The fossil record and common ancestry

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टीचर्स के लिए: The fossil record and common ancestry (NGSS Middle School Science, Biology) के लिए इस्तेमाल के लिए तैयार लेसन स्लाइड्स, रिवीज़न नोट्स — इन्हें अपने लेसन में इस्तेमाल करें, या टॉपिक को एक इंटरैक्टिव क्लास एक्टिविटी की तरह चलाएं जिसे आपके स्टूडेंट्स लाइव गेम की तरह खेलें।

लेसन नोट्स

Fossil Record Basics

Fossils are preserved remains of ancient organisms, usually hard parts like bones and teeth, but also footprints, burrows, eggs, and amber.
Paleontologists study fossils to learn about past life.
Fossils are found in rock layers; deeper layers are older, so fossil age can be determined by its layer.
The fossil record is the ordered appearance of fossils in rock layers, providing evidence of when organisms lived, evolved, and went extinct.
Fossil record documents existence, diversity, extinction, and change of life forms over Earth's history.

Different types of fossils: amber preserving an insect, stone etching an impression of skin, and a rock preserving a footprint.

Evidence from Rock Layers

Newer rock layers form on top of older ones, so the deepest layers are the oldest.
Consecutive rock layers show different species, indicating change over time.
The Utahraptor fossil, found in 1991, is the largest raptor in Utah and shares traits with modern birds.
Fossils in rock layers help estimate when and how species change over time.

Rock layers with fossils: newer rocks and their fossils sit on top, older rocks and their fossils sit at the bottom.

Common Descent and Evolution

Common descent occurs when different species evolve from a common ancestor.
Paleontologists have found evidence of common descent in the fossil record, supporting the theory of evolution.
Fossils allow comparison of anatomy to determine relationships, when species lived, and when they went extinct.

Similar Structures in Fossils

Scientists group animals into families using skeletal structure, skull size/shape, and teeth.
Example: a modern crocodile skull and the skull of the ancient megalania, one of the crocodile's ancestors, show similar shape and teeth.
Comparing ancient and modern organisms reveals patterns of body structure similarities and differences.

A modern crocodile skull next to the skull of the ancient megalania, one of the crocodile's ancestors.

Uintatherium: A Shared Ancestor

Both the modern elephant and the modern whale are related to the Uintatherium, an animal that lived over 50,000 years ago.
Comparing the Uintatherium skeleton to the elephant skeleton shows similarities in the toes.
Comparing the Uintatherium skeleton to the whale skeleton shows small remnant pelvis and leg bones in the whale, in the same place as the Uintatherium's hip and leg bones.
These shared, matching bone patterns are evidence that elephants and whales are related through a common ancestor, even though they look very different today.

Skeleton of a Uintatherium.

Vestigial Structures

Vestigial structures are leftover body parts that had a function in ancestors but are reduced or unused now.
The human tailbone (coccyx) is a vestigial structure left over from tailed ancestors.
Ostrich wings are vestigial; they are too small for flight, showing change over generations.
Vestigial structures support evolution and show how species have changed over time.

A group of ostriches; their wings are too small to allow flight.

Anatomical Evidence for Relationships

Scientists use bone structures, similarities in teeth, and features of muscle attachment to infer relationships.
Example: the extinct Paraceratherium, which stood over 16 feet tall, has a skeleton that closely resembles the skeleton of a modern white rhinoceros.
Anatomical evidence from fossils helps support the theory of evolution.

A modern white rhinoceros (photo and skeleton) alongside a skeleton reconstruction of the extinct Paraceratherium (bottom).

Comparative Embryology

Comparative embryology is the study of similar patterns among embryos of different species.
Early scientists compared drawings of embryos of several species side by side and found strong similarities in early stages.
All animals with a backbone have gill slits and tails at some point in their embryonic development, even species that never have them as adults.
These embryonic similarities are evidence of common ancestry, though the original comparison drawings were simplified and are still debated.

Embryos of several backbone-having animals side by side at three developmental stages, showing shared early features such as tails.

Embryonic Development in Humans

The human embryonic stage lasts through the eighth week after fertilization.
During weeks 4-8, the embryo grows, becomes more complex, and develops organs, limb buds, and facial features.
By week 8, the human embryo is about 30 millimeters long and has begun to move.
Embryonic similarities across species are evidence of evolution.

Embryonic development from week 4 to week 8: the heart, limb buds, eyes, lungs, and fingers and toes appear in sequence.

