B4

• CYCLING OF MATERIALS:

  • It's likely that everyone has some carbon atoms in their body that were once inside Charles Darwin or Marie Curie, or any other individual that is now dead.
  • Atoms exist as part of different compounds and cycle between them through an ecosystem.
  • The materials cycle between the biotic and abiotic components of an ecosystem.
  • The biotic components are the living parts, such as plants, and the abiotic components are the non-living parts, such as the soil.
  • This cycling is seen in the elements carbon and nitrogen, and in the compound water.
• THE NITROGEN CYCLE:

  1. Nitrogen in soil is absorbed by plants which are then eaten by animals
  2. Animals release nitrogen through processes such as excretion and egestion
  3. Animal waste and dead animals are broken down by bacteria which returns nitrogen to the soil.
  4. Cow feeding on plant. Ammonia and nitrate in soil is absorbed by plant roots. Nitrogen in plant proteins. Ammonia and nitrate in soil is absorbed by plant roots.
  5.  Nitrogen in soil is absorbed by plants which are then eaten by animals
• THE NITROGEN CYCLE:

  • Many humans eat protein in the form of meat from other animals.
  • Our bodies break down this protein into its constituent parts, called amino acids.
  • These amino acids are used to make proteins inside our bodies, for example, in order to repair damaged tissue.
  • When we eventually die our proteins are broken down into the amino acid building blocks and often returned to the soil to be used by other living organisms, such as plants.
• IMPORTANCE OF MICROORGANISMS:

  • Decomposing bacteria and fungi are microorganisms that play an important role in breaking down dead organisms.
  • Microorganisms help return minerals and nutrients back to the environment so that the materials can then be used by other organisms.
  • As the bacteria and fungi decompose dead matter, they also respire and so release carbon dioxide to the environment, contributing to the carbon cycle.
• THE CARBON CYCLE:

  Every living organism has carbon compounds - such as fats and proteins - inside each of its cells.

  The carbon cycle shows how atoms of carbon can exist within different compounds at different times and be recycled between living organisms and the environment.
• THE CARBON CYCLE:

  1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
  2. Carbon dioxide is absorbed by producers in photosynthesis.
  3. Animals feed on plants, passing the carbon along the food chain. Most carbon they consume is exhaled during respiration. The animals and plants eventually die.
  4. Dead organisms are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide as fossil fuels in combustion.
  5. Overnight, CO2 from burning fuel (combustion) and respiration by cows, birds and plants pass into the atmosphere.
• THE CARBON CYCLE:

  The carbon cycle is easiest to understand in terms of its processes and how carbon is converted. The three key processes and the conversions are shown in the table below.

  A) Photosynthesis

  B) Glucose

  C) Carbon Dioxide

  
• THE CARBON CYCLE:

  1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
  2. Carbon dioxide is absorbed by producers in photosynthesis.
  3. Animals feed on the plant passing the carbon compounds along the food chain. The carbon they consume is exhaled as carbon dioxide formed during aerobic respiration. The animals and plants eventually die.
  4. Decomposers break down the dead organisms and return the carbon in their bodies to the atmosphere as carbon dioxide by respiration. Animals are used later as fossil fuels
• THE WATER CYCLE:

  Water is a key compound for life on Earth.

  Water is important for:

  • maintaining habitats
  • allowing nutrients to flow between organisms and the environment
  • survival of organisms

  Some organisms can survive in a dormant state without water for long periods of time, but all organisms will quickly or eventually die without it
• THE WATER CYCLE:

  A) Evapouration

  B) Condensation

  C) Precipitation

  D) Transpiration

  E) Percolation

  
• WATER CYCLE:

  A) Evapouration

  B) gas to liquid

  C) winds

  D) Precipitation

  E) Infiltration

  F) Transpiration

  
• DECOMPOSITION:

  • Decomposition is the breakdown of dead matter, often also called rotting.
  • Decomposing bacteria and fungi are microorganisms that help the process of decomposition.
  • Decomposition is crucial to the cycling of elements, such as carbon, from one living organism to another.
  • The rate of decomposition 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), mass (decaying fruit and vegetables) or temperature (grass cuttings).
• FACTORS AFFECTING DECOMPOSITION:

  A) Temperature

  B) decomposition

  C) enzymes

  D) growth

  E) oxygen

  F) aerobic respiration

  G) anaerobic

  H) Water

  I) decay

  
• WHAT IS COMPOST?

  • Gardeners and farmers improve the quality of their soil by adding compost.
  • Compost is made from dead plants.
  • Once spread on the soil, compost is broken down into minerals by decomposing bacteria and fungi, as well as by other organisms, such as worms.
  • Adding compost helps to recycle minerals so that they are absorbed by new plants and used in growth.
  • Compost also improves the quality of soil by increasing aeration and water retention.
• CONDITIONS FOR COMPOST:

  Compost forms through decomposition.

