Harap Maaf Kerja Kerja Pemurnian Sedang Di Jalankan

Harap Maklum

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Species, Population, Community,   

Habitat and Ecosystem

1 There are millions of plant and animal species on Earth.

2 A species is a group of similar organisms with common characteristics. They can breed among themselves to produce fertile offspring.

3 It is estimated that there are about 13.6 million species living on Earth. Some are big, some are small, and some can only be seen under the microscope. They move on land, swim in water, fly in the air, and some even live on the body of other organisms.

4 Each species is adapted to live in specific conditions in certain surroundings. This is referred to as a suitable environment for that species.

5 Everything surrounding a species that affects how it lives and survives is known as its environment.

6 A species that is best adapted to its environment is the most likely to survive and reproduce successfully. Organisms that are poorly adapted will not survive.

7 You have learnt in the previous chapter that a place where plants and animals live is called a habitat. It is the place that provides food, shelter from enemies, protection from bad weather and opportunities for breeding.

8. In an environment, there are different types of habitats. Treetops, tree trunks, ponds, rocks, pools, rotting logs, burrows in the soil, and even rooms in our homes are a few examples of habitats.

9. A population is a group of organisms of the same species living together and reproducing at the same time. For example, we have population of tigers, a population of human beings and a population of ferns.

10 The different populations of plants and animal which live together in the same habitat make up the community. For example, a freshwater pond community consists of population water hyacinths, duckweeds, dragonflies, watersnails, freshwater fish and tadpoles.

11 The organisms in a community are interdependent on one another and their environment. An organism cannot live in isolation.

12. An ecosystem consists of several communities that interact with one another and environment.

13. The environment is made up of living and non-living components.

14 (a) Non-living components are physical factors that affect the organisms’ way of life.

     (b) Light, temperature, oxygen, carbon dioxide and water are some examples of physical factors.

15 The relationships between species, population, community and ecosystem are shown in Figure 4.1

 

Figure 4.1 How ecosystem is formed

Figure 4.2 shows the relationships between species,

                population and community in a grassland.

17. Figure 4.3 shows an ecosystem in a freshwater pond.

18. There is usually more than one habitat in an ecosystem. For example, there are various habitats in the pond ecosystem as shown in Table 4.1.

Figure 4.3 An ecosystem of freshwater pond

Table 4.1 The various species found in the different habitats of the pond

Habitat	Spesies
Pond apron	Cattails, rusiga, grasses, frogs, toads, kingfishers, grasshoppers
Water surface	Water hyacinths, lotus, duckweeds, water insects, mosquito larvae
Middle water level	Tadpoles, fish, algae, daphnia
Pond base	Elodea, Hydrilla, shrimps, water snails
Under pebbles or stones in the pond	Worms, bacteria, Paramecium

(a) The different communities found in the pond ecosystem include cattails, rusiga, grasses, frogs, toads, kingfishers and grasshoppers on the pond apron.

(b) Water hyacinths, lotus, duckeeds, water insects and mosquito larvae are the community on the water

      surface.

(c) Populations of tadpoles, fish and algae are found at the middle water level.

(d) There are also communities of Elodea, shrimps and water snails on the pond base.

(e) A community of worm and bacteria can found under pebbles or stones in the pond.

(f) In the pond ecosystem, there are the non-living factors that influence the distribution of the organisms.

    These factors are water temperature, air temperature, oxygen content in water, mineral content in water,

     rainfall and light intensity.

19. Forests, grasslands, seashores, rivers, mountains and deserts are some of the world’s ecosystems.

Interdependence of living Organisms Creates   

A Balanced Ecosystem

1. In a particular ecosystem, various organisms coexist together. The various organisms live together and are interdependent on one another for their survival. They interact with one another and the environment to help create  a balanced ecosystem.

2. A balanced ecosystem is one that does not change very much over a period of time. The size of each population remains the same through a steady supply of basic needs like oxygen, food, shelter and breeding partners.

3. When a population grows too big, organisms from the same species will compete with each other for their basic needs. The weaker or may not survive, thus leading to a reduction in the population.

4.  A balanced ecosystem also helps to purify and recycle gases, water and minerals. It even controls the climate.

5. In the pond ecosystem, as discussed earlier, the aquatic plants obtain their food from sunlight during photosynthesis. The plants obtain carbon dioxide from aquatic animals which release oxygen during respiration.

6. The animals in return obtain their supply of oxygen from the plants which release oxygen during photosynthesis.

7. The aquatic plants also obtain minerals from the soil at the bottom of the pond.

8. The animals cannot make their own food but depend on other organisms to obtain food. They eat plants or other animals found in their environment.

9. Some pond animals depend on aquatic plants for shelter and protection. They cling to parts of the plants like the leaves. These animals are able to camouflage themselves as their body colours match the colours of those parts of the plants they are attached to.

