Unit 2: Species and Speciation Flashcards
What is Species?
group of populations that interbreed and produce fertile offspring
What is Speciation?
a splitting event that creates 2 or more distinct species from a single ancestral species
What is Species Concept?
a set of criteria used to define and differentiate species
What is Morphological Species Concept?
species defined based on differences in size, shape, or other morphological features
What are the Pros & Cons of morphological species concept?
Pros:
- typically easy to measure traits
- can be applied to asexual and extinct species (fossils)
Cons:
- which traits, and how different do they need to be?
- species with different morphs (order of colors of birds)
- cryptic species ( 2 different species which look alike)
What is Gene Flow?
transfer of alleles from one population to another; makes populations similar
What is Reproductive Isolation?
behaviors or processes that prevent gene flow between populations; creates opportunity for divergence
What is Biological Species Concept?
species defined based on reproductive isolation:
- species do not interbreed in nature, or if they do, the offspring is not viable/stable
What are the Pros & Cons of biological species concept?
Pros:
- based on mechanism (reproductive isolation) low to lead to evolutionary divergence
Cons:
- can not be applied to asexual and extinct species
- what if populations are not sympatric?
What is Phylogenetic Species Concept?
species defined based on analysis of a phylogeny
What is Phylogeny (Phylogeny Tree)?
(evolutionary tree) representation of the evolutionary relationship among organisms
What is criteria of the phylogeny tree?
species are the smallest possible sets of monophyletic groups on a phylogeny tree
What is Monophyletic Group/Clade?
a group that consists of one ancestor and all its descendants
Phylogenies are nest hierarchy of clades. True of False?
True
What are the steps of prating Phylogenies?
- gather data from multiple population and samples
- use data to construct phylogeny
- analyze for monophyletic groups
What are the Pros & Cons of phylogenic species concept?
Pros:
- can be applied to asexual and extinct species
- can be used to analyze allopatric populations
Cons:
- production of phylogenies limited by samples
- different data sets may produce different phylogenies
What is Allopatry?
(occurring in different geographically areas) is an effective way to hinder gene flow between populations
Without gene flow, there is opportunity for populations to _____ and become reproductively isolated.
diverge
What is Allopatric Speciation?
speciation that occurs via geographically separation; most common mode of speciation
What are 2 routes to allopatry?
- dispersal to a new habitat
- vicariance
With dispersal, the likelihood of speciation is ______ correlated with connectively between patches
negatively, high connectivity = low chance of speciation
What is Vicariance?
the physical splitting of a population into smaller, isolated populations by a physical barrier
With vicariance, the likelihood of speciation is _____ correlated with the strength of the barrier.
positively
What is Reproductive Isolation?
situation that occurs when a species is reproductively independent from other species
What causes reproductive isolation?
- behavior
- location
- reproductive barriers
Isolating mechanisms can be _______ (before zygote formation) or ________ (after zygote formation)
prezygotic, postzygotic
What are the types of mechanism that prevent the formation of a zygote?
- temporal
- habitat
- behavioral
- mechanical
- gametic
What is Temporal Isolation?
differences in breeding schedules that can act as a form of pre zygotic barrier leading to reproductive isolation
What is Habitat Isolation?
reproductive isolation resulting when species’ populations move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the same species’ other populations; may never come into contact during mating periods = no hybridization
What is Behavioral Isolation?
type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place (e.g. sound frequencies in mating calls are unattractive)
Does behavioral isolation extend to plants?
Yes, pollinators may favor different floral shapes or food (nectar)
What is Mechanical Isolation?
differences in size and shape of reproductive organs, making mating impossible (e.g. genital lock & key)
What is Gametic Isolation?
prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs & sperm) prevent fertilization from happening
What are types of mechanisms that prevent zygotes from passing on alleles?
- Hybrid Inviability
- Hybrid Biological Sterility
- Hybrid Ecological Sterility
What is Hybrid Inviability?
hybrids do not survive to sexual maturity, instead they die during development or soon after birth
What is Hybrid Biological Sterility?
hybrids survive to maturity but do not produce gametes or are not fertile
What is Hybrid Ecological Sterility?
hybrids survive to maturity are are fertile, but have an intermediate phenotype that keeps them from reproducing (e.g. don’t attract mates or are not adapted to environment)
How do these reproductive isolation mechanisms evolve?
allopatry (e.g. natural selection, genetic drift, and mutation)
What are the 3 types of changes in hybrid zones?
- reinforcement
- fusion
- stability
What is Reinforcement?
continued speciation divergence between 2 species due to low fitness of hybrids between them
What is Fusion?
reproductive barriers weaken until the 2 species become 1
What is Stability?
fit hybrids continue to be produced
What is a Hybrid Zone?
area where 2 closely related species continue to interact and reproduce, forming hybrids; relatively stable over long periods of time
In a Hybrid Zone, exchange of alleles is limited and parental species remain distinct. True or False?
True
Since producing hybrids decreased fitness, natural selection results in _____
reinforcement
