Chapter 24, 25
• Microevolution is changes within a
• Speciation when changes among
populations is significant
• Macroevolution is the origin of new
– New kingdoms, families, orders, etc.
– Takes place over millions of years
What is a species?
• Species, simply means a “kind” or
– Still used this way in chemistry
• In Taxonomy, species is the most unique
grouping in the hierarchy.
• Based on Herbals, full page lists of
• Binomial system: Homo sapiens,
– Linnaeus (1700's) based on a type specimen,
called the Holotype, with a complete description
Biological Species Concept
• Not a definition proper
• Based the ability to sexually reproduce thus
sharing a common genepool and evolution.
– “Species are groups of interbreeding natural
populations that are reproductively isolated
from other such groups”.
Biological Species Concept
• Natural groups of populations
• Potential Ability to reproduce
shared by all members in groups of
• Reproductive barriers separates
groups as separate species.
Biological Species Concept
• Recognizes species as independent
• Morphology still what people use day to
day to identify species – keys to ID species
Problems with B. S. C. –
– Hybrids (many plant species)
– Nonsexual groups (Bacteria, fungi, some plants
and even animals)
– No good for extinct groups (fossils)
– Each remote population a separate species? No
potential to interbreed, but still same species
Other species concepts:
(Do not memorize them)
• Laws protect endangered species in USA
• Make population a new species – now
• Lump a protected species with another as
– loose protection?
– Gray Wolf
Do you protect the Red Wolf as an endangered
Are they a separate species?
• Gene flow still exists between two
populations if hybrids can form and
• Ring species – are groups of populations
that can reproduce with their neighbors, yet
the extreme can not.
California Salamanders: Ring Species
• Ensantina eschscholtzi
– Transformation of one
species into another over
– Branching evolution
• Lead to speciation by blocking gene flow
• Prezygotic barriers prevent successful
fertilization between species.
• Postzygotic barriers allow fertilization but
prevent successful development /
reproduction of hybrid.
• Takes place in separate
• Populations become
separated by a geologic
barrier, blocking gene flow
Antelope squirrels of the Grand
• Dispersal to island
• Adaptation to new
• Dispersal to next
• Eventually lead to
• Each adapted to
different niches on
• Species diversify from their ancestors
when important new novel traits form.
• These traits allow them to open a new
• Honeycreepers In absence of
radiated to fill
• Takes place within habitat
of parent species
• Reproductive barrier
forms within a subset of
• Genetic or behavioral
• Meiotic errors fail to produce haploid
• Doubling of chromosome numbers restores
• May be in one species – Autopolyploidy
• May be in a hybrid- Allopolyploidy
• Common in plants
Origin of Wheat
• Hybrid vigor
– A sub set of animal choose mate by color, size,
– A sub set of animal mates or flowers emerge
earlier / later than the rest.
• Over time new species forms as gene flow is
Rate of Evolution:
Constant Gradualism or Punctuated equilibrium?
• Many speciation events over time give rise
to new lineages
• Evident in fossil record
• Novelties come about by modifications to
• All intermediate forms must be suited to
their environments at the time
• Heterochrony- evolutionary change to rate
or timing of development.
– just a few key developmental genes modified.
• Ground Salamander has longer toes and
less webbing because they grow longer
period of time
• On average, why are men taller than
• Overall shape is
determined by relative
growth rates in the
different body parts
Changes in Petal Growth Rates
Allometric growth changes
Causes change in pollinator
• Adults retain some juvenile features of
– Paedogenesis = Juvenile stage develops sexual
maturity precociously (early).
• Control placement and spatial arrangement
of body parts
• Hox genes control development in animal
Geologic Time scale
• Fossil any preserved remnant or
impression of an organism that lived in
• Most form in sedimentary rock, from
organisms buried in deposits of sand
and silt. Compressed by other layers.
• Also includes impressions in mud
• Most organic matter replaced with
minerals by Petrification
• Some fossils may retain organic matter
• Encased in ice, amber, peat, or dehydrated
Fossil Formation – Fig. 22.3
Conditions that favor fossilization:
• Having Hard parts – shells, bones,cysts
• Get buried, trapped
– Marine species
– Marsh, flooding areas
Abundant species (with many individuals)
Long lived species (as a species)
Avoid eroding away
Limitations of Fossils record
• Has to die in right place under the right
conditions. Most things don’t get into the fossil
• Biased: Highly favors hard parts, abundant, long
lived species organisms.
• Lots of missing organisms
• Hard to find, only certain areas highly researched
• “Absolute” Radiometric dating: decay and
half-life of natural isotopes.
• Index dating – comparing index fossils in
Radiometric “absolute” dating
Getting used to the geologic time
• We use
– Millions of years (MYA) and
– Billions (BYA) of years ago.
