Evolution Notes Chapters 14 17 Spontaneous Generation Life

Evolution Notes Chapters 14 -17

Spontaneous Generation • Life generates from Non-Living material – People believed this was true until the late 19 th century – "Law of Biogenesis, " which states that life only comes from previously existing life

Francesco Redi (1626 -1697) • Tried to disprove spontaneous generation using maggots and meat. (see p. 261)

Lazzaro Spallanzani (1729 -1799) • Boiled broth experiment: showed that microbes would not show up in broth that was boiled and sealed (See p. 262). • People were still not convinced

Louis Pasteur (1822 -1895) • He finally settled the dispute over spontaneous generation by using a curved necked flask. (see p. 263)

Pasteur’s other contributions • He solved the mysteries of rabies, anthrax, chicken cholera, and silkworm diseases, and contributed to the development of the first vaccines. • He described the scientific basis for fermentation, wine-making, and the brewing of beer

How do we learn about the past • Earth’s age: estimated at 4. 6 billion years • Radioactive dating: Most elements have several isotopes (same atomic #, different mass) and some of them decay (give off particles or radiant energy or both) and become a “daughter element”

HALF-LIFE • The time it takes for half of the radioactive material to decay is called half-life (Carbon-14 is radioactive and becomes the daughter element N-14) • It takes 5, 730 years for one ½ life of carbon-14

How ½ lives are estimated • The amount of the original material is compared to the amount of the daughter material to determine how many half-lives have passed. This tells scientists how old the organism is (or rock layer)

Earliest forms of life • Had to be anaerobic (low oxygen in the atmosphere) • The oldest microfossils found are prokaryotic (no nucleus) • Most likely used chemosynthesis (energy is obtained from inorganic substances)

Bacteria • Archaebacteria Living today: bacteria that thrive in harsh environments: like earth’s beginning • Cyanobacteria Also alive today: they are capable of photosynthesis About 3 billion years ago organisms like these started putting O 2 in our atmosphere

The first Eukaryotes(1/5) • Endosymbiosis: theory that aerobic prokaryote invaded (like a parasite) inside larger anaerobic prokaryotes. This mutually beneficial relationship evolved into the mitochondria of eukaryotic cells

Fossils • Law of Superposition = rock layers are deposited on other rock layers; therefore older rock is found below younger rock – Relative age: tells that a fossil is younger or older than another fossil Absolute age: tells the exact age of a fossil

Geologic History Mass extinctions: brief periods where large numbers of species disappeared from the rock record: these events defined the different periods and eras of the past

Geologic ages • Precambrian (over ½ billion years ago) – Prokaryotes, then eukaryotes • Paleozoic (500 -245 million years ago) – Invertebrates – Fish – Amphibians – Land plants – reptiles

Geologic ages continued • Mesozoic era (245 – 65 million yrs ago) – Dinosaurs dominate, but become extinct at the end of this era – Mammals arise – Birds arise

Geologic ages continued • Cenozoic era (65 mya – present) – Modern mammals arise – Hominids show up

Jean Baptiste de Lamarck 1829) (1744 - • Developed idea of evolution before the time of Darwin. He explained that species changed by the inheritance of Acquired characteristics • He thought that giraffe Ancestors stretched their Necks to reach the trees Producing offspring with Longer necks

Charles Darwin (1809 -1882) • Sailed on the HMS Beagle • Went to the Galapagos islands – Studied various species of finches along with thousands of other species • Wrote the book “On the Origin of Species” which explained evolution • He coined the term “Natural Selection” (survival of the fittest)

Evidence of Evolution • Homologous features: similar features that originated from a common ancestor

Evidence of Evolution • Analogous features: features that are similar in function but do not come from common ancestry: the wings of bats, birds and insects

Evidence of Evolution • Vestigial structures: structures that may have served a purpose at one time, but no longer have a purpose that is known: • Examples: human tailbone, wisdom teeth and appendix; Pelvic bone in whales; skeletal limbs and pelvis in boa constrictor

Evidence of Evolution • Embryology: humans, pigs, reptiles and birds all have similar stages of embryological growth

Evidence of Evolution • DNA similarities: closer related organisms share more amino acid sequences than more distantly related organisms

Patterns of evolution • Coevolution – The change of 2 or more species in close association with each other • Bats or hummingbirds evolved with the flowers that they pollinate

Convergent evolution • When two dissimilar species evolve to become more similar – Sharks and dolphins have similar structures that nature selected for them even though their origin is very different – Analogous features are the result of convergent evolution

Divergent evolution • Two or more related populations or species become more and more different

Adaptive radiation • Type of divergent evolution • One species (like the Galapogos Finches) become different because of different environmental conditions (like food resources) that they must adapt to

• Divergent evolution caused by humans – Different breeds of dogs were selected and bred from wolves – Traits in horses are selected and bred – Various plants are cultivated with special traits Artificial selection