ECOLOGYTHE TERMINOLOGY:

• Species• Population• Community• Ecosystem• Habitat• Biosphere

• Biotic environment• Abiotic environment

SPECIES → POPULATION → COMMUNITY → ECOSYSTEM → BIOSPHERE

THE PHYSICAL ENVIRONMENT

•Light

•Temperature

•Water

•Oxygen

•Salinity (salt concentration)

•pH (acidity or alkalinity)

PRODUCERS

CONSUMERS

DECOMPOSERS

1. LIGHT•PLANTS need light to make their food.

•Some plants show adaptations to reach for light such as climbers.

•Most of the animals need sunlight.

•Some live in dark such as bats.

•Some are nocturnal: search for food in the night.

2. TEMPERATURE•Affects the physiological activities of plants and animals.

•A fall in temperature = decrease in the metabolic activities of the organism

•Find it difficult to tolerate extremes of temperature: extreme hot extreme cold.

•Flowering plants have special adaptations to survive through the hot, dry season or winter by:1. Underground storage organs (tubers, corms, bulbs etc)2. Shedding of leaves to reduce water loss3. Formation of seeds just before the beginning of

unfavourable seasons.

• Polar regions have their characteristic animals such as polar bears, penguins and seals. These animals have thick layer of fat under their skin so as to protect them from extreme cold.

3. WATER•Rainfall determines the amount of water

•Water is the most important factor in the distribution of plants and animals.

•No organism can survive without water for long. Only some are adapted like camels, which can store water, so as to survive under conditions where there is limited amount of water.

1. Xerophytes2. Hydrophytes

1. XEROPHYTES

• Xerophytes are those plants which can live in conditions of prolonged drought in their habitat.

• Mechanism of survival: 1. reduce rate of transpiration (loss of water) by shedding

young leaves.2. Stems become fleshy, storing up water.3. The stems are green and take over the function of

photosynthesis from the leaves.

A. Casuarina: • Leaves reduced to tiny sheaths at the nodes.• Food manufactured by the long green stems• Stomata lie in grooves protected by minute hairs.

B. MARRAM GRASS• leaves have sunken stomata that lie in grooves in the upper surface.

•Grooves bear many tiny hairs which trap water vapour diffusing out of stomata, which leads to increased humidity around the stomata and so reduces the rate of transpiration.

•When leaves loose too much water, they roll up reducing the surface area exposed.

2. HYDROPHYTES

•Live in water or very wet places.

1. Completely submerged (Hydrilla)2. Partially submerged (water lily)3. Free floating (water hyacinth)

ADAPTATIONS:4. Stems have air spaces so as to help plant float5. Upper surface of leaf protected by water proof cuticle to

prevent water form blocking the stomata.

PNEUMATOPHORES

•Have their roots buried in oxygen-poor mud, but special breathing roots called pneumatophores arise from the root system and project above the mud surface.

•Pneumatophores bear openings thorugh which oxygen can pass downwards to the whole root system

IN ANIMALS:

•Gills for oxygen absorption•Webbed toes in frogs•Fins in fishes

4. OXYGENANIMALS ARE EITHER:

•Aerobes•Anaerobes

Aerobes need special adaptations to survive in low oxygen in atmosphere:

•Pneumatophores in mangroves•Fishes living in water of low oxygen concentration are usually air-breathers and come to the surface to gulp air.

5. SALINITY(salt concentraion)Salinity of the water is a very important factor for the aquatic organisms

•Either adapted for life in very salty water such as sea water.•Or in streams and freshwater ponds where the salt concentration is low. FRESH WATER

•Salt conc. Of the cytoplasmic contents of FRESHWATER

ORGANISMS is higher than the surrounding water, hence water

enters these organisms by osmosis.

•Their cells don’t burst with water because of their rigid cellulose

cell walls.

•Have contractile vacoule to remove excess of water (amoeba)

•Fishes possess water-proof coat consisting of closely-fitting

scales covered by a slimy mucous material.

SEA WATER

•Animals lose water by osmosis as the sea water contains a higher concentration of salt than the tissue cells.•Saltwater fish has a slimy scaly skin which reduces the rate of water loss.

