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Biology Form 4Biologi Tingkatan 4Chapter 8 : Dynamic Ecosystem
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8.2 COLONISATION & SUCCESSION IN AN ECOSYSTEM
Levels of Ecological Organization
population all the members of one species in an area
community all the members of the different interacting species in an area
ecosystem all the members of a community plus the abiotic (physical) factors influencing them
biosphere entire region of the earth where living things may be found
THINKING TIME!!!
Colonization and succession
Colonization
process : living organisms moves into newly formed area which is completely devoid of life
E.g. an environment of sand and stones
The 1st colonizers are called pioneer species
Pioneer species
Can survive on dry and nutrient poor soil
Usually are hardy plants
E.g. : lalang, grass have dense root systems
to bind sand particles, water and humus
Short life cycle
Pioneer species
› When they die, their remains add to the humus content of the soil
› establish conditions that are more conducive to other species (successor species)
Succession
takes place when successor species :› moves into the modified environment› compete & gradually replace the
pioneer species› E.g.: Herbaceous plant
Successor species bigger than the pioneer species have small wind- dispersable
seeds (enable them to spread and grow rapidly
change the structure and quality of soil, making it more conducive for larger plants to grow
plants that grow over the remaining of successor species are called dominant species
DOMINANT SPECIES grow faster and can
out-compete the pioneers which grow at a slower rate
the dominant species modify the environment which allows larger trees to grow
E.g.: Shrubs
CLIMAX COMMUNITY The stable
community undergoes little
or no change in its species composition
RAINFOREST
Colonisation and succession in a pond
groups of plants play an important roles in the colonisation & succession of newly form pond:a) Submerged plantsb) Floating plantsc) Amphibious plantsd) Land plants
Submerged plants
elodea sp
Cabomba sp
Urticularia sp
Vallisneria sp
Hydrilla sp
Floating plants
Nelumbium sp(lotus)
Pistia sp
Lemna sp(duck weed)
Eichornia sp.(Water hyacinth)
Amphibious plants
Cyperus sp.
Scirpus grossus
Scirpus mucronatus
COLONISATION & SUCCESSION IN MANGROVE SWAMPS
Pioneer Species
Sonneratia sp. (Perepat trees)
Avicennia sp. (white api-api trees)
• Thick & fleshy leaves
• Waxy cuticles
• Hydathodes
• Viviparous seedling
• Long underground cable root system
• Pneumatophores• Vertical aerial
roots
Stagnant water & reduced oxygen content
Sea currentSoft &
muddy soil
High temperatur
e(Water loss)
High Salt
Pneumatophores
Successor species
Rhizophora sp
Has prop/stilt roots These aerial roots
anchor plants to the mud and play important role in aeration
Aeration can also take place through lenticels on the tree bark.
Rhizophora sp
Rhizophora sp
Dominant sp
Dominant species
Bruguiera sp.› Has buttress root
forms loop that protrude from soil to trap more silt and mud.
› This modifies the soil structure gradually.
Buttress roots of Bruguiera sp.
Dominant species
Over time, terrestrial plants such as Nypa sp., Pandanus sp., begin to replace the Bruguiera sp.
Nypa sp.
Distribution of different mangrove species at the mouth of a river
POP QUIZ
Rhizophora sp
Avicennia sp / Sonneratia sp
Brrugeira sp
Questions 8.2
1. Which of the following describes a population? A. The function of an organism or the role it
plays in an ecosystem B. The natural environment in which an
organism lives C. A group of organisms of the same species
living in the same habitat at the same time D. A natural collection of plant and animal
species living within a habitat in an ecosystem
Answer : C
2. Phytoplankton, zooplankton and algae are often among the first species to establish themselves in a mining pond. As time passes, submerged and floating plants will grow, followed by amphibious plants, grasses, small shrubs, bushes and eventually trees.
This is an example of A. colonisation B. competition C. evolution D. succession Answer : D
3. Over many years a forest can be found on an initially barren piece of land left behind by a volcanic eruption. What is the correct sequence of ecological processes that have taken place?
A. Colonisation, succession, climax community B. Colonisation, climax community, succession C. Succession, colonisation, climax communiity D. Succession, climax community, colonisation
Answer : A
5. Diagram 1 shows the seed of Rhizophora sp. which germinates while it is still attached to the parent plant
This phenomenon is know as A. double fertilisation B. oviparity C. viviparity D. vegetative reproduction
Answer : C
REVISION