The Science
of Biology
Look inside plant and animal cells, follow photosynthesis and respiration, see how the body’s systems work together, learn how DNA and genes pass on traits and how evolution happens, and map the food webs of Alberta’s ecosystems.
- 00First Principlesp.2
- 01Cellsp.4
- 02Photosynthesis & respirationp.5
- 03Body systemsp.6
- 04Genes & evolutionp.7
- 05Ecosystemsp.8
- ✦Self-check · Make it · 5 Questions · Side Questp.9
You'll need: 2 small pots of the same plant (or bean seeds in cups), soil, water, a dark cupboard, a ruler and a notebook.
Principles
A first principle is a basic truth you can build on. The science of biology rests on four: all living things are made of cells, life runs on energy from the Sun, DNA carries the instructions and passes them on and living things depend on each other.
What do I already know?
What is necessary?
Everything in this module is built from four bricks. Rate yourself on each one, then check the example to see if your rating holds up.
What is the objective?
By the end, you’ll be able to compare plant and animal cells, explain photosynthesis and respiration, describe how body systems work together, explain genes, inheritance and natural selection, and build a food web for an Alberta ecosystem.
- 01Name 4 parts of a cell.
- 02Write the photosynthesis equation.
- 03Link 2 body systems.
- 04Explain dominant and recessive.
- 05Explain natural selection.
- 06Build a food web.
The list on the left is ours. Now make it yours. What do you want out of this?
How much do you know about the science of biology right now? Shade the boxes in pencil. You'll come back at the end (p.9) and shade it again in pen.
Why start this way? When you know what you already have (1), what you need (2) and where you're going (3), you learn faster and you notice the gaps. Every module on the Biology Path starts with these same three questions.
Cells
All living things are made of cells.
The units of life
All living things are made of one or more cells, and new cells come only from existing cells. Scientists estimate the human body has about 30 trillion cells.
- Nucleus: holds the DNA.
- Cell membrane: controls what goes in and out.
- Mitochondria: release energy from food.
- Cytoplasm: the jelly where much of the work happens.
What’s different
- Plant cells have a stiff cell wall and usually a large vacuole.
- Plant cells in leaves have chloroplasts for photosynthesis.
- Bacteria are prokaryotes: tiny cells with no nucleus.
Your cells and a plant’s cells both have mitochondria.
The first “cells”
In 1665, Robert Hooke looked at thin slices of cork under an early microscope and saw tiny boxes. He called them “cells” because they reminded him of small rooms. He was looking at the walls of dead plant cells.
- Why do you think cells are so small?
- What do plant cells have that yours don’t, and why?
Model a cell
Build a model plant cell from household things (a sandwich bag for the membrane, a box for the wall, a coin for the nucleus). Label each part and say what it does.Which cell part is found in plant cells but not animal cells?
Photosynthesis & respiration
Plants make food from light; all life releases energy from food.
Making food from light
In chloroplasts, green chlorophyll captures light energy. Plants use it to turn carbon dioxide and water into sugar, giving off oxygen:
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Releasing energy
Nearly all living things, plants included, break sugar down in their mitochondria to release energy:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
It is the reverse of photosynthesis.
Out of thin air
Most of a tree’s mass comes from carbon dioxide taken from the air, not from the soil. Soil gives water and small amounts of minerals. Leaves turn the carbon into sugar, then into wood.
- Why would life on Earth stop without photosynthesis?
- How are photosynthesis and breathing connected?
Leaf in water
Put a fresh leaf in a clear glass of water in bright sunlight for an hour. Look for tiny bubbles on the leaf. What gas might they be? Compare with a leaf in the shade.Which gas do plants take in for photosynthesis?
Body systems
Organ systems work together to keep you alive.
Cells to systems
Cells → tissues (groups of similar cells) → organs (like the heart) → organ systems → the organism.
| System | Main job |
|---|---|
| Digestive | Breaks down food |
| Circulatory | Carries blood, oxygen, food |
| Respiratory | Takes in oxygen |
| Nervous | Sends signals |
| Skeletal & muscular | Support and movement |
| Immune | Fights germs |
Systems working together
- When you run, muscles need more oxygen.
- The respiratory system breathes faster.
- The circulatory system pumps faster to carry oxygen.
- The nervous system controls both.
An adult skeleton usually has 206 bones.
