L12: Macroevolution of Birds & Dinosaurs

Difference between micro and macroevolution

micro = evolution between population
macro = evolution between species (species rather than individuals)

Adaptative Radiation

an evolutionary process where species rapidly splits into many different new species (leading to rapid diversification in adaptative rates) because a bunch of new survival opportunities and niches open up

What can adaptative radiation arise from? And key drivers?

• Colonization of a new location (Darwin’s finches)

• Key innovations (pharyngeal jaws in Cichlid fishes)

• isolation on an island

• extinction of a competitor

• the formation of the new habitats

Consequences of Adaptive Radiation

• Cambrian radiation of animal

• Devonian radiation of plants

• Cretaceous radiation angiosperms

Convergent Evolution

similar adaptations in distantly related organisms that live in similar environments
→ this leads to analogous structures

Analogous structures

similar functions but different evolutionary origins

Name at least 2 analogous structures

• Insect wings v. bird wings (similar functions but different origins)

• Dolphins fin v. shark fins

• Cat tails v. cheetah tails (one for balance and speed)

What’s the one single marsupial species native to the U.S.?

the Virginia possum

Marsupial species

pouched animals that give birth to undeveloped young (who typically grow inside a pouch)

What can we learn from fossil records?

• Hypothesize about evolutionary processes by using phylogenetic trees to compare to extant (still living) species

• Understand molecular basis of phenotypic traits and how certain genes are may have evolved

• comparing with living organisms

What can we not learn from fossil records?

• Anatomical information about most parts of most organisms

• Detailed information on evolutionary events within species and populations and interactions

Mass Extinction

periods of high extinction rates that reshape evolution, eliminating dominant groups and creating new spaces for surviving species

What extinction period was the most severe, resulting in the loss of >90% of the species, leading to the raise of new groups like dinosaurs?

End-Permian

Phyletic Gradualism

species change SLOWLY and steadily over long periods of time through the gradual accumulation of SMALL changes

Punctuated Equilibrium

species remain relatively unchanged for long periods, interrupted by brief, RAPID episodes significant change with allopatric speciation events

(a sudden environment change or geographic split triggers a fast burst of new trait and creates a brand-new species)

Allometry (of Sexual Selection) + Name example

Differential growth of some body parts in relation to others (instead of everything growing at the exact same rate, different part grows at different rates)

Forced characteristics and traits that are emphasized and exaggerated

• Example: Male fiddler crab’s claw

Heterochrony (of Sexual Selection)

Acceleration OR delay of certain developmental processes compared to its ancestors

• Example: reproductive systems envelope faster so that early characteristics are able to reproduced → Red eyed tree frog

Name the evidence that birds and dinosaurs are related

• The closest known example: Archaeopteryx

• Shares morphological features and behavior 

• First it has a beak, wings, and it has feathered 

• Similar behavior; uses feathers for thermoregulation, and dancing (to attract mates)

Gene Recycling

existing genes or genetic material are repurposed to form new genes (instead of creating them from scratch)

Name at least 2 examples of gene recycling

• Pigment gene (originally for dark pigment, repurposed for UV protection or camouflage)

• The grape leaf tendril: coded for leaf but genetically modified for plant balance, grip, etc

Hybridization

the merging of genes from different species through hybridization can create new species with a mix of characteristics