DoAssignment study guide

B2.4 · Investigate biodiversity, water, soil, and succession in sustainability

Learn to investigate biodiversity, water, soil, and succession in sustainability through clear examples and targeted practice.

Ontario Grade 9 Science

Biology: Sustainable Ecosystems and Climate Change

Investigating how living things and their surroundings support sustainability

A grassy schoolyard, a garden, and a patch of woodland may all support life, but they can differ in the kinds of organisms present, the water available, and the condition of the soil. These parts of an environment are connected. A change to one may affect others. Sustainability means considering whether people can meet needs while keeping environmental systems able to support life over time. In this lesson, you will investigate biodiversity, water, soil, and succession as parts of that question. An investigation is a planned way to gather and compare evidence. It does not by itself decide what a community ought to do.

What you will learn

Describe biodiversity and explain why it matters when considering sustainability.
Plan a safe, fair investigation of a local place using observations and simple records.
Describe how water and soil support living things and how changes in a place can lead to succession.
Separate observations and evidence from model limits and personal or community judgments.

1. Begin with a place and a question

Start with something you can observe. Perhaps two garden beds look different: one has many kinds of plants, while the other has mostly one kind. That observation raises a science question: What differences in the plants, water, or soil might help explain what is growing in each bed?

Biodiversity is the variety of living things in a place. It can include different kinds of plants, animals, fungi, and other organisms. A simple comparison can count the kinds of plants seen in two equal-sized areas. This is one measure of biodiversity, not a complete account of every living thing. Some organisms are small, hidden, or present only at another time of year.

Water is needed by living things and can affect which organisms can live in a place. Soil is the loose material on the ground in which many plants grow. Soil can hold water and provide a place for roots. It can also contain air, small pieces of rock, and decayed material from living things. These are useful starting ideas, not a claim that every soil or habitat is the same.

A fair comparison changes as little as possible besides the factor being investigated. For example, compare areas that are the same size and observe them in similar weather and at a similar time. Record what you actually see. Do not call one area healthier just because it looks more attractive to you; that is a judgment, not a direct observation.

Biodiversity means variety of living things in a place.
A question should name what will be observed or compared.
Observations describe evidence; judgments express values or preferences.

2. Gather evidence about water and soil

Before investigating, decide what evidence could help answer the question. A student could map where plants are growing, list visible plant kinds, and note whether the ground looks wet, dry, bare, or covered by plants. A map or checklist makes observations easier to compare. These records are evidence because they come from planned observations.

Keep the investigation safe and respectful. Use a school-approved outdoor area, follow teacher directions, avoid disturbing organisms, and do not taste soil or water. Do not dig or handle unknown material without permission. If an investigation needs a tool or a soil sample, use it only as directed by the teacher.

Water and soil can be described in simple ways. For example, note whether the surface appears wet or dry, or whether soil is covered by plants or exposed. These descriptions do not measure every property. A surface that looks dry may have moisture below it, and appearance alone cannot identify all the materials in soil.

A useful plan states the question, the place and time, what will be observed, and how records will be made. It should also identify limits. If one bed has more plant kinds on one visit, that result supports a comparison for that place and time. It does not prove that water or soil caused the difference. Other conditions may differ too.

Use a clear, safe plan and record observations consistently.
Describe visible evidence without claiming more than it shows.
A result can suggest a connection without proving its cause.

3. Succession and sustainability

A place can change over time. Succession is the gradual change in the kinds of organisms living in an area. For example, after bare ground is left undisturbed, some plants may begin to grow. Later, other plants may become established. The exact changes depend on the place and its conditions. Succession is not a promise that every area follows the same sequence.

Plants can affect the conditions around them. Their roots may hold soil in place, and plant cover can affect how much bare ground is exposed. When plants die, their remains can become part of the soil over time. These ideas help explain why biodiversity, water, soil, and succession are worth investigating together. They do not mean that one observation can reveal every process happening in a place.

A simple model can show a possible sequence: bare ground, early plant growth, then a changed plant community. A model is a simplified representation used to think about a system. It leaves out details, such as the exact organisms, weather, and time involved. The model helps organize ideas, but evidence from the actual place is needed to describe what is happening there.

Sustainability questions can include both science and human choices. Science can provide evidence about organisms, water, soil, and change over time. A decision about how a place should be used may also involve community needs and values. Those judgments should not be presented as if they were measurements made by an investigation.

Succession is gradual change in the organisms living in an area.
A model helps organize ideas but simplifies real places.
Scientific evidence can inform decisions without deciding values for people.

4. Compare carefully and explain limits

When comparing records, look for patterns that are actually supported. If one area has more kinds of visible plants and more plant cover on the day observed, you can report that pattern. You cannot conclude from that alone that the area has better soil, more available water, or greater sustainability. Those ideas need suitable evidence too.

Useful questions include: Were the areas the same size? Were they observed at similar times? Could some organisms have been missed? Did the observation describe water and soil directly, or only plant growth? Naming these limits makes a conclusion more accurate, not less useful.

Repeat observations can help show whether a pattern is consistent, provided they are made in a comparable way. A single visit is a snapshot. Even repeated observations do not automatically explain why a pattern exists. A careful report states what was observed, what it might suggest, and what remains unknown.

A conclusion should match the evidence collected.
A snapshot is limited to the place and time observed.
Repeated, comparable observations can strengthen a description of a pattern.

From observation to careful conclusion

What is recorded	What it can support	What it cannot establish alone
Kinds of visible plants in equal areas	A comparison of visible plant variety at the time observed	Every organism present or the cause of a difference
Ground looks wet or dry	A description of apparent surface condition	Moisture below the surface or the full water supply
Bare ground or plant cover	A description of visible ground cover	A guaranteed future succession sequence

Worked example

Comparing plant variety

A class wants to compare visible plant variety in two parts of a school garden. How can it make a fair, safe comparison, and what could it conclude?

