GCSE/iGCSE Biology - Week 2
- Sallyann Clark
- Apr 30
- 4 min read
WEEK 2: WHAT IS LIFE?
Big Question of the Week
"What exactly do biologists DO all day, and what makes something alive in the first place?"
Write this question in your learning journal as a title before we begin. Do not look anything up. Just think. What do you already believe? What makes a rock different from a mouse? What makes a virus different from a bacterium? Hold those thoughts. We will come back to them.
Before you press play on Episode 3, make a prediction: Write down three things you think biologists actually do at work every day. Be specific. Do they mostly work in labs? In jungles? At computers? We will check your predictions after.
Video Session 1
This episode with a question that sounds simple but is actually enormous: what is biology for? The answer he builds toward is that biology is the study of life in all its forms, and that biologists pursue that study in wildly different ways.
Key ideas to watch for:
Fieldwork vs. Laboratory Work: Biology does not happen only in white-coated labs. Some biologists spend months in rainforests counting beetle species. Others peer through microscopes at cell membranes. Others build mathematical models of population growth without ever leaving their desks. The discipline is vast.
Biological Models: One of the most important tools biologists use is the model — a simplified representation of a biological system. Models are not perfect copies of reality. They are useful simplifications. A model of how a virus spreads through a population will not capture every detail of human behaviour, but it can still help us understand and predict outbreaks.
The Importance of Observation: Before any experiment, before any hypothesis, there is observation. Hank reminds us that careful, patient observation, the kind Darwin practised for decades, is the foundation of all biology.
Reading Assignment 1
Khan Academy: Meet Larry Joe Highschool Biology Unit 11.
Here is a go place to stop if you need to.
Video Session 2
This episode is dense and rewarding. Hank takes us from the smallest units of life all the way up to the entire biosphere. This is called the hierarchy of biological organisation and it is a concept you will return to again and again throughout this course and in your iGCSE exam.
The Levels of Organisation — learn these in order:
Level | Example |
Atom | Carbon atom |
Molecule | Glucose molecule |
Organelle | Mitochondrion |
Cell | Muscle cell |
Tissue | Muscle tissue |
Organ | Heart |
Organ System | Circulatory system |
Organism | Human being |
Population | All humans in London |
Community | Humans, foxes, pigeons, trees in London |
Ecosystem | London including its soil, water, and air |
Biosphere | All life on Earth |
Using a design app like Cana or pens and paper create a poster showing the twelve levels of organisation giving an example for each layer. Make it colourful.
Two concepts we were introduced to in the video were homeostasis and biochemical cycles.
Homeostasis - the idea that living things maintain stable internal conditions even when the external environment changes. Your body temperature stays close to 37°C whether you are in a snowstorm or a desert. This is homeostasis. It requires constant monitoring and adjustment. We will return to this concept in much greater detail when we cover the nervous and endocrine systems in Week 21.
Biogeochemical Cycles Carbon, nitrogen, water, and other essential elements move through living and non-living systems in continuous cycles. These are called biogeochemical cycles. Episode 4 introduces them briefly. We will explore them in depth during our Ecology unit in Weeks 23 and 24.
Reading Assignment 2
The Biological Contract: The Seven Demands of Existence
🧠 Misconception Corner
"Biologists mostly work in laboratories."
This is one of the most common misconceptions students bring to biology. In reality, the discipline spans laboratory bench science, field ecology, computational biology, marine research, medical research, conservation work, and science communication. Some of the most important biological discoveries in history, including Darwin's theory of evolution, emerged from years of fieldwork and observation, not laboratory experiments.
"Homeostasis means your body never changes."
Not quite. Homeostasis means your body regulates internal conditions within a narrow range. Your heart rate, blood pressure, blood glucose, and body temperature all fluctuate constantly. Homeostasis is the process of bringing them back to a set point, it is dynamic, not static.
Here is a good place to take a break.
Video Session 3
Watch TedEd - The Mysterious Origins of Life on Earth
Reading Assignment 3
Discussion question for your journal: Miller and Urey produced amino acids but not living cells. Why does this matter? What is still unexplained about the origin of life?
Scientist Portrait
Stanley Miller (1930–2007)
Add Stanley Miller to your Scientist journal. Draw his portrait or print one. Beneath it, write: "He built early Earth in a flask, and life's ingredients appeared."
✏️ 10-Question Practice Set — Week 2
Questions:
Name the two broad categories of work that biologists do, and give one example of each.
What is a biological model? Why are models useful even when they are not perfectly accurate?
List the twelve levels of biological organisation in order from smallest to largest.
What is homeostasis? Give one example from the human body.
Define the term biogeochemical cycle and name two elements that move through such cycles.
What are the seven characteristics of life? List them.
Which characteristic of life distinguishes a virus from a bacterium? (Hint: think about reproduction and cells.)
What did Miller and Urey produce in their 1953 experiment, and why was it significant?
Why is the generation effect a useful study strategy? What does it mean to reconstruct information from memory? (You may need to look this up.
Choose one level of biological organisation and explain how it relates to the level immediately above and immediately below it.
Looking Ahead — Week 3 Preview
Next week we go deeper than cells, deeper than molecules — all the way down to atoms. Week 3 is The Chemistry of Life, and it will ask you to think about carbon, water, and the four families of biological molecules that make up every living thing. If chemistry feels daunting, do not worry. We will build it slowly, with CrashCourse as our guide.
Prepare by writing this question in your journal: "If you had to build a living thing from scratch using only chemistry, where would you start?"