1.1 Flashcards
What is the definition of a species according to Mayr’s Biological Species Concept?
Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.
This definition emphasizes reproductive isolation as a key factor in defining species.
What is the Morphological Species definition?
A set of organisms sharing structural similarities between members and discontinuities in structure between different species.
This definition focuses on the physical characteristics of organisms.
Why is speciation important for biologists?
Speciation is evidence that evolution occurs and provides insight into mechanisms of evolution, distribution patterns of organisms, and patterns in ecology and reproductive biology.
Understanding speciation helps clarify how species evolve and adapt over time.
What is Cladogenesis?
Cladogenesis is a splitting event that creates two or more distinct species from a single ancestral group.
How does isolation affect speciation?
Active gene flow between populations eliminates genetic differences among them.
When gene flow stops, mutation, selection, and drift lead to independent evolution.
What are the four steps leading to Allopatric Speciation?
- A single species is an interbreeding reproductive community.
- A barrier develops or a dispersal event occurs, dividing the species.
- Separated populations diverge through gene and trait differences.
- Populations become so different that interbreeding does not occur if they overlap again.
What is an example of Allopatric Speciation?
Speciation of squirrels in the Grand Canyon.
This illustrates how geographic barriers lead to speciation.
What is Sympatric Speciation?
Speciation without any geographical isolation within the continuous ancestral population.
It occurs through changes in behavior, microhabitat, seasonality of breeding, or chromosomal mutation.
What is polyploidy and its significance in speciation?
Polyploidy is a type of mutation that can lead to isolation between populations and is thought to account for 80% of today’s plant species.
Fill in the blank: Sympatric speciation occurs in populations that occupy the ______ geographic area.
same
What are prezygotic isolating mechanisms?
Mechanisms that make interbreeding unlikely to occur before fertilization.
Examples include behavioral isolation and temporal isolation.
What are postzygotic isolating mechanisms?
Mechanisms that cause hybrids to become sterile or to fail to develop properly.
What is a hybrid zone?
Areas where interbreeding occurs and hybrid offspring are common.
Hybrid zones can provide insight into the process of speciation.
True or False: The ability to hybridize contradicts the reality of species distinction.
False
What is an Adaptive Radiation?
The evolutionary diversification of a species or single ancestral lineage into various forms each adaptively specialized to a specific environmental niche.
What conditions facilitate rapid Adaptive Radiation?
- Numerous unoccupied niches
- Minimal competition for resources
How does reproductive isolation occur in nature?
Through mechanisms that prevent interbreeding, including prezygotic and postzygotic isolating mechanisms.
What happens after one speciation event?
Species evolve into other species over periods ranging from a few dozen to hundreds of thousands of years.
