Evolutionary History and Relationships

Evolutionary History and Relationships

Middle School

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Learning Objectives

• Analyze the fossil record to find patterns of existence, diversity, and extinction.

• Use anatomical similarities to infer relationships between modern and fossil organisms.

• Compare embryological development to identify relationships not seen in adult organisms.

• Explain how biogeography and fossil dating methods provide evidence for evolution.

Key Vocabulary

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Fossil Record

The fossil record is the complete collection of all the fossils that have ever been discovered.

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Common Ancestor

A common ancestor is a predecessor species from which different groups of organisms have evolved.

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Sedimentary Layers

Sedimentary layers are the distinct layers of rock where fossils are most commonly found and preserved.

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Relative Dating

Relative dating is a method used to determine a fossil's approximate age by its rock layer position.

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Radioactive Dating

Radioactive dating is a method for finding the precise age of a fossil using radioactive decay.

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Homology

Homology refers to a fundamental similarity between different species that suggests evidence of a shared ancestry.

Key Vocabulary

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Anatomical Structures

Anatomical structures are the various physical parts that make up an organism's body, like bones and organs.

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Embryological Dev

Embryological development is the study of how an organism grows and changes before its birth.

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Biogeography

Biogeography is the scientific study of how and why different species live in various parts of the world.

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Extinction

Extinction is the complete and permanent dying out of a species, so none are left anywhere on Earth.

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Evolutionary Descent

Evolutionary descent is the process by which species change over generations as they inherit traits from their ancestors.

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The Fossil Record: A History of Life

• The fossil record is the total collection of fossils arranged in chronological order.

• It documents the existence, diversity, change, and extinction of life over time.

• Found in rock layers, older fossils are deeper and show simpler life.

• The record shows mass extinctions followed by the appearance of new species.

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Multiple Choice

What is the fossil record?

• The total collection of fossils arranged in chronological order.

• A list of all currently living species on Earth.

• A single, complete dinosaur skeleton.

• A book describing the different types of rocks.

Multiple Choice

What does the arrangement of fossils in rock layers reveal about the history of life?

• Fossils found in deeper layers are older and represent simpler life forms.

• Fossils found in deeper layers are younger and represent complex life forms.

• The depth of a rock layer does not provide any information about the fossil.

• Fossils in shallow layers are always from marine animals.

Multiple Choice

Based on the patterns of change and extinction found in the fossil record, what is the most logical conclusion about life's history?

• Life on Earth has become more diverse and complex over long periods.

• All species of organisms appeared on Earth at the same time.

• The oldest life forms were identical to the life forms that exist today.

• Mass extinctions prevent new types of species from appearing.

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Dating Fossils: Relative and Radioactive

Relative Dating

• This method determines a fossil's age by comparing its position in sedimentary rock layers.

• In undisturbed rock, older fossils are in deeper layers and younger ones are in shallower layers.

• It provides a relative age, not an exact number of years for the fossil.

Radioactive Dating

• This method provides a more precise, absolute age in years for a fossil.

• It measures the decay of radioactive elements within the fossil or the surrounding rock.

• The rate of decay for these elements is known and constant, acting like a clock.

Multiple Choice

What is the primary difference in the information provided by relative dating versus radioactive dating?

• Relative dating gives a comparative age, while radioactive dating gives a precise age.

• Relative dating uses radioactive elements, while radioactive dating uses rock layers.

• Relative dating is more accurate than radioactive dating.

• Relative dating provides an exact age, while radioactive dating provides a comparative age.

Multiple Choice

How does the position of a fossil in undisturbed rock layers help determine its age?

• Fossils in deeper layers are generally older than fossils in shallower layers.

• The color of the rock layer indicates the exact age of the fossil inside.

• Fossils found closer to the surface are typically the oldest.

• The number of fossils in a layer determines how old that layer is.

Multiple Choice

A scientist discovers a fossil and needs to determine its exact age in years to understand when the organism lived. Which method should be used and why?

• Radioactive dating, because it measures the decay of elements to provide a precise age.

• Relative dating, because comparing its rock layer to others is the most accurate method.

• Relative dating, because it can determine the fossil's age by its depth in the ground.

• Radioactive dating, because it compares the fossil to other fossils in the same rock layer.

Anatomical Evidence: Homologous Structures

• Homologous structures are similar anatomical features that suggest a common ancestor.

• Human, bat, and whale forelimbs have different functions but similar bone structures.

• Organisms with more homologous structures are considered more closely related.

Multiple Choice

What is the primary significance of homologous structures?

• They suggest a common ancestor.

• They perform the exact same function.

