what is a scientific theory? – it makes falsifiable predictions with consistent accuracy across a...
TRANSCRIPT
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