Categorizing a common ancestry like eukaryotes and prokaryotes and back spine give us a common ancestry among homo sapiens. This is called “HOMOLOGOUS STRUCTURES.”

Fins of fish, and Dolphin flippers are similar to each other but we know fins and flippers are deriving from completely different structures. Structures that are different because of convergent evolution are referred to as “ANALOGOUS STRUCTURES.” 

 

Evidence in keeping records of similar structures and how they converged evolutionarily as analogous and homologous structures due to common ancestry, gives us records of how species evolved by (comparative anatomists), and that information is offered as evidence for evolution.  For example; forelimbs, bones of humans, cats, whales, and bats look different because the forelimbs are used for different ways of existing and responding to the environment. They nevertheless  have similarities in them of their positioning,  and aspects of their shape. Recognized as homologous structures of similarities, gives us information to determine evolutionary relationships and how they have bent, shaped and twisted to deal with different selective pressures from the environment. Biologists that determine the structure is homologous and not just structure similarity, or appearance,  but in evidence from developmental patterns,  and aspects of how structures are related.

 

DNA sequences are “homologous” across organisms. This does us justice to be able to look at the relationships.  We look at DNA sameness in phylogenetic relationships of a group of species. Characteristics of a species changes over time and this change is referred to as  “derived characters” from evolutionary pressures from the environment, for adaptation to survive, compared to “primitive characters.”

 

Primitive characters does not mean less well adapted to their time and environment, because it only means their “Ancestor trait.”

 

Some species have traits that changed a lot and others have traits that changed little. The derived characters are what they no longer share with the ancestor species. Species that are homologous have “shared derived traits.” Some evidence for homologous traits, like the jaw, or presence of limbs, on the structure are “shared derived traits.” Hair is a shared Primitive trait.

 

So cats, gorillas, and humans have hair, so we have a “shared primitive trait,” and we have 5 shared derived traits,(1)  jaws, (2) limbs, (3) hair (4) lungs (5) tail or not having a tail. Humans and cats share 4 of those shared derived traits and do not share the tail as a shared primitive trait. So it might suggest that our structure is closer to the gorilla, than a cat.

 

So on the node branch, of the tree of similarities, in categories,  of shared derived traits, lung fish are more like humans and gorillas than trout with “Primitive derived traits.”

 

“Phylogenetic Systematic Analysis” branch nodes, show us how shared primitive traits,  have evolved in similar structures (over time),  with shared derived traits in  comparisons of the categories of species. The methods that have been derived are now very primary in the way evolution is studied,  because patterns of relatedness of structures, both primitive,  and evolved are compared. Some primitive traits from species have changed so much, that the primitive traits have gone completely, and the evolved traits are here today.

 

The information here in this write – up,  is about “DNA” and how we learned about our specie’s, evolution, which is the ultimate goal of BIOLOGY. 

 

Drawing on the information served from the analysis of the categories of species,  it provides a way to look at how the life, in all it’s diversity, on earth, including the evolution of complex cells,  plus the evolution of multicellular organisms such as ourselves,  and how these events contribute to patterns of life today, which is a common derived trait that all life, on earth shares, which is a (Universal)  Planetary Common Ancestry.

 

It is the information “encoded” in the first DNA,  which still exists in some forms today, even though it has been copied,  and modified,  multiple times,  but theoretically can be traced all the way back to it’s origin.

 

The First living organisms must have risen  3.9 to 3.5 billion years ago based on geological and fossil evidence. The oldest fossil organisms are 3.5 billion years old,  and these organisms already resemble modern prokaryotes, which suggests that life evolved earlier.

 

The first entity we might call “Living” was a single simple cell with a membrane, and RNA based genetic system,  and it’s ability to extract energy nutrients by breaking down organic molecules that it absorbed. DNA took over (the information storing role). The major effects such information storing mechanism to establish cooperation among different kinds of bio – molecules. So life existed only as a prokaryotic cell for 1.5 billion years.

 

The two major lineages of prokaryotes,  are (bacteria and archea). The differences between bacteria and archea are biochemical properties.  They today live in hot springs or extremely salty water. Prokaryotes evolved an enormous variety of biochemical (metabolic) pathways, with which to (1) capture, (2) store (3) and to use energy. Evolution was needed for these pathways to work. Nearly all metabolic pathways occured in modern cell evolution before the existence of Eukaryotes.

 

A transforming event in the history of Life was biochemical pathways that captured energy from sunlight,   and stored simple sugars , a process known as “photosynthesis.” Photosynthesis tapped into an endless source of energy, so was extremely successful at adapting. The most important thing about photosynthesis is,  in the present context, most successful pathways generated oxygen as a waste product.  So consequence of this fact over the course of history of about 1 billion years,  this increased the Earth’s atmospheric oxygen,  from almost zero to where the readings are today,  that are called “modern levels.” Oxygen is highly reactive and tends to break down organic molecules. Increasing oxygen levels caused many organisms that originally evolved in the absence of oxygen to go extinct. Some groups adapted to increased oxygen levels and the most notable adaptation was adaptability of biochemical pathways of cellular respiration, that used oxygen to extract energy stored in the organic molecules, or organisms molecules much more efficiently. Cells then found a new source of fuel, plus a better way to burn fuel that they had for energy. Another positive result of oxygen accumulation was the eventual development of an ozone layer around the earth, in the upper atmosphere. This ozone layer is a modified form of oxygen that absorbs damaging UV radiation from the sun, and this permitted cellular organisms to live on land without radiation burns for the first time in history. This land arrival started the multicellular organism’s earthly journey of the Evolutionary Trek over 3.9 to 3.5 billion years. 

 

Darwin said,” All living things have much in common in their chemical composition, and their germinal vesicles,  their cellular structure, their laws of growth,  and reproduction…therefore inferring from analogy that probably all organic beings which have ever lived on the planet earth have descended from the “One Primordial Form” into which life was first breathed, being the Prokaryotic simple cell that evolved with biochemical pathways,  and evolved into the Eukaryotic complex cells. This is the common shared Ancestry, Primitive trait,” of us all. 🙂

All 8 billion people are relatives. Carolyn d Hogarth Canada. I love this part out of all the courses I took. 

1 Earthling and After 40 years of study, of all kinds of studies, I absolutely agree 100% with Darwin. 🙂 

 

 

 

 

 

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