B17 Organising an ecosystem Flashcards
(17 cards)
What is a producer?
Plants that begin food chains by making energy from carbon dioxide and water.
What is a food chain?
A sequence (usually shown as a diagram) of feeding relationships between organisms, showing which organisms eat what and the movement of energy through trophic levels.
What are the levels of consumers?
All animals above the producer are called consumers. The first is the
primary consumer
, the next is the secondary consumer. Animals that hunt and kill others are called predators, and those that are hunted and killed are called
prey. The top animal in the feeding relationship is called the apex predator.
What are decomposers?
Decomposers
are bacteria and fungi, which break down dead organisms in a process called decomposition or rotting. They do this by releasing
enzymes onto the dead matter and afterwards, consume the broken down substances. They form a vital role in the recycling of matter. When organisms die and
decompose plants absorb the broken down nutrients through their roots.
What are the stages of the carbon cycle?
Stage1: Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
Stage 2:
Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.
Stage 3:
Animals feed on plants, passing the carbon compounds along the food chain. Most carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die.
Stage 4:
Dead organisms are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.
What is the rate of decay?
The rate of decay is the speed at which dead matter is broken down by decomposers. The rate can be estimated by measuring changes in pH, (for example in milk), change in mass (decaying fruit and vegetables) or change in temperature (grass cuttings).
What key factors affect rate of decay?
Temperature
At colder temperatures decomposing organisms will be less active, thus the rate of decomposition remains low. This is why we keep food in a fridge. As the temperature increases, decomposers become more active and the rate increases. At extremely high temperatures decomposers will be killed and decomposition will stop.
Water
With little or no water there is less decomposition because decomposers cannot survive. As the volume of available water increases, the rate of decomposition also increases. Many decomposers secrete enzymes onto decaying matter and then absorb any dissolved molecules. Without water these reactions cannot occur.
Oxygen
Similar to water, decomposers need oxygen to survive and without it there is little or no decomposition. Oxygen is needed for many decomposers to respire, to enable them to grow and multiply. This is why we often seal food in bags or cling film before putting it in the fridge. As the volume of available oxygen increases, the rate of decomposition also increases. Some decomposers can survive without oxygen. We use these in biogas generators.
How is compost useful?
Gardeners and farmers improve the quality of their soil by adding
compost
or
manure
. Compost is made from dead plants and manure is the waste from animals. Once spread on the soil, compost and manure are broken down into minerals by decomposing bacteria and fungi, as well as by other organisms, such as worms. Adding compost or manure helps recycle minerals so that they are absorbed by new plants and used in growth. Compost and manure also improve the quality of soil by increasing aeration and water retention.
Farmers can also use inorganic fertilisers on soil to overcome specific mineral deficiencies, although this does not require the involvement of decomposers.
One key element which is recycled is nitrogen. This element is needed by plants to make proteins in order to grow and repair themselves. Plants cannot absorb nitrogen gas, and need it to be provided as nitrate ions. These nitrate ions are produced as a result of a long series of reactions by decomposers breaking down proteins and urea in the soil. The nutrients and minerals are then passed along the
food chain
as the organisms are consumed by others.
Describe the main events of the water cycle:
Evaporation: Water from oceans, lakes, rivers, and soil turns into water vapour due to the sun’s heat.
Transpiration: Plants release water vapour into the atmosphere from their leaves.
Respiration: Animals releases water vapour as a by product of respiration
Condensation: As water vapour rises and cools, it changes into tiny water droplets or ice crystals, forming clouds.
Precipitation: Water falls back to Earth from clouds as rain, snow, sleet, or hail.
Surface Run-off: Water flows over the land surface, eventually making its way into rivers, lakes, and oceans.
Percolation/Infiltration: Water seeps into the ground, replenishing groundwater supplies.
Absorption: Plants take up water from the soil through their roots.
Why are decomposers important for a stable ecosystem?
Living organisms remove materials from the environment constantly.
If mineral ions taken from the soil by plants were not replaced, Earth’s
resources would be depleted quickly.
Decomposers break down plant and animal waste and dead animals
and plants and return mineral ions to soil to be taken up by plants
again,
and carbon to the atmosphere as carbon dioxide to be used by
producers in photosynthesis.
Describe the main events of the carbon cycle?
