The Origin of Species
AP Biology
Speciation and Reproductive Isolation
 Species: members in a population who
have the potential to interbreed in nature
and produce viable, fertile offspring
Reproductive isolation: one group of
genes becomes isolated from one another
to begin a separate evolutionary history
 Speciation: anything that fragments a
population and isolates a small group of
individuals

 Allopatric
 Sympatric
AP Biology
 Allopatric Speciation: caused by
geographic isolation
AP Biology
 Sympatric Speciation: caused by anything
besides geographic isolation

habitat isolation: two organisms live in the same
area but rarely encounter one another

behavioral isolation: two species do not mate
because of differences in courtship behavior

temporal isolation: populations may mate or
flower at different seasons or different times of day

reproductive isolation: closely related species
unable to mate because of a variety of reasons
 prezygotic barriers
 postzygotic barriers
 reproductive isolation
AP Biology
Scientific evidence of biological
evolution uses information from
geological, geological, physical,
chemical and mathematical
applications
AP Biology
Scientific evidence for Evolution
1) Fossil Dating
 Age of rocks where
fossils are found
 rate of decay of C-14
 relationships within
phylogenic trees
 mathematical equations
that utilize chemical
properties to estimate
age
AP Biology
2) Morphological
Homologies
3) Vestigial structures
4) Genetic similarities
5) Mathematical
structures

phylogenic trees
Patterns of Evolution
 Divergent
 Convergent
 Parallel
 Coevolution
 Adaptive Radiation
 Gradualism
 Punctuated
AP Biology
Divergent Evolution
 Occurs when a population becomes
isolated from the rest of the species,
exposed to new selective pressures,
and evolves into a new species
allopatric speciation
 sympatric speciation

AP Biology
Convergent evolution
 Flight evolved in 3 separate animal groups
evolved similar “solution” to similar “problems”
 analogous structures

AP Biology
Convergent evolution
 Fish: aquatic vertebrates
 Dolphins: aquatic mammals
similar adaptations to
life in the sea
 not closely related

AP Biology
Those fins & tails
& sleek bodies are
analogous structures!
Parallel Evolution
 Convergent evolution in common niches


filling similar ecological roles in similar
environments, so similar adaptations were selected
but are not closely related
marsupial
mammals
placental
mammals
AP Biology
Parallel types across continents
Niche
Burrower
Placental Mammals
Australian Marsupials
Mole
Marsupial mole
Anteater
Numbat
Anteater
Nocturnal
insectivore
Mouse
Climber
Marsupial mouse
Spotted cuscus
Lemur
Glider
Stalking
predator
AP Biology
Chasing
predator
Sugar glider
Flying
squirrel
Ocelot
Tasmanian cat
Wolf
Tasmanian “wolf”
Coevolution
 Two or more species reciprocally
affect each other’s evolution

predator-prey
 disease & host
competitive species
 mutualism

 pollinators & flowers
AP Biology
Adaptive Radiation
 the emergence of
numerous species
from a common
ancestor introduced
into an environment,
filling a niche
AP Biology
Modern Theory of Evolution
1. Gradualism
2. Punctuated Equilibrium
3. The Origin of Life
4. Endosymbiosis
AP Biology
Modern Theory of Evolution
1. Gradualism

AP Biology
Organisms descend from a common
ancestor gradually over a long period of
time in a linear branching fashion
2. Punctuated Equilibrium
Stephen J. Gould and Nile Eldridge
stated that gradualism is not supported
by fossil record
 Rather a sudden appearance of species
is explained by the allopatric model

AP Biology
3. The Origin of Life is a Hypothesis
 Special Creation


Was life created by a
supernatural or divine force?
not testable
 Extraterrestrial Origin


Was the original source of
organic (carbon) materials
comets & meteorites striking
early Earth?
testable
 Spontaneous Abiotic Origin

AP Biology
Did life evolve spontaneously
from inorganic molecules?
testable
Millions of years ago
1000
1500
2000
2500
3000
3500
Paleozoic
PROTEROZOIC
PRECAMBRIAN
500
Cenozoic
Mesozoic
ARCHEAN
0
Colonization of land
by animals
Appearance of animals
and land plants
First multicellular
organisms
Animalia
Oldest definite fossils
of eukaryotes
Appearance of oxygen
in atmosphere
Oldest definite fossils
of prokaryotes
4000
Molten-hot surface of
earth becomes cooler
4500
Formation of earth
AP Biology
Bacteria Archae- Protista Plantae Fungi
bacteria
The evolutionary tree of
life can be documented
with evidence.
The Origin of Life on
Earth is another story…
What is Life?
 First we have to define LIFE…



organized as cells
respond to stimuli
regulate internal processes
 homeostasis

use energy to grow
 metabolism

develop
 change & mature
within lifetime

reproduce
 heredity
 DNA / RNA
 adaptation & evolution
AP Biology
Spontaneous Generation
 What does it mean for something to be
spontaneous?
 It used to be thought that living things
could arise from nonliving things.
 This idea was called spontaneous
generation.
AP Biology
Experiments disproving
spontaneous generation
 Pasteur—mid 1800s


Boiled broth in curved
neck flask to allow air
to reach broth but not
microorganisms
Broth only became
cloudy when neck was
broken off.
AP Biology
New Idea
 These experiments proved
spontaneous generation incorrect.
 The idea that living things come from
other living things is called biogenesis.
AP Biology
Conditions on early Earth
 Reducing atmosphere
water vapor (H2O), CO2, N2, NOx, H2, NH3,
CH4, H2S
 lots of available H & its electron
low O2 =
 no free oxygen

