DYNAMIC ECOSYSTEM Question

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1(a) - Colonisation is a process in which organism starts to inhibit an unhabitat area such as bare ground and forms a colony.

- Succession is the gradual process where one community changes its environment so that it is replaced by another community.

- Diused pond, pioneer species are Phytoplankton (microscopic algae) and submerged plant (Hydrilla sp., Cabomba sp., elodea sp.) begin to grow and carry out photosynthesis.

- When they die and decompose, organic matter converted into humus at the pond base, the pond become shallow.

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1. b)

-The condition becomes favourable for floating plants such as water hyacinths (Eichornia sp.) and duckweeds (Lemna sp.)

-They spread covering water surface and prevent sunlight from reaching the submerged plant causing these plants to die since they cannot photosynthesise.

- The decomposed plants add more organic matter and the pond becomes more shallow.

- The emergent plants (sedges, cattails) replace the floating plants. - They grow from the edge of the pond towards the middle of the pond as the pond becomes more shallow.

- When these plants die, their decomposed remains are added as sediments to the base of the pond thus reduces the depth of the pond. - The condition becomes suitable for land plants like small herbaceous weeds.

- Gradually, the land becomes much drier and more land plants (shrubs, herbs and large woody plant) start to grow.

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- A jungle emerges and turns into a tropical rainforest which form a climax community.

– It is a balanced ecosystem which involves the interaction between the abiotic and biotic factors.

- Ensures conversation of biodiversity, preservation of flora, fauna and organism.

- Preventing the extinction of flora and fauna.

- Maintaining major sources of human food such as ulam, meat, honey and sources of traditional medicinal herbs.

- Sustains the food webs in the ecosystem.

- Preventing disruption of the natural cycles of water/carbon and also balancing photosynthesis and respiration.

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- Provides natural water catchment areas.

- Preserves natural resources for recreational activities and eco- tourism.

- Reduces stress and promotes a healthy lifestyle.

- A balanced ecosystem prevents the loss of plants which will cause a reduction in food resources and food chains.

- It will also cause soil erosion and flash floods.

- And the extinction of some animal and plant species.

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2. a) i)

- The ground is too soft and muddy soil, unable to support plants. - Waterlogged conditions of the soil decrease the amount of oxygen for root respiration.

- The swamp water has a high concentration of salt and is hypertonic compared to the cell sap of the root cells.

- The plants growing in swamp will have the problem of dehydration. - Seeds that fall into the muddy swamp will die of dehydration/ insufficiency of oxygen.

- The swamp is exposed to the sun leads to a high rate of transpiration. 1 1 1 1 1 1

2. a) ii)

- As a result, the plants growing there will lose water very fast by transpiration. ANY 5 - Root system which is highly branched and widespreads underground cable roots to give good support to the plants.

- Pneumatophores (breathing root) which grow protruding upwards above the ground to allow gaseous exchange.

- The cell sap of the roots cells has a higher osmotic pressure than the soil water that surrounds them to enable water enter the root by osmosis.

- Hence, the cells are able to withstand the high salt content of the swamp.

- Excess salt is eliminated through hydatodes found at the lower epidermis of leaves.

- Viviparous seeds which germinate while still attached to the mother plants.

- The long radical produced will let the seedling stick into the ground, not submerged into the soft and waterlogged soil or drift away.

- Thick layer of cuticle covers the leaves and succulent which help to reduce the rate of transpiration and store water.

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Question 3

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3.a)

3. b)

-The diagram shows a saprophytic fungus.

- It obtain its nutrient by secreting digestive enzymes onto the substrate.

- The enzymes digest the complex substances into simple forms. - The simple forms are then absorbed by hypha.

- Owls are predators and rats are preys.

- In the month of January until April, the increase in the prey’s is followed by an increase in predator population.

- Due to abundance of food.

- However from April to August, when the number of predator 1 1 1 1 1 1 1 1 4

increases, the number of preys will then decrease.

- This is because the high number of predators will easily consume the prey.

- When the prey reduces, the predators will have less to eat. - There is intraspecific competition.

- The number of predators also reduces in the following months from August to December.

-The prey-predator relationship takes place in cycle.

- This keep the population of both organisms in a dynamic equilibrium. ANY 6 1 1 1 1 1 1 10

Question 4:

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4. - Rhizobium bacteria inside the root nodules of legumes and Nostoc sp. found freely in the soil fixed the nitrogen in air.

- Decaying bacteria/ fungi decompose plant/ animal/ dead organism/ waste product

- To form ammonium compound.

- Nitrosomonas sp. / nitrifying bacteria converted ammonium compound to nitrite.

- Nitrobacter sp. /nitrifying bacteria convert nitrite to nitrate. - Nitrate is absorbed by plant to form plant protein.

- ( Plant protein ) eaten by an animal to form animal protein. - Denitrifying bacteria reduce the nitrate content in the soil. - by converting the nitrate into the nitric oxide and nitrogen gas.

- Nitrogen gas goes back into the atmospheric to complete the nitrogen cycle. 1 1 1 1 1 1 1 1 1 1 10

CHAPTER 9: ENDANGERED ECOSYSTEM