GRADE 9 Integrated Science LIVING THINGS AND THEIR ENVIRONMENT – The interdependence of life Notes

Integrated Science — Living Things and Their Environment

Subtopic: The interdependence of life (age 14, Kenya)

Learning goals:

• Define interdependence and explain how living things depend on one another and on the environment.
• Describe producers, consumers and decomposers and how energy flows in a food chain/web.
• Give Kenyan examples (e.g., acacia and ants, pollination of crops, savanna food chains).
• Show simple human impacts and ways to protect interdependence in ecosystems.

1. What is interdependence?

Interdependence means that living things (plants, animals, microorganisms) need one another to survive. For example:

• Plants give animals food and oxygen.
• Animals help plants by spreading seeds and pollen.
• Decomposers return nutrients to the soil so plants can grow again.

2. Key parts of an ecosystem

• Producers (autotrophs) — make their own food by photosynthesis. Example: grasses, maize, acacia trees.
• Consumers — eat other organisms.
  • Primary consumers: herbivores (e.g., gazelles, zebras).
  • Secondary consumers: carnivores that eat herbivores (e.g., jackals, hyenas).
  • Tertiary consumers: top predators (e.g., lions, eagles).
• Decomposers — break down dead plants and animals (e.g., bacteria, fungi, dung beetles) and recycle nutrients.

3. Food chain — simple visual

A food chain shows how energy moves from one organism to another. Example from the Kenyan savanna:

4. Food web — many links

In real ecosystems many food chains join to form a food web. Energy flows through many paths.

5. Symbiosis — relationships between species

Symbiosis means close relationships between species. Types:

• Mutualism — both benefit. Example: acacia trees and ants. Ants live on acacia, protect the tree from browsers; tree gives nectar and shelter to ants.
• Commensalism — one benefits, the other not harmed. Example: birds nesting in large trees.
• Parasitism — one benefits, the other harmed. Example: ticks on cattle or malaria parasites in humans.

6. Why interdependence matters

• Loss of one species can affect many others (e.g., fewer pollinators = lower crop yields).
• Decomposers keep soil fertile — without them plants cannot grow well.
• Humans rely on healthy ecosystems for food, water, medicine and clean air.

7. Human impacts and how to help

Harmful actions: deforestation, overgrazing, pollution, overfishing. These break interdependence.

Ways to help:

• Plant trees and protect native vegetation (e.g., plant indigenous trees in school compound).
• Use pesticides carefully; protect pollinators like bees.
• Reduce waste and compost organic matter to feed the soil.
• Support conservation of national parks and protected species.

8. Short class activity (10–15 minutes)

1. In groups, draw a food web from a nearby environment (school garden, farm or nearby field). Include at least 6 organisms.
2. Identify producers, consumers and decomposers. Mark any mutual relationships you spot.
3. Discuss one way humans could improve or harm the web and report back.

9. Revision questions

1. Define interdependence in your own words. (1 mark)
2. Name one example of mutualism found in Kenyan ecosystems. Explain the benefits. (2 marks)
3. Draw a short food chain of 4 organisms from a maize field and label producers and consumers. (3 marks)
4. Explain why decomposers are important for farming. (2 marks)
5. Give two ways human activity can break interdependence and one action to reduce harm. (2 marks)

Answers (short)

• Interdependence: living things depend on one another and their environment for survival.
• Example mutualism: acacia and ants — ants get food/shelter, ants protect tree from browsers.
• Maize field food chain (example): Maize (producer) → Maize stem borer caterpillar (primary consumer) → Small bird (secondary consumer) → Hawk (tertiary consumer).
• Decomposers break down dead material to release nutrients for plants — keeps soil fertile.
• Human harms: deforestation, pollution, overuse of pesticides. Reduce harm by planting trees, using integrated pest management, protecting habitats.