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Balancing Selection
Balance of different alleles within a population.
TERM 2
Heterozygote Superiority
DEFINITION 2
Heterozygoous individuals have greater reproductive success
than homozygous individuals.
TERM 3
Frequency Dependant Selection
DEFINITION 3
Survivorship decreases as that phenotype becomes more
common.
TERM 4
Neutral Variation
DEFINITION 4
Polymorphism that is not affected by natural selection
because it offers neither an advantage nor a disadvantage.
TERM 5
Sexual Dimorphism
DEFINITION 5
The systematic difference in form between individuals of
different sex in the same species.
Outbreeding
The practice of introducing unrelated genetic material into a
breeding line.
TERM 7
Morphological Species Concept
DEFINITION 7
Classifies organisms based on observable and measurable
phenotypic traits. It can be applied to asexual organisms,
fossils, and in cases when we dont know about possible
interbreeding. There is some subjectivity in deciding which
traits to use.
TERM 8
Ecological Species Concept
DEFINITION 8
Defines a species by its ecological role or niche. Classifies by
unique adaptations to its particular role.
TERM 9
Phylogenetic Species Concept
DEFINITION 9
Defines a species as a set of organisms representing a
specific evolutionary lineage. Morphological or DNA
similarities or differences can be used to define a species.
Defining the amount of difference required to distinguish
separate species is a problem.
TERM 10
Biological Species Concept
DEFINITION 10
Groups of actually or potentially interbreeding populations,
which are reproductively isolated from other groups.
Allopatric Speciation
Populations are separated by a geographic barrier and evolve
separately.
TERM 17
Sympatric Speciation
DEFINITION 17
Reproductive isolation without geographic isolation.
TERM 18
Polyploid
DEFINITION 18
Occurs in cells and organisms when there are more than two
paired (homologous) sets of chromosomes.
TERM 19
Hybrid Zone
DEFINITION 19
Exists where the ranges of two interbreeding species meet.
TERM 20
Fusion
DEFINITION 20
Weak reproductive barriers between the two species, with
considerable gene flow, reverses speciation and two species
become one again.
Reinforcement
If hybrids are less fit than parent species, natural selection
strengthens reproductive barriers.
TERM 22
Stability
DEFINITION 22
Many hybrid zones are stable, continuing to produce hybrids;
this allows some gene flow between populations, but each
species maintains its own integrity.
TERM 23
Nonbranching Evolution
DEFINITION 23
Population changes and becomes new species.
TERM 24
Branching evolution
DEFINITION 24
Splits lineage into 2+ species.
TERM 25
Temporal Isolation
DEFINITION 25
Occurs when species breed at different times- during diff
seasons, times of days, or years.
Reduced Hybrid Fertility
Hybrid offspring of two different species reach maturity and
are vigorous but sterile, and therefore unable to bring about
gene flow between the parent species.
TERM 32
Hybrid Breakdown
DEFINITION 32
First generation of hybrid offspring are viable and fertile, but
when these hybrids mate with one another or with either
parent species the offspring are feeble or sterile.
TERM 33
Gradualist Model
DEFINITION 33
Species evolve gradually and continuously in response to
selective pressures, slowly overtime have gradual changes
and stages can be seen through the fossil record.
TERM 34
Punctuated Equilibrium Model
DEFINITION 34
Long periods of stasis punctuated by bursts of "rapid"
change. Many fossil species appear suddenly in a layer of
rock, variation of original specie.
TERM 35
Mass Extinction
DEFINITION 35
High widespread extinction.
Radiometric Dating
Measures the decay of radioactive isotopes.
TERM 37
Continental Drift
DEFINITION 37
The slow, continuous movement of Earth's crustal plates on
the hot mantle.
TERM 38
Pangea
DEFINITION 38
Super continent formed 250 million years ago.
TERM 39
Phylogeny
DEFINITION 39
The evolutionary history of a species or a group of species.
TERM 40
Analogous Structures
DEFINITION 40
Organisms have similar structures but are unrelated.
Parsimony
The simplest hypothesis is the most likely phylogenetic tree.
TERM 47
Paedomorphosis
DEFINITION 47
Retention of juvenile body features in an adults.
TERM 48
Identity Genes
DEFINITION 48
Master control genes that direct development.
TERM 49
Horizontal Gene Transfer
DEFINITION 49
Genes that are transferred from one to another.
TERM 50
Genome
DEFINITION 50
A complete set of genes.
Molecular
Clock
Can be used to estimate dates of evolutionary episodes.
