Species Concepts
This species concept is most limited when applied to organisms that reproduce asexually or are known only from fossils.
What is the Biological Species Concept?
A shift in allele frequencies due to natural selection, mutation, or genetic drift within a population describes this level of evolution.
What is microevolution?
Speciation caused by a physical barrier such as a mountain range or river is known as this type.
What is allopatric speciation?
Barriers that prevent mating or fertilization from occurring at all belong to this category.
What are prezygotic barriers?
Offspring produced by mating between individuals of two different species are known as this.
What are hybrids?
Two populations look nearly identical but occupy different ecological niches and never compete directly for resources; this concept would most likely classify them as separate species.
Ecological Species Concept
The origin of mammals from reptile-like ancestors over millions of years is an example of this evolutionary scale.
What is macroevolution?
The formation of a new species through chromosome duplication without geographic separation is an example of this type of speciation.
What is sympatric speciation?
Two species of insects breed in the same area but during different seasons, preventing interbreeding.
What is temporal isolation?
A mule’s inability to reproduce demonstrates this postzygotic barrier.
What is reduced hybrid fertility?
This species concept relies heavily on observable traits and was historically used before genetics and reproductive data were available.
What is the Morphological Species Concept?
This evolutionary process often exaggerates traits that may reduce survival but increase mating success.
What is sexual selection?
Plant species often undergo rapid sympatric speciation due to this genetic mechanism.
What is polyploidy?
Differences in courtship songs or mating dances are examples of this isolating mechanism.
What is behavioral isolation?
When hybrid offspring fail to develop properly or die early, this barrier is responsible.
What is reduced hybrid viability?
According to the biological species concept, which two conditions must be met for individuals to be considered the same species?
What is the ability to interbreed and produce fertile offspring?
Which evolutionary scale is directly responsible for the formation of new species?
What is macroevolution?
When populations diverge because they occupy different microhabitats within the same environment, this process may lead to speciation.
What is habitat differentiation?
Incompatibility of reproductive organs between species represents this prezygotic barrier.
What is mechanical isolation?
This postzygotic barrier occurs when second-generation hybrids show reduced fitness.
What is hybrid breakdown?
Early taxonomists relied on this species concept before genetics and reproductive isolation were understood.
Morphological Species Concept
Microevolutionary changes accumulated over long periods can ultimately lead to this broader evolutionary outcome.
What is macroevolution?
Which type of speciation is most likely when gene flow is completely cut off between populations?
What is allopatric speciation?
Reproductive barriers that act after fertilization has occurred fall under this category.
What are postzygotic barriers?
A geographic area where closely related species meet and produce hybrid offspring is called this.
What is a hybrid zone?