FFormm && FuunccTiioN

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:

Take a few minutes to make some

observations about the form of this

animal.

observations

Long, thick-boned tail that reaches to the ground

Large feet

Short arms with finger-like appendages

Elongated rear limbs with shorter bones connecting them to the

pelvis.

For example, you might say….

example

Making Inferences:

To make an inference means to draw conclusions from your

observations.

What are some functions of these structures??

inferences

Why is the tail so long and sturdy?

Why are the feet so large?

What are the arms used for?

How might long, skinny legs help it move?

Some questions you might start with are…

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

Iguana Gila Monster

Click on a part of the animal to learn about these adaptations..

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:

Sharp front claws

Elongated snout

Hard, outer covering

Long, bony tail

Armadillo Skeleton

Anteater:

Long, tapered snout

Short, forelimbs with claws

Long tail that drags behind the animal

Sloth: Sharp claws

Long forelimbs and hind legs, relatively similar in length and size.

Based on your observations, are these animals related or unrelated? Or in other

words, do they have homologous or analogous structures?

Order Xenarthra:

Armadillo

Sloth

Anteater 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.

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.

1. By making careful observations and inferences, we are able to formulate hypotheses on the relationships between form and function.

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 TailA 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?

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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

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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

Giraffe’s Legs

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Human arm, bat wing, and whale flipper.

Bat wing Whale FlipperBACK

Analogous Structures

Butterfly wings and bat wings resemble each other in form and function, but there is no ancestral link between the two.

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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.

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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!

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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.

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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.

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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.

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Gila Monster Claws

The Gila monster’s short legs and short claws are ideal for digging burrows, digging for eggs

and food, and climbing.

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