Ecosystems and Food Webs Chapter Notes | Natural Science and Technology (Grade 6-A) PDF Download

Different Ecosystems

An ecosystem is a self-sustaining area where living things (plants, animals, microorganisms) and non-living things (air, water, soil, sunlight) interact and depend on each other for survival. Ecosystems vary widely across the planet, each with unique features, climates, and organisms adapted to their environment.

Types of Ecosystems

• Rivers: Flowing water systems supporting fish, plants, and other aquatic life.
• Mountains: High-altitude areas with rocky terrain and specialized plants and animals.
• Sea and Rocky Shores: Coastal ecosystems with marine life like crabs and seaweed.
• Ponds and Wetlands: Freshwater areas with plants like reeds and animals like frogs.
• Arctic and Alpine Tundra: Cold regions near the poles with no trees, only shrubs and dwarf plants growing in wet or permafrost soil.
• Grasslands: Includes tropical savannas (e.g., South African bushveld) and temperate grasslands, supporting grasses and grazing animals.
• Forests: Includes tropical rainforests and temperate forests with coniferous or deciduous trees, home to diverse herbivores and carnivores.
• Deserts and Semi-Deserts: Arid regions with sparse vegetation and animals adapted to low water.

Unique South African Ecosystem: Fynbos
South Africa’s fynbos biome is a unique ecosystem found nowhere else in the world. It is famous for its incredible plant biodiversity, including the King Protea, South Africa’s national flower. Fynbos plants are adapted to harsh, windy conditions and frequent fires, with seeds that often germinate only after being scorched. This biome supports a wide variety of plants and animals, thriving in the Western Cape’s specific climate.

Living and Non-Living Things in Ecosystems

Ecosystems rely on a balance between living and non-living components. Living things include plants, animals, and microorganisms, while non-living things include air, water, soil, sunlight, and rocks. A healthy ecosystem maintains this balance and supports sufficient biodiversity, which is the variety of plant and animal species in an area.

Non-Living Things in Ecosystems

• Air: Provides oxygen for animals and carbon dioxide for plants.
• Water: Essential for drinking, photosynthesis, and as a habitat for aquatic organisms.
• Sunlight: Powers photosynthesis, enabling plants to produce food.
• Soil and Sand: Supports plant growth and provides shelter for animals like ants.
• Rocks: Offer habitats or structural features in ecosystems.

Importance of Balance

A healthy ecosystem requires a delicate balance between living and non-living things. Disruptions, such as drought drying up rivers, soil erosion, or lack of sunlight in man-made forests, can reduce biodiversity and harm the ecosystem. 
For example:

• A dried river bed reduces water availability, affecting plants and animals.
• Soil erosion removes nutrients, making it hard for plants to grow.
• Dense tree canopies, like in pine plantations, block sunlight, limiting undergrowth and animal habitats.

Role of Water

Water is vital for ecosystems:

• Habitat: Supports aquatic organisms and breeding grounds for plants and animals.
• Chemical Reactions: Acts as a solvent for processes like photosynthesis, where plants use water, sunlight, and carbon dioxide to make glucose.
• Plant Reproduction: Some seeds are dispersed by water, aiding plant spread.

Food Webs

In ecosystems, plants and animals are connected through feeding relationships, forming complex networks called food webs. Plants produce their own food, while animals consume plants or other animals, creating a system of producers and consumers.

Producers and Consumers

• Herbivores: Eat only plants (e.g., mice eating grass).
• Carnivores: Eat only meat or eggs (e.g., snakes eating mice).
• Omnivores: Eat both plants and animals (e.g., humans).
• Insectivores: Eat only insects (e.g., certain birds).
• Scavengers: Eat dead animals (e.g., vultures).
• Decomposers: Microorganisms like bacteria, fungi, and mushrooms that break down dead plant and animal matter, recycling nutrients into the soil for plants to use.

Food Chains and Food Webs

• Food Chain: A simple sequence showing feeding relationships, starting with a producer and ending with a consumer, scavenger, or decomposer (e.g., leaf → caterpillar → chameleon → mongoose → snake).
• Food Web: A complex network of interconnected food chains within an ecosystem, showing multiple feeding relationships (e.g., a savanna food web where a snake eats lizards and mice, not just chameleons).

Consumer Levels
Consumers are categorized by their role in the food web:

• Primary Consumers: Herbivores that eat plants (e.g., mice in a savanna).
• Secondary Consumers: Eat primary consumers (e.g., snakes eating mice).
• Tertiary Consumers: Eat secondary or primary consumers (e.g., hawks eating snakes or mice).

Points to Remember

• In America, grasslands are called prairies; in Asia, steppes; in South America, Pampas; and in South Africa, bushveld or savanna.
• South Africa’s fynbos biome is unique, with diverse plants like the King Protea, adapted to fire and windy conditions.
• Ecosystems are self-sustaining areas where living and non-living things depend on each other.
• Biodiversity refers to the variety of plant and animal species in an ecosystem, crucial for its health.
• Water is essential as a habitat, for chemical reactions like photosynthesis, and for seed dispersal.
• Food webs illustrate complex feeding relationships, connecting producers (plants) and consumers (animals).
• Decomposers, like bacteria and fungi, recycle nutrients from dead matter back into the soil.
• Human activities, like overgrazing, can disrupt ecosystems, but conservation efforts, like reintroducing native species, can restore balance.

Difficult Words

• Ecosystem: An area where living (plants, animals, microorganisms) and non-living (air, water, soil) things interact and depend on each other.
• Biodiversity: The variety of plant and animal species in an ecosystem.
• Fynbos: A unique South African biome with diverse plants, like the Protea, adapted to fire and harsh conditions.
• Producers: Plants that make their own food through photosynthesis.
• Consumers: Animals that eat plants or other animals, including herbivores, carnivores, omnivores, insectivores, scavengers, and decomposers.
• Herbivores: Animals that eat only plants.
• Carnivores: Animals that eat only meat or eggs.
• Omnivores: Animals that eat both plants and animals.
• Insectivores: Animals that eat only insects.
• Scavengers: Animals that eat dead animals.
• Decomposers: Microorganisms that break down dead matter, recycling nutrients into the soil.
• Food Chain: A simple sequence showing who eats whom in an ecosystem, starting with a producer.
• Food Web: A complex network of interconnected food chains in an ecosystem.

Summary

Ecosystems are self-sustaining areas where living and non-living things, like plants, animals, water, and sunlight, interact and depend on each other. They vary from rivers and forests to South Africa’s unique fynbos biome, which supports diverse plants adapted to fire. A healthy ecosystem maintains a balance between living and non-living components, with biodiversity ensuring stability. Water is critical for habitats, photosynthesis, and plant reproduction. Food webs show complex feeding relationships, with plants as producers and animals as consumers (herbivores, carnivores, etc.). Decomposers recycle nutrients, sustaining the ecosystem. Human actions can disrupt ecosystems, but conservation can restore balance, ensuring the survival of diverse species.