MEWAR INTERNATIONAL UNVERSITY MASAKA,

NASARAWA STATE

DEPARTMENT OF BIOTECHNOLOGY

LECTURE NOTES ON

GENERAL BIOLOGY 1 (BIO 101)

TOPIC: ECOLOGY

Compiled by S. Shuaibu and YY. Pai

INTRODUCTION

Ecology is defined as the study of inter relationship and interaction of different organisms with each other
and with their environment. It is concerned with the general principles that apply to both animals and
plants. The meaning of the word ecology was given by German Biologist Ernst Haeckel in 1869. The word
ecology is derived from Greek words ‘Oikos’ meaning house, habitat or place of living and ‘Logos’
meaning to study.

OBJECTIVES OF ECOLOGICAL STUDIES

It is important for humanity to understand its environment because we have the ability to modify the
environment through the use of technology. Therefore, ecology is more than just the understanding of the
interrelationships between organisms and their environment; it also has social, political, economic and
technological dimensions. It also is a study of evolutionary development of organisms, the biological
productivity and energy flow in the natural system. To develop mathematical models to relate interaction of
parameters and to predict the effects.

CLASSIFICATION OF ECOLOGY

Based on study area:

Autecology: It deals with the study of an individual species of organisms and it’s population. The

ecologists study the behavior and adaptations of particular species to the environmental condition

at every stage of that individual’s life cycle. It is also called the Species ecology.

Synecology: It deals with the study of communities, their composition, their behaviour and relation
with the environment. It is also called as Ecology of communities.

Based on Environment or habitat:

Aquatic ecology: The study of interaction of organisms in the water

Marine water ecology - Ocean, Deep Sea, Estuary

Freshwater Ecology - Letic (Running water) – River, Stream, Spring

Lentic (Standing Water) –Pond, Lake.

Terrestrial Ecology: The study of interaction of organisms on land surfaces divided as grassland ecology,
forest ecology & desert ecology.

Organism Ecology:

Organismal ecology is the study of an individual organism’s behaviour, morphology, physiology, etc. in
response to environmental challenges. Ecologists research how organisms are adapted to these non-living
and living components of their surroundings. Individual species are related to various adaptations like
physiological adaptation, morphological adaptation, and behavioural adaptation.

Population Ecology:

It deals with factors that alter and impact the genetic composition and the size of the population of same
species. Population ecology examines the population distribution and density. Population density is the
number of individuals in a given volume or area. This helps in determining whether a particular species is
in endanger or its number is to be controlled and resources to be replenished.

Community Ecology:

It deals with how community structure is modified by interactions among living organisms. Ecology
community is made up of two or more populations of different species living in a particular geographic
area.

Ecosystem Ecology

It deals with the entire ecosystem, including the study of living and non-living components and their
relationship with the environment. This science researches how ecosystems work, their interactions, etc.

Landscape Ecology

It deals with the exchange of energy, materials, organisms and other products of ecosystems. Landscape
Ecology study the habitat fragmentation (such as deforestation) or the migration of organisms between
ecosystems, etc.

Biosphere
It deals with interactions among earth’s ecosystems, land, atmosphere and oceans. It helps to understand
the large-scale interactions and their influence on the planet, the role of greenhouse gases, the effects of
climate change on ecosystems and organisms, etc.

BASIC ECOLOGICAL CONCEPTS

1. ENVIRONMENT: The sum total of the biotic (living thing) and abiotic (non-living thing)
factors that actually affect living organisms.
2. BIOSPHERE: The part of the earth in which living organisms exist and with which they
exchange materials.
3. HYDROSPHERE: Part of the earth occupied by water.
4. ATMOSPHERE: Part of the earth occupied by air.
5. HABITAT: A place where species of organisms live. The broad classifications of habitat
include terrestrial, arboreal and aquatic.
6. NICHE: The place and role in a biological community occupied by particular specie. The
niche of an organism is the functional role that it plays within an ecosystem.
7. SPECIE: The group of organisms that resemble one another and can interbreed freely.
8. POPULATION: Is a group of interbreeding individuals of the same species in any
given environment at a particular time.
9. COMMUNITY: This is the combination or group of different species (plant and
animals) living together in a habitat at a particular time.
10. BIOME: It is an area classified according to the species that live in that location.
11. ECOSYSTEM: is a community of organisms interacting with one another and with their
non-living surroundings. Examples include the ponds, rivers (aquatic ecosystem) and land
(terrestrial ecosystem).

ECOSYSTEM
Ecosystem is a biological community where the living and non-living components interact with
each other as their physical environment. It is the functional unit of nature and varies greatly in
size.

Types of Ecosystem
1. Natural ecosystem
a) Aquatic Ecosystem. Eg- Running water, standing water, Marine ecosystem
b) Terrestrial Ecosystem. Eg- Grassland, forest, desert ecosystem.
2. Artificial ecosystem - Man made ecosystem – operated and maintained by man himself Eg :
Cropland,
Gardens.

