7.2 Organisation of an ecosystem Flashcards
Producers
Photosynthetic organisms are the producers of biomass for life on Earth.
They produce their own food using energy from the Sun.
A producer has the following characteristics:
They are at the start of every food chain (the first trophic level, which is always the biggest).
They can photosynthesise (producers are normally green plants or algae).
They make glucose by photosynthesis.
They use this glucose to produce other biological molecules, which then make up the producer’s biomass (some of the glucose produced is also used in respiration to release energy for the cell).
In extreme environments (such as underwater volcanic vents) the producers are not photoautotrophs but chemoautotrophs who produce organic molecules without using energy from the Sun).
Food chains
A simple way to show the feeding interactions between the organisms in a community is with a food chain
1. Producer: food chains always begin with a producer.
2. Primary consumer: producers are eaten by primary consumers (herbivores/omnivores).
3. Secondary consumer: primary consumers are eaten by secondary
consumers (carnivores/omnivores).
4. Tertiary consumer: secondary consumers are eaten by tertiary consumers (carnivores/omnivores).
A food chain shows the transfer of energy from one organism to the next.
The source of all energy in a food chain is light energy from the Sun.
The arrows in a food chain show the transfer of energy from one level of the food chain to the next.
Investigating ecosystems
Ecology is the branch of biology that studies the distribution and abundance of species, the interactions between species, and the interactions between species and their abiotic environment.
Ecologists are biologists that study these interactions by investigating ecosystems.
Quadrants and transects
They are used by ecologists to measure the distribution and abundance of species in an ecosystem.
Practical 9 (ecosystems)
Aim: To measure the population size of a common species in a habitat and use sampling techniques to investigate the effect of a factor on the distribution of this species.
Procedure - Use a quadrat to estimate the population size of a plant species in a survey area.
Use a transect line and a quadrat to investigate the effect of a factor on the number of plants in a survey area.
Recycling in an ecosystem
Many different materials cycle through the abiotic and biotic components of an ecosystem.
All materials in the living world are recycled to provide the building blocks for future organisms.
Carbon cycle
Elements such as carbon are not endless resources.
There is a finite amount of each element on the planet.
Elements need to be recycled in order to allow new organisms to be made and grow.
Process of carbon cycle
Carbon is taken out of the atmosphere in the form of carbon dioxide by plants and algae during photosynthesis (the carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins - biomass - within plants and algae).
This carbon is passed on to animals (and microorganisms) when they feed on plants and algae.
It is returned to the atmosphere in the form of carbon dioxide, during respiration by plants, animals and microorganisms (that release COz during decomposition).
If animals and plants die in conditions where decomposing
microorganisms are not present, the carbon in their bodies can be converted, over millions of years and significant pressure, into fossil fuels.
When wood or fossil fuels are burned (a process is known as combusti the carbon within them combines with oxygen and carbon dioxide is released into the atmosphere.
Water cycle
The water cycle provides fresh water for plants and animals on land before draining into the seas.
Water is continuously evaporated and precipitated.
Water molecules move between various locations - such as rivers, oceans and the atmosphere - by specific processes:
Water enters the atmosphere as water vapour in one of two processes.
Energy from the Sun heats the Earth’s surface and water evaporates from oceans, rivers and lakes.
Transpiration from plants releases water vapour into the air.
The warmer air of the lower atmosphere rises, taking the water vapour with it.
The moist air cools down as it rises.
Water vapour condenses back into liquid water, forming clouds.
Water returns to Earth in the form of precipitation.
As the water droplets in the cloud get bigger and heavier, they begin to fall as rain, snow and sleet.
Role of microorganisms
Microorganisms play a vital role in cycling material through an
ecosystem; they return carbon to the atmosphere as carbon dioxide and mineralions to the soil.
When living organisms produce waste products or organisms die, the waste products and dead organisms are broken down (digested) by microorganisms known as decomposers.
Bacteria and fungi are the main groups of decomposers.
