Chapter 5:

The Evolution of Living Things

EvolutionEvolution – change of species over time.

• Fossil –a remain or imprint of once living organisms

• Fossil Record- A historical sequence of life through fossils.

Proof of Evolution: Fossil record shows how the

characteristics of some species have changed over time. • Ex. dog to a horse

Evidence for Evolution #1 Fossils

•One of the few animals for which we have a fairly complete evolutionary record is the horse.

•This is because all the main stages of the evolution of the horse have been preserved in fossil form.

•Over 60 million years, the horse evolved from a dog-sized creature that lived in rainforests into an animal adapted to living on the plains & standing up to 2 meters high.  

Evidence for Evolution #1 Fossils (Continued)

Evidence for Evolution #2 Homologous Structures

• Homologous Structures - Body parts that are similar in related animals.

Proof of Evolution: The similar structures show that we must have a common ancestor!

Evidence for Evolution #3 Vestigial Structures

Proof of Evolution: They are remnants of once useful structures, so they may have been useful to our ancestors.

• Vestigial structures- structures present in modern day organisms but are not even used.

Example: The pelvic bones in the baleen whale show structural changes over time.

Evidence for Evolution #3Vestigial Structures

http://www.youtube.com/watch?v=8cn0kf8mhS4

Video Clip

“Whale Evolution”

Evidence for Evolution #4Molecular Biology

• Molecular Biology – The more closely related the species are to each other, the more similar the DNA is!

• Proof of Evolution: If 2 species have DNA in common, then they must have a common ancestor!

•Similar species of organisms have more common DNA than do organisms that are more different

chimpanzeeorangutangibbonsiamang

humangorilla

Can you tell which of these is human?

•Fetal Similarities: The unborn offspring of many species resemble each other.

•Proof of Evolution: There must have been a common ancestor.

Evidence for Evolution #5 Fetal Similarities

Evidence for Evolution Video Clip

Time 11:22

Recap QuestionsWhat is the change of species overtime?

Evolution

What is the remains or imprints of once living organisms called?

Fossil

What is a historical sequence of life through fossils called?

Fossil Record

What is it called when body parts are similar in related animals?

Homologous Structures

Recap Questions

What are structures that are present in modern day organisms but are not even used.

Vestigial Structures

The more closely related the species are to each other, the more similar the DNA is what type of evidence for evolution?

Molecular Biology

The unborn offspring of many species resemble each other.Fetal Similarities

Recap QuestionsIdentify the piece of evidence for evolution for each example:

• A horse evolved from a dog-sized creature into an

animal adapted to standing up to 2 meters high.  Fossil

• Humans have an appendix, tonsils, eyebrows and wisdom teeth which is not needed for survival

Vestigial Structures

• The unborn offspring of the hog and calf are very similar to each other.

Fetal Similarities

Recap QuestionsIdentify the piece of evidence for evolution for each example:

Molecular Biology

• The baleen whale has a pelvic bone

Vestigial Structures

• Chimpanzees and humans have similar DNA to each other.

• Humans have similar structures to whales, cats, bats, horses and birds.

Homologous Structures

Chapter 5 Section 2:

How Does Evolution Happen?

Charles Darwin’s Theory

Charles Darwin• 1831- Charles Darwin took the British naval ship called

The HMS Beagle, which sailed to the Galapagos Islands.

• He collected thousands of plants and animal samples and kept detailed notes of his observations.

Charles Darwin Observed Finches

He made careful notes about the Finches on different islands…

•Differences in their beak shapes.

•What they ate.

•How they differed from each other as well as from Finches in the surrounding areas!

• Probing bill

• Insect eater

• Feeds in trees

• Probing bill

• Insect eater

• Uses twig to probe insects from cactus

• Crushing Bill

• Cactus seed eater

• Grasping bill

• Insect eater

• Feeds in trees

Galapagos Finches 1970-1990

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big, strong beaks

soft, small beaks

• Darwin studied fossils of animals he had never seen before.

Darwin Studied Fossils

• He observed differences between modern day species and extinct species.

• The tortoises on each of the Galapagos Islands had different characteristics.

Darwin Observed Tortoises

• Examples: Color, Size, Shape, Beak shape

• Darwin talked to farmers who used selective breeding.

Darwin Interviewed Farmers

• Selective Breeding: occurs when desirable traits are chosen by farmers to make sure that these traits are passed down to the next generation.

• Example: Juicy fruits, meatier chickens, higher milk producing cows, etc.

Darwin was puzzled by:• Why are the animals and

plants that live or lived in one area different from the ones that live or lived in other areas?

• Were they once related?

