Download 24 Speciation

Speciation and
Macroevolution
Chapter 24, 25
Evolution
• Microevolution is changes within a
population
• Speciation when changes among
populations is significant
• Macroevolution is the origin of new
taxonomic groups
– New kingdoms, families, orders, etc.
– Takes place over millions of years
What is a species?
• Species, simply means a “kind” or
“appearance”in Latin.
– Still used this way in chemistry
• In Taxonomy, species is the most unique
grouping in the hierarchy.
Species
• Based on Herbals, full page lists of
characters.
• Binomial system: Homo sapiens,
– Linnaeus (1700's) based on a type specimen,
called the Holotype, with a complete description
in Latin.
Herbal
Holotypes
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
populations
• Reproductive barriers separates
groups as separate species.
Biological Species Concept
• Recognizes species as independent
evolutionary lineages
• 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)
•
•
•
•
Morphological
Paleontological
Ecological
Phylogenetic
Legal Species
• Laws protect endangered species in USA
• Make population a new species – now
protected ?
• Lump a protected species with another as
one
– loose protection?
– Gray Wolf
Gray Wolf
Coyote
Red Wolf
Do you protect the Red Wolf as an endangered
species?
Are they a separate species?
Hybridization
• Gene flow still exists between two
populations if hybrids can form and
reproduce
• Ring species – are groups of populations
that can reproduce with their neighbors, yet
the extreme can not.
Deer Mouse
California Salamanders: Ring Species
• Ensantina eschscholtzi
Speciation types
• Anagenesis
– Transformation of one
species into another over
time.
• Cladogenesis
– Branching evolution
Reproductive Barriers
• 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.
Reproductive
barriers
Allopatric Speciation
• Takes place in separate
areas.
• Populations become
separated by a geologic
barrier, blocking gene flow
Antelope squirrels of the Grand
canyon rim
Testing Speciation:
Adaptive
radiation
• Dispersal to island
followed by
• Adaptation to new
area-speciation
• Dispersal to next
island
• Eventually lead to
several species
coexisting
• Each adapted to
different niches on
islands
Adaptive radiations
• Species diversify from their ancestors
when important new novel traits form.
• These traits allow them to open a new
adaptive zone.
Hawaiian Honeycreepers
• Honeycreepers In absence of
other bird
species, they
radiated to fill
numerous niches
FOUNDER SPECIES
Sympatric speciation
• Takes place within habitat
of parent species
• Reproductive barrier
forms within a subset of
population
• Genetic or behavioral
Polyploidy
• Meiotic errors fail to produce haploid
gametes.
• Doubling of chromosome numbers restores
fertility, Polyploidy
• May be in one species – Autopolyploidy
• May be in a hybrid- Allopolyploidy
• Common in plants
Origin of Wheat
• Allopolyploidy
• Hybrid vigor
Sympatric Speciation
• Behavioral
– A sub set of animal choose mate by color, size,
etc.
• Temporal
– A sub set of animal mates or flowers emerge
earlier / later than the rest.
• Over time new species forms as gene flow is
stopped.
Rate of Evolution:
Constant Gradualism or Punctuated equilibrium?
Macroevolution
• Many speciation events over time give rise
to new lineages
• Evident in fossil record
• Novelties come about by modifications to
older structures.
• 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.
• Heterochrony
• Ground Salamander has longer toes and
less webbing because they grow longer
period of time
• On average, why are men taller than
women?
Allometric Growth
• 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
Paedomorphosis
• Adults retain some juvenile features of
ancestral species.
– Paedogenesis = Juvenile stage develops sexual
maturity precociously (early).
Homeotic Genes
• Control placement and spatial arrangement
of body parts
• Hox genes control development in animal
embryos
Species
selection
Overview
•
•
•
•
•
Fossil Record
Geologic Time scale
Mass extinctions
Continental Drift
Phylogenetic Trees
Fossil Record
• Fossil any preserved remnant or
impression of an organism that lived in
the past
• 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
• Pollen
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
Get discovered
Limitations of Fossils record
• Has to die in right place under the right
conditions. Most things don’t get into the fossil
record
• Biased: Highly favors hard parts, abundant, long
lived species organisms.
• Lots of missing organisms
• Hard to find, only certain areas highly researched
(NA. Europe)
Dating Fossils
• “Absolute” Radiometric dating: decay and
half-life of natural isotopes.
• Index dating – comparing index fossils in
strata
Radiometric “absolute” dating
Getting used to the geologic time
scale…
• 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
history.
– Enough time for 30,000 generations
Geologic Time
Scale Table 26.1
Know :
• 3 Eons
– Phanerozoic
– Proterozoic
– Archaean
• 3 Eras
– Their dates
– Major Animal and
Plant groups
• Periods:
– Permian
– 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
Eons:
• 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
Three Eras
• 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
structures, pathways
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
Crust
100 km (60 mi.)
200 km (120 mi.)
Crust
Low-velocity zone
Mantle
Lithosphere
Solid
10 to 65km
2,900km
100 km
(1,800 mi.)
3,700˚C
Outer core
(liquid)
Core
200 km
5,200 km (3,100 mi.), 4,300˚C
Inner
core
(solid)
Asthenosphere
(depth unknown)
Plate tectonics
• 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
continents.
• These land movements we call Plate
Tectonics, and cause earthquakes.
Layers of the Lithosphere
Oceanic crust
(lithosphere)
Abyssal Oceanic
floor
ridge
Abyssal
floor
Abyssal plain
Abyssal
hills
Trench
Folded mountain belt
Craton
Volcanoes
Continental
shelf
Continental
slope
Continental crust
(lithosphere)
Mantle (lithosphere)
Mantle (asthenosphere)
Mantle
(lithosphere)
Continental
rise
Abyssal plain
Plate
tectonicsDivergent
Areas
Lithosphere
Asthenosphere
Oceanic ridge at a divergent plate boundary
• Plates spread apart in Divergent
(constructive) making new crust
Fig. 10.6a
Slide
Convergent zones
• 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
Convergent plates
Trench
Volcanic island arc
Rising
magma
Subduction
zone
Lithosphere
Asthenosphere
Trench and volcanic island arc at a convergent
plate boundary
Fig. 10.6b, p. 215
Slide 8
• 10 MYA India (previously an
island) hits Asia
• 50 MYA. Australia becomes
completely isolated
• 65 MYA NA and Europe still
touched
• 135 MYA Pangea broke up
into Laurasia and
Gondwanaland
• 250 MYA Pangea all land
masses touched
• Fig 25.4
Mass extinctions
• 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.
Permian extinction
•
•
•
•
90% marine & 80% insect species gone
250 MYA
Took place in about 5 MY
Pangea forming, extreme volcanism- climate
change.
• Drop in sea level, loss of shoreline & intertidal,
more severe continental weather
• Isolated species come together and compete,
causing extinctions
• Paleozoic to Mesozoic boundary
Cretaceous extinctions
• 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
retreated.
• 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.
Alvarez-Impact theory
Chicxulub Crater- sonar image
Impact hypothesis
• 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
rain.
• Some lineages were dying out before
impact.
• Probably a final and sudden blow coming
at a time of change, with continental drift,
climate change.
Considerations for phylogeny
• Homologous structures- derived from a an
common ancestor
• Analogous structures - have same
function but evolved independently. Not
relates
– Convergence- similar looking features due to
adapting to the same habitat, not common
ancestry.
• Molecular clocks- give estimates but not
real dates.
– Assume mutation rates do not change
• Fossil evidence takes priority– Real dates and Real intermediate structures
Convergent Evolution
Ocotillo
North America
Allauidia
Madagascar
Phylogenetic trees
• Systematics makes groups based on
evolutionary relationships.
• 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
Phylogenetic Trees
Class Reptilia is paraphyletic
Cladogram Analysis
Molecular tools
• We can compare any
living organism to another
by DNA.
HIV Molecular clock
– between species so
distantly related the have
no obvious features in
common
• Objective and quantifiable
• DNA hybridizations,
sequences
• Protein sequences
• No real dates or
intermediate structures