BIOLOGY FORM 4 NOTES CHAPTER 8 : DYNAMIC ECOSYSTEM8.1 THE ABIOTIC AND BIOTIC COMPONENTS OF THE ENVIRONMENTEcology = the scientific study of the interactions of living organisms with other living organisms and with physical environment

Producers autotrophs- green plants synthesis organic substances / food from nutrients & sunlightConsumers heterotrophs acquire energy & nutrient by feeding on other organisms primary consumers secondary consumers tertiary consumersDecomposers microorganisms-bacteria / fungi break down waste products and dead bodies of other organisms into simple substancespH affects the distribution of organismsLight intensity affects the distribution and growths of plants and distribution of animalsHumidity affects the rate of water loss by plants and animalsTemperature affects the physiological activities of plants and animalsTopography altitude- the height gradient- steepness of a slope aspect- windward / leeward slope

Microclimate climate in microhabitat affects the number and distribution of organisms

FOOD CHAIN, FOOD WEB AND TROPHIC LEVELSFood chain = a sequences of organisms through which energy is transferred. starts with a producer and ends with a top consumer. Grass Grasshoppers Frogs Snakes (producers) (primary (secondary (tertiary consumers) consumers) consumers) 1st 2nd 3rd 4th trophic level trophic level trophic level trophic level

Food web = Different food chains link up to form a food web.

Tropics Level The tropics level of an organism is its position in a food chain. When a primary consumer feeds on a producer, only 10% of the original energy in producer is incorporated into the primary consumer and 90% of it is lost as heat. Similarly, when a primary consumer is eaten by a secondary consumer, only 10% of the original energy in producer is incorporated into the secondary consumer and 90% of it is lost as heat.

THE INTERACTION BETWEEN BIOTIC COMPONENTS IN REACTION TO FEEDING(i)Symbiosis(ii)Saprophytism(iii)Prey-predators

(ii) Saprophytism = a type of interaction in which living organisms obtain food fromdead and decaying organic matter the organisms secretes enzymes to digest dead organisms before absorbing the digested compound. Examples:(a)Saprophyte any plants that depends fully on dead organisms for food mushroom, fungi(b) Saprozoite any animal that obtains food from dead organisms Earthworm, paramecium, saprophytic bacteria

(iii) Prey-predator = an interaction between two organisms in which an organism (the prey) ishuntedand killed by the other (the predator) for food. helps to control the population of organisms in an ecosystem and maintain the balance of the nature

a) At the beginning, the rats (prey) have plenty of food, and they survive to breed and their population rises.b) Increases in the population of rats means more food for owls (predator), so they survive to breed and their population rises.c) With more owls, the population of rats goes down because the rats are eaten by the owls.d) With less rats, fewer owls survive to breed and their population declines. Some of the owls migrate to other places.e) With fewer owls, more rats will survive to breed and their population rises, so the cycle repeats itself.f) The predator-prey cycles are self regulating and keep the populations of both predator and prey in a dynamic equilibrium.

INTERACTION BETWEEN BIOTIC COMPONENTS IN REACTION TO COMPETITIONCompetition = an interaction between organisms living together in a habitat and competing for limited resourcesa. b. foodc. shelter d. breeding matese. lightf. nutrientsg. water h. space

Two type of competition:(i) Intraspecific Competition a competiton between individuals of thesame species The two species ofparamecium aureliaandparamecium caudatumare cultured in two separate culture dishes but given the same amount of food. The population ofparamecium aureliaandparamecium caudatumin each culture dish increased and then reached a maximum.(ii)Interspecific Competition a competiton between individuals oftwoormore different species in this type of competition, the species that loses: either dies, or is forced to move out of the habitat wins : stays and become dominant in that habitat

Example : Whenparamecium aureliaandparamecium caudatumare cultured in a same culture dish with the fixed amount of food and space,paramecium caudatumlost out toparamecium aureliain this competition for food and space. The population ofparamecium caudatuminitially rose and then decreased while the population ofparamecium aureliarose and finally became the dominant species.

