Unit 1 NOS/Evolution PPT #7 Evolutionary Theory

Evolution= Gradual change over time

Charles Darwin in 1871 PERHAPS no one has influenced our knowledge of life on Earth as much as the English naturalist Charles Darwin ( ).

Who was Charles Darwin Studied medicine Studied medicine Hated the sight of blood Hated the sight of blood Received a BA in Theology Received a BA in Theology Had 10 children Had 10 children Darwin was a Naturalist Darwin was a Naturalist on the HMS Beagle on the HMS Beagle

The 2 theories during the 1850’s about Evolution Jean Baptist Lamarck (French) Early 1800’s vs. Charles Darwin (English) Mid 1800’s

Jean Baptiste Lamarck He Hypothesized: He Hypothesized: Evolution occurs as structures develop through use, or disappear because of disuse, and these “acquired characteristics” are passed to offspring. are passed to offspring. EXAMPLE: Over a giraffes lifetime it can stretch it’s neck and it’s offspring will be born with long necks…. Valid?

Charles Darwin He Hypothesized : He Hypothesized : Evolution occures due to gradual changes in populations over generations. (Evolving traits) Evolution occures due to gradual changes in populations over generations. (Evolving traits) Darwin referred to such change as “descent with modification” – evolution; Darwin referred to such change as “descent with modification” – evolution; Wrote Origin of Species He still wondered He still wondered “How does evolution occur?”

While traveling Darwin noticed slight differences within species and developed his Theory of Evolution

In The Galapagos Islands, Darwin collected species of finches (13) In The Galapagos Islands, Darwin collected species of finches (13)Galapagos IslandsGalapagos Islands Each had a specialized diet and beak structure Each had a specialized diet and beak structure These finches all closely resembled a South American finch ancestral species These finches all closely resembled a South American finch ancestral species On the trip Darwin saw things he could only attribute to a process called: On the trip Darwin saw things he could only attribute to a process called: “Natural Selection”

Darwin called this process by which populations change in response to their environment: Natural Selection

Darwin’s Finches

After his voyage, Darwin made the following inferences: 1. There is variation within populations 2. Some variations are favorable 3. Not all young produced in each generation can survive 4. Individuals that survive and reproduce are those with favorable variations 5. Favorable traits will increase in future generations. KNOW THESE!!! KNOW THESE!!!

Evolution happens because of natural selection Selection acts on individuals, populations evolve !!!

Adaptation Adaptations are inherited traits that increase a group’s chance of survival & reproduction This type of finch has a thick beak  adaptation for cracking open seeds

Variation Within a species, there is variation Variation = differences between members of a population Species = group that can breed & produce healthy offspring

Through Adaptation and Variation within a species Change creates advantages for some species & disadvantages for others We see this through fossil evidence: Fossils reveal changes in species over millions of years

What is the Evidence for Evolution?? 1. Fossils show change over time show change over time scientists can date fossils & use them to support the theory of evolution scientists can date fossils & use them to support the theory of evolution common ancestors reveal whether species are related common ancestors reveal whether species are related – Anatomy of living species also shows relatedness shows relatedness

How Anatomy supports Evolution 2. Homologous Structures Similar structures in different species but different functions Similar structures in different species but different functions because they share a common ancestor because they share a common ancestor Ex: human arm, dog front limb, horse leg, whale fin Ex: human arm, dog front limb, horse leg, whale fin “ look the same.” These “ look the same.” They have the same bones but different function.

3. Analogous structures Distantly related species have different structures that have the. Distantly related species have different structures that have the same function. Ex: wing of butterfly & bird Ex: wing of butterfly & bird “ work the same.” These “ work the same.” They have different bones but the same function. How Anatomy supports Evolution

4. Vestigial structures Structures reduced in size & often unused Structures reduced in size & often unused Remains of functional structures inherited from an ancestor Remains of functional structures inherited from an ancestor Ex: leg & hip bones in pythons & whales Ex: leg & hip bones in pythons & whales How Anatomy supports Evolution

How DNA Supports evolution 5. Molecular Evidence Also called biochemical evidence Also called biochemical evidence Compares biomolecules such as DNA or amino acid sequences between organisms Compares biomolecules such as DNA or amino acid sequences between organisms Related organisms have more of the same molecules in common Related organisms have more of the same molecules in common

So….. Where Do New Species Come From?

How do new species form? 1. Geographic Isolation When members of a population are separated When members of a population are separated Ex: polar, grizzly, & black bears Ex: polar, grizzly, & black bears

2. Reproductive Isolation When members of a population can’t breed even though they live nearby When members of a population can’t breed even though they live nearby Ex: different mating seasons or different mating calls Ex: different mating seasons or different mating calls

Different Types of Evolution 1. Divergent evolution 2. Convergent evolution 3. Coevolution 4. Adaptive radiation

Divergent Evolution (spread apart) -Isolated populations evolve independently Ex: polar & grizzly bears changed independently due to different habitats

Convergent Evolution (come together) -Unrelated species become more alike because they live in similar environments Ex: shark & dolphin

Coevolution (together) -Species that interact closely adapt to one another Ex: Flowers & Pollinators (Birds, Bees and Butterflies too)

Adaptive Radiation Evolution of many diverse species from one common ancestor Ex: famous Galapagos finches discovered by Darwin

Questions?