NATIONAL 5

ENVIRONMENTAL SCIENCE

Unit 1: Living Environment

Revision Notes

ECOSYSTEMS

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

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• A food web shows all the possible feeding relationships in an ecosystem or habitat.

FOOD CHAINS & FOOD WEBS

• 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

All green plants are producers. They convert light (solar) energy intochemical energy (sugars) through the process of photosynthesis.

A consumer means an animal whichdepends on other living things (plantsor other animals) for its food.

• Primary consumers are herbivoresthat eat the producers

• Secondary consumers are animalsthat eat the primary consumers.

• Tertiary consumers eat secondaryconsumers. They are carnivores thatonly eat other animal material

• Omnivores (can be primary andsecondary consumers) eat both plantsand animals

The owl is the top predator in this food web

Energy is “lost” within food webs and chains. Usually only about 10% of the energyfrom prey is passed on to a predator. This means there are far fewer predators thantheir prey. Energy is lost due to:

• Heat• Movement• Undigested waste (e.g. bones). But not from faeces as this is food for other

species

Decomposers are important in recycling nutrients in food webs. These are bacteriaand fungi which break down dead material chemically

Detritivores are animals which feed on and get their energy from dead material ororganic matter. Examples include wood louse, earthworms and maggots.

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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 anddecomposition.

Humans also contribute to the carbon cycle by burning fossil fuels such as coal andoil which produces carbon dioxide.

Photosynthesis is essential for converting solar energy and CO2 into sugars:

Respiration converts the sugars, with oxygen into energy which all organisms need

carbon dioxide + water + light energy glucose + oxygen

glucose + oxygen carbon dioxide + oxygen + energy

herbivore

carnivore

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THE NITROGEN CYCLE

The nitrogen cycle describes the movement of nitrogen atoms within nature, betweenthe atmosphere, living things and the soil. Nitrogen is required by living things foramino acids, proteins (for muscles and movement) and for our DNA.

Although nitrogen makes up around 80% of the atmosphere, it cannot be easilyabsorbed by plants or animals. It must go through a number of process before it canbe 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 aspeas 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 firstnitrites, then nitrates. These can be absorbed by plant roots and the plant gets thenitrogen 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 theyneed and so on; the nitrogen is passed up the food chain.

When an organism dies or passes waste (urine and faeces), decomposers can breakdown this material and convert it into ammonium or back to nitrogen gas, returning itto the nitrogen cycle.

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BIODIVERSITY

Biodiversity is the range of life forms within an ecosystem and also the variety withinindividual species. The greater the biodiversity, the healthier the ecosystem.

Humans rely on biodiversity for our food (plant and animals), resources such aswood, soil and a number of “services” which living things do e.g. insects pollinatingcrops; bacteria breaking down sewage.

Biodiversity can be affected by living and non-living things:

INDICATOR SPECIESIndicator Species are species which show the health of the ecosystem or thepresence / absence of one abiotic factor. Examples include:

• Lichens which show levels of air pollution (sulphur dioxide). Bushy lichens needreally clean air whereas crusty lichens can survive in more polluted air (nearfactories and busy roads).

• Freshwater invertebrates - in rivers and streams there are small insects whichlive under the stones in the river bed. Stonefly nymphs like clean water with plentyof 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 quitehealthy as there is plenty of food for the top predators.

Abiotic Factors Biotic FactorsNon Living components include:

• Temperature• Humidity• Sunlight• Oxygen concentration• pH• Moisture content

Living components include:

• Relationship between predators and prey

• Competition• Invasive or naturalised species (e.g.

grey squirrel, rhododendron)• Disease

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HUMAN IMPACT ON BIODIVERSITY

Human activities which impact on biodiversity include:

Problem Causes Problems Acid Rain Burning of fossil fuels (in

power stations and in transport) produces sulphur dioxide (SO2) and nitrogen oxides (NOX) which dissolve in rain

• Damages trees• Lakes and rivers become acidic and fish die off

Climate Change

• CO2 from burning fossil fuels (power stations, vehicles)

• Methane from livestock• CFCs from fridge units• Produce less emissions than coal

• Deforestation

• 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

Deforestation • Clearance of rainforest for cattle ranching, mining, dams and hardwood logging

• Impact on global climate (leads to global warming)