A fair garden comparison

This is a planning model, not a record of actual garden observations. It omits details such as weather and organisms that may be hidden.

Set the comparison
Choose two equal-sized areas and observe them on the same day. This reduces differences caused by area size or timing. Use a teacher-approved location and avoid disturbing plants.
Record evidence
Make a checklist of distinct visible plant kinds in each area. Record the observation method and note that hidden or hard-to-identify organisms may be missed.
State a limited conclusion
If one area has more kinds on the checklist, report that it had greater visible plant variety in this comparison. Do not claim that it has greater total biodiversity or that soil or water caused the difference.

Answer: Use equal-sized areas, similar timing, and the same recording method. Report the visible plant variety observed, not every organism present or an untested cause.

Check: The comparison describes evidence from one method and time. It does not establish why the areas differ.

Worked example

Reading a hypothetical water-and-plant record

Suppose a student records that a planted patch looked moist and had several visible plant kinds, while a nearby bare patch looked dry and had few visible plant kinds. What is a careful interpretation?

Identify the evidence
The record describes visible plant variety and the apparent surface condition of each patch. Treat this as hypothetical practice information, not as a real measurement.
Notice the pattern
In this hypothetical observation, the patch that looked moist also had more visible plant kinds. That is a pattern in the record, not proof that moisture caused the difference.
Name what is missing
The student has not measured moisture below the surface or described other possible differences between the patches. A careful report says the observations occurred together and identifies what further evidence would be needed.

Answer: The hypothetical record shows an association between apparent surface moisture and visible plant variety in these patches. It does not establish cause, total biodiversity, or soil condition.

Check: The interpretation is limited to what was observed and does not treat appearance as a complete measurement.

Worked example

Using a succession model

A class sees bare ground in one part of a schoolyard and wonders whether plants might establish there over time. How can a model help, and what should the class avoid claiming?

A simplified succession model

Conceptual model only. It is not to scale, gives no time scale, and does not claim that every site follows this sequence.

Use a simple sequence
Represent a possible change from bare ground to early plant growth and then to a changed plant community. This makes succession easier to discuss.
Connect the model to evidence
The sequence is a model, not an observation of what will happen in this schoolyard. The class would need observations at different times to describe actual change there.
State the limit
Do not claim that every bare patch develops in the same way or on the same schedule. Conditions vary, and the model leaves them out.

Answer: A succession model suggests a possible gradual change in organisms. Observations over time are needed to describe what actually occurs at the site.

Check: The model explains an idea; it does not provide site-specific evidence or a guaranteed outcome.

Common mistakes and how to avoid them

Calling a place more biodiverse because it has more individual plants.

Correction: Biodiversity concerns variety of living things. Count different kinds, and state which organisms your method could detect.

Treating a wet-looking surface as proof that water caused more plant growth.

Correction: Appearance is limited evidence. Report the pattern, and do not claim a cause without suitable evidence.

Assuming succession always follows one fixed sequence.

Correction: Succession is gradual change, but the organisms and pattern can differ among places.

Presenting a preference about land use as a scientific measurement.

Correction: Keep observations and evidence distinct from values and decisions about what people should do.

Lesson summary

Biodiversity is the variety of living things in a place.
Water and soil are important parts of the conditions in which organisms live.
Succession is gradual change in the organisms living in an area.
A safe, fair investigation uses a clear question and consistent observations.
Conclusions should match the evidence and name important limits.
Scientific findings can inform sustainability decisions, while social and ethical judgments remain distinct.

Check your understanding

Question 1

A student counts more kinds of visible plants in one equal-sized garden area than another during one visit. Which conclusion is best supported?

The first area had greater visible plant variety in this comparison.
The first area has greater biodiversity in every season.
The soil in the first area caused the difference.
The first area is always more sustainable.

Show answer and explanation

The first area had greater visible plant variety in this comparison.

The observation supports a limited comparison of visible plant variety at that time. It does not establish a cause or a complete measure of biodiversity.

Question 2

Why should a class avoid disturbing organisms while observing a school garden?

Disturbance can affect the place being investigated, and observation can often be done without it.
Disturbance guarantees that every organism will be seen.
A disturbed area always has more biodiversity.
Safe investigation means observations cannot be recorded.

Show answer and explanation

Disturbance can affect the place being investigated, and observation can often be done without it.

Respectful, teacher-approved observation helps protect the organisms and makes the investigation safer.

Question 3

What does a succession model show?

One possible way organisms in an area may change over time.
The exact future of every bare patch.
A direct measurement of soil and water at a site.
Proof that all plant communities change at the same speed.

Show answer and explanation

One possible way organisms in an area may change over time.

A model represents an idea in simplified form. It does not predict every site's exact changes.

Key terms

Biodiversity: The variety of living things in a place.
Evidence: Information gathered through observations or other suitable methods that can support a conclusion.
Investigation: A planned way to gather and compare evidence.
Model: A simplified representation that helps explain or think about a system.
Soil: Loose material on the ground in which many plants grow.
Succession: Gradual change in the kinds of organisms living in an area.
Sustainability: Considering whether people can meet needs while keeping environmental systems able to support life over time.

Continue through SNC1W

View the complete SNC1W Ontario Grade 9 Science curriculum and lessons

About this lesson and its review

Published by DoAssignment. This reviewed lesson follows Ontario Grade 9 Science (SNC1W), expectation B2.4. It is a study resource, not an official curriculum publication.

Before publication, content is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability. Errors can still occur, so corrections are welcomed.

Official curriculum reference

Report a correction or ask a question