Biology’s 4 Big Ideas Thinking Biologically, # 1

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.

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 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,

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   and I'll see you here next week the next 
episode of Thinking Biologically. Thanks..

You May Also Like