Lesson 8: Evolution Flashcards
Evolution
Inheritable change in species over time (the result)
Natural Selection
When the environment favors certain traits and selects them, allowing those that have them to survive and pass them on (the process)
Species
A group of organisms that breed with each other and produce fertile offspring in the wild (can be somewhat subjective)
Adaptation
Any trait that allows an individual/group a better chance at surviving and reproducing
Fitness
The reproductive success of an organism (# of species)
Microevolution
Small changes (based on variation) that occur within a species
Macroevolution
Change that occurs as a new species evolves and old species become extinct - can lead to speciation
Evolution Misunderstandings
- Natural selection cannot produce perfection; it is limited by historical constraints
- Evolution doesn’t make new traits; it only improves existing traits
- Adaptations are often compromises
- Luck plays a big role in evolution
- Individuals can’t evolve; populations do
- Evolution is not intentional/purposeful
- Evolution is situational
Evidence for evolution
- Fossil Record
- Biogeography
- Anatomy
- Molecular Biology
- Experiments
Fossil record
➜ specific order which fossils appear within geologic layers
● remains or evidence of organisms preserved in rock
● change over time (evolution) is visible when looking at fossils for the various species of life on this planet
➜ Ex. Archeopteryx linked dinosaurs and birds
➜ Ex. Australopithecus afarensis or “Lucy” linked humans and chimpanzees
● There are many “gaps” in the fossil record due to undiscovered and unfossilized species
Biogeography
➜ Species that are geographically close to one another are more genetically related
➜ Ex. Darwin’s finches
Anatomy
● Homologous structures - Similar structures that serve entirely different functions; shows divergent evolution
● Analogous structures - Same function but very different structures; shows convergent evolution
Anatomical Evolution:
➜ Derived traits - Traits that have recently evolved within a species (new)
➜ Ancestral Traits - Traits that are “left over” from a previous species’ evolution (old)
➜ Vestigial Traits - Ancestral traits that are no longer functional/useful (old + useless)
● Embryologic Development - Development is similar for many different organisms (suggesting out common ancestor)
Molecular Biology
● Most genes are found in all living organisms
● More closely related species share more genes
● The genetic code (DNA and RNA) is universal
● Most genes are conserved through evolutionary history
● The more genetic differences between 2 species, the longer they “speciated”
➜ Ex. Hemoglobin amino acids sequences
Experiments
● Scientists are constantly performing experiments to test and support evolution
➜ Ex. Peppered moth experiment
5 Mechanisms of Microeveolution
- Natural Selection - The environment selects for a certain trait/allele, changing allele frequency
- Genetic Drift - Change in allele frequency due to chance - no “selection” takes place
2A. Bottleneck Effect - A random event (natural disaster) drastically reduces population size, leaving a random set of alleles in population - Gene flow - when fertile individuals or gametes (i.e. pollen) migrate to another population - this reduces genetic differences between populations
- Mutation - a random change during transcription or translation that results in a new allele
- Sexual Selection - When mates are chosen and not randomly selected within a population