STRUCTURE (or) COMPONENTS OF AN ECOSYSTEM

The structure of an ecosystem explains the relationship between the abiotic (non –living) and the
biotic (living) components. An ecosystem has two major components.
• Biotic (living) components.
• Abiotic (non-living) components

Biotic components
The living organisms (or) living members in an ecosystem collectively form its community
called biotic components (or) biotic community. Examples:-Plants (producers),animals
(consumers) and micro-organisms (decomposers). The members of biotic components of an
ecosystem are grouped into three, based on how they get food.
● Producer (plants)
● Consumer (Animals)
● Decomposers (Micro-organisms)
Producers (Autotrophs)(self-feeders)
Make their own food from compounds that are obtained from their environment. They are the
source of all food in an ecosystem. On land, most producers are green plants. In freshwater and
marine ecosystems, algae and plants are the major producers near shorelines. In open water, the
dominant producers are phytoplankton (most of them microscopic) that float or drift in the water.
Most producers capture sunlight to make carbohydrates (such as glucose) by photosynthesis. E.g
Photosynthesis The green pigments called chlorophyll, present in the leaves of plants, converts
CO2 and H2O in the presence of sunlight into carbohydrates.
6CO2 + 12H2O ----> C6H12O6 + 6O2 +6H2O.

Consumers (Heterotrophs) (“other feeders”)

Get their energy and nutrients by feeding on other organisms or their remains.
Primary consumers: Are those that eat producers (plants) as a source of food. They are also
known as herbivores.
Secondary consumers or carnivores: Eat other animals.
Tertiary Consumers: Large Carnivores which feed on secondary consumers.
Quaternary Consumers: Largest Carnivores that feed on tertiary consumers. They are not eaten
by any animals.
Omnivores: Have mixed diet that include both plants and animals.

Decomposer:
Mostly certain types of bacteria and fungi are specialized consumers that recycle organic matter
in ecosystems. They do this by breaking down (biodegrading) dead organic material to get
nutrients and releasing the resulting simpler inorganic compounds into the soil and water, where
they can be taken up as nutrients by producers.

Interactions with other organisms

1. Competition: This is the struggle for resources that are in short supply. It involves the
Interaction among two or more organisms of the same species or different species in
which one out grows the other and survives while the other cannot grow nor survive.
2. Parasitism: - This is a close association between two organisms in which one called the
parasite, lives in or on, and feeds at the expense of the other organism called the host. The
parasite benefits from the association while the host usually suffers harm or even die.
Example is tapeworm in the intestine of man obtains digested food and protection from
man while man derives no benefit from the association but suffers. Another example is
mistletoe and flowering plant.

3. Commensalism: This is an association or a relationship between indivisuals of two

species living together in which one specie(the commensal) obtain food or other benefits
from the association while the other neither benefit nor is harmed. Examples are remora
and shark. Remora attaches itself temporarily to the shark and feed on scraps the shark
fails to consume and shark is neither harmed nor benefited as a result of the presence of
the remora fish. Second is man and intestinal bacteria.

4. Mutualism: This is the association between two organisms of different species in which
both of them (host and a symbiont) benefit from each other. Example is lichen(alga and
fungi).The alga supplies photosynthetic products to the fungus while the fungus provides
support and water to the alga. Other examples are bacteria in the rumen of ruminants,
flowers and insects and lastly is nitrogen fixing bacteria in the root nodules of
leguminous plant.

5. Predation: Predation is a biological interaction where one organism the predator, kills
and eats another organism, its prey. The predator benefits while the prey is completely
eliminated. Examples are a pride of lions attacking a larger animal, such as elephant,
dolphins chasing and eating fish, house cats killing mice, birds and other small animals.

6. Pathogens: Pathogens are are microscopic organisms including viruses, bacteria, fungi
and parasites that can cause diseases in humans, animals and plants leading to their
reduction through death

7. Dispersal: Is the spreading of new individuals from their parents to new habitat so as to
start a new life in the new environment. Such spreading habits may affect the lives of
other organisms in the new area.

8. Migration: This is the movement of members of a species to a different environment in

search of food, better conditions, or reproductive needs. organism either move into a new
habitat (immigration) or out of a habitat (emigration). The movements usually have
effects on other organisms inhibiting that habitat.
 9. Mortality: This is death rate of living organisms (plants and animals) in an environment.
Mortality usually reduces the population of organisms in any habitat

10. Natality: Natality is also known as birth rate. It is defined as the ratio of the number of
births to the size of that population. It is generally known to increase the population of
the habitat which will subsequently lead to certain problems among the organisms in that
habitat.

Abiotic components
Consists of Non-living chemical & physical components such as water, air, nutrients in the soil
or water & Solar Energy. Physical & chemical factors that influence living organisms in land
(terrestrial) ecosystem & aquatic life zones. Abiotic factors can act as limiting factors that keep a
population at a certain level. Abiotic Components are mainly of two types they are Climatic
factors and Edaphic factors
Climatic Factors: which include rain, temperature, light, wind, etc.
Edaphic Factors: which include soil, pH, Topography, Minerals, etc.
Topographic factors: These include the nature of the soil, shape of land, Altitude, drainage and
erosion.

What are the Abiotic Factors?

 It is the non-living part of an environment. It includes all the physical and chemical
aspects of an ecosystem.
 These factors may be present in the atmosphere, hydrosphere, and lithosphere. It
contributes to the continuity of life on earth by supporting the survival and reproduction
process.
 The component also depends upon the type of ecosystem.
 For example, Rainfall contributes to tropical rainforest ecosystems, sand in desert
ecosystems and water, salinity, ocean currents, pressure in the marine ecosystem.
All the factors are interrelated to each other.
All the biotic components i.e living components are directly or indirectly dependent upon the
abiotic factors. The biotic and abiotic systems work together for maintaining the ecosystem

Abiotic factors include:

 Water
 Sunlight
 Temperature
 Soil
 Atmosphere
 pH
 Air Humidity
 Wind
 Elevation

Water
 Water is an essential abiotic factor. Not only plants