BIOLOGY A LEVEL(FORM SIX) NOTES – ECOLOGY

ECOLOGY

• Is the study of relationships of living organisms to each other and their surrounding (physical surrounding)

• It gives us scientific foundation of understanding some fields of studies such as agriculture which concern with crop cultivation and animal husbandry, forestry, fishery and so on
• The study of ecology gives us the basis for predicting and remedying environmental degradation (how to conserve environment)
• Help us to understand the likely consequences of massive interventions in the environment e.g. construction of huge dams, deforestation to open space for plantation, agriculture e.t.c
• Ecology is an important interdisciplinary science linking physical, biological and social science.
• Ecology has given rise to a growing public awareness on environmental issues. This has given rise to development of laws on environment protection, formation of new political perspective e.g. environmentalism in Europe, emergence of environmental consultancies, development of environmental data services / base, e.t.c.

1. Environment Refers to the surrounding of organisms. OR

• Everything that surround an organism and influence it.

1. Population is a group of organisms of one species occupying a defined area or habitat at the same time.Community – Any group of organisms belonging to a number of different species that co-exist in the habitat or area and interact through trophic and spatial relationship.
2. Ecosystem – A community of organisms and their physical environment interacting as an ecological unit.
3. Habitat is a typical environment of a particular organism or population or community.

1. Biosphere – Is the total volume of the earth in which life permanently exists.

• Ecosystem Approach

• Community Approach.

• Population Approach (Ant ecological approach)

• Habitat Approach

• Evolutionary and historical approach
• This focuses on the changes that have occurred in the organisms over time and the development of technology and culture of the human species.

• The ecosystem refers to a community of organisms and their physical environment interacting as an ecological unit.
• The term describe the whole complex of organisms living together as a sociological unit and its habitat.

• The ecosystem is made up of living and Non- living components
• The living component of the ecosystem is known as biotic component, these include plants, animals, microorganisms e.t.c
• The Non- living component is known as Abiotic component. The Non- living component of an ecosystem is divided into:-
• Soil
• Water
• Climate

• Energy flow
• Cycling of nutrient

• Producers – are the autotrophic organisms or the organisms which in turn are eaten by other organisms.

1. Producers: These are autotrophs which synthesis the food using sunlight energy.

• Consumers

• Primary consumers

• Secondary consumers.

• Tertiary consumers

• Energy decreases as one move from one trophic level to another. There is less energy to support the organisms.
• The first Trophic level is occupied by producers (autotrophs).
• The second trophic level is occupied by the herbivores
• The third trophic level is occupied by secondary consumers – the carnivores.
• The fourth trophic level is occupied by the carnivores (Tertiary consumers)

ECOLOGICAL PYRAMIDS

Pyramids of Numbers
In ecosystems the smaller organisms usually outnumber the large organisms. Pyramid of numbers shows the number of organisms in each trophic lever and how they change in successive levels of ecosystem.
.In a trophic lever based pyramid of numbers the organisms of a given area are first counted and then grouped
in their trophic levers.
.There is a progressive decrease in the number of animals at each successive level
.Plants in the first trophic level often outnumber animals at the second trophic level but it will depend on the relative size of organism


Types of Pyramid of numbers.

• It is more laborious and expensive in terms of time and equipment.
• It does not allow for changes in biomass at different time of the year e.g. deciduous tree have a large biomass in summer than in winter, when they have shed their leaves.
• The rate at which the biomass accumulates is not taken into account. A mature tree has a large biomass which increases slowly over many years.

• They do not show the rate production (productivity that is the amounts of materials and energy passing from one trophic level to the next).

• Some energy is used for metabolic activities at each trophic level, mainly respiration.
• A lot of energy is lost in form of heat hence is not available in the ecosystem energy lost in respiration cannot be transferred to other living organisms.
• Some energy is locked in animal or plant parts which cannot be eaten e.g. Bones, horns, nails, and feathers of animals and cellulose materials of plants which are indigestible.
• Organisms do not assimilate some of the materials taken in as food.
• The consumer population is unable to harvest enough of the food population.

