Lecture Title ( Fossils ) & Date. Main Ideas/Lecture Topics/Questions. Big Ideas or Chunking the Lecture

Transcription

1

2 Lecture Title ( Fossils ) & Date Main Ideas/Lecture Topics/Questions Big Ideas or Chunking the Lecture

3 Fossil Trilobites

4 Point of View #1

5 Natural selection provides a scientific explanation for the fossil record and physical similarities among the diverse species of living organisms. The millions of different species (plants, animals, and microorganisms) that live on Earth today are related because they descended (came) from common ancestors.

6 Natural selection provides a scientific explanation for the fossil record and physical similarities among the diverse species of living organisms. The millions of different species (plants, animals, and microorganisms) that live on Earth today are related because they descended (came) from common ancestors.

7 1. What is a fossil? 2. What are six different ways fossils can form? 3. What three things can fossils tell us? 4. List three weaknesses of the fossil story. 5. Identify and describe the four (4) details that paleontologists can interpret in the fossil record.

8 1. Fossils take different forms 2. Fossils Tell a Story

9 Fossils are found in rocks Fossils are found in amber Fossils can be frozen Fossils can be petrified Fossils can be found in tar & asphalt Trace fossils can tell a story as well

10 Can you name any dinosaurs? Do you know what they looked like or how they moved? Scientists have been able to tell us many things about organisms (such as dinosaurs) that lived millions of years ago. How do scientists learn about these organisms if they ve never seen them?

11 Fossils = the remains or imprints of an organism that lived long ago. Fossils can be formed in five different and direct ways. Trace fossils are indirect evidence of dead organisms.

12 Usually when an organism dies, it begins to decay right away. But sometimes organisms are buried by sediment (earthen material) when they die. Sediment can preserve the organism.

13 Hard parts (shells, teeth, bones) are preserved more often than soft parts (skin, organs). These parts become fossils when the sediment hardens to form a sedimentary rock. Preservation is favored when organisms are buried rapidly in the absence of oxygen. Gentle burial by volcanic ash or mud is best.

14 Fossils are found in rocks Fossils are found in amber Fossils can be frozen Fossils can be petrified Fossils can be found in tar & asphalt Trace fossils can tell a story as well

15 Sometimes organisms (such as insects, frogs, and lizards) are caught in sticky tree sap. If the sap hardens around the insect, a fossil is created. Hardened tree sap is called amber.

16 Fossils are found in rocks Fossils are found in amber Fossils can be frozen Fossils can be petrified Fossils can be found in tar & asphalt Trace fossils can tell a story as well

17

18 Ice and cold temperatures slow down decay. Fossils can be preserved in blocks of ice. Fossils of woolly mammoths (relatives of elephants) that went extinct 10,000 years ago have been found in ice.

19 Fossils are found in rocks Fossils are found in amber Fossils can be frozen Fossils can be petrified Fossils can be found in tar & asphalt Trace fossils can tell a story as well

20 Minerals (containing calcium, silica, and iron) can replace tissues (organs, muscles, skin). In animals, minerals fill the tiny spaces in the hard tissues (like bone). In trees, minerals replace the wood, so the wood becomes rock.

21

22 Fossils are found in rocks Fossils are found in amber Fossils can be frozen Fossils can be petrified Fossils can be found in tar & asphalt Trace fossils can tell a story as well

23 In some places, asphalt can bubble and form sticky pools of tar. La Brea Tar Pits in L.A: ~38,000 years old. These pools have trapped and preserved many different organisms saber-toothed cats dire wolves These fossils might explain what California was like 10,000 to 40,000 years ago.

24 Fossils are found in rocks Fossils are found in amber Fossils can be frozen Fossils can be petrified Fossils can be found in tar & asphalt Trace fossils can tell a story as well

25 Organisms can leave behind clues about their lives that are also fossils. These clues were made by an organism, but they do not include parts of the organism s body. Can indicate Animal s size Speed Way of moving

26 Burrows (shelters made by animals that bury themselves in the sediment) may be filled with sediment and preserved. Coprolites = dung ( poop ) that is fossilized.

