3.1.2 Section B: The living world |
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3.1.2.1 Ecosystems
Key Idea Ecosystems exist at a range of scales and involve the interaction between biotic and abiotic components. What is an ecosystem? An ecosystem is a community of living organisms (plants and animals) sharing an environment, this can range from a pond to woodland, a field to mountain. What is a biome? A biome is a very large ecosystem e.g. Desert or rainforest An ecosystem is a balanced natural system made up of climate, plants, animals and soil. These elements interrelate and depend upon each other. An ecosystem includes all of the living organisms in a specific area. These systems are the plants and animals interacting with their non-living environments (weather, earth, sun, soil, atmosphere). An ecosystem's development depends on the energy that moves in and out of that system. An example of a small scale UK ecosystem to illustrate the concept of interrelationships within a natural system, an understanding of producers, consumers, decomposers, food chain, food web and nutrient cycling. Image 1 - Pond Food Web2 simple food chains from the complex food web above
Did you know that as you move up the food chain the transfer of energy is not complete and about 90% of energy is lost through heat. This leaves only 10% of energy available to the consumer for growth.
Nutrient Cycle A nutrient cycle is the movement and exchange of organic and inorganic matter into the soil and back into living matter. Therefore ecosystems are highly reliant on decomposers. These are organisms that break down dead material in an ecosystem and return the nutrients from them into the soil. These nutrients can then be used by other plants for further growth. Decomposers are often bacteria and fungi, but could also be types of insect like dung beetles, worms that we find in compost bins, or the rat tailed maggot found in ponds. Nutrients then, are the food that plants need for growth, and include Potash, Nitrogen and Potassium. Nutrients can be added from rainwater, weathered out of rocks or recycled by decomposers. |
Key Terms
Video 1 - Ecosystem EcologyVideo 2 - The hydrological and carbon cycleImage 2 - Soil and Nutrient Cycles |
Task - using the internet and your textbook find an example of a small scale ecosystem in the UK. Find or create a suitable food web from the ecosystem. Identify the producers, consumers and decomposers in the food web. Draw a systems diagram to show a food chain from the ecosystem.
Task - answer the following questions
Task - answer the following questions
- What happens to the size and number of consumers as you move up the food chain?
- Why are there only a few top consumers?
- Why do the top consumers have to eat so much food?
- what natural factors can affect an ecosystem?
- What human factors can affect an ecosystem?
The impact on the ecosystem of changing one component.
Factors that directly or indirectly cause changes to an ecosystem are referred to as drivers. A direct driver, such as a tropical storm, visibly impact an ecosystem. Where as an indirect driver, such as human-induced climate change, operates on a more subtle level by influencing direct drivers, such as the frequency and severity of tropical storms. For this reason, it is difficult to determine to what degree a change within an ecosystem are a result of humans or natural forces. Typically more changes to ecosystems are not sudden and instead are gradual and over time. Some examples of changes to an ecosystem could be the removal of dangerous animals such as bears and wolves for the safety of people. But the reduction of these animals would increase the numbers of primary/secondary consumers such as rabbit and deer. The example of change we are going to study is the removal and reintroduction of wolves to Yellowstone national park. Task - using videos 4 and 5, your own research and the textbook assess the reintroduction of Grey Wolf to Yellowstone National Park.
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Video 3 - Human Impacts on the EnvironmentsVideo 4 - Wolf CascadeVideo 5 - How wolves change rivers |
An overview of the distribution and characteristics of large scale natural global ecosystems.
Climates are influenced by many factors, such as the proximity to the equator or the poles, the proximity to the sea, as well as things like ocean currents, atmospheric pressure belts and prevailing winds.
Furthermore a place's climate influences the types of vegetation and animals that live there and therefore the ecosystems that exist. It is possible to divide the world into a number of climatic zones or biomes, each with their own characteristic climate, vegetation and wildlife. Watch video 6. Head over to this webpage to find out on the world's major biomes. Task - Consider the mark scheme opposite for the following 2 mark exam style question
Describe the distribution of hot deserts Now consider the mark scheme to answer the following 2 mark questions 1. Describe the distribution of the tropical rainforests 2. Describe the distribution of the tundra biome 3. Describe the distribution of the savanna biome 4. Describe the distribution of the coniferous forest |
Video 6 - Introduction to Biomes and Climates |
Peer assess on completion. Ensure you check geographical content and accuracy for instance did they give the correct latitudes? Have they used the names of appropriate countries and continents? Did they use directions instead of above/below, left/right?
