1. Ch. 19 History of Life

2. Section 19. 1 The Fossil Record Benchmark: SC. 912. N. 1
Section 19.1 The Fossil Record Benchmark: SC.912.N.1.6- Describe how scientific inferences are drawn from scientific observations and provide examples from the Benchmark being studied.
Key Questions:
1. What do fossils reveal about ancient life?
2. how do we date events in Earth’s history?
3. How was the geologic time scale established and what are it’s major divisions?
4. How have our plants environment and living things affected each other to shape the history of life on Earth

3. Fossils and Ancient Life
An extinct species is one that has died out (ex. Dodo bird, dinosaurs)
Fossils are the most important source of information about extinct species
Fossils can be up to 3.4 billion years old. With this we can see relationships between species back then and now.
Many organisms have died without leaving a trace so the FOSSIL RECORD IS INCOMPLETE!

4. Types of fossils
Fossils can be as large and perfectly preserved as an entire animal, complete with skin, hair, scales, or feathers
Trace fossils- may be impressions made on the substrate by an organism.
Organisms can sometimes leave trace fossils like footprints, burrows, tracks, or even droppings. They also sometimes leave only fragments like teeth or pieces of a jawbone.
Ex: Mummification, amber

5. Fossils in sedimentary Rock
Most fossils are preserved in sedimentary rock.
Sedimentary rock can only form when sediments settle at the bottom of a lake, river, or ocean.
Only hard structures like teeth and bones can be preserved in sedimentary rock

6. What Fossils can Reveal
Structure of the ancient organisms, their environment, and way of life
We can find evolutionary relationships between organisms
Hypotheses form about how structures and species evolved
Ex: Whales have leg bones that could have been used to walk

7. Dating Earth’s History
The fossil record wouldn’t be as useful without a time scale to tell us what happened when.
Researchers use several techniques to date rocks and fossils.
1) Relative Dating
2) Radiometric Dating

8. Relative dating
Relative dating allows paleontologists to determine whether a fossil is older or younger than other fossils.
Index fossils are distinctive fossils used to establish and compare the relative ages of rock layers and the fossils they contain.
Index fossils help establish the relative ages of rock layers and their fossils.
Index fossils that are easily seen are usually the most useful .
Ex: Trilobites

9. Radiometric Dating
Radiometric Dating- relies on radioactive isotopes, which decay into a stable isotopes.
Half-life: time required for half of the radioactive atoms in a sample to decay.
Radiometric dating uses the proportion of radioactive to stable isotopes to calculate the age of a sample.
Ex: Carbon-14 is used to date organisms that lived in the recent past.

10. Geological Time Scale
Geologists and paleontologists have built a time line of Earths history called the geological time scale.
Based on both relative and absolute dating
Major divisions of time scale are eons, eras, and periods

12. Establishing the Time Scale
Early paleontologists placed Earthes rocks and fossils in order according to their relative age.
They used boundaries to determine where one division of geologic time ended and the next began.
The scale is constantly being tested, verified, and adjusted.

13. Divisions of the Geological Time scale
After lots of change over the years, geologists now recognize 4 eons.
The Hadean Eon
The Archean Eon
The Proterozoic Eon
The Phanerozoic
Eons are divided into eras.
Then eras are subdivided into periods

15. Naming the divisions
Geologists started to name divisions of the time scale before any rocks older than the Cambrian Period had been identified.

16. Life on a changing planet
Earths physical environment has undergone striking changes in its history
These changes have affected life in dramatic ways

17. Physical forces
Climate is one of the most important aspects of the physical environment.
Earths climate has been anything but consistent over the years.
Living things have affected each other to shape the history of Earth by-
Building mountains
Opening coastlines
Changing climates
Geological forces have altered habitats of living things repeatedly throughout Earth histoy

18. Biological forces
The first photosynthetic organisms began absorbing carbon dioxide and releasing large amounts of oxygen.
The actions of living organisms over time changed conditions in the land, water, and atmosphere of planet Earth
Plants, animals, and microorganisms are active players in global cycles of key elements, including carbon, nitrogen, and oxygen.

19. Section 19.2-Patterns and Processes of evolution Benchmark: SC.912.L.15.1 EXPLAIN HOW THE SCIENTIFIC THEORY OF EVOLUTION IS SUPPORTED BY THE FOSSIL RECORD, COMPARATIVE ANATOMY, COMPARATIVE EMBRYOLOGY, BIOGEOGRAPHY, MOLECULAR BIOLOGY, AND OBSERVED EVOLUTIONARY CHANGE.
Key Questions
What processes influence whether special and clades survive or become extinct?
How fast does evolution become extinct?
What are two patterns of macroevolution?
What evolutionary characteristics are typical coevolving species?

20. Speciation and Extinction
The study of life's history leaves no doubt that life changed over time.
Some changes occurred in species and some occurred in larger clades over time.
Macroevolutionary patterns are changes in anatomy, phylogeny, ecology, and behavior that take place in clades larger than a single species.

21. Macroevolution and cladistics
Fossils are classified using the same cladistics techniques, based on shared derived characters, that are used to classify living species.
Fossils are arranged into clades that involve both living and extinct organisms.
Cladograms illustrate hypotheses about how closely related organisms are. This does NOT mean that the organisms are direct ancestors.

22. Adaptation and extinction
Throughout the history of life, organisms have faced changing environments.
When environmental conditions change, processes of evolutionary change enable some species to adapt to new conditions and thrive.
If the rate in a clade is equal to or greater than the rate of extinction, the clade will continue to exist.
If the rate of extinction in a clade is greater than the rate of speciation, the clade will eventually become extinct.

