History of the evolution theory

Evolution is a Latin word for continuous, unidirectional change

-Evolution of universe

-evolution of ideas

-organic evolution

The idea of organic evolution states that all life form on Earth is descended from other life, through small changes. In other words all life is linked by a process of ancestry and descent. This observation goes back at least as far as the Greeks in the fifth century B.c., who realized that all animals were built on a common plan. In some of the Greek philosophers  thought the idea of “everything changing” was a basic element.

However the dominance of the church in Western thought obeyed the thout of evolution for over a thousand years. According of Christian belief, all plants and animals were created as we see them today and there is no possibility  that species could change.

During the 1700’s it become more and more difficult for scientists to stay with this static view of nature with their expanding knowledge of the biological world:

-When Linnaeous made the first standardized classification of organic species, there were no more than 8000. However lots of discovery trips brought 100’s of new species.

The questions have emerged!!!!

-how could all of these animals have fit onto Noah’s ark?;

-Why did faraway places such as Australia  and South America have their own unique type of animals?

-if every kind of animals on earth had dispersed from mountain Ararat (Turkey) why did no European type animals ended up in Australia?


What is your opinion? Do you have the answer to these questions??

Other Questions related to geology

-Cuvier by the early 1800’ demonstrated that some of the animals were  extinct. (Big animals such as Mastodon, which are much bigger than any of the animals exist today. This was an evidence nobody could hide).

Cuvier soon after demonstrated that the species which become extinct soon had been replaced with other species. How could this be explained by genesis, which states that all species were created once.

Scientist soon came up with the idea that genesis could not explain the fossil record, but they had no other explanation for it!!!!!


What is your opinion? Can  you explain these?

George Buffon (1707-1788) French zoologist (molten ball guy)

He did big steps for the conception of evolution

-He was the first to state the concept of species and noted that each species exists as a separate entity and he demonstrated that no species could interbreed with another.

-He also noted that the environment directly caused variations in the offspring. With this he was the first to realize the interrelationship between environment and species. (Later ADAPTATION)

-He noted that there are also changes due to inheritance of characteristics from both parents (INHERITANCE)

- He put these two concepts together and come up with the statement that modification of organisms are due to inheritance of characters and changes caused by the environment.

He made this fundamental statement, however he could not and did not explained how these changes had happened?

Erasmus Darwin Britain (Charles’ grandfather)

He was strongly influenced by Buffon’s ideas. As an animal experimenter

-he saw, that there are many changes going on during ONTOGENY (the development of an individual)

                    caterpillar    -  butterfly

                    tadpole   -   frog

-He saw that in breeding, changes can be recognized from generation to generation, although these changes are very small.

-He also realized that the species become adapted to their environment primarily by gathering food, (elephant’s trunk: tear the grass and lifting it to mouth), or by security (protective coloration, wings, shells, legs)

Jean Baptist Lamarck (1744-1829)

One of the greatest naturalist in the eighteenth century.

-foundation of modern invertebrate zoology

-He was the first to see all life -both plant and animal- as an integrated whole and he used the term BIOLOGY for it.

- He named first the inheritance of acquired characteristics.

in other words this states that the effect of environments could be inherited by offspring.

-He found a mechanism for this theory. (The change of the environments will lead to changes in needs of the organisms. Animals have to change their habits). How did giraffes get the long neck?

Charles Darwin 1809 February 12 (he was born on the same day with Abraham Lincoln)

-medical student at the Universuty of Edinburghwhen he learned medicine and natural history.

-Theology student, and finished college in a Christ college in Cambridge.

He was always interested in natural science and collected animal, plant and rock specimens.

-He was from a wealthy family so he did not have to have a specific job, however his father wanted him to have a job.

-When he was 22 there was a great opportunity for him. He could be the company as a naturalist of the captain on a voyage on H.M.S. Beagle around the earth.

- During the trip he collected a huge amount of species from different plants and animals. He also made tremendous amount of observation in his notebooks. These gave him the basis for his later publications and his theory of evolution.

-He saw the fantastic variety of species found on the earth,

-The huge population of different species.

