Evolution
Fossils
The remains or impression of a prehistoric organism preserved in petrified form
Fossil Dating
Techniques to determine how old a fossil is
Relative Dating: comparing to similar fossils of known ages (index fossil)
Absolute Dating: using radiometric dating techniques
Fossil Formation
Original fossil: actual remains of an organism, such as teeth or bones
Replacement fossil: permineralization occurs when minerals replace the hard structure itself (petrified form)
Carbon film fossil: an outline formed from the carbon residue of soft-bodied organisms that have been buried
Mold and cast: formed when flowing water removes the original fossil leaving just the impression (mold) and sometimes minerals replace the space (cast)
Trace fossils: items that record activity of an organism encased in a material that preserves it(such as nests, burrows and leaf imprints)
Preserved fossils: an entire organism encased in a material preserves it (such as ice, volcanic ash and amber)
Law of superposition
The geologic principle used to determine the relative ages of rock layers. States that in horizontal layers of sedimentary rock, the oldest rock layer will be on the bottom and the youngest at the top.
Selection
Artificial Selection: The concept of enhancing specific traits in an organism for future generations
Natural Selection: A natural process by which species that have more beneficial traits tend to survive and reproduce at higher rates, thus overpowering the individuals from the same species with traits less fit for survival
Darwin's 5 Step Natural Selection Theory
- Struggle for existence
- Variation in traits
- Different survival and reproduction
- Inheritance
- Time
Sexual Selection: Type of natural selection in which mating preferences influence the traits of the organism
Evolution by Random Process
Mutation
A random change in a gene that creates a new trait that causes genetic variation in a population.
Genetic Drift
Founder's Effect
Bottleneck Effect
A change in the genetic composition of a population as a result of random mating
Change in a species caused by a small number of colonizing individuals
A reduction in the genetic diversity of a population caused by a decrease in size
Evidence of Evolution
Fossil Record
Comparative Anatomy
Genetics and Biochemistry
Geographical Distribution
Chronological collection of life's remains in sedimentary rock layers that displays evolutionary changes (incomplete as fossilization is rare)
The comparison of body structures in different species
Homologous Structures: Structures that possess similar underlying anatomy as a result of a shared evolutionary origin
The comparison of complete genome sequences and amino acid composition of different species
The distribution of species over geographical areas and shows that closely related species are found in close proximity
Analogous Structures: Structures adapted to possess similar features and functionality as a result of exposure to common selective pressures, but with different origins
Vestigial Organs: The presence of functionless and reduced remnants of organs once functional in ancestors due to environmental changes
Comparative Embryology: Embryos with similar stages of development are typically closely related organisms
Types of Evolution
Divergent Evolution
When two or more species sharing a common ancestor become more different over time
Convergent Evolution
Parallel Evolution
When two or more species sharing a common ancestor become more similar over time
When two or more species sharing a common ancestor evolve in constantly similar ways
Human Evolutionary Changes
Primates
forward eyes, pentadactyl digits, opposable thumbs, nails, large brains, flexible skeletons and rotatable arms
Skeletal Changes
Skull Changes
Less pronounced brow ridge
Developed an upright stance (bipedalism)
Larger brain capacity
Shorter arm to leg ratio
'S' shaped spine as opposed to bow shaped
Smaller jaw and teeth
Flatter face