Mouth to intestine
Teeth and saliva start breaking food down. The stomach adds acid and churns it. The small intestine absorbs nutrients into the blood through millions of tiny folds, and the large intestine absorbs water.
- Which body system do you think works hardest?
- How do two body systems work together when you run?
Body map
Trace an outline of your body on large paper (or draw one). Add and label the heart, lungs, stomach, intestines and brain. Draw arrows showing how oxygen gets from the air to a leg muscle.Which two systems work together to deliver oxygen?
Genes & evolution
DNA carries traits, and populations change over time.
The instructions
DNA is a long molecule shaped like a twisted ladder. A gene is a section of DNA that holds instructions for one part of how the body is built or works. Humans have about 20,000 genes.
Most human cells have 46 chromosomes (23 pairs): one of each pair from each parent.
How evolution works
- Individuals in a population vary.
- Some variations are passed on.
- Those better suited to the environment survive and reproduce more.
- Over many generations, the population changes.
Charles Darwin and Alfred Russel Wallace described this idea in the 1850s.
Antibiotic resistance
When antibiotics are used, a few bacteria may survive because of small genetic differences. They multiply, so the drug works less well next time. That’s why people should take antibiotics only as a doctor directs.
- Why do brothers and sisters look alike but not identical?
- How could a useful trait spread through a population?
Family traits
Make a table of 3 easy-to-see traits (like attached or free earlobes) in people who agree to take part. Remember most traits depend on many genes, so don’t draw conclusions about family relationships.How many chromosomes are in most human cells?
Ecosystems
Living things depend on each other and on their environment.
Who eats whom
- Producers make food from sunlight (aspen, grasses).
- Consumers eat other living things (hares, moose, lynx).
- Decomposers break down dead things (fungi, bacteria, worms).
A food web shows all the links, not just one chain.
The boreal forest
In the boreal forest, snowshoe hares eat shrubs and bark, and Canada lynx eat mostly hares. Their numbers rise and fall in a cycle of roughly 10 years: more hares, then more lynx, then fewer hares, then fewer lynx.
Beavers
Beavers build dams that flood land and make ponds. The ponds give homes to fish, frogs, ducks and moose, store water in dry years and change how streams flow. One species can reshape a whole ecosystem.
- What would happen if one animal disappeared from a food web?
- Which Alberta ecosystem would you most like to visit?
Food web
Pick an Alberta ecosystem (a slough, a grassland or a mountain forest). Draw a food web with at least 8 living things, including a decomposer. What would happen if one disappeared?What role do mushrooms play in a food web?
Quick self-check
Six questions, covering every stop. Show your thinking. Answers are upside down at the bottom; no peeking till you're done.
1 · What does the nucleus do?
2 · Write the word equation for photosynthesis.
3 · Which systems deliver oxygen to muscles?
4 · What is a gene?
5 · What are the steps of natural selection?
6 · Name a producer, a consumer and a decomposer.
Re-shade your knowledge meter
How much do you know about the science of biology now? Flip back to p.3 and shade the meter again in pen (or shade this one). Did any of the four bricks on p.2 move from "Not yet" to "Got it"?
Plants and light
Does a plant need light to grow well?
1 · Plan
Use two pots of the same plant, or grow bean seeds in two cups. Give both the same water and soil. Put one in a sunny window and one in a dark cupboard. Measure and describe both every two days for two weeks.
- Same plant, soil and water
- Only light changes
- Prediction first
- Dated measurements
2 · Results
| Day | Light (cm) | Dark (cm) |
|---|---|---|
| 0 | ||
| 2 | ||
| 4 | ||
| 6 | ||
| 8 |
3 · Must-haves
- Height and colour noted
- Graph of both plants
- Photosynthesis explained
- One way to improve
4 · What I found
Use a common, non-poisonous houseplant or bean seeds. Don’t eat the seeds or plants, keep soil away from your mouth, and wash your hands after handling soil.
5 Questions
I Still Have
This module didn't answer everything. Good. Write 5 new questions it didn't answer, one of each type below. There are no wrong questions, only ones nobody's asked yet.
★ Star the one question you'd most like answered. You'll need it on the next page.
1What I'll find out
Break your big question into 2 or 3 smaller ones you could actually answer.
2Where I'll look
3How I'll share it
Who I'll share it with:
Done by: