Changes Over Time

Evolution by Natural SelectionEvolution by Natural Selection

Charles Darwin

Burning Questions…

If there are millions of organisms on earth in every shape, size,

color…

How did they arise?? How did they arise??

How are they related?How are they related? ?

In your own words, describe what YOU think the theory of evolution means…

Darwin’s Theory of Evolution

Evolution, or change over time, is the , or change over time, is the process by which modern organisms have process by which modern organisms have descended from ancient organisms. descended from ancient organisms.

A scientific A scientific theory is a well-supported is a well-supported testable explanation of phenomena that testable explanation of phenomena that have occurred in the natural world.have occurred in the natural world.

How do you think Darwin came up with his theory?

Voyage of the Beagle

Voyage of The Beagle

Dates: Dates: February 12th, 1831February 12th, 1831 ShipShip: H.M.S. Beagle: H.M.S. Beagle Destination:Destination: Voyage around the world. Voyage around the world. Findings:Findings: evidence to propose a evidence to propose a

revolutionary hypothesis about how life revolutionary hypothesis about how life changes over time. changes over time.

Science would never be the same again!Science would never be the same again!

Patterns of Diversity

Darwin visited similary ecosystems and biomes Darwin visited similary ecosystems and biomes around the world and noticed that there sometimes there around the world and noticed that there sometimes there were very different animals living therewere very different animals living there

Neither Argentina nor Australia was home to the Neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands.sorts of animals that lived in European grasslands.

Why aren’t there kangaroos in England?Why aren’t there kangaroos in England?

Living Organisms and Fossils

Darwin collected the preserved remains of Darwin collected the preserved remains of ancient organisms, called ancient organisms, called fossils. .

Some of those fossils resembled organisms that Some of those fossils resembled organisms that were still alive today.were still alive today.

Living Organisms and Fossils   Others looked completely unlike any creature he had Others looked completely unlike any creature he had

ever seen. ever seen.

As Darwin studied fossils, new questions arose. As Darwin studied fossils, new questions arose. Why had so many of these species disappeared? Why had so many of these species disappeared?

How were they related to living species?How were they related to living species?

Fossils

The Galapagos Islands The smallest, lowest islands were hot, The smallest, lowest islands were hot,

dry, and nearly barrendry, and nearly barren -Hood Island-sparse vegetation-Hood Island-sparse vegetation

The higher islands had greater rainfall and The higher islands had greater rainfall and a different assortment of plants and a different assortment of plants and animals-animals- Isabela- Island had rich vegetation.Isabela- Island had rich vegetation.

The Galapagos Island

Darwin was fascinated in particular by the land Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos. tortoises and marine iguanas in the Galápagos.

Giant tortoises varied in predictable ways from Giant tortoises varied in predictable ways from one island to another.one island to another.

The shape of a tortoise's shell could be used to The shape of a tortoise's shell could be used to identify which island a particular tortoise identify which island a particular tortoise inhabited. inhabited.

Animals found in the Galapagos

Land TortoisesLand Tortoises

Darwin FinchesDarwin Finches

Blue-Footed BoobyBlue-Footed Booby

Marine IguanasMarine Iguanas

Animals

Soooo…

Darwin began to hypothesize…

Hypothesis:Hypothesis: Separate species may Separate species may have arisen from an original ancestorhave arisen from an original ancestor

But over time, those species separated But over time, those species separated because of characteristics that developed because of characteristics that developed over time based on the environment where over time based on the environment where the species lived. the species lived.

Evolution by Natural Selection

The Struggle for ExistenceThe Struggle for Existence-members of -members of each species have to compete for food, each species have to compete for food, shelter, other life necessitiesshelter, other life necessities

Survival of the FittestSurvival of the Fittest-Some individuals -Some individuals better suited for the environmentbetter suited for the environment

Natural Selection

VariationVariation-differences among -differences among individuals of a species (Color, size, individuals of a species (Color, size, etc.)etc.)

Caused by mutations or are Caused by mutations or are shaped shaped by conditions in the by conditions in the environmentenvironment

Struggle For Existence & Survival of The Fittest

Nature “selects” certain Nature “selects” certain animals to survive and animals to survive and pass along their pass along their characteristics to the next characteristics to the next generation. generation.

Sometimes variationsGive certain animals or plants an “edge” over others.

They can get stronger, live longer and reproduce

And pass along their goodgenes to their offspring.

Natural Selection Over time, natural Over time, natural

selection results in selection results in changes in inherited changes in inherited characteristics of a characteristics of a population. population.

These changes increase a These changes increase a species’ “fitness” for its species’ “fitness” for its environmentenvironment

AdaptationsAn inherited trait that increases an organism’s An inherited trait that increases an organism’s

chance of surviving, reproducing in its chance of surviving, reproducing in its environment. environment.

Three types:Three types:

Behavioral Structural FunctionalBehavioral Structural Functional *(*(Check out the other ppt on my website!)Check out the other ppt on my website!)

Adaptations help organisms survive:

CamouflageAllows organism to blend in with their

environment

MimicryResemblance of one species to another species

Evidence for Evolution

Vestigial organsVestigial organs-organs that no -organs that no longer serve a useful function in an longer serve a useful function in an organism organism

i.e.) appendix, wisdomi.e.) appendix, wisdom

teeth, 5teeth, 5thth claw on claw on

dog or catdog or cat

Homologous Structures

Body parts of organisms that are Body parts of organisms that are similar in structure and position but similar in structure and position but different in functiondifferent in function

Analogous Structures Body parts that perform a similar function Body parts that perform a similar function

but differ in structurebut differ in structure

Similarities in Early Development - Pharyngeal Pouches