Decomposition (also known as decay) is the process by which waste products or dead organisms are broken down and the materials they contain (such as carbon and mineral ions such as iron, magnesium and nitrates) are returned to the environment.
When decomposing microorganisms respire, carbon is returned to the atmosphere in th form of carbon dioxide.
Rate the of decay
Decomposition (also known as decay or rotting) is the breaking down and digestion of biological material (waste products and dead organisms) by organisms called decomposers.
Decomposers include microorganisms (bacteria and fungi) and detritus feeders.
Decomposition is a crucial process as it ensures that materials such as carbon and mineral ions are recycled and returned to the environment.
The rate of decay is the speed that decomposers break down biological material and is affected by three key factors.
Practical 10 (decay)
Aim: To investigate the effect of temperature on the rate of decay of fresh milk by measuring pH change.
Procedure - Decide on the range of temperatures that you wish to investigate milk decay over, considering the lesson time you have.
Use an indicator to monitor the rate of decay of milk.
Changing environments
Environmental change (often as a result of human activity) can affect the distribution of species within ecosystems.
A change in distribution means a change in where an organism lives.
Some changing environmental factors that can affect the distribution of organisms include:
Temperature
Availability of water
Composition of atmospheric gases
These changes may be seasonal, geographic or caused by human interaction.
Effects on distribution
Temperature - Organisms have adaptations that enable them to survive within a certain temperature range.
As climate change occurs and average temperatures rise, the distribution of species is changing.
Availability of water - All organisms require water to survive, either directly (water is essential for the biological processes that sustain living organisms) or indirectly (water may provide a habitat for species and is essential for the growth of plants that support whole food chains and food webs).
Composition of atmospheric gases - There are many ways in which the distribution of organisms can be affected by atmospheric gases:
Oxygen is required for aerobic respiration in plants and animals.
Some aquatic animals (such as fish) can only survive in water with high oxygen concentrations.
Carbon dioxide is required for photosynthesis in plants (CO2 concentration affects the rate of photosynthesis).
Some species are very sensitive to air pollution.
Importance of decomposition
The two main groups of decomposers are bacteria and fungi.
Decomposers carry out a very important function in ecosystems - they break down dead plant and animal material.
They do this by:
Secreting digestive enzymes onto the surface of the dead organism.
These enzymes break down the dead matter into small soluble food molecules.
These molecules are then absorbed by the decomposers.
This process of decomposition also helps to release organic nutrients back into the environment (eg. the soil) which are essential for the growth of plants (producers).
Factors affecting rate of decay
Temperature - at warmer temperatures, enzymes involved in decomposition can work at a faster rate increasing the rate of decay. If the temperature is too high then the enzymes will denature and rate of decay will decrease. At low temperatures the enzymes have less kinetic energy and the rate of decay is lower.
Water - decomposers require water to survive. Many decomposers also function by secreting enzymes on to decaying biological matter and absorbing the products of the chemical digestion. As water availability increases the rate of reaction also increases.
Availability of oxygen - oxygen is needed by many composers for aerobic respiration. For these decomposers the rate of decay increases as oxygen availability increases. However some microorganisms can respire anaerobically resulting in anaerobic decay.
Compost
Gardeners and farmers try to provide optimum conditions (warmth, moisture and an oxygen supply) for rapid decay of waste biological material.
The compost produced is used as a natural fertiliser for growing garden plants or crops.
Once the compost is spread onto the soil, it is broken down further by decomposing microorganisms (bacteria and fungi) and detritivores (eg. earthworms and woodlice).
This ensures the recycling of minerals (such as magnesium and nitrates) that can then be absorbed by plants to be used for growth (magnesium is used to make chlorophyll, nitrates to make amino acids).
Biogas generator
Some decomposing microorganisms can break down biological material without oxygen.
This is called anaerobic decay.
Anaerobic decay produces methane gas (as well as carbon dioxide) – together these products are given the term ‘biogas’
The methane produced can be burned as a fuel.
Biogas generators are large containers in which animal or plant waste is allowed to decay anaerobically.
