Evolution

Unit Question: To what extent does the

environment influence living things over time

Area of Interaction:

Environment

EvolutionEvolution

change change

overover

timetime..

Charles Darwin???

Fact, Fiction, Theory & Law: How are they different?

Fact: something that has actual existence.

Ex. space exploration is now a factb : an actual observable occurrence in our time

Fiction:

a: something invented by the imagination or feigned; specifically : an invented story

b: fictitious literature (as novels or short stories)

c: a work of fiction; especially : NOVEL

Hypothesis: an interpretation of a

situation

a: an educated ‘best guess’

Theory: A well supported testable explanation of phenomena that have occurred in the natural world.a: a plausible or scientifically acceptable general principle

offered to explain phenomena <wave theory of

light>

A Hypothesis becomes Theory when it is supported by a huge body of evidence after lots of

testing.

Law: very much like a theory, less complex

a: a statement of provable scientific knowledge related to a single measurable phenomenon. ie Law of Gravity, Law of thermodynamics

b: specific and measurable

PBS 6 Min Vid

Deep thoughts

• So what is evolution?– Fact or fiction?– Hypothesis, Theory, or Law?– Is evolution debatable?

• How do ideas change over time with new scientific evidence? Give examples.

Evolution• Change over time

• In biology it is the process by which modern organisms have descended from ancient organisms.

50 million years

3 million years ago

Who is Charles Darwin?- Proposed theory to explain evolution- Theory called Natural Selection

Darwin - Early Years

• Terrible student– Medical school at age 16 (Edinburgh, Scotland,

established 1582!-ancient university)

– Skipped class to collect biological specimens

– Sat in on classes in geology and botany

• Father removed Darwin due to lack of academic progress

Darwin – Early Years

• Clergymen - University of Cambridge

• Preferred competitive collecting of beetles, riding, and shooting to studying – but did graduate.

Beetling was the craze at that time…

Darwin – How it all started• Darwin was recommended as a naturalist and

much needed gentleman’s companion to Captain Robert Fitzroy of the H.S.S Beagle

• Two year voyage to chart the coastline of South America

Movie

Sailing the Seas…for five years!

Darwin – the voyage!

• Darwin methodically collected an enormous amount of specimens– Animals, fossils, rocks, etc.

• He also made observations and took detailed notes

• Some key specimens from the Galapagos Islands…

Darwin’s Finches

Galapagos Islands…great place to visit?Blue-footed Booby

Iguanas

Galapagos TortoiseGalapagos Tortoise

Galapagos Islands

What did he see & find?

• He saw:

– Living Organisms and Fossils

• Fossil: preserved remains or evidence of an ancient organism

– Patterns of diversity: organisms are different all over the world and on different islands of the Galapagos

• Patterns of diversity example:Darwin’s Finches

Other Scientists that shaped Darwin’s Ideas

1. Hutton Layers of sedimentary rock form slowly Mountains are pushed up slowly The earth changes slowly!

2. Lyell Darwin read his book right before sailing on the Beagle Volcanoes and erosion we see working today takes

millions of years to make the landscape The earth is older, much older than we think

Other Scientists that shaped Darwin’s Ideas3. Malthus

Population growth and food production are related Overpopulation will occur There will always be competition for food. Those that get food are the most advanced

genetically

4. Lamark 1st to propose a theory of evolution, but his was

WRONG!1. Tendency towards perfection 2. Use and disuse of organs: if you stop using an

organ, it will disappear3. Passing on acquired traits: traits you get in

your lifetime will be passed on to your offspring

• Alfred Wallace writes Darwin– He came up with the same ideas

independently (“I think an organisms structure is related to the environment it lives in”)

• This forced Darwin to publish his book, On the Origin of Species, in 1859

– 21 years after the Beagle voyage!

Movie

So what is Darwin’s Theory?1. There is variation within a species

2. Some traits are helpful, some are harmful. Those that are helpful will help the organism survive. Those that are harmful will cause the organism to die sooner. (natural selection)

3. Those that survive will reproduce others with the same traits

4. Over a LONG period of time, the species gradually changes.

5. All living organisms originated from one common ancestor.

Natural Selection (after genetics)• Genetic mutations occur

during meiosis. • Over time, natural

selection causes changes in the inherited characteristics of a population (the gene pool).

