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IB Biology "Themes Homework," Ch. 1 Overview and 1.1 - KEY
Theme: New Properties Emerge at Each Level in the Biological Hierarchy (Molecules to
Biosphere, see Fig. 1.4)
At each level, the whole is more than the sum of its parts!
E.g. A community ≠ a handful of populations
Because of emergent properties, a reductionist approach cannot give us all answers. Must
combine with a systems, holistic, dynamic approach that studies the interactions of the system's
parts.
E.g. How do we kill cancer while minimizing side effects?
Theme: Organisms Interact with Other Organisms and the Physical Environment
Humans causing climate change is a textbook example of this theme. And a corollary is that
materials are recycled earth-wide.
E.g. A butterfly is a food source for many animals, and keeps plants in check, and when it dies its
body is decomposed and becomes part of the soil to be converted into minerals for plants again.
Theme: Life Requires Energy Transfer and Transformation
Organisms require energy to do the work of living. Energy enters as sunlight in photosynthesis,
is converted to chemical energy, is passed from producers to consumers to decomposers, and
leaves the ecosystem as heat when, for instance, chemical energy (potential) is converted to
kinetic energy (running). Energy flow is one-way.
Example: Sunlight falls on carrot plant, carrot plant makes sugar, carrot is filled with sugar, I eat
sugar, I convert sugar's energy to ATP, I use ATP in my muscles as I type, giving off heat.
Theme: S and F are Correlated at All Levels of Biological Organization
At all levels, how a biological structure looks lets us make inferences about what it is used for,
and vice-versa.
E.g.: Because they run on the surface of water when trying to escape, I would expect there to be
something special about the structure of basilisk lizards' feet, such as long toes, waterproof
material, etc.
Theme: The Cell is an Organism's Basic Unit of S and F
When we look at figure 1.4, the not alive/alive line is drawn below the cell. Cells – whether
prokaryotic or eukaryotic – can do all activities required for living. And we can trace what
tissues, organs, or organisms do to what their cells do.
E.g.: A beta cell in a pancreas secretes insulin, the protein that lowers blood sugar after eating. In
an untreated diabetic, lack of beta cells results in a lack of insulin and thus blood sugar level that
is too high.
Theme: The Continuity of Life is Based on Heritable Information in the Form of DNA
E.g.: A sea turtle is a sea turtle's egg's way of making another sea turtle." Living things make
more of themselves, either directly through cell division or by using cell division to create
"founder" cells that merge into a new being. What is physically passed along – copied, then
divided - are chromosomes. Chromosomes contain DNA. DNA is the blueprint for making
proteins. Living things are built of and operated by their proteins. One protein "recipe" is called
a gene. Some genes' jobs are to make proteins for traits, but to make proteins that control the
functioning of other genes. All of the DNA of an organism constitutes its genome. Studying
entire genomes, genomics, is how genes are studied today.
Theme: Feedback Mechanisms Regulate Biological Systems
Living systems are so complex – at the level of the cell, or at the level of the ecosystem –
mechanisms exist to regulate the rates of key activities. The output of a process regulates that
very process. This is called feedback regulation. In negative feedback, the output sends the
process in the opposite direction; in positive feedback, the output amplifies the process in the
same direction.
E.g.: Drug addiction. When an addict repeatedly takes drugs that lead to dopamine (DA) release,
receptors for DA are down-regulated (negative feedback). The sad result is that the addict,
without the normal number of DA receptors, eventually resorts to taking the drug just to feel
normal again (rather than to feel a "high").
Theme: life evolves!
Evolution is biology's core theme. It explains both life's diversity and its unity – all the features
that living things have in common.
E.g. Descent from a common ancestor allows us to explain, for example, why both gorillas and
humans have opposable digits.
Concept Check 1.1 Questions
1. Putting Fig. 1.4 into words:
 The biosphere is made of overlapping ecosystems
 Ecosystems are made of interacting communities
 Communities are made of populations inhabiting a specific area
 Populations consist of organisms of the same species
 Organisms contain organs and organ systems that work together
 Organs are made of tissues that have specific jobs
 Tissues are made of cells of the same kind, working together
 Cells contain organelles that are interdependent
 Organelles are structures made of molecules
2.
a) the sharp spines of a porcupine could exemplify
 S/F
 evolution
 organisms interacting with other organisms
b) the cloning of a plant from a single cell could exemplify
DNA's role
 cell is basic unit of life
 requirement for energy
 emergent properties
c) a hummingbird using sugar to power its flight could exemplify
 requirement for energy
 organisms interacting with other
organisms
 evolution

S/F
 emergent properties
 feedback mechanisms
3. Give an example not mentioned in the book for each theme – see blue type