Geography (9230) | Ecosystems

Hello, future geographers! Welcome to the world of Ecosystems!

This chapter is all about how living things (like animals and plants) interact with non-living things (like water, air, and soil) to create fantastic natural systems. It’s like studying a giant, complex community where everything relies on everything else.

Don't worry if some of the words seem tricky at first. We will break them down step-by-step! Understanding ecosystems is vital because they are the foundation of "The living world" section and help us understand environmental issues later on.

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Section 1: Defining the Ecosystem

1.1 What is an Ecosystem?

An Ecosystem is simply a natural unit consisting of all the living things (plants, animals, microorganisms) and the non-living physical environment in which they interact.

Analogy: Think of a fish tank. The fish and plants are the living parts, and the water, rocks, filter, and light are the non-living parts. The entire tank, and how these parts work together, is an ecosystem.

1.2 Components of an Ecosystem

Every ecosystem has two essential components:

• Biotic Components: These are the living parts of the ecosystem.
  Examples: Plants, animals, bacteria, fungi.
• Abiotic Components: These are the non-living (physical) parts of the ecosystem.
  Examples: Climate (temperature, rainfall), light, soil, water, oxygen levels.

Memory Aid: "Bio" means life (like Biology!). So, Biotic is the living part.

1.3 Scale of Ecosystems

Ecosystems can be tiny or huge. The same basic rules apply whether we are looking at:

• Small Scale (Local): A rotting log, a garden pond, or a hedgerow.
• Medium Scale: A forest, a large lake, or a mountain range.
• Global Scale: A Biome (e.g., the entire Amazon Rainforest, or all the world’s deserts).

Section 2: Interdependence and Roles

2.1 Interdependence: Everything is Connected

Interdependence means that every organism (living thing) in an ecosystem depends on other living and non-living things for survival. If one part is removed or changed, it affects the whole system.

Analogy: Think of a set of dominoes. If you remove or push one, the whole chain reaction changes.

• If rainfall (abiotic) decreases, plants (biotic) die.
• If plants die, animals (biotic) that eat them starve.
• If the soil quality (abiotic) is poor, it limits which plants can grow.

2.2 Key Roles in the Ecosystem (Trophic Levels)

Within an ecosystem, every living thing plays a specific role in moving energy and nutrients around.

1. Producers:

• These organisms produce their own food, usually through photosynthesis (using sunlight).
• They form the base of every food chain.
• Examples: All green plants and algae.

2. Consumers:

• These organisms get energy by eating other organisms.
• Primary Consumers (Herbivores): Eat producers (e.g., rabbits eating grass).
• Secondary Consumers (Carnivores/Omnivores): Eat primary consumers (e.g., foxes eating rabbits).
• Tertiary Consumers: Eat secondary consumers (e.g., eagles eating snakes).

3. Decomposers:

• These organisms break down dead organisms and waste material.
• They are incredibly important because they return essential nutrients back into the soil for the producers to use again.
• Examples: Bacteria, fungi, earthworms.

Section 3: Energy Flow - Food Chains and Webs

3.1 The Flow of Energy

Energy moves through an ecosystem when one organism eats another. This movement is shown by a Food Chain.

Food chains always start with a producer (plant) and the arrows show the direction of energy flow (what is eaten by what).

Example: Grass → Rabbit → Fox → Eagle

3.2 Food Webs

In reality, animals rarely eat just one type of organism. A Food Web shows how multiple food chains link together in an ecosystem, giving a more realistic picture of energy transfer.

3.3 The 10% Rule (Energy Loss)

This is a crucial concept. When energy is transferred from one trophic level (one level of the food chain) to the next, most of it is lost.

• Only about 10% of the energy is transferred and stored in the body of the consumer.
• The remaining 90% is lost, mainly through heat (movement, breathing, keeping warm) or as waste material.

This is why food chains usually have only 4 or 5 levels—there simply isn't enough energy left to support more consumers at the top!

Analogy: Imagine trying to fill a bucket that has a giant hole in it (the 90% loss). If you keep pouring water up through many leaky buckets, by the time you reach the top bucket, there will only be a small amount of water left!

Section 4: Nutrient Cycling

4.1 The Importance of Recycling

Unlike energy, which flows through an ecosystem and eventually leaves (as heat), nutrients (like nitrogen and potassium from the soil) are constantly recycled. This keeps the ecosystem going.

Here is the simple four-step cycle of nutrients:

Step 1: Uptake

• Plants (Producers) take nutrients from the soil or water through their roots.

Step 2: Consumption

• Animals (Consumers) eat the plants, incorporating the nutrients into their bodies.

Step 3: Waste and Death

• Nutrients are returned to the ground via animal waste or when any organism (plant or animal) dies.

Step 4: Decomposition

• Decomposers break down the dead matter and waste, releasing the nutrients back into the soil, ready for plants to use again. The cycle repeats!

Key Takeaway: The nutrient cycle is a closed loop, meaning nutrients are reused over and over.

Section 5: Global Ecosystems (Biomes)

5.1 What is a Biome?

A Biome is a very large-scale global ecosystem defined by its dominant vegetation type, which is determined by the climate (temperature and rainfall). Biomes are often called major global ecosystems.

The location of these biomes is closely linked to latitude (distance from the equator) because latitude heavily influences temperature and rainfall.

5.2 Major Biomes of the World

You need to know the location and general characteristics of the main biomes:

1. Tropical Rainforest

• Location: Found near the Equator (low latitudes), especially in South America (Amazon) and Southeast Asia.
• Characteristics: High temperatures and very high rainfall all year round. Highest levels of biodiversity (variety of life) on Earth. Vegetation is layered and dense.

2. Desert

• Location: Usually found around 30° North and South of the Equator (e.g., Sahara, Arabian Desert).
• Characteristics: Very low rainfall (less than 250mm per year). Can be hot during the day and cold at night. Plants (like cacti) and animals are highly adapted to survive extreme dryness.

3. Grassland (Savanna and Temperate)

• Location: Often found between tropical forests and deserts.
• Characteristics: Dominated by grass rather than large trees. They have distinct wet and dry seasons (Savanna) or hot summers and cold winters (Temperate).

4. Temperate Deciduous Forest

• Location: Mid-latitudes, where we experience four distinct seasons (e.g., most of Europe, Eastern USA).
• Characteristics: Trees lose their leaves in winter to conserve water. Moderate temperature and rainfall.

5. Taiga (Boreal Forest)

• Location: High latitudes, covering large parts of Canada, Russia, and Scandinavia.
• Characteristics: Cold and snowy winters; short, mild summers. Dominated by evergreen (coniferous) trees because the needles are adapted to cold weather and poor soils.

6. Tundra

• Location: Very high latitudes (near the poles) and high mountains.
• Characteristics: Extremely cold, low precipitation. Soil is often permanently frozen (permafrost). Only mosses, lichens, and small shrubs can grow here.