• How did they change?

Darwin’s Questions

Darwin’s Conclusions

• This led him to publish his book called:

• On the Origin of Species

by Natural Selection

• Darwin wrote about his theory on how species change over time called: “The Theory of Natural Selection”

Darwin’s Book

• This is a 4 part theory that states the organisms that are better adapted to their environment survive and reproduce more successfully than less well adapted organisms do.

Darwin’s theory part 1 Overproduction

•Organisms have more offspring than can possibly survive.

Darwin’s theory part 2Inherited Variation

• Variations are caused by mutations.

• Mutation - random changes in our DNA that cause changes. Some of these changes are bad, some are neutral, & some are good.

• If it is bad organism is less likely to mate & pass down the gene. The organism dies along with the mutation that made it less fit.

• If it is neutral, nothing happens. This is what most mutations are.

• If it is good organism is more likely to survive and pass down the gene to their offspring.

Darwin’s theory part 3Struggle to Survive (Competition)

• A natural environment does not have enough resources to keep all offspring alive.

• Offspring have to compete for the following: Food, water, shelter, mates, land, etc.

• Some variations give them an advantage and makes them more likely to survive.

• A variation that makes an organism more likely to survive and reproduce is called: adaptation.

• Examples: physical structures, behaviors for finding food, mating, migrating.

Darwin’s theory part 4Successful Reproduction

• Individuals who survive are more likely to successfully reproduce and pass on the variations that made them more successful.

• Also known as: “Survival of the Fittest”

PRACTICE:Look at each of these

organisms. Determine how Darwin would explain how

they got their characteristics.

How did the giraffe get a long neck?

How did the giraffe get a long neck?

1. Overproduction – lots of giraffes are born

2. Inherited Variation - Some giraffes are born with long necks, some are born with short necks.

3. Struggle to Survive - The giraffes with long necks can reach leaves on trees better. The giraffes with short necks can’t reach leaves, so they will die.

4. Successful Reproduction - The giraffes with longer necks survive and reproduce and pass the long necks on to their offspring.

How did the polar bear get white?

How did the polar bear get white?

1. Overproduction – Many polar bears are born.

2. Inherited Variation - Some polar bears are whiter than others.

3. Struggle to Survive - The bears that are more white can be camouflaged (protected from predators, hidden from prey) better in the snow. The bears that aren’t as white will die from predators or starvation.

4. Successful Reproduction - The bears that are whiter survive, reproduce, and pass the white fur on to their offspring.

How did the cheetah get fast?

How did the cheetah get fast?

1. Overproduction – many cheetahs are born.

2. Inherited Variations - Some cheetahs are faster than others.

3. Struggle to Survive - The faster cheetahs are better at getting prey and escaping predators. The slower cheetahs die.

4. Successful Reproduction -The faster cheetahs survive, reproduce, and pass their speed on to their offspring.

How did cacti get spines?

How did cacti get spines?1. Overproduction – Many cacti are produced.

2. Inherited Variation - Some cacti have spines and some do not.

3. Struggle to Survive - The cacti with spines are protected from animals that want to eat them. The cacti without spines get eaten by animals and die.

4. Successful Reproduction - The cacti that survive reproduce and pass the spines on to their offspring.

How did elks get antlers?

How did elks get antlers?1. Overproduction – lots of baby elk are born.

2. Inherited Variation - Some elk have antlers and some do not.

3. Struggle to Survive - The elk without antlers can’t defend themselves and don’t impress female elks. The elk that don’t defend themselves or mate die and they do not reproduce.

4. Successful Reproduction - The elks with antlers survive and impress females, so they reproduce, passing antlers on to their offspring.

How did flowers get bright colors?

How did flowers get bright colors?1. Overproduction – lots of flowers are produced

2. Inherited Variation - Some flowers have brighter colors than others.

3. Struggle to Survive - The flowers with bright colors are attractive to birds and bees and get pollinated. The flowers that are not bright are attractive and do not get pollinated. They won’t reproduce.

4. Successful Reproduction - The bright flowers survive and pass their bright colors on to their offspring.

How did sharks get sharp teeth?

How did sharks get sharp teeth?

1. Overproduction – lots of sharks are born.

2. Inherited Variation - Some sharks have sharp teeth, and some have dull teeth.

3. Struggle to Survive - The sharks with dull teeth can’t attack pray and eat as well as sharks with sharp teeth. They will die.

4. Successful Reproduction - The sharks with sharp teeth will survive, reproduce, and pass their sharp teeth on to their offspring.

Recap Questions

On the Galapagos Islands, what did Charles Darwin collect and keep samples of?

