5.1 Intro to Theory of Evolution

6.1 Darwin’s Theory of Evolution

Why and how have organisms changed over time???

Think about it from the beginning. . . How do you think all of the creatures we

have today came to be?

True or False All creatures were created by God Humans descended from fish God created the first man and woman God created all creatures the way they

are today Whales used to have legs Birds used to be dinosaurs

True or False Humans have as many genes as chickens We are created in the likeness of God Humans have 99% the same DNA as chimps The thumb is the most important attribute that

separates humans from other creatures God created all the creatures of land and sea in

one day Since we don’t chew with great force, the

human species evolved

Charles Darwin Was a religious man From England At age 22 in 1831, he set sail on a five year trip around the world

Charles Darwin’s Voyage Was ship’s naturalist

Person who studies natural world His job was to learn about living things he

saw on journey Question: why there were so many organisms

that he never saw in England? Observations led to one of the most

important theories of all time

Observations on Journey Diversity

Very different species Fossils

Saw preserved remains of organisms similar but different to organisms alive today

Characteristics of organisms on Galapagos Islands

Galapagos Organisms Galapagos Islands far off coast of S.A. Saw similarities and differences between

organisms on islands and organisms on mainland Ex) iguanas on island large claws to grasp

slippery rocks to feed on seaweed Ex) iguanas on mainland small claws to climb

trees to eat leaves

Galapagos Organisms (cont’d) HYPOTHESIS: species came to island from

mainland and over time offspring became different from mainland relatives

Darwin observed ADAPTATION Adaptation

A trait that helps an organism survive and reproduce

Example Protection porcupine needles, skunk,

poisonous plants

Adaptations of Galapagos Organisms Finches’ Beaks those eating bugs had narrow

thin beaks, but those eating seeds had strong wide beaks

Iguanas those on mainland had smaller claws allowing them to climb trees to eat leaves. Those on island had large claws that allowed them to grip slippery rocks where they eat seaweed

Bird Beak Adaptation Activity Use tweezers to pick up as much ‘birdseed’

as you can in 10 seconds

Then use clothes pin to pick up as much ‘birdseed’ as you can in 10 seconds.

Compare which method is more effective.

Theory of Evolution Back in England, Darwin developed a

scientific theory and studied it for 20 years Theory is a well-tested concept that explains a

wide range of observations Cannot be proved but can be disproved

Called theory of evolution Root: evolve

Theory of Evolution Evolution

Gradual change in a species over time Theory of Evolution

Darwin reasoned that organisms that came to islands faced different conditions than on mainland.

Theorized that species gradually changed over many generations and became better adapted to new conditions

Natural Selection: An Explanation Years later, Darwin and biologist Wallace

offered an explanation how evolution could occur In Darwin’s book The Origin of Species

Video Clip Discovery Education

Natural Selection Natural Selection

Process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species

Factors that Affect Natural Selection Overproduction

Competition

Variation

Factor #1: Overproduction

More offspring are produced than can survive in most species. . . Why?

Frogs lay hundreds of eggs in a year. . .

Factor #2 Competition

Direct and indirect (more indirect) Competition of food, shelter, mates

Factor #3 Variation

Any difference between individuals of the same species

Examples Ex) some fish/turtles swim faster than others Ex) some tigers are more aggressive than others Others????

Role of Genes Variations can result from mutations and

changing of alleles during meiosis

Three Factors lead to NATURAL SELECTION!!! Natural Selection

Some variations are better adapted to environment

These are more likely to survive and reproduce Ex: fastest fish escape their hunters Ex: iguanas that camouflage don’t get eaten

“SURVIVAL OF THE FITTEST”

Selection (cont’d) Strong parents will pass on variations to offspring As time passes, more members will have these

helpful characteristics Environment “selects” organisms with

helpful traits to be parents of next generation Helpful variations increase, unfavorable one

disappear

Example of Evolution Moths used to be very light because bark

was light—camoflague

Industrial Revolution made lots of pollution and soot which made trees dark

Over time moths became darker and darker to blend in with trees

Role of Environment Environmental change can lead to selection

Affects ability of organism to survive

Human Evolution Thought that humans have evolved from

apes There are MANY early versions of the

human Our form is homo sapien

We are still adapting We stand upright which is unusual Back and legs not adapted so we have pains

Pictures of Various “Human Sapiens” https://www.msu.edu/~robin400/ramidus.ht

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When Darwin was alive, the Catholic Church Against Evolution

Catholics vs. Darwin Darwin’s theory would mean Creation Story

is not literal or true People thought God made each creature with an

intended PURPOSE that wasn’t to change Darwin said only ‘purpose’ is to reproduce/survive

Darwin’s theory would mean God did not make everything in this world in seven days

Darwin did NOT say God is not real

Modern Catholic Church No definite stance on evolution of species

of organisms– if they did develop, it was under God’s guidance

Accepts that the biological human form of the body could have developed under God’s guidance but insists on special creation of the SOUL!

Summary There was once only one or a few species–

all the thousands we have today were once these original species– they evolved gradually over time due to natural selection. That is, the “survival of the fittest” led to changes in characteristics