Hey this is Mr. W. Welcome to Episode One of Thinking Biologically: Biology's Big Ideas.
This is the first episode of a weekly series that I'll be doing this year. My
goal is to help you succeed in your biology course and learn more than you ever thought
imaginable. Throughout this series I'll be emphasizing the College Board's four big
ideas. Why? Because they're a fantastic intellectual scaffold that you can use
to organize all of the information in this very information-rich subject. Here's what they are:
evolution, information storage and transmission, energy and matter flow,
and systems and system interactions. And they're all right here in this Apple.
Evolution is the process by which living things change over time.This Apple is a Gala or a Gala
depending on how you like to pronounce it. It's a cultivated variety of a wild undomesticated
apple that first evolved in Central Asia. If you could go back in time and went back just
a hundred years you wouldn't find a Gala Apple. This variety has only been cultivated for about
a hundred years. It's one of hundreds of Apple varieties each with different appearances and
tastes that humans have created through selective breeding. Evolution is a process that unfolds over
time you can use a diagram like this— it's called a phylogenetic tree— to represent the
evolutionary history of any organism, including apples. Apples have a common relatively recent
ancestor with crab apples. They're more distantly related to fruit like pears. Apples, crab apples,
and pears are part of an enormous group of species called the flowering plants
that first emerged over a hundred million years ago in the time of the dinosaurs. A
more ancient ancestor gave rise to plants with seeds but no flowers
about 350 million years ago. You can push further back to seedless plants, and eventually you reach
an ancestor that wasn't a plant at all. Before 450 million years ago there was no life on land.
There were no plants. At that point the apple's ancestor was some kind of aquatic photosynthetic
algae If you go wide enough you're looking at all of evolutionary history — essentially the tree of
life. Here's the group that apples belong to: the plant kingdom. Here's our group the animals. Note
that we and apples have an evolutionary ancestor in common. The apple is our evolutionary cousin,
as is every other living thing. Is there evidence for that astounding claim? Of course: it's
embedded in our genes, our selves, our metabolism. We'll get there later in this series. Evolution
produces adaptations: structures with functions that help organisms to survive and to reproduce.
The skin of this apple is an adaptation that evolved to attract animals by letting the apple
be seen against a sea of green leaves. That's a trait that co-evolved with color vision in fruit
loving primates like ourselves. The apple's skin also protects the apple's flesh from bacteria and
fungi. The flesh is an adaptation that evolved to be a reward for animals that would eat the
fruit and swallow the seeds. The seeds themselves have other adaptations including a protective seed
coat that allows the seeds to pass through an animal's gut without being broken down by the
acids in an animal's stomach. This allows the seeds to be deposited somewhere where they can
grow into new apple trees. Adaptations come about through a process called natural selection. In any
population there's variation in traits. Among the apple seeds there are going to be some that
have thicker coats and some that have thinner coats. Some of that variation is determined by
genes. Variants that are unsuccessful — which means that they're not very good at promoting
survival and reproduction — are going to wind up being removed from the population.
An apple seed that has a coat that's too thin is going to wind up being dissolved in the stomach
as it's being dissolved. The genes for that trait are also going to be dissolved and that means that
those genes won't wind up being represented in the next generation's gene pool. The opposite is going
happen to traits that are more adaptive (that help an organism to survive and reproduce). So over
time natural selection shapes adaptations. It's that simple. The second big idea in our course
is information storage and transmission. Again, think about this apple. You plant an apple seed,
you get a new plant. What the seed is transmitting is information about how to build a new tree.
