Unit 1 Skeleton

PHENOMENON | Zach Doubek, an otherwise healthy, athletic 11-year-old got a life-threatening MRSA infection, from which he was lucky to recover; antibiotic-resistant bacterial infections are becoming more common and harder to treat.

SOCIETAL ISSUE | Medical professionals are concerned about the increased prevalence of potentially fatal antibiotic-resistant infections.

QUESTION | How can bacterial infections make us so sick, and why are they getting harder to treat?

BIG IDEA | Widespread use (and misuse) of antibiotics causes the development of antibiotic-resistant populations of bacteria that can cause potentially fatal infections.

CHAPTER 1

Question: How can bacteria cause infections?

BIG IDEA | Bacteria interact with their environment to survive
and reproduce, and these activities can harm human cells.

Lesson 1: Anchor
How can bacteria make us
so sick?

Sometimes, bacterial infections
make us very sick with potentially
fatal infections.

Lesson 2: Investigate
What are bacteria and where
are they?

Bacteria are all around us, they
differ in important ways from
viruses, they can be transferred
from one environment to
another, and they may grow
more in one environment than
they will in another.

Lesson 3: Investigate
What do bacteria need to live
and grow?

Bacterial growth on agar plates is the
result of individual bacteria reproduc-
ing by splitting into two, leading to
exponential population growth until
this growth is limited by resources
such as food and space.

Lesson 4: Investigate
Why do some bacteria cause
us problems?

Some (but not all) bacteria can cause
us problems when they enter our
bodies (or a new place in our bodies)
because in the process of getting
what they need to live and grow,
they may damage our cells and
cause us symptoms of infection.

Lesson 5: Synthesize
How can bacteria cause
infections?

Bacteria can cause infections because
as single-celled organisms that need
resources to live and grow, bacterial
populations may grow to a high level
when introduced to our bodies, and the
more of them there are, the more they
may damage our cells and make us sick.

CHAPTER 2

Question: How does the body respond to infections?

BIG IDEA | In response to infection, the human body has
specialized cells that can reduce the bacterial population, and
homeostatic feedback mechanisms ensure the body can
return to its optimal range.

Lesson 6: Gap Analysis
What is the body doing
when we get an infection?

When we have a bacterial
infection, our body may respond
in a variety of ways.

Lesson 7: Investigate
How do we know when
we’re sick?

The body has healthy ranges
that it maintains despite
environmental changes through
homeostasis, and when our
body goes outside those ranges
it often indicates illness.

Lesson 8: Investigate
Why are all these changes
happening in the body?

The body increases body temperature
as well as levels of specialized immune
cells and signal molecules because it
can use these to actively fight the
bacteria, even though the body’s
response contributes to our symptoms.

Lesson 9: Investigate
How can the body
control its response?

The body has homeostatic
feedback mechanisms that
can amplify or inhibit the
immune response to ensure
it activates only when
helpful and stops when it
would be harmful for it to
continue.

Lesson 10: Synthesize
How does the body
respond to infections?

The body responds to a
bacterial infection by
ramping up an immune
response when it detects
bacteria and the damage
they cause; if the bacterial
population is within the
range the body can
effectively respond to, it
will kill the bacteria and
then turn off the immune
response—if not, the
infection may become
more serious or even fatal.

CHAPTER 3

Question: What explains the increasing incidence of
antibiotic-resistant infections?

BIG IDEA | Natural selection occurs when inherited variation provides some individuals
a survival and reproductive advantage over other individuals in a specific environment,
leading to a shift in the most prevalent traits in a population. When we use antibiotics,
antibiotic-resistant traits can become more prevalent in bacterial populations.

Lesson 11: Gap Analysis
Why aren’t antibiotics
working as well as they
used to?

Antibiotics are not as
effective against some
bacterial infections as they
used to be.

Lesson 12: Investigate
How do antibiotics work?

Antibiotics reduce the
bacterial population
probabilistically because
they change the environ-
ment by targeting
structures that bacteria
have but our cells don’t.

Lesson 13: Investigate
Why do antibiotics sometimes not work?

Bacterial populations have variation because
some individuals have different traits, some
of which are differences in structures that are
advantageous because they make an
antibiotic ineffective against them.

Lesson 14: Investigate
How do antibiotic-resistant
bacteria become more common
over time?

In an environment that exposes
them to antibiotics, individuals
with antibiotic-resistant trait(s)
will become a larger portion of
the overall bacterial population
over multiple generations.

Lesson 15: Synthesize
What explains the
increasing incidence of
antibiotic-resistant
infections?

The incidence of
antibiotic-resistant
infections is increasing
because natural
selection leads to
increased antibiotic
resistance with
increased use of
antibiotics; we must
use antibiotics sparingly
and responsibly.

Lesson 16: Culminating
Task: How can we work
together with medical
professionals to be
better stewards of
antibiotics?

To prevent continued
selection for antibiotic-
resistant strains, we
need to work in
partnership with
medical professionals
to become stewards of
antibiotics.