Fossil Evidence of Evolution

Horse fossils show evolution: the earliest horses were fox-sized with four long toes and lived in wooded marshlands, eating soft leaves.
As grasslands replaced marshes, horses changed: they became taller, evolved a single large toe that became a hoof, and developed longer molars covered with cement for grinding tough grasses.
Similar fossil evidence documents the evolution of the whale, moving from land into the sea.
Plant fossils show evolution from aquatic green algae to land plants with vascular tissue, seeds, and flowers.

Evolution of the horse: changes in molar teeth, whole-animal size, and forefeet from Hyracotherium to the modern horse.

स्लाइड्स

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साइन अप करें — फ्री लॉग इन

प्रैक्टिस सवाल

फ्री प्रीव्यू — 43 में से 8 सवाल। सभी देखने के लिए साइन अप करें।

1.What is the term for the preserved remains of animals, plants, and other organisms from the distant past?
Easy
- AFossil
- BEmbryo
- CVestigial structure
- DCommon ancestor
2.Paleontologists are scientists who study fossils to learn about life in the past.
Easy
True or false?
3.In the fossil record, which layer of rock contains the oldest fossils?
Easy
- AThe topmost layer
- BThe deepest layer
- CThe middle layer
- DAll layers are the same age
4.Which of the following is NOT a type of fossil?
Easy
- ABones
- BFootprints
- CAmber-preserved insects
- DLiving animals
5.The fossil record provides evidence for when organisms lived, how species evolved, and how some species became extinct.
Easy
True or false?
6.The deepest rock layers are the oldest, so fossils found there are older than fossils in the layers above.
Easy
True or false?
7.Match each type of evidence with its description.
Medium
- Fossil record
- Comparative embryology
- Vestigial structures
- Preserved remains in rock layers showing change over time
- Similarities in the development of embryos
- Leftover structures with no current function
8.Based on the fossil record, put the following events in horse evolution in the order they occurred, from earliest to latest.
Medium
- Horses were fox-sized, had four long toes, and lived in wooded marshlands.
- Grasslands slowly replaced marshes as the climate became drier.
- Horses became taller, which helped them see predators over tall grass.
- Horses evolved a single large toe that became a hoof, helping them run and escape predators.
- Horses evolved longer molars covered with cement, letting them grind tough grasses.

