Note by , created almost 6 years ago

GCSE Biology Core Note on Inter-relationships, created by daniifarrell on 01/02/2014.

Created by daniifarrell almost 6 years ago
The Nervous stystem
Organic Chemistry
Megan Tarbuck
American West GCSE History Revision
Jasmine Box
The Nervous System
Control in plants
Variation and Genes
Disease and Cure

Page 1

Antiseptics and antibiotics   Bacteria can become resistant to antibiotic due to bacteria mutating. If you have an infection some of the bacteria is resistant to antibiotic so only the non-resistant strains of bacteria will be killed. The individual resistant bacteria will reproduce and the population of the resistant strain will increase; natural selection.  The resistant strain can cause a serious infection that cannot be treated by antibiotics. E.g MRSA causes serious wound infections and is resistant to the powerful antibiotic Methicillin.   Practical to investigate Pour hot sterilised agar jelly into a sterile petri dish, when the jelly is set transfer bacteria to the culture medium. Then take three paper discs; soak one in antibiotic, another in different antibiotic and the third in sterile water. Place the discs in the jelly and tape the lid. Leave the dish for 24 hours at 25 degrees. Look at the results, anywhere the bacteria can’t grow is called an “inhibition zone” the bigger the inhibition zones around the disc, the more effective the antibiotics. The control variables for this experiment include; Temperature, size of the discs, concentration  of the antibiotics.

Energy and biomassEnergy from the sun is the source for nearly all life on earth. Plants convert a small percent of the light into glucose. The rabbit then eats the plant and uses up some of its energy and some is stored in its body. The fox then eats the rabbit and gets the energy stored in its body.Energy is used to stay alive i.e in respiration which powers all life processes, including movement. A lot of energy is lost through heat. The energy is said to be lost in the animals in the food chain can’t use it. After four or five trophic levels too much energy has been lost to support more organisms.

Parasitism and mutualism Parasites live in or on a host; they take what they need to survive, with out giving anything back, this often harms the host.  Fleas- fleas are insects that live in the fur and bedding of animals, including humans. They feed by sucking blood and can reproduce quickly. Head Lice- live on human scalps sucking blood. Tapeworms- attach to the intestinal wall of their hosts and absorb the nutrients causing them to suffer from malnutrition. Mistletoe- parasitic plant that grows on trees and shrubs, absorbs water and nutrients which can reduce the host’s growth.Both organisms gain from a mutualistic relationship.Oxpeckers- birds that live on the backs of buffalo. Eat pests on the buffalo like ticks, flies and maggots but they also alert the animal to any predators that are near by hissing.Cleaner fish- eat dead skin and parasites off large fish. In return they get a source of food and avoid being eaten by the big fish.Nitrogen-fixing bacteria in legumes- most plants have to rely on nitrogen-fixing bacteria in the soil to get the nitrates that they need. Leguminous plants beans, peas, clover etc, carry the bacteria in nodules in their roots. The bacteria can get a constant supply of sugar from the plant, and the plant get essential nitrates.

Potential problems of larger population: Raw materials including non-renewable energy resources, are rapidly being used up. More waste More pollutants being produced including phosphates, nitrates and sulphur dioxide (sulphur dioxide forms acid rain which can lower the ph of soil and lakes an can destroy habitats.   Fertilier contains nitrates essential to modern farming. Without them crops wouldn’t grow nearly so well and food yields would be well down because crops take nitrates out of the soil that need to be replaced. If too much fertiliser is applied it finds it way into river, lake and seas; this results in eutrophication- too many nitrates in the water. Rapid growth in algae- some plants start dying due to competition for light- microbe numbers increase as they feed on the dead material- microbe use up all the oxygen. Fish and other aquatic animals suffocate. Experiment – Set up one jam jar with moist cotton wool, soaked in water, and 20 cress seeds on top- this is the control Set up on a second jar in the same way, but with the cotton wool soaked in a solution of pollutant, e.g nitrate Seal jar After 5-7 days, measure the length of the shoots and work out the average shoot length for each jar. The results will depend on the pollutant used. E.g nitrate will cause increased plant growth compared to control. Make sure the following variable are controlled- temperature, amount of light, volume of solution that cotton wool absorbs, number of seeds and type.

Recycling No recycling means; More waste More land used for landfill. Some waste is toxic More materials have to be manufactured or extracted to make new products- using up more resource and energy. Recyclable materials cause: Metal are extracted from ores e.g. aluminium is extracted from bauxite. There’s a limited amount of metal ore. Mining and extracting metals takes energy most of which comes from fossil fuels. Paper is produced by wood so fewer trees cut down. Prevents deforestation, recycling paper uses 28%-70% less energy Plastics are made from crude oil- so recycling conserves oil resources. Plastics are slow decomposers. Problems with recycling: Still uses energy Waste materials can be difficult and time consuming to sort. Expensive Quality of recycled goods isn’t good 100 million tons of domestic and commercial waste a year New law in the uk and eu to increase recycling. Eg by 2015 cars will be made by 95% recyclable material.

Some organisms are very sensitive to change and can show the effect of human activity- indicator species.Water pollution If raw sewage or other pollutants containing nitrates are released into a river, the bacterial population in the water increases and uses  up the oxygen Invertebrate animals like stonefly larvae and fresh water shrimps are sensitive to the concentration of dissolved oxygen. If you find stonefly larvae in a river it indicates that the water is clean. Other invertebrates have adapted to polluted conditions, e.g. blood worms and sludgeworms indicate a high level of pollution. Air pollution Can be monitored by looking at particular types of lichen that are sensitive to concentration of sulphur dioxide in the atmosphere (level of pollution from car exhausts, power stations etc.) Blackspot fungus is found on rose leaves, its presence indicates clean air  Non living indicators Dissolved oxygen meters and chemical tests are used to measure the concentration of dissolved oxygen in water to show how the level of water pollution is changing. Electronic meters and various lab tests are also used to measure the concentration of sulphur dioxide in air to show air pollution changing.

Antiseptics and antibiotics

Energy and Biomass


larger pop & recycling

living indicators