Cambridge Biology (4th Ed.) — Chapters 1 & 2 (Year 11 NZ) Study Materials Summary & Study Notes

🧬 Chapter 1 — Characteristics of Living Things & Cell Theory

This chapter introduces the characteristics of life and the foundational cell theory. Living organisms share common features: organisation, metabolism, homeostasis, growth, response to stimuli, reproduction, and adaptation. Understanding these characteristics helps distinguish living from non-living systems.

The cell theory states three key ideas: all living organisms are composed of cells, the cell is the basic unit of life, and all cells come from pre-existing cells. Cells can be unicellular (single-celled) or multicellular. Cell specialisation and organisation into tissues, organs and systems allow multicellular organisms to perform complex functions.

🔬 Chapter 2 — Cell Structure and Microscopy

This chapter focuses on cell types, organelles, and the tools used to study them. Cells are broadly classified into prokaryotes (no nucleus; e.g., bacteria) and eukaryotes (membrane-bound nucleus; e.g., plant and animal cells). Key organelles include the nucleus, mitochondria, chloroplasts (in plants), endoplasmic reticulum (rough and smooth), Golgi apparatus, lysosomes, ribosomes, and the cell membrane.

The plasma (cell) membrane is a phospholipid bilayer with embedded proteins and is described by the fluid mosaic model. It regulates exchange via diffusion, osmosis, and active transport. The surface area-to-volume (SA:V) ratio is critical: as cells grow larger, volume increases faster than surface area, affecting transport efficiency and often limiting cell size.

🔭 Microscopy: Principles and Practice

Microscopes are essential for observing cells. Light microscopes (compound) are used for living or stained specimens and provide magnification up to around 1000–1500×. Electron microscopes (TEM and SEM) use electrons for much higher resolution; TEM shows internal ultrastructure, SEM shows surface topology.

Important microscopy concepts:

• Magnification is given by the product of ocular and objective lens magnifications. Image size = object size × magnification. In formula form: $\text{magnification} = \frac{\text{size of image}}{\text{size of object}}$.
• Resolution is the ability to distinguish two close points as separate — electron microscopes have much higher resolution than light microscopes.
• Staining (e.g., methylene blue, iodine) increases contrast by binding to specific cell components.
• Proper slide preparation and focus (coarse then fine) are essential; use appropriate controls and labels.

🧪 Measuring and Calculations

Students must practise calculating magnification and real object sizes using scale bars and formulae. For a specimen image: $\text{actual size} = \frac{\text{image size}}{\text{total magnification}}$. Always keep track of units (µm, mm) and convert appropriately.

Estimating cell counts, comparing organelle sizes, and calculating SA:V ratios ($SA:V = \frac{\text{surface area}}{\text{volume}}$) help predict metabolic rates and diffusion limits.

🧾 Practical Skills and Observations

Practical skills emphasised in these chapters include mounting wet mounts, preparing stained slides, focusing a light microscope, drawing labelled diagrams with scale bars, and making careful observations. Record clear observations and avoid over-interpretation. Include magnification and use appropriate biological vocabulary.

✅ Key Terms (quick reminder)

Cell theory, prokaryote, eukaryote, nucleus, mitochondrion, chloroplast, ribosome, endoplasmic reticulum, Golgi apparatus, lysosome, plasma membrane, diffusion, osmosis, active transport, magnification, resolution, staining, surface area-to-volume ratio.