The two different species that share the same trait is a cat and human. These two share the same bone structure, same basic pattern of bones (one long bone, a joint, two small bones, a wrist made of lots of little bones and then five digits on the end) , even though they serve very different functions (human arms and cat legs for walking).
The bone structure in humans are as follows, your radius and ulna are in your lower arm, and the humerus is in you upper arm. The radius goes from your thumb to your humerus, crossing over the ulna which goes from your pinky to your humerus.
Your humerus also connects to your scapula (or shoulder blade) in what is called a "ball and socket" - the rounded end of your humerus fits perfectly into the indent in your scapula.
In your fingers, you have carpals, which are your wrist bones; metacarpals, which are the palm of your hand; and phalanges, which are your finger bones.
In cats the arm structure is caput
head of the humerus
humerus
the upper bone of the forelimbs
The lower part of the forelimbs (shank) consists of 2 bones, which are connected via an articulation, thus the paws can be turned around.
radius
one of the 2 bones of the lower leg
ulna
the second bone of the 2 bones of the lower leg
radial notch
a hollow in the ulna, where the head of the ulna is connected to the radius
As you can see these two share the same bones like humerus and radius. Their differences are what each are used for.
The common ancestor to these two And to placental mammals Maelestes gobiensis he possessed the trait because he had bones like all the placental mammals.
Analogous
Above we see the butterfly wing and the bat wing. Comparing the wing of these animals reveals more differences than similarities. Insects have two pairs of wings, while bats and birds each have one pair. Insect wings lack bones, but bird and bat wings have them. Butterfly wings are covered in scales and bat wings with bare skin. All of these organisms have adapted to life in the air and in doing so have evolved wings. Since wings have evolved independently in each of these groups, and don't indicate that they are closely related, the possession of wings is an analogous trait.
The common ancestor of these two is A little microscopic thing called a gastrula. No eyes. No head. No wings.
The wings of the butterfly and the wings of the bat evolved independently, long after their ancestral lineages diverged.
Vanessa,I like how you broke down the structure of the cat arm in relation to that of a human arm. I didn't realize how similar they were. It simplified that homologous trait for me. Also, your comparison of the analogous traits of the bat and butterfly makes sense, although they have wings and fly, they do not have the same wing structure.
ReplyDeleteGood set of homologous traits. I liked the detailed description of the anatomical similarities. How do the differences contribute to the different functions? Maelestes gobiensis is a possible candidate for a common ancestor, but the main thing you need to understand is that the ancestor was a mammal and the limb structure you describe is indicative of mammals in general.
ReplyDeleteGood work on the analogous trait. Most students compared the butterfly to a bird, so it was interesting to see the butterfly/bat comparison. A gastrula is not a particular organism, it is an embryonic stage of animals in general that occurs early in embryonic development. Regardless, we know that the bat developed it's wings independently after mammals arose, so there is no chance it inherited the trait from an ancestor some 100's of millions of years ago, which is how long ago these two organisms diverged. The butterfly may have inherited it's wings from that organisms (I don't believe it did) but as long as one of these creatures developed the trait independently, it is an analog.
Good comparisons! I did not have the brain power to be very creative in my choices and while I chose a cat and a butterfly as well, I think you did a better job of analysis. Your post had a lot of information and you made all your points very clearly. Nice work!!
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