8.2 COLONISATION AND SUCCESSION IN AN ECOSYSTEM8.2.1EcosystemAn ecosystem = a system formed by the interactions of a community of organisms with their non-living environment and function as a unit. It is a dynamic system where all the biotic components are in balance with one another and with the abiotic components.8.2.2Niche, Habitat, Community And Population Of An Ecosystem1.Niche A niche is the role that an organism plays in the ecosystem. Is the way of life of an organism in its natural surrounding Example: the niche of a grasshopper it hops and flies around the grass field, feeds on grass, mates and becomes food for others.2.Habitat A habitat is a place where an organism lives.3.Community A community consists of all the different populations of plants and animals living together and interacting within a defined area of habitat.4.Population A population is a group of organisms of the same species living in the same habitat at the same time.8.2.3Colonization and Succession1.Colonization is a process whereby living organisms move into the newly formed area which is completely devoid of life.2.The species organisms that colonize the newly formed area called pioneer species.3.Characteristics of pioneer species: usually hardy plants Able to survive on dry or nutrient-poor soil or sand.4.Succession of a habitat take places when species move into the modified environment, compete and gradually replace the pioneer species.5.Successor species grow larger than the pioneer species, thus cutting off light, nutrients and space of pioneer species and finally eliminating the pioneers.6.The succession process continues gradually. Finally after many levels of succession, a climax community (a balanced and stable community) forms.8.2.1.1Colonisation and Succession In A PondPioneer Stagea.Phytoplankton, zooplankton and submerged aquatic plants (Hydrilla, Utricularia and Cabomba) are the pioneers.b.These submerged aquatic plants have long fibrous roots to penetrate the soil and to absorb nutrients.c.When the pioneer plants die and decompose, the organic matter settles to the bottom of the pond. This organic matter, together with the eroded soil from the bank of the pond gradually settles to the bottom, making the pond shallower and more suitable for floating plants.

Succession by aquatic floating plantsd.Floating plants (Pistia, Eichornia and Lemna) gradually multiply and cover the surface of the pond and prevent sunlight from entering it.e.This causes the submerged aquatic plants to die as they cannot carry out photosynthesis.f.The dead plants decompose and add on to the layer of organic matter at the bottom of the pond.g.The dead plants together with the eroded soil from the bank of the pond gradually raise the floor of the pond, making it too swallow for the floating plants.

Succession by emergent (amphibious) plantsh.Emergent plants (Firmbristylis sp, Scirpus sp and Cyperus sp) which can live in water and on dry land succeed the floating plants.i.The emergent plants multiply and change the habitat of the pond.j.Some of the emergent plants die, their decomposed remains add on to the sediment making the pond even swallower and eventually dry it up.

Succession by land plantsk.Land plants (creepers, herbaceous and woody plants) replace the emergent plants and gradually from a jungle

Climax communityl.The process of succession will stop when a level of balance is achieved.m.The climax community takes a few hundred years to form.

8.2.3.2 Colonisation and Succession InMangroveSwamp

Avicennia sp. and Sonneratia sp. ZoneRhizophora sp. zoneBruguiera sp. zone

Pionner stage:

Avicennia sp. and Sonneratia sp. are pioneers.Adaptations:a) The pioneer plants have vertical aerial roots known as pneumatophores.b) At the end of the pneumatophores are aerenchyma tissues for gaseous exchange.

