Form & FuncT oN
i
What is a skeleton?
A skeleton consists of the bones that make up the
framework of a body.
Exercise directions
In this exercise, we will be looking at the form and
function of different skeletons and how they suit
the lifestyle of those animals.
Let’s try a few examples.
Making Observations:
observations
Take a few minutes
to make some
observations about
the form of this
animal.
For example, you might say….
example
Short arms with fingerlike appendages
Long, thick-boned tail
that reaches to the ground
Elongated rear limbs with shorter
bones connecting them to the
pelvis.
Large feet
Making Inferences:
inferences
To make an inference means to
draw conclusions from your
observations.
What are some functions of these
structures??
Some questions you
might start with are…
What are the arms
used for?
Why is the tail so
long and sturdy?
How might long, skinny legs help it move?
Why are the feet so large?
Can you guess the
animal?
Kangaroo!
How does form relate to function?
Click on a part of
the animal to find
out
Adaptations
An adaptation is a characteristic that helps
an organism survive and reproduce in its
environment.
Can you identify a structure that serves as an
adaptation for a kangaroo?
Let’s try another example…
Make some
observations about
this skeleton
Observations:
-Hoofed feet
-Thing, long legs
-Long neck
-Short, skinny tail
Make some
observations
about this
skeleton
Observations:
-Thick beak
-Elongated, skinny legs
-Three skinny toes
-Long, tapered neck
Make some inferences about the functions of
these skeletal structures:
Can you guess the animals?
Giraffe
Flamingo
Click on parts of each animal to learn about their adaptations.
How do the similar structures of these two
animals serve as different adaptations to their
environments?
Think about some adaptations in the
next example…..
Observations?
Observations:
-Long tail
-Small skull
-Short limbs
-Five toes per foot
-Body set low to the ground
Observations?
Observations:
-Elongated torso
-Short limbs
-Small skull
-Body set low to the ground
-Front feet larger than back feet
-Five toes
Can you make some inferences about the
structures of these two animals?
Can you guess the animals?
Iguana
Gila Monster
Click on a part of the animal to learn about these adaptations..
Iguana
Gila Monster
How do these structures have similar and
different adaptations?
Homologous Structures
A homologous structure is a characteristic
shared by related species that has been
inherited from a common ancestor.
See example
In this next example, take note of any
homologous structures that could
support an ancestral link between
these two animals.
Observations?
Observations:
-
Small skull with
sharp teeth.
-
Forelimbs
proportional to rear
limbs.
-
Long tail
-
Four paws with
claws.
Observations?
Observations:
-
Large skull with
protruding fangs.
-
Prominent front and
rear claws.
-
Broad shoulder blades
-
Dense forelimbs
-
Long tail
Make some inferences about the
structures of these two animals.
Can you guess the animals?
Cat
Lion
Cats and Lions are closely related species,
therefore, they exhibit structures called
“homologous structures”
Can you identify some homologous structures
between cats and lions?
Analogous Structures
Analogous structures are two structures with
the same function but no evolutionary link.
See example
Observations?
Observations:
-Hard, outer shell
-Small skull
-No visible teeth
-Four toes
-Thin forelimbs and back
limbs
Observations?
Observations:
-hard, outer covering
-Long, bony tail,
-Elongated snout
-Three sharp toes
Make some inferences about the
structures of these two animals.
Can you guess the animals?
Box Turtle
Armadillo
Turtles and armadillos are unrelated species
that share similar characteristics. Can you
identify a few analogous structures between
these two animals?
Identifying Related Species
What characteristics do these three
animals have in common?
Do they appear to be
related or unrelated?
Let’s take a closer look at their
skeletons…
Armadillo:
Armadillo
Skeleton
Hard, outer covering
Elongated snout
Long, bony tail
Sharp front claws
Anteater:
Long, tapered
snout
Short, forelimbs
with claws
Long tail that drags
behind the animal
Sloth:
Long forelimbs and hind legs,
relatively similar in length
and size.
Sharp claws
Based on your observations, are these
animals related or unrelated? Or in other
words, do they have homologous or
analogous structures?
Order Xenarthra:
Anteater
Sloth
All three animals are
classified in the order
“Xenarthra” because they
all lack incisors or canines
and have 2-3 predominate
claws. These common
structures are known as
homologous structures.
Armadillo
Identifying Related Species:
1. Make observations about the forms of different
organisms.
2. Draw inferences about the functions of those
forms.