• They are found only in animals that live in the same habitat.

• They have completely different bone structures.

Multiple Choice

What is the relationship between the structure and function of the forelimbs in humans, bats, and whales?

• They have different functions despite having similar structures.

• They are used for the exact same purpose in each animal.

• They are made of completely different types of bones.

• They only appear in animals that are unrelated.

Multiple Choice

Based on the evidence of homologous structures, how would a scientist determine which two organisms are the most closely related?

• The two organisms with more homologous structures are more closely related.

• The two organisms with fewer homologous structures are more closely related.

• All organisms are considered equally related, regardless of homologous structures.

• Homologous structures cannot be used to determine how related organisms are.

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Embryological Evidence for Evolution

• Comparing embryos of different species reveals surprising similarities.

• Early vertebrate embryos, including humans, have gill slits and a tail.

• In fish, these gill slits develop into gills; in humans, they disappear.

• These shared patterns suggest that these species share a common ancestor.

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Multiple Choice

What is the primary conclusion suggested by the surprising similarities observed among the early embryos of different species like humans and fish?

• These species share a common ancestor.

• All species develop at the exact same rate.

• Adult animals look identical to their embryos.

• Fish evolved from early human ancestors.

Multiple Choice

How does the development of gill slits in human embryos compare to their development in fish embryos?

• They develop into gills in fish but disappear during human development.

• They develop into lungs in both humans and fish.

• They disappear completely in both humans and fish.

• They develop into a tail in humans and gills in fish.

Multiple Choice

If scientists discovered a new land animal whose embryo has a tail and gill slits, what would be the most logical conclusion based on this evidence?

• The organism will be a type of fish when it is born.

• The organism likely shares a common ancestor with other vertebrates.

• The organism will keep its gill slits throughout its adult life.

• The organism's development is completely unique and unrelated to other species.

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Molecular Evidence for Evolution

• Similarities in DNA and proteins show how closely related different species are.

• Woolly mammoths and elephants share very similar mitochondrial DNA, showing a close relationship.

• The universal genetic code used by nearly all life suggests a common ancestor.

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Multiple Choice

What do similarities in the DNA and proteins of different species reveal to scientists?

• How closely related different species are

• What diet different species consume

• The exact age of each species

• The habitat where different species live

Multiple Choice

The mitochondrial DNA of woolly mammoths and elephants is very similar. What does this specific evidence suggest about their relationship?

• They lived in the same environment

• They share a close common ancestor

• They were identical to each other

• They ate the exact same types of food

Multiple Choice

The fact that nearly all organisms use the same universal genetic code to build proteins is strong evidence for which conclusion?

• All living things have the exact same DNA sequence

• The environment has no effect on an organism's DNA

• Most forms of life on Earth likely evolved from a common ancestor

• Simple organisms like bacteria do not have DNA or proteins

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Evidence from Biogeography

• Biogeography is the study of how species are distributed across the planet.

• These distribution patterns provide strong evidence for the theory of evolution.

• Continental drift caused geographical isolation, which separated populations of different species.

• Australia's marsupials evolved in isolation after separating from the supercontinent Pangaea.

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Multiple Choice

What is the definition of biogeography?

• The study of how animals behave in their habitats.

• The study of how different species are distributed across the planet.

• The study of fossils to understand ancient life.

• The study of how continents have moved over time.

Multiple Choice

According to the principles of biogeography, what is the primary way that continental drift influenced the evolution of species?

• It caused all species to mix together.

• It stopped evolution from happening.

• It separated populations, which then evolved in isolation.

• It only affected the distribution of plants, not animals.

Multiple Choice

Scientists discover two large landmasses separated by an ocean. On both landmasses, they find species that are related but have distinct differences. What is the most likely conclusion based on this evidence?

• The animals must have migrated across the ocean to the other landmass.

• The two landmasses were once connected, and the species evolved differently after being geographically isolated.

• The similar environments on each landmass caused identical species to evolve.

• One species is much older than the other and is not related.

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Common Misconceptions

Misconception	Correction
Evolution is a linear ladder of progress.	Evolution is a branching tree, not a straight line.
The fossil record is a complete history of all life.	The fossil record is incomplete as fossilization is a rare event.
Organisms that look alike must be closely related.	Anatomical structure, not just appearance, shows relationships.

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Summary

• The fossil record shows patterns of change, extinction, and increasing complexity over time.

• Homologous structures and embryological similarities provide strong evidence for common ancestry.

• Molecular evidence, such as DNA similarities, confirms evolutionary relationships.

• Biogeography explains how geographical isolation drives the evolution of new species.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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• 3

• 4