THEORY OF EVOLUTION By Natural Selection

What is the Theory of Evolution? Evolution is change in a species over time. You personally cannot evolve. It doesn’t happen overnight! It takes hundreds of generations.

What is a scientific Theory? A theory is a well-tested explanation of a variety of observations and scientific experiments There must be MANY similar observations and results before it can be considered to be a theory! A theory is NOT a guess.

Jean Baptiste Lamarck ( ) French naturalist Was the first scientist to develop an explanation for evolution

Jean Baptiste Lamarck ( ) Lamarck believed that traits you acquire, or develop, during you life time could be passed on to your offspring (acquired characteristics) Example: Giraffes stretched their necks to make them longer, then passed that trait on to their offspring.

Acquired Characteristics If two body builders have a baby, will that baby be born with more “buff” muscles than other babies? Lamarck was right that animals change over time, but he was incorrect about the mechanism that caused this change.

Charles Darwin ( ) British Naturalist In 1831, he sailed around the world on the HMS Beagle Made observations and recorded information about the different species he saw

Voyage of the HMS Beagle

Galapagos Islands Darwin observed that the finches (small birds) on the Galapagos Islands all had differently shaped beaks Each beak was perfectly shaped for their food source

Galapagos Islands The finches had all come from ancestor birds who flew to the islands millions of years ago. Showed adaptive radiation – many new bird species evolved from one group because of all the different habitats on the different island.

Darwin’s Major Conclusions 1. Variation exists among individuals in a species (sexual reproduction + mutations) 2. Individuals must compete with each other for available resources. (“struggle” to survive) 3. After competition, some individuals will survive and some will die. 4. “Fitness”: Individuals with advantageous variations are more likely to survive and reproduce!

14 offspring 2 offspring Octomom Mom in Family B Who is more “fit”?

Octomom is more “fit” because she has produced more offspring, and more successfully passed on her genes to the next generation!

Adaptations Favorable traits are also known as adaptations Adaptations are ANY trait that helps an organism survive in its environment

Adaptations Camouflage: when an organism blends in to its environment

Adaptations Mimicry: when an organism looks like another organism to avoid being eaten

Natural Selection Darwin proposed the mechanism of evolution, called natural selection Said that all living things have descended with modifications from a common ancestor Some individuals have traits that will help them survive better than others in their habitat

Natural Selection

Organisms with these better traits are more likely to survive and pass those traits on to their offspring (also called survival of the fittest) Over time, the organisms with the “bad” traits die out, and a new species may be formed!

Evolution by Natural Selection

Natural Selection – Bacteria Imagine that there are 10 bacteria growing on your hand.

Natural Selection – Bacteria You use hand sanitizer to clean your hand every day.

Natural Selection – Bacteria After a week, there are still 3 bacteria on your hands that have survived!

Natural Selection – Bacteria These bacteria are special – something about their DNA has made them different and strong enough to survive

Natural Selection – Bacteria The 3 “super” bacteria are resistant to the hand sanitizer and asexually reproduce.

Natural Selection – Bacteria After a week, your hands will be covered with TONS of bacteria that are all resistant to the hand sanitizer!

Old SOL Question!

Another old SOL Question! They love evolution questions

Types of Natural Selection 1. Stabilizing selection – when no extreme phenotype or characteristic is favored – the “average” phenotype is seen the most. 2. Directional selection – the environment favors one extreme phenotype

Types of Natural Selection 3. Disruptive selection – the environment favors two extreme phenotypes.

Evidence for Evolution Evidence for evolution includes: 1. The Fossil Record 2. Anatomy 3. Embryology 4. Biochemistry/DNA

1) Fossil Record Shows how organisms have changed and become more complex over time Scientists study phylogeny, evolutionary history of species, from the Fossil Record

Relative vs. Absolute Dating Relative Dating: uses rock strata (layers) to compare age of organisms. Absolute Dating: uses radioactive isotopes to give us an estimate of numerical age. What can we tell from this, the relative age or absolute age?

Fossil Record

Practice SOL Question!

2) Anatomy – shape of structures Homologous Structures: body parts of different organisms that have the same internal structure Example: human arm, cat leg, whale fin, and bat wing have the same number and arrangement of their bones “Forelimbs”

Anatomy Homologous Structures show evidence of organisms having a common ancestor. We call this divergent evolution, when species “split” from each other who have a common ancestor.

Anatomy Analogous Structures: body parts of different organisms that have the same function (job), but are made of different structures Example: bird’s wing and insect’s wing

Anatomy Analogous structures show how different organisms have adapted to the SAME “selection pressure” (flying to avoid predators)– we call this convergent evolution.

Anatomy Vestigial Structures: parts with no obvious use (but they used to have a function) Examples: Appendix in humans, hip bones in whales

Evolutionary history of whales

3) Embryology Embryos (very early stage of development) of different, but related, organisms look similar to each other

4) Biochemistry/DNA All organisms use DNA to carry genetic information The more similar the DNA or protein sequences are, the more closely related the organisms are.

SOL Practice Question!

We’re gonna get you to rock that SOL!

Speciation – appearance of new species Gradualism – new species form constantly and slowly throughout time. Punctuated equilibrium – burst of speciation followed by long times unchanged.

Punctuated Equilibrium Idea was put forth by Stephen Jay Gould. Worked at Harvard, NYU, American Museum of Natural History

Isolation Mechanisms A species is a group that can mate + produce offspring New species form over long periods of time when populations can no longer breed with one another (they are “isolated” from each other). Geographic isolation – a physical barrier that prevents populations from breeding.

Isolation Mechanisms Behavioral Isolation – a behavior prevents two populations from breeding/mating with each other Example – birds with different mating calls

SOL Practice Question

Difficult because of too many words

Cladograms A cladogram is a branching diagram that shows the evolutionary relationships among a group of organisms.

Reading a Cladogram When a characteristic is listed at a tick mark: Organisms BEFORE that tick mark do not have the trait. Organisms AFTER the tick mark do have the trait.

Sample Cladogram What trait or characteristic do lizards have that salamanders do not have?

Cladogram What are the differences between primates/rodents/rabbits and crocodiles/birds?