B13. Human influences on ecosystems

 (0654) Coordinated Sciences 2023/2024

Subheadings and Key concepts

• the Carbon cycle
• deforestation:
• extinction of species/ loss of biodiversity
• soil erosion
• flooding
• increase in atmospheric CO2
• water pollution
• eutrophication

B12. Organisms and their Environment

 (0654) Coordinated Sciences 2023/2024

Subheadings and Key concepts

• food chain, food web
• producer, consumer
• herbivore, carnivore, decomposer
• ecosystem, trophic level
• energy transfer between trophic levels

14. Ecosystem pdf

# 147 Summary of Ecosystem

Energy enters ecosystems in sunlight. Producers (photosynthetic plants) capture some of this energy and transfer it to organic substances such as carbohydrates. Consumers (animals and fungi) gets their energy by eating producers or other consumers. 

#146 Population size, factors affecting the rate of growth

A population is a group of organisms of one species, living in the same area at the same time. Factors affecting the rate of population growth include food supply, predation and disease. 

#145 Effects of combustion of fossil fuels on CO2 level

Photosynthesis takes CO₂ out of the atmosphere and replaces it with O₂. Respiration and combustion both do the opposite: they use up O₂ and replace it with CO₂.

#144 Nitrogen cycle

Nitrogen is essential for the formation of amino acids to make proteins. The nitrogen cycle describes the ways in which nitrogen is recycled.

#143 Nutrient cycles - Carbon and water cycles

Most of the chemicals that make up living tissue contain carbon. When organisms die the carbon is recycled so that it can be used by future generations. Four main processes are involved: photosynthesis, respiration, decomposition and combustion. 

#142 Food chain and energy efficiency

In term of conversations of energy, there is an increased efficiency in supplying green plants  as human food and a relative inefficiency in feeding crop plants  to animals.

#141 Food pyramids of numbers, biomass and energy

A food pyramid shows the relative sizes of different components at the various trophic levels of a food chain. There are three types of ecological pyramid we use: numbers, biomass and energy.

# 140 Food web

Food web is a network of interconnected food chains showing the energy flow through part of an ecosystem.

#139 Food chain

Credit: BBC Bitesize

Food  chain is a chart showing the flow of energy (food) from one organism to the next beginning with a producer.

#138 Energy flow, energy loss

The Sun is the principal source of energy input to biological systems. The Earth receives 2 main types of energy from the Sun: light (solar) and heat. Photosynthetic plants and some bacteria can trap light energy and convert it into chemical energy.