NATIONAL 5 ENVIRONMENTAL SCIENCE

Transcription

1 NATIONAL 5 ENVIRONMENTAL SCIENCE Unit 1: Living Environment Revision Notes

2 ECOSYSTEMS 2 Main definitions: Species - creatures which can breed successfully and produce offspring Population - a group of organisms of one species Habitat - a place where an organism lives Community - all of the animas and plants that live together in an ecosystem. Ecosystem - the community and the habitat together. It can also be described as all of the living things together with the non living environment Niche - is the role occupied by an organism in a habitat - what it eats, what preys on it and where it lives (e.g. tree bark, freshwater pond) Competition - a negative interaction which occurs between species whenever there is demand for a limited resource e.g. food, water Biodiversity - the variety of life that exists within an ecosystem Biotic factor - a living feature of an ecosystem, such as the food supply, disease and predation Abiotic factor - a non-living feature of an ecosystem, such as ph, light intensity, rainfall, temperature, wind speed and wind direction Adaptation - any feature which makes an organism well suited to its environment e.g. thick coat, camouflage Interdependence - when two or more organisms rely on each other for survival

3 FOOD CHAINS & FOOD WEBS 3 The source of energy for a food chain / web is always the sun. A food chain shows the relationship between organisms which pass on their energy by feeding The arrows in a food chain indicate the direction of energy flow e.g. oak tree leaf-eating insect shrew fox A food web shows all the possible feeding relationships in an ecosystem or habitat. The owl is the top predator in this food web A consumer means an animal which depends on other living things (plants or other animals) for its food. Primary consumers are herbivores that eat the producers Secondary consumers are animals that eat the primary consumers. Tertiary consumers eat secondary consumers. They are carnivores that only eat other animal material Omnivores (can be primary and secondary consumers) eat both plants and animals All green plants are producers. They convert light (solar) energy into chemical energy (sugars) through the process of photosynthesis. Energy is lost within food webs and chains. Usually only about 10% of the energy from prey is passed on to a predator. This means there are far fewer predators than their prey. Energy is lost due to: Heat Movement Undigested waste (e.g. bones). species But not from faeces as this is food for other Decomposers are important in recycling nutrients in food webs. These are bacteria and fungi which break down dead material chemically Detritivores are animals which feed on and get their energy from dead material or organic matter. Examples include wood louse, earthworms and maggots.

4 4 THE CARBON CYCLE The carbon cycle describes the movement of carbon atoms between the atmosphere, the oceans and rivers, rock and all living material The main processes in the carbon cycle are photosynthesis, respiration and decomposition. carnivore herbivore Photosynthesis is essential for converting solar energy and CO2 into sugars: carbon dioxide + water + light energy glucose + oxygen Respiration converts the sugars, with oxygen into energy which all organisms need glucose + oxygen carbon dioxide + oxygen + energy Humans also contribute to the carbon cycle by burning fossil fuels such as coal and oil which produces carbon dioxide.

5 THE NITROGEN CYCLE 5 The nitrogen cycle describes the movement of nitrogen atoms within nature, between the atmosphere, living things and the soil. Nitrogen is required by living things for amino acids, proteins (for muscles and movement) and for our DNA. Although nitrogen makes up around 80% of the atmosphere, it cannot be easily absorbed by plants or animals. It must go through a number of process before it can be absorbed by plant roots. Bacteria play a very important role in this. Nitrogen-fixing bacteria found in both the soil and roots of leguminous plants (such as peas and clover) fix nitrogen from the air into a form that can be used by plants, called ammonium. However ammonium is harmful to plants in large amounts Chemical reactions by other bacteria add oxygen to the ammonium producing first nitrites, then nitrates. These can be absorbed by plant roots and the plant gets the nitrogen it needs. Consumers (herbivores) then eat these plants to get the nitrogen they need Secondary consumers (carnivores) then eat these animals to get the nitrogen they need and so on; the nitrogen is passed up the food chain. When an organism dies or passes waste (urine and faeces), decomposers can break down this material and convert it into ammonium or back to nitrogen gas, returning it to the nitrogen cycle.

