Everything’s Relative Don’t I Know You?!?

Are the people in these pics related? How can you tell?

What about these folks?

Are these people related too?

How about them?

Here too?

How are all these organisms related? They all have similar or identical (twins) DNA. The more similar the DNA is between two organisms, the more closely they are related! In order to compare DNA, we look at amino acid sequences because the order of your amino acids is determined by your DNA. Remember, DNA codes for proteins, and amino acids are the building blocks of these proteins. Have students fill in the answers as you type.

What is a common ancestor? All species of organisms have evolved from a common ancestor. A common ancestor is an organism that gave rise to new species of organisms. For example, the common ancestor of modern birds are dinosaurs. Homo sapiens (that’s us) have the same common ancestor as modern day apes.

What is evolution? The change in the DNA of a population over time. One organism itself cannot evolve, only a population can evolve. What are the general steps? 1. Simple, single-celled organisms appear. 2. Multicellular organisms begin to evolve. 3. The diversity of mulicellular organisms increases. 4. Meat eaters (carnivores & omnivores) were the last to evolve.

Endosymbiont Hypothesis…AGAIN!! If single-celled organisms (usually prokaryotes) were the first to evolve, where did multicellular (usually eukaryotes) organisms come from? Remember that one anaerobic prokaryote ate an aerobic prokaryote, but instead of digesting it, it became stabilized. These aerobic prokaryotes eventually evolved into chloroplasts and mitochondria. This is why chloroplasts and mitochondria have a DOUBLE membrane! (From going through the anaerobic bacteria’s cell membrane.) Evidence for the Endosymbiont Hypothesis: Mitochondria & chloroplasts contain DNA similar to bacterial DNA. Both mitochondria and chloroplasts reproduce through binary fission. Mitochondria, chloroplasts, & bacteria are similar in size and shape.

How does the dna change? Two Ways: Sexual Reproduction – mixes the DNA of two individual organisms in a new and unique way. Mutation – a spontaneous change in the DNA which can be passed from parent to offspring.

How does the new dna spread? If the new pattern of DNA is beneficial, then the organism will outlive its competitors. If it outlives its competitors, it can have more opportunity for reproduction. All of its offspring will then have this new beneficial trait. The trait will spread through the population. If it spreads through the population, it isn’t a mutation anymore, because almost all the organisms have it. It has now become an adaptation!

I don’t believe in evolution because it’s just a theory! Well, do you believe you are made of trillions of tiny cells? Do you believe that all things are held to Earth because of gravity? These are examples of scientific theories. A scientific theory doesn’t mean that it’s just some dude’s random idea. A scientific theory MUST be supported by data, and I mean LOTS of data!!!! It must be researched, defended, and all but proven in order to reach the status of “theory”. We’ll be looking at this data in just a moment! Link to Just a Theory video clip

But believing in evolution goes against my religion… Science as a whole has nothing to do with religion. People of all faiths all over the world practice science. Science can tell us HOW something happens. Religion can help determine WHY. For example, I don’t know the purpose of life. I don’t know WHY we’re here. My personal religious beliefs tell me that there is a greater purpose for us being here. But I do know HOW we got here. Science tells me that it happened through the process of evolution…AND we have the evidence to back it up!

Fossil Dating How do we know how old fossils are? Relative Dating – means that we don’t know exactly, but we can estimate using what we know. Law of Superpositioning – the deeper down a fossil is, the older it is. Which layers in the picture are oldest? …youngest? This can be tricky because sometimes the rock layers have become disturbed due to earthquakes, landslides, or other events. In these cases, the layers, and the fossils they contain, may not be in the order that they were originally deposited. Absolute Dating – means that we can figure out precisely how old a fossil is. Use radioactive dating of either carbon (C-14) or potassium (K-40). Radioactive atoms decay into other elements by losing neutrons. For example K-40 decays into Argon. Carbon can be used by measuring the ratio of C-12 to C-14, because C-12 remains the same after death, but C-14 decreases. We refer to this as the half-life. Half-life: the time it takes for one half of the sample to decay. The half-life of K-40 is 1.3 billion years. The half-life of C-14 is 5,600 years.