Regents Biology

But don’t be fooled by these…

▪ Analogous structures

◆ look similar

▪ on the outside

◆ same function

◆ different structure & development

▪ on the inside

◆ different origin

◆ no evolutionary relationship

Solving a similar problem with a similar solution

How is a

bird

like a bug?

What are Analogous Structures?

• Structures that are made differently, but have the same function.

• Examples: Wings of a bug, bird, and a butterfly.

Regents Biology

Analogous structures

▪ Dolphins: aquatic mammal
▪ Fish: aquatic vertebrate

◆ both adapted to

life in the sea

◆ not closely related

Watch the

tail!

Regents Biology

Vestigial organs

▪ Structures that are reduced in size and

have lost all or most of their original
function.

Why would whales have
pelvis & leg bones if they
were always sea creatures?

Because

they

used to
walk on

land!

Regents Biology

Vestigial organs

▪ Structures on modern animals that have

no function

◆ remains of structures that were functional

in ancestors

◆ evidence of change over time

▪ some snakes & whales have pelvis bones &

leg bones of walking ancestors

▪ eyes on blind

cave fish

▪ human tail bone &

appendix

Regents Biology

3. Comparative embryology

▪ Animals with backbones develop similarly

▪ During development, all vertebrates have a tail and paired
pharyngeal pouches.

-- In fish and amphibian larvae, the pouches become gills.
-- In humans, the pouches becomes the middle ear; tonsils, & glands

all vertebrate embryos have a “gill
pouch” at one stage of development

Regents Biology

4. Molecular record

1
0

0

2
0

3
0

4
0

5
0

6
0

7
0

8
0

9
0

10
0

11
0

12
0

Lampre

y

Fro
g

Bir
d

Do
g

Macaqu

e

Huma

n

3
2

8

4
5

6
7

12
5

Comparing DNA & protein structure

◆ everyone uses the same genetic code!

▪ DNA sequences show how closely related 2

organisms are to each other.

▪ compare common genes
▪ compare common proteins

number of amino acids
different from human
hemoglobin

Regents Biology

Building “family” trees

Closely related species are branches on the tree —
coming from a common ancestor

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5. Biogeography

▪ the study of the geographical distribution of living things
▪ The distribution of fossils show that the continents were

once joined together.

▪ Animals living in the same area evolve to have similar

traits.

Regents Biology