Succession by Rhizophora sp.:Pneumatophores trap mud and organic sediment and the amount of soil increases and becomes more compact and firm as time passes, making the habitat more suitable for Rhizophora sp.Adaptations:a) Rhizophora sp. has stilt roots (prop roots) for support in the soft and unstable mud.b) The stilt roots help the plants to breathe as they are permeable to gas.c) Have viviparous seedling that start to germinate while still being attached to the parent on the tree branch.d) Hydathodes (found on the edges of the leaves to get rid of excess salt from the tree through guttation)e) Thick and fleshy leaves (to store water)f) Waxy cuticle (protects the epidermis from excessive losing of water)Succession by Bruguiera sp.:The stilt roots of Rhizophora sp. trap the deposit floating debris, wood, sand and mud brought in by the tide.Over time, these deposition creates firmer soil, raises the ground level and makes it drier, making the habitat more suitable for Bruguiera sp.Adaptations:a) Bruguiera sp. has buttress roots and pneumatophores that are knee-shaped.b) The buttress roots form loops that protrude the soil, providing strong support and trapping more silt.c) Other adaptations: viviparous seedling Hydathodes Thick and fleshy leaves Waxy cuticles

8.2POPULATION ECOLOGY8.2.1What is population ecology?1. Population ecology: = the study of the relationship between(a) different populations(b) populations and the environment

2. Measuring the population size: (a) plants by quadrat sampling technique (b) animals by the capture, mark, release and recapture technique.

8.2.2Quadrat Sampling Technique

1.Procedure:

1.The distribution of organisms can be determined by:

8.2.1Capture, Mark, Release And Recapture Technique

1.Procedure:

1.Populaton size:

Formula:_____________________________________________________

1.Assumptions:(a)The marked individuals can mix randomly in the population before the second sample is taken;(b)Marked and unmarked animals in the sample are caught at random.(c)The marks on the animals of the first sample cannot be deleted easily and are no danger on the sampled animals.(d)There are no predators of the sampled animals in the area surveryed.(e)The population sampled is stable and does not experience any sudden changes.(f)The mortility rate and the birth rate are about the same.

8.2.1The abiotic factors which influence the distribution of an organism.

a.The distribution of an organism is influenced by abiotic factors such as:(a) light intensity (b) temperature(c) humidity (d) pH(e) aspect

Experiment:To study the effect of change pH on a plant population.

Objective: To study the effect of change pH on the population growth rate ofLemnasp.

Problem statement: What is the effect of change pH on the population growth rate ofLemnasp?

Hypothesis: In a neutral medium the population growth rate ofLemnasp. is the fastest.

Variables:Manipulated variable: pH of waterResponding variable: Number ofLemnasp.Fixed variable: Light intensity

Materials: Dilute hydrochloric acid, dilute sodium hydroxide solution, pond water, distilled water andLemnasp.

Apparatus: Beakers

Procedure:1.Nine beakers are labelled as A1,A2,A3,B1,B2,B3 and C1, C2, C3..2.Each beaker is filled with 200 ml of pond water.3.10 ml of dilute hydrochloric acid is poured into beaker A1,A2 and A3.4.10 ml of dilute sodium hydroxide solution is poured into beaker B1,B2 and B3.5.10 ml of distilled water is poured into beaker C1,C2 and C3.6.20Lemnasp. plants are put into each beaker.7.Each beaker is placed in an area of evenly distributed light.8.After 5 days, the number ofLemnasp. plant in each beaker is counted.9.The result is recorded in a table.10.The average reading of number of plants at the end of experiment is taken.

Precautional step:1.Make sure all the beakers are exposed to the same light intensity.

Presentation of data

BeakerCondition (pH)Number of plants

Beginning of experimentEnd of experiment

A1Acidic

A2

A3

B1Alkaline

B2

B3

C1Neutral

C2

C3

Conclusion:The population growth rate ofLemnasp. is affected by a change in pH.Lemnasp. grows best in a neutral environment. The hypothesis is accepted.

8.2BIODIVERSITY

8.2.1What is biodiversity?

1.Biodiversity:= the diverse variety of plants and animals in the different ecosystem on the earth.

8.2.2Classification of organisms

KingdomCharacteristicsExamples

Monera / Prokaryotae

Protista

Fungi

Plantae

Animalia

The hierarchy in the classification of organism

The naming of organisms or biological nomenclature is based on the Linnaeus binomial system.

