Evolution
Microevolution
Definition: A change in gene frequency within a population.
Occurs over short periods of time, like from one generation to the next.
Example: Mosquito's evolving resistance to DDT.
Macroevolution
Definition: Evolution above the species level.
Those small changes build up over millions of years
Patterns we see when looking at the large-scale history of life
Life on Earth has been accumulating small changes for 3.8 billion years.
Examples: Origin of mammals and radiation of flowering plants
Example: HIV strains evolving resistance to antiviral medication
Example: Flu Season
Mechanisms
Mutation
Change in DNA
Migration
Genetic Drift
Natural Selection
Random(beneficial, harmful, or neutral)
Some individuals leave descendants by chance
Unlike Natural selection, an advantageous trait is not necessarily being selected for.
Also know as Gene Flow
Movement of individuals(and their genetic information) from one population to another
Occurs because their is variation, heredity, and the environment cannot sustain unlimited population growth.
Evidence for Evolution
- DNA sequence
- Amino Acid sequences(even when DNA sequences are slightly different)
- Patterns in the fossil record
- Pattern of Anatomical similarites
- Pattern of Embryological Similarites
Intro to Evolution
Evolution: Change in a population over time.
NOT a change in an individual
Individual=1 organism
Population: group of individuals of the same species that live in the same area and reproduce with one another.
Fossil Evidence
Traditional form
organisms that show the intermidate states between an ancestral form and that of it decendants
Relative dating
Compating fossils' afes by where there are found in the Earth(superposition)
Radioactive dating
Radioactive elements in fossils or sediments surrounding fossils
Comparative Anatomical Evidence
Homologous structures
similar structures in related organisms that are a result of common ancestry
Vestigial structures
little or no purpose to present organism, but provide evidence for common ancestry
Homologous
characters in different organisms that are similar because they were inherited from a common ancestor that also had that character
Common ancestry/descent
when one species is the ancestor of two or more species later in time
Analogous
have separate evolutionary organisms, but are superficially similar because they have both experienced natural selection that shaped them in a similar way
Convergent evolution
process in which two distinct lineages evolve a similar characteristic independently of one another
Embryological evidence
homologous structures observed during early embryological development
these homologous structures may not be visible in the fully developed organism
Molecular evidence
DNA sequences
Amino acid sequences
chromosomes
gene expression
Mutation
A change in a DNA sequence
the ultimate source of genetic variation random
Random
can be beneficial, neutral, or harmful for the organism, but mutations do not try to supply what the organism needs
Migration/gene flow
gene flow=migration
movement of individuals, and their genetic material, from one population to another
Genetic Drift
genetic drift affects the genetic makeup of the population but, unlike natural selection, through an entriely random process
does not work to produce adaptions
in each generation, some individuals leave behind a few more descendants than other individuals
Natural selection
Carrying capacity
Whent he above 3 criteria are met, evolution by natural selection will is occurring
Heredity
Variation of traits
Adaption
A feature that is common in a population because it provides some improved function
well fitted to their function and are produced by natural selection
mimicry of leaves by insects is an adaption for evading predators
Adaptive radiation
A single species evolves into a number of other species
these species are distinct from one another but are closely related
each species is specialized for a different environment
Sexual selection
acts on an organisms ability to successfully copulate with a mate
sexual selection is often powerful enough to produce features that are harmful to individual's survival
sexual selection makes many organisms go to extreme lengths for sex
Artificial selection
people select which organism get to reproduce
farmers and breeders allow only the plants and animals with desirable characteristics to reproduce
Co-evolution
cases where two species reciprocally affect each other's evolution
likely to happen when different species have close ecological interactions with one another
Speciation
species
a population of similar organisms that can interbreed to produce viable, fertile offspring
a lineage -splitting event that produces two or more separte species
branching points on phylogenetic tress are speciation events
geographic isolation is an important step or some speciation events
microevolution
small scale, single population
macroevolution
grand scale, across species