और सवाल

9.Put the following steps in the order they occur in the fossilization process.
Medium
- An organism dies.
- The soft parts of the organism decompose.
- The hard parts, such as bone, are buried and preserved.
- The fossil is later found in a rock layer.
10.Which of the following are commonly preserved as fossils? (Select all that apply)
Medium
- ABones
- BTeeth
- CFootprints
- DSoft tissues
- EDroppings
11.A paleontologist finds a fossil horse in a rock layer that is deeper than a layer containing a fossil of a modern horse. Based on the fossil record, what would the deeper fossil most likely look like?
Medium
- ASmaller, with four toes
- BLarger, with a single hoof
- CIdentical to the modern horse
- DLarger, with four hooves
12.The Paraceratherium became extinct over 23 million years ago. If an animal lived 30 million years ago, how many million years before the Paraceratherium's extinction did it live?
Medium
13.The Paraceratherium became extinct over 23 million years ago. If an animal lived 30 million years ago, how many million years before the Paraceratherium's extinction did it live?
Medium
- A6 million years
- B9 million years
- C7 million years
- D8 million years
14.Match each type of fossil evidence with the evolutionary change it supports.
Medium
- Horse fossils
- Whale fossils
- Plant fossils
- Change from small, four-toed animals to larger, single-hoofed animals
- Movement from land to sea
- Change from aquatic green algae to land plants
15.Explain how the fossil record provides evidence for evolution.
Medium
16.Describe the evidence from the fossil record that shows horses have evolved over time.
Medium
17.Complete the sentence.
Easy
Fossils are usually found in ____.
18.Which of the following is a vestigial structure in humans?
Easy
- ATailbone
- BSkull
- CRib cage
- DKneecap
19.Vestigial structures are structures that have no function in an organism today but were functional in its ancestors.
Easy
True or false?
20.Vestigial structures provide evidence for evolution because they show that a species has changed over time.
Easy
True or false?
21.What is the term for structures that are left over from ancestors but no longer have a function?
Easy
22.Scientists compare skeletal structure, skull size and shape, and type of teeth to determine evolutionary relationships. This is an example of which type of evidence?
Medium
- AEmbryological
- BFossil
- CAnatomical
- DMolecular
23.Both modern elephants and modern whales are linked by fossil evidence to the Uintatherium. Which observation best supports this evolutionary relationship?
Medium
- AThe elephant's toe bones and the whale's remnant pelvis bones both match the Uintatherium's skeleton pattern
- BElephants and whales live in similar habitats today
- CElephants and whales are similar in overall body size
- DElephants and whales eat similar diets
24.Which of the following pieces of evidence link the Paraceratherium and the modern white rhinoceros? (Select all that apply)
Medium
- ABone structures
- BSimilarities in teeth
- CFeatures of muscle attachment
- DIdentical body size
- ESame habitat
25.A scientist finds a fossil skull and teeth similar to a modern crocodile's, but in an older rock layer. What can be inferred from this evidence?
Medium
- AThe fossil organism is a direct ancestor of the modern crocodile.
- BThe fossil organism and the modern crocodile share a common ancestor.
- CThe fossil organism is unrelated to the modern crocodile.
- DThe fossil organism evolved after the modern crocodile.
26.A scientist compares the skeleton of a modern whale with the skeleton of the ancient Uintatherium. Which observations would support the idea that they share a common ancestor? (Select all that apply)
Hard
- ASimilar bone structure in the limbs
- BSimilar tooth patterns
- CSimilar skull size and shape
- DSimilar body size
- ESimilar diet
27.Why are vestigial structures considered evidence for evolution?
Medium
28.Explain how scientists use similarities in body structures to determine evolutionary relationships.
Medium
29.The pictures show the bone structure of the front limbs of a lion, a human, and a frog. Which statement best describes how these front limbs support the theory of evolution?
Medium
- AThe bone structure of the three animals has not changed over time.
- BThe bone structure of the three animals is getting more complex over time.
- CThe bone structure of the three animals was inherited from a common ancestor.
- DThe bone structure of the three animals evolved independently from different ancestors.
30.Embryos of different species show similarities during developmental stages, which is evidence of common ancestry.
Easy
True or false?
31.What is the study of similar patterns among embryos called?
Easy
- AComparative embryology
- BComparative anatomy
- CPaleontology
- DEvolutionary biology
32.Comparative embryology is the study of similar patterns among embryos.
Easy
True or false?
33.All animals that have a backbone have gill slits and tails at some point in their embryonic development.
Easy
True or false?
34.By the eighth week of development, about how many millimeters long is the human embryo?
Easy
35.By the eighth week of development, about how many millimeters long is the human embryo?
Easy
- A27 mm
- B30 mm
- C33 mm
- D36 mm
36.The human embryo is about 30 millimeters long by the eighth week of development. How many centimeters is that?
Easy
37.Which of the following best explains why similarities in embryos provide evidence for common ancestry?
Hard
- AEmbryos are identical in all species
- BSimilarities in embryos suggest shared developmental pathways from a common ancestor
- CEmbryos of different species look different at every stage
- DEmbryos are not affected by evolution
38.A student observes that a human embryo and a fish embryo both have gill slits and tails early in development. What is the best conclusion from this observation?
Medium
- AHumans evolved from fish.
- BHumans and fish share a common ancestor.
- CHumans and fish are the same species.
- DThe gill slits and tails are present in adult humans.
39.Describe how comparative embryology provides evidence for common ancestry.
Medium
40.The chart shows embryonic images of a chicken, a mouse, a crocodile, and a snake, each labeled with skull, vertebrae, limbs, and tail. Which statement can be supported using evidence from the chart?
Medium
- AOnly the crocodile and snake embryos have tails.
- BThe chicken, mouse, and crocodile embryos develop similar outer coverings.
- CEyes are visible at every stage of embryonic development for all four organisms.
- DAll four organisms have limbs at some point during their embryonic development.
41.The Utahraptor and modern birds share many traits. What does this similarity most likely indicate?
Medium
- AThey are the same species
- BThey share a common ancestor
- CThey lived at the same time
- DThey have identical DNA
42.Which of the following are used as evidence that two species share a common ancestor? (Select all that apply)
Easy
- AThe fossil record
- BComparative embryology
- CSimilarities in body structures
- DLiving in the same habitat today
- EEating the same kind of food
43.A graph tracks the number of groups of marine species from 600 million years ago (MYA) to the present. The number of groups rises steadily, then drops sharply about 250 MYA, then rises again to the present. Which claim can be supported by the change in the graph at 250 MYA?
Easy
- ANew species of marine organisms evolved 250 MYA.
- BThe number of marine species groups dropped sharply 250 MYA, then rose again.
- CMany marine organisms migrated to live on land 250 MYA.
- DThe number of marine species groups increased steadily and without interruption.

