EvolutionChange Over Time

First part of student download

Controversial subject. But why?

• Belief structures (Religion).

• Evolution is difficult to conceptualize.

• Lack of scientific understanding.

• Misinformation

Religion and the Origin of life

• Religion is based on faith.

• Faith is a belief system

Evolution is not a religion!• It is a scientific theory that best explains the data

produced from hundreds of years of observation and research.

• Based on scientific observations and what we can prove scientifically.

• Supported by Biological, Chemical, Genetic, and Physics Research.

• You do not have to believe it but you should understand it

Evidence for evolution• Geologic• Structural• Genetic

Geologic evidence:

• Geologic timeline from fossils• Continental Drift• Plate tectonics

Continental Drift

Evidence for evolution:FossilsObservation: Fossils have been found and

dated.Inference: Comparing fossils to living

species today indicates living organisms have changed over time.

Trilobite (extinct marine invertebrate) found in Ohio—site of an ancient sea

Fossils can form in several ways.

1. Permineralization

Permineralized skeleton of a Velociraptor dinosaur

The minerals form a covering over the bones.

2. Natural cast – Minerals fill in the

spaces left from decomposition, recreating the original shape.

Cast of a crinoid, a marine animal

3. Trace fossils.

Leaf imprintsFootprints

Fossils of footprints from a Dimetrodon dinosaur

4. Amber-preserved fossils

– organisms are trapped in tree resin

Wasp

5. Preserved remains • an entire organism becomes encased in ice,

volcanic ash, or mud.

Ice preserved 5000 year old man found in the Italian Alps.

• Specific conditions are needed for fossilization.• Only a tiny percentage of living things became fossils.

• Nevada’s state fossil: the icthyosaur which is the ancestor of the dolphin

• We have the Icythyosaur State Park in central Nevada as Nevada was once underwater

Fossils: Links to the past…

Scientists have an incomplete picture of past life on Earth because:

• Not all bones become fossils.- Conditions- Predated by animals

• We have not found all fossils

Evidence for evolution• Geologic• Structural• Genetic

Fossils: Links to the past…

Scientists have an incomplete picture of past life on Earth because:

• Not all bones become fossils.- Conditions- Predated by animals

• We have not found all fossils

Dating the age of Fossils

1. Law of superposition – Estimates the age of fossil– It compares the placement

of fossils in layers of rock.

2. Radioactive isotope dating (Uranium used for really old aging Carbon 14 dating most common)

Law of Superposition

Radioactive dating

Dating the age of Fossils

1. Law of superposition – Estimates the age of fossil– It compares the placement

of fossils in layers of rock.

2. Radioactive isotope dating (Uranium used for really old aging Carbon 14 dating most common)

Law of Superposition

Radioactive dating

Development of the modern theory of how evolution happened

• History• The Beagle• Darwin’s Research

Early ideas on evolution:Lamarck• He thought salamanders lost their legs

because they didn’t use them. Legless salamanders (snakes) then passed on this trait to offspring.

Logic errors:• Not supported by DNA• No experimental evidence

Charles Darwin: “Father of Evolution”

• Traveled extensively• Familiar with breeding (genetics)• Published his ideas in Origin of

Species in 1859.

Published in1859:

Darwin’s Voyage on the HMS Beagle

• Where it went• His Observations

Darwin’s Voyage on HMS Beagle

Darwin’s observations gave him an idea. Then he did his homework!

Darwin’s observation:

1. Variation exists in all living thingsStructural variation (what they look like)Behavioral variation (how they act)Biochemical variation (how they function)

2. Species compete for resources: Food Water Mates Shelter

Darwin’s Inferences: Theory of Natural Selection

1. Due to variations, some organisms have characteristics which help them survive.

2. These organisms reproduce, passing on their genes.

3. Over time, more and more organisms will have this great trait, making them “different” from previous generations.

4. Natural selection explains how new organisms will appear over time. This is called speciation.

VocabularyAdaptationAn inherited variation that increases the chance of survival.

FitnessMeasure of the ability to survive and produce more offspring.

3 Ways Evolution Happens1. Artificial selection2. Genetic Drift3. Natural selection

1. Artificial SelectionThe process by which humans change a species by breeding it for certain traits.

neck feathers

crop

tail feathers

Pigeon breeding Bred for tail feathers

Bred for crop

Bred for neck

feathers

2. Genetic Drift

• “Chance” causes a small population.– Dramatic event– Small group leaves or is separated

• Result: less genetic variety

3. Natural Selection Its all about Variation!

• Mutations - Small changes / Lots of time• Genetic Recombination (crossing over,

Independent assortment & Segregation)

Fitness determines survival• Variation leads to differential

fitness.• Some organisms survive

better than others• Fitness determines which

individuals survive and reproduce.

• Must have a selective advantage or trait (gene) will not increase within a population.

Selected for:

• Helpful traits which help survival are selected for in a population and increase in frequency.

Selected against:

• Harmful traits or unsuccessful traits are selected against in a population and decrease in frequency.

Examples of Evolution Occurring

• Extinction• Pesticide Resistance• Antibiotic Resistance

Extinction

• All members of a population die out.

• Loss of genetic diversity.• Can be global or

regional

Pesticide resistance:• Have to come up with new and more toxic

chemicals to combat pests. • Weeds• Insects

Antibiotic resistance:• Need for new antibiotics• Evolutionary arms race*