Chapter 21 Flashcards
(14 cards)
CC species concepts (4)
Introduction
Biological Species Concept
Limitations of the Biological Species Concept (BSC)
Other Species Concepts
Introduction
Species: Latin for “kind” or “appearance”
Speciation: processes where one species splits into two new species
Microevolution: changes over time in the alleles in a population
Macroevolution: a broad pattern where species are formed
Biological Species Concept
The biological species concept = species is a group of populations whose members have
Interbreed in nature and
Produce viable, fertile offspring
Reproductively isolated
Gene flow between populations keeps genotypes similar
Ernst Mayr
Limitations of the Biological Species Concept (BSC)
“Potential to interbreed in nature and produce viable, fertile offspring”
Sexual reproduction only - (interbreed)
Alive today
Is it possible to test all individuals?
How do we know if these dinosaurs are the same or different species?
Other Species Concepts
Morphological species concept
Uses physical characteristics
Works for extinct or asexual
But…must agree on characters
Ecological species concept
Species is defined by its niche (role in environment)
Works for extinct or asexual
But… must understand complex interactions
CC and SEQ the 5 prezygotic, and 3 postzygotic isolation mechanisms
5 prezygotic
Habitat isolation
Temporal (time) isolation
Behavioral Isolation
Mechanical isolation
Gametic Isolation
3 postzygotic
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
Habitat isolation
Habitat isolation: impedes mating
Two species encounter each other rarely, or not at all, because they occupy different habitats
Ex. two different butterfly species live on different habitats
Temporal (time) isolation
Temporal (time) isolation: impedes mating
Species that breed at different times of the day, different seasons, or different years cannot mix their gametes
Ex. spring field crickets and fall field crickets will breed different seasons
Behavioral Isolation
Behavioral Isolation: impedes mating
Courtship rituals and other behaviors unique to a species are effective barriers
Ex. male fireflies use specific light patterns to attract females
Mechanical isolation
Mechanical isolation: impedes mating and/or preventing completion of mating
Morphological differences can prevent successful mating
Ex. snail has left-handed snail and cannot morphologically successfully mate
Gametic Isolation
Gametic Isolation: hinders fertilization
Sperm of one species may not be able to fertilize eggs of another species
Reduced hybrid viability
Reduced hybrid viability:
Genes of the different parent species impair the hybrid’s development
Ex. Ensatina hybrid is tasty and obvious
Reduced hybrid fertility
Reduced hybrid fertility:
Even if hybrids are living, they may be sterile
Ex. Donkey + horse = mule (sterile hybrid – all female) ; cannot create grandchildren
Hybrid breakdown
