What is a scientific theory?– It makes falsifiable predictions with consistent accuracy across a

broad area of scientific inquiry– It is well-supported by many independent strands of evidence,

rather than a single foundation– It is consistent with pre-existing theories and other experimental

results– It can be adapted and modified to account for new evidence as it

is discovered, thus increasing its predictive capability over time.– It is among the most parsimonious explanations, sparing in

proposed entities or explanations.

Review• Macroevolution –

If the changes are over a very long time and are large enough that the population is no longer able to breed with other populations of the original species, it is considered a different species.

• Microevolution – changes to the varieties of individuals in a population

such as a change in a species' coloring or size.• Gene Pool –

all genes in a population• Mutation –

– random change in structure of DNA. Every so often, a mutation is beneficial for survival.

Review• Natural Selection –

a) Genetic variability in a trait within population

b) Trait is heritable

c) Differential reproduction – must enable individuals with the trait to leave more offspring than others without the trait.

Review• Sexual Dimorphism:

– The males & the females of a species have a noticeable physical difference

Review• Speciation –

– The formation of a new species from an ancestral species

• Geographic Isolation – – Species are unable to mate/blend their genes due

to the location(s) of species within a habitat/globally

• Reproductive Isolation – – Behavioral or physiological barriers that prevent

the reproduction between species.

Review• Background Extinction –

– A slow rate of die off, often due to natural selection

• Mass Extinction – – A quick & massive die off of an entire population

or many populations

• Adaptive Radiation – – after mass extinctions, numerous new species

evolve to fill vacated niches. Takes 1-10 million years for adaptive radiation to rebuild biodiversity.

Review• Artificial Selection –

– artificially selecting superior genetic traits– Agriculture, Hatcheries, Pets

• Genetic Engineering – • Gene splicing• Species creation in laboratories• Takes less time than artificial selection

• Age of the Earth – – 4.57 billion years old

Review• Eon Era Period Epoch

• Cambrian Period – – Sudden appearance in the fossil record of

many new phyla (Cambrian explosion)– Abundant marine invertebrates

• Ordovician Period – – Earliest vertebrates appeared

(ostracoderms)– The first plants invaded land

Review• Silurian Period –

– Coral reefs became abundant– First jawed fish appeared (Placoderms)

• Devonian Period – – First fish evolved into tetrapods and invaded

land

– Cartilaginous fish (sharks) became dominant

• Carboniferous Period – – The first reptiles evolved from amphibians

Review• Permian Period –

– Reptiles thrived and began their radiation– Ended with the largest extinction event on

record – 96% of animal species disappeared

• Triassic Period – – Reptiles returned to the seas– Beginning of the radiation of dinosaurs

• Jurassic Period –– Warm climate and high sea levels– First small mammals appeared

– First evidence of feathered birds (Archaeopteryx)

Review• Cretaceous Period –

– Mammals evolved into three forms (monotreme, marsupial, placental)

– all dinosaurs and all ammonites, along with many other species, became extinct

• Tertiary Period – – primitive apes; first elephants– First ancient hominids arose

Review• Quaternary Period –

– Pleistocene: modern humans evolved; ended with the Ice Age that saw the extinction of mammoths and other animals

– Holocene: human civilization spread throughout the globe and humans became the dominant form of life

Review• Tiktaalik roseae – important transitional fossil

discovered in 2005 that connects aquatic species to terrestrial species

Review• Changes in the skull of tetrapods:

– Skull becomes flattened – Eyes move from the side of the head to the top

and to the front– Pectoral girdle (bones around the neck) are

reduced so that the head can turn– Snouts/jaws become elongated– Primary palate expands

Review• Terrestrialization (33 & 34):

– Bones become more dense to support weight without the buoyant force of water

– Fin rays become digits– organization of myomeres (striated muscles) in

fishes (locomotion)– Lungs & pump (diaphragm, buccal pump, etc.)– Thickening of dermis– Body temperature control

Review• Aquatic Mammal Examples:

– Cetaceans, Sirenias, Pinnipeds

• Aquatic/Terrestrial Mammal Similarities:– Endotherms– Placental (belly buttons)– Mothers produce milk– Most have hair at some stage of their

development

Review• Aquatic/Terrestrial Mammal Differences:

– Modified limbs into flippers– Some have reduced pelvises & femurs– Cetaceans have flukes– Cetaceans have nostrils located on the dorsal

portion of their head (blowhole)

Review• Vestigial Features:

– Genetically determined structures that have lost their ancestral function

– Examples:• Femur bones & reduced pelvises in dolphins & whales• Olfactory nodes found in the brains of most cetaceans• Homologous bone structure

• Atavism:– Reverting (genetic error of expression) to an

ancestral type– Examples: Dolphin legs, human tails, chicken teeth

Review• 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

Review• Homologous Structures –

– Similarities in body structures due to common ancestry

• Analogous Structures –– Structures with similar function that do NOT share

common ancestry

Review• Population Genetics –

– The study of genetic changes in populations over time– Quantify molecular differences within and among

populations• Traits exhibit variation

• Gene Flow – – The loss or gain of alleles (genes) in a population

due to migration of fertile individuals or gametes between populations

a)Immigrationb) Emmigration

Review• Genetic Drift –

– a change in allele frequency due to random chance– Affect small populations– Limits alleles available to subsequent generations

• Founder Effect – – Genetic drift attributed to colonization by a limited

number of individuals from a parent population

• Bottleneck Effect – • Genetic drift resulting from the reduction of a population,

typically • by natural disaster, surviving population does not represent

the original• population’s gene pool

Review• Directional Selection –

– 1 extreme is favorable

• Diversifying Selection – – 2 extremes favorable

• Stabilizing Selection – – Intermediate favored

Review• Pre-zygotic Barriers –

– prevent successful fertilization between species

• Post-zygotic Barriers – – allow fertilization but prevent successful

development / reproduction of hybrid.

Review• Habitat Isolation –

– Two organisms that use different habitats even in the same geographic area are unlikely to encounter each other to even attempt mating.

• Behavioral Isolation – – Many species use elaborate behaviors unique to

that species to attract mates.

• Temporal Isolation – – Two species that breed during different times of

day, different seasons, or different years cannot mix gametes.

Review• Mechanical Isolation –

– Physical/ structural mechanism that prevents reproduction

• Reduced Hybrid Viability – – Miscarriage, early death

Review• Reduced Hybrid Fertility –

– Sterile– Unattractive to opposite sex

• Hybrid Breakdown – – 1st generation is viable & fertile– 2nd generation is unviable or infertile– Occurs in plants

• Allopathic Speciation – – A mode of speciation induced when the ancestral

population becomes segregated by a geographic barrier

Review• Parapatric Speciation –

– Takes place in large range– Variable environmental – Variable selection pressure– Non-random mating

• Sympatric Speciation – – Takes place within habitat of parent species– Reproductive barrier forms within a subset of population– Maybe genetic that immediately blocks reproduction– Maybe behavioral

Review

Review• Phylogeny –

– Technique to understand evolutionary relationships

• Phylogenetic Trees –

Review• Convergent Evolution –

– Evolutionary pattern where two or more non related taxonomical groups independently evolved same/similar characteristics

– Similar structures evolve under similar environmental conditions