Origins of Biological Diversity
Chapter 15
Page 323
Species Concept
• Biological Species Concept – A species is a
population (group) whose members have the
ability to breed with one another in nature and
produce fertile offspring.
• Ex: Humans and gene flow
• **MEMBERS OF ONE SPECIES CANNOT
SUCCESSFULLY INTERBREED WITH MEMBERS OF
OTHER SPECIES**
• Ex: Horses and Cows
• Not included: Asexual reproduction (frogs, fish,
insects) and fossils.
Micro and Macro Evolution
• Microevolution – A change in allele (trait)
frequencies within a population.
– Changes within one family.
• Macroevolution – Changes that are much
more dramatic and include:
– Origin of a species
– Extinction of a species
– Evolution of major features (wing on a bird)
Speciation – Origin of new species – This leads to
Biological Diversity, as new kinds of life is started.
Microevolution Example
Macroevolution Example
Reproductive Barriers
• INABILITY TO BREED MARKS SPECIES AS SEPARATE –
HOW?
• Reproductive Isolation – A barrier that keep species
from breeding
– Timing – Different breeding seasons
– Behavior – Different courtship or mating rituals Ex: bird
songs and colors.
– Habitat – Different habitats in the same location Ex:
Sawgrass birds vs. open waterway birds in the Everglades.
– Incompatibility of physical structures
– Sperm plug Ex: Hemipenes and certain snakes.
– Failure to develop
– Infertility
– Natural Abortion – Without help (From stress, attack, or
low food – may abort to save the genes in bad times).
Geographic Isolation
• Separation of populations due to geographic
change or dispersal to isolated places Ex:
Earthquake or Hurricane (Birds) – Even in
Everglades or Keys – Key Deer
– Depends on species ability to physically move
– New “splinter” population may now have their
own evolution (genetic drift and natural
selection).
– Many may die through failure to survive and
thrive
– See Figure 15-6 and Figure 15-7 in book
Geographic Isolation Example
Adaptive Radiation
• Evolution from a common ancestor that
results in diversification of species
• See Figure 15-7 in your book (page 328)
• 1) Colonization of a new island (empty
environment)
• 2) Species evolve and move to other islands in
the chain and create entirely new species.
• Ex: Hawaiian birds
Adaptive Radiation Example
Tempo of Speciation
• Punctuated Equilibrium –
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–
–
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Species appears suddenly
Persists for thousands of years and has no changes
Suddenly disappears.
*There are long periods of little change (equilibrium)
broken by shorter periods of change and speciation,
which can be very rapid.
– **Successful species last approximately 5 million years
(Man is not successful yet)
– Can be a short or long interval.
– Natural Selection and adaptation happen during
Punctuated Equilibrium when a species is “Young”.
Example of Punctuated Equilibrium
Refinement of Existing Adaptations
• Physical structures are adapted or “changed”
over time from simpler structures
• Ex: The eye of an animal can range from simple to
complex – Eyes are based on food needs, light
needs, light access. Deep trench animals in the
ocean use fluorescence.
Adaptation of Existing Structures
• When existing materials or structures start with a
certain function, then over time fulfill other
functions.
– Chitin – forms the exoskeleton of Arthropods (insects,
spiders, and lobsters)
– In the ocean, chitin helped protect animals from
predators
– On land, chitin helps to prevent dehydration.
– Penguin flippers – Penguins are birds whose flippers
are modified wings – they “fly” through the water.
They are isolated from land predators, but do have
water predators.
Evolution and Development
• Embryology – The study of processes of
multicellular organisms as they devleop from
fertilized eggs to adults.
– Genes or the Adaptation of body parts based on
the geography of their home area.
Fossil Records
• Are created by dead organisms
• Some fossils actually retain organic material
(plants keep chlorophyll).
• Fossils are studied for clues on:
– Time period of life for organism
– Diet
– Breeding
– Digestion
**Fossils in ice are slower to decompose than in
rock layers.**
Fossil Record Example
Geologic Time Scale (VIP!!)
• Use acronyms to remember all of this.
