Two major hypotheses as to the origin of the solar system and therefore the earth:
1. Big-Bang Theory a. Most scientists believe that about 5 billion years ago the solar system was a swirling mass of dust and gas. b. Within a few million years the material had collapsed inward and formed the sun. c. The remaining dust and gas ringed the sun as an enormous disk. d. This material is thought to have collected in clumps and formed the planets. e. Earth is thought to be about 4.6 billion years old according to this hypothesis.
2. Creationism —account of the origins of the universe and solar system in which a supreme, all-powerful being created the universe.
According to current evolutionary theory, life appeared on earth about 3.5 billion years ago.
Evidence from microfossils and
(Carbon-14 or Potassium-40) support this theory.
—the theory that species change over time.
Types of evolution include:

—change in allele frequencies within a population. May be caused by natural selection of traits that already exist within a population or by natural selection of traits produced in a population by mutations.

—evolutionary change at the species level or higher; that is, the formation of new species, new genera, and so forth.

Important proponents of evolutionary theory in order of occurrence include:

Aristotle
— who lived in the 300s BC, referred to a "ladder of nature"—a progression of life forms from lower to higher —but his ladder was a static hierarchy of levels of perfection, not an evolutionary concept.
 Charles Lyell
—a Scottish geologist wrote Principles of Geology (1830). Lyell proposed that plant and animal species had arisen, developed variations, and then bec ame extinct over time. He also believed that the Earth’s physical landscape changed over a long period of time.
 Thomas Malthus — wrote an essay called The Principles of Population . In it,
Malthus proposed that populations outgrew their food supplies, causing competition between organisms and a struggle for one species to survive against another.
 Jean Baptist de Lamarck
—proposed the first mechanism for evolution called “the inheritance of acquired characteristics”.
 Charles Darwin —naturalist on ship HMS Beagle. Ship was chartered for a five year mapping and collecting expedition to South America and the South Pacific.
Wrote a book called On the Origin of Species, which proposed the mechanisms for evolution to be a process called natural selection.
 Stephen Jay Gould —(American paleontologist) in 1972 the proposed the theory of punctuated equilibrium.
Indirect evidence for evolution includes:

The fossil record

The
or geologic column —based upon the idea that the earth
’s layers can be dated according to what fossils they contain, older organisms being found near the bottom of the column and younger organisms found nearer the top of the column. By matching rock layers with fossils called index fossils, geologists can determine the age of the rocks, while paleontologists can determine the age of the fossils. This is called
. Includes the Precambrian,
Paleozoic, Mesozoic and Cenozoic (most recent) Eras

Comparative anatomy

1.
—structural features with a common evolutionary origin. They may be similar in arrangement, function, or both. Examples would be a whale’s fin and a bird’s wing.
2.
—body parts of organisms that do not have a common evolutionary origin, but are similar in function. Examples would include insect wings and bird wings.
3.
—body structure that has no function in a present day organism but was probably useful to an ancestor.
4. Embryology —the study of how animal embryos develop; during early stages of development many animal embryos look similar

Biochemistry —comparisons of the proteins, DNA, or RNA of different species.
Direct evidence for evolution includes:

Pesticide resistance in insects and other organisms

Antibiotic resistance in bacteria
Processes involved in evolution include:
—the process by which organisms with favorable adaptations (favorable variations) survive, and reproduce at higher rates than organisms with less favorable adaptations.
From all the information gathered by Darwin, two central concepts emerged to form the basis of his theory of evolution.

First, Darwin observed that variations within a species were dependent on the environment. Adaptations are genetically coded traits that occur in organisms and enable them to be more successful in their environment. Darwin reasoned that the importance of these adaptations is to ensure the survival through reproduction of that species. The organisms that lack these adaptations will not reproduce as successfully.


Secondly, the organisms on the Galapagos Islands had become geographically separated from one another. This resulted in reproductive isolation . There is no interbreeding between organisms of the same species that are located on different islands. For example, finches on one island could not breed with finches of the same species on another island. He theorized that within a population of a species, adaptations would arise due to reproductive isolation. The organisms would develop adaptations to their environment over time that would result in significant differences between the same species on different islands.
How natural selection acts on populations:

Individuals tend to produce more offspring than the environment can support.
(competition)
 In any population individuals have genetic variation. These variations may already exist in a population or may be caused by mutations. (variation)
 Individuals with certain favorable variations survive longer and thus produce more offspring that have the same favorable variations. (selection)
 Over time, offspring with these favorable variations make up most of the population and may look entirely different from their ancestors. (generations)
Types of selection include:
1. Stabilizing selection —individuals with the average form of a trait are selected.
2. Directional selection —individuals with one extreme form of a trait are selected.
3. Disruptive selection —individuals with either extreme form of a trait are selected.
4. Sexual selection —preferential choice of a mate is based on the presence of a particular trait or combination of traits.
5. Artificial selection —intentional breeding of organisms to produce certain traits
—of the species that have existed on the planet, more than 99% are extinct. Mass extinctions are thought to be brought about by some sort of catastrophe or climate change that produces conditions too severe for most species to endure. Extinction of a species is thought to be a major cause of evolution by opening niches that will be filled by another species.