In this system, each organism has two names in Latin.The first name: begins with capital letter, refers to the name of genusThe second name: begins with small letter, refers to the name of species.

Example: the scientific name of humans isHomo sapiensorHomo sapiens.

Scientific names of some animals and plants:Common nameScientific name

Durian

Hibiscus

Maize

Frog

Fruit fly

8.2.1The importance of biodiversity

1.Source of medicinea.Plants in tropical provides raw material for medicine, for example, in the treatment of cancer.

2.Shelter and foodb.People and animals depend on their ecosystem for shelter, food and basic needs.

3.Environmental servicesc.Environmental services, such as nitrogen cycle, pollination, and regulation of atmospheric temperature are provided due to the diversity of plants and animals, and the interactions between various organisms.

4.Economic resourcesd.Eco-tourism contributes to the economy.e.Timber, rubber and organic oils plays important roles in economy.

8.2THE IMPACT OF MICROORGANISMS

8.2.1Types of microorganisms

1.A microorganism (or microbe) is an organism (unicellular animal or plant) that is very small and cannot be seen by unaided eye. It can only be seen with the help of a microscope.

2.The various type of microorganisms

Types of microorganisms

CharacteristicsExamples

Bacteria

Unicellular organismsHave cell wallDo not have nuclear membraneAsexual reproduction through binary fusionForm spores in unfavorable condition4 ways of nutrition:(a)Photosynthesis(b)Chemosynthesis(c)Saprophytic(d)Parasitic

LactobacillusStreptococcusE. coli

AlgaeSemi-aquatic plant, autotrophs.Have chlorophyll and chloroplastNo leaves, stems or roots.The cell walls are made of celluloseLive in moist and extremely low light areaSexual and asexual reproduction through spores or separation of vegetative cell.Carry out aerobic respiration.

Phytoplankton,Spirogyra sp.

Types of microorganisms

CharacteristicsExamples

FungiUnicellular or multicellular plant.HeterotrophsDo not have chlorophyll, leaves, stems or roots.The cell walls are made of chitinSexual and asexual reproduction through spores and buddingLive in dark and moist area or upon the death or decaying organism.

Mucor sp.Yeast

ProtozoaAquatic unicellular organismHave a nucleus, cytoplasm, and a plasma membraneCarry out life processes, such as respiration, reproduction and excretion.Sexual and asexual reproduction through spores and budding or binary fusion

Paramecium,Amoeba,Euglena

VirusSmallest microorganism, can only be seen under electronic microscopeNon-living cell because it cannot survive or reproduce on its own outside the cells of its host.Depend on host for nutrition, reproduction and respiration.Have two parts:(a)Inner core composed of nucleic acid: DNA or RNA(b)Outer capsid of proteinCan be purified or crytallised

Influenza virus,Poliomyelitis virus,Tobacco mosaic virus

8.2.1The effects of abiotic components on the activity of microorganisms

1.The activity of microorganisms are affected by:

(a)Nutrients and watera.Microorganisms need water and nutrient for reproduction and grow.b.Without water, the microorganisms will die or form spores.

(b)pHc.Each species of microorganisms has its own optimum pH.d.Most bacteria prefer slightly alkaline conditions (pH 7.4), while yeast and protozoa prefer acidic conditions (pH 4.5 4.0).

(c)Temperaturee.Most a microorganisms are inactive in low temperature.f.The optimum temperature for microorganisms is between 350C 400Cg.Beyond 600C, the growth of the microorganisms is inhibited.h.Microorganisms and their spores can only be destroyed when they are sterilized at 1210C.

(d)Light intensityi.Microorganisms prefer dark or low light intensities.j.High intensities of sun light or ultraviolet rays can kill microorganisms.k.Photosynthetic algae and bacteria are more active under high light intensities to carry out photosynthesis.

(e)Presence or absence of oxygen

l.most microorganism (aerobes) require oxygen for respiration and metabolism.m.Certain bacteria and fungi are facultative anaerobes, they are able to grow in either presence or absence of oxygen.n.Obligate anaerobes can only survive in the absence of oxygen.

