KEY CONCEPT There were theories of biological and geologic change before Darwin.

1. 10.1 Early Ideas About Evolution KEY CONCEPT There were theories of biological and geologic change before Darwin.

2. 10.1 Early Ideas About Evolution • Theory: proposed explanations for a wide variety of observations (supported by lots of evidence) • Theories about how life exists: • Spontaneous Generation: life comes from non-living things • Biogenesis: only living organisms can produce living organisms

3. 10.1 Early Ideas About Evolution Spontaneous Generation and Biogenesis • Francesco Redi: tested the idea that flies come spontaneously from rotting meat. One of the first scientists to disprove spontaneous generation by showing flies come from flies. • John Needham: tried to disprove Redi’s findings by using his own experiment. Believed he proved spontaneous generation occurs for microorganisms, but did not realize microorganisms could be found in the air. Proved that controls are needed in experiments • Lazzaro Spallanzani: Experiments disproved spontaneous generation by showing that microorganisms will not grow in boiled and sealed gravy but will grow in boiled gravy that is left open to air • Louis Pasteur: his experiments provided the last piece of evidence disproving spontaneous generation. Showed that sterile broth remained free of microorganisms until exposed to air. He confirmed that microorganisms can be found in air. He proved that biogenesis was true.

4. 10.1 Early Ideas About Evolution Early scientists proposed ideas about evolution. • Evolution is the biological change process by which descendants come to differ from their ancestors. • A species is a group of organisms that can reproduce and have fertile offspring.

5. 10.1 Early Ideas About Evolution • Linnaeus: classification system from kingdom to species • Buffon: species shared ancestors rather than arising separately • E. Darwin: more-complex forms developed from less-complex forms • Thomas Malthus: if human population continues to grow, we will run out of food and other resources and there will be a struggle to survive • There were many important naturalists in the 18th century.

6. 10.1 Early Ideas About Evolution • Scientists that influenced Darwin’s work: • Lamarck: theory of acquired characteristics. Some thought you could gain or lose features if you overused or did not use them, and you could pass those traits on to offspring. • Ex. A lizard that didn’t use its legs would eventually not have legs and his offspring wouldn’t • Ex. A giraffe stretched its neck to reach higher leaves, and the stretched neck would be inherited. • Lamarck’s theory was proven to be WRONG! Logically, it doesn’t work. If you had a leg amputated, your children wouldn’t be born with no leg. Features gained in life are not passed on

7. 10.1 Early Ideas About Evolution • Scientists that influenced Darwin’s work: • Charles Lyell: proposed that Earth was a lot older that thought. Processes occurring now have shaped Earth’s geological features over long periods of time. • Alfred Wallace: wrote to Darwin speculating on evolution by natural selection based on his studies of the distribution of plants and animals. Darwin presents Wallace’s essay, and realizes that this applies to all populations of organisms.

8. 10.1 Early Ideas About Evolution Theories of geologic change set the stage for Darwin’s theory. • There were three theories of geologic change. • catastrophism • gradualism • uniformitarianism

9. 10.1 Early Ideas About Evolution • Uniformitarianism is the prevailing theory of geologic change.

10. 12.3 Origin of Life KEY CONCEPT The origin of life on Earth remains a puzzle.

11. 12.3 Origin of Life Earth was very different billions of years ago. • There have been many hypotheses of Earth’s origins. • The most widely accepted hypothesis of Earth’s origins is the nebula hypothesis.

12. 12.3 Origin of Life Chemical evolution – the formation of life from nonliving chemicals. • 4 billion years ago, no oceans existed on Earth. • The earth was very hot so no liquid water existed. • Before living things could evolve, organic molecules like lipids, carbohydrates, amino acids, and nucleotides need to be present. • There are two organic molecule hypotheses.

13. electrodes “atmosphere” water “ocean” heat source amino acids 12.3 Origin of Life Several sets of hypotheses propose how life began on Earth. • There are two organic molecule hypotheses. • Miller-Urey experiment: organic compounds could be made by passing an electrical current (simulated lightning) through a mixture of gases

14. 12.3 Origin of Life Several sets of hypotheses propose how life began on Earth. • There are two organic molecule hypotheses: • meteorite hypothesis: amino acids may have arrived on Earth through meteorite or asteroid impacts.

