ECOLOGY

Ecology is defined as the study of living organisms in relation to their environment. The study
can be limited to the study of relationship between a single individual (or group of organisms of
the same species) and the environment or widened to study different species of living organisms
and their environment.

Ecology is divided into two main branches.

Autecology– is the study of an individual organism or a single species of organism and its
environment. For example, the study of a single and its environment.

Synecology-is the study of the inter-relationship between groups of organisms or species of

organisms living together in an area. For example the study of different organisms in a river in
relation to their aquatic environment.

ECOLOGICAL CONCEPTS

Habitat– is defined as any environment which an organism lives naturally e.g. Fish lives in
water, land, air and trees.

Environment- is the overall external and internal factors that affect living organisms.

Ecosystem-is defined as the association between living components (plant and animals) with the
non-living factors of the environment. Biotic factor/component includes all living organisms in
the environment often called biotic community. The biotic population include:

 Food producer (autotrophs) e.g. green plant

 Food consumer (heterotrophs) e.g. herbivore, carnivore and omnivore, protozoa and some
bacteria.
 The decomposers are organism that cause the decay of dead plant and animals e.g. saprophytes
such as fungi and bacteria

The abiotic factors/component is the non-living factors in the physical environment. They are
what organisms need to stay alive. These factors include soil, water, temperature, humidity, light

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intensity, air minerals salts etc. The abiotic factors control the activities of the biotic component
just as the organism also influence and control the abiotic environment.

Biomes are large easily recognizable terrestrial ecosystems consisting of plants and animals
naturally living together.

Biosphere or Ecosphere is the zone of the earth occupies by living organisms. It is a layer of
life which exists on the earth surface. Lithosphere is the solid portion of the earth. It is the
outermost layer or zone of the earth crust. It is made up of rocks and minerals materials.
Hydrosphere is the liquid or aquatic part of the earth of the earth or living world. It holds water
in various forms e.g. solid (ice), Liquid (water) and as gases. Examples of hydrosphere are lake,
pools, spring, ocean or sea, ponds, oasis, river and stream. Atmosphere- This is the gaseous
portion of the earth. It is a layer of gases surrounding the earth.

Ecological Niche is defined as the specific portion of the habitat which is occupied by a
particular species or organism. It is the functional position of an organism in the community for
examples; a caterpillar and aphid which lives on the same plant occupy different position or
ecological niche on the plant.

Population is defined as the total number of organisms of the same species living together in a
given area. For example, the total number of Tilapia fish in a pond constitutes the population
Tilapia in that habitat.

Community of organism consists of the population of different kinds of organisms living

together in an area or habitat.

Food Chain: This is the sequence of transfer of matters and energy in the form of food from
organism to organism. Food chain intertwines locally to form a food web because most
organisms consume more than one type of animal or plant.

Grass Grasshopper Bird Snake Owl

Fungi (Mushroom

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Trophic Levels: Trophic levels refer to the hierarchical stages in a food chain, starting from
autotrophs and moving towards primary, secondary, and tertiary consumers. An organism that is
a predator at one trophic level can become the prey at a higher trophic level. For example, krill
are predators of phytoplankton but are also the prey of higher predators, penguins. At the next
trophic level, penguins are the prey of sharks.

Trophic pyramid: The basic structure of interaction in all biological communities characterized
by the manner in which food energy is passed from one trophic level to the next along the food
chain. The base of the pyramid is composed of species called autotrophs, the primary producers
of the ecosystem. All other organisms in the ecosystem are consumers called heterotrophs, which
either directly or indirectly depend on the primary producers for food energy.

A pyramid of numbers shows the total number of individual organisms at each level in the food
chain of an ecosystem. An inverted pyramid of numbers can be found in an ecosystem where
the community contains a few producers with a very large biomass that support a larger number
of smaller consumers.

A pyramid of energy shows the total quantity of available energy stored in the biomass of
organisms at each level in the food chain of an ecosystem per year.