AQUATIC ORGANISMS ARE HIGHLY SPECIALIZED:

•They can survive only in their own environment.•Many fresh water animals cannot live in sea water and vice versa.

•Starfishes and coral reefs are only found in sea. Are not found even in BRACKISH water (water where fresh and sea water mix)

•Animals and plants living in brackish water are adapted to tolerate wide fluctuations in salt concentration.

6. pH (acidity or alkalinity)pH value of soil water OR water of the freshwater ponds or sea is very important.

•Sensitive to pH of water and may be killed if the pH changes appreciably.•Sea water is alkaline with pH 8. And this pH has little variation.

•In Freshwater ponds and streams, pH varies from region to region.•Changes in pH occur, especially if pH of water depends on the amount of bicarbonates present in it.•In strong daylight, photosynthesis of plants uses up carbon dioxide in the water, making the water more alkaline.•During the night, photosynthesis ceases and carbon dioxide produced as a result of respiration makes the water more acidic.•For most freshwater organisms, neutral or nearly neutral water is best.

FOOD CHAINSFOOD WEBS

•Energy enters an ecosystem from outside – SUN•And flows through it in a non-cyclic manner. That’s why energy has to be constantly supplied to an ecosystem.

•Materials are not supplied fro m outside.•Obtained from the physical environment and flow through the ecosystem in a cyclic manner.

•In a balanced ecosystem, materials are never lost and are continually recycled.

A series of organisms through which energy is transferred in material form (food) constitutes a food

chain.

Each level in a food chain is called a TROPHIC LEVEL.

HOW MATERIALS ARE RECYCLED!!!

ENERGY TRANSFER IS INEFFICIENT

•The amount of energy that is passed on in a food chain is reduced at every step.•Energy can be neither created nor destroyed, it is not lost but is converted into some other form.•During respiration, some energy is transferred to the environment as heat.

FOOD WEB

•Little energy is transferred from the base to the top of a food chain, a top carnivore must eat many herbivores.

•These herbivores are probably not all of the same species.

•In turn, each herbivore is likely to feed on many different plant species.

•These different relationships are shown linked to each other in a food web.

•The more complicated a food web, the more stable a community is.

HAWK

STARLING OWL

SNAILS WOODLICE WORMS RATS MICE SQUIRRELS

FALLEN LEAVES LIVING LEAVES GRASSES SEEDS

TROPHIC LEVELTer.Consumer

SecondaryConsumer

PrimaryConsumer

Producers

FOREST FOOD WEB

FEEDING RELATIONSHIPSPYRAMIDS OF NUMBERS

PYRAMIDS OF BIOMASS

PYRAMIDS OF ENERGY

1. PYRAMID OF NUMBERSA diagrammatic representation of the number of different organisms at each trophic level in an ecosystem at any one time!!!

Note: 1. The number of organisms at any trophic level is

represented by the length or the area of the rectangle.2. Moving up the pyramid, the number of organisms

generally DECREASES , but the size of each individual INCREASES.

2. PYRAMID OF BIOMASSBIOMASS is the number of individuals x mass of each individual.

Pyramid of biomass represents the biomass at each trophic level at any one time.

GRASS → RABBIT → SNAKE → HAWK

Lets suppose:

•10 hawks in an area and each hawk feeds on 2 snake every day.•Each snake eats one rabbit every day.•Each rabbit eats 20 grass plants every day.

Construct a PYRAMID OF NUMBERS .

The pyramid of biomass is constructed based on the dry mass of organisms in each trophic level at any one time. This is called the STANDING MASS of organisms.

HOW CAN WE CONSTRUCT A PYRAMID OF BIOMASS???

•Lets suppose there are 1000 rabbits in a given area at one time.•We can determine the biomass of rabbits at that time as follows.

1. Dry 10 rabbits in an oven at 1000C until a constant mass is obtained. Lets say the dry mass of 10 rabbits is A g. the biomass of 1000 rabbits will be 100A g.

2. Repeat step one for all the other trophic levels.

3. Construct a pyramid of biomass using the information obtained in steps 1 and 2.

VARIATIONS IN ECOLOGICAL PYRAMIDS……

Mostly they are pyramid shaped, but there are impostant exceptions.