Photosynthesis: Plants and other photosynthetic organisms absorb carbon dioxide (CO2) from the atmosphere and use it to create glucose for energy, releasing oxygen in the process.
Respiration: Plants, animals, and other organisms break down these sugars during respiration to release energy. This process consumes oxygen and releases carbon dioxide back into the atmosphere.
Consumption: Animals obtain carbon by eating plants or other animals. Carbon moves through the food chain as organisms consume one another.
Decomposition: When plants and animals die, decomposers
like bacteria and fungi break down their remains. This process releases carbon back into the atmosphere and soil.
Fossil Fuel Formation: Over millions of years, some dead organic matter can be buried and transformed into fossil fuels like coal, oil, and natural gas. This stores carbon underground.
Combustion: Burning fossil fuels in power plants and vehicles releases the stored carbon back into the atmosphere as carbon dioxide. Deforestation (burning forests) also releases carbon.
Ocean Exchange: The ocean absorbs CO2 from the atmosphere. This CO2 can be used by marine organisms or stored in the deep ocean. The ocean also releases CO2 back into the atmosphere.
Sedimentation: Carbon can be stored in sediments, such as limestone, formed from the accumulation of shells and other organic matter on the ocean floor.
Required practical
Investigate the effect of temperature on the rate of decay of fresh milk by measuring pH change
Aim
To investigate the effect of temperature on the rate of decay of fresh milk by measuring pH change.
Method
Place 20 cm3 of fresh milk into three beakers
Decide the three temperatures you will investigate. Write these onto the sides of the beakers. They may be 5, 20 and 35°C.
Use universal indicator paper or solution to determine the pH of the milk in the three beakers
Cover each beaker in cling film and incubate at the appropriate temperature
Use universal indicator paper or solution to determine the pH of the milk in the three beakers after 24, 48 and 72 hours
Explain fluctuations in prey and predators in a stable community:
Prey Increase: Initially, an abundance of prey allows the predator population to increase due to a readily available food source.
Predator Increase & Prey Decrease: As the predator population grows, they consume more prey, leading to a decline in the prey population.
Predator Decrease: With fewer prey available, the predator population begins to decline due to starvation.
Prey Increase Again:
As the predator population decreases, the prey population starts to recover, beginning the cycle anew.
Explain the stages of the decay cycles?
Decomposition: This is the initial breakdown of organic material by bacteria, fungi, and other decomposers. Larger organisms like insects and scavengers also play a role.
Scavenging: Scavengers consume the larger portions of the decaying matter, breaking it into smaller pieces and spreading it across a wider area.
Putrefaction: This stage involves the breakdown of proteins, leading to the release of gases like ammonia and hydrogen sulfide, which cause the characteristic smell of decay.
Fermentation: Anaerobic bacteria break down remaining carbohydrates, producing acids, alcohols, and gases.
Skeletal Stage: In the final stage, only the most resistant materials, such as bones or woody structures, remain. These eventually break down through weathering and further decomposition.
What are the conditions for decay?
Oxygen: Most decay processes are aerobic, meaning they require oxygen. Microorganisms like bacteria and fungi use oxygen to break down organic matter. Without oxygen, decay slows down significantly or occurs through anaerobic processes, which are generally slower and produce different byproducts.
Temperature: Decay occurs fastest within a specific temperature range. Generally, warmer temperatures accelerate decay because they increase the metabolic activity of microorganisms and the rate than enzymes work at. However, extremely high temperatures can kill these microorganisms, halting decay. Very low temperatures also slow down decay by reducing microbial activity.
Moisture: Moisture is essential for decay because microorganisms need water to function. It also helps to dissolve and transport nutrients, making them accessible to decomposers. Too little moisture will inhibit decay, while excessive moisture can create anaerobic conditions, altering the decay process.
Why is decomposition useful for gardeners and farmers
Decomposition is useful for farmers and gardeners because it recycles nutrients, improves soil structure, and reduces the need for chemical fertilisers. Decomposed organic matter, also known as compost or humus, enriches the soil, providing essential elements for plant growth and promoting a healthy soil ecosystem.
Why does milk pH lower when decaying?
When milk decays, bacteria consume lactose and produce lactic acid. This lactic acid increases the concentration of hydrogen ions
in the milk, which lowers the pH. A lower pH indicates a more acidic environment.