27

28 Lecture Title ( Fossils ) & Date Main Ideas/Lecture Topics/Questions Big Ideas or Chunking the Lecture

29 1. Fossils take different forms 2. Fossils Tell a Story

30 Fossils can show scientists three main things: 1) The kind of organism that lived in the past 2) How the environment might have changed 3) How organisms might have changed over time

31 Fossils can show scientists three main things: 1) The kind of organism that lived in the past 2) How the environment might have changed 3) How organisms might have changed over time

32 Fossils can show scientists three main things: 1) The kind of organism that lived in the past 2) How the environment might have changed 3) How organisms might have changed over time

33 Paleontologists are scientists who study fossilized skin, bones, and body parts. They interpret key details of the fossil record to tell the story of the past: 1. Rock layers 2. Index fossils 3. Radiometric Dating (e.g. Carbon-14)

34

35 1. Law of Superposition: Similar fossils can be found in the same rock layer. Lower layers are older than upper layers. Therefore, fossils found in lower layers are thought to be older than those in upper layers.

36

37

38 SHARED TRAITS Flat molars for grinding plants Four legged Lower leg bone similar

39 Paleontologists are scientists who study fossilized skin, bones, and body parts. They interpret key details of the fossil record to tell the story of the past: 1. Rock layers 2. Index fossils 3. Radiometric Dating (e.g. Carbon-14)

40 A fossil that helps identify when certain geologic events happened; the relative date. Usually a species that lived during a short period of time. Certain plankton Graptolites (primitive animals) Ferns

41 Index fossils are found throughout the world and usually live at certain time periods. By matching layers of rock in different places That have index fossils an approx. age is estimated.

42 Paleontologists are scientists who study fossilized skin, bones, and body parts. They interpret key details of the fossil record to tell the story of the past: 1. Rock layers 2. Index fossils 3. Radiometric Dating (e.g. Carbon-14)

43

44 Element Half-Life Use Carbon years Date fossils up to 50,000 years Potassium (K) & Argon (Ar) Uranium (U) 1.3 billion years Date inorganic 4.5 billion years material (no C)

45 At present, we have fossils for about 250,000 species however there must have been many millions of ancient, now-extinct species, and we will not be able to recover fossils for most of them. Thus, our record of past life is incomplete, with built-in biases. (Starr & Taggart. Biology: The Unity & Diversity of Life (302-03))

46 1. Erosion erases the presence of fossilized rocks

47 1. Erosion erases the presence of fossilized rocks 2. Soft-bodied organisms do not easily fossilize

48 1. Erosion erases the presence of fossilized rocks 2. Soft-bodied organisms do not easily fossilize 3. Population and body size skew the story

49 1. Erosion erases the presence of fossilized rocks 2. Soft-bodied organisms do not easily fossilize 3. Population and body size skew the story 4. Remains can be removed from a burial site by scavenging animals

50 1. Erosion erases the presence of fossilized rocks 2. Soft-bodied organisms do not easily fossilize 3. Population and body size skew the story 4. Remains can be removed from a burial site by scavenging animals 5. Many fossil remains are incomplete; putting them together properly can be difficult to impossible

51 1. Erosion erases the presence of fossilized rocks 2. Soft-bodied organisms do not easily fossilize 3. Population and body size skew the story 4. Remains can be removed from a burial site by scavenging animals 5. Many fossil remains are incomplete; putting them together properly can be difficult to impossible 6. Not all environments produce fossils equally well (Starr & Taggart. Biology: The Unity & Diversity of Life (302-03)

52 Point of View #2

53 1. What is a fossil? 2. What are six different ways fossils can form? 3. What three things can fossils tell us? 4. List three weaknesses of the fossil story. 5. Identify and describe the four (4) details that paleontologists can interpret in the fossil record.

54 1. What is a fossil (1)? The remains or imprints of an organism that lived long ago. 2. What are five different ways fossils can form (6)? In rock, amber, ice, asphalt, petrification, trace 3. What three things can fossils tell us (3)? The kind of organism that lived in the past How the environment has changed How organisms have changed 4. List three weaknesses of the fossil story (3). 1. Answers vary 5. ID, describe four details studied by paleontologists (4)? Rock layers: layers deeper in the Earth are thought to be older than younger layers (as well as the fossils found within them) Index fossils: Key species found in the rock layers are used to give a relative date of the rock layer in which they are found. Anatomy: Body parts (limbs, fins, body shape & size) are examined. Homologous parts infer a common recent ancestor but analogous parts infer a less common ancestor. Radiometric dating: the natural decay rate of C, Ar, Kr, and U indicate how old a sample is based on the radioactive element s half-life.