AP Biology Origin of Life “…sparked by just the right combination of physical events & chemical processes…” Thank you to Kim Foglia for her hard work an d dedication n to AP Biology

AP Biology What do we know? Group up! What do we know about early Earth? How do we know? What were the earliest organisms and why? What changed so that we know have millions of organisms?

AP Biology BacteriaArchae- bacteria AnimaliaFungiProtistaPlantae Formation of earth Molten-hot surface of earth becomes cooler Oldest definite fossils of prokaryotes Appearance of oxygen in atmosphere Oldest definite fossils of eukaryotes First multicellular organisms Appearance of animals and land plants Colonization of land by animals Paleozoic Mesozoic Cenozoic Millions of years ago ARCHEAN PRECAMBRIAN PROTEROZOIC The evolutionary tree of life can be documented with evidence. The Origin of Life on Earth is another story… The evolutionary tree of life can be documented with evidence. The Origin of Life on Earth is another story…

AP Biology Which of the following organisms alive today is likely the most similar to the first forms that evolved on the earth? a. methane-producing bacteria b. Cyanobacteria c. Algae d. Dinosaurs e. humans

AP Biology Which of the following gases is least likely to have existed in the early atmosphere the earth? a. NH3 b. CO2 c. N2 d. H2O e. O2

AP Biology What is Life?  First we have to define LIFE…  organized as cells  respond to stimuli  regulate internal processes  homeostasis  use energy to grow  metabolism  develop  change & mature within lifetime  reproduce  heredity  DNA / RNA  adaptation & evolution

AP Biology The Origin of Life is Hypothesis  Special Creation  Was life created by a supernatural or divine force?  not testable  Extraterrestrial Origin  Was the original source of organic (carbon) materials comets & meteorites striking early Earth?  testable  Spontaneous Abiotic Origin  Did life evolve spontaneously from inorganic molecules?  testable

AP Biology Early Earth and Plate Tectonics

AP Biology Presumably, Pangea was ripped apart by such continental rifting & drifting.

AP Biology Tectonic Plates on Modern Earth

AP Biology Conditions on early Earth  Reducing atmosphere  water vapor (H 2 O), CO 2, N 2, NO x, H 2, NH 3, CH 4, H 2 S  lots of available H & its electron  no free oxygen  Energy source  lightning, UV radiation, volcanic

AP Biology Water vapor Condensed liquid with complex, organic molecules Condenser Mixture of gases ("primitive atmosphere") Heated water ("ocean") Electrodes discharge sparks (lightning simulation) Water Origin of Organic Molecules  Abiotic synthesis  1920 Oparin & Haldane propose reducing atmosphere hypothesis  1953 Miller & Urey test hypothesis  formed organic compounds  amino acids  adenine CH 4 NH 3 H2H2

AP Biology Of the following ___________ was not contained in the Miller-Urey original mixture? a. Water b. Nitrogen c. Hydrogen d. phosphorus

AP Biology Stanley Miller University of Chicago produced -amino acids -hydrocarbons -nitrogen bases -other organics

AP Biology Origin of Genetics  RNA is likely first genetic material  multi-functional  codes information  self-replicating molecule  First molecule of heredity  natural selection & evolution  enzyme functions  Ribozymes (RNA enzyme that can catalyze a reaction)  replication  regulatory molecule  transport molecule  tRNA & mRNA Dawn of natural selection

AP Biology Key Events in Origin of Life  Key events in evolutionary history of life on Earth  life originated 3.5–4.0 bya

AP Biology Prokaryotes  Prokaryotes dominated life on Earth from 3.5–2.0 bya 3.5 billion year old fossil of bacteria modern bacteria chains of one-celled cyanobacteria

AP Biology Oxygen atmosphere  Oxygen begins to accumulate 2.7 bya  reducing  oxidizing atmosphere  evidence in banded iron in rocks = rusting  makes aerobic respiration possible  photosynthetic bacteria (blue-green algae)

AP Biology First Eukaryotes  Development of internal membranes  create internal micro-environments  advantage: specialization = increase efficiency  natural selection! infolding of the plasma membrane DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell endoplasmic reticulum (ER) nuclear envelope nucleus plasma membrane ~2 bya

AP Biology Endosymbiosis Ancestral eukaryotic cell Eukaryotic cell with mitochondrion internal membrane system aerobic bacterium mitochondrion Endosymbiosis  Evolution of eukaryotes  origin of mitochondria  engulfed aerobic bacteria, but did not digest them  mutually beneficial relationship  natural selection!

AP Biology mitochondrion chloroplast Eukaryotic cell with chloroplast & mitochondrion Endosymbiosis photosynthetic bacterium Endosymbiosis  Evolution of eukaryotes  origin of chloroplasts  engulfed photosynthetic bacteria, but did not digest them  mutually beneficial relationship  natural selection! Eukaryotic cell with mitochondrion

AP Biology  Evidence  structural  mitochondria & chloroplasts resemble bacterial structure  genetic  mitochondria & chloroplasts have their own circular DNA, like bacteria  functional  mitochondria & chloroplasts move freely within the cell  mitochondria & chloroplasts reproduce independently from the cell Theory of Endosymbiosis

AP Biology The endosymbiotic theory explains a. the origin of all organelles in eukaryotic cells b.How bacterial cells can invade eukaryotic cells and cause disease. c.How mitochondria and chloroplasts originated from free-living cells d.How eukaryotic cells consume food

AP Biology Cambrian explosion  Diversification of Animals  within 10–20 million years most of the major phyla of animals appear in fossil record 543 mya

AP Biology Kingdom Protista Kingdom Fungi Kingdom Plantae Kingdom Animalia Kingdom Archaebacteria Kingdom Bacteria

What is Evolution? Change in the genetic makeup of a population over time. Fitness – those with favorable variations for survival and reproduction. – Populations can evolve, not individuals. Diverse gene pool good for long-term survival of a species. Genetic variations are important! How do genetic variations occur?

AP Biology Where does Variation come from?  Mutation  random changes to DNA  errors in mitosis & meiosis  environmental damage  Sexual reproduction  mixing of alleles  genetic recombination  new arrangements of alleles in every offspring  new combinations = new phenotypes

Genetic variation in a population

AP Biology Essence of Darwin’s ideas  Natural selection  heritable variation exists in populations  over-production of offspring  more offspring than the environment can support  competition  for food, mates, nesting sites, escape predators  differential survival  successful traits = adaptations  differential reproduction  adaptations become more common in population

AP Biology Lamarckian vs. Darwinian view  LaMarck  in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring  Darwin  giraffes born with longer necks survive better & leave more offspring who inherit their long necks