6 BIODIVERSITY 6 Biodiversity is the range of life forms within an ecosystem and also the variety within individual species. The greater the biodiversity, the healthier the ecosystem. Humans rely on biodiversity for our food (plant and animals), resources such as wood, soil and a number of services which living things do e.g. insects pollinating crops; bacteria breaking down sewage. Biodiversity can be affected by living and non-living things: Abiotic Factors Non Living components include: Temperature Humidity Sunlight Oxygen concentration ph Moisture content Biotic Factors Living components include: Relationship between predators and prey Competition Invasive or naturalised species (e.g. grey squirrel, rhododendron) Disease INDICATOR SPECIES Indicator Species are species which show the health of the ecosystem or the presence / absence of one abiotic factor. Examples include: Lichens which show levels of air pollution (sulphur dioxide). Bushy lichens need really clean air whereas crusty lichens can survive in more polluted air (near factories and busy roads). Freshwater invertebrates - in rivers and streams there are small insects which live under the stones in the river bed. Stonefly nymphs like clean water with plenty of oxygen. Rat-tailed maggots prefer dirty, polluted water, which lack oxygen e.g. sewage pollution Birds of prey. If birds of prey are present it suggests the ecosystem is quite healthy as there is plenty of food for the top predators.

7 HUMAN IMPACT ON BIODIVERSITY 7 Human activities which impact on biodiversity include: Problem Causes Problems Acid Rain Climate Change Deforestation Burning of fossil fuels (in power stations and in transport) produces sulphur dioxide (SO 2 ) and nitrogen oxides (NO X ) which dissolve in rain CO 2 from burning fossil fuels (power stations, vehicles) Methane from livestock CFCs from fridge units Produce less emissions than coal Deforestation Clearance of rainforest for cattle ranching, mining, dams and hardwood logging Damages trees Lakes and rivers become acidic and fish die off Possible sea level rise (as oceans expand and ice on land melts) Loss of habitat e.g. ice for polar bear to hunt Ranges of species change - cold favouring species forced to move out as climate works More storms and heavy rain more flooding Impact on global climate (leads to global warming) Loss of habitats / biodiversity Desertification Pollution of Lakes and Seas Overfishing Farming Problems Overgrazing and deforestation as popualtin increases Soil dries up, blown away Farming waste (nitrogen run off) Industrial Waste Oil spills Factory fishing trawlers can take huge catches from sea Rising demand for fish e.g. cod, mackerel Removal of hedgerows to make space for machines Pond s drained Use of chemicals Increased soil erosion Dust storms as soil dries out Drought increases Toxic for wildlife (e.g. plastic beads which species eat) Oil spills smother wildlife e.g. seabirds Falling fish stocks Possibility of extinction, populations take much longer to replenish Habitat loss - decline in farmland birds as ponds and hedges removed Excess fertilisers can cause algal blooms which absorb oxygen from rivers and streams (eutrophication) Pesticides can kill other creatures they don t intend to (non-selective) e.g. insects required to pollinate crops

8 NON NATIVE SPECIES 8 A non-native species is a species introduced through human action (both accidental and deliberate) outside its native range An invasive non-native species (INNS) is a non-native species which has the ability to spread and cause damage to the environment, the economy or the way we live Examples include: Non-native species Grey Squirrel Rhododendron Ponticum CONFLICTS Problems Caused Introduced from North America in the 1800s: Out competes native red squirrel for food Carries Red squirrel numbers in steep decline Flowering shrub introduced from Asia in the 1800s: Spreads quickly through it tubers/roots Nothing grows underneath it (blocks out light) Solutions Trapping (but estimate 2 million greys across Britain) Introducing sterile males into grey population so they don t breed untested Captive breeding of red squirrels to boost population Cutting back and burning (but this pollutes atmosphere) Using herbicides / weedkillers - but shrub is becoming more resistant to these and these are expensive Conflicts arise where two competing land users disagree. An example is the disagreement between environmental groups e.g. RSPB and the Forestry Commission who plant trees to produce wood across much of Northern Scotland Conflict Forestry Commission plants nonnative trees e.g. Sitka Spruce (from Canada) which don t suit local wildlife Nothing grows on forest floor as trees block out the light Pine needles turn the soil and river acidic which can kill off fish Large square blocks of forest don t look natural Mesh fences to keep deer out (eat samplings) threaten low flying birds Solutions / Strategies Plant along contours to make appear more natural Plat more native species e.g. oak, Scots pine, birch Pout up squirrel, bird and bat boxes to encourage native wildlife Use plastic tubing to protect young trees from being eaten by deer instead of fences Regular meetings between forestry and environmental groups - now work together to achieve aims