10. Aquatic plants depend on non-living compound of the environment and other organisms for reproduction. These plants rely on water, wind, insects and birds for pollination and dispersal.

11. The favourable climatic conditions and the abundance of water may help certain animals to find breeding partners and to disperse their eggs. The absence of predators in the pond may also increase their chances of survival. The presence of plants provides opportunities for the eggs or the young ones to attach themselves

Figure 4.4 Interdependence among living organisms

12. Microorganisms like bacteria in the soil help to decompose dead organisms and release minerals into the soil. These minerals act as nutrients for the plants. These microorganisms are known as decomposers.

13. Decomposers play an important role in the relationships which exist in an ecosystem. They break down dead organisms, and return the relevant gases and minerals to the environment. By doing this, they also clean up the environment.

14. The interdependence among living organisms and their environment creates a balanced ecosystem. The amount of food, the availability of shelter, breeding partners and space keep the population of each organism in check. There are enough decomposers to return gases and minerals to the environment

4.2 Interaction between Living Organisms 

1. In any ecosystem, organisms interact with one another in order to survive.

2. Interaction between living organisms helps the organisms to obtain food, shelter, protection, breeding partners, regulate their population size and maintain the balance of nature.

3 Organisms interact in many ways (Figure 4.5) 

Types of interaction	Effects	Examples
Competition  • Organisms struggle, fight or search for the same basic needs. • Competition becomes more intense when basic needs become limited. • Normally, they compete for shelter, nesting sites, food, sunlight, minerals and breeding partners. • Organisms that are stronger, fitter and better adapted to environmental changes will be successful and survive. • There are two types of competition. (a) Intra-specific competition This is a competition between organisms of the same species. (b) Inter-specific competition This is a competition between organisms of different species. a b Figure 4.7 Polulations of two species of Paramecium cultured (a) separately and (b) together.	+ (stronger organism) — (weaker organism)	Figure 4.6 Competition between the lion for food
	+ (stronger organism) — (weaker organism)	• Two male tigers fighting for a tigress. • Bitter gourd plants competing for   support to reach sunlight.   Balsam plants competing for sunlight.
	+  (stronger organism) — (weaker organism)	·      Two different species of Paramecium. P. aurelia and         P caudatum competing with each other for food. P. aurelia         emerges as the winner (Figure 4.7). ·      Graph (a) shows the population of P. aurelia and P caudatum species living separately. ·      Graph (b) shows the two populations living together and therefore competing for the limited amount of food. ·      As a result, P aurelia, the stronger species. kills P. caudatum. ·      The population of P. cauda turn decreases. The population of P. aurelia increases. ·      The maize plants competing with weeds for water and minerals. ·      The owl and the snake competing with each other for food (the rat).
Symbiosis • The close relationship between two organisms of different species which live closely together and interact with each other. At least one of the two living organisms benefits from this relationship. • There are three types of symbiosis. (a) Commensalism A relationship between two organisms in which one partner benefits (the commensal) while the other does not receive any benefit or harm (the host). Figure 4.8 The tiyctroid growing on a shell occupied by a hermit crab (b) Mutualism • An interaction between two different species of organisms which benefits both organisms. • This relationship helps the organisms to survive in harsh conditions. Neither organism will be able to survive on its own. (e) Parasitism • In this relationship, there is a parasite and a host. • The parasite benefits from living outside or in the host. • The host is harmed or may even be killed by the parasite.	+ (the commensal) O (the host)	§ A remora fish is often found attached under a shark, gets free transportation, and feeds on food scraps left by the shark without harming it. § Hydroids are found attached to the shells of hermit crabs. The hydroids obtain food particles from the crab plus a free ride. The crab does not gain anything from this relationship (Figure 4.8). § Barnacles attach themselves to the skin of whales and get a free ride through nutrient-rich waters, without the whales being harmed or deriving any benefit from this relationship.
	+ (both organisms)	• An alga and a fungus form a lichen. The alga produces food and the fungus provides shelter (Figure 4.9). • A sea anemone attaches itself to a hermit crab in such a way that the anemone’s mouth and tentacles are close to the mouth of the hermit crab to obtain food scraps and also free transportation. The hermit crab gets protection from the anemone’s stinging cells.
	+ (the parasite) — (the host)	Ticks, fleas, lice (singular: louse) and mosquitoes (parasites) live on the skin of mammals (hosts) and suck the blood of the host. Tuberculosis bacteria (parasite) attack human (host) lungs. Round worms, tapeworms, hook worms and thread worms live inside the intestine5 of humans (hosts). These parasites obtain food and shelter from the host. The host loses weight and is weakened.
3 Prey-predator relationship In this relationship, the predator which is normally bigger in size, hunts, kills and feeds on the smaller, hunted animals called the prey. Generally, the predator population is smaller than the prey population.	+ (predator) --   (prey)	Frogs (predators) feed on grasshoppers (prey). Lions (predators) hunting deer (prey) for food. Bigger fishes (predators) feeding on smaller fishes (prey).

