CHAPTER 14 ORIGINS OF LIFE
Spontaneous Generation • for much of history, people believed that animals could come from non-living sources. • this is called abiogenesis • also known as spontaneous generation
Redi’s critics said: • You have excluded AIR • We ALL know that everything needs air • Of course no flies grew! • You haven’t proven anything.
Redi part 2 – answer to critics flies laid eggs on top of mesh no maggots in meat fine mesh allows in air, but not flies
BIOGENESIS • Defintion- all living things must come from other living things • This was now obvious for larger animals-- but what about bacteria???
tight seal loose seal LAZZARO SPALLANZANI’S EXPERIMENT (PG 262) 30 mins • he did TIMED BOILINGS • then left them partially sealed • some partially sealed, some hermetically sealed as in his previous experiment • hypothesized that more boiling should lead to less life 60 mins 90 mins 120 mins
Spallanzani’s results Boiling time had no effect on the broth The broth that was SEALED stayed the freshest for the longest time regardless of boiling time.
Louis Pasteur’s Experiment 1859 (pg 263) • used swan-necked flask • flask allowed in air, but trapped dust (and microbes) • boiled infusion • showed that NO growth occurred, even after many days
pasteur • Pasteur showed that the active principle was NOT damaged • at any later time, he could tip the flask • this allowed nutrient broth to contact the dust • this carried microbes into the broth • result: growth! area where dust had been trapped
DATING of the EARTH EARTH’s estimated age--- more than 4 billion years How have scientist predicted this????
RADIOACTIVE DATING • Using the HALF-LIFES of radioactive material to determine age • HALF-LIFE- the time it takes ½ of the mass of a radioactive isotope to breakdown into it’s non radioactive counterpart • Example • Carbon-14 turning to carbon 12 (half life is 5730 years)
FIRST PROKARYOTES • Probably ARCHAEBACTERIA- that could survive the tough atmospheric and temperature conditions • CHEMOSYNTHETIC- used chemicals to make energy
FIRST PROKARYOTES • Chemosynthetic bacteria slowly gave rise to photosynthetic bacteria • CYANOBACTERIA- first known photosynthetic organism • 3.5 billion year old microfossils have been discovered
FIRST EUKARYOTES • CYANOBACTERIA combining with other prokaryotes- probably gave rise to eukaryotes • ENDOSYMBIOSIS- mutually beneficial joining of two organisms • (example- E. coli and the human intestine)
SCIENTIFIC PROOF OF LIVING ORGANISMS FOSSIL- trace of a long dead organism (examples----bones, teeth, shell, imprints “MOLDS”, footprints,
DATING OF FOSSILS • LAW OF SUPERPOSITION- successive layers of rock or soil are deposited one on top of the other. The lowest layer (STRATUM) is the oldest while the top layer (STRATUM) is the most recent. • RELATIVE AGE- determined by which layer of rock the fossil is found in • ABSOLUTE AGE- more precise age by using radioactive dating (Carbon Dating)
EVIDENCE OF LIFE EXTINCTION- the disappearance of a species MASS EXTINCTION- the disappearance of many species- probably due to a dramatic change in earth’s atmosphere BIOGEOGRAPHY-- comparing present day organisms with fossils from the area (example Armadillo)
DEFINITIONS • POPULATIONS- one species in one place at one time ( can interbreed) • FITNESS- the ability of a species to survive and pass down their genes (how many grandchildren do they have?) • ADAPT- to change genetically in a population to better survive in an environment • ADAPTIVE ADVANTAGE- having a trait that is favorable in an environment
PRINCIPLE OF UNIFORMITARIANISM • Principle that the changes that occur on Earth present day are similar to the changes that have occurred on early Earth
THEORIES OF EVOLUTION • LAMARCK- proposed that similar species descended from a common ancestor • Example– giraffes came from horses • ACQUIRED TRAIT- trait not determined by genes but by the organisms behavior that result in a change in the species • Example– giraffes necks became longer as they started eating leaves off of trees
Charles Darwin • Traveled around the world collecting organisms • Noticed many organisms in each ecosystem were different in form, function and behavior • He believe these differences were hereditary • Developed the term “NATURAL SELECTION” • Species that were best suited to their environment would reproduce more successfully thanother organisms
Darwin’s first theory • DECENT WITH MODIFICATION– newer forms of a species are modified descendants of older species • “One species could actually become many different species”
Darwin’s second theory • MODIFICATION BY NATURAL SELECTION- • Environment determined which individuals passed down traits
NATURAL SELECTION • Defined as the unequal survival and reproduction that results from the presence or absence of particular traits due to competition • Natural selection leads to EVOLUTION
5 Characteristics of Natural Selection 1. Organisms produce more offspring than can survive in the wild (give an example) 2. The environment is hostile and contains limited resources. (food, water, space, and predator/prey) Competition can be between individuals or between species. 3. Organisms differ in the traits that they have. 4. Some traits provide an advantage 5. Each generation contains more organisms with the advantageous traits
EVIDENCE OF EVOLUTION (5) • HOMOLOGOUS STRUCTURES- similar features that originated in a shared ancestor-- example- bones of the hand, number of cervical vertebrae • ANALOGOUS STRUCTURES- similar structures on totally different species with the same function-- Examples- wings on birds and insects
EVIDENCE OF EVOLUTION (5) • 3. VESTIGIAL STRUCTURES- structures that no longer have a functions (example- appendix) • 4. SIMILARITIES IN DNA AND RNA
EVIDENCE OF EVOLUTION (5 • 5. SIMILARITIES IN EMBRYOS • “Embryological development repeats evolutionary history”
ADAPTATION • An inherited trait that increases an organisms chance of survival and reproduction
Adaptive Radiation • One species splitting into many different species
COEVOLUTION • Two species evolving in response to long-term interactions with one another • DIVERGENT EVOLUTION- species become more and more different from one another due to the environment-- can lead to new species • CONVERGENT EVOLUTION- two completely different species becoming more and more similar due to the environment
ARTIFICIAL SELECTION • Defined as Selective breeding by humans for specific characteristics • Examples- breed dogs for hunting, or to be pets (size and behavior) breed plants to produce more food or be resistant to drought or disease
Choose a species • Give an example of it producing too many offspring • Give 2 examples of competition • Give 2 examples of differing traits • Choose one trait that gives an advantage