Plants & Animals

What islands did Charles Darwin sail to?The Galapagos Islands

What was the name of the ship that Charles Darwin sailed on?

The HMS Beagle

Recap Questions

What is the name of the book that Charles Darwin published?

On the Origin of Species by Natural Selection

This occurs when desirable traits are chosen by farmers to make sure that these traits are passed down to the next generation.

Selective Breeding

What organism did Charles Darwin specifically look at including their beak shape, what they ate, and how they differed from each other?

Finches

Recap Questions

What part of Darwin’s Theory is also called Survival of the Fittest?

Successful Reproduction

What are the 4 parts of Darwin’s Theory of Natural Selection called?

Overproduction, Inherited Variation, Struggle to Survive (Competition), Successful Reproduction

Darwin’s Theory states the organisms that are better adapted to their , will survive and reproduce more successfully than less well adapted organisms.

Environment

Recap Questions

What part of Darwin’s Theory that that organisms have more offspring than can possibly survive?

Overproduction

What part of Darwin’s Theory states that there are not enough resources to keep all organism alive so the ones better suited for the environment will survive?

Struggle to Survive (Competition)

What part of Darwin’s Theory states that mutations cause variations among organisms?

Inherited Variation

Recap Questions

A variation that makes an animal more likely to survive and reproduce is called?

Adaptation

What are some things that animals compete for?Food, water, shelter, mates

What are random changes in the DNA that could be good, bad, or neutral?

Mutations

Individuals who survive are more likely to successfully reproduce and pass on the variations that made them more successful is what part of Darwin’s Theory? Successful Reproduction

Chapter 5 Section 3:

Natural Selection In Action

• Populations change due to the environment

• Generation Time - the period between the birth of one generation and the birth of the next one.

• Species with short generation times adapt quickly. • Species - a group of organisms that can mate with one

other to produce fertile offspring.– EX: red eyed tree frogs mate with red eyed tree frogs to make

more red eyed tree frogs

Generation Time

http://www.zo.utexas.edu/faculty/antisense/tree.pdf

Formation of New Species

• Speciation- the formation of a new species as a result of natural selection.

3 Steps to Speciation 1. Separation

2. Adaptation

3. Division

1. Separation- portion of the

population becomes isolated.

• Example: canyon forms, mountain range, volcano, tsunami

Separation

• A population of wild fruit flies minding its own business on several bunches of rotting bananas, cheerfully laying their eggs in the mushy fruit…

Example - Separation

• Disaster strikes: A hurricane washes some of the bananas and the immature fruit flies they contain out to sea. The banana bunch eventually washes up on an island off the coast of the mainland.

• The fruit flies mature and emerge from their slimy nursery onto the lonely island. The two portions of the population, mainland and island, are now too far apart to reproduce with each other.

• At this point, speciation has not occurred—any fruit flies that got back to the mainland could mate and produce healthy offspring with the mainland flies.

Example – Separation (Continued)

2. Adaptation- the part of the population that got separated has a different environment to adapt to.

Adaptation

• The populations diverge: Ecological conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does.

• Morphology, food preferences, and courtship displays change over the course of any generations of natural selection.

Example - Adaptation

3. Division– over hundreds to thousands of generations, the 2 groups became so different that they are no longer the same species and can no longer interbreed.

Division

• So we meet again: When another storm reintroduces the island flies to the mainland, they will not readily mate with the mainland flies since they’ve evolved different courtship behaviors.

• The few that do mate with the mainland flies, produce eggs that can’t hatch because of other genetic differences between the two populations.

• The lineage has split now that genes cannot flow between the populations.

Example - Division

• The Kaibab squirrel (left) became isolated in the Grand Canyon approx. 10,000 years ago. Features have gradually evolved that separate it from close relative, the Abert squirrel (right) .

Speciation of Squirrels

Croatian Lizards• Experiment: Scientists placed 5 pairs of insectivorous

species in a new island habitat.• Old island habitat very little plants but plenty of insects

– (Lizards diet was 93% insects, 7% plants)

• New island habitat had an abundance of plants, but limited insects.

• After 80 generations, the lizards diet was 36% insect & 64% plant

In a few decades the lizards have developed:

• New digestive structure• Larger heads• Harder bite

Galapagos tortoise• All subspecies of Galapagos tortoise evolved from a common ancestor that arrived from mainland South America about 6-12 million years ago.

• A volcano formed the oldest Galapagos Island. Tortoises that arrived there colonized the island.

• The distance between the islands prohibited much inter-breeding and resulted in independent evolution of the populations.

“A small basic Journey of how Evolution Happens”

Video Clip

Time 5:48