Biology 11 intro – Speciation
Postzygotic Isolating Mechanism
A form of Prezygotic Isolation
1 species does not recognize a call, dance
or pheromone signal
Slow and
steady
change from
one species
to another
Habitat Isolation
Barriers are in place after fertilization
Prezygotic Isolating Mechanism
Temporal Isolation
Behavioral Isolation
Mechanical Isolation
Gamete Isolation
A form of Prezygotic Isolation
2 species are reproductive at different
times of the year
Geographic barriers divide a population.
This prevent gene flow between the
population. Overtime the 2 populations
evolve into different species.
A form of Postzygotic Isolation
Sperm of one species doesn’t reach the
egg of another.
Phyletic
Gradualism
Cannot identify
Reproductive
isolation in the
fossil record
Punctuated
Equilibrium
New species
evolved quickly
leaving only a few
individuals in the
transition phase
Zygotic Isolation
Barriers are in place before fertilization
Hybrid Sterility
A form of Postzygotic Isolation
Hybrid can reproduce but its offspring
cannot
F2 Fitness
Speciation
Allopatric Speciation
Sympatric Speciation
Phyletic Gradualism
Punctuated Equlibrium
Phyletic Gradualism versus Punctuated
Equilibrium when explaining the lack of
transition fossils
Natural Selection
4 thing needed for natural selection to
occur
Fitness
A new species is created within a
population without any physical barriers
A form of Prezygotic Isolation
2 species in same location but in
different habitats
Long periods of
no new species
followed by
short periods of
rapid speciation
One species evolves into two species
A form of Postzygotic Isolation
Fertilization between two different
species occurs but the zygote does not
survive
A form of Prezygotic Isolation
Two species are not capable of breeding
A form of Postzygotic Isolation
Hybrid survives but is not able to
produce any offspring
A measure of the number of fertile
individuals produced over an organisms
life time
Sexual Reproduction:
- mutations only
Asexual Reproduction:
- mutations only
- mixing of genes
Individuals with better survival traits
produce more offspring then others
Variation via sexual and asexual
reproduction
Bell Curve
Stabilizing Selection
Directional Selection
When the
average or
normal
phenotype is
favored
One extreme
is favored.
Bell curve
moves to the
right or the
left
Both
extremes are
favored.
Average
individuals
are selected
against
1) Individual Variation: members of a
population are different from each other
2) Inheritance: Traits are passed down to the
next generation
3) Overproduction: More offspring are
produced then the environment can sustain
4) Differential Reproductive Success:
Better adapted individuals produce more
offspring
Disruptive Selection
Requirements for creation of small
molecules
Purpose: Tried to create small molecules
using earth’s early atmosphere
Results: Fluid contained traces of amino
acids and organic acids
Miller and Urey’s Experiment
RNA molecules were the only
molecules needed to form the first
cells
Evidence: RNA acts as genetic blue print
and an enzyme
Macromolecules and how they formed
Proteins and Nucleic acids arrived at
the same time
Evidence: Clay attracts particles like
amino acids and nucleic acids. Once they
build up around the clay they form long
chains of proteins and RNA or DNA
Miller and Urey’s Apparatus
3 Hypothesis Explaining Macromolecules
1) RNA – first Hypothesis
Large chains of molecules
Formed when initial small molecules
(amino acids, nucleic acids) joined to
create large chains.
Eg. DNA, Proteins
1)Energy: early earth had high
temperature
3 Hypothesis Explaining Macromolecules
Heat = Energy
2) Protein – first Hypothesis
2)Elements needed for building
molecules
Microspheres
C
Methane Gas
N
Ammonia Gas
O
Water
H
Hydrogen Gas
1) Silent Mutation: change in DNA
3 Hypothesis Explaining Macromolecules (genotype) but not appearance
3) Graham Cairns-Smith’s Hypothesis
(phenotype)
2) Expressed Mutation: Change in
genotype and phenotype
Protocells versus True Cells
Transition Fossils
5 Agents of Evolutionary Change
2 types of mutations
Genetic Drift
Gene Flow
Nonrandom Mating
An organism travels to a new population
and carries its genes with them. These
genes are then moved into the
population via sexual reproduction
Individuals pair up based on their
phenotype.
Problems: Inbreeding: Lose genetic
diversity. Build up of harmful recessive
genes.
Protein molecules were the only
molecules needed to form the first
cells
Evidence: Amino acids form long chains
of protein on their own
Microspheres: Globules of protein are
collected in drying pools. When returned
to water the have properties of cells
Protocell: Lipid
True Cells: Lipid
protein
membrane bound
membrane.
structures
Capable of energy capable of protein
metabolism
synthesis
Show a link between 2 groups of
organisms
Eg. Archaeopteryx shows a link between
reptiles and birds.
1) Mutations
2) Genetic Drift
3) Gene Flow
4) Nonrandom Mating
5) Natural Selection
Change in how often a particular allele is
seen in a population
Eg. The allele for brown eyes
4 Pieces of evidence used to determine
the phylogenetic tree
Also used as evidence for evolution
Biochemical relationships
Homologous versus Vestigial and
Analogous structures
Binomial Name
Systematics
Seven Characteristics of Living Things
Different species use identical molecules
for cell functions
Eg. DNA = Genetic Blue print
Protein = Build cell structures
ATP = Energy
The name of the genus followed by the
species name.
Only genus name is capitalized
Eg. Canis lupus
1) they are organized
2) They acquire materials and energy
3) They reproduce
4) They respond to stimuli
5) They are homeostatic
6) They grow and develop
7) They adapt to their environment
Systematics: The act of identifying
species then classifying them according
to a set of rules.
Taxonomy:
1) Evolutionary relationships (fossil
record)
2) Biochemical relationships
3) Homologous Structures
4) Embryonic Relationships
Analogous Structures: Structures have
similar functions but different anatomy = no
similar ancestor
Vestigial Structures: Structures that are
found in related species but are reduced in one
(vestigial)
Homologous Structures: Anatomy and
function of a structure are similar in 2 species
because they have a similar ancestor