heterotroph hypothesis 

The earliest cells were probably heterotrophs. Most likely they got their energy from other molecules in the organic “soup.” However, by about 3 billion years ago, a new way of obtaining energy evolved. This new way was photosynthesis. Through photosynthesis, organisms could use sunlight to make food from carbon dioxide and water. These organisms were the first autotrophs. They provided food for themselves and for other organisms that began to consume them. 
After photosynthesis evolved, oxygen started to accumulate in the atmosphere. This has been dubbed the “oxygen catastrophe.” Why? Oxygen was toxic to most early cells because they had evolved in its absence. As a result, many of them died out. The few that survived evolved a new way to take advantage of the oxygen. This second major innovation was cellular respiration. It allowed cells to use oxygen to obtain more energy from organic molecules. 


Lamarck

Jean Baptiste Lamarck (1744–1829) was an important French naturalist. He was one of the first scientists to propose that species change over time. However, Lamarck was wrong about how species change. His idea of the inheritance of acquired characteristics is incorrect. Traits an organism develops during its own life time cannot be passed on to offspring, as Lamarck believed.

Need
-organisms strive to better then selves and become more successful
Use and Disuse
-Used parts advance, unused parts fade or disappear 
Inheritance of Acquired Traits
-modified body structures during the life of an organism are passed onto their offspring

How was this theory disputed?

Weissman's experiments with mice.

Darwin

Darwin spent many years thinking about the work of Lamarck, Lyell, and Malthus, what he had seen on his voyage, and artificial selection. What did all this mean? How did it all fit together? It fits together in Darwin’s theory of evolution by natural selection. It’s easy to see how all of these influences helped shape Darwin’s ideas.

EVOLUTION OF DARWIN’S THEORY

It took Darwin years to form his theory of evolution by natural selection. His reasoning went like this:

  1. Like Lamarck, Darwin assumed that species can change over time. The fossils he found helped convince him of that.
  2. From Lyell, Darwin saw that Earth and its life were very old. Thus, there had been enough time for evolution to produce the great diversity of life Darwin had observed.
  3. From Malthus, Darwin knew that populations could grow faster than their resources. This “overproduction of offspring” led to a “struggle for existence,” in Darwin’s words.
  4. From artificial selection, Darwin knew that some offspring have variations that occur by chance, and that can be inherited. In nature, offspring with certain variations might be more likely to survive the “struggle for existence” and reproduce. If so, they would pass their favorable variations to their offspring.
  5. Darwin coined the term fitness to refer to an organism’s relative ability to survive and produce fertile offspring. Nature selects the variations that are most useful. Therefore, he called this type of selection natural selection.
  6. Darwin knew artificial selection could change domestic species over time. He inferred that natural selection could also change species over time. In fact, he thought that if a species changed enough, it might evolve into a new species.
Wallace’s paper not only confirmed Darwin’s ideas. It also pushed him to finish his book, On the Origin of Species. Published in 1859, this book changed science forever. It clearly spelled out Darwin’s theory of evolution by natural selection and provided convincing arguments and evidence to support it.

APPLYING DARWIN’S THEORY
The following example applies Darwin’s theory. It explains how giraffes came to have such long necks.

  • In the past, giraffes had short necks. But there was chance variation in neck length. Some giraffes had necks a little longer than the average.
  • Then, as now, giraffes fed on tree leaves. Perhaps the environment changed, and leaves became scarcer. There would be more giraffes than the trees could support. Thus, there would be a “struggle for existence.”
  • Giraffes with longer necks had an advantage. They could reach leaves other giraffes could not. Therefore, the long-necked giraffes were more likely to survive and reproduce. They had greater fitness.
  • These giraffes passed the long-neck trait to their offspring. Each generation, the population contained more long-necked giraffes. Eventually, all giraffes had long necks.

  1. Stabilizing selection occurs when phenotypes at both extremes of the phenotypic distribution are selected against. This narrows the range of variation. An example is human birth weight. Babies that are very large or very small at birth are less likely to survive. This keeps birth weight within a relatively narrow range.
  2. Directional selection occurs when one of two extreme phenotypes is selected for. This shifts the distribution toward that extreme. This is the type of natural selection that the Grants observed in the beak size of Galápagos finches.
  3. Disruptive selection occurs when phenotypes in the middle of the range are selected against. This results in two overlapping phenotypes, one at each end of the distribution. An example is sexual dimorphism. This refers to differences between the phenotypes of males and females of the same species. In humans, for example, males and females have different heights and body shapes.

Evolution

Flash animations

Files:

Vocabulary

  • allele: Variant of genes.
  • chromosome: Structure composed of DNA wrapped around proteins.
  • DNA (deoxyribonucleic acid): Hereditary material of a cell.
  • genotype: Describes the combination of alleles that an individual has for a certain gene.
  • homozygous: Having two of the same alleles for a specific gene.
  • heterozygous: Having two different alleles for a specific gene.
  • phenotype: Describes observable traits.

Helpful links

Above are some but not all of our vestigial structures.


Xiphoid process is another, google it!

I personally have heard the wisdom teeth were more for chewing vegetation, rather than meat as stated in the video, since they are grinding teeth rather than tearing, no matter, they are still vestigial now.
Peppered Moths, Evolution in progress!

Sources of Genetic Variation

Mutations
Sexual reproduction
  • crossing over
  • independent assortment
  • random fertilization