Chapter 5: Study of an Ecosystem

Chapter 5: A Study of an Ecosystem

A Broad Overview of a Selected Ecosystem
Choose your ecosystem and visit it. Suitable ecosystems include:

  • hedgerow
  • stream
  • rock pool
  • rocky seashore
  • old wall
  • small woodland
  • small meadow
  • freshwater pond
  • waste land
  • an overgrown garden
  • soil
  • peatland
  • grassland

Practical Activity: Select and visit one ecosystem, e.g. hedgerow
Physical properties:

  • Acts as a boundary to the field
  • It is a large hedgerow
  • Provides good protection from the weather
  • It can be classed as a very small woodland area

General presence of life:

  • Flora: many trees and shrubs, plants, and grasses
  • Fauna: herbivores, birds and predators

Practical Activity: Observation and Scientific Study of a Selected Ecosystem
Identify any five fauna and any five flora using simple keys:
Flora:

  • Hawthorn
  • Blackthorn
  • Gorse
  • Blackberry bramble
  • Fuschia
  • Holly
  • Rowan (Mountain ash)
  • Ash saplings
  • Hazel
  • Willow

Fauna:

  • Beetles
  • Butterflies
  • Hoverflies
  • Snails
  • Ladybirds
  • Hare
  • Foxes
  • Badgers
  • Hedgehog
  • Mice

Identify a variety of habitats within the selected ecosystem
There are a number of habitats in the selected ecosystem of the hedgerow:

  • Soil
  • Leaf litter
  • Shrub level
  • Canopy level

Different organisms are found in each of the habitats.

Ecology Apparatus
Identify and use various apparatus required for collection methods in an ecological study

  • Mammal trap
  • Pitfall trap
  • Cryptozoic trap
  • Beating tray
  • Pooter
  • Nets (to include – sweep net, insect net, plankton net or fish net)
  • Direct search
  • Tullgren funnel

Traps:
Mammal trap

  • Bait attracts small mammals into box
  • Once they enter the trap door prevents exit

Pitfall trap

  • Involves simple can or plastic up embedded in the ground and covered to prevent water entering
  • Bait is sometimes used

Cryptozoic trap

  • Shelter trap involving a piece of old wood, a log, or a large stone
  • Small animals like slugs and woodlice hide under a cryptozoic trap during periods of inactivity

Beating tray

  • Hold under tree or bush
  • Shake the tree or bush
  • Insects fall onto tray and can be identified

Pooter

  • Device ecologists use to pick up small objects, like insects
  • Like a miniature vacuum cleaner with your lungs working as the engine

Sweep nets, insect nets, plankton nets

  • Have a lightweight aluminium frame
  • The net bags usually have curved tips to help prevent insects escaping
  • Sweep net usually have a 5-sided frame designed to give a better sampling sweep than circular frames
  • Plankton nets are long and very light designed to

Tullgren funnel

  • Used for both dry and wet extraction of soil organisms from soil samples
  • A soil sample is placed in the removable upper part of the funnel
  • Heat and light from the lamp creates a temperature gradient of approximately 14°C in the soil sample
  • This stimulates the downward movement of soil arthropods, and similar organisms, through the gauze to a receiver attached to the base of the funnel

Organism Distribution
There are two ways in which organism distribution is determined:
Qualitative survey:

  • Record of presence/absence of organism

Quantitative survey of flora and stationary/slow-moving fauna:

  • Subjective estimate – prone to variation amongst researchers – not as accurate as objective estimate.
  • Objective estimate – accurate (two methods).

1. Quadrats
2. Transects

Objective estimation: Quadrats

  • Squares with sides of either 1, 0.5, or 0.25 m
  • Thrown randomly in habitat over shoulder
  • Two measurements taken with quadrat:

1. Percentage cover: estimate of the ground in quadrat covered by each species of interest
2. Frequency: chance of finding a named species with any one throw of the quadrat

Limitations:

  • Animals can move fast and not remain in the quadrat
  • Limited by species size, e.g. trees and large animals

Percentage cover: estimated using one of two methods:

  1. The area of quadrat covered by each species (five flora) of interest is estimated as a percentage of the total quadrat area – not very accurate.
  2. Using a graduated quadrat the total number of squares (25) is divided by the number of squares (top and right sides only) touched by the flora of interest (e.g. 10) – much more accurate.
Picture

Quantitative survey of plants:
Use one of two methods:

  • Frequency: presence/absence recorded as a %
  • Percentage cover: approximate % of the area of the quadrat that is occupied by plant species OR the number of plants touching top and right sides of graduated quadrat

Sources of error in studying an ecosystem:

  • Human error – especially when estimating frequency
  • Changing conditions – seasonal variations
  • Accidental discovery – by a walker instead of an ecologist
  • Sample size – more samples, better accuracy

Measuring the Effects of Abiotic Factors
Study the effects of abiotic factors on the suitability of an organism to its habitat
You must study at least 3 abiotic factors:

  • pH
  • temperature
  • light intensity
  • water current
  • air current
  • dissolved oxygen
  • mineral content
  • percentage air in soil
  • percentage water in soil
  • percentage humus
  • salinity
  • degree of exposure
  • slope

Then describe how each of the 3 you chose affects your ecosystem

Identifying Organism Adaptations

  • Adaptations are necessary for an organism to survive new conditions
  • Adaptations may be structural, competitive, or behavioural
  • Describe ONE adaptation of an organism you studied in your habitat
  • Snail has a protective shell
  • Ladybird has a red covering to warn birds that it is poisonous to eat
  • Blackthorn has thorn to protect its fruits

Identifying Organisms’ Role in Energy Transfer

  • Identify where each organism in your habitat is positioned in the food chain/food web
  • From the data collected on your field trip construct a food chain, food web, and pyramid of numbers

Analysis

  • Learn to analyse, assess, and discuss your results and conclusions
  • Is there any relationship between the results and conclusions of your study and local ecological issues
  • Prepare a portfolio/report/project (no less than 1,000 words, no more than 2,500 words)