• Loss of habitats / biodiversity

Desertification • Overgrazing and deforestation as popualtinincreases

• Soil dries up, blown away

• Increased soil erosion• Dust storms as soil dries out• Drought increases

Pollution of Lakes and Seas

• Farming waste (nitrogen run off)

• Industrial Waste • Oil spills

• Toxic for wildlife (e.g. plastic beads which species eat)

• Oil spills smother wildlife e.g. seabirds

Overfishing • “Factory fishing” trawlers can take huge catches from sea

• Rising demand for fish e.g. cod, mackerel

• Falling fish stocks• Possibility of extinction, populations take much longer to replenish

Farming Problems

• Removal of hedgerows to make space for machines

• Pond s drained• Use of chemicals

• 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

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8NON NATIVE SPECIES

A non-native species is a species introduced through human action (both accidentaland deliberate) outside its native range

An invasive non-native species (INNS) is a non-native species which has the abilityto spread and cause damage to the environment, the economy or the way we live

Examples include:

Non-nativespecies

Problems Caused Solutions

Grey Squirrel Introduced from North America in the 1800s:

• Out competes native red squirrel for food

• Carries • Red squirrel numbers in

steep decline

• 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

Rhododendron Ponticum

Flowering shrub introduced from Asia in the 1800s:

• Spreads quickly through it tubers/roots

• Nothing grows underneath it (blocks out light)

• Cutting back and burning (but this pollutes atmosphere)

• Using herbicides / weedkillers - but shrub is becoming more resistant to these and these are expensive

CONFLICTSConflicts arise where two competing land users disagree. An example is thedisagreement between environmental groups e.g. RSPB and the ForestryCommission who plant trees to produce wood across much of Northern Scotland

Conflict Solutions / Strategies

• Forestry Commission plants non-native 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

• 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

CONSERVATION

Conservation is the regulation of wild animals and plants (and their habitats) in orderfor them to be able to survive and continue as species in the wild. A number ofspecies 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 inScotland. These are shown below

Method Role

SNH Scottish Natural Heritage is the most important organisation in Scotlanddealing with conservation. It is public body, which gets taxpayers moneyWhat 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.SEPA 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

SSSI Sites of Special Scientific Interest. There are over 1400 in Scotland and someof these are very small, and attempt to protect animals, plants or the geologyof 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

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Ecosystem Sampling Equipment & Method Technique Improving ResultsTree Beating Stick &

TrayA 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.

• 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

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

• Set up several traps• Disguise the opening with a leaf or stone

• Check traps regularly or put preservative liquid in the beakers

Pond / Stream

Pond Net 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.

• Choose a net with finer mesh to catch smaller invertebrates

• Repeat the procedure many times to increase reliability

Vegetation / Plants

Quadrat (type of grid usually with 100 squares)

Randomly position a quadrat and count the plant types (or ground cover) in each square

• Repeat the procedure many times

Methods of sampling will depend upon the ecosystem under investigation:

SAMPLING METHODS IN ECOSYSTEMS

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.

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MEASURING ABIOTIC FACTORS

All measurements have the potential to introduce error, all equipment should beproperly maintained, calibrated and used appropriately

Estimating Population Size

The “capture-mark-recapture” technique can be used to estimate the size of apopulation:

• 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:

Abiotic Factor Sampling Method Improving ResultsTemperature (soil/water)

Thermometer. • Repeat and average to boost reliability• Ensure probes of equipment are clean before use to avoid inaccurate readingsSoil moisture Soil moisture probe

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

• Colorimetric methods (react with O2 in water to give colour change)

• Repeat and average

Flow rate (stream discharge)

• 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)

• 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)

Wind speed / direction

• Speed is measured by an anemometer and direction by a wind vane

• Need to be located in an area which is not sheltered

Rainfall • Rain gauge • Empty same time each day• Repeat and average

USING KEYS 12

Keys are methods used to identify a species. A key can be branching or a series ofpaired statements with simple 'yes / no' answers.

1. Branching Tree Example

This tree could help you identify a newvertebrate. For example, if it had nofur or feathers and dry skin, you wouldfollow the right-hand pathway at thefirst and second junctions, but the left-hand pathway at the third junction.This would lead you to identify theanimal 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?