Evolution Flashcards
Bootcamp + booster
Evolution
is the changes in populations, species or groups; changes in allele (traits) frequencies in populations over time.
Microevolution
the changes in allele frequencies that occur over time within a population due to mutation, selection, gene flow, gene drift, and nonrandom mating.
Macroevolution
the patterns of changes in groups of related species over broad periods of geologic time. Patterns determine phylogeny
(evolutionary relationships among species and groups of species). These patterns can be used to establish a phylogenetic tree
Cuvier proposed
catastrophism
catastrophism
Catastrophes lead to mass extinctions of species in those areas. The different populations in different areas were shaped
by what catastrophes had occurred, and what random organisms then survived and
populated that area.
Lamarck proposed:
Use and disuse, Inheritance of acquired characteristics
Use and disuse
used body parts will
develop and unused ones are weakened,
leading to evolution.
Inheritance of acquired traits
traits acquired through use and disuse are passed onto offspring (eg. giraffe stretching neck will cause its neck to
develop, and produce long necked offspring). This is incorrect - acquired characteristics are generally not heritable.
Darwin theory
Theory of Natural Selection.
Natural Selection
survival of the fittest without any luck. Allele frequencies increase or decrease in order to adapt to the environment.
Survival of the fittest
occurs as individuals with greatest fitness (ability to survive and produce viable
and fertile offspring) have greatest success, and pass on more DNA to future generations
compared to less fit parents.
Descent with modification
coined by Darwin, this occurs via natural selection. Over time and generations, traits
providing reproductive advantage become more common within the population.
Paleontology
fossils reveal prehistoric
existence of extinct species, and are often found in sediment layers. Deepest fossils represent the oldest specimens. Large, rapid changes produce new species.
Fossil types
actual remains, petrification,
imprints, molds, and casts
Biogeography
The geography that describes
the distribution of species. Unrelated species in different regions of the world look alike when found in a similar environment. The supercontinent Pangea slowly broke apart to 7 continents due to continental drift.
Embryology
similar stages of development
among related species establishes evolutionary
relationships. Gill slits and tails are found in fish, chickens, pigs, and human embryos.
Ontogeny
The development of an organism.
Phylogeny
The evolutionary development and diversification of a species.
Comparative anatomy
this describes two kinds of structures that contribute to the
identification of an evolutionary relationship.
Homologous structures
body parts that resemble one another between different species that descended from a
common ancestor. E.g., bat forelimbs vs. bird forelimbs
Analogous structures
body parts that resemble one another between different species that evolved independently. They have similar structures as adaptations to similar environments. These structures are also called homoplasies. E.g., bat wings vs. bee wings
Molecular biology
this field examines nucleotide and amino acid sequences of DNA and proteins from different species. More than
98% of nucleotide sequences in humans and chimpanzees are identical. Amino acids in the
protein cytochrome c are often compared
Comparative biochemistry
organisms with a common ancestor mean they have common biochemical pathways.
what are the key points of natural selection
- population possess an enormous reproductive potential
- Population size remains stable
- Resources are limited
- Individuals compete for survival
- There is variation among individuals in a population
- Much of the variation is heritable
- Only the most fit individuals survive
- Evolution occurs as favorable traits accumulate in the population
Stabilizing selection
the bell curve favors an
intermediate, like how the average height in humans is in the middle.
Directional selection
the favoring of traits that is at one extreme of the range. Traits at opposite extremes are selected against.
Industrial selection
the selection of dark-colored, melanic, varieties in various species of moths, like the peppered moth, as a result of
industrial pollution. This is a specific type of directional selection.
Disruptive selection
this selection occurs when the environment favors extreme or
unusual traits while selecting against common traits. For example, a certain environment may favor short and tall heights while the average height is selected against.
Sexual selection
the differential mating of males or females in a population
Intersexual selection
females choose superior males, which increases the fitness of the offspring. Because females
invest more energy into their offspring, they want to maximize the quality of their offspring by picking fit males.
intrasexual selection
when males compete and fight with other males for better mating opportunities. Males
increase fitness of offspring by
maximizing quantity. Intrasexual selection favors traits like musculature,
horns, large stature, etc.
Sexual dimorphism
the differences in appearance of males and females, which is a form of disruptive selection. This occurs because female choice leads to traits and behaviors in males that are
favorable to females. Male traits like colorful plumage or elaborate mating behavior will be selected for by females.
Artificial selection
this is a form of directional
selection carried out by humans when they breed favorable traits, and is not natural
selection
Mutation
new alleles could be introduced to the population with genetic mutations.
Sexual reproduction
genetic recombination such as crossing over, independent assortment, and random joining of gametes can occur during sexual reproduction
Diploidy
Diploid organisms have two copies of each chromosome. In heterozygous conditions, the recessive allele is stored for
later generations, and thus more variations are maintained in the gene pool
Outbreeding
mating with unrelated partners
results in mixing of different alleles and creating new allele combinations.
Heterozygote advantage
Two parents produce an
offspring that is more fit than either parent.
