Theory of Evolution

Evolution: Undirected change over time.
Theory of Evolution: The process where existing life forms have evolved from earlier forms over a long period.

Lamarck proposed that by the use or disuse of organs, organisms acquired or lost certain traits during their lifetime.
These traits could then be passed to their offspring.
Over time, this process led to changes in a species.
Example: Giraffes stretched their necks out of necessity to reach higher leaves.

Served as a ship’s naturalist for 5 years on H.M.S. Beagle and kept a detailed journal describing the many organisms and fossils he found.
Wrote the famous Origin of Species in 1859.
Realized that natural variation exists in all species, and these differences can be passed to their offspring.
Evolution resulted from natural selection, including:
- Struggle for existence: Members of each species regularly compete to obtain food, living space, and other necessities.
- Overpopulation: More offspring are produced in a population than can survive.
- Fitness: The ability of an individual to survive and reproduce.
- Successful adaptations: Adaptations that aid in survival are passed on.
- Survival of the fittest: Those better suited to the environment survive to reproduce.
Natural selection results in changes over time in the inherited characteristics of a population, making the species more fit for the environment.
Descent with modification: Over long periods, each living species has changed to fill different environments.
Common ancestors: Species have evolved from common ancestors.

Cladograms show proposed ancestry according to shared traits.
Outgroup: The starting point organism with the least common characteristics with the other organisms.
The closer two species are on the cladogram, the more closely related they are proposed to be, and the more recently they evolved from a common ancestor.

Fossil Record: Remains of life found deep in earth’s crust, with the lowest layers being the oldest.
Geographic distribution of species: Similar organisms are found in different areas of the world.
Homologous structures: Organisms that seem to have similar structures used differently.
Comparative embryology: As an organism develops, it passes through similar stages.
Comparative biochemistry: Similar species have similar biochemistry; compares proteins such as hemoglobin molecules or compares DNA.
Vestigial structures: Structures with unknown use to an organism; potentially needed previously.

Mendel studied how genes were passed down from parent plant to offspring, noting genetic variation, dominant and recessive traits, and their alleles (TT, Tt, tt).
Darwin knew nothing about genetics.
Darwin's challenges:
1. Where did variations come from?
2. How were they passed on?
Species: A biological group whose members resemble each other and can mate to produce fertile offspring.
Population: Members of a species that live in the same area.
Gene pool: The combined genetic information of all members of a population, typically with 2 or more alleles.
Gene frequency: How often a particular allele occurs in a population.

Natural selection: A selective pressure in nature leads to changes in allele frequencies within populations. Those more fit for the environment have a better chance at survival (e.g., Peppered moth).
Gene Flow: A change in alleles due to individuals with different genes moving into and out of the population.
Migration: Movement of organisms into or out of a population.
Sexual Selection: Some traits are more desirable but don’t necessarily make the organism more fit for survival; it just increases their chance to pass on traits by attracting mates.
Genetic Drift: A change in gene frequency of a very small population due to chance.
Mutation: Any alteration of the DNA sequence, which can cause variation in the population of a species.

Isolation: Separation of populations into groups that no longer interact, resulting in different gene pools, causing the two populations to diverge (become more different).
- Geographic isolation: Separated by geography.
- Genetic/reproductive isolation: After species have changed, they aren’t able to interbreed.
- Behavioral isolation: Two species don’t reproduce because they act differently.

Evolutionary change within a species, primarily through natural selection.
Changes can give the organism an advantage, allowing it to live longer and reproduce more (e.g., camouflage).

Life and the universe could not have arisen by chance but was designed and created by an intelligent entity.
Teleology: Since nature has a design and purpose, something beyond nature must have given it that purpose.
Biblical Creationism: Creation of mankind, nature, and the universe by God.

Describing, ordering, and naming living things, not necessarily the same as “kind” referred to in the Bible.
The need for classification in science is due to the diversity of living things; they must be organized to be studied.
Done on the basis of similarities of structure & evolutionary history.
3 Domains: Archaea, Bacteria, and Eukarya (ABE).
- Archaea & bacteria are prokaryotic = No nucleus, no membrane-bound organelles, reproduce asexually.

Binomial Nomenclature: Living organisms are given a two-part name:
- First part = Genus - includes similar species.
- Second part = species.
Names are generally in Latin, italicized or underlined, with the first name capitalized but the second lowercase.
Examples:
- domestic cat = Felis domesticus
- lion = Felis leo
- tiger = Felis tigris
- Man = Homo sapien