Homologus and Analogous

  

 

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.

What Does It Say?

Enjoy :)

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Thomas Malthus

Thomas Malthus was a positive influence to Charles Darwin. He wrote An Essay on the Principle of Population. Malthus says that if we don’t keep in check our food supplies, human population could double every 25 years. In other words, population size increases exponentially while food supplies remain relatively stable. He was arguing for population growth. He could also apply this to nonhuman organisms. This could be why there is a competition for food. Malthus' view that poverty and famine were natural outcomes of population growth and food supply was not popular among social reformers Malthus was a political economist who was concerned about, what he saw as, the decline of living conditions in nineteenth century England. He blamed this decline on three elements: The overproduction of young; the inability of resources to keep up with the rising human population; and the irresponsibility of the lower classes. To combat this, Malthus suggested the family size of the lower class ought to be regulated such that poor families do not produce more children than they can support. The central theme of Malthus' work was that population growth would always overpower food supply growth, creating perpetual states of hunger, disease, and struggle.

 What struck Darwin in Essay on the Principle of Population (1798) was Malthus's observation that in nature plants and animals produce far more offspring than can survive, and that Man too is capable of overproducing if left unchecked. He realized that producing more offspring than can survive establishes a competitive environment among siblings, and that the variation among siblings would produce some individuals with a slightly greater chance of survival. Darwin considered that some of the competitors in Malthus' perpetual struggle would be better equipped to survive. Those that were less able would die out, leaving only those with the more desirable traits

 Thomas Malthus' work helped inspire Darwin to refine natural selection by stating a reason for meaningful competition between members of the same species. "In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long- continued observation of the habits of animals and plants, it at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work".

Charles Darwin, from his autobiography. (1876).

Darwin was skeptical about publishing his book. He knew his work would cause a huge controversy. His wife Emma was very religious and was afraid that this would cause a problem for her. He in no way wanted to cause problems for her in the church community. He was also afraid that it would threaten his friend’s status quo and his so he hesitated.

http://www.ucmp.berkeley.edu/history/malthus.html