Ecology

MandPractivity 9

Study a Local Habitat, Using Appropriate Instruments and Simple Keys to Show the Variety and Distribution of Named Organisms

A simple key was demonstrated in the chapter Living Things (ICI).

The instruments for use: quadrat, pooter, pitfall trap, beating tray, line transect.

a) The Variety of Animals

The pooter, pitfall trap and beating tray can be used to capture small animals for identification. Once captured keys can be used to identify the animals.

Pooter is used as a ‘mini-vacuum cleaner’ to collect small delicate animals such as insects and spiders.

Pitfall Trap is used to collect small animals that ‘walk’ across the surface of the ground such as insects, spiders, woodlice, snails. Smelly decaying food may be placed in the trap as bait.

Beating TrayA stick is used to strike a leafy branch to knock small animals off onto a white cloth below. The animals may be taken off the cloth by forceps or pooter. Insects and spiders are commonly collected animals.

Many other animals may be identified from afar by normal sight, by using binoculars or by the traces they leave such as footprints and faeces. Animals easily identified by these methods are rabbit, fox, badger, hedgehog and birds.

b) Variety of Plants

Making a list of plant species in the habitat is easy, plants remain anchored in the soil and so do not have to be ‘captured’. The only problem is their identification using suitable keys

c) Distribution of Plants

Distribution means the natural geographical range of the plant and it can also mean its frequency of occurrence.

(i) To Investigate the Natural Geographical Range of a Plant e.g. daisy.

Method: Line Transect

A line transect is a measuring tape placed in a straight line across the field.

Three transect lines are used.

Mark the line of each transect on a map of the habitat.

Walk beside each line and mark the position of each ‘daisy’ touched by the line.

Combine the three transect results to calculate the ‘daisy’ distribution.

Use the scale to calculate the area in m2.

(ii) To Investigate the Frequency of Occurrence of Plants

Method: Quadrat

Frequency is number of quadrats a species would be present in out of a random 100 quadrats – therefore frequency is a percentage figure.

A quadrat is a square frame made of wood or metal.

Randomly place 20 quadrats in the field.

Record the plant species in each quadrat.

For each species record the number of quadrats out of 20 it was found in.

Multiply this number by 5 to calculate the species frequency.

Frequency scale: DAFORM

D: dominant A: abundant F: frequent

O: occasional R: rare M: missing (not present)

(iii) Investigating the Population of a Plant Species e.g. daisy.

Method: Quadrat

A quadrat with an area of 0.25 m2 (1/4 m2) is used.

Quadrats randomly placed in the field.

Number of plants in each quadrat is counted and recorded.

Average number of plants per metre squared is calculated.

This is then multiplied by the area of the species distribution to calculate the population.

Describing the Habitat

A good way to describe the habitat is to draw a map of it. Include the direction of north and give the size of the area. At least four physical features must be labelled on the map.

(iv) Investigating the Distribution of an Animal Species e.g. beetles.

Method: Grid Trapping

Pitfall traps are laid out in a grid pattern in the habitat.

A map of the habitat is made showing the positions of the pitfall traps in which beetles were found.

The pattern of these traps on the map is the distribution of beetles.

The food chain is a list of species, where each species is food for the next in the list.

Examples Grass » Rabbit » Fox

Buttercup » Bee » Thrush » Hawk

Bramble » Greenfly » Ladybird » Sparrow

The position of an organism in a food chain is called its trophic level.

Bramble: first trophic level, A.K.A. primary producer.

Greenfly: second trophic level, A.K.A. primary consumer.

Ladybird: third trophic level, A.K.A. secondary consumer.

Sparrow: fourth trophic level, A.K.A. tertiary consumer.

Green plants start every food chain – they are the producers, the makers of all the food in the community.

Food chains for the habitat being studied can be investigated by observing the feeding behaviour of the animals.

A food web is a chart of the feeding relationships in the habitat. A food web is made by linking food chains.

(i) Grass » Rabbit » Fox

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Hawk

(ii) Grass » Rabbit » Fox

Buttercup » Bee » Thrush » Hawk

Bramble » Greenfly » Ladybird » Sparrow

The food web shows that all species in the habitat are connected and if any one species is disturbed, then all species will undergo changes in its population.

Example: If all the foxes are removed, then the following changes are likely:

(a) Population increase: Rabbit, Hawk, Bee, Buttercup, Ladybird, Bramble.

(b) Population decrease: Grass, Thrush, Sparrow, Greenfly.

Interrelationships Between Organisms

1. Dependence: one species needs another for an essential resource for its survival and/or reproduction.

Examples: Rabbits need grass for food.

Buttercups need the bee for pollination.

Thrush needs the bramble (blackberry hedge) for nesting site (for shelter).

2. Interdependence: two species need each other – each supplies the other with an essential resource

Examples: Buttercups supply the bee with food and the bee pollinates the buttercups.

Bramble supplies the thrush with food and shelter and the thrush disperses the bramble’s seeds.

3. Competition: the rivalry between individuals as they ‘fight’ each other to obtain a supply of an essential resource when there isn’t enough for everyone.

Rivalry between individuals of the same species is called intra-specific competition..

Examples: Buttercups compete for light, water, space, mineral nutrients and pollinators.

