Study of an Ecosystem (chpt 39)

Ecosystem

Community of organisms and its interactions with the environment

Flora and Fauna

Plants and animals

Key

Guide to identification

• Pictorial key: Book with drawings of each species

• Dichotomous key: Series of questions where there are normally two possible answers

Diversity of life in an ecosystem

Determined by making a consolidated species list (CSL), by searching ecosystem for different species and using equipment

Habitat

Place where a species lives

Types of Habitats in a Wooded Grassland Ecosystem

• Grassland: Mown area, equivalent to area grazed by large herbivores. Exposed to full sunlight and thus high light intensity. Exposed to wind and rain in full effects

• Ash Woodland: Native species

• Woodland Floor: Reduced light intensity and reduced effects of wind and rain. Decomposing plant material provides plentiful nutrients and retains moisture

• Stream: Freshwater habitat. Organisms found there determined by rate of flow, depth of water, pH, dissolved oxygen content, pollutants, etc. Soil nearby wetter resulting in different flora and fauna

Identify and use various apparatus for collection methods in an ecological study (mandatory experiment) - Animals

• Pooter: Collects small invertebrates. Suck through tube with gauze to prevent sucking up previously captured animals. To anaesthetise insects, filled with CO2, allowing time to identify them

• Pitfall trap: Catches invertebrates walking on surface of ground. Cup/beaker buried in ground so edge is flush with ground (if edge above ground, will walk around it). Lid above stops container filling with water, which would drown them. Also makes it easier to find it

• Beating tray: Catch insects hiding under leaves. Tray held under branch which is beaten with a stick. Sudden movement dislodges insects. Also stuns insects so do not have time to fly off. When on tray, collected w pooter

• Cryptozoic trap: Catch animals that shelter in secluded spaces during day or in dry weather. Old slate/wood placed on top of few supporting stones, leaving space underneath for animals. Heavy object placed on top to prevent wind blowing away

• Nets: Catch mobile animals, mainly insects/aquatic animals.

  • Butterfly nets: Catch insects on the wing (flying). Light to not damage insects/butterflies. Swept over insect and then twisted quarter turn to close opening. Insect placed in specimen jar or pooter

  • Fishing nets: Aquatic animals. If in pond, used like butterfly net. If in stream, placed on bottom with mouth facing upstream. Materials on bottom of stream in front of net are disturbed and current sweeps any animals into net

• Tullgren funnel: Extract small animals from leaf litter. Soil or leaf litter into sieve and turn on lamp. Soil and leaf litter dwelling animals don’t like light or heat and tend to move away. Lamp suspended above sieve drives them downwards and fall through mesh into container. Animals will almost certainly die rapidly from dehydration, so usual to place alcohol in collecting breaker to preserve them

  • Baermann funnel: variation of tullgren funnel. Sample of soil or plant tissue tied in muslin gauze and placed in large filter funnel full of water and sealed at botto. Small animals in sample try to escape and wriggle through gauze. Sink to bottom of filter funnel and can be collected and examined

• Mammal traps: Catch small mammals. Wooden, plastic or wire mesh. Need relatively large amount of food because lose lots of body heat, so ensure plenty of bait to keep mammal alive. Visited on daily basis. Secure firmly to prevent dogs, foxes, humans making off with them. When removing animal, wear thick gloves to prevent bites/scratches

Identify and use various apparatus for collection methods in an ecological study (mandatory experiment) - Plants

• Quadrat: Sample plants or sedentary animals. Quadrat frame encompassing known area. Usually 50cm x 50cm. Simple/plain frame and gridded. Gridded allows for easier estimation, as well as counting. Samples normally taken w quadrat in random manner within habitat. Random sampling avoids bias

• Belt transect: Investigate distribution of species varies w changing environmental factor, eg. light intensity. Pick line that crosses obvious changing environmental factor. Lay out line marked in metres and take sample at regular intervals

• Line transect: Same function as belt transect. Lay out line and record species of plant that touches or directly below each mark on line. Record results

Qualitative surveys

Record which species are present (limited view of ecosystem as proves no idea of how common particular species is)

Quantitative surveys

Determine which species are present and how many individuals present

Conduct quantitative study of plants in an ecosystem (experiment)

• Percentage Frequency: Number of quadrats of species occurs out of 100 quadrats

  • % frequency = Number of quadrats species occurs in/Total number of quadrats sampled x 100

• Percentage Cover: Estimating percentage of ground covered by species within quadrat. Gridded quadrats best. If square more than half full, regarded as full and vice versa is empty. Multiply number of filled squares to get percentage (eg. 25 squares in quadrat, 7 filled: 7 x 4 = 28%)

Conduct quantitative study of animals in ecosystem (experiment) → mark and recapture method

1. Set pitfall traps and leave overnight. Return and count and record ground beetles caught. Place beetles in central collection vessel: brightly coloured plastic bucket works

2. Mark each beetle using small dab of non-toxic waterproof paint. Mark discretely so predators won’t be attracted and will not hinder movements (top of thorax, not wing cases)

3. Release in same area. Reset traps and leave for day or two

4. Collect captured beetles when return following day. Count and record number of marked and unmakred beetles caught. Release all beetles as counted

5. Calculate pop.: (number caught on first day x total caught on second day)/number of marked beetles caught on second day

6. Error sources: miscounting or misidentifying species. Immigration/emigration of beetles from area

Investigate three abiotic factors (experiment)

• pH: using pH meter/indicator paper. pH meter calibrated using pH buffer solution and then inserted into medium (soil, water)

• Light intensity: Measured using light meter. When using, ensure sun is shining at same intensity each time you take a measurement. Hold meter in same orientation each time, horizontal

• Moisture Content: Meter or by experiment

  • Meter: Prove of meter placed in soil and value read from display

  • Experiment: Sample of soil taken and weighed. Dried in oven at 100 degrees overnight and then reweighed. Soil content calculated: weight (of water) lost/weight of dried soil x 100 = % moisture

• Temperature: Thermometer or temperature probe. Lab thermometers simply held in air or water to record temperature. Soil temps measure using thermometer protected by metal casing. Allow sufficient time for all cases

Eutrophication

Excess plant growth caused by excess nutrients