Hybrid vigor (heterosis)
the superior quality of offspring resulting from crosses between two different inbred strains, species, or varieties of organisms. Hybrid superior quality results from reducing deleterious recessive homozygous conditions and
increasing heterozygous advantage
Frequency-dependent selection
(minority advantage)
rare phenotypes offer higher fitness. Cycle between high
and low frequency. (eg. advantageous against hunters’ search images).
The Hardy-Weinberg formula
calculates genetic frequency during genetic equilibrium (no
change in gene frequencies). If both equations hold true, the population is under Hardy-Weinberg equilibrium.
Hardy-Weinberg Equation: all individuals sum to 100%
p² + 2pq + q² = 1 (all individuals sum to 100%)
Hardy-Weinberg Equation: all alleles sum to 100%
p + q = 1 (all alleles sum to 100%)
Requirements to be in Hardy-Weinberg Equilibrium:
- No mutations - no new alleles can be introduced to the population
- No natural selection - the environment is not impacting allele frequencies, and so traits are neutral
- No gene flow - also happens as a result of no migration. An isolated population will have no
gene flow - Large populations - this decreases the effects of genetic drift
- Random mating - this decreases the chance of any allele from changing in frequency
Genetic Drift:
allele frequencies change by
chance. Larger effects on small populations.
Bottleneck effect:
smaller gene pool, some alleles may be lost (eg. disaster killing majority of population).
Founder effect:
some individuals migrate
away from the population.
Non-random Mating:
sexual selection, outbreeding, inbreeding.
Mutations:
can be dormant until environmental change allows it to flourish.
Gene Flow:
migration (non-random) moving
alleles between populations, leading to variation through mixing.
Neutral Variations
may become beneficial if the environment changes.
Polyploidy
plants have multiple copies of
alleles introducing more variety and preserving different alleles. Can also mask effects of a harmful recessive allele.
Prezygotic Isolation
mechanisms are barriers that prevent fertilization and zygote
formation from occurring between species.
Habitat Isolation
occupying different habitats
Temporal Isolation
reproducing at different times/seasons.
Behavioral Isolation
different courtship rituals
Mechanical Isolation
male and female genitalia are not compatible.
Gamete Isolation (Incompatibility)
gametes do not recognize or are unable to fertilize each other.
Postzygotic Isolation
refers to barriers to organism success after zygote has formed.
Hybrid Mortality (inviability)
hybrid zygote not-viable and does not survive past embryonic stage (often due to
different chromosome numbers).
Hybrid Sterility
hybrid zygote sterile (infertile).
Hybrid F2 Breakdown
Hybrid F2 generation have reduced fitness compared to their parental generation.
Speciation
is how species form, starting with reproductive isolation, which leads to interruption of gene flow between populations
that gradually develop into two species.
Allopatric Speciation:
occurs due to a geographical barrier.
Adaptive Radiation:
occurs when many species arise from one ancestor as they adapt differently to their environments. During adaptive radiation, species can specialize to fill different niches within
the same environment.
Sympatric Speciation:
occurs without a geographical barrier.
Balanced Polymorphism:
different phenotypes are isolated within the same
area.
Hybridization
some hybrids are more fit
than purebreds.
Phyletic gradualism:
evolution happened gradually via accumulation of small intermediary changes. Not likely to be true (not supported by fossil evidence).
Punctuated equilibrium:
short spurts of evolutionary changes during periods of stasis
(supported by fossil evidence).
Divergent Evolution:
species diverge from
common ancestor.
Convergent Evolution (Homoplasy):
unrelated species adapt to similar environments becoming more alike (analogous structures).
Parallel Evolution:
species diverge from a common ancestor but undergo similar changes.
Coevolution:
two species impart selective
pressure on each other. Classic examples are hummingbirds and flowers.
Camouflage
match appearance to environment to avoid detection. Strictly visual method of concealment.
Crypsis:
Similar to camouflage, except
includes olfactory (smell) or auditory methods of concealment (ex. scent
masking, silencing).
Aposematic Coloration
(warning coloration): vibrant coloration in poisonous animals to warn predators.
Mimicry:
evolving to resemble another
species.
Batesian mimicry
a non-harmful animal resembles a harmful one.
Mullerian mimicry,
two poisonous animals resemble each other to
warn their predator.
Phylogenetic tree
is a branched diagram that
shows inferred evolutionary relationships between different taxa.
clade
is a cluster with an ancestor and all its descendants.
monophyletic
(an ancestor and all its descendants)
paraphyletic
(ancestor and some but not all of its descendants).
cladogram
is a type of phylogenetic tree that shows such inferred evolutionary relationships
among various biological species.
internal node
is a branch point on a cladogram, and represents the splitting (divergence) of a single group into two descendant groups.
Cladogenesis
is a type of phylogenetic tree that shows such inferred evolutionary relationships
among various biological species.
internal node
is a branch point on a cladogram, and represents the splitting (divergence) of a single group into two descendant groups.
Cladogenesis
refers to the splitting apart of
evolutionary lineages (formation of new clades).
Anagenesis describes the gradual evolution of an interbreeding population without splitting.
Parsimony
means the simpler the evolutionary explanation, the better.