23. Patterns of extinction
Some species become extinct because of the slow process of natural selection.
Background extinction is extinction caused by slow and steady process of natural selection.
Mass extinction is an event during which many species become extinct during a relatively short period of time.

24. Rate of evolution
Evidence shows that evolution has often proceeded at different rates for different organisms at different times over the long history of life on Earth.
The 2 models of evolution are gradualism and punctuated equilibrium.

25. Gradualism
Darwin was impressed by the slow, steady pace of geologic change.
He suggested that evolution needed to be slow and steady, which is known as gradualism.
The fossil record shows that many organisms have indeed changed gradually over time.

26. Punctuated equilibrium
Punctuated Equilibrium is the term used to describe equilibrium that is interrupted by brief periods of more rapid change.
The fossil record DOES reveal periods of relatively rapid change in particular group of organisms.

28. Rapid evolution after equilibrium
There are several reasons why evolution might proceed at different rates for different organisms at different times.
Rapid evolution may occur after a small population becomes isolated from the main population.
Rapid evolution may also occur when a small group of organisms migrates to a new environment.

29. Adaptive radiation and convergent evolution
As paleontologists study the fossil record, they look for patterns
Two important patterns of macroevolution are adaptive radiation and convergent evolution.

30. Adaptive radiation
Studies often show that a single species or small group of species has diversified over time into clade containing many species
Adaptive radiation is the process by which a single species or a small group of species evolves over a relatively short period of time into several different forms that live in different ways.
It may occur when species migrate to a new environment or when extinction clears an environment of large number of inhabitants.

31. Convergent evolution
Sometimes, groups of organisms evolve in different places or at different times, but in similar environment.
Evolution produces similar structures and characteristics in distantly related organisms through the process of convergent evolution.
It occurs in both animals and plants.

32. Coevolution
Sometimes the life histories of 2 or more species are so closely connected that they evolve together/
The process by which two species evolve in response to changes in each other over time is called coevolution.
The relationship between the organisms becomes so specific that neither can survive without the other.

34. Flowers and pollinators. Plants and Herbivorous insects
Coevolution of flowers and pollinators is common and can lead to unusual results.
Plants and herbivores also demonstrate close, coevolutionary relationships.

35. 19. 3 Earth’s early history benchmark- SC. 912. L. 15
19.3 Earth’s early history benchmark- SC.912.L.15.8 DESCRIBE THE SCIENTIFIC EXPLANATIONS OF THE ORIGIN OF LIFE ON eARTH
Key Questions
What do scientists hypothesize about early Earth and the origin of life?
What theory explains the origin of eukaryotic cells?
What is the evolutionary significance of sexual reproduction?

36. The Mysteries of Life’s origins
Geological and astronomical evidence suggests that Earth formed as pieces of cosmic debris collided with one another.
Earth’s early atmosphere contained little or no oxygen.
It was principally composed of carbon dioxide, water vapor, and nitrogen, with lesser amounts of carbon monoxide, hydrogen sulfide, and hydrogen cyanide.

37. The first organic molecules
Miller and Urey’s experiment suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds
New experiments based on current ideas of the early atmosphere have also produced organic compounds.

38. Formation of microspheres
Microspheres are not cells, but are similar.
They have selectively permeable membranes through which water molecules can pass.

39. Evolution of RNA and DNA
Scientists have solved the puzzle of the origin of RNA and DNA, but molecular biologists have generated intriguing hypothesis.
Hypothesis proposes that RNA existed by itself before DNA.
From this simple RNA-based system, several steps could have lead to DNA-directed protein synthesis.

40. Production of Free oxygen
Microscopic fossils of prokaryotes that resembles bacteria have been found in Archean rocks more than 3.5 billion years ago.
At first, oxygen combined with iron in the oceans, producing iron oxide, or rust.
Oxygen then began to accumulate in the atmosphere.

41. Origin of eukaryotic cells
One of the most important events in history was the evolution of eukaryotic cells.
Eukaryotes have-
Nuclei
Complex organelles
Mitochondrion

42. Endosymbiotic Theory
Theory that proposes that eukaryotic cells formed from a symbiotic relationship among several different prokaryotic cells.
Idea proposed more than a century ago.
Led to hypothesis that proposes that mitochondrion evolved from endosymbiotic prokaryotes were able to use oxygen to generate energy to reach ATP.
Led to another hypothesis that proposes chloroplast evolved from endosymbiotic prokaryotes that had the ability to synthesize.

43. Modern Evidence Evidence gathered supported the endosymbiotic theory.
Lynn Margulis noted 3 things
1. mitochondrion and chloroplast contain DNA similar to bacterial DNA.
2. mitochondrion and chloroplast have ribosomes whose size and structure closely resemble those of bacteria.
3. mitochondrion and chloroplast reproduce by binary fission when cells containing them divide by mitosis.

44. Sexual reproduction and multicellularity
After eukaryotic cells arose, they began to reproduce.
Sexual reproduction sped up evolutionary chance because sexual reproduction increases genetic variation.

45. Significance of sexual reproduction
When eukaryotes reproduce sexually, offspring receive genetic material from 2 parents.
Meiosis and fertilization shuffle and reshuffle genes, generating lots in genetic diversity.
Genetic variation increases the likelihood of a populations adapting to new or changing environmental conditions.

46. Multicellularity
Evolved a few million years ago after sexual reproduction.
Organisms underwent a series of adaptive radiation, resulting in great diversity.