4 Characteristics of predators and prey: 

(a) Generally, predators are bigger in size than the prey. However, the population of predators is smaller than the prey.

(b) The predators are well adapted to kill their prey. They possess good vision (eagles), sharp claws, strong beaks (eagles), a good sense of smell, powerful jaws and sharp teeth (lions).

(c)They have the ability to run faster than their prey. Their bodies are camouflaged (tigers) to prevent detection.

(d) Predators are carnivores while the prey may be omnivores or herbivores.

(e) Prey also have sharp eyes to detect the presence of predators. They have the ability to run and escape from predators.

(f) Just like the predators, prey also have body colours that blend very well with their surroundings (zebras). This characteristic helps them to avoid being easily detected by the predators.

(g) Some prey give out unpleasant odours or harmful chemicals. Some can mimic the colours or smell of other stronger animals to frighten or confuse the predators.

5 (a) When the number of predators is low but the number of the prey is high, the population of the predators increases rapidly.

(b) Then as the number of the predators increases, the population of the prey decreases.

(c) When the population of prey falls, competition between predators for food increases. So the predator population decreases because of death due to starvation.

(d) With a smaller number of predators, the prey population begins to increase again. This is shown in the graph in Figure 4.10.

Biological control 

1 After knowing how living organisms interact with one another, it is not difficult (in theory) to think of a method to control the population of a particular species (X) by using another species (Y) that feeds on or kills species X.

2 Using a living organism to check the population growth of another organism is known as biological control.

3 The organism used to control the population of a pest is known as the biological control agent.

4 The predator-prey interaction is used widely in biological control. Other interaction like parasitism and competition are also used.

5 This is in contrast to using chemicals like pesticides, herbicides, fungicides or insecticides to control the population of living organisms. This approach is called chemical control.

6 Biological control is used in agriculture to contain the pest population that attack crops and fruit trees.

Table 4.3 Examples of biological control

Organism X that is to be controlled	Biological control agent for X
Cactus Opuntia in Australia was a nusisance in the early twentieth century	The caterpillar of the mouth Cactoblastus was introduced in large numbers to eat up the cactus plants
Larvae of a stem borer feed on the leaves and stems oil palm trees.	A type of fly known as Ichneumon can be used to control the larvae (Figure 4.11(a)).
Rats in oil palm estates are pests.	Snakes and owls are used to control the rat population (Figure 4.11(b)).
To control the growth of weeds in rubber  and oil palm estates.	Grass such as the Imperata cylindrica is planted to control the weeds.
Mosquitoes breed  in stagnat ponds.	Fishes which eat the mosquito larvae are reared in the ponds
Aphids that feed on crops	Ladybirds are used to eat up the aphids (Figure 4.11(c)).

Figure 4.11 Examples of biological control

 

8. Biological control is more effective in controlling pests because it does not damage the ecosystems although its effects are slower.

9. It should be noted that the organism that is used to control the pest must be specific to the pest. It must target the specific pest and no other species.

10. What would happen if other species are also killed other than the targeted species? The implication can be serious. For example. in Australia, a type of toad was introduced to control the beetle that damaged sugar-cane plantations. The toad also killed non-target organisms like the possum, a primitive mammal. The death of possums caused an imbalance in the ecosystem.

11 In Malaysia, an increase in the number of crows has posed a problem to people living in Klang. Crows were used to control the hawk moths. With the available food scraps in Klang, the crow population increased and became a nuisance. The state government, the relevant authorities and the non-government agencies (NGOs) have launched several approaches like

• culling the crows by shooting them

• trimming big trees so as to reduce the number of branches and leaves

• clearing food scraps around coffee shops and hawker centres everyday

• ensuring refuse bins are closed

4.3 Food Webs 

1. A food chain demonstrates the feeding relationship between living organisms in an ecosystem.

2.It consists of a sequence of organisms starting with the producer (green plant), followed by the primary consumer, the secondary consumer and usually ending with the tertiary consumer.

3. In any ecosystem, animals or consumers will eat more than one type of food. For example, snakes not only eat frogs but also birds and rats.

4 These food alternatives form a food web as shown in Figure 4.12. To make the food web more complex, we can extend the food web as in Figure 4.13.

 

5 The food web in Figure 4.13 is made up of three food chains: (a), (b) and (c).

6 A food web is made up of several food chains. These individual food chains are interlinked in a complex way to provide a more complete picture of how animals feed.

7 A food web helps to maintain a balanced ecosystem by regulating the number of organisms at each level










 

Grass        →	Grasshopper            →	Toad    →	Snake     →	Hawk     →	Bacteria of decay
In general
Autotrophs (Producers)      →	Herbivores (Primary Consumers)          →	Carnivores (Secondary, tertiary, etc. consumers)                    →			Decomposers