  Gardeners often make compost in a compost heap or bin. To speed up the rate of decomposition the conditions inside are kept:

  1. Warm - compost bins are usually black, which absorbs heat. Heaps are often covered with an old piece of carpet to insulate the compost.
  2. Moist - water is added at regular intervals.
  3. Aerated - the compost is regularly 'turned' with a garden fork to mix up the contents, prevent the contents becoming compacted and to introduce oxygen.
• RATE OF CHANGE = CHANGE IN VALUE/ CHANGE IN TIME
• ABIOTIC FACTORS AFFECTING ORGANISMS

  Abiotic factors affecting the abundance and distribution of organisms

  The abundance is the number of organisms in an ecosystem. A community is all of the living organisms within a habitat. Communities are affected by abiotic factors. Abiotic factors are non-living.

  They include:

  • light intensity
  • temperature
  • moisture levels
  • pH of soil
• ABIOTIC FACTORS ON ORGANISMS

  LIGHT INTENSITY:

  Plants have evolved for optimum growth in bright sunlight.

  Cacti originally come from deserts, where they grow in bright sunlight. Other plants have evolved to grow in shade.

  Many orchids, which are also kept as houseplants, grow on trees in the rainforest and have evolved for optimum growth in darker conditions. If an orchid was put on a bright windowsill and a cactus in a dark corner of a room neither plant would grow well.
• ABIOTIC FACTORS ON ORGANISMS

  TEMPERATURE:

  Both animals and plants have evolved to grow healthily at their optimum temperatures. If you planted either a cactus or orchid houseplants outside in cold temperatures, they would die. Similarly, animals that have evolved to live at the North Pole, such as the polar bear, could not survive in warmer conditions.
• ABIOITC FACTORS ON ORGANISMS:

  MOISTURE LEVELS

  More people kill houseplants by overwatering than by underwatering them. Many plants cannot survive in waterlogged soils because there is little oxygen. The cells in their roots are unable to respire, meaning that the roots rot and the plant dies. Other plants, such as pitcher plants, grow best in bogs where the moisture levels are high. Soil moisture meters can accurately determine how wet an area is.
• ABIOITC FACTORS ON ORGANISM:

  PH OF SOIL

  The pH of soil can have a huge effect on the range of plants that are able to grow. Some plants, like azaleas, grow best in acidic soils and will quickly die if planted in alkaline soils. Others, like clematis, prefer alkaline soils. Some, like the hydrangea, can grow in both. These plants are unusual in that their flower colour changes in different soils. Just like universal indicator paper, hydrangea flowers are pink in acidic soils and blue in alkaline soils.
• BIOTIC FACTORS AFFECTING ORGANISMS:

  Communities of organisms are also affected by biotic factors, which are factors that are living.

  They include:

  • availability of food
  • the presence of new predators
  • competition between organisms
• FOOD AVAILABILITY:

  • All animals require food to live.
  • The availability of food is a major factor in how many animals live in an ecosystem.
  • Areas like rainforests, which have rich food supplies, have more species of life than other areas like deserts and the Polar regions, where there is less food.
• NEW PREDATORS:

  • The arrival of new predators in an ecosystem can have a devastating effect.
  • In balanced ecosystems predators and prey have evolved together.
  • Predators can catch enough prey to survive, but not enough to kill all their prey.
  • The arrival of a new predator can upset this balance.
  • An example of this is the introduction of the red fox to Australia, which has caused concern over their effect on native birds and small mammals.
  • Introducing new predators can cause a rapid decline in the numbers of prey, which then reduces the food supply for existing predators.
• OUT-COMPETITION:

  • The introduction of a new species into an ecosystem can result in it out-competing another native species.
  • Several hundred years ago grey squirrels were brought to England from North America by wealthy people and let free in their grounds.
  • The smaller native red squirrel couldn't compete with the newer, larger grey squirrel.
  • Grey squirrels are larger so they can store more fat and survive harsher winters. So the number of red squirrels and the places they live has reduced dramatically.
• ABIOTIC FACTORS:

  • Abiotic factors are non-living.
  • They include light intensity, temperature and moisture levels.
  • The community of living organisms in an ecosystem can be affected by abiotic factors.

  AFFECTS OF ABIOTIC FACTORS ON ECOSYSTEMS:

  • A shingle beach has small stones instead of fine sand because of the wave types. The wave type is an abiotic factor.
• BIOTIC FACTORS:

  • Biotic factors are living.
  • The community of living organisms in an ecosystem can be affected by abiotic factors.

