What is speciation?
formation of new species
Define species
kind" or "appearance
The biological species concept is based on what?
The potential to interbreed rather than on physical similarity
The biological species concept defines a species as
group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring members of other populations
When and who proposed the biological species concept?
In 1943, biologist Ernst Mayr
What is anagenesis?
the accumulation of heritable changes, altering the characteristics of a species
What is Cladogenesis?
New species arises from a population that buds from a parent species
What is the basis for biological diversity?
Cladogenesis
What is microevolution?
changes in gene pool
What is macroevolution?
appearance of different phenotypes
What is prezygotic?
Prevents the zygote from being formed
What is postzygotic?
Prevents the zygote from being functional
What are prezygotic barriers?
Habitat, Temporal, Behavioral, Mechanical, and Gamete isolation
What is habitat isolation?
different habitats
What is temporal isolation?
Species that breed during different times of the day, season, or year cannot mix their gamete
What is behavioral isolation?
Actions and behaviors that attract mates
What is mechanical isolation?
Morphological differences can prevent successful mating
What is gamete isolation?
Sperm of one species may not be able to fertilize the eggs of another species
What are postzygotic barriers?
Reduced Hybrid viability, fertility, and breakdown
Reduced Hybrid Viability
The genes of different parent species may interact and impair the hybrid's development
Reduced Hybrid Fertility
Even if the hybrid survives, they may be sterile
Hybrid Breakdown
First generation hybrid are viable and fertile but their offspring of the next generation are feeble or sterile
What is included in the species definition?
Morphological species concept, Paleontology Species Concept, Ethological, and Phylogenic
What does the morphological species concept characterize a species by?
characterizes a species by its body, shape, size, and other structural features
What are the advantages for MSC?
can be applied to asexual and sexual organisms; useful even without information of the extent of gene flow
How do scientists distinguish most species?
By MSC
What is a disadvantage of MSC?
the definition relies on subjective criteria
What does the Paleontological species concept focus on?
Bones and fossils
Why are we forced to distinguish many species this way?
Because there is little or no information about their mating capability
What does the ecological species concept view a species in terms of what?
its ecological niche and its role in a biological community
What can the ecological species concept accomodate?
asexual as well as sexual species
How does the phylogenetic species concept define a species as?
a set of organisms with a unique genetic history
What are the two ways speciation can occur in?
Allopatric and Sympatric
What is allopatric speciation?
A population forms a new species while geographically isolated from its parent population
What is sympatric speciation?
A small population becomes a new species without geographic seperation
What kind of population is most likely to experience allopatric speciation?
small, isolated populations
How to confirm a case of allopatric speciation?
determine whether the allopatric populations have changed enough that they no longer have the potential to interbreed and produce fertile offspring
What is polyploidy?
the condition in which an organism has extra sets of chromosomes
What is an autopolyploid?
an individual that has more than two chromosome sets, all derived from a single species
What is a more common form of polyploidy that can occur?
When two different species interbreed and produce a hybrid that are often sterile
What is an allopolyploid?
fertile with each other but cannot interbreed with either parental species
Why are interspecific hybrids sterile?
Because the set of chromosomes from one species cannot pair during meiosis with the set of chromosomes from the other species
Adaptive radiation typically occurs when
organisms make their way to new, often distant areas or when environmental changes cause numerous extinctions, opening up ecological niches for the survivors
What is punctuated equilibrium?
equilibrium that is interrupted by brief period of more rapid change
What is gradualism model?
species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations
What is punctuated equilibrium model?
A new species changes most as it buds from a parent species and then changes little for the rest of its existence
What is exaptations?
Structures that evolve in one context but become co-opted for another function
What is heterochrony?
an evolutionary change in the rate or timing of developmental events
What is allometric growth?
proportioning that helps give a body its specific form
What is paedomorphosis?
maintain juvenile characteristics that are usually left behind