2. PRELIMINARIES
C. HOUSE RULES
1. Listen carefully
2. Raise your right hand whenever
you want to recite.
3. Unnecessary noise is not allowed.
4. Submit your output on time.
6. “DECODE ME”
Activity1
DIRECTION: Divide the class into two groups.
Each group will form a circle to communicate with
each other. On the board/screen are numbers.
Decode the given numbers to their corresponding
letters of the alphabet.
9. UNLOCKING OF DIFFICULTIES
Another evidence of evolution is from comparative anatomy
structures that can be homologous and analogous.
1.The divergent evolution proposed that homologous structures
that developed from a common ancestor may have different
functions, such as bat wings, and forelimbs of dogs and
whales.
2.The convergent evolution suggests that analogous structures
of organisms of different ancestors have similar functions
such as butterfly wings and bird wings.
10.
11. AHA! HOMOLOGOUS! ANALOGOUS!
Activity 2
Objectives:
1.Distinguish homologous and analogous structures.
2.Explain the relevance of comparative anatomy as
evidence of evolution.
Materials:
a.Pen
b.Paper
12. Direction:
1.Write in the space provided H if the structures below are homologous and A if they are
analogous.
13. QUESTIONS:
Q1. Can you say that humans, whales, and
bats might belong to a common ancestral
group? Explain why.
Q2. Give other examples of homologous
and analogous structures.
14.
15. Evidence for
Evolution
Many genetic, anatomical,
physiological, archaeological and
geographical discoveries have been
made that support the theory of
evolution; these include:
• Comparative anatomy
• Molecular homogeny
• The fossil record
16. Comparing the anatomy of present day, transitional and ancestral
organisms with each other, in addition to embryological or
intermediate forms, gives insight into the similarities and
differences between various body structures.
Both internal and external form can be observed and associated
with function between organisms to identify the degree of
evolutionary relatedness.
Depending on what is being compared, structures can be referred
to as being:
Comparative Anatomy
• Homologous • Analogous
17. These structures look different externally, however,
actually link two species to a common ancestor. The
structures are essentially the same but differ in
shape, size etc. These differences can be attributed
to how the structure has adapted to suit unique
environmental selection pressures to aid survival.
Same Origin but different functions
Examples include:
Homologous
Structures
• The pentadactyl limb
• Vertebrate hearts
• Insect mouthparts
• The mollusc foot
18. The pentadactyl limb is one of the most
well-known examples of a homologous
structure. It consists of the bones making
up the appendages of tetrapod
vertebrates and often refers to the ‘arm’,
although can also refer to the ‘leg’ as well.
Different bones will vary in size, thickness
and orientation dependent on what the
specific species use this limb for -
swimming, grasping, climbing, digging etc.
Homologous Structures
The Pentadactyl Limb
Scapula
Phalanges
Carpals
Ulna
Radius
Humerus
20. These may mislead you to think two species are closely related as
the structures appear similar in form, although on closer inspection
it can be found that the structures however similar in appearance,
are not a result of recent common ancestry.
Similarities in shape, size, colour etc can be attributed to the
organisms experiencing similar environmental pressures therefore
requiring similar structures to aid survival.
Analogous structure-similar functions but different origin
Analogous Structures
• Wings of mammals, birds and insects
• Dorsal fins of fish and marine mammals
• Gliding ‘wings’ of placental and marsupial mammals
Examples include:
21. Basis Of Comparison Homologous
Structure
Analogous Structure
Origin Have the same
ancestor
Have different
ancestor
Function Modified to perform
different functions
Adapted to similar
functions
Example Forelimbs of bats
and whales
Wings of birds, bats
and butterflies
Comparison Between Analogous and Homologous
23. QUESTIONS:
1. What is the difference between
homologous and analogous
structures?
2. What is the importance of
comparative anatomy in the study
of evolution?
25. Get ¼ piece of paper.
Answer the following
questions. Write the letter
of the correct answer.
26. 1.Which pair of animals shows a correct
example of homologous structures?
a.Wings of butterfly and wings of bat
b.Flipper of whale and forelimb of cat.
c.Fingers of human and arm of starfish.
d.Tongue of frog and proboscis of
mosquito.
27. 2. Which of the following statements about
analogous is true?
a.They perform similar functions
b.They have similar anatomy
c.They indicate strong evolutionary
relationship
d.None of the above
28. 3. Propose a reason why scientists agree that a
human and a bat share a common ancestor.
a.The human arm and a bat's wings are homologous
structures that share similar anatomical structures.
b.The human arm and a bat's wings are analogous
structures that share similar anatomical structures.
c.The human arm and a bat's wings share similar
functions and anatomical features.
d.The human arm and a bat's wings do not provide
evidence of common ancestry.
29. 4. Explain why species have homologous
structures.
a. They share a common ancestor.
b. They contain remnants of their ancient
ancestors.
c. They do not share a common ancestor.
d. They share a similar function but have
a different anatomical structure.
30. 5. Describe what the arm of a human and the
wing of a bat provide an example of.
a. Homologous Structures
b. Vestigial Structures
c. Heterogenous Structures
d. Analogous Structures