• It takes into account the rate of production, in contrast to pyramids of numbers and biomass which depict the standing states of organisms at a particular moment in time.
• It allow different ecosystem to be compared including the relative importance of population within one ecosystem.
• They tell how much energy is required to
  support each trophic level because only a proportion of energy in a level is transferred to the next.
• Energy pyramid are never invested nor do they have a central bulge
• Energy pyramids are more informative than the pyramid of number and biomass.
• Input of solar energy can be added as an extra rectangle at the base of pyramid of energy.

• They are the most difficult to obtain data
• They are not an accurate method of representing energy content of the ecosystem.

• The pyramids of numbers, biomass and energy depend on assigning living organisms to trophic level. While the correct level is obvious for plants and obligate herbivores. Many carnivores and omnivores eat a varied diet and thus their trophic level varies according to the food selected.
• It is hard to fit dead material (detritus) and other waste together with their consumers into conventional pyramids. These materials are important as a food source.

• Nitrogen Fixation

• Nitrification
• Nitrification is the production of nitrates. Nitrogen is converted to Nitrate (NO3–) in several ways.

• By lightening and other cosmic radiation

• By the action of nitrifying bacteria ammonia (NH3) in the soil is converted to Nitrates by certain soil bacteria in a two – step process flost, nitrite producing bacteria convert ammonia to nitrite (NO2–) this is achieved by free living bacteria such as Nitrosomonas.

• Humans make a most significant contribution to the nitrogen cycle when they convert nitrogen gas to nitrate for use in fertilizer.

• Nitrogen used by plants and animals.

• Decomposition by Microorganisms

• Denitrifying bacteria

CARBON CYCLE

• The producers (green plants and algae) use CO2 to make food.

• Herbivores eat plants and carbon gets into the body of carnivores.

• Both plants and animals respire. The process returns CO2 to the atmosphere.

• When plants and animals die, the decomposers break down dead bodies and carbon is released to the soil where it is absorbed by plant roots.

• Oceans and seas are large reservoir of carbon in form of HCO3–. This can be used to build up shells of marine organisms. Some reaction change bicarbonate into CO2 that return to the atmosphere.

• Living and dead organisms contain organic carbon and serve as one reservoir for carbon cycle.

• Calcium carbonate that accumulate in limestone and calcium carbonate in carbonate shells.

• Burning of fossil fuels e.g.; coal and oils used for running machines and automobiles. These results into release of much CO2 and other gases in the atmosphere.

• Burning of fuel wood i.e. firewood and charcoal
• Deforestation i.e. destruction of forests through burning on cutting trees.

• The niche of organism is defined as its profession or total role in a community, e.g. an organism can be producer, consumer, predator, scavenger or a decomposer.

• Defined as a place occupied by a species in an ecosystem and the way it use the resources of the ecosystem.

• The niche of an organism means its place in a biotic environment and its relation to food, enemies, habits and biological factors.

• Community ecology focuses on the development and stability of the communities.

• A stable community is established through number of stages which are orderly.

• During the time of development there will be an orderly and progressive replacement of one community by another till a relatively stable community is established. This is called ecological succession.

• Ecological succession is the process in which a community is evolved from simple beginning to more complex which is more or less stable. A complete succession is called a sere.

• A complete stable community is called a climax community.

• Primary succession

• Secondary succession

1. Primary succession – Is a type of succession when the community is established where no community has previously existed.

• Is a type of sampling in which every item of the universe has an equal chance of inclusion in the sample

• It involves selection of every in the item in a list (an element of randomness is introduced into this kind of sampling by using random numbers to pick up the unit to which to start.

• Is a type of sampling in which the population is divided into several sub population on that are individuals more homogenous group than the total population.

• This refers to the number of item to be selected from the set of objects (population or universe) to constitute a sample excessively.

• It makes the study easier since few organisms are involved.

• Since only few organisms are under study this save time and reduce the financial cost if large group of organisms were to be studied.

• By transects

• By quadrants

• Point frame

• Pit fall

• Box trapping.

• Ways of establishing a sample

• Transects – line transect

• Belt transect.

• Quadrants – quadrat

• Pin frame (point quadrant)

• permanent quadrat.

• Is a method where a tape or string is run along a ground in a straight line between two points or poles .

• A belt transect is simply a strip of chosen width through the habitat made by setting up two line transects say 0.5m to 1m a part.