9 CONSERVATION 9 Conservation is the regulation of wild animals and plants (and their habitats) in order for them to be able to survive and continue as species in the wild. A number of species in Scotland are threatened with extinction e.g. Red squirrel - threatened by invasive species (grey squirrel carries disease) Scottish wildcat - threatened by habitat loss (native pine forest) and breeding with domestic cats Ptarmigan - mountain grouse threatened by climate change (global warming) Conservation in Scotland There are a number of ways in which animals and habitats are conserved in Scotland. These are shown below Method Role SNH SEPA SSSI Scottish Natural Heritage is the most important organisation in Scotland dealing with conservation. It is public body, which gets taxpayers money What does SNH do? Has species action lists for 32 of Scotland s threatened species e.g. red squirrel, capercaillie Removal of introduced species (crayfish, mink) Educate the public on the wildlife (website and publications) Manages Scotland s deer population (culls if required) Looks after areas of conservation designated for their scenery or wildlife importance e.g. National Nature Reserves and SSSIs. The Scottish Environmental Protection Agency is also a government organisation: monitors pollution levels in land, water and atmosphere. deals with waste reduction and landfill and can fine polluters for breaking laws Sites of Special Scientific Interest. There are over 1400 in Scotland and some of these are very small, and attempt to protect animals, plants or the geology of an area: SSSIs are protected by law. It is an offence for any person to intentionally or recklessly damage the protected natural features of an SSSI. Must gain special permission before developing these areas

10 SAMPLING METHODS IN ECOSYSTEMS 10 Methods of sampling will depend upon the ecosystem under investigation: Ecosystem Sampling Equipment & Method Technique Improving Results Tree Beating Stick & Tray A walking stick is used to give the branch of a tree a few taps. Invertebrates fall on to a a collecting tray or sheet underneath. Soil Pitfall Trap Animals the are active on the soil surface and leaf litter fall into the trap (a sunken beaker). Pitfall traps should be placed at random or at regular intervals across the area of survey Pond / Stream Vegetation / Plants Pond Net Quadrat (type of grid usually with 100 squares) In ponds the net is moved rapidly through the water, catching animals which are quickly transferred to screw top jars. In streams the net is held at a fixed position and invertebrates in the stream bed can be dislodged by kicking the pebbles. Randomly position a quadrat and count the plant types (or ground cover) in each square Take several samples from different branches of the same tree Use a large tray with raised edges to stop other insects crawling in to the trap Set up several traps Disguise the opening with a leaf or stone Check traps regularly or put preservative liquid in the beakers Choose a net with finer mesh to catch smaller invertebrates Repeat the procedure many times to increase reliability Repeat the procedure many times Random sampling is important to eliminate the human factor, to prevent selection of one particular species and to reduce bias in a technique Sampling should also be repeated (at different times or by different groups) to allow averages to be used. This helps to eliminate anomalies, reduce errors and improve the reliability of experiments and techniques.

11 MEASURING ABIOTIC FACTORS Abiotic Factor Sampling Method Temperature (soil/water) Soil moisture Thermometer. Soil moisture probe Improving Results Repeat and average to boost reliability Ensure probes of equipment are clean before use to avoid inaccurate readings Soil ph Soil ph meter Ensure probes of equipment are clean Light levels Use a light meter Light meters are difficult to use (change in cloud cover, shadows) so repeat/average Oxygen concentration Flow rate (stream discharge) Wind speed / direction Colorimetric methods (react with O 2 in water to give colour change) Use a flow meter Calculate size or river channel (depth x width) and multiply by speed (timing object e.g. a float to move 5 metres) Speed is measured by an anemometer and direction by a wind vane Repeat and average Ensure sampler does not stand in front of the flow meter to reduce (shelter) readings Use an object that is heavy enough to move Repeat and average (floats can get stuck behind stones when river levels are low) Need to be located in an area which is not sheltered Rainfall Rain gauge Empty same time each day Repeat and average All measurements have the potential to introduce error, all equipment should be properly maintained, calibrated and used appropriately Estimating Population Size The capture-mark-recapture technique can be used to estimate the size of a population: animals are trapped, e.g. using pitfall traps they are marked in a harmless way and then released traps are used again a few days later the numbers of marked and unmarked animals caught in the traps are recorded the population size is estimated using an equation:

12 USING KEYS 12 Keys are methods used to identify a species. A key can be branching or a series of paired statements with simple 'yes / no' answers. 1. Branching Tree Example This tree could help you identify a new vertebrate. For example, if it had no fur or feathers and dry skin, you would follow the right-hand pathway at the first and second junctions, but the lefthand pathway at the third junction. This would lead you to identify the animal as a reptile. 2. Paired Statement Keys Paired statement keys can also be used to identify organisms e.g. Question 1 Are the leaves like needles? Yes? go to question 2 No? go to question 3 Question 2 Are the needles in pairs? Yes? go to question 4 No? go to question 5 Question 3 Are the leaves simple or compound (several leaflets)? Yes? go to question 6 No? go to question 7 Question 4 It could be a Scots Pine. [Start again.] Question 5 Are the needles in circular clusters? Question 6 Is the leaf heart-shaped?