Lecture 14: Adaptive Radiation Flashcards
What is Adaptive radiation?
Evolutionary changes shape traits allowing organisms to adapt to their environment, and convey fitness advantages
What is the radiation part of adaptive radiation?
Many species coming from a common ancestor over a short timeframe
What is a niche?
The specific place a species holds in its biotic and abiotic environment.
No two species can hold exactly the same niche in the same environment. One always outcompetes the other.
Wha are some ways new niches open/are created?
Key innovation traits create new unexploited niches
Dispersal to a new environment (like a lake or island)
A mass extinction event kills a population within a niche, opening, it up to a new population
Modification of habitat due to ecosystem engineering (ex: beaver dams)
How does extinction affect radiation (in mammals)?
Mass extinction causes the loss of dinosaurs = abundance of empty niches which led to incredible adaptive radiation in mammal specie resulting in the domination of mammal species today
What is darwin’s theory on adaptive radiation?
Single colonizing finch species gave rise to many species that evolved to fill diverse open niches.
What were some key features of mammals that allowed them to adapt quickly?
Small, rapid reproduction, good nutrition for babies (milk), diverse diet, could be nocturnal
What was the Cambrian Explosion?
Massive radiation of new animal forms during the Cambrian era –> rapid emergence of new traits (hard bodies, predation, eyes)
Explain adaptive radiation in terms of angiosperms?
Flowers attract pollinators –> major diversification of angiosperm pollinators along with angiosperms created new pollination niches and a decline in other pollinators
What is convergent evolution?
independent evolution of analogous traits (structures, functions, behaviors) in two or more lineages (ex: bird wings vs bat wings vs insect wings all evolved separately but all allow flight).
What is the evidence of convergent evolution?
Map a trait on a phylogeny and look for presence of the trait in fossil ancestors
Explain mimicry in terms of convergent evolution.
a non-toxic species evolving to resemble an unrelated toxic/dangerous one to deter predation
What is parallel evolution?
Similar development of a trait in distinct species that are not closely related, but share a similar original trait, in response to similar evolutionary pressure.
Give an example of parallel evolution
Placental mammals and marsupials diverged 100 million years ago but each lineage developed similar forms on different continents after they diverged to fill similar niches.
What is the founder effect?
A type of genetic drift that occurs when a new population is established by a small group of individuals from a larger source population
What is genetic bottlenecking?
a significant reduction in a population’s size, resulting in a decrease in genetic diversity –> a mutation in a small gene pool has a much larher affect compared to a large population (1/30 vs 1/300)