• A quadrant frame is a metal of wooden frame preferably collapsible to facilitate carrying, which forms a square of known area such as 0.25m2 or 1m2

• The way a quadrant is used

• The use of these methods depends on (number of factors) nature of investigation.

• This is a frame bearing a number of holes through which a pin “such as knitting needle can be passed”

• This is used in long term ecological investigation involving the study of community change (succession or seasonal changes).

• Computer program

• Direct observation

• Photographs

• Pit fall trap

• Box trapping

• The capture – recapture method of sampling is used to try to estimate the entire population, a sample of animals is caught and tagged their number noted and then released into their habitat. Later another sample is captured and the proportion of tagged animal in this sample should be representative of the proportion of tagged animal in the whole population and then the total population size can be estimated using this formula.

• Species density

• Species Frequency

• Species cover

• In this method the number of animals captured is recorded and the animal kept. This procedure is repeated a further three times and the gradually reducing number recorded. A graph is plotted of number of animals captured per sample against the previous cumulative number of animal captured. By extrapolating the line of the graph to the point at which no further animal would be captured (i.e. number in sample = 0)

• A group of organism of the same species occupying a particular species and usually isolated to some extent from other similar groups by geographical factor / topography.

• Population studies are not just about the number of a given species living in a given area at given moment in time but it includes also how population grow, how population is maintained and how and why population decline.

• Population dynamics is the study of how and why population size changes over time. It examines the characteristics of a group of organisms such as density, natality (birth rate), survival ship, age structure, migration and from of growth of the population.

• Reproductive potential of the organism

• The rate of reproduction given unlimited environmental resource.

• Environmental resistance

• This is the sum of total limiting factor both biotic and abiotic which act together to prevent the maximum reproductive potential from being realized. It includes external factor such as predation, food supply, heat, light and space, and internal regulatory mechanisms such as intra specific competition and behavioral adaptation.

• The territorial behavior

• Physical effects of over crowding

• Territories are typically used for feeding, mating, rearing of young or combination of these activities.

• Territorial animals benefit in several ways they have exclusive access to food supplies and breeding areas within their territories.

• Also familiarity with their areas help them to obtain food there and avoid predators

• Moreover they can care for their young without interference from other individuals of the same species.

• Population growth curves
• Two basic forms of growth curves can be identified.

• The j-shaped growth curves

• The S-shaped growth curves or sigmoid growth curve.

• J-Shaped growth curve

• This type of growth curves describes a situation in which after initial establishment phase (lag phase) population growth continues in an exponential form until stopped abruptly as the environmental resistance becomes suddenly effective.

• Growth is said to be density independent since regulation of growth rate is not tied to the population density until the final cash.

• The crash may be triggered by factor such as seasonality or the end of a breeding phase, either of the organism itself or of an important prey species. It may also be associated with a particular stage in a life cycle such as seed production or it may be included by human intervention.

• A biome is a large region in the biosphere that possesses characteristic physical condition on that support organisms which show adaptations to those condition found there.

• Is a collection of similar ecosystem in a particular region of the earth, it could be a habitat or zone such as desert forest, grassland or water bodies such as ocean, lakes etc.

• Is a largest terrestrial communication or a largest ecological unit.

• A biome has a specific kind of plants and animal species within a geographical area that has distinct climatic conditions. A biome is a product of physical factors that influence the rainfall, temperature and light.

• Tundra

• Northern coniferous forest or Taiga

• Deciduous forest

• The Mediterranean shrub

• Tropical savannah

• Grassland

• Desert

• Marine environment

• Fresh water environment

• Human population is the most abundant (about 7 billion) which is next to certain species of fishes and insects.

• Human population is widely distributed on earth in almost all climatic conditions from arctic to Antarctica.

• The population differ economically, socially, culturally and color and height in different part of the world.

• The study of trends in human population growth and the prediction of future development is known as demography.

• Climatic and Edhapic factor

• Location of natural resources

• Transport facilities.

• Industrial development and education

• Rate of growth of human population is not uniform in all the countries, the developed countries have stable or negative growth rate (both the birth and death rate are low).

• Rate of grow
  th differ among different group of people within a country.

• The population of the urban areas is leading to overcrowding and is causing adverse environmental implications.

• Is the release into the environment of substances or energy in such quantities and for such duration that they cause harm to the people or other organisms or their environment.