• Changes lead to adaptations and eventually new species!

Movie

Variati on

Variation: The differences in individual organisms in the same

species.

Same Species?

Marine Flatworms

snails

Variation- differences

• Variation is caused by:

–Sexual reproduction (“shuffling the genetic deck”)

–Genetic mutations (error in DNA replication or repair)

Ex: Variation in height among humans

Example: Peppered Moth• Black and White

variations• Live mostly on white

birch trees in England• Birds eat them!

• Birch trees turned black from soot from nearby factories

• Which moth was more likely to survive?

Simulation

Survival of the Fittest = Natural SelectionSurvival of the Fittest = Natural Selection

• Species Overproduce—Most species produce more babies than can survive

• Struggle for existence—Members of each species compete on a daily basis for food, living space, and other necessities

• Fitness—the ability of an individual to survive and reproduce in its environment

• Adaptations- inherited physical features or behaviors that become common in a population because it provides a natural selection advantage

Many animals are brownsMany animals are brownsand grays. Why??and grays. Why??

Some fish lay on the sandSome fish lay on the sandto camoflage.to camoflage.

A deer will lift its white tailA deer will lift its white tail to warn othersto warn others of danger.of danger.

Even eggs and babies can beEven eggs and babies can be camoflaged.camoflaged.

Sometimes an animal will hi-liteSometimes an animal will hi-liteone body part to save another.one body part to save another.

Phototropism -plants grow to light.

Plants have adaptations, too.Plants have adaptations, too.

How is the Ghost Pipefish adapted to its’ environment?

video

Lesson OverviewLesson Overview Evolution as Genetic Change in PopulationsEvolution as Genetic Change in Populations

How do variations become Adaptations?Normal Variation exists as a “bell shaped curve”.

Variations become adaptations when they “increase the chance for survival”.

Lesson OverviewLesson Overview Evolution as Genetic Change in PopulationsEvolution as Genetic Change in Populations

Directional Selection

Directional selection occurs when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. The range of phenotypes shifts because some individuals are more successful at surviving and reproducing than others.

For example, if only large seeds were available, birds with larger beaks would have an easier time feeding and would be more successful in surviving and passing on genes.

Lesson OverviewLesson Overview Evolution as Genetic Change in PopulationsEvolution as Genetic Change in Populations

Stabilizing SelectionStabilizing selection occurs when individuals near the center of the curve have higher fitness than individuals at either end. This situation keeps the center of the curve at its current position, but it narrows the overall graph.

For example, very small and very large babies are less likely to survive than average-sized individuals. The fitness of these smaller or larger babies is therefore lower than that of more average-sized individuals.

Lesson OverviewLesson Overview Evolution as Genetic Change in PopulationsEvolution as Genetic Change in Populations

Disruptive Selection

Disruptive selection occurs when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle. Disruptive selection acts against individuals of an intermediate type and can create two distinct phenotypes.

For example, in an area where medium-sized seeds are less common, birds with unusually small or large beaks would have higher fitness. Therefore, the population might split into two groups—one with smaller beaks and one with larger beaks.

Lesson OverviewLesson Overview Evolution as Genetic Change in PopulationsEvolution as Genetic Change in Populations

Genetic Drift

Genetic drift occurs in small populations when an allele becomes more or less common simply by chance. Genetic drift is a random change in allele frequency.

SpeciationIf Darwin says that we all have a common ancestor,

how do we get new species?

Species: group of similar organisms that can breed and produce fertile

offspring

Speciation: Formation of new species

Members of a species may be born with

Variations- gene shuffling

Mutations- a genetic change

Sometimes those variations/mutations are an adaptation and allow the

individual to survive.

The surviving individual(s) usually reproduce others like them.

Those individuals without the adaptation tend to die off.

Over a very long period of time, the entire species can change to have the adaptation.

A necessary factor in speciation: populations become reproductively isolated

Reproductive Isolation- separating a species in any way so they can’t breed with each other

• Behavioral Isolation- (Different courtship rituals)

• Geographic Isolation- (Separated by rivers, oceans, mountains, etc)

• Temporal Isolation- separated by time (reproduce at different times of the year)

What kind of speciation is this?How are these species related?