 Energy source

lightning, UV radiation,
volcanic
What’s missing
from that
atmosphere?
AP Biology
organic molecules
do not breakdown
as quickly
Electrodes discharge
sparks
(lightning simulation)
Origin of Organic Molecules
 Abiotic synthesis
1920
Oparin & Haldane
propose reducing
atmosphere
hypothesis
 1953
Miller & Urey
test hypothesis

Water vapor
CH4
NH3
Mixture of gases
("primitive
atmosphere")
H2
Condenser
Water
 formed organic
compounds while
bonding to clay
AP Biology
 amino acids
 adenine
Heated water
("ocean")
Condensed
liquid with
complex,
organic
molecules
Stanley Miller
Harold Urey
University of Chicago
produced
-amino acids
-hydrocarbons
-nitrogen bases
-other organics
It’s ALIVE!
AP Biology
How did the first cells possibly form?
 Sidney Fox produced protocells from
solutions of amino acids by heating them.
 These structures have certain life-like
properties: take up substances from the
surroundings, growth, surrounded by a
membrane.
 They have properties unlike living things: no
hereditary characteristics, can’t respond to
natural selection
AP Biology
Dawn of natural selection
Origin of Genetics
 RNA is likely first genetic material
multi-functional
 codes information

 self-replicating molecule
 makes inheritance possible
 natural selection & evolution

enzyme functions
 ribozymes
 replication
regulatory molecule
 transport molecule

AP Biology
 tRNA & mRNA
Key Events in Origin of Life
 Key events in
evolutionary
history of life on
Earth
Earth formed
4.6 bya, very
hostile
environment
 life originated
3.5–4.0 bya

AP Biology
Prokaryotes
 Prokaryotes dominated life
on Earth from 3.5–2.0 bya
3.5 billion year old
fossil of bacteria
AP Biology
modern bacteria
chains of one-celled
cyanobacteria
Oxygen atmosphere
 Oxygen begins to accumulate 2.7 bya

reducing  oxidizing atmosphere
 evidence in banded iron in rocks = rusting
 makes aerobic respiration possible

AP Biology
photosynthetic bacteria (blue-green algae)
~2 bya
First Eukaryotes
 Development of internal membranes


create internal micro-environments
advantage: specialization = increase efficiency
 natural selection!
infolding of the
plasma membrane
plasma
membrane
endoplasmic
reticulum (ER)
nuclear envelope
nucleus
DNA
cell wall
Prokaryotic
cell
AP Biology
Prokaryotic
ancestor of
eukaryotic
cells
plasma
membrane
Eukaryotic
cell
4. Endosymbiosis
 Evolution of eukaryotes



origin of mitochondria
engulfed aerobic bacteria, but
did not digest them
mutually beneficial relationship
 natural selection!
internal membrane
system
aerobic bacterium
mitochondrion
Endosymbiosis
Ancestral
AP
Biology
eukaryotic
cell
Eukaryotic cell
with mitochondrion
Endosymbiosis
 Evolution of eukaryotes



Eukaryotic
cell with
mitochondrion
origin of chloroplasts
engulfed photosynthetic bacteria,
but did not digest them
mutually beneficial relationship
 natural selection!
photosynthetic
bacterium
chloroplast
Endosymbiosis
Eukaryotic cell with
AP Biology
chloroplast & mitochondrion
mitochondrion
Theory of Endosymbiosis
 Evidence

structural
 mitochondria & chloroplasts
resemble bacterial structure

genetic
Lynn Margulis
 mitochondria & chloroplasts
have their own circular DNA, like bacteria

functional
 mitochondria & chloroplasts
AP Biology
move freely within the cell
 mitochondria & chloroplasts
reproduce independently
from the cell
Cambrian explosion
 Diversification of Animals

543 mya
AP Biology
within 10–20 million years most of the major
phyla of animals appear in fossil record
AP Biology
AP Biology
Early mammal evolution
 125 mya mammals
began to radiate
out & fill niches
AP Biology
Mass Extinctions
 Fossil record shows most species that
have ever lived are now extinct.
 Reasons to become extinct:
1. destroyed habitat
2. changes in environment that did not
favor species
AP Biology
Mass Extinctions
 certain times in history environmental

changes have caused the normal rate of
extinction to increase dramatically = mass
extinction
5 Big Mass Extinctions
AP Biology
6th Mass Extinction ?
 Typical “background” rate for extinctions



is considered to be 1 – 10 in 400 yrs.
There have been > 1,000 extinctions in
past 400 yrs
Not counting those species (probably
some in rain forests) that are becoming
extinct that we had never discovered
Losses to date have not reached those of
the BIG 5
AP Biology
Consequences of Mass Extinctions
 significant & long term effects
 extinct species is gone forever  course

of evolution is changed
takes at least 5-10 million yrs for diversity
to recover from a mass extinction
AP Biology
Classification of Life
AP Biology
Classifying Life
 Molecular data
challenges 5 Kingdoms
 Monera was too diverse
 2 distinct lineages of prokaryotes
 Protists are still too diverse
 not yet sorted out
AP Biology
3 Domain system
 Domains = “Super” Kingdoms
Bacteria
 Archaea

 extremophiles = live in extreme environments
 methanogens
 halogens
 thermophiles

Eukarya
 eukaryotes
 protists
 fungi
 plants
 animals
AP Biology
Evidence supporting relatedness in all 3 domains
 Genetic Information

DNA/RNA: transcription, translation and
replication
 Genetic Code in all living things
 Metabolic process conservation
 Structural evidence

AP Biology
membrane bound organelles,
cytoskeleton
Kingdom
Bacteria
Kingdom
AP BiologyFungi
Kingdom
Archaebacteria
Kingdom
Protista
Kingdom
Plantae
Kingdom
Animalia