EEMB 2290 Study Guide - Midterm Guide: Ecological Niche, Reproductive Isolation, Invasive Species
Introduction to Evolution
Reading list # 3
Topic: Speciation, reproductive isolation, extinction
Vocabulary:
Microevolution
Macroevolution: grand scale evolutionary change
- Origin of new taxonomic groups
- Evolutionary trends
- Adaptive radiation
- Mass extinction
“Species”
Biological species concept
A population whose members can potentially interbreed in nature to produce viable, fertile offspring
Fundamentally based on the idea of reproductive isolation (no interbreeding, no viable offspring =
reproductive barriers)
Limitations:
• Does not apply to asexually reproducing organisms (i.e. bacteria)
• There are organisms that can interbreed in spite their morphologically and ecologically distinct
traits (i.e. grolar bears!)
Morphological Species Concept
Distinguishes a species by body shape, color and other structural features. This concept
can be applied to asexual organisms
Does not require knowing the extent of gene flow
Limitations:
• The criteria are subjective (the researcher decides which traits are important (not all researchers
agree
• Sexual dimorphism
• Humans
Biological species concept
Morphological Species Concept
Ecological Species Concept
Phylogenetic Species Concept
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Ecological Species Concept
Based on where the organisms live and their abiotic and biotic interactions with their environment
(ecological niche)
Organisms that occupy different niches are considered different species even if they could interbreed
Limitations:
• Invasive species
• Different migration patterns due to global warming
Examples: cane tod(frog), that eat everything and grow really big; Asian Longhorned Beetle;
The Burmese Python; Nile Perch (giant fish); Kudzu vine (plant)
Enemy RELEASE Hypothesis: States that a species, on introduction to an exotic region, experiences
a decrease in regulation by natural enemies (i.e. predators, pathogens, herbivores etc.), resulting in a
rapid increase in the distribution and abundance of the introduced species.
Phylogenetic Species Concept
The smallest group of individuals that share a common ancestor forming one branch of the tree of life
Based on morphological and molecular (i.e. DNA sequence) similarities
Limitations:
• Determining the degree of differences required to indicate separate species (what is the
permissible level of genetic variability? Phenotypic plasticity?)
Mechanisms of
Reproductive isolation
Pre-zygotic: geographic, habitat, ecological, temporal
isolation, behavioral isolation, mechanical isolation,
gametic isolation
Post-zygotic: reduced hybrid viability, reduced hybrid
fertility, hybrid breakdown
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Speciation
• Speciation is at the boundary between microevolution and macroevolution.
• While the changes after any speciation event may be subtle, the cumulative change over
millions of speciation episodes must account for macroevolution, the scale of changes seen in
the fossil record
Two requirements:
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Document Summary
A population whose members can potentially interbreed in nature to produce viable, fertile offspring. Fundamentally based on the idea of reproductive isolation (no interbreeding, no viable offspring = reproductive barriers) Phylogenetic species concept: does not apply to asexually reproducing organisms (i. e. bacteria, there are organisms that can interbreed in spite their morphologically and ecologically distinct traits (i. e. grolar bears!) Distinguishes a species by body shape, color and other structural features. This concept can be applied to asexual organisms. Does not require knowing the extent of gene flow. Limitations: the criteria are subjective (the researcher decides which traits are important (not all researchers agree, sexual dimorphism, humans. Based on where the organisms live and their abiotic and biotic interactions with their environment (ecological niche) Organisms that occupy different niches are considered different species even if they could interbreed. Invasive species: different migration patterns due to global warming. Examples: cane tod(frog), that eat everything and grow really big; asian longhorned beetle;