Origins of Biological Diversity

Chapter 15Page 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 – – 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 half-life 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:– Kingdom King Largest (broadest)– Phylum Phillip– Class Came– Order Over– Family For– Genus Good – Species Spaghetti 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.