PROGRAM DIDIK CEMERLANG AKADEMIK
SPM
ORGANISED BY:
JABATAN PELAJARAN NEGERI PULAU PINANG
BIOLOGY
MODULE 11
Colonisation and succession
Term Meaning
colonisation Occurs when certain species of organisms arrive at a new habitat, reproduce and take control of the habitat Pioneer species The first species of organisms to colonise a new habitat Successor A species which takes over the place of the pioneer
species
Succession The process whereby a pioneer species is replaced gradually and consecutively by other species
Colonisation and sucession in an abandoned mining pool
Figure Explanation
1. After mining activities ,mining pools are often left
abandoned. In such a pool, colonisation will soon occur
2. The pioneer species in an abandoned mining pool are
submerged plants. They include pond weeds such as
Hydrilla sp, Elodea sp., Cabomba sp., and Utricularia sp.
3. When these submerged plants die, they settle to the bottom of the pool and become humus
4. The humus, as well as soil eroded from the sides of the pool makes the pool
shallower. Such a condition is not suitable for the
submerged plants anymore. It is more suitable for floating plants such as water lily (Nymphaea sp.),
duckweed(Lemna sp.), and water hyacinth (Eichornia sp.) .Hence, the number of
floating plants increases.
shallower.
6. There will come a time when the pool is too shallow for floating plants. At this stage,
amphibian plants will grow and gradually replace the floating plants. Amphibian plants are plants which can live in water as well as on land, for example Fimbristylis sp. and Lepironiasp.
7. The death of old amphibian plants adds humus to the bottom of the pool and makes it even shallower.
8. When the pool is so shallow that there is little water in it, small terrestrial plants will begin to grow. These include grasses, ferns and herbal plants. The number of amphibian plants decreases.
9. Bigger and woody terrestrial plants follow suit. Over hundreds of years, a tropical rainforest is eventually formed.
Colonisation and sucession in a mangrove swamp
1.Swamps are formed by deposition of mud and silt carried down by the stream, when its flow is slowed down upon impact with tidal waves. Such swamps are newly formed land ready to be colonised. However most plants are not able to colonise them due to various reasons :
a) The ground is too soft and unable to support plants
b) Its waterlogged mud contains very little oxygen. This poses a problem because the roots of plants need oxygen for respiration.
c) Seawater contains a lot of salt and therefore is hypertonic. Because of this, it tends to draw water out of the roots of plants by osmosis. This can cause dehydration of plants.
e) The swampy area is exposed to strong sunlight and intense heat. Any plants which grow there will be at risk of losing water excessively due to their high transpiration rate.
2.Only mangrove trees are able to colonise such an area of harsh conditions. Generally, mangrove tree have the following adaptive characteristics to overcome the problems mentioned above :
a) They have a highly branched root system that spreads over a big area to support the plants in soft ground.
b) Most mangrove trees have breathing roots called pneumatophores.
Pneumatophores grow upwards and protrude out of the ground. On the surface of pneumatophores are lenticels which can absorb atmospheric oxygen.
c) The roots of mangrove trees are able to withstand the high salt content of seawater. This is because the cell sap of the roots has a salt content that is higher than that of seawater. The roots do not lose water by osmosis. Instead, seawater enters the roots. Excess salt which enters the trees are eliminated through hydathodes found at the lower epidermis of leaves. d) Most mangrove trees have viviparous seeds. This means the seeds start
germinating while the are still attached to the parent plant. When they germinate, they produce a long radicle. When the seedlings are released, the long racidle helps to lift the shoot above the ground. As such the seedlings do not drown, nor will they drift to the sea.
e) The leaves of mangrove trees have a thick cuticle with sunken stomata to reduce transpiration. The trees also store water in their thick and succulent leaves.
Profile of a swampy seashore and the plants which grow there
1. The pioneer species in such a swampy are Avicennia sp. and Sonneratia sp. grows in areas facing the sea, while Sonneratia sp. is found in more sheltered areas.
Pneumatophores of Avicennia sp. and Sonneratia sp.
3. Their highly branched root system enables Avicennia sp. and Sonneratia sp. to trap more silt and mud carried downstream by the river. Over a period of time, the shore is slightly raised and becomes less waterlogged. Such conditions are more suitable for another kind of mangrove tree, namely Rhizophora sp. Hence, Rhizophora sp. gradually replaces the pioneer species.
4. Rhizophora sp. has a prop root system to support the trees in soft ground.
Prop root system of Rhizophora sp.
5. The seeds of Rhizophora sp. show distinct viviparity.
6. The prop roots of Rhizophora sp. continue to trap more silt and mud. At the same time, humus is formed from the pioneer species and old
Rhizophora sp. trees which die, as well as from fallen leaves.