-The amount of competition among population for food. (STABLE number in populations)

-He saw that not all offspring survives, but the ones the best fit for the certain environment

-He collected enough data for his revolutionary hypothesis of


The best fit for life survive

Finches of Galapagos is his best evidence for this!!!

Evidence for evolution

1. Branching organization of life

Since Linneaeus’s classification it was clear, that nature was organized into a great hierarchy of groups nested within groups. In Darwin’s time this structure was deduced from the obvious anatomical features of animal and plants.

In our generation striking proof of this branching structure has been added from molecules in our body. Comparisons of the molecular structure of a great number of organisms have repeatedly shown the same pattern of branching suggested by anatomy.

2. Homology

Organs with strikingly different functions are commonly built from the same basic parts. (Forelimbs of vertebrate are used for many purposes:

-grasping; humans

-flying; birds

-swimming seals, dolphins

But they have the same underlying structure of bones, muscles, and nerves.

Why is that? ---- Most likely they have the same common ancestor.

Similar elements derived from a common ancestor are called homologous elements.


What is your opinion? Is this really  prove that they had to have the same ancestor?


By contrast structures, that perform the same function but are not derived from the same evolutionary origin are known as analogous (wing of birds or bat in vertebrates vs. wing of butterfly insects)

3. Vestigial structures and other imperfections

Darwin pointed out, that the nature’s imperfections are more revealing than the examples of good design. He pointed out, that lots of animals have tiny remnants, or vestiges, features which they no longer use.


-stunted tail bone



-tiny splint bones that are remnants of ancient side toes

Why would these features exist on these organisms unless they evolved from animals that once needed these organs?


What is your opinion? Is this really  prove that they had to have  an ancestor which used those structures?

4. Embryonic history

The great German embryologist Karl Baer (1792-1876) showed that the development of animals was powerful evidence of their ancestry.

Whether they develop into fish, amphibians, or humans all vertebrate embryos start out very similar, with gill slits and long tail. During the embryonic development in case of higher order animals these organs would be lost.

Why would humans have embryos with gill and tail unless their ancestors also once had these features?

The embryonic development or ontogeny  of vertebrates retains so much of their evolutionary history, or phylogeny, that Ernst Haeckel (1834-1919) German embryologist said:

ONTOGENY RECAPITULATES EVOLUTION in other words the embryonic development repeats the evolution.

(of course this is not happen step by step, but embryonic development is one of the most important arguments for the reality of evolution.


What is your opinion about ontogeny?  How can you explain, that it looks like that  every organism have the same organic plan?

5. Biogeography

Many regions of the world have unique animal and plant assemblages.

The most striking fact of evolution is that on many continents unrelated animals have evolved to occupy similar ecological niches.

Australia - pouched mammals or marsupials

they developed forms that are mimic those of wolves, cats, anteaters and so on. This phenomena is the so called ECOLOGICAL CONVERGENCE.

The only logical explanation:

which is on the other hand evidence for plate tectonics, that Australia broke apart from the supercontinent Pangea, when the evolution was at that level (marsupials). Later on in Australia the evolution there was different from the way in the other part of the world. 


What is your opinion? Is this really  prove that tevolution has to exist?

Microorganisms can evolve very fast in a matter of hours in response to changes in their environment. (Cold, flu)

I belive that there are still questions in the mechanisms of evolution, but there is no question that it has happened.  We do not clearly understand what gravity is, yet this does not change the fact that objects fall toward the earth.

The Basis of evolution

The science of how inheritance takes place is called Genetics

During Darwin’s time scientists knew little about how favorable variations were inherited.

The father of genetics was actually a monk who lived in Austria (Chek republik today Brunn) in a monestry, Gregor Mendel (1822-1884). He did experiment with pea flowers.

-he concluded that traits such as color are controlled by a pair of factors we now call genes.

-Also he concluded that genes controlling the same traits occur in alternate forms or alleles.

-The one allele may be dominant over another (However the other is not lost, but can come out later on) Since the environment is changigng probably when the other allele comes out that could be more favorable for the given environment, and become the evolutionary trend)

-Offsring recieve one allele (gene) of each pair from each parent.

Genes and chromosomes

The cells of all organisms are contain threadlike structures called chromosomes. Chromosomes are complex double-stranded helical molecules of deoxiribonucleic acid (DNA). Specific segments of the DNA molecule are the basic hereditary units, the genes.

