Chapter 5: Changes Over Time
Section 1: Darwin’s Voyage
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Charles Darwin was 22 years old when he sailed around the world for five years on a ship named the
______________
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During his voyage, he observed ______________and ______________never seen before
He developed an important theory known as: ______________________________________
Darwin’s Observations
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One of the first stops was the coast of ______________
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Here, he saw insects that looked like flowers and huge ants
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In ______________he saw armadillos, as well as bones from giant sloths
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Today, scientists have identified more that 1.7 million ______________of organisms on Earth
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A species is a group of similar ______________ that can mate with each other and have ______________offspring
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In 1835, he reached the Galapagos Islands and found some the greatest ______________of life forms
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He saw giant tortoises (land turtles), seals with fur, and giant lizards
Similarities and Differences
• Darwin was surprised to see that many of the plants and animals on the Galapagos Islands were ______________but
different to those on the mainland of South America
• From observations he made, he inferred (guessed) that some of the plants and animals had come to the islands from
the ______________.
• But how did they get there? He thought maybe they had been blown over during a ______________or drifted on a log.
Adaptations
• One of the most obvious differences among animals he noticed was the bird ______________…many had varied sizes
and shapes
• He noticed that each species was well suited to what it needed to do to ______________
• Beak shape is an example of an ______________, which is a trait helps an organisms survive
Evolution
• For the next 20 years after his trip, Darwin continued to think about his trip and he continued to ______________with
other scientists about his ideas
• Darwin thought the species ______________changed over many generations and became better adapted to the new
conditions
• He called this gradual change ___________________________
• He knew that people could produce ______________ traits in organisms by selective breeding
Chapter 5: Changes Over Time
Natural Selection
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In 1858, Darwin and Russel Wallace proposed an ______________for evolution
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They explained that evolution occurs by ____________________________ …“Survival of the Fittest”
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Natural Selection is the process by which individuals that are better adapted to their environment are more likely to
______________and ______________than other members of the same species.
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Factors that affect this process are:
– ______________: more born than survive
– ______________: fight for resources
– ______________: difference in offspring (helpful variations are passed down to offspring)
The Role of
Genes in Evolution
• Without ______________, all members of a species would have the same traits
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We now know that variations are passed down on genes (______________)
• Because of this, only traits that are ______________, or controlled by genes can be acted upon by Natural Selection
Evolution In Action
• Since Darwin’s book, ___________________________, many scientists have observed natural selection
• In 1977, very little rain fell, and many plants died…so fewer seeds were ______________for the birds to eat
• Instead, birds had to eat bigger seeds that had tougher pods so the birds beaks ______________and some birds died
off
How Do New Species Form?
• Darwin could explain how variations occur, but how does a whole new ______________arrive?
• ______________, or complete separation, occurs when some members are completely cut off from the rest
• This can happen from volcanoes, rivers, mountains, or large waves
• A new species can form when they have been ______________for so long that it ______________new traits
The Continental Drift
• Hundreds of millions of years ago, the ______________were all together
• They were called ______________
• Over millions of years, Pangaea split apart, creating the continents
• A great example of isolation occurring from this is found in ______________, where Kangaroos live
Chapter 5: Changes Over Time
Section 2 : The Fossil Record
• Scientists must act like ______________to understand events from long ago
• Some of the most important clues to Earth’s past are ______________
• A fossil is the preserved ______________or traces of an organism that lived in the past
• Most famous? Probably the ______________!
How Do Fossils Form?
• Usually only the hard parts of an organism body (______________or ______________) remain after death
• The parts of plants that are left after death are usually leaves, stems, roots, or ______________
• Fossil formations are ______________
• Most fossils form when organisms that die become buried in ______________ (particles of soil and rock)
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Sediments are carried by a ______________flowing into a lake or ocean and settle on the bottom
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Over millions of years, the layers cover up the dead organisms and ______________
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______________Fossils: these type of fossils actually become rock
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A ______________is a hollow space in the sediment that shells have left behind when they dissolved.
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A ______________is a copy of the shape of the shape of the organism that made the mold
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Preserved Remains: Entire organisms could be preserved in ______________ (like the elephant-like mammoths) or in
______________.
Determining A Fossil’s Age
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Relative Dating:
– Looking at the ______________of rock that have formed over years…the lower the layer, the older the fossil (does
not tell the actual age of fossils)
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Absolute Dating:
– Will determine the actual age of a fossil…uses ______________
What do Fossils Reveal?
• Fossils help scientists piece together info about the ______________
• All the fossils that have been collected are known as the ____________________________
• The Fossil Record is ______________ (because not all animals leave fossils)
• Almost all fossils are of organisms that are now ______________
• The first animals are believed to have appeared in the ______________about 540 million years ago
• The first ______________are believed to have appeared 410 million years ago
Chapter 5: Changes Over Time
The Geological Time Scale
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This is the ______________of the Earth’s history
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It is split into 4 era’s
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______________Era (1)
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4.6 billion years ago
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87% of Earth’s history is here
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Early bacteria: 3.6 billion years ago
______________Era (2)
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544 million years ago
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First fish
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Early plants
______________Era (3)
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Age of the reptiles
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First birds
______________Era (4)
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First primates
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Flowering plants
How Fast Does Evolution Occur?
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There are two theories
The first, ______________, proposes that evolution occurs slowly but steadily (what Darwin thought)
The second, ____________________________, states that species evolve during short periods of rapid change
Chapter 5: Changes Over Time
Section 3: Other Evidence for Evolution
• While most animals have many of the same ______________, not all of them use them the same way
• Humans do not really need their ______________, but other animals can’t live without it
• Scientists compare body ______________, development before birth, and DNA ______________to determine the
evolutionary relationships among organisms
Similarities in
Body Structure
• An organism’s body structure is its basic body plan, such as how its ______________are arranged
• Vertebrates (fish, amphibians, reptiles, birds, and mammals) have an ______________skeleton with a
______________
• Similar structures that related species have inherited from a common ancestor are called ______________structures.
Similarities in Early Development
• During early development, many organisms look similar
• A fish, a chicken, a pig and a human all have a ______________and tiny ______________slits in their throats when
they are developing
• When these three animals are adults, they look ______________alike
Similarities in DNA
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Scientists think animals look similar while developing because they may have inherited the same genes from a
common ______________
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By comparing the ______________of bases in DNA, they can guess how closely related certain species are
Combining the Evidence
• By combining evidence from ______________, body structures, early development, and DNA, scientists have found
______________evidence.
• A ______________tree is a diagram that shows how scientists think different groups of organisms are related.