7. Gradually, the shore is raised higher. Its soil becomes more compact and fertile, and less saline since it is only bathed in seawater during high tide. Such conditions are ideal for another species of mangrove trees, that is
Bruguiera sp.
Buttress root system and pneumatophore of Bruguiera
9. As more earth is deposited, the shore extends further to the sea. The old shore is now further away from the sea. It is more and more like terrestrial ground.
10.Coconut trees, Nipah and Pandanus sp. begin to grow and gradually replace the Bruguiera sp trees. Other terrestrial trees, too begin to grow there.
OBJECTIVE QUESTIONS
1.Which of the following plants possesses the banyan root for support in the mangrove swamp?
A. Avicennia B. Bruguiera C. Sonneratia D. Rhizophora
2.Colonisation is said to have occurred when a species of a plant arrives at the new
habitat and
A. Starts to conquer the old plants
B. Grow, reproduce and conquer the habitat C. Eliminate the other plants
D. Becomes part of a different plant community
3. Which of the following roles are true of the pioneer species?
I causes changes in the habitat that become more suitable for its offsprings. II takes over the habitat from other plants
III increases the organic content of the new habitat IV makes gradual changes to the environmental factors
A. I and II B. III and IV C. I,II, and IV D. II, III, and IV
4. Which of the following plants will replace (succeed) the pioneer plant in pond? A. Herbaceous plant
B. Amphibian plant C. Floating plant D. Submerged plant
6. The species that first colonises a habitat is known as the A. Pioneer species
B. Successor species C. Dominant species D. Primary species
7. In mangrove swamps, the mangrove species which is found nearest to the sea is the
A. Avicennia sp. B. Sonneratia sp. C. Rhizophora sp. D. Bruguiera sp.
8. The root systems of mangroves are adapted to the conditions in a swampy area. Which of these mangrove species are matched correctly to the types of roots?
Rhizophora sp. Avicennia sp. Bruguiera sp.
A. Prop roots Buttress roots Extensive root system
B. Buttress roots Prop roots Extensive root system
C. Extensive root system Buttress roots Prop roots
D. Prop roots Extensive root system Buttress roots
9. Which of the following characteristics enable mangrove trees to live in a swampy area ?
I Have thick and succulent leaves
II Have breathing roots (pneumatophores) III can undergo anaerobic respiration
IV can store mineral salts that are absorbed A. I and II
10. Which of the following are the characteristics of a climax community ? I A climax community takes a long time to be formed
II A climax community is stable
III A drastic change in an abiotic factor can disturb the dynamic equilibrium of a climax community
IV The biotic and abiotic components interact with one another in a climax community
A. I , III and III B. I, II, and IV C. II, III, and IV D. I,II, III and IV
STRUCTURED QUESTIONS
Figure 1
1. Figure 1 shows the profile of mangrove swamp plants by the sea side. (a) i. Which zone has a lot of pioneer plants ? (1 mark) ii. Name a species mangrove plant found in the zone you have
named in (a) i. (1 mark)
(b) i. Name the structure P (1 mark) ii. State the primary function of structure P (1 mark)
(c) State the use of structure Q in Zone B (1 mark) (d) i. Name the way of reproduction that is special for plants found in Zone A (1 mark) ii. Give two problems that can be solved with the method of reproduction as in
(d) i. ( 2 marks)
(e) Explain the importance of mangrove swamps in the aquatic food web of
after an interval of time. ( 2 marks)
2. The terms below are related to colonisation and succession of an abandoned mining pool. Complete the table with suitable examples.
Plants Examples
1. Pioneer species (submerged plants)
A : B : C : 2.Floating Plants A : B : C : 3. Amphibian Plants A : B : 4. Terrestrial plants A :
B : C :
ESSAY QUESTION
1.
What is process X ? Describe how process X takes place in an area
Mentioned (10 marks)
ANSWER KEY
C: Rainforest
ESSAY QUESTION
Process X is the process of succession and the area is an abandoned
mining pool. (1)
The pioneer species (plants in the mud) at stage 1 die, decay and are
deposited at the bottom of the pond. (1)
The settling of humus and soil erosion cause the pond to be shallow.
(1)
The pond is now suited for floating plants(successor plants) such as
Lemna, Lotus, water hyacinth and the first succession takes place .(1)
The floating plants prevent light from penetrating into the depths of the
pond. (1)
This prevents the aquatic plants from photosynthesizing and the plants die
(1)
Finally, all the pioneer plants are replaced by floating plants and the pond
gradually becomes shallower because of the accumulation of humus at
the bottom of the pond. (1)
The banks of the pond is raised and becomes dry and the floating plants
cannot live under these conditions. (1)
Amphibian plants that can either live in water or on land such as
Fimbristylis sp. and Rusiga starts to grow around the area. (1)
