Species Diversity

Term 1, Week 1, Lesson 4

Do Now

In your book, answer this question:

“Why do you think it’s important to have many different species in an ecosystem?”

Write 2–3 sentences explaining your thinking.

You have 3 minutes.

Daily Review

Answer the following 5 multiple choice questions in your book:

1. What is predation?
   • 1. When organisms work together
   • 2. When one organism hunts and eats another
   • 3. When organisms compete for food
   • 4. When organisms share a home
2. If water availability decreases in an ecosystem, what is likely to happen first?
   • 1. More animals will appear
   • 2. Plants will grow faster
   • 3. Plants may die or struggle
   • 4. Nothing will change
3. Competition occurs when:
   • 1. Organisms help each other
   • 2. Organisms fight for the same resources
   • 3. Organisms ignore each other
   • 4. Organisms live in different places
4. If a predator is removed from an ecosystem, the prey population will likely:
   • 1. Decrease
   • 2. Stay the same
   • 3. Increase
   • 4. Disappear completely
5. A change in one factor in an ecosystem:
   • 1. Only affects that one factor
   • 2. Can affect many other parts of the ecosystem
   • 3. Has no effect on anything
   • 4. Only affects abiotic factors

Learning Intentions

Today we are learning about species diversity and why it is important for healthy ecosystems.

Success Criteria

You will be successful if you have:

• Defined species diversity
• Explained why species diversity is important for healthy ecosystems
• Compared the diversity of different ecosystems

Keywords

Species diversity

The variety of different species in an ecosystem, including both the number of species and how evenly they are distributed.

Biodiversity

The variety of all living things on Earth, including diversity within species, between species, and of ecosystems.

Ecosystem stability

The ability of an ecosystem to maintain its structure and function over time, even when disturbed.

Resilience

The ability of an ecosystem to recover after a disturbance.

Learning Activities

Activity 1 — I DO: Understanding Species Diversity

Species diversity is a key measure of ecosystem health.

What is Species Diversity?

Species diversity has two parts:

1. Species richness — How many different species are present
2. Species evenness — How evenly individuals are distributed among species

Example:

Ecosystem A	Ecosystem B
100 kangaroos	25 kangaroos
2 wombats	25 wombats
1 echidna	25 echidnas
1 snake	25 snakes
Total: 4 species, 104 individuals	Total: 4 species, 100 individuals

Both have the same species richness (4 species), but Ecosystem B has higher diversity because individuals are more evenly distributed.

Why is Species Diversity Important?

Benefit	Explanation
Food web stability	If one species dies out, predators have other food sources
Pollination	Different pollinators can pollinate different plants
Pest control	Natural predators keep pest populations in check
Nutrient cycling	Different decomposers break down different materials
Disease resistance	Diseases are less likely to wipe out all organisms
Resilience	Diverse ecosystems recover faster from disturbances

Comparing High and Low Diversity Ecosystems

High Diversity	Low Diversity
Rainforests	Monoculture farms
Coral reefs	Arctic tundra
Wetlands	Deserts
More stable	More vulnerable
More resilient	Less resilient

What Threatens Species Diversity?

• Habitat destruction
• Pollution
• Climate change
• Invasive species
• Overhunting/overfishing

Check for Understanding

Think about this: Why might a farm with only one crop be more vulnerable to disease than a natural ecosystem?

Answer: If a disease affects that crop, it can spread easily to all plants because they’re all the same species. In a diverse ecosystem, diseases usually only affect certain species, so others survive.

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Activity 2 — WE DO: Calculating Diversity

Let’s practise comparing the diversity of two ecosystems.

Species Count Data

Ecosystem 1: Local Park

Species	Number of Individuals
Magpie	15
Pigeon	45
Sparrow	8
Crow	2
Total	70

Ecosystem 2: Nature Reserve

Species	Number of Individuals
Magpie	12
Kookaburra	10
Lorikeet	14
Wren	11
Honeyeater	13
Parrot	10
Total	70

Discussion Questions

1. Which ecosystem has higher species richness?
2. Which ecosystem has more even distribution?
3. Which ecosystem do you think is healthier? Why?
4. What might happen to the park if pigeons got a disease?

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Activity 3 — YOU DO: Comparing Ecosystems

Complete the worksheet: 114-species-diversity-you-do.docx

You will compare species diversity in different ecosystems and answer questions about the importance of biodiversity.

Work independently. You have 12 minutes to complete the worksheet.

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Notes

Use this space to write any important points from today’s lesson.

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Reflection

End of Week Quiz

Answer these 5 multiple choice questions covering everything from this week:

1. An ecosystem is:
   • 1. Only living things
   • 2. Living and non-living things interacting
   • 3. Only non-living things
   • 4. Just animals
2. Which is a biotic factor?
   • 1. Water
   • 2. Temperature
   • 3. Bacteria
   • 4. Sunlight
3. Abiotic factors are:
   • 1. Living components
   • 2. Non-living components
   • 3. Only animals
   • 4. Only plants
4. Species diversity refers to:
   • 1. Only the number of species
   • 2. Only how species interact
   • 3. The variety of species and their distribution
   • 4. Only rare species
5. Why is high species diversity important?
   • 1. It makes ecosystems more stable and resilient
   • 2. It makes ecosystems simpler
   • 3. It has no effect on ecosystems
   • 4. It only affects plants

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Home-study

Choose an Australian ecosystem (e.g., Great Barrier Reef, Daintree Rainforest, or a local area). Research 5 species that live there and explain why diversity is important for that ecosystem.