3.1.2.2 Tropical rainforests
Key Idea Tropical rainforest ecosystems have a range of distinctive characteristics. The physical characteristics of a tropical rainforest. Climate- It is the same all year round, there are no definite seasons. It is hot between 20-28c. This is because it is near the equator, the sun is overhead all year round. Rainfall is very high around 2000mm per year (annum). It rains every day usually in the afternoon. Soil- is not very fertile as the heavy rain washes the nutrients away (leaching). There are nutrients at the surface due to decay from leaves that have fallen but the layer is thin (Humus) as decay is fast due to warm, moist conditions. Vegetation- most trees are evergreen to take advantage of the continual growing season. The vegetation can be split into 4/5 distinct layers - the emergents, the canopy, the undercanopy, the shrub layer and the forest floor. Some categorisations will place the shrub layer and forest floor as one layer. Watch video 8 for more details of the layers. Animals- more animals species than any other ecosystem including microscopic animals, invertebrates (like insects and worms), fish, reptiles, amphibians, birds, and mammals. The interdependence of climate, water, soils, plants, animals and people. Interdependence means the dependence between two or more things such as people, places, systems. Within the tropical rainforest there are a large number of dependent relationships between the biotic and abiotic features for instance trees depend on the nutrient cycle which is dependent on decomposers to return dead leaf litter to the soil. Watch video 9 for details of the interdependent relationships within the tropical rainforest, pay particular attention to the water and nutrient cycles. How plants and animals adapt to the physical conditions. Issues related to biodiversity. Key Idea Deforestation has economic and environmental impacts Changing rates of deforestation. A case study of a tropical rainforest to illustrate: • causes of deforestation – subsistence and commercial farming, logging, road building, mineral extraction, energy development, settlement, population growth • impacts of deforestation – economic development, soil erosion, contribution to climate change. Key Idea Tropical rainforests need to be managed to be sustainable. Value of tropical rainforests to people and the environment. Strategies used to manage the rainforest sustainably – selective logging and replanting, conservation and education, ecotourism and international agreements about the use of tropical hardwoods, debt reduction. |
Video 7 - Virtual Fieldtrip of the AmazonVideo 8 - Layers of the TRFTask - download the cross-section of the TRF task sheet below and follow the instructions to describe and explain the physical characteristics of the layers of the tropical rainforest.
Video 9 - How the forest works |
3.1.2.4 Cold environments
Key Idea
Cold environments (polar and tundra) have a range of distinctive characteristics
The physical characteristics of a cold environment. The interdependence of climate, permafrost, soils, plants, animals and people. How plants and animals adapt to the physical conditions. Issues related to biodiversity
Key Idea
Development of cold environments creates opportunities and challenges.
A case study of a cold environment to illustrate: • development opportunities in cold environments: mineral extraction, energy, fishing and tourism • challenges of developing cold environments: extreme temperature, inaccessibility, provision of buildings and infrastructure.
Key Idea
Cold environments are at risk from economic development.
The value of cold environments as wilderness areas and why these fragile environments should be protected. Strategies used to balance the needs of economic development and conservation in cold environments – use of technology, role of governments, international agreements and conservation groups.
Key Idea
Cold environments (polar and tundra) have a range of distinctive characteristics
The physical characteristics of a cold environment. The interdependence of climate, permafrost, soils, plants, animals and people. How plants and animals adapt to the physical conditions. Issues related to biodiversity
Key Idea
Development of cold environments creates opportunities and challenges.
A case study of a cold environment to illustrate: • development opportunities in cold environments: mineral extraction, energy, fishing and tourism • challenges of developing cold environments: extreme temperature, inaccessibility, provision of buildings and infrastructure.
Key Idea
Cold environments are at risk from economic development.
The value of cold environments as wilderness areas and why these fragile environments should be protected. Strategies used to balance the needs of economic development and conservation in cold environments – use of technology, role of governments, international agreements and conservation groups.