7. Rates of Evolution Flashcards
Anagenesis
Evolving into another species over time
Cladogenesis
Evolving into two or more species over time
Creeps
Gradual speciation
Jerks
Punctuated equilibrium
Gradual Speciation
- Species arise slowly overtime
- Many morphological intermediates
Intermediate Forms
Evolutionary steps between ancestral species/traits and the current species/trait
Evolution of eye - evidence
- Fossils of intermediate eyes found
- Intermediate forms can persist in species
- Some alive today - eyespot
Punctuated Equilibrium
- Species diverge quickly
- After quick divergence, remain unchanged for a long time
- Single or few mutation in short period of time - De novo
- Mutation sever to be noticeable but not deleterious or lethal
- Must be geographic or reproductive isolation
Tiger Salamander
Example of punctuated equilibrium
- Terrestrial
- Single gene mutation caused it to stay as larval stage(aquatic)
- Can become adult form under extreme stress but unable to reproduce
Quantum Speciation
Unexpectedly rapid speciation
- Only seen in punctuated equilibrium
- Often in small population with founder’s effect and genetic drifting
- ex. Big bird lineage of finch - 2 generation
Frequency of gradual vs punctual
Biased
- If intermediates are missing
When looking at species that diverged recently or long ago
Living fossils and evolution
No clear answer
One clear relationship
- If habitat remains stable - species also remain stable
Trait evolution
The evolution of traits - no relation to species
- can be a trait found in many different species
Likelihood of mutation
Severe mutation adding novel traits are rare
- Axolotl is a very rare case
Trends in Trait Evolution
Complexity increase?
- only early unicellular to eukaryotes
Complexity
Not clear
One definition
- Number of unique individual organs or traits in an organism
Specialization
A species losing general traits to become better adapted to a very specific habitat
- Re-evolving traits thought to be very rare
Irreducible complexity
Traits whose function have become essential to life, losing them seems impossible
Selective ratchets (irreducible complexity)
Traits not easily dispensed due to their role in functional integration
- Notochords - Used to be structural support but in vertebrates they don’t - They facilitate the development of spinal column
Key Evolution
Novel and sudden phenotypic adaptation to one or more ecological zones
- Enables great diversity in a lineage
- Seeds in plants
Taxonomic rates of evolution
The rate at which taxa evolve
- The most common definition of evolution
Adaptive radiation
Relatively rapid speciation and evolution event
- Seems to correlate with a sudden abundance of open niches
Ecological niche
The specific place a species hold in its environment, and the role it plays in the food chain of that community
- Interaction between the abiotic and biotic factors
- Two species can hold the same niche
Ways of creating new niches
Mass extinction
Development of new traits that create new, unexploited niches
Modification of habitat
- Ecosystem engineering - Beavers
Mass Extinction
An extinction event which extinction vastly exceeds the historical background rate of species extinction
- Severe climate change
- 5 observed
End-Cretaceous Extinction
Extinction of Dinosaurs
- Led to empty niches
- Adaptive radiation of mammals
- Small size - Fast reproduction
- Generalist - Eat anything
Angiosperm
Adaptive radiation after emergence at expense of other groups
- Coevolution with pollinators
- creation of niches through ecosystem engineering
Angiosperm and pollinator
Flowers - attract pollinator
- Travel further
Angiosperm and niches
Grow faster than conifers - main plant back then
- Many annual species too
Ecosystem engineering
- Decomposition of angiosperm makes soil neutral - benefits angiosperm
Evolution rate
No general rules
- Few patterns