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INSTRUMENTS USED TO MEASURE ECOLOGICAL FACTORS

 Temperature: thermometer
 Pressure: barometer
 Rainfall: rain gauge
 Wind speed: anemometer
 Wind direction: wind vane
 Relative humidity: hygrometer
 Light: light meter or photometer
 Turbidity: secchi disc

BIOLOGICAL INTERACTION/ ASSOCIATION IN AN ECOSYSTEM

Biological associations are relationships or interactions among living organisms as no living

organism can exist as an isolated entity. Therefore, a living organism A goes into a relationship
with another living organism B voluntarily or involuntarily. Organisms live in an assemblage of
populations having at least two different species that are in constant interaction with each other
either directly or indirectly within a specific geographical region in an ecological community.
The interaction between species forms the basis for many biological processes in ecosystems
such as the food chain and the nutrient cycle. The nature of these interactions depends upon the
environmental conditions and evolutionary aspects in which they exist. There are several
classifications of these interactions which are found in different ecosystems. These interactions
can be used as a framework in analyzing the ecological community to describe processes that
naturally occurs which in turn can be used to predict human modifications that may affect the
properties and processes of ecosystems.

Symbiosis

A symbiosis is an evolved interaction or close living relationship between organisms from

different species, usually with benefits to one or both of the individuals involved. Symbioses
may be ‗obligate‘, in which case the relationship between the two species is so interdependent,
that each of the organisms is unable to survive without the other, or ‗facultative‘, in which the
two species engage in a symbiotic partnership through choice, and can survive individually.
Obligate symbioses are often evolved over a long period of time, while facultative symbioses

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may be more modern, behavioral adaptions; given time, facultative symbioses may evolve into
obligate symbioses.

Types of Symbiosis

i. Parasitism ii. Commensalism iii. Mutualism

Parasitism: This is a relationship between two species of plants or animals in which one
organism (parasite) lives in/on another organism (host), procuring nutrient and causing harm to
it. Parasites may be characterized as ectoparasites—including ticks, fleas, leeches, and lice—
which live on the body surface of the host and do not themselves commonly cause disease in the
host; or endoparasites, which include tapeworms, hookworm, liver fluke, plasmodium etc.
example of parasitic fungi are Phytophthora palmivora that causes black pod disease of cocoa
and Phytophthora infestans causing late blight disease of potato. Dodder, mistletoes and witch
weeds are examples of parasitic plants A parasite must be able to cling on the host‘s body
surface. Parasites have boring organs which enable them to enter the host. Also, parasites
produce enzymes to dissolve tissues enabling them to penetrate the host.

Commensalism: It is an imbalanced type of interaction wherein one entity benefits while the
other is neither harmed nor benefited (unaffected). The commensal—the species that benefits
from the association—may obtain nutrients, shelter or support from the host species, which is
unaffected. The commensal relation is often between a larger host and a smaller commensal. The
host organism is essentially unchanged by the interaction, whereas the commensal species may
show great morphological adaptation. Many bacteria in the large intestine of man are
commensals as they feed on unwanted food and get protection while the hosts are not affected in
any way.

Mutualism: This is an association between organisms of two different species in which each
benefit from the interaction. Mutualistic arrangements are most likely to develop between
organisms with widely different living requirements. Several well-known examples of
mutualistic arrangements exist. The partnership between nitrogen-fixing bacteria and leguminous
plants is one example. In addition, cows possess rumen bacteria that live in the digestive
tract and help digest the plants the cow consumes. Associations between tree roots and

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certain fungi are often mutualistic (see mycorrhiza). Relationship between an alga and a fungus
in lichen and between flowers and pollinators (insects) are also good examples of mutualism.

Predation

Predation is a biological interaction where one organism, the predator, kills and eats another
organism, its prey. Carnivorous predators kill and eat their prey. The common perception of
carnivory involves a large animal, such as a shark, tiger, or wolf hunting smaller animals like
rabbits or deer. However, carnivorous predation is widespread in the animal world and
carnivores can come in a variety of sizes. Each carnivore is adapted to its mode of feeding.
Herbivorous predation involves the consumption of autotrophs, such as plants or photosynthetic
algae. Unlike carnivory, not every herbivorous interaction leads to the death of the plant.
Occasionally, herbivory can benefit the plant as well. Fruit seeds are dispersed over wide areas
as the herbivore moves. Tough seed coatings are removed in the digestive tract of the herbivore,
and its dung fertilizes the soil, providing an ideal environment for seed germination.

Competition

Competition is an interaction between organisms or species in which both require a resource that
is in limited supply (such as food, water, or territory). Competition lowers the fitness of both
organisms involved, since the presence of one of the organisms always reduces the amount of the
resource available to the other. Competition can be interspecific or intraspecific competition. It
said to be interspecific if it is between organisms of different species and intraspecific if the
competition is between organisms of the same species.

HABITAT

In ecology, a habitat is where a species of organism lives or thrives. It is the natural

environment of that species. It is where it will derive its food, shelter, and mate for reproduction.
It is where the species will attempt to be as adaptive as possible.

