the environment.
C. They were inherited from an ancestor and haven't fully disappeared.
When we find structural patterns that are shared across different species—like similar bone layouts and matching embryo stages—what is the ultimate "big picture" conclusion?
B) Earth’s biodiversity is unified through a history of shared descent.
The Brain Blueprint: In early development, the embryos of all vertebrates start with a "three-bulge" brain. What does this suggest about the origin of the vertebrate brain?
A. It evolved from a single common ancestor.
B. They will develop as the main structure of the body.
C. Every organism descended from various ancestors.
A. It evolved from a single common ancestor.
The Octopus Eye: The eyes of a human and an octopus are structurally similar and both used for sight, but they evolved completely independently.
Are they homologous or analogous?
Analogous
The Giraffe's Neck: A giraffe has 7 neck vertebrae, and a human also has 7 neck vertebrae, despite the massive difference in length.
Is this homology or analogy?
Homology
Name a human body part that is considered a vestigial structure.
Because an organism's genes determine its physical structure, analogous structures provide evidence that two organisms are closely related.
True or False.
False.
Homologous structures provide evidence that two organisms are closely related.
A structure in the early embryo that develops into parts of the jaw, ear, and neck. (Correct spellings only)
Pharyngeal arch/slit
Succulent Survival: Cacti in America and Euphorbia in Africa both have thick, water-storing stems and spines, but they are not closely related.
This is an example of what? Divergent Evolution or Convergent Evolution
Convergent Evolution
Plant Parts: The spine of a cactus and the leaf of a maple tree look different and do different jobs, but both developed from the same ancestral leaf tissue.
What type of structures are these? Homologous or analogous structure
Homologous Structures
What is a vestigial structure?
A leftover part with no clear purpose.
If two animal species look completely different as adults, they cannot share a common ancestor, even if their embryos look identical.
True or false.
False.
In land animals, what do embryonic pharyngeal arches become?
Jaws or inner ear bones
The Shell Game: Both armadillos (mammals) and turtles (reptiles) evolved hard protective shells.
Is this a sign of a recent common ancestor or similar environmental pressure?
Similar environmental pressure
Bone ID: In the "one bone, two bones, many bones" pattern, what is the name of the "one bone" found in the upper arm of all tetrapods?
Ulna, Humerus, Radius, or Carpals
Humerus
Boa constrictor snakes have tiny, useless hind leg bones buried inside their muscles. What does this tell us about snake history?
Snake ancestors had legs.
What scientific term describes anatomical features—such as the similar arm bone layouts in humans, bats, and whales—that are shared by different species because they were inherited from a common ancestor?
Homologous Structures