Evolution Flashcards
4 basis of natural selection
1) heritable variation
2) competition for resources
3) reproductive success varies
4) organisms adapt with environment
Mechanisms for modification
Gene variation
Pressure at individual level
Gene
Unit of heredity
Passed from partner to offspring
Genetic fitness
Individuals ability to reproduce relative to others.
More for= ability to spread more genes
Adaptation
Evolve trait better visited to environment. Result of natural selection.
Traits between two species link them together. Share a common ancestor
Transitional species
Linked fish and amphibians
Tetrapods
Similar structures
inherited from common ancestor
Homologous structures
Similar structures
Originated independently
Analogous structures
Structure important for ancestor
Remains in derived species
Vestigial structures
Antibiotic resistant bacteria
Staphylococcus aureus
Penicillin and methicillin resistant
Biogeographic evidence
Similarities in global strata
All continents were connected and split apart
Marsupials in Australia
Egg laying- marsupial pouch- placenta
Placental mammals outcompeted marsupials in South America.
Species definition
Group of same kind of organism in a population
May breed to produce viable offspring
Do not breed with other kinds
Speciation
Formation of two species from one
Allopathic speciation
Geographic isolation. Physical barrier
Adaptive radiation
Sympatric specidtion
Within same area
Gene flow
Sexual selection
Habitat differentiation
Gene flow types
Polyploidy: >2 chromosome copies
Autopolyploid: cell division error. Tetraploid cells. Self pollination
Allopolyploid: Asexual reproduction. Interbreeding with sterile hybrids.
Pre-zygotic barriers
Temporal
Habitat
Behavioral
Mechanical
Gametic
Habitat isolation
Pre zygotic Limit mating
2 species with 2 habitats within same area. Rare encounters
Temporal isolation
Pre-zygotic prevents mating
Seasonal breeding.
Behavioral isolation
Pre-zygotic Prevents mating
Specific mating rituals
Mechanical isolation
Pre-zygotic prevents fertilization
Mismatched anatomy prevents fertilization
Gametic isolation
Pre-zygotic prevents fertilization
Morphology of sperm or biochemical barrier.
Post zygotic barriers
Hybrid viability: low hybrid survival rate
Hybrid fertility: sterile hybrids due to chromosome numbers differing
Hybrid breakdown: first generation may be fertile, but 2nd is sterile
Hybrid patterns
Spatially overlap zone. Patches and boundary overlap. Alleles change within zone. Hybrids have more developmental problems.
Hybrid Environment
Climate change shoots hybrid zones and provide buffer to climate change.
Results of hybrids
Temporary reconnection re-establishes gene flow. Real time speciation
Hybrid reinforcement
Strengthening reproductive barriers.
Reinforced sympatric speciation
Changes occur via natural selection.
Hybrid fusion
Wearing of reproductive barriers. Gene pools become more similar
Biodiversity decreases
Stability
Continued formation of hybrid individuals
Many hybrids despite low success rate because both species often enter hybrid zones.
Narrow zone= more hybrids
Wider zone= less hybrids
Time for speciation
4,000 years- 40 mil years
Average 6.5 million years
Speciation punctual model
Short speciation. Prolonged stabilization.
Abrupt extinction
Speciation gradual model
Small incremental changes over entire time period. Produced two species