The number of chromosomes are specific for a single species but varies among species. For ex. fruit fly has 8 chromosomes, humans have 46, and horses have 64.

In sexually producing organisms the production of eggs and sperm result when parent cells undergo a speciel type of cell division called meiosis.

Each eggs and sperms contain only half of the chromosomes; in humans 23.

The fertilized eggs however contain all 46 chromosomes and starts to the cell division called mitosis that does not reduce the chromosome number.

The genes are passed from one generation to the other and mutation can occur, and any change occur in the sex cells is inheritable.

-mutations are random in respect to fitness

-it may be harmful, neutral or beneficial.

Which one is harmful which is beneficial is depend on the environment.


What is your opinion? Now what is your opinion about evolution?

The Mechanism of Evolution


We all know that in each population of different species there is an enormous potential for variation. Think of humans!!!!

We already talked about mutations.

-Some of these variations are the result of interaction between individuals and the surrounding environment and it is due to factors such as food suply, living habitat, temperature, sunlight, and rainfall.

-Other variations are genetic in origin and is due to the somewhat different genetic make-ups of the individuals in the population.

       genotype-----The total genetic information that codes for an             individual

           Phenotype--- The anatomical results of growth and development   from a given genotype.

There is no population in the earth in which the genotypes and phenotypes of all individuals are identical. All populations include some genetic variability among its members. (difference in sex is an example of genetic variation).

2.Natural Selection

Given the fact that all or most populations display genetic variability, not all individuals are equally survive. Especially important the success in reproduction.

Those plants and animals that are succesfull breeders are the ones passing on their genetic characters to the next generation.

One or several mutations may result in individuals that are more successful in adapting to small changes in the environment or in breeding. These individuals will pass on their genetic features to an incresingly larger proportion of the population. The particular mutations that confer these advantages will spread and fixed into more and more individuals. This process is called natural selection.

Natural selection results in a slow continuing shift in the genetic make-up of a population. Given enough time this process can change the gene pool of a population to probably call it a new species, when the original and the new would not interbreed with each other.

The gradual change through time of one species population to another phenotypically distinct population is called PHYLETIC EVOLUTION, or PHYLETIC GRADUALISM. (Phylogeny is the study of ancestral-descendant relationships among organisms). THIS IS THE MODEL DIAGRAM FOR IT:

There is an other wiev, punctuated equilibrium holds that a species changes a little or not at all during most of its history and than evolves rapidly to give rise to a new species. Long periods of equilibrium are occasionally punctuated  by short periods of rapid evolution. It looks like that the fossil record support this idea.

However we must know that the deposition is not continuous; thus the lack of transitional forms is simply the artifact of the fossil record.

This new species without transition can be a result of what is called ALLOPATRIC SPECIATION In order for these speciation events to occur a segment of the population must be geographycally isolated!!!!!


This is the third, and probably the most important facet of this mechanism is ISOLATION, especially geographyc isolation.

Mountain range, land barrier, periphreral isolates; so on.

Patterns of evolution

1.Divergent evolution

Divergent evolution happens when an interbreeding population gives rise to diverse descendant types of organisms. Divergence into numerous related types involves an ADAPTIVE RADIATION which occurs when species of related ancestry exploit different aspects of the environment (Finches of the Galapagos)

While divergent evolution leads to organisms that different markedly from their ancestor, Convergent and parallel evolution are processes where similar adoptations arise from different groups.

2.Convergent evolution

Development of similar characteristic of distantly related organisms

3.Parallel evolution

development of similar characteristic of closely related organisms

4.Mosaic evolution

All organisms are mosaic of characteristics, some of which are retained from the ancestral condition, while others are more recently evolved.


Dyno like teeth, tail, hind limb, and brain size but!

feathers, and wishbone charact. of birds

Evolutionary trend

most of the group of living things have trends in their evolution

A really common trend is increase in size.

Appereance of vestigials so on.

Living fossils --- no change ever!!!!!!  Gingko


If the specimen evolves into an other gradually -- Pseudoextinction

Sudden termination with no continuation ------extinction

Mass extinction