Terrestrial Habitat

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The term terrestrial in biology is generally used to describe living organisms that live and grow
on land. Living things that make use of nature as their habitat may be grouped based on where
they live, grow and reproduce. Living things that spend most of their life on land are called
terrestrial. This is in contrast to living things that live on water (called aquatic) and those that are
not growing in the ground (called aerial or epiphytic, especially of plants). There is another
distinct group of living things that live both on land and in water and they are referred to as
amphibious. As for the type of habitat, the term terrestrial may also be used. Land as a habitat is
called a terrestrial habitat to distinguish from water that is called aquatic habitat. A terrestrial
habitat would therefore indicate the habitat specifically for terrestrial living things whereas an
aquatic habitat pertains to the various shelters of aquatic living things in different water forms.

Terrestrial habitat types include forests, grasslands, wetlands and deserts. Within these
broad biomes are more specific habitat types with varying climate types, temperature regimes,
soils, altitudes and vegetation. Many of these habitat types grade into each other and each one
has its own typical communities of plants and animals. A habitat-type may suit a particular
species well, but its presence or absence at any particular location depends to some extent on
chance, on its dispersal abilities and its efficiency as a colonizer.

Types of Terrestrial Habitats

Forests: It has a dense tree population with significantly high precipitation. Tropical rainforests
are home to several different types of animal species. However, habitat features vary across
tropical deciduous forests, temperate deciduous forests and coastal coniferous forests among
others.

Grasslands: Grasslands are divided into savannas, prairies and tundra. Precipitation varies
across these grasslands and trees are usually very scarce.

Deserts: Deserts receive very little rainfall, usually approximately 25 cm. Animals living in
deserts are largely nocturnal and forage for food at night.

Mountains: The mountainous ecosystem comprises different ecologies such as forest regions,
valleys, meadows and peaks.

Terrestrial Habitat Plants

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Mesophytes: they grow at moist temperatures and retain the characteristics of a well-developed
root, shoot and vascular system

Xerophytes: they grow in a hot and dry habitat, usually common in deserts. Their stems are
fleshy and thick for storing water. The small leaves also help in reducing transpiration.

Terrestrial Habitat Animals

Desert animals: like camels and rodents have thick skin, and also have organs for water storage.

Aerial animals: have streamlined bodies and forelimbs which have developed as wings.

Arboreal animals: such as squirrels and chameleons have a curved body that helps in climbing
and a muscular chest for moving between branches.

Fossorial animals: These are burrowing animals like rats and rabbits, which have short
forelimbs, and the head is in the form of a snout.

Cursorial animals: like deer and horses live and move on hard open ground. They usually have
strong legs with locomotion being digitigrade.

Aquatic Habitat

The term aquatic is used to relate to water, as in aquatic animals, aquatic plants, aquatic
environment, aquatic habitat, and aquatic‖ locomotion.

Aquatic animals pertain to animals that live predominantly in different water forms, such as seas,
oceans, rivers, lakes, ponds, etc. Examples of aquatic animals include fish, jellyfish, sharks,
whales, octopus, crocodiles, crabs, dolphins, eels, and so on. Aquatic plants, on the other hand,
are plants found in those habitats, such as water hyacinth, water lettuce, water fern, duckweed,
water lilies, and watergrass. And these habitats where aquatic animals and plants live on are
referred to as aquatic habitats. Aquatic habitats may be freshwater, marine, or brackish water.
Organisms possess morphological and anatomical adaptations that enable them to live and thrive
in aquatic habitats. Aquatic animals that can move freely using their fins or tentalces, and other
locomotory organelles to propel themselves in an aquatic medium. Movements, such as diving
and swimming, are examples of an aquatic locomotion.

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 Characteristics of marine habitat
 High salinity which enhances bouyancy of micro-organisms.
 Temperature varies with depth.
 High pressure at low depth.
 High turbidity and low light penetration.
 There are waves, ocean currents and tides.
 High density (1.028) which enables eggs of some Marine organisms and various organisms to
float in it.
 Dissolved gases: Oxygen and carbon (iv) oxide are the common dissolved gases. More oxygen is
dissolved at surface water due to the wave action of the surface and green plants
(phytoplanktons) which carry out photosynthesis and release oxygen into the water. Oxygen is
absent at the bottom of the ocean.
 Low hydrogen ion concentration (pH) near the surface (alkaline).
 Animals in marine water include hydrozoans, sponges, hard and soft corals, anemones, snails,
slugs and mussels, squids, flatworms, tube worms, starfish, brittle stars, sea urchins, sea
cucumbers, sea squirts, whales, dolphins, sharks and reptiles. Common plants are
phytoplanktons, sea grass, kelp, algae etc.

