What biological principle is illustrated by the Heike crabs?
Selection by humans
Sagan says that if artificial selection can produce vast changes in a short period of time, then what must nature be able to do, given the age of the ear (4.5 billion years or so)? Don't just quote the video here. Explain what he means!
Nature must be able to produce and create.
What are the basic “steps” in natural selection as Sagan describes them? What questions does he raise for you?
Natural Selection happens when human’s changes have created other changes without humans directly deciding to do so.
Sagan describes the basic steps as there are more creatures then can survive. Less adapted have a less chance of surviving and producing off spring. Sudden changes in heredity can be pushed on to the off springs. Environmental changes can have an impact on what mutations will help survival. Thus, slow changes produce new species. Natural Selection was discovered by Charles Darwin and Alfred Russel Wallace.
Explain the Watchmaker Hypothesis as an argument against natural selection. How does Sagan address it?
“Our ancestors looked at the intricacy and the beauty of life and saw evidence for a great designer. The simplest organism is a far more complex machine than the finest pocket watch. And yet, pocket watches don’t spontaneously self-assemble or evolve in slow stages on their own from say, grandfather clocks”. (Sagan, C)
It’s impossible to just look at something and understand as a whole.
Sagan comments that all life on this planet shares a number of characteristics, including one three-letter answer to the question of what is the master molecule?
DNA
What IS the master molecule? Do you think it is significant that all life on the planet shares the use of this code? Why or why not?
DNA is made of nucleotides which have four chemical parts, “adenine, cytosine, guanine and thymine”. (microbenet) Each is different based of what organism. Should a mutation occur it is going against the genetic plan. Thus, some mutation can harm the next generation. Others can assist the genetic plan and assist in evolution. We all have very close DNA that breaks down proteins to support functions of our cells.
Explain the purpose of the “cosmic calendar analogy” as you understand it. Roughly how long have humans been on the calendar? 2.5 Mya
What does that make you think about the relative newness of our species?
The cosmic calendar analogy was created to explain how much time has passed since the Big Bang explosion which created the universe. Sagan calendar is based on one-year. January 1 is Big Band and the following January 1 is today. Based off this scale, “there are 438 years per second, 1.58 million years per hour, and 37.8 million years per day”(Kardas). Looking at the calendar and the existence of the universe our years of life are diminutive. Makes me feel that we are pretty small compared to what is out there.
What do we learn when Sagan visits the Royal Gardens at Kew about the relationship between plants and animals on earth? Which is more “important” – us or them; why?
Plants use carbohydrates to produce energy. We use the carbohydrates from plants to fuel us with energy. When carbohydrates and oxygen meet we use this to breath. We use energy and exhale carbon dioxide. Plants use the carbon dioxide to make carbohydrates. The cycle repeats. Carbon dioxide would still exist without animals/us. Thus, our need for plants is higher than the plants need for us.
What does Sagan say about the nature of genetic material and its function?
DNA and enzymes are part of “molecular machines with awesome powers”. Molecular ensure that nucleic acids reproduce.
What does Sagan say about the number of possible combinations of nucleic acids? How does this relate to selection?
The combination is “larger than the total number of atoms in the universe”. It just isn’t possible. Human kind holds many possibilities. Because the combination is so large, to know the amount of human possibilities is not feasible. What similarities does Sagan see between humans and trees? Why does he suggest we are so similar?
Proteins that control cell chemistry that carry hereditary information are identical in plants and animals.
Trees and humans use nucleic acids, proteins and translate nucleic acid information into protein information.
11. What is the purpose of the Miller-Urey experiment and what results were had from its implementation?
The experiment was based off creating molecules, “the stuff of life”. Mixing together the gases, waters and energy and using an ultraviolet light (posing at the sun) the vessel created brown organic molecules, “The building blocks of the proteins and nucleic acids”, making “identical copies of the nucleic acids.
Cosmic Calander. Retrieved from http://en.wikipedia.org/wiki/Cosmic_Calendar
Eisen.J (n.d.) Facts sheet: dna-rna-protein. Retrieved from http://microbe.net/simple-guides/fact-sheet-dna-rna-protein/
Carl Sagan's (1/30/2010) Calendar Analogy of Time since the Big Bang. Retrieved from http://peace.saumag.edu/faculty/kardas/Courses/HP/Lectures/sagan.html