1. A PYRAMID OF NUMBERS MAY E UPSIDE DOWN if:

• Organisms of one trophic level are parasitic on organisms of another trophic level.

• Many small organisms of one trophic level feed on a large organism of another trophic level

EXAMPLE: tree → aphid → protozoa

In this case the pyramid of numbers is inverted.

•Bottom of the pyramid is one tree.

•Many aphids are parasitic on the tree.

•Many protozoa are parasitic on the aphids.

Pyramid of biomass is going to be the same, ie, broad at the bottom and narrow towards the apex. This is because one tree has comparatively large biomass.

2. Pyramid of biomass for rapidly reproducing organisms are also not pyramid shaped.

•As the pyramid of biomass is based on standing mass, it does not take into account the rate of reproduction of organisms.

•This is a disadvantage when considering organisms that reproduce rapidly.

PHYTOPLANKTON → ZOOPLANKTON → SMALL FISH → LARGE FISH

•Phytoplanktons are microscopic , plant-like organisms which make food through photosynthesis.

•Zooplanktons are microscopic primary consumers, feeding of phytoplanktons.

•Biomass of phytoplankton is smaller than the zooplankton which is not possible.

•Rate of reproduction of phytoplankton is fast enough to replace the organisms that were eaten by zooplankton.

3. PYRAMID OF ENERGYThe total energy in the various trophic levels of a food chain can be represented in the form of a pyramid.

•We need to determine the total energy content of each trophic level over a period of time.•We should take into consideration the rate at which the organisms reproduce.•The average energy content of each trophic level can then be calculated using special techniques.•Then we can construct the pyramid of energy.

THE PYRAMID OF ENERGY IS THUS CONSTRUCTED BASED ON THE TOTAL ENERGY LEVEL IN EACH TROPHIC LEVEL OVER A CERTAIN PERIOD OF TIME, FOR EXAMPLE, ONE

YEAR

A LOT OF ENERGY IS LOST TO THE ENVIRONMENT AS FOOD IS TRANSFERRED FROM ONE TROPHIC LEVEL TO

THE NEXT

It may be lost to the environment:

1. As heat during respiration at every trophic level.2. In uneaten body parts3. Through undigested matter egested by consumers.4. Through waste products excreted by consumers, eg. Urea.

Heat energy is wasted energy since it cannot be recycled in any way in the ecosystem.

• More and more energy is lost as we go down a food chain. • The total energy level is highest at the 1st trophic level.• Hence, the enrgy of pyramid is always broad at the base

and narrow towards the top.

We can assume that about 90% of the energy is lost when it is transferred from one trophic level to the next.

The greatest amount of energy is lost during transfer of energy from producer to primary consumer.

PYRAMID OF BIOMASS PYRAMID OF ENERGY

1. Related to the biomass of the organisms

1. Related to the energy content of the organisms

2. Constructed based on the biomass at any given time

2. Constructed based on energy content over a period of time

3. Does not consider the rate of reproduction of organisms

3. Takes in consideration the rate of reproduction of organisms

NON-CYCLIC ENERGYFLOW IN ECOSYSTEM

•The first source of energy in an ecosystem is the sun.•Some of it is lost to the environment as heat.•Energy lost as heat cant be recycled.•Hence, energy has to be constantly supplied to the ecosystem.

•In an ecosystem, energy does not flow in a cycle. Energy flow is non-cyclic or linear.

1. In an ecosystem, the ultimate source of energy is the sun.

2. Light energy absorbed by chlorophyll in producers is converted into chemical energy during photosynthesis.

3. Energy in the producers is passed from one trophic level to another by feeding. (holozoic nutrition)

4. The flow of energy through the ecosystem is non-cyclic. Energy is released as heat to the environment as it flows through the ecosystem. This energy can not be recycled and returned to the same system.

5. Dead organisms and egested and excreted materials contain trapped chemical energy. Some of this energy is released by the activity of decomposers. Decomposers use some of this energy for their needs whereas, the rest is lost as heat.

ALL the energy that enters the BIOTIC part of the ecosystem is lost as heat energy. Living organisms can not use heat

energy to do work. They can ONLY use LIGHT AND CHEMICAL ENERGY.

NUTRIENT CYCLINGEssential nutrients:•Carbon•Oxygen•Nitrogen•Water

Released back into the soil when organisms die.