—is the evolution of a new species that occurs when interbreeding happens, or when the production of fertile offspring is prevented. In the physical world, natural barriers form and cause the breakup of populations to form smaller populations. Volcanoes, sea-level changes, and earthquakes are a few examples of natural occurrences that affect populations.
This is known as
. Geographic isolation prevents interbreeding, so gene exchange will cease. So over time, each smaller population will adapt to their new environment through the process of natural selection.
Eventually, this causes the gene pool of each group to become different so that it can be concluded that there is a new species formed.
The rate of speciation can proceed in one of two timeframes:

—idea that evolution occurs a slow even rate over extremely long periods of time

—trends in the fossil record cannot be attributed to gradual change within a lineage, but rather to quick bursts of evolutionary change.
Patterns of evolution:

—when diversity seems to have occurred in a newly evolved species in a relatively short time. They also believe it occurs when an organism colonizes a new area that contains few other species and adapts differently to fill niches in that area. Researchers use the example of the finches Darwin observed on the Galapagos Islands. He counted over a dozen different kinds of finches that he believed evolved from a single founding species.

(adaptive radiation is one type of this) —pattern of evolution in which species that once were similar to an ancestor
’s species diverge, or become increasingly distinct. An example would be bats, whales, and dogs —all mammals, but distinctly different.

—occurs when unrelated species occupy similar environments in different parts of the world. Because they share similar environmental pressures, and therefore, similar pressures of natural selection, they tend to have many of the same characteristics. An example would be whales and fish
—completely different but have similar features.

—occurs when two species live in close contact and have clear adaptations to one another’s existence.

Role of evolution in biological resistance:
New techniques in molecular biology have given researchers new insight into genetic mechanisms that may be involved in some types of directional selection. Remember that directional selection involves change from one phenotypic property to a new one. It refers to a trend that happens consistently over time. When a bed of oysters in Malpeque Bay (Prince
Edward Island, Canada) was infected with a lethal pathogen in 1915, it almost wiped out the oyster industry. But 10 years later, the oysters were making a comeback. By 1940, the
Malpeque Bay was producing more oysters than it ever had. They began to repopulate other areas that had been wiped out. What brought about this drastic change for the oyster?
Directional selection. Out of the 50 million or so offspring that were produced each year by the oysters, a fraction of those offspring carried an allele that was resistant to this pathogen. So when the environmental conditions were favorable for the offspring that carried this allele, the outcome was an increase in that variant in the population. This resulted in an increase in healthy oysters.
Many insects have developed a resistance to insecticides. Simple point mutations may be the process by which enzymes are modified so they are no longer susceptible to the insecticide. It has been discovered that in a swamp treated with a pesticide, the surviving mosquitoes had an amplification of the gene which does this. Over 250 copies were present in each diploid cell.
With this large number, the mosquitoes can make large amounts of an enzyme which results in detoxification the insecticide. This gene amplification has been observed in other arthropods, in mammalian tumor cells, and during cell differentiation. Biologists are not sure what exactly triggers or signals this process but they do know that once it starts, gene amplification takes on specific characteristics that enable it to perform its particular function.
Viruses are another organism that constantly evolve in response to changes in their environment. Some don’t change quickly, like smallpox or measles. This gave biologists time to create a vaccine against them. Others change very quickly, like the flu. The flu virus mutates rapidly, constantly changing its genotype and phenotype, so the flu virus changes year to year.
The body does not recognize the new virus as anything harmful, so it doesn’t send out anything to attack it. Another adaptation of viruses is that certain viruses can live in two or more different hosts. One virus may originally live in pigs and geese and then move on to live in humans and ducks. Viruses carry their genetic information on eight pieces of DNA. So if two strains of the virus infect the same cell, some of those genes will get mixed up, resulting in a new strain of the virus. This can cause major problems for the host.
—proposes that eukaryotes evolved through a symbiotic relationship among ancient prokaryotes.