Term
| A physical barrier that reduces gene flow sufficiently for genetic differences to evolve |
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Definition
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Term
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Definition
speciation by geographic isolation
Isolation might occur because of great distance or a physical barrier, such as a desert or river, as shown below
The physical barrier reduces gene flow sufficiently for genetic differences to evolve (Natural selection or genetic drift)
It prevents gene exchange if the populations come into contact later on |
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Definition
A union between two gametes that differ in size or form
Often of a large motile female gamete (MEGAGAMETE) by a small motile male gamete(MICROGAMETE) |
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| Biological Species Concept |
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Definition
Hybrid Creation
describes an evolutionary entity
efines a species as members of populations that actually or potentially interbreed in nature, not according to similarity of appearance. |
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Definition
The failure of individuals of species with recent common ancestry (i.e. related species or semispecies) to produce hybrid offspring because differences in their behaviour prevent successful mating taking place
o Potential mates meet but do not mate
o Behavioral or sexual barriers
o Very important among sympatric species that may frequently encounter one another but don’t mate
o ANIMALS: differences in courtship behaviors or sex pheromones
o PLANTS: using specific pollinators that are specific to only one species of plant |
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Definition
Adaptive Significance of Sex
The production or fusion of morphologically identical gametes
Occurs in many protists and algae
Gametes are small and motile
Two types- + and – (only fuse with opposite type) |
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Definition
Large immobile female gamete
Anisogamy |
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Definition
Small motile male gammete
anisogamy |
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Term
| Migration homogenizing Evolutionary Force |
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Definition
o Migration moves alleles between populations.
o It can cause allele frequencies to change from one generation to the next.
o From small populations receiving immigrants from larger populations Migration can be a potent mechanism of evolution.
o Migration tends to prevent local adaptation.
o Migration tends to prevent evolutionary divergence between populations. |
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Definition
is the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner
o In a population without recombination there is a tendency for slightly deleterious mutations to accumulate |
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Term
| Niles Eldredge and Stephen Jay Gould Proposed: |
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Definition
| The theory of punctuated Equilibrium |
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Definition
Inbreeding:: leads to inbreeding depression
Heterozygous parents will produce ½ heterozygous offspring and ½ homozygous offspring. |
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Definition
| no specific extrinsic barrier to gene flow. The population is continuous, but nonetheless, the population does not mate randomly. Individuals are more likely to mate with their geographic neighbors than with individuals in a different part of the population’s range |
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Term
| Parapatric Speciation if Gene flow is low |
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Definition
| relatively weak selection will be enough to establish differences at the genetic level to result in reproductive isolation |
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Term
| Parapatric Speciation when geneflow is high: |
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Definition
| the difference required for reproductive isolation will occur only under strong selection |
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Definition
The development of young from unfertilized eggs.
In honey bees the unfertilized eggs produce drones |
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| Potential mates meet but do not mate |
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Definition
| Ethological Isolation: Animal behavior |
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Definition
Eldredge and Gould observed that instead of a slow, continuous movement, evolution tends to be characterized by long periods of virtual standstill ("equilibrium"), "punctuated" by episodes of very fast development of new forms
criitique of Darwin's theory of Evolution
Suggests that broadly distributed, well established species maybe incapable of evolving substantially because of constraints
Peaks shifts in small populations can rapidly give rise to morphologically divergent new species
When these species spread from their point of origin and become abundant enough they suddenly appear in the fossil record. |
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Term
RHAGOLOTIS POMONELLA
(THE APPLE MAGGOT FLY) |
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Definition
Sympatric Speciation Example::
200 years ago, the ancestors of apple maggot flies laid their eggs only on hawthorns—but today, these flies lay eggs on hawthorns (which are native to America) and domestic apples (which were introduced to America by immigrants and bred). Females generally choose to lay their eggs on the type of fruit they grew up in, and males tend to look for mates on the type of fruit they grew up in. So hawthorn flies generally end up mating with other hawthorn flies and apple flies generally end up mating with other apple flies. This means that gene flow between parts of the population that mate on different types of fruit is reduced. This host shift from hawthorns to apples may be the first step toward sympatric speciation—in fewer than 200 years, some genetic differences between these two groups of flies have evolved.
There are several loci that are different between flies that continue to parasitize hawthorns (closely related to apples) and those that affect apples
Gene exchange is further reduced by an average of three weeks difference between the flies mating on apples and those that mate on hawthorns
Flies are beginning stages of sympatric speciation
Because apples ripen and suitable for larval development earlier than hawthorns
Selection for divergent timing of emergence and reproduction may be responsible for the genetic differences that have been observed |
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Term
| Sex & The role of Parasites |
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Definition
Except under the effects of inbreeding, the sexual population was more resistant then the clones
EXPLANATION: sexual population = more diversity
(Haldane, 1949) if parasites evolve to attack the more common types in a host population, then the rarer types will have an advantage
May not only favor the rarer types over the common types in asexual populations but may favor SEXUAL over ASEXUAL |
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Term
| Sexually Reproducing Polyploid Animals |
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Definition
Some frogs && Fish
parthenogenic species such as weevils, grasshopper, salamanders and lizards |
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Definition
| is the evolutionary process by which new biological species arise |
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Definition
does not require large-scale geographic distance to reduce gene flow between parts of a population
Merely exploiting a new niche may automatically reduce gene flow with individuals exploiting the other niche |
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Term
| differences in courtship behaviors or sex pheromones |
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Definition
| Ethological Isolation: Animal Behavior |
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Term
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Definition
A reduction in fitness resulting from mating between close relatives that occurs by chance in small populations or by assortative mating in large populations.
usually results from the exposure of deleterious recessive mutations to selection
increases the number of homozygous recessive genotypes and exposes them to selection
refers to the fitness consequences of deleterious recessive alleles in homozygotes when compared to the rest of the population. |
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Term
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Definition
definition: Containing more than two homologous sets of chromosomes.
reproductively isolated hybrid sterility from their progenitors= distinct species
2 distinctions
1. Only instantaneous mode of speciation by a single genetic event
2. The only mode of sympatric speciation that is widely accepted |
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Definition
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Term
| sympatric species that may frequently encounter one another but don’t mate |
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Definition
| Ethological Isolation: Animal Behavior |
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Term
| using specific pollinators that are specific to only one species of plant |
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Definition
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