15. 12.3 Origin of Life • iron-sulfide bubbles hypothesis: around thermal vents in ocean, gases bubble up within iron sulfide chimney structures forming the basic organic compounds within the iron sulfide walls, which acted as the first cell membranes. • There are different hypotheses of early cell structure (cellular evolution).

16. 12.3 Origin of Life • lipid membrane hypothesis: lipid molecules spontaneously form membrane – enclosed spheres (liposomes) in water, which could have formed around a variety of organic molecules and acted as early cell membranes. • There are different hypotheses of early cell structure.

17. 12.3 Origin of Life • A hypothesis proposes that RNA was the first genetic material. • Ribozymes are RNA molecules that catalyze their own replication. • DNA needs enzymes to replicate itself.

18. 12.4 Early Single-Celled Organisms KEY CONCEPT Single-celled organisms existed 3.8 billion years ago.

19. 12.4 Early Single-Celled Organisms Microbes have changed the physical and chemical composition of Earth. • The oldest known fossils (3.5 billion years old) were prokaryotic cells similar to Achaea, which live in extreme environments, such as hot springs or volcanic vents. • Prokaryotic cells such as cyanobacteria, which are photosynthetic autotrophs, evolved and added oxygen to the atmosphere. This led to the evolution of aerobic prokaryotes, and eventually to eukaryotes.

20. 12.4 Early Single-Celled Organisms • Fossil stromatolites provide evidence of early colonies of life.

21. 12.4 Early Single-Celled Organisms Eukaryotic cells may have evolved through endosymbiosis 1.5 – 1.8 million years ago. Theory explains the origin of mitochondria and chloroplasts. • Endosymbiosis is a relationship in which one organism lives within the body of another. • Mitochondria and chloroplasts may have developed through endosymbiosis.

22. 12.4 Early Single-Celled Organisms Eukaryotic cells may have evolved through endosymbiosis. • An early eukaryote may have engulfed an aerobic prokaryote, and instead of digesting it, it remained inside and eventually evolved into mitochondria. • Sometime later, a eukaryote may have engulfed a photosynthetic prokaryote, and instead of digesting it, it remained inside and eventually evolved into chloroplasts. These eukaryotes gave rise to plants and their relatives.

23. 12.4 Early Single-Celled Organisms Eukaryotic cells may have evolved through endosymbiosis. • Early mitochondria and chloroplasts were once simple prokaryotic cells that were taken up by larger prokaryotes • Instead of being digested, some of the prokaryotes may have survived inside the other • The small one could have given energy or sugars and the larger one provided a stable environment

24. 12.4 Early Single-Celled Organisms The evolution of sexual reproduction led to increased diversity. • Genetic variation is an advantage of sexual reproduction. • Sexual reproduction may have led to the evolution of multicellular life. • The correct order of evolution of living things: anaerobic prokaryotes  photosynthetic prokaryotes  aerobic prokaryotes  eukaryotes  multicellular organisms

25. 10.2 Darwin’s Observations KEY CONCEPT Darwin’s voyage provided insight on evolution.

26. 10.2 Darwin’s Observations Charles Darwin proposed theory the of evolution (organic, or biological, evolution). • Darwin set sail around the world in the H.M.S. Beagle. • He made many observations on the Galapagos Islands. • He realized that a huge number of species inhabit the earth. • He was impressed by how well suited they were for whatever environment they inhabited. • Galapagos Islands – small group of islands off the coast of South America that influenced Darwin the most.

27. 10.2 Darwin’s Observations Darwin observed differences among island species. • Variation is a difference in a physical trait. • Galápagos tortoises that live in areas with tall plants have long necks and legs. • Galápagos finches that live in areas with hard-shelled nuts have strong beaks.

28. 10.2 Darwin’s Observations • Species are able to adapt to their environment. • Adaptations can lead to genetic change in a population. • Survival of the fittest = natural selection. • An adaptation is a feature that allows an organism to better survive in its environment.

29. 10.2 Darwin’s Observations Darwin observed fossil and geologic evidence supporting an ancient Earth. • Darwin found fossils of extinct animals that resemble modern animals. • Darwin found fossil shells high up in the Andes mountains.

30. 10.2 Darwin’s Observations • He saw land move from underwater to above sea level due to an earthquake. • Darwin extended his observations to the evolution of organisms.

31. 10.3 Theory of Natural Selection KEY CONCEPT Darwin proposed natural selection as a mechanism for evolution.

