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Ch. 23: Macroevolution (What does Macroevolution Tell Scientists? (New…

- - - - Plate tectonics
        
        This is the theory that continents are part of great plates of Earth’s crust that float on the hot, underlying portion of the mantle
        
        Continental drift is where movements in the mantle cause the continents to move slowly over time
        
        Continental drift results in:
        
        Altered habitats
        
        Climate change due to new location
        
        The promotion of allopatric speciation on a grand scale
        
        Causes extinction of species as well as new growth opportunities for organisms surviving a change
      - Mass extinctions
        
        Defined as the elimination of a large number of species throughout Earth, and is the result of global environmental changes
        
        5 mass extinctions have occurred within the past 500 million years resulting in the majority of species that ever lived to now be extinct
        
        Consequences of Mass Extinctions:
        
        It severely disrupts interactions in an ecological community.
        
        It changes types of organisms in community affecting species interactions
        
        Species go extinction meaning their evolutionary lineage is gone forever
        
        It takes millions of years to recover the previous levels of diversity
        
        It promotes adaptive radiation where new groups of organisms fill empty niches and diversify
      - Adaptive radiations
        
        More on this in a separate branch!
- - - - After a mass extinction
        
        Ex: After dinosaurs went extinct mammals greatly expanded in diversity and size to fill empty niches
      - When a group of organisms has a major evolutionary innovation (ex: seeds, armored body covering)
        
        Ex: After land plants developed adaptations like waxy leaf coats and stems to fight gravity, they were able to fill new niches
      - When a group of organisms colonizes regions in which they face little competition from other species
        
        Ex: When plants colonized and diversified on land, it stimulated AR in insects that ate or pollinated plants
    - - Mass extinctions
      - Major evolutionary innovations
      - Diversification of another group of organisms (which can provide new sources of food)
      - Migration to new locations where few competitor species exist
- - - - Mutations, or Changes in Gene Sequences
        
        Results from the process of duplication and divergence
        
        The original gene still exists and functions allowing for survival, but the new copy is free to accumulate mutations and possibly even new function(s)
        
        This picture demonstrates an example using the Artemia Ubx gene
        
        This gene promotes leg formation in the trunk of the body however mutation occurred in the nucleotide sequence resulting in a new gene (Drosophilia Ubx) that suppresses leg formation in the trunk
      - Changes in Gene Regulation
        
        Gene regulation controls when, where, and how long a gene is expressed or allowed to function, so changing it can have significant effects
        
        This picture demonstrates an example using threespine stickleback fish
        
        Here the marine species have spines on the lower surface that is made of calcium. In lake species however, there are no spines because calcium is used for other purposes. The Pitx1 gene is the same for both species but the gene regulation is different. The marine species express it in the spine and mouth regions while lake species express it only in the mouth region.
- - - - Based mostly on the sequence in which fossils accumulate in sedimentary rock layers called strata