The role of Useful Microorganisms in the Ecosystem

AreaUsage / Examples

DigestionThe alimentary canal of herbivores, contain bacteria which produces cellulose enzyme to digest cellulose.The digestion of cellulose in termite is done by protozoa that produces cellulose enzyme to digest cellulose.In human colon, some mutualistic bacteria can synthesis Vitamin B 12 (to prevent anaemia and Vitamin K for blood clotting)

MedicineFungi are used in the production of antibiotics.oExample: Penicillin produced by fungusPenicillium natotumis used to treat diseases such as gonorrhoea, syphlilis and lung infection.Vaccines which formed by weakened or dead bacteria or viruses are used to stimulate the bodys immunity agaist diseases.oExample: B.C.G. vaccine is used to produce immunity agaist TB.

DecompositionBacteria and saprophytic fungi decompose the dead animals and plants into simple compounds and elements.Microorganisms are used to treat waste from industries.Decomposers play an importance role in natural cycles of elements such as carbon cycle and nitrogen cycle.a.the decaying process returns elements such as carbon, nitrogen and sulphur back to the soil.b.These substances are then reabsorbed by plants and move through the ecosystem again.

Industry1.Production of alcohola.Yeast is used to produce alcohol through fermentation of sugar, starch or grains.

2.Production of vinegara.The bacterium,Acetobector, acts on the alcohol to produce vinegar.

3.Making of breada.Yeast is used to raise the dough.

4.Production of buttera.The bacteria split the proteins from the fat of the cream to enable the fat molecules to stick together when the mixture is stirred strongly.

5.Production of fermented milka.The bacteria,Lactobacillussp. andStreptococcussp. together with yeast act on thick milk to produce fermented milk.

6.Production of vitaminsa.Microorganisms such as yeast can be used to produce vitamin B2 and vitamin D.

7.Textile industrya.Bacteria are used to decompose the soft plant tissues leaving the plant fibres.

The Nitrogen CycleNitrosomonassp. andNitrococcussp. convert ammonia into nitrites.Nitrobactersp. converts nitrites into nitrates that go into the soil, which are absorbed by the roots of plants.RhizobiumandAzotobactersp. converts nitrogen into nitrates.

There are three main processes which involve the activity of microorganism in nitrogen cycle.(a)decomposition(b)nitrogen fixation(c)denitrification

Decompositiona.organic matter such as animal carcasses, dead plants and animal wastes are converted by the saprophytic organism (bacteria and fungi) into ammonia.b.Ammonia is converted into nitrites byNitrosomonassp. andNitrococcussp.c.Nitrobactersp. then converts nitrites into nitrates that go into the soil, which are absorbed by the roots of plants and converted into proteins.

Nitrogen fixationd.Nitrogen fixation is a process whereby atmospheric nitrogen is converted into nitrates.e.It can be carried out by:(a)industry fixation(b)biological fixation(c)atmospheric fixation

f.Industry fixationa.Ammonia nitrate is produced through nitrogen-based fertilizer

g.Biological fixationa.Biological fixation is carried out by nitrogen-fixing bacteria and blue-green algaeb.Azotobactersp. andClostridiumsp. (free-living bacteria in the soil) convert nitrogen into nitrates.c.Rhizobiumthat lives in the root nodules of leguminous plants, also converting nitrogen gas into nitrates.d.Noctocsp. is a blue-green algae in the soil that fixes nitrogen gas into nitrates.

h.Atmospheric fixationa.During thunderstorm, lightning causes nitrogen gas and oxygen gas to combine to produce nitrogen dioxide.b.The nitrogen dioxide gas dissolves in rain water to form nitrous acid and nitric acid.c.These acids react with bases found in the soil to form nitrates.

Denitrificationi.The denitrifying bacteria reduce nitrates to free nitrogen and oxygen gas.j.The nitrogen gas returns to atmosphere while oxygen is used by the denitrifying bacteria for respiration.

