2.11) BIO modul 11 Dynamic Ecosystem (II)

  PROGRAM DIDIK CEMERLANG AKADEMIK SPM

ORGANISED BY:

  JABATAN PELAJARAN NEGERI PULAU PINANG BIOLOGY MODULE 11 COLONISATION AND SUCCESSION IN ECOSYSTEM

  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 Climax community The stable community formed at the end of the succession

  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.

  5. Because of the increasing

  number of floating plants in the pool, sunlight can no longer penetrate the pool. Without sunlight submerged plants are unable to carry out photosynthesis. They soon die off and become humus. Humus is also formed when old floating plants die. As more humus is deposited, the pool becomes even 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 Lepironia sp.

  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.

  d) The seeds of plants will sink easily into the soft and waterlogged mud, and die of oxygen deficiency. 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.

  2. Avicennia sp. and Sonneratia sp. have a stilt root system which is highly branched. They have vertical and sharp pneumatophores.

  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.

  8. Bruguiera sp. has a buttress root system to support itself. It has knee- shaped pneumatophores.

  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.

  11.Eventually, a tropical rainforest is formed. It is the climax community in the succession of mangrove swamps.

OBJECTIVE QUESTIONS

  4. Which of the following plants will replace (succeed) the pioneer plant in pond?

  D. I,II,III and IV

  C. I,II, and III

  B. II and IV

  A. I and III

  IV Has prop roots

  III Has cell sap with high pressure

  II Reproduce by the viviparous

  I Has thick succulent leaves

  5. Which the following are adaptations of the tree, Sonneratia sp. to live in mangrove areas?

  D. Submerged plant

  C. Floating plant

  B. Amphibian plant

  A. Herbaceous plant

  1.Which of the following plants possesses the banyan root for support in the mangrove swamp? A. Avicennia

  B. Bruguiera

  C. I,II, and IV

  B. III and IV

  A. I and II

  IV makes gradual changes to the environmental factors

  III increases the organic content of the new habitat

  II takes over the habitat from other plants

  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.

  D. Becomes part of a different plant community

  C. Eliminate the other plants

  B. Grow, reproduce and conquer the habitat

  A. Starts to conquer the old plants

  2.Colonisation is said to have occurred when a species of a plant arrives at the new habitat and

  D. Rhizophora

  C. Sonneratia

  D. II, III, and IV

  6. The species that first colonises a habitat is known as the

  C. Extensive root system Buttress roots Prop roots

  C. I,II and III

  B. II and IV

  A. I and II

  IV can store mineral salts that are absorbed

  III can undergo anaerobic respiration

  II Have breathing roots (pneumatophores)

  I Have thick and succulent leaves

  9. Which of the following characteristics enable mangrove trees to live in a swampy area ?

  D. Prop roots Extensive root system Buttress roots

  B. Buttress roots Prop roots Extensive root system

  A. Pioneer species

  A. Prop roots Buttress roots Extensive root system

  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.

  D. Bruguiera sp.

  C. Rhizophora sp.

  B. Sonneratia sp.

  A. Avicennia sp.

  7. In mangrove swamps, the mangrove species which is found nearest to the sea is the

  D. Primary species

  C. Dominant species

  B. Successor species

  D. II, III, and IV

  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 living things.

  ( 2 marks) (f) If the mangrove is allowed to develop naturally, what is the shape of the plants 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) Process X in a habitat takes place when a pioneer species has adapted and improved the environmental factors for other species

ANSWER KEY OBJECTIVE QUESTIONS

  1. B

  2. B

  3. B

  4. C

  5. C

  6. A

  7. A

  8. D

  9. A

  10.D

STRUCTURED QUESTIONS

  1.(a) i. Zone A ii. Avicennia sp. (b) i. Pneumatophore ii. structure P has openings namely lenticels for breathing. (c ) function of structure Q is to support the plant in the mud in zone B. (d) i. has viviparous seeds ii. – the seeds, with its geminated radicle falls into the soft mud and this prevents the seed from sinking and being carried away by the high and low tides of the sea.

• the seedling can get oxygen from the atmosphere and thus overcomes the problem of insufficient oxygen in the mud. (e) mangrove swamps is the confluence of mud and silt and become a source of food for the living things of the sea. The mangrove swamps are very rich with animals such as crabs, prawns, and others. (f) the process of succession takes place because of the prolonged deposit of mud and the area increases in height, becoming hard and dry. 2. 1. A : Hydrilla sp. B : Elodea sp. C : Cabomba sp.

  2. A: Lemna sp.

  B: Eichornia sp.

  C: Nelumbium sp.

  1. A : Fimbristylis sp.

  B : Lepironia sp.

  2. A : Ferns B : Herbal

  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)

  (1)  Amphibian plants dominate the middle area of the pond  Land plant species appear and this is the beginning of a primary forest (1)  A climax community, such as a tropical rainforest is finally formed (1)