GENERAL BIOLOGY 2
QUARTER 3 - WEEK 4
Evidences of Evolution
Activity 1. Related or Not?
Fossils
1. What is the biggest change in skull anatomy that occurred from the dawn horse to the
modern horse?
- The size of the skull is dramatically larger in the modern horse.
2. What is the biggest change in leg anatomy that occurred from the dawn horse to the
modern horse?
- Aside from having much longer legs, the modern horse has grown hooves in place
of hand and foot bones.
3. Give similarities of the skull that might lead to the conclusion that these are all related
species.
- The tops of the skulls all have a ridge that extends. The overall shape stays
consistent. A set of flattened teeth can be found on each skull.
Embryology
Species
Human
Chicken
Rabbit
Tortoise
Salamander
Fish
Species
Human
Chicken
Rabbit
Tortoise
Salamander
Fish
Embryo
F
D
E
C
B
A
Your thinking.
I think I categorized which
embryo belongs to which
organism.
Anatomical Changes From Early to Late Stages
Developed limbs, defined features in face, neck, and ears, loss of tail,
tiny fingers present
Beak is developed, tail is shorter, wings and legs are developed, and
the head is large.
Tail is gone, limbs are developed, and the ears and mouth have detailed
features.
Shell developed, limbs developed, tail became thinner, belly became
larger, tail became longer, and beak became longer.
Gills, a tail, and a large underbelly are all present.
Fins, gills, tail, and scales have all developed.
1. Look again at the six embryos in their earliest stages. Describe the patterns you see. What
physical similarities exist between each of the embryos?
- The basic shape is the same, with circular spots (eyes) and underbelly, tails, tiny
bumps on the underside, and a hole for the ear.
2. Does this suggest an evolutionary relationship? Explain how these embryos can be used as
evidence of a common ancestor between each of these six organisms.
- Observation of embryo development demonstrates that the embryos appear to be
nearly identical during relevant phases of early development. Gill pouches, for example, are
present in all vertebrate embryos at various stages. In fish, the pouches eventually become the
gill apparatus. In evolving vertebrates without gills, the gill pouches develop further and
become structures linked with the head and neck. Furthermore, tails are present in all early
embryo development, which persist in some species but regress in humans throughout later
stages of development. As a result, an animal's individual development is divided into stages
that give a broad picture of the stages of evolution or phylogeny of the organisms to which it
originally belonged.
Comparative Anatomy
Animal
Human
Whale
Cat
Bat
Bird
Crocodile
Primary Functions
Using tools, picking up and holding objects
Swimming
Running, walking, jumping
Flying, flapping wings
Walking, hopping
Swimming, walking, crawling
Compare the skeletal structure of each limb to the human arm. Relate the differences you see
in form to the differences in function.
Animal
Comparison to Human Arm in Comparison to Human Arm in
Form
Function
Whale
Whale has a much shorter and
Whale fin needs to be longer to help in
thicker humerus, radius, and ulna. movement through water. Thumbs are
Much longer metacarpals.
not necessary, as they don’t need to
pick up and grasp things.
Cat
The humerus is curved, the ulna
Cats move by jumping and running,
and radius are shorter and thinner, and they're smaller for agility and
and the metacarpals and phalanges balance on small ledges. They don't
are smaller.
have thumbs for grabbing, instead
relying on claws and teeth.
Bat
Humerus, ulna, and radius are
The bones are smaller to reduce
thinner; carpals are smaller;
weight in flight, while the metacarpals
metacarpals and phalanges are
and phalanges are long to extend the
longer and thinner.
wings.
Bird
Humerus, ulna, and radius are
Bones are thinner for flight, more
slightly shorter; metacarpals are
aerodynamic and light
fused together, and phalanges are
fewer but more pointed.
Crocodile
The humerus, ulna, and radius are Long metacarpals for swimming and
shorter and thicker, the carpals are thicker legs to support heavy weight
larger, and the phalanges are
pointed.
Compare the anatomy of the butterfly and bird wing below.
1. What is the function of each of these structures?
- The wings are designed for gliding and flying.
2. How are they different in form? Give specific differences.
- A butterfly has two pairs of wings, whereas a bird's wing has many feathers. A
bird's wing has bones, but a butterfly's wing has none.
Compare the overall body structure of the cave fish and the minnow below.
1. What is the biggest, most obvious difference between the body structure of these two fish?
- The cave fish lack eyes and scales, unlike the minnow where it has eyes and scales.
2. Assume the two fish came from the same original ancestor. Why might the cave fish have
evolved without eyesight?
- There is no requirement for sight because it is always in a dark environment. This
adaptation would not have provided a benefit, hence it was not selected.
3. What kind of sensory adaptation would you hypothesize the cave fish has to allow it to
navigate in a cave, including catching and eating food?
- Sensitivity to motion, vibration, electrical impulses, sound, smell, and/or taste
Homologous structures
1. Give an example of a homologous structure from this activity:
- Crocodile leg, human arm
- Human and cat front legs
Analogous structures
2. Give an example of an analogous structure from this activity:
- Butterfly and bird wing or bat wing
Vestigial structures
3. Give an example of a vestigial structure from this activity:
- Thumb of a whale fin
4. Below are some vestigial structures found in humans. For each, hypothesize what its
function may have been.
Structure
Wisdom teeth
Appendix
Muscles for
moving the ear
Body hair
Little toe
Tail bone
Possible function?
Extra grinding ability for vegetation
Store good bacteria to fight infections or digest cellulose like the caecum
in rabbits
Better hearing by changing direction of ears
Keeping warm, preventing germs from reaching mucosal membranes, and
trapping pheromones and oil on the body
Balance/clinging on rocks/trees
Balance, rear stabilizing limb
5. How are vestigial structures an example of evidence of evolution?
- Structures that are helpful in other species are often similar to vestigial organs.
Humans have a vestigial tailbone that is similar to other animals' functional tails. Vestigial
structures might also be considered as evolutionary evidence since creatures with vestigial
features are likely to share a common ancestor with organisms with functioning homologous
structures.
Molecular Biology
Animal
Horse
Chicken
Tuna
Frog
Number of Amino Acid
Differences Compared
to Human Cytochrome
C
5
7
11
9
Animal
Number of Amino Acid
Differences Compared to
Human Cytochrome C
Shark
Turtle
Monkey
Rabbit
14
8
1
4
1. Based on the Cytochrome C data, which organism is most closely related to humans?
- Monkey
2. Do any of the organisms have the same number of differences from human Cytochrome C?
In situations like this, how would you decide which is more closely related to humans?
- None of the organisms have the same number of difference from the human
Cytochrome C. In circumstances like this, we can determine which organism is more closely
linked to humans by comparing anatomy structures, evolutionary tree, or comparing them to
human genes using another protein.
Charles Darwin published his book On the Origin of Species in 1859. Of the different
types of evidence that you have examined, which do you think he relied upon the most,
and why?
- To link species, Darwin relied on their anatomies being similar. He also had some
fossil evidence of minor changes in the species' body structure over time, which often resulted
in vestigial structures.