• The harmful substances are collectively known as pollutants

• Pollutants destroy the natural quality of the environment.

• Agri
  cultural chemicals such as fertilizers, pesticides and herbicides

• Industrial by products or emissions such as sulphur dioxide, mercury, carbon monoxide, CFC’S lead, cadminium

• Sewage

• Smog

• Oils

• Radiations such as gamma rays, x-ray

• dusts

• Materials form the natural environment / ecosystem that man can use.

• Renewable resources: – Are those which can be replaced within a short period of time after being used e.g. water, wildlife forest e.t.c.

• Non- renewable resources: – Cannot be easily replaced within a short – time e.g. tonsil foils, minerals.

• Ethical reasons – cultural, tradition, religious beliefs, political persuasion, shape our attitude toward nature.

• Nature does not exist simply for humans to transform & modify because all living species have a right to coexist with us on earth. Man has no right to cause the extinction or to diminish the quality of life of any organism.

• Custodianship – Man has to pass on to the future generations to all the diversity of life & quality of environment that we inherited.

• Athletic reasons – Humans derive pleasure from pleasant environment & the presence of other living organisms.

• Local national & international organization exist worldwide to promote wildlife contribute to our immediate needs e.g. in forestry many plant species have important medical uses.

• Fisheries from water bodies as direct source of food

• Agriculture – We have to conserve food stocks and soil quality for crops.

• Usage of pollinating insects & beneficial predators in pest control.

• Maintenance of balanced biochemical cycles to avoid pollution & regulation of the earth’s climatic conditions.

• To avoid deforestation & desertification.

• To avoid loss of vegetation cover this may affect soil erosion leading to accumulation of mud on river beds & costs.

• Reduce extinction of species to retain diversity gene pool (retaining biodiversity)

• To preserve care species that may have generation potential.

• To minimize effects of mining / drilling/ urbanization.

• People should be educated on the importance of our environment by:-

• Encouraging them to plant trees

• Encouraging the use of organic manure & good agricultural practices in agriculture such as terrace farming on hill sides, crop rotation.

• Discouraging harmful traditions such as burning / slash method of farming to clear the land.

• Legislation

• Laws that govern the protection of national parks/ grass kinds & punishments for those who start bush fires

• Laws that protect the endangered species as a means of preventing extinction e.g. rhino

• Some animal species must be regulated to avoid over – population e.g. wild beasts.

• Reduction of pollution e.g. by using lead free petrol, alternate energy source (solar power, ethanol cars) use of bio degradable products, recycle waste such as paper to avoid deforestation, glass & cans water as resource & its sources must be preserved. Government should increase biodiversity by increasing botanical gardens, seed banks & field gene banks.

• Sustainability – exploitation of natural resources & conserving then for future generations.

• Avoid excessive use of chemicals such as pesticides and herbicides.

• Encouraging biological control.

• Is the artificial control of pests & parasites those which compete with human for food or damage the health of humans or livestock by the use of organisms or their products & therefore it is based on predator – prey relati
  onship. The control agent either control the pest by feeding on it (lady bird or aphids, caterpillars larvae of butterflies & moths) are parasitized by bacillus species or by causing disease to the pests e.g. Virus sprays on army worm caterpillar.

• Is to bring the population of the pest down to a tolerable level and not to eradicated by its natural enemy.

• It doesn’t pollute the environment

• It’s easy to apply as it doesn’t involve the use of sophisticated machine

• Its effective through generations as the pest will not develop resistance to the predator as it is with the pesticides & herbicides. Thus time to time application is not important.

• The predator eliminates or feeds / affects the intended organisms or i.e. it is selective.

• It is cheap.

• The beneficial organisms may also be eliminated due to lack of food if it dominates the harmful organisms or pest which may cause / lead to disruption of food chain.

• The predator (agent) may turn into a pest by feeding on other useful organisms instead of feeding on the intended organisms’ e.g
  . after controlling the pest population it may become a pest itself.

• It’s expensive i.e. involves studying the biology of the pest & the predator & this may take a long time.

• If important agents / predators may fail to survive when the environment of the new country changes.

• Biological control may not be effective if the pest outbreak is high because the agent/ predators are fairly slow to react / to eat to large numbers of pests. The population of pest species left may still be great enough to continue causing damage.