•Decomposers break down dead organisms•The materials locked up in these dead organisms are returned to the physical environment to be again used up by green plants.•That’s how nutrients are never lost in a balanced ecosystem.•They are continually recycled.

Physical processes Biological processesChemical processes

1. CARBON CYCLE

Living organisms require carbon containing compounds as:

1. A source of energy, when carbon-containing compounds are oxidized during respiration. (carbohydrates and fats)

2. Raw materials for the growth of cells (fats and proteins)

•Carbon is constantly being removed from and released into the environment in the form of CO2

•CO2 concentration in the environment remains relatively constant.

IMPORTANCE:

1. Ensures a continuous supply of carbon dioxide for plants.2. Enables energy to flow through the ecosystems. Carbon

compounds carry the trapped solar energy from organism to organism in the food chains of an ecosystem.

REMOVAL OF CARBON DIOXIDE FROM THE ENVIRONMENT

During photosynthesis, green plants absorb CO2 from the atmosphere and use it to manufacture carbohydrates, for

example: glucose

Glucose may be changed to other organic compounds such as fats, amino acids and proteins.

When animals feed on green plants, the carbon compounds become part

of the bodies of these animals.

The carbon compounds may also be preserved in fossil fuels such as coal,

natural gas and oil.(This happens in conditions of low temperature , Oxygen and

low pH, which prevent the action of decomposers. Carbon compounds become LOCKED

UP in fossil fuels)

RELEASE OF CARBON DIOXIDE FROM THE ENVIRONMENT

RESPIRATION: When living organisms respire, Carbon compounds are broken down in their bodies and CO2 is released into the environment.

COMBUSTION: When fossil fuels like coal and natural gas are burnt, or undergo combustion, carbon compounds preserved in fossil fuels are broken down and CO2 is released into the environment.

DECAY: When organisms die, their bodies decay into simpler substances by decomposers. CO2 is one of the simplest substances released into the environment during decay. Also, some of the simple substances are absorbed by decomposers and become a part of their bodies. When the decomposers respire, CO2 is released. Methanobacterium, utilizes acetate and produces methane and carbon dioxide.

1. NITROGEN CYCLE

WHY NITROGEN IS ESSENTIAL?

•Plants need nitrogen for the synthesis of proteins and other compounds, including the DNA and vitamins.

•Nitrogen gas makes up about 80% of the Earth’s atmosphere, but plants do not have the enzymes necessary to use the nitrogen directly – instead they must absorb it as NITRATE.

•Nitrate is formed by 2 sets of processes carried out by microorganisms:

1. Nitrogen fixation2. Nitrification

NITROGEN FIXATIONNitrogen and hydrogen are combined to form ammonium ions and then nitrate.

The process depends upon enzymes that are only possessed by NITROGEN FIXING BACTERIA, a specific class of bacteria.

Some of these bacteria live free in the soil but a very important species called Rhizobium leguminosarum lives in swellings called nodules on the roots of the leguminous plants such as peas, beans and clover.

Nitrogen fixation only happens IF OXYGEN IS PRESENT.

It also naturally occurs in the atmosphere when the energy from lightning combines nitrogen directly with oxygen.

Farmers can plant legumes in a crop rotation scheme to avoid having to use so much nitrogen-containing fertilizers. This saves money and also limits pollution of water.

NITRIFICATIONIn NITRIFICATION, ammonium ions produced by the decomposition of amino acids and proteins are oxidized , first to nitrite and then to nitrate.

The process id carried out by NITRIFYING BACTERIA which live in the soil.

Nitrifying only happens IF OXYGEN IS PRESENT.

In the absence of oxygen the process gets reversed and DENITRIFYING BACTERIA obtain their energy by converting nitrate to nitrogen gas.

This is why waterlogged soils, example: tend to lose nitrate as nitrogen gas.

RECYCLING NITROGEN

Once nitrate has been formed by either nitrogen fixation or nitrification, it can be absorbed by plants through their roots.

Eventually the plant dies and its body is added to the nimal wastes and remains in the soil.

Decomposers break down the nitrogen compounds in these wastes and remains and the formation of nitrate can begin again.

