EVS Chapter 4

Natural Selection 


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(1858, Darwin & Wallace) 

Shapes organisms

Acts as evolutionary mechanism

Acts on genetic variation 

1) Directional: drives feature in 1 direction
2) Stabilizing: produces intermediate traits, status quo preserved 
3) Disruptive: drives trait in 2 or more directions  

Biological Diversity
Area’s sum total of all organisms
Allopatric Speciation
Main mode.
Formation of new species due to physical separation of populations. 
-Ex: by mountains, glaciers, rivers
Sympatric Speciation

Populations reproductively isolated within the same area – reproduction leads to new group – gene pool alteration – reproduction of new group – can lead to new species


Hybridization and/or mutation 


Divergent Evolution
One species evolves in many different directions

Ex: Birds developing different beak shapes based on the food they eat. 

Convergent Evolution
Different species evolve towards one common form 

Ex: similarity in wings of insect, bird, pterosaur and bat. Trait is shared, but each evolved independantly  

Endemic Species

Can only exist in a specialized area. 

-Very susceptible to extinction 

-Usually have small populations 

Gaia Hypothesis
Through complex system of positive/negative feedback, life on Earth regulates planetary environment to help sustain life

Eutrophication Process

Nutrient over-enrichment, algal blooms, increased production of organic matter, ecosystem degradation 

Primary limiting factor of eutrophication is phosphorus availability 

Photic and Aphotic Zones in Lakes and Oceans

Photic: zone of intense sunlight 

Aphotic: usually deep waters, little or no sunlight 


Form of anaerobic respiration in methanogen microbes. The process absorbs carbon dioxide but emits methane, a significantly more potent GHG. 


Biological Pump

Oceanic sequestration of carbon from atmosphere -; deep sea. 

Cycling of organic matter produced by phytoplankton during photosynthesis. 

Cycling of calcium carbonate (CO3) 

Microbial Carbon Pump
Transformation of bioavailable carbon into pools of inert organic carbon deeper in the ocean.
Microbial Loop

Transformation of dissolved organic carbon into particulate organic carbon via heterotrophic bacteria. Recycling carbon back to food webs 

Zooplankton can access POM and not DOM