Module 2 - Natural Selection Flashcards
Aristotle’s “the chain of being”
Living world is unalterable; ladder of life
Age of Enlightenment
Earth was older than initially believed!
Jean-Baptiste Lamarck
- diversity of life shows the age of earth
- adaptation is a primary product of evolution
- WRONG - acquired traits can be passed down, used structures get bigger and vice versa
Charles Lyell
Principles of Geology; earth has been shaped by slow action of rivers, earthquakes etc.
Charles Darwin
“Decent with modification” - natural selection is a driving force in evolutionary change
Darwins core concepts
All species have the ability to overproduce
Resources are limited -> struggle for survival
Individuals less suited for the environment are less likely to survive
Natural Selection
Individuals have certain inherited traits tend to survive and reproduce better because of those traits
What is changing in populations over time?
Allen frequencies of a gene pool
Gene
A unit of heredity transferred from parent to offspring
Gene pool
All genetic information in the individuals population
Allele
1+ variants of a gene
DNA
Molecule carrying genetic instructions of all known organisms
Evolution
A change in allele frequencies in a gene pool
What is changing in evolution
DNA (physical/behavioral characteristics); alleles
4 mechanisms of evolutionary change
- mutations
- gene flow
- genetic drift (chance events)
- natural selection
Mutations
Random events; can be beneficial, harmful, neutral
Ways mutation can occur (2)
Spontaneous - a result of biological and chemical process
Induced - external factors (ex. Radiation)
Gene flow
Exchanges alleles between two different populations (can introduce or remove alleles from a given population) *homogenizing force
Genetic drift
Chance events cause unpredictable fluctuation in gene frequencies (impactful in small populations)
Founder effect
When a small part of a larger population is established
Population bottleneck (genetic drift)
Sharp reduction in size of a population; can reduce genetic variation
Natural selection types (3)
Directional, stabilizing, disruptive
Directional selection
Individuals with an advantageous trait that leans towards one extreme
Stabilizing selection
Individuals with an average inherited trait are advantageous
Disruptive selection
Individuals with either extreme of an inherited trait are advantageous
Sexual selection
Traits which are good at securing a mate are over-represented (peacock feathers)
6 lines of evidence for evolution
- fossils
- traces of evolutionary history in existing organisms
- similarities and differences in DNA
- direct observations of genetic change in populations
- the distribution of organisms and fossils around the world
- present day formation of new species
Homologous traits
Traits shared between groups of organisms because of their decent from a common ancestor
Vestigial structures
Body parts that had served a purpose in ancestral species but currently not useful
Convergent evolution
When natural selection causes similar phenotypic structures not due to a common ancestor
Analogous traits
Traits shared between organisms because of convergent evolution
Macro evolution
Evolution above the species level
Micro evolution
Smaller evolutionary changes (alleles within a species or population)
Speciation
When one species becomes a new species, reproductively isolation
Pre-zygote barriers (5)
- temporal
- ecological/habitat
- behavioral
- mechanical
- gametic
Post-zygote barriers (3)
- zygote death
- hybrid infertility
Hybrid breakdown
Allopathic speciation
Geographical isolation
Sympathize speciation
Hybrids (not geographical); individuals of the same population become different over time