• One Million Years: If we give 10,000 years for
all of recorded human history
– One million years equals 100 times all human
– Enough time for 30,000 generations
Scale Table 26.1
• 3 Eons
• 3 Eras
– Their dates
– Major Animal and
– Cretaceous (K)
– Tertiary (T)
The three Eras and
the new groups that begin to
dominate on land
• Cenozoic Era– 65.5 MYA
– Mammals, birds flowering plants
• Mesozoic Era – 251 MYA
– Reptiles, conifers
• Paleozoic Era – 542 MYA
– Amphibians, insects, moss, ferns
• Precambrian (2 Eons) – 4.6 BYA
– Origin of animal phyla
– Protists, bacteria
The three Eons and
the new groups that begin to
dominate on land
• Phanerozoic – Present to 542 MYA, 3 Eras
“Precambrian” is now 2 Eons:
• Proterozoic - 542- 2,500 MYA
– Origins of Eukaryotes
• Archaean – 2,500- 4,500 MYA
– bacteria, and oxygen atmosphere
• Eras do not have same amount of time
• Pace of evolution quickens with each major
branch or era .
• Recent organisms generally are more complex –
older ones simpler.
• Why ?
Pace of evolution
• Quicken over the eras
• Evolution builds on what is already there.
• Don’t have to recreate the first cell, and all it
machinery with each new species.
• More complexity forms out of simpler base
Many changes in geologic
history due to Plate tectonics
Earth’s Mantle Layers
• Inner Solid Mantle layer –
• Outer Mantle divided into two layers
– Asthenosphere – deep
– Lithosphere- “shallow” surface
• Approx. Top 40miles
Layers of the Earth
35 km (21 mi.) avg., 1,200˚C
100 km (60 mi.)
200 km (120 mi.)
10 to 65km
5,200 km (3,100 mi.), 4,300˚C
• The study of the movement of earth
structures in the crust.
• Internal forces from the core create heat
that keeps asthenosphere molten.
– Convection cells
– Mantle Plumes
Convection Cell in Mantle
Earth’s Layers - Crust
• Oceanic Crust
– only 3 miles thick
• Continental Crust
– up to 12-40 miles thick
• Oceans change shape much more than
• These land movements we call Plate
Tectonics, and cause earthquakes.
Layers of the Lithosphere
Folded mountain belt
Oceanic ridge at a divergent plate boundary
• Plates spread apart in Divergent
(constructive) making new crust
• Plates move together and collide.
• An Oceanic Plate sinks under Continental
in a Subduction zone.
– Causes Earthquakes, volcanoes
• When Continental plates collide neither
subducts, both deform, mountains
Volcanic island arc
Trench and volcanic island arc at a convergent
Fig. 10.6b, p. 215
• 10 MYA India (previously an
island) hits Asia
• 50 MYA. Australia becomes
• 65 MYA NA and Europe still
• 135 MYA Pangea broke up
into Laurasia and
• 250 MYA Pangea all land
• Fig 25.4
• Mark borders of Eras:
– 245 Permian (Paleo-Mesozoic)
– 65 Cretaceous (K/T boundary; Meso-Cenozoic)
• Caused by a major change that affects many
species at once.
90% marine & 80% insect species gone
Took place in about 5 MY
Pangea forming, extreme volcanism- climate
• Drop in sea level, loss of shoreline & intertidal,
more severe continental weather
• Isolated species come together and compete,
• Paleozoic to Mesozoic boundary
• 65 MYA
• Wiped out 50 % marine species, on land
many families of plants and the Dinosaurs.
• Mesozoic to Cenozoic boundary.
• Climate cooled and shallow seas
• Mammals and angiosperms around earlier,
but survived and radiated out to dominant
now empty niches
• Many diverse lineages from algae to
dinosaurs disappeared at once.
Chicxulub Crater- sonar image
• Anomalous Iridium layer marks boundary
layer – element common in meteorites
• Chicxulub Crater
• Explains large water scarring in NA.
• Global winter lasting years, collapsed food
chains. Ignite tremendous wildfires, acid
• Some lineages were dying out before
• Probably a final and sudden blow coming
at a time of change, with continental drift,
Considerations for phylogeny
• Homologous structures- derived from a an
• Analogous structures - have same
function but evolved independently. Not
– Convergence- similar looking features due to
adapting to the same habitat, not common
• Molecular clocks- give estimates but not
– Assume mutation rates do not change
• Fossil evidence takes priority– Real dates and Real intermediate structures
• Systematics makes groups based on
• Cladistics an analytical method to
determine branch points.
• Only Monophyletic trees are accepted.
– Include all species from a common ancestor.
• Polyphyletic trees
– grouping of taxa that have do not have
ancestors in common to the entire group.
• Paraphyletic-Leaves out some descendant
species from the common ancestor
Class Reptilia is paraphyletic
• We can compare any
living organism to another
HIV Molecular clock
– between species so
distantly related the have
no obvious features in
• Objective and quantifiable
• DNA hybridizations,
• Protein sequences
• No real dates or