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This zone, also known as the open ocean, is comprised of oceanic water that is not in direct
contact with the shore or sea floor. The pelagic zone is subdivided into vertical zones, based on
factors such as sunlight amount. While these waters are known as the ―deserts of the sea‖, a wide
variety of organisms still call the open ocean their home.

Epipelagic

This zone, known as the ―sunlit‖ zone, begins on the surface of the water and extends to the dark,
sunlight-less area where photosynthesis ceases in production. This layer is heated by the sun and
is mixed vertically downward by winds on the surface. This mixing allows for a distribution of
heat in this layer around the world, from super warm in the Persian Gulf (97 degrees Fahrenheit)
to super cold up at the North Pole (28 degrees Fahrenheit) (National Weather Service)!

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At the bottom of this layer lies the thermocline. The thermocline is a region of rapidly decreasing
temperatures with increasing depth. The depth of the thermocline varies in space and time and
does not remain uniform across the globe as it is dependent on the season and year. The
variability of this line can be altered by unusual weather patterns, like a monsoon, or local
impacts.

Mesopelagic

The mesopelagic zone reaches 200-1000m in depth. Technical deep-sea divers reach the 300m
mark (National Weather Service). The mesopelagic zone is home to some of the most diverse
fishes and behaviors. It is estimated that around 90% of all global fish biomass occurs in this
zone. The populations of these organisms are so large that WWII hydroacoustic researchers were
not able to penetrate the zone because of the high biomass of organisms with swim bladders.
Common fish of the Mesopelagic include hatchetfish, lanternfish, barreleye fish, and
bristlemouth fish. Many of the fish in this region are on the smaller side, but the megamouth
shark (Megachasma pelagios) stands out because of its unusually massive size (Oceana).
Reaching up to 13-18 feet long, megamouth shark are large filter feeders that swim with their
mouth open to collect food (Oceana).

Bathypelagic

The bathypelagic zone is known as the ―midnight‖ zone for its characteristically lightless waters.
At 1,000-4,000 meters below, no light is able to penetrate the ocean water this deep, preventing
any primary production. The only source of light in this zone comes from organisms using
bioluminescence (National Weather Service). Bioluminescence is the ability for animals to glow
in the dark, caused by the release of energy from chemical reactions in the form of light.

Benthic

Unlike its sister zones, the benthic (from Greek: ―Depth of the sea‖) zone is characterized not by
its depth but by the body of water itself. The benthic zone is the lowest level of the ocean,
encompassing the sediment surface and the water level right above it, starting from the shoreline
and expanding to the deepest part of the ocean floor. Due to its large surface area, it is difficult to

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 generalize the physical characteristics of the benthic zone; however, the most important and
notable part of the zone lies with its ecological properties.

Characteristics of Fresh water habitat

 It includes pool, river, stream, pond, lake etc

 It has low salt content.
 Relatively small body of water.
 The water is shallow.
 Its temperature varies with depth and season.
 Low density water.
 Turbidity depends on season.
 There is available oxygen in all parts of water but more at the surface.
 It accommodates bony fish such as tilapia. Fish living in freshwater habitats have plenty of
company. Snails, worms, turtles, frogs, marsh birds, mollusks, alligators, beavers, otters,
snakes, and many types of insects live there too. Some unusual animals, like the river dolphin
and the diving bell spider, are freshwater creatures. Planktons are also present

Characteristics of Estuarine Habitat

An estuarine habitat is an ecological zone where river and sea water meet, thus, to establish
brackish conditions. Brackish water has a salinity which fluctuates with the tides and wet and dry
seasons. It is neither salt water nor fresh water, but the intermediary between both. It occurs
where freshwater interact with salt water.

 It has a fluctuating salinity

 It has poor aerated substratum or saturated soil that lack oxygen
 There is a mild wave action.
 There is high and low tidal influence
 Soil erosion is prominent
 It is exposed and prone to flood periodically

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 Turbidity of estuarine habitat increases especially during the rainy season when lots of
debris is brought down by rivers. High turbidity reduces photosynthesis and respiration
rates of organisms.
 The habitat has low species diversity of species compare to marine habitat.
 Unlike marine water that is deep, the water in estuarine habitat is very shallow

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