• 3 large divisions:
– Eras
– Periods
– Epochs
•E
•P
•E
Eras
• 4 Different Eras:
– Precambrian
– Paleozoic
– Mesozoic
– Cenozoic
•
•
•
•
P
P
M
C
Precambrian Era
• The origin of Earth
– Prokaryotic (no nucleus)
– Eukaryotic (nucleus, nuclear membrane, internal
organelles) cells
– Invertebrates (have no backbone)
• 4.6 to 543 million years ago
Paleozoic Era
• Cambrian – Modern animal groups – from 543 to 510 million years
ago.
• Ordovician – Colonization of land by plants and arthropods – 510 to
439 million years ago
• Silurian – Jawless, Jawed fishes, and vascular plants – 439 to 409
million years ago
• Devonian – Bony fishes, Amphibians, Insects – 409 to 363 million
years ago
• Carboniferous – Forests, seed plants (fruits), reptiles, amphibians –
363 to 290 million years ago
• Permian – Marine & terrestrial organisms die – newer reptiles,
modern insects – 290 to 245 million years ago
–
–
–
–
–
–
C
O
S
D
C
P
Paleozoic Era
Mesozoic Era
• Triassic – Cone bearing plants (pine trees) ,
dinosaurs – 245 to 206 million years ago
• Jurassic – Cone bearing plants, dinosaurs – 206 –
144 million years ago
• Cretaceous – Flowering plants, ORGANISMS GO
EXTINCT AROUND 65 MILLION YEARS AGO
(CALLED CRETACEOUS EXTINCTIONS). – from 144
to 65 million years ago.
• Dinosaurs lasted for 180 million years (quite
successful.
–T
–J
–C
Mesozoic Era
Cenozoic Era (Tertiary Period)
• Paleocene – Mammals, birds, pollinating insects (bees)
– 65 to 57 million years ago
• Eocene – Flowering plants, modern mammals – 57 to
35 million years ago
• Oligocene – Modern primates – 35 to 25 million years
ago
• Miocene – Modern mammals ,plants – 23 to 5 million
years ago
• Pliocene – Human ancestors – 5 to 1.8 million years
ago
–
–
–
–
–
P
E
O
M
P
Cenozoic Era (Tertiary Example)
Cenozoic Era (Quaternary Period)
• Pleistocene – The ice ages, start of modern
humans – 1.8 million years ago
• Recent – now – recorded time
–P
–R
**Boundaries between Eras are marked by:
– Major changes in life
– Where the oldest appearances happen or
extinctions occur **
Dating Fossils
• Relative Ages – They reflect the order in which groups
of species existed compared to each other.
• Absolute Ages – Actual ages in years.
• Radiometric Dating – Measurement of radioactive
isotopes in objects.
– Determines the absolute age of a fossil.
Half-Life – the number of years it takes for 50 percent of an
isotope to decay.
**Unaffected by temperature, pressure, or other
environmental conditions.
Uranium -238 (half-life of 4.5 billion years) - used to date
rocks of the Cambrian Period, as is not found in living
organisms. Found in lava and volcanic rock. Decays into
Lead -206 – When scientists compare the amount ratio
between Uranium and Lead, they can date the rocks.
Dating Fossils
• Carbon-12 and Carbon-14 (radioactive) are used to
date elements that accumulated when organisms were
alive.
• They measure the ratio of Carbon-12 to Carbon-14 to
calculate how long an organism has been dead.
• Carbon dating only used for current fossils (has a halflife of 5,600 years). If older than 50,000 years, they
have to use Uranium-238.
Continental Drift and Macroevolution
• Continental plates are not locked in plates, but
drift on a thin layer of magma.
• This causes movement of plates known as
Continental Drift, which can cause
earthquakes as plates shift against each other.
• Scientists feel that the continents started as
one massive landmass called Pangaea (all
land), then broke apart over time into
Gondwanaland and Laurasia, then the current
continents over time.
Continental Drift and Macroevolution
• Scientists feel that Continental Drift supports
Evolution, because it is the main way certain
animals (marsupials) could have wound up
where the are at the current time, as they
became geographically isolated.