Thrushes compete for territory, mates, food and nesting sites.

Rivalry between individuals of different species is called inter-specific competition. When resources are in short supply, organisms must compete.

Examples: Daisy and buttercups compete for space, light and pollinators.

Fox and hawk compete for rabbits.

Adaptation

Successful organisms are suited to their environment as they have the features that solve the problems that environment sets against survival and reproduction.

The advantageous features can be structural or behavioural.

Examples: The brown fur of the rabbit gives it camouflage to hide it from its predators.

The yellow petals of the buttercups attract insect pollinators.

The long pointed teeth of the fox allow it to kill its prey.

Types of Organisms in a Habitat

(a) Producers are organisms that can make their own food e.g. plants – grass, buttercup, daisy, dandelion and clover make their food by photosynthesis.

(b) Consumers are organisms that cannot make their own food; they obtain their food by feeding on other organisms or detritus – animals, fungi and most bacteria.

Detritus is dead organic matter – dead organisms and parts, excreta and egesta.

Consumer Types

(i) Herbivore: feeds only on plants e.g. rabbit, bee, greenfly (aphid).

(ii) Carnivore: feeds only on flesh (meat) e.g. fox, hawk, ladybird, swallow.

(iii) Omnivore: feeds on plants and flesh e.g. thrush, badger, magpie.

(iv) Decomposer: feeds on detritus e.g. earthworm, bacteria, field mushroom.

Decomposers are very important for they are food for other organisms. They also recycle carbon and the mineral nutrients that the plants have extracted from the soil. By recycling minerals the decomposers keep the soil fertile and maintain good plant growth.

Response of Organisms to Environmental Changes

If the habitat is studied at different times throughout the year then you will notice that the activity of organisms varies throughout the year depending on the seasons i.e. the climate has a huge influence.

Examples

Flowering period e.g. buttercup, bramble. Animal migration e.g. swallow.

Leaf fall e.g. oak.

Animal hibernation e.g. bees, greenfly. Withering of aerial parts e.g. buttercup. Breeding season e.g. ducks.

Population Size

The population of any species depends on a wide number of factors. The number of rabbits in a field depends on the amount of food plants that are present, competition from other species for food and also on the presence of predators such as foxes and hawks.

Plant populations are also influence by competition but also by the availability of insect pollinators, seed dispersers and also carnivores to keep the herbivore numbers from going too high.

Conservation is positive action to protect and preserve the natural environment.

The Importance of Conservation

1. By giving other species a healthy environment, we ensure that we also have a nice environment.

2. We depend on living organisms for all our food.

3. Many raw materials for important industries come from plants and animals.

4. Many of our important medicines come from living organisms.

5. Future generations have a right to a healthy planet.

Positive Human Activity Negative Human Activity

1. ‘Set-aside’: allowing agricultural land return to natural conditions by not farming that area. 1. Pollution

2. Use of ‘unleaded’ petrol. 2. Deforestation

3. Use of smokeless fuels instead of bituminous coal. 3. Desertification as result of poor farming practices.

4. Use of renewable sources of energy. 4. Use of pesticides.

5. Storage and treatment of slurry. 5. Introduction of foreign species.

6. Sewage treatment plants. 6. Roadbuilding.

7. Bicycle and Public Transport. 7. Overfishing

8. Domestic Waste 3Rs: reduce, reuse, recycle. 8. Illegal dumping.

9. Urban and national parks; nature reserves

Pollution is the contamination of the natural environment, with materials from our activity leading to an upset in the balance of nature.

Air pollution

1. Burning of fossil fuels (coal, oil, gas, peat)

(a) CO2: increases the greenhouse effect leading to ‘global warming’

Problems: climate change, sea level rise, greater storm damage.

(b) Nitrogen Oxides and Sulphur Dioxide: acid rain.

Problems: reduced soil fertility, death of fresh water lakes.

2. CFCs (refrigeration gases): destruction of the ozone layer in the atmosphere.

Problems: more skin cancer, more eye cataracts and threat to plants.

Water Pollution

1. Organic waste e.g. human sewage and farm slurry

Problems: de-oxygenation of water – fish kills, water not safe for drinking or

cooking, loss of recreational use of water habitats.

2. Artificial fertilisers: carried by runoff water from farmland.

Problems: excess plant growth in streams and canals – flood hazard, water may not be safe

Soil Pollution

1. Acid Rain: reduced soil fertility.

Inhibits the ability of plants to absorb mineral nutrient from the soil.

Inhibits the activity of bacteria in the soil.

2. Pesticides: absorbed by plants passing along the food chains to other species.

Kill non-pest species – causing major population changes.

Waste Management

Waste is material that is of no further value or use to us. Casual dumping or disposal of waste causes many environmental, economic and health problems. Waste must be managed to avoid these problems.

Waste management involves waste reduction, reusing the material and recycle the material for other uses.

Reuse and recycle do not contribute to pollution as the materials are not abandoned to contaminate the environment. But it is very difficult to reuse and recycle all waste materials so some material will be a complete waste and dealt with either in landfill or incinerated.

Some use can be made of waste destined for incineration – the energy released may be used for heating or generation of electricity.

Part of waste management must be the active inspection and investigation along with enforcement of antipollution laws backed up with severe penalties.