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Salters-Nuffield Advanced Biology Resources Extension 5.1 Teacher Sheet HOW FIRE AFFECTS BIODIVERSITY

In document NEW SPEC UNIT 4 (TOPIC 5) (Page 138-140)

This study of bushfire ecology is intended to allow students to apply their knowledge and

understanding of ecological studies to a new situation. It is based on an extract of text published in scientific journals, so the level of language is high.

Students will also meet the concept of influence diagrams. These specialist diagrams are included to give practice at understanding different ways of presenting information. Students should not feel they need to know how to produce them.

Ecosystems in areas that burn regularly often include plants and animals with special adaptations that make them resistant to, or in some cases dependent on, the fires. In some plants the seeds will only germinate if they have been burned. The extracts from the articles deal with some of the aspects of bush fire ecology in Australia. Other areas that experience similar regimes include the chaparral (scrub) in the western states of the USA and the final question links in with this.

Answers

Q1 After the rainfall many plants quickly grew and flowered on the burned areas of the bush. These plants included many that were not recorded at that site before. Even almost a year later, 53 of the 63 species recorded in the burned area were ‘new’ to the site.

Q2 The researchers thought the ‘new’ species came from seeds that were already in the soil at the site. They thought that there were too many different plants and that they were present too quickly for them to have arrived as colonisers after the fire.

Q3 It is likely that heat is involved in breaking seed dormancy. Alternatively, germination could be triggered by a chemical from the ash produced by the fire, or by increased light levels after the fire had removed the leaf litter/vegetation (though the researchers report that a large proportion of the ground (69%) was bare before the fire so light is unlikely to be a factor in triggering germination).

Q4 The three negative influences in Figure 1 are:

● The Triodia inhibit the germination of the ephemeral flora.

● They also inhibit the growth of the ephemeral flora into mature plants.

● Fire reduces the mallee, burning off the litter and other biomass.

Q5 A resprouter is a plant, which produces new suckers/sprouts from the burned stump. Q6 The ‘hidden diversity of the mallee’ refers to the soil seedbank of ephemerals. (Interesting

point – if the species that germinate depend on the season when burned, it would be very difficult to assess the true biodiversity.)

Q7 a Maintaining a mosaic of patches at different ages should increase biodiversity, as there will be a wider variety of habitats available. However, organisms that need a very large home range or population to be viable might be adversely affected.

b Re-colonisation of burned areas should be faster as organisms will have less far to go if the burned patches are small.

c This policy tends to reduce the damage done in any one fire because fewer areas will have large amounts of dead wood and litter, and these will be separated by areas that are less likely to burn.

d Extinction of a species is less likely if the fire is less extensive. Mobile species may be able to move out of the way and it is less likely that the whole of a suitable habitat will be burnt. Re-colonisation of the area should be faster, leading to less long-term loss of habitat.

e Organisms that are intolerant of burning, or require a large area of same-aged habitat may be harmed by this policy.

Salters-Nuffield Advanced Biology Resources

Safety checked, but not trialled by CLEAPSS. Users may need to adapt the risk assessment information to local circumstances. Extension 5.2 Student Sheet

LEAF STRUCTURE AND FUNCTION

SAFETY

Never use a microscope with a daylight mirror in a place where sunlight could strike the mirror. Your retina could be permanently damaged.

How is leaf structure well suited to its function in photosynthesis? How does its structure help in the delivery of the raw materials needed for photosynthesis to where they are needed? How is it suited to the subsequent removal of the products? In this extension your aim is to relate the structure of the leaf to its function in photosynthesis, recalling knowledge from topics you studied in Year 1 of the course. 1 First examine the external features of a dicotyledonous leaf, for example, privet (Ligustrum), then

view a prepared slide of a transverse section of a leaf under the microscope. See also Figure 1 below. Make a low-power plan drawing of the leaf. Remember in a low-power plan drawing there is no need to show the presence of individual cells.

2 Annotate the parts of your plan that illustrate how the leaf is adapted to its function. You need to show how the leaf is well suited for:

 light interception

 rapid diffusion of carbon dioxide into the palisade cells and removal of waste products from the palisade cells

 transport of water to the leaf and photosynthetic products away from the leaf.

3 Write a short paragraph to describe any adaptations that you are not able to see using a light microscope.

Salters-Nuffield Advanced Biology Resources

Extension 5.2 Teacher Sheet

In document NEW SPEC UNIT 4 (TOPIC 5) (Page 138-140)