Some processes cause the loss of nitrate from the environment.This happens naturally as a result of denitrification and less naturally when crops are harvested and removed from the site where they have grown.These losses of nitrate can be made either by nitrogen fixation or by adding nitrate in the form of fertlisers.

PARASITISMParasitism is the association between two organisms such that one organism (the parasite) lives on or in the body of

another organism (the host). The parasite derives its nutrients, and usually shelter from its host. In this

process, it normally does some harm to its host.

Parasites live at the expense of their hosts, feeding on the host tissues, they cause diseases and sometimes death.Thus called PATHOGENS.

EXAMPLE: hookworms and aphids.Hookworms live in the intestines of vertebrates.Aphids suck plant juices.

What is a VECTOR???An animal that transmits a pathogen (disease causing organism) from one host to another is called a vector.

The vector may transmit the pathogen:

1. By carrying it on its body2. By swallowing infected material.

In the case of swallowed material – often blood – the pathogen survives and can multiply inside the gut of the vector.

VECTORS AND DISEASES

Name of Disease Pathogen Vector and method of transmission

Rabies Virus

Mammals including bats, rats and dogs. Passed on the saliva e.g. from the bite of an infected animal

Leptospirosis Bacterium

Mammals – passed on in the urine to bodies of water such as ponds or rivers. Humans wash or bathe in infected water.

Dengue fever Virus

Mosquito (Aedes aegypti) which bites and drinks the blood of an infected person and then passes on the virus in its saliva.

Malaria Protoctistan

Mosquito (Anopheles species) which bites and drinks the blood of an infected person and then passes on the pathogen in its saliva.

Gastroenteritis Bacterium of the salmonella group

Housefly picks up infected material from food or from faeces and then passes it onto human food as it feeds.

MALARIAL PATHOGEN

•Endemic disease in many tropical countries•Caused by certain species of Plasmodium.

•Plasmodium is a parasitic protozoan that spends one part of its life cycle in man and the other part in the female Nopheles mosquito, ie. It is a parasite of both Man and mosquito.

SIGNS AND SYMPTOMS

•Intermittent fever which occurs either every 48 hours or 72 hours.

•It attacks liver cells and red blood cells.•Inside the liver cell or RBC, the parasite reproduces asexually.•Thousands of them are released into the blood stream.•The toxin produced by the parasite in the bloodstream causes fever, usually accompanied by chills, shivering and ending in profuse sweating.

•The patient could become anaemic.•Death may occur if untreated.

TRANSMISSION OF THE PATHOGEN

•Transmitted by the female Anopheles mosquito. They are the vectors of malarial parasites as they may carry and transmit them from an infected person to a healthy person.

•When a female anopheline mosquito bites a human being, it uses its probiscis to pierce the skin of its victim, and at the same time secretes saliva into the wound.

•The saliva prevents the blood of the victim to clot around the probiscis. The insect then sucks the blood.

•If the victim is the infected person, his blood will contain Plasmodium. Thus, the parasite gets sucked into the mosquito’s stomach.

•In the stomach wall of the mosquito, the parasite first reproduces asexually to produce numerous young Plasmodium.

•The parasite travels to the mosquito’s salivary glands.

•This mosquito is now ready to transmit the disease. If it bites an uninfected person, it injects saliva, containing Plasmodium into his bloodstream.

•That person gets infected with the disease.•It can also be transmitted by the transfusion of infected blood.

METHODS OF CONTROL OF MALARIA

•An infected person should be treated with quinine or chloroquine.

•Uninfected persons travelling to malarial regions could take preventive drugs, (PALUDRINE)

•Sleep under a mosquito net as mosquitoes are most active at night.

•Anti – mosquito measures are aimed at destroying the resting and breeding places of mosquitoes or making these places unsuitable for them. They include:

1. Filling and draining of breeding places .2. Not allowing water to collect in empty tins and other

containers for too long a period in and around houses. (because they legs in water)

3. Spraying of insecticides especially in dark corners of the houses.

4. Spraying oil on stagnant water. Oil reduces the surface tension of water and mosquito larvae and pupae are killed since they are unable to adhere to the surface to breathe.

5. In ponds and lakes, small fishes may be introduced to feed on the mosquito larvae and pupae.