The document summarizes the process of evolution on Earth over the past 4 billion years. It describes how chemical evolution led to the formation of organic molecules and early life forms like single-celled bacteria over 1 billion years. Biological evolution then produced the diversity of plant and animal species we see today through natural selection and adaptation over the past 3.7 billion years. Key figures like Charles Darwin contributed to the understanding of evolution by natural selection, where traits that aid survival and reproduction are preserved and passed on.

1. Chapter 4

2. Read the Core Case Study on Page 82. Summarize the main ideas and be prepared to discuss.

3. Scientific evidence indicates that the Earth’s life is the result of … 1 billion years of chemical change to form cells. 3.7 billion years of biological change to produce the variety of species we have on Earth today.

4. 1 billion years Organic molecules, bipolymers, systems of chemical reactions Evidence comes from chemical analysis and measurements of radioactive elements in primitive rocks and fossils Lab experiments that show how simple inorganic compounds might have reacted to produce amino acids, sugars, and other organic molecules that became the building blocks for proteins, carbohydrates, RNA and DNA.

5. Followed chemical evolution Uses natural selection Moved from single-celled bacteria to multi-cellular protists, plants, fungi, and animals. This phase is ongoing.

6. Fig. 4-2, p. 84 Variety of multicellular organisms form, first in the seas and later on land Biological Evolution (3.7 billion years) Chemical Evolution (1 billion years) Formation of the earth’s early crust and atmosphere Small organic molecules form in the seas Large organic molecules (biopolymers) form in the seas First protocells form in the seas Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas

7. Charles Darwin (1809 – 1882) Alfred Russel Wallace (1823 – 1913)

8. Fig. 4-3, p. 84 Modern humans appear about 2 seconds before midnight Recorded human history begins about 1/4 second before midnight Origin of life (3.6-3.8 billion years ago) Age of mammals Age of reptiles Insects and amphibians invade the land First fossil record of animals Plants begin invading land Evolution and expansion of life

9. 1859, England, Charles Darwin While on a voyage (HMS Beagle) noticed: Organisms in one population differ slightly from each other in form, function and behavior. Some of the differences are hereditary. Proposed a hypothesis for how species change over time The environment exerts a strong influence over which individuals survive to produce more offspring. Some individuals, because of certain traits, are more likely to survive and reproduce than other individuals.

10. “ Can we doubt…that individuals having any advantage, however slight, over others would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favorable variations, I call Natural Selection.” --- Charles Darwin

11. Natural selection is the process by which individuals that have favorable variations and are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do. Darwin proposed that over many generations, natural selection causes the characteristics of populations to change. Evolution is a change in the characteristics of a population from one generation to the next.

12. All populations have genetic variation. The environment presents challenges to successful reproduction. Individuals tend to produce more offspring than the environment can support. Individuals are better able to cope with the challenges presented by their environment tend to leave more offspring than those individuals less suited to the environment.

14. 13 or 14 separate species of finches collected from the Galapagos Islands All birds are about the same size and color. Most important differences between species are in the size and shape of their beaks. Each beak is highly adapted to different food sources.

15. Large beaks – Crush seeds in beaks Narrow beaks – Eat insects Short, stubby beak – Eats seeds and few insects Sharp beaks – Poke holes in food or pick insects out of cactus

17. Pale coloured, speckled peppered moth

18. Dark coloured peppered moth

19. Peppered moths on tree trunk

20. Populations – not individuals – evolve by becoming genetically different

21. Development of genetic variability Occurs through mutations Exposure to external agents Random mistakes Natural Selection

22. Genetic variability Heritable traits Differential reproduction

23. An adaptation is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions. Natural selection preserves beneficial adaptations and discards harmful adaptations.

24. When faced with environmental change an organism has 3 options: Adapt Migrate Become extinct

25. Genes mutate, individuals are selected, and populations evolve that are better adapted to survive and reproduce under existing environmental conditions.

26. Interacting species can engage in a back-and-forth genetic contest in which each gains a temporary genetic advantage over the other. Changes in the gene pool of one organism can cause changes in the gene pool of another organism. Sometimes the predators surge ahead, at other times the prey get the upper hand.

27. Sometimes different species can crossbreed to form hybrids that can survive and reproduce. Some species can exchange genes without sexual reproduction.

28. A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce.

29. A change in environmental conditions through conventional natural selection only for genetic traits already present in the gene pool. The population’s ability to adapt is limited by its reproductive capacity.

30. Even when a favorable genetic trait is present in a population, most of the population would have to die or become sterile so individuals with the trait can become dominant and pass the trait on through natural selection. Most members of the human population would have to die prematurely for hundreds of thousands of generations in order for a new genetic trait to dominate.

31. Survival of the fittest Organisms develop traits that they need or want Evolution by natural selection involves a grand plan of nature in which species can become perfectly adapted.

32. Evolution through natural selection is about leaving the most descendents Organisms do not develop certain traits just because they need or want them There is no master plan leading to genetic perfection.