Principles of Ecology
BIO 271
Sufia Irfan
Department of Biology
University of Tabuk
• Ecology ?
• Ecology is the study of all the living organisms in
the biosphere and there interaction with one
another to create a stable living environment.
http://plantphys.info/plant_biology/climate.shtml
http://en.wikipedia.org/wiki/Oxygen_cycle
http://en.wikipedia.org/wiki/Phosphorus_cycle
• Levels of organization (ecology)' are the 6
levels of organization.
1. Biosphere
2. Biomes
3. Ecosystem
4. Community
5. Populations
6. Species
• What is Biosphere- This is where all living
things on Earth live. The most complex level.
• What is Biome?
A biome is a series of ecosystems that have
relatively the same abiotic and biotic factors
spread over a large area. The prominent feature
of biomes is their plant life.
• Eg: A desert's plant life consists of cacti and
other plants that have adapted to surviving
with little to no water.
• What is Ecosystem? Biological
community+Physical environment (abiotic and
biotc)
• An ecosystem is a network of interactions
between organisms and the interactions
between organisms and their environment.
• What is community?
• A community is an area in which two or more
populations of different species occupy.
• Eg: There are species of squirrels, deer,
rabbits, and other animals that inhabit the
forest area.
• What is population?
• All the organisms of the same group or species
living in the same geographical area or land
interbreeding with each other and
reproducing the offspring like them.
• Eg: A population of rabbits, deer, or humans.
• Species- Basic unit of biological organization. A
group of organisms who are able to interbreed
with each other and produce fertile offspring.
• Eg: Human (Homo sapiens), capable of
interbreeding and reproducing healthy
offspring who will grow and repeat the cycle.
• Biosphere• The biosphere is the global ecological syestem
with all living beings and their relationships
including their interaction with the elements
of the lithosphere, hydrosphere and
atmosphere.
• The biosphere is the global sum of all
ecosystems. It can also be called the zone of
life on Earth, a closed (apart from solar and
cosmic radiation and heat from the interior of
the Earth), and self-regulating system.
• The term "biosphere" was coined by geologist
Eduard Suess (1875). He defined biosphere as
• "The place on Earth's surface where life
dwells."
• Our biosphere is divided into a number of
biomes, inhabited by broadly similar flora and
fauna.
• On land, biomes are separated primarily by
latitude . Terrestrial biomes lying within the
Arctic and Antarctic Circles are relatively
barren of plant and animal life.
• Most of the biomes lie near the equator with
huge population.
• Terrestrial organisms in Temperate and Arctic
biomes- small biomass, smaller energy
budgets.
• Characters• Adaptations to cold (world wide migrations)
• social adaptations
• homoeothermy
• aestivation
• multiple layers of insulation.
• Biomes- Biomes are climatic conditions on the
Earth. E.g. communities of plants, animals,
and soil organisms, and are often referred to
as ecosystems.
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Biomes haveplant structures e.g. trees, shrubs and grasses
plant spacing (forest, woodland, savanna)
Different climate.
• A fundamental classification of biomes are:
• Terrestrial (land) biome
• Aquatic biome
1. Freshwater biome 2. marine biome
• Climate is a major factor determining the
distribution of terrestrial biomes. Important
ones are as follows• Latitude- Arctic, boreal (coniferous forest in
the north hemisphere), temperate,
subtropical, tropical
• Humidity- humid, semihumid, semiarid, and
arid
• Rainfall
• Biodiversity- increases away from the poles
towards the equator and increases with
humidity.
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The 7 biomes of the earth are:
Desert,
Tundra,
Taiga,
Savanna,
Grassland,
Temperate Deciduous Forest,
Tropical Rainforest
• Biogeochemical cycle• a biogeochemical cycle is a pathway by which
a chemical element or molecule moves
through both biotic (biosphere) and abiotic
lithosphere, atmosphere and hydrosphere
compartments of earth.
• The circulation of chemical nutrients like
carbon, oxygen, nitrogen, phosphorus,
calcium, and water etc. through the biological
and physical components.
• Ecosystems have many biogeochemical cycles
operating as a part of the system.
• E.g. The water cycle, the carbon cycle, the
nitrogen cycle, etc.
• All chemical elements present inside
organisms are part of biogeochemical cycles.
• Chemicals are part of living organisms.
• These chemical elements also cycle through
abiotic factors of ecosystems e.g. water
(hydrosphere ),
• land (lithosphere) and
• air (atmosphere).
• Water cycle- The water undergoes
evaporation, condensation and precipitation,
falling back to Earth clean and fresh.
• Elements, chemical compounds, and other
forms of matter are passed from one organism
to another and from one part of the biosphere
to another through biogeochemical cycles.
• Carbon cycle- The carbon cycle is the
biogeochemical cycle by which carbon is
exchanged among the
• biosphere,
• Pedosphere (soil layers and microorganisms)
• geosphere,
• hydrosphere, and
• atmosphere of the Earth.
• Carbon is the major constituent of all organic
matter,
• from fossil fuels to DNA the genetic basis of all
life forms.
• Carbon- fourth most abundant chemical
element in the universe.
• Forms the building blocks of the living world
along with hydrogen and oxygen.
• Its concentration in the biotic world (living
world) is almost 100 times more than that in
the abiotic (non-living) world.
• CO2- Important greenhouse gas, and
responsible for the greenhouse effect that
increasing the earths temperature.
• There is a constant exchange of carbon
between the biotic and the abiotic world, thus
forming a cycle which is called the carbon
cycle.
• Carbon dioxide is regularly being returned to
the atmosphere by the process of respiration
in plants and animals.
• Burning of wood and fossil fuels in industries
and automobiles also releases carbon dioxide.
• CO2 Used by Plants for Photosynthesis –
• Green plants primary producers
photoautotrophs are removing carbon dioxide
from the atmosphere through the process of
photosynthesis.
• Nitrogen cycle- movement of
nitrogen through the environment. Nitrogen
exists in the soil,in plants and animals, and in
the air.
• nitrogen gas (N2) makes up 78% of the
air,plants cannot use it for growth unless it is
turned into nitrate (NO3) in the soil.
• Nitrogen fixing bacteria present in the some
plant root nodules change nitrogen into
nitrate.
• E.g. peas, beans and clover.
• Ammonia- (NH3) present in animal excreta
and dead animals body.
• ammonia turns into nitrite and nitrifying
bacteria in the soil turns nitrite (NO2) into
nitrate (NO3). They increase the amount of
nitrate in the soil.
• Denitrifying bacteria in the soil- turn nitrate
(NO3) into nitrogen gas (N2) and the nitrogen
gas goes back into the atmosphere.
• Most of the nitrogen in the atmosphere is
fixed through N cycle.
• Oxygen cycle- Biogeochemical cycle describes
the movement of oxygen in atmosphere,
lithosphere and biosphere
• Driving factor of the oxygen cycle is
photosynthesis responsible for modern day
life on the earth.
Oxygen Cycle
• Oxygen cycle is a natural cycle through which
plants and other producers use carbon dioxide
from the atmosphere and produce oxygen
through the process of photosynthesis.
• Marine organisms in the biosphere make
calcium carbonate shell material (CaCO3) that
is rich in oxygen.
• Atmosphere has no significant role in the
movement of phosphorus, because
phosphorus and phosphorus-based
compounds are solids and found on the Earth.
• Phosphorus is an essential nutrient for plants
and animals.
• Phosphorus is a limiting nutrient for aquatic
organisms.
• Phosphorus occurs in nature as part of a
phosphate ion (PO4)3-.
• The primary biological importance of
phosphates is as a in the nucleotide.