3. Consider how those forms may serve as
adaptations.
4. Compare those adaptations to other organisms.
5. Do the forms and adaptations represent
homologous or analogous structures?
What else might you need to know in order to
identify related species?
Conclusions:
1. By making careful observations and inferences, we are
able to formulate hypotheses on the relationships between
form and function.
1.2.
Certain structures have specific functions according to the
organism and the environment. These are called
adaptations.
3. Structures of related species are known as homologous
structures.
4. Similar structures of unrelated species are known as
analogous structures.
5. By analyzing the structures of these organisms, we can
begin to draw conclusions about their origins and
relations.
The End
The Kangaroo Tail
A Kangaroo’s Tail is long
and muscular, extending all the
way down to the ground. It
serves as a sturdy prop while
the kangaroo sits or stands.
When the kangaroo fights,
sometimes the only limb
touching the ground is the tail!
??Can you think of any human inventions
that may resemble a kangaroo tail in
both form and function?
BACK
Forelimbs
A Kangaroo’s Forelimbs
are thin and short and
help the animal “hop”
forward.
Compare the kangaroo’s forelimbs
to the arms of a runner. How
are they similar and how are
they different in both form and
function?
BACK
Kangaroo Hind legs
The Kangaroo’s hind
legs have tendons that act
like rubber bands,
propelling the animal
forward in quick, strong
leaps.
It’s large feet help the animal
sit and balance, and are
also a very powerful
defense mechanism. No
one wants to experience
the kick of a kangaroo!T
BACK
Giraffe’s Legs
Because its legs are so
long, a walking giraffe
moves both legs on a side
at almost the same time. It
can gallop at up to 56
km/h
BACK
Giraffe Tail
Like many animals, a giraffe’s tails function
as fly swatters. The zebra to the right
demonstrates with his tail, which has a similar
structure to the giraffe’s tail.
BACK
Giraffe Mouth
Their mouths are designed to
pick leaves from trees and
have flat teeth to crush the
vegetation. Therefore, their
feeding structures are
adapted to their feeding
habits.
BACK
Giraffe Neck
Giraffes tend to feed on the
leaves from tall trees where
they experience less
competition from other
herbivores. To reach those
leaves, they need long necks.
BACK
Flamingo Neck
A flamingo’s long
neck helps it extend
down into the water
to feed. It is also used
to stabilize the bird
during flight.
BACK
Flamingo Wings
Flamingos are capable of flying distances up to 300
miles in one night. They typically extend their necks
forward and their legs behind them during flight and
reach speeds of up to 30mph.
BACK
Flamingo Legs
Flamingos have long legs
that allow them to wade into
deeper waters than their
competitors. Their webbed
feet help them to stabilize
themselves in the mud.
BACK
Flamingo Beak and Feeding
Flamingos have a unique
feeding mechanism
whereby they hold their
heads upside down and
filter algae, seeds, and
marine invertebrates such
as shrimp and mollusks
from the water through
their beaks.
BACK
Human arm, bat wing, and whale flipper.
Bat wing
Whale Flipper
BACK
Analogous Structures
Butterfly wings
and bat wings
resemble each
other in form and
function, but
there is no
ancestral link
between the two.
BACK
Iguana Claws
An iguana has
four feet with
five digits on
each. These
claws are used
mainly for
climbing seeing
as the iguana’s
main habitat is in
trees.
BACK
Iguana Tail
The iguana’s tail has
two functions. First, as a
means of balance during
climbing. Second, as a
means of defense
against predators. It can
whip and distract
predators and
sometimes, may
disconnect from the
iguana, but don’t worry;
its grows back!
BACK
Iguana Head and Mouth
Iguana’s have spines
starting at the back of their
head and continuing down
their back which make it
more difficult for predators
to swallow them. Their flat
mouths crush vegetation
and fruit which are the
main sources of nutrition
for these reptiles.
BACK
Gila Monster Tail
A Gila monster’s
short, fat tail serves
as a storage place
for fat. When the
animal is low on
food sources, it
uses the fat from
its tail as a source
of energy.
BACK
Gila Monster Head
The Gila monster has a
large head with a strong
lower jaw, which is where
the animal stores its
venom. One reason why
the head sits low is so the
animal may lick the
ground which is how it
picks up the scents of its
prey.
BACK
Gila Monster Claws
The Gila monster’s short legs and short claws
are ideal for digging burrows, digging for eggs
and food, and climbing.
BACK