  EFFECT OF BIOTIC FACTORS ON ECOSYSTEMS:

  • A stronger species will live for longer and out-compete the other species (grey squirrels and red squirrels in the UK)
• COMPETITION:

  Within an ecosystem there are many communities of different organisms. Each of the organisms is trying to survive in the ecosystem.

  Animals must get access to:

  • food
  • water
  • space (territory)

  Plants need access to:

  • sunlight for photosynthesis
  • water
  • mineral salts
  • space
• COMPETITION:

  • All of the communities of organisms within the ecosystem compete for resources that they need to survive.
  • There are only a set amount of resources in an ecosystem.
  • If an organism cannot access the resources that it needs to survive, then it will die.
  • Animals can try moving to another habitat to find more resources, but plants cannot move to another location.
  • Changes to the numbers of organisms could be due to a change in the abiotic factors, like water or sunlight, or biotic factors, like a new predator or pathogen.
• OUT-COMPETE:

  The introduction of a new species into an ecosystem can result in it out-competing another native species.
• INTERDEPENDENCE:

  • Organisms in an ecosystem rely on each other for their survival. This relationship is called interdependence.
  • When organisms interact with one another it affects their survival.
  • This becomes obvious when studying predator-prey cycles, mutualistic relationships and parasitism.
• PREDATOR- PREY RELATIONSHIP:

  Predator-prey cycles:

  1. There are always more prey than predators.
  2. The number of predators increases because there are more prey, so there is more food for them to eat.
  3. The number of prey reduces because there are more predators, so more get eaten.
  4. The number of predators reduces because there is less prey, so less food.

  There is interdependence between the predator and the prey. Any change in numbers of prey affects the numbers of predators and vice versa. In a healthy, balanced ecosystem the numbers of predators and prey remain fairly constant.
• MUTALISM:

  Some organisms rely on the presence of organisms of a different species. This is an example of mutualism.

  Other examples of mutualism:

  • Lichens - formed by algae and fungi living together. Algae can photosynthesise and make food, which is shared by the fungus. The fungus in turn shelters the algae from a harsh climate.
  • Leguminous plants - peas, beans and clover have colonies of nitrogen-fixing bacteria in nodules attached to their roots. The plants gain nirogen-containing compounds from the bacteria, and the bacteria gain sugars from the plants.
• PARASITISM

  Parasites are organisms that live on or in a host organism. The parasite benefits from this arrangement, but the host suffers as a result. Parasites do not usually kill the host because this would cut off their food supply.

  Examples:

  • Fleas suck blood
  • Tapeworm absorb food.
  • Headlice feed off blood.
  • Mistletoe absorb nutrients and minerals.
• TROPHIC LEVELS:

  A simple food chain is:

  algae → mosquito larvae → dragon fly larvae → perch

  All other food chains in an ecosystem can be added together to make a food web. These stages in a food chain or web are called trophic levels.
• FOOD CHAIN:

  • Producer- bottom of the food chain. A plant or algae which can photosynthesise to convert carbon dioxide and water into glucose. This provides all the biomass for the food chain. Algae are the producers in the food chain above.
  • Herbivore- cannot make their own food. The second trophic level in all food chains is a herbivore or omnivore called a primary consumer.
  • Carnivore- eats the primary consumer. This is called the secondary consumer.
  • Apex predator- Organisms at the top of a food chain have no predators.
• KEY TERMS- ECOSYSTEMS:

  A) Producers

  B) Primary

  C) Secondary

  D) Predator

  E) Prey

  F) Decomposers

  
• BIOMASS:

  • Biomass is tissue from living organisms.
  • The mass of your body is biomass because you are alive.
  • Wood is considered biomass because it was recently a plant.
  • Fossil fuels are not considered biomass because they are the remains of organisms that died millions of years ago and have been chemically changed from the original living tissue.
• PYRAMIDS OF BIOMASS:

  • We can measure the amount of biomass at different trophic levels in a food chain.
  • The total biomass of each trophic level is often represented as a modified bar chart called a pyramid of biomass. In a food chain from a healthy ecosystem the biomass at each trophic level must reduce.
  • An example of a food chain is:

  clover → snail → thrush → sparrowhawks

  • Pyramids of biomass should always be perfectly shaped as a pyramid. If this is not the case, then the ecosystem is likely to be unhealthy and in danger.
• PYRAMIDS OF BIOMASS:

  Pyramids of biomass must be drawn with the:

  1. bars equally spaced around the midpoint
  2. bars touching
  3. bar for the producer at the bottom
  4. length of each bar proportional to the amount of biomass available at each trophic level