Abert Squirrel

Kaibab Squirrel

What kind of speciation is this?

Cicadas that breed every 13 years Cicadas that

breed every 17 years

What kind of speciation is this?

                                                                                 

                                 

The eastern meadowlark (left) and western meadowlark (right) have overlapping ranges. They have different mating songs.

Speciation in Galapagos Island finches

The steps of speciation in Darwin’s finches

1. Bird pushed from mainland and arrive on the islands.

2. Separation of populations

(Geographical isolation)

3. Changes in the gene pool

(Reproductive isolation)

5. Ecological Competition for survival (mainly food)

How do scientists prove speciation occurred? Can’t state it as a fact, only an evidenced theory by:

• Genetic Studies• Studying fossil history• Presumed common ancestors• Observing common traits

What kind of speciation did Darwin observe in the Galapagos?

Evolution Evidence-How do we know it happened?

Key Concept:Darwin argued that living things have been

evolving on Earth for millions of years.

Now we believe it has been 3.5 billion years.

Age of Earth = 5-6 billion

1. Fossil Record

Fossils provide evidence that living things have been evolving for billions of years.

Fossilization Video

4 Main Proofs of Evolution

Archaeopteryx Fossil – 150 million years old

Example:

Oldest dinosaur fossil with feathers – probably evolved into birds.

• The oldest fossils are 3.5 billion years old!

3.4-3.5 billion year old stromatolites composed of cyanobacteria and sediment from the Pilbara Shield of Australia

Video- 11 min

2. Geographic Distribution of Living Species

• Darwin saw similar organisms in different locations.

• He thought: Can these organisms adapt to their local environment and change over time?

Beaver

Muskrat

Beaver and Muskrat

Coypu

Capybara

Coypu and Capybara

3. Similarities in Body Structurea. Homologous structures – parts of different animals that develop from the same body part but have different functions.

Examples: human arm, cat leg, whale fin, bat wing

b. Vestigial Organs – organs that serve no useful purpose. So why

are they there?

             

Organs like: tonsils, appendix, coccyx, wisdom teeth, whale pelvis…

4. Similarities in Early Development

a. Embryos (organisms in the early stages of development) of different animals look very similar. Why?

Why?

1. Not all genes in an organism are turned on at the same time. They have a specific pre-arranged order that all living organism share.

2. As embryos grow, different genes turn on to make them different organisms.

Human EvolutionWe have fossils of our own

species(homo sapiens) dating back 100,000 years. Fossils of close relatives date back some 2 million years. Earlier hominids(primate that walks on 2 feet) date back to 6 million years

What about Us???

Human Evolution

• Australopithecus afarensis- 3 million years ago. Very small skull. Oldest full fossil reconstruction found thus far.

Human Evolution

• Australopithecus africans- 2 million years ago. Ape-like, but bipedal locomotion.

• Homo habilus- 1.8 million years ago. Handy with tools.

Human Evolution

• Homo Erectus-

0.5 million years ago. Thought to be first erect mammals. Wrong!

- Java Man

- Peking Man

Human Evolution

• Homo sapiens- Neanderthal Man-

100,000 years ago. Short, tough hunters.

• Homo sapiens(cont.)

- Cro-Magnon- 50,000 years ago. Hunters and artists. Cave paintings.

- Modern humans- 10,000 years ago. (us)

That’s the story according to scientists, anthropologists and

paleontologists

• Did species evolve? Do they continue to evolve?

• If so, what has caused the changes in species?

So, there are 2 big questions:

1920’s: Scopes Monkey Trial

Met by a new challenger, organized

religion and the creation theory.

Darwin’s Theory of Natural Selection was widely accepted from 1860-early 1900’s by those who thought evolution had occurred.

Creation Theories

A force other than the natural laws of science

causes evolution to occur.

A creation theory may take many forms:

Organized religions (Christianity,

Buddhism, Muslim, etc.) or just a personal

belief.

Today- 2014

Both creationism and natural selection remain popular theories to explain why

and how nature has changed. Many people combine both theories!

What do you think??

Evolution....

a slow gradual process

that ... well, Evolves!!