Week #3 - Analogy/Homology Blog Post

HOMOLOGOUS TRAIT - INCISORS

BEAVER GNAWING AWAY

THE BEAVER

Beavers, are great builders with powerful jaws and big strong incisors. 

(Please see analogous trait below for more information on the beaver)

ELEPHANT USING TUSKS TO PEEL BARK FROM A TREE; ONE OF MANY USES

ELEPHANTS USING THEIR TUSKS TO FIGHT

THE ELEPHANT

The elephant is the largest land animal currently living. It is a herbivorous mammal with thick almost hairless skin, a long flexible prehensile trunk which they use for a multitude of tasks like drinking, tearing up food and placing it in their mouths, and sucking up water to spray their bodies. They also have upper incisors forming long curved tusks which they use for digging, fighting and peeling bark from trees, as well as large fan-shaped ears.

HOMOLOGOUS TRAIT

The homologous trait shared by the beaver and the elephant is the incisor tooth. An incisor tooth is a sharp-edged tooth in mammals that is adapted for cutting or gnawing. The incisors are located in the front of the mouth between the canine teeth. Although this trait has a similar origin, the structures and functions differ. Beavers use their incisors to knock/cut down and gnaw trees, while elephants use theirs for fighting, digging, and peeling bark from trees to eat. 

Beaver incisors are small, flat, thin, but very strong. They have a hard orange coat that keeps them from breaking and because gnawing wood wears the teeth out, they continue to grow throughout their lifetime. Elephant incisors, also known as tusks, are made of ivory (a hard, smooth, yellowish/white, dentine) which serves as protection. These tusks are rather long and curvy.

COMMON ANCESTOR

The general common ancestor is a mammal. I know that the ancestor possessed this homologous trait because all mammals possess incisor teeth. 

ANALOGOUS TRAIT - WEBBED FEET

BEAVER WEBBED FEET- 5 TOES ALL WEBBED

  

JUST KEEP SWIMMING....

   

YES, UP TO SOMETHING!

THE BEAVER

Beavers, also known as "nature's best architects" are semi-aquatic large rodent mammals. They are nocturnal herbivores who live in colonies near permanent water and woody plants (streams, ponds, small lakes, and marshes). Their life expectancy is 8 to 10 years, they are very territorial and are known to mate for life. Beavers have made adaptations that allow them to live in water. They have powerful jaws and big strong incisors, a flat hairless tail which helps maintain their balance and is also used as a rudder, short front legs with heavy claws, long rear legs with webbed feet which help propel them through water, a thick layer of fat that keeps them warm under water,  naturally oily and waterproof fur, transparent eyelids which help them see under water, and although they cannot breathe under water they have a special respiratory adaptation that allows them to store enough oxygen to swim under it. 

WEBBED FEET - 4 TOES 3 WEBBED

SWIMMING, OH SO GRACEFULLY

UGLY DUCKLING? I DON'T THINK SO!

                      

THE DUCK

The duck is a bird and because it lives in places near water (marshes, ponds, rivers) it is also known as a "waterflow". There are many different types of ducks; dabbling duck, diving duck, perching duck, etc. Ducks have short necks, short wings, a stout body, short legs and webbed feet which they use as paddles to swim. These webbed feet are the reason why they waddle instead of walk. Their mouth, known as their bill, is used to hunt for food. Underneath their waterproof coat, they have fluffy feathers which keep them warm.

ANALOGOUS TRAIT

The analogous trait shared by both the beaver and the duck is webbed feet. Webbed feet is defined as having digits connected by a thin fold of skin; palmate (shaped like an open hand and having 3 toes connected by a web). Both the beaver and the duck use their webbed feet as propellers to swim; this meets the similarity in the function of the trait. Although only 3 of the duck's 4 toes are webbed, as opposed to all 5 of the beaver's toes, there are still similarities in their structure. The toes are claw-like and in between is a stretch of flexible web. 

COMMON ANCESTOR 

In my opinion, the common ancestor (chordata vertebrate) of the beaver and the duck did not possess this analogous trait. These two species have developed webbed feet through parallel evolution not through inheritance. Beavers for example, lived in land, but have made adaptations which enable them to now also live in water. Not all birds are water birds, therefore ducks have also made adaptations.