रिवीज़न नोट्स

## The Fossil Record and Common Ancestry - **Fossil record** shows patterns of existence, diversity, extinction, and change over time. - **Common ancestry** means species share a common ancestor. The more recent the common ancestor, the more closely related the species. - All life on Earth likely descended from a **last universal common ancestor (LUCA)** ~3.9 billion years ago. - Evidence for common ancestry includes: - **Fossils**: show gradual change and transitional forms. - **Anatomical similarities**: homologous structures (same basic form, different functions) suggest shared ancestry. - **Embryological similarities**: embryos of related species look alike. - **Biochemical evidence**: all organisms use DNA, RNA, ribosomes, ATP, etc. Some 23 proteins are found in all organisms; 6,331 genes are common to all animals. - Charles Darwin proposed universal common descent in *On the Origin of Species* (1859). - The fossil record is incomplete, but no reliable observation contradicts common descent. ## Key Terms

fossil record: The collection of all known fossils, showing patterns of life's existence, diversity, extinction, and change over geological time.
common ancestry: The concept that two or more species share a common ancestor; the more recent the common ancestor, the more closely related the species.
last universal common ancestor (LUCA): The most recent common ancestor of all currently living organisms, estimated to have lived about 3.9 billion years ago.
homologous structures: Anatomical features in different species that have the same basic form but may serve different functions, indicating shared ancestry.
embryological similarities: Similarities in the early developmental stages of different organisms, providing evidence for common ancestry.

फ्लैशकार्ड

What does the fossil record show about life on Earth over time?

The fossil record shows that life has existed, changed, and gone extinct over millions of years, with new species appearing and others disappearing.

How do fossils provide evidence for common ancestry?

Fossils show patterns of change over time, with older rocks containing simpler life forms and younger rocks containing more complex forms, suggesting descent from common ancestors.

What is the last universal common ancestor (LUCA)?

LUCA is the most recent common ancestor of all currently living organisms, estimated to have lived about 3.9 billion years ago.

What are two early pieces of evidence for life on Earth?

Biogenic graphite in 3.7 billion-year-old rocks from Greenland and microbial mat fossils in 3.48 billion-year-old sandstone from Australia.

How many groups of genes are common to all living animals?

6,331 groups of genes are common to all living animals, likely from a common ancestor that lived 650 million years ago.

Who first proposed universal common descent through evolution?

Charles Darwin in his 1859 book On the Origin of Species.

What did Darwin mean by 'from so simple a beginning endless forms most beautiful and most wonderful have been evolved'?

He meant that all diverse life forms evolved from one or a few simple ancestors through natural processes over long periods.

What is the idea that all living things are related called?

Common descent or universal common ancestry.

What evidence from biochemistry supports common ancestry?

All known life uses DNA for genetic information, RNA for transcription, and ribosomes for protein synthesis, with shared molecules like ATP for energy.

What is cytochrome c and how does it support common descent?

Cytochrome c is a protein found in many organisms; small differences in its sequence across species reflect evolutionary relationships, supporting common ancestry.

How many proteins are found in all organisms?

About 23 proteins are found in all organisms, serving core functions like DNA replication, indicating a single ancestry.

What does the similarity of embryos across different species suggest?

Embryological similarities, such as early stages of vertebrates having gill slits and tails, suggest they share a common ancestor.

What are homologous structures?

Homologous structures are body parts in different species that have similar underlying anatomy, indicating they evolved from a common ancestor.

Give an example of homologous structures in vertebrates.

The forelimbs of humans, cats, whales, and bats have similar bone arrangements (humerus, radius, ulna) despite different functions, showing common ancestry.

What is the difference between homologous and analogous structures?

Homologous structures share a common evolutionary origin; analogous structures serve similar functions but evolved independently (e.g., bird wings and insect wings).

How does the fossil record show extinction?

Many fossils of species that no longer exist today, like dinosaurs and trilobites, provide evidence of extinction events.

What does the pattern of fossils in rock layers indicate?

Older rock layers contain simpler fossils, and younger layers contain more complex fossils, showing a progression of life over time.

What is a transitional fossil?

A transitional fossil shows traits of two different groups, providing evidence for evolutionary change between ancestral and descendant species.

Name a famous transitional fossil.

Tiktaalik is a transitional fossil between fish and tetrapods, with both fish-like and land animal features.

How do vestigial structures support common ancestry?

Vestigial structures are remnants of organs that had a function in ancestors but are reduced or useless now, like the human appendix or whale pelvic bones.

What does the genetic code's universality suggest?

All organisms use the same genetic code (DNA to RNA to protein), strongly suggesting they share a common ancestor.

What is the significance of the 6,331 genes common to all animals?

These genes are shared across all animal species, indicating they were present in a single common ancestor that lived about 650 million years ago.

How does DNA comparison help determine common ancestry?

By comparing DNA sequences, scientists can measure how closely species are related; more similar DNA indicates a more recent common ancestor.

What is the role of natural selection in common descent?

Natural selection acts on variations, causing populations to adapt and diverge over time, leading to new species from a common ancestor.

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