That information is genetic information and it's stored in a molecule called DNA. Let's
think about DNA in the context of a cell. DNA is in the cell's nucleus and it sends
a message that goes to particles that are called the ribosomes. Those ribosomes are
unbelievable because what they can do is they can take information sent by DNA and translate
it into protein. Protein determines the characteristics of cells. And in fact,
through many complex mechanisms, proteins will wind up determining the characteristics of the
entire organism. And that information has been changing over evolutionary time. In
fact you can think of evolution as a change in the genetic information carried within a population's
gene pool. The third theme is energy and matter flow. This apple was built by cells using solar
energy. Photosynthesis is one of the great energy reactions of living things. What photosynthetic
cells can do is take free energy in sunlight (free energy is available energy that can be harvested
to do work) and they use that energy to combine carbon dioxide (a gas in the air) and water to
create carbohydrates. Those carbohydrates are full of chemical energy that plants can use to power
their own life processes. These carbohydrates also provide the matter—the carbon, hydrogen,
and oxygen atoms— that plants use to build themselves. Now that energy can also pass to
animals like you and me. What we do is we take chemical energy and combine it with oxygen,
releasing energy we need to sustain our life processes. We breathe out the exhaust carbon
dioxide and water vapor. The entire process is called cellular respiration and it's life's
other great energy related process. So we have energy flow from the sun into plants
and then into animals like you and me. Note that this is a one-way flow. The energy isn't lost,
but it starts out as useful free energy and by the time living things are done with it it's
useless heat. Energy flows and dissipates. In almost every ecosystem on Earth, life is
sustained by a constant flow of energy from the Sun. Matter works differently: it's recycled.
Carbon, for example, will move from carbon dioxide in the air into plants like apple trees. Plants,
in addition to doing photosynthesis, also do cellular respiration and that returns some carbon
dioxide into the air. The carbohydrates made by plants can then pass to animals. We perform
cellular respiration and that again returns CO2 to the air. When living things die they're
decomposed by bacteria and fungi. Decomposition returns carbon dioxide to the atmosphere,
so the same atoms have been cycling on planet Earth for billions of years. Idea number four
is that life is composed of complex interacting systems. A system is a group of connected things
that form a larger whole. You know that phrase "the whole is greater than the sum of its parts?"
That's what systems are all about. The systems that we'll look at most in this course are cells,
the building blocks of life. Earlier we looked at the Tree of Life. You can see here that
the tree has a common stem and then there are three major branches. Each branch is a Domain.
That's the biggest classification category and it's based on cell type. Simpler,
smaller cells are found in bacteria and archaea. Much more complex cells,
like the one in this Paramecium, are found in our Domain, the eukaryotes. Apple trees are
composed of eukaryotic cells that are like this. These cells interconnect to form tissues like the
photosynthetic tissue in this leaf. Interacting tissues form organs like the leaf itself. At every
level new properties emerge as the system grows more complex. Organisms, whether they're made of
one cell like this Paramecium or trillions of cells like you and me, are open systems. That
means that they have input and outputs. The inputs in terms of cellular respiration are things like
fuel food and oxygen. The outputs are things like carbon dioxide, water and other wastes. Systems
interact when I took a bite out of this Apple that was one organism consuming another organism.
That's an important kind of interaction. Living systems are also embedded within other systems.
An apple tree, for example, is part of a wider ecosystem composed of interacting populations
and the nonliving matter and energy that sustain them and all ecosystems are part of the biosphere,
the living system that includes all life on Earth. How are you going to learn this? I'm not referring
just to this video but to the entire course. Learning requires interaction and that's why I
put together an interactive biology curriculum and my website, sciencemusicvideos.com. So go
there now You're gonna find flashcard. You're going to find multiple-choice quizzes. You'll
find the interactive diagrams: ways that you can interact to really remember what you've learned.
Go there now there's a card above there's a link below. Complete the
activities and you will learn more than you ever thought possible and you'll
have fun doing it because it's not passive learning. It's active you'll have a great
sense of accomplishment. So go do it! It does require a subscription. It's a great bargain,
and you can also get your teacher to purchase a site license so that all the students in
your class can be learning together. Got a question? Please leave it in the comments
below. But right now we're going to sign off. I'll see you at sciencemusicvideos.com
and I'll see you here next week the next episode of Thinking Biologically. Thanks.