8.2.1The effects of harmful microorganismsk.There are many microorganisms that cause harmful effects. These include:(a)causing infections and diseases(b)spoilage of food, clothing and other sustances

l.Pathogens are organisms or viruses that can invade the body of living hosts and cause diseases.

8.2.2How diseases spread

m.Diseases are transmitted in five ways, through(a)AirThrough cough, sneezes, talk or breatheExamples of diseases: TB, diphtheria and viral diseases such as pneumonia, influenza, cold and mumpsWays to prevent:(i)refrain from spitting(ii)refrain from coughing near other people(iii)use handkerchief or tissue paper when sneezing

(b)FoodThrough dirty hands, exposed food, pests, raw foodExamples of diseases: typhoid, amoebic dysentery, cholera, worm infectionWays to prevent:(i)Cooking food(ii)Covering food(iii)Keeping food in refrigerator

(c)WaterThrough contaminated waterExamples of diseases: typhoid, amoebic dysentery, choleraWays to prevent:(i)Boiling the drinking water(ii)Chlorinating the water in the reservoirs

(d)Physical contactThrough direct contact, indirect contact, sexual intercourse and cutsExamples of diseases: ringworm, TB, measles, chickenpox, sexually transmitted diseases (gonorrhoea, syphilis and AIDS)Ways to prevent:(i)Do not share personal belongings(ii)Adopt hygienic habits(iii)Abstain from immoral activities and drug abuse(iv)Abstain from immoral sexual relationships

(e)VectorsThrough insects (mosquito, housefly and lice), through animals (rats, dogs)Examples of diseases: Malaria (byAnophelessp. mosquito), Dengue fever (byAedessp. mosquito), Cholera (by housefly)

8.2.3Methods of controlling pathogens

1.Antibioticsn.Antibiotics are chemical substances produced by certain microorganisms.o.Function: To kill and inhibit the growth of bacteria and fungi.p.Examples:(i)Penicillin is used to treat diseases caused by bacteria, such as syphilis(ii)Streptomycin is used to treat diseases such as TB.

2. Antiseptics- Antiseptics are chemical used to kill and inhibit the growth of microorganisms on cuts or wound.- Examples: iodine solution, potassium permanganate solution, acriflavin, alcohol

3. Disinfectants- Disinfectants are chemical solution used to kill microorganisms on the surface of floors, buildings, furniture, toilet bowls and clothing.- Examples:Phenol, carbolic acid, creasol, and formaldehyde

2.Vaccinesq.Vaccines are weakened or killed viruses and bacteria which injected to the body to stimulate the production of antibodies.r.Examples:BCG vaccine is used to immunize a person against TB.

8.2.1The use of microorganism in biotechnology

1.Cleaning of oil spills

b.Genetically engineered bacteria are used in cleaning oil spills.c.The bacteria together with a nutrient solution are sprayed onto the oil.d.The bacteria break down the oil into less harmful substances such as carbon dioxide and water.

2. Management of waste

e.Toxic and non-toxic industrial wastes are converted by microorganisms into safe substances for the environment.f.Certain species of bacteria are used to decompose compounds of hydrocarbons and sulphur in toxic solution and in septic tanks.g.Degrading fungi are used to convert wood pulp and other useful products.

3. Processing of food

h.Yeast is used in the making of bread and wine.i.Yogurt is made from the fermentation of milk, using bacteria such asLactobacillussp. adStreptococcussp.

4. Production of bioplastics

j.Bioplastic is biodegradable plastic which can be easily decomposed.k.Bioplastic is produced by culturing bacteria in a nutrient-rich medium. Bacteria in the nutrient medium react by synthesizing a natural plastic.l.The bioplastic is extracted from the bacteria to make bags, bottles, spoons and forks.

5. Production of energy from biomass

m.Anaerobic bacteria are used to break down organic waste to produce biogas and gasohol.n.The biogas produced can be used as domestic fuel or fuel for vehicles.