32. 10.3 Theory of Natural Selection Darwin proposed natural selection as a mechanism for evolution. • Darwin published On the Origin of the Species in which he proposed a mechanism for evolution he called natural selection. • Organisms are modified during their decent, generation by generation, from common ancestors.

33. neck feathers crop tail feathers 10.3 Theory of Natural Selection Several key insights led to Darwin’s idea for natural selection. • Darwin noticed a lot of variation in domesticated plants and animals. • Artificial selection is the process by which humans select traits through breeding.

34. 10.3 Theory of Natural Selection Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. • Natural selection explains how evolution can occur. • Heritability is the ability of a trait to be passed down. • All species have genetic variation. • Fitness is the measure of survival ability and ability to produce offspring. • Organisms generally produce more offspring than can be supported by the environment, leading to a struggle for existence by competing for resources (food & space) • Some competition would lead to the death of some individuals while others would survive. • Natural selection acts on existing variation within individuals of a species. • Darwin proposed that adaptations arose over many generations.

35. VARIATION OVERPRODUCTION ADAPTATION DESCENT withMODIFICATION 10.3 Theory of Natural Selection Natural selection explains how evolution can occur. • There are four main principles to the theory of natural selection. • variation • Fitness is the measure of survival ability and ability to produce more offspring. • overproduction • adaptation • descent with modification

36. five digits wrist bone 10.3 Theory of Natural Selection Natural selection acts on existing variation. • Natural selection can act only on traits that already exist. • Structures take on new functions in addition to their original function.

37. 10.3 Theory of Natural Selection Evolutionary scientists believe that all new structures have been acquired over time through small, random genetic mutations. • Once these random mutations result in a useful characteristic, natural selection can then act on that trait so that it is passed on to future generations.

38. 10.4 Evidence of Evolution KEY CONCEPT Evidence of common ancestry among species comes from many sources.

39. 10.4 Evidence of Evolution Evidence for evolution in Darwin’s time came from several sources. • Fossils provide evidence of evolution. • Paleontology is the study of fossils or extinct organisms. • Fossils in older layers are more primitive than those in the upper layers.

40. 10.4 Evidence of Evolution • island species most closely resemble nearest mainland species • populations can show variation from one island to another • The study of geography provides evidence of evolution.

41. Larva Adultbarnacle Adult crab 10.4 Evidence of Evolution • identical larvae, different adult body forms • similar embryos, diverse organisms • Embryology provides evidence of evolution.

42. 10.4 Evidence of Evolution Similar Embryos

43. Molefoot Batwing Human hand 10.4 Evidence of Evolution • Homologous structures are similar in structure but different in function. • Homologous structures are evidence of a common ancestor. • The study of anatomy provides evidence of evolution.

44. Human hand Mole foot Bat wing Fly wing 10.4 Evidence of Evolution • The study of anatomy provides evidence of evolution. • Analogous structures have a similar function. • Analogous structures are not evidence of a common ancestor.

45. 10.4 Evidence of Evolution Structural patterns are clues to the history of a species. • Vestigial structures are remnants of organs or structures that had a function in an early ancestor. • Ostrich wings are examples of vestigial structures.

46. 11.1 Genetic Variation Within Population KEY CONCEPT A population shares a common gene pool.

47. 11.1 Genetic Variation Within Population Genetic variation in a population increases the chance that some individuals will survive. • Genetic variation leads to phenotypic variation. • Phenotypic variation is necessary for natural selection. • Genetic variation is stored in a population’s gene pool. • made up of all alleles in a population • allele combinations form when organisms have offspring

48. 11.1 Genetic Variation Within Population • measures how common allele is in population • can be calculated for each allele in gene pool • Allele frequencies measure genetic variation.

49. 11.1 Genetic Variation Within Population Genetic variation comes from several sources. • Mutation is a random change in the DNA of a gene. • caused by mistakes in DNA replication or mutagens. • can form new allele • can be passed on to offspring if in reproductive cells

50. 11.1 Genetic Variation Within Population Genetic variation comes from several sources. • Recombination forms new combinations of alleles. • usually occurs during meiosis (crossing-over) • parents’ alleles arranged in new ways in gametes (gene shuffling). • The 23 pairs of chromosomes can produce 8.4 million different combinations of genes (independent assortment).