• There were also changes to water levels,
inland seas, inland climates, etc…
• These changes over time may have caused the
mass extinctions that are spoken about
Continental Drift Example
Mass Extinctions
• In earth’s history, there has been Punctuated Equilibrium,
in that there were long periods of stability with very short
periods of huge species loss. These are known as Mass
Extinction periods.
• Ex: Cretaceous Extinctions (numerous species), Permian
extinctions (marine life loss)
• Scientists think that the extinction of the dinosaurs is
recorded in a meteor crater located in the Yucatan
Peninsula in Mexico – Scientists think the meteor would
have thrown a huge ash cloud in the sky that polluted the
air for months, which would have changed climate, food
(no photosynthesis), breeding, etc…
• There have been 5 or 6 periods of extinction over the last
600 million years according to the fossil record.
• They affect biological diversity, but also lead to Adaptive
Radiation and eventual increases in population due to
Natural Selection.
Mass Extinctions example
What is Taxonomy?
• A branch of biology that involves the
identification, naming, and classification of
species.
• To help with this, all species are assigned a Latin,
scientific name (Genus, species).
• The system most widely used was started by
Swedish botanist Carolus Linnaeus, who came up
with a system that uses two things:
– Two part (binomial nomenclature) Latin naming
system
– A Hierarchy or ordering system of species into broader
and broader groups.
Taxonomy (Con’t)
• Leopard – Panthera pardus – Genus always
capitalized and latin name always in italics.
• The breakdown starts from Kingdom down to
species:
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–
–
–
–
–
–
Kingdom
Phylum
Class
Order
Family
Genus
Species
King
Phillip
Came
Over
For
Good
Spaghetti
Largest (broadest)
Smallest (most specific)
Taxonomy Example
Classification and Evolution
• Darwin did consider Linnaeus’s ideas when
coming up with Natural Selection and
Evolutional Theory.
• A physical diagram that represents
evolutionary relationships among species is
called a Phylogenetic Tree.
Classification and Evolution (Con’t)
• Homologous structures are one of the best features to
indicate how closely organisms are related.
• Ex: Penguin flipper and bird wing – they may look
different and have different functions, but they have
basic similarities in stucture. Also human and
chimpanzee skulls (possibly inherited from a common
ancestor).
• What about when there are not structural similarities?
• Convergent Evolution – the process by which unrelated
species from similar environments have adaptations
that seem similar (analogous structures).
• Ex: The wings of insects vs. the wings of birds (do the
same thing, but are built from entirely different
physical structures.
Example
Molecular Data
• Scientists are now studying the molcular gene
sequences of all species to determine what
species come from common ancestors.
Phylogenetic Trees
• The key feature is in the pattern of branches.
• Can always be expanded
• Splits that occur by the base of the tree are
considered “deeper” and represent how the
species originally split from a common
ancestor.
Clades
•
•
•
•
Each “branch” in this tree is called a clade.
Represents a new evolutionary species.
They can “nest” within larger clades
Each item in an actual clade may be an individual
species, or part of a larger group.
• EVERY clade has an ancestor and ALL
descendants.
Examples
Examples
Cladistics
• The network of branches in a phylogentic tree
can be determined by a method called
cladistics.
• Key feature: All organisms of a clade must
share homologous (same) features that
cannot be found outside that clade.
• The diagram itself is called a cladogram.
• Ex: A cladogram can be based on animals that
all have hair from an ancestor, or all have
teeth for a certain purpose Ex: carnivores.
Surprising finds
• Upon testing genetic material, scientists have
found some surprising things:
– Crocodiles are more closely related to birds than
to lizards or snakes (warm vs. cold blooded and
reptile vs. mammal)
Two vs. Three vs. Five
• Linnaeus proposed a 2 kingdom system: Plants
and Animals
• In 1969, Robert Whittaker propsed a 5
Kingdom classification system: Monera,
Protista, Plants, Fungi, Animals
• In the last 10 years, scientists have come up
with a 3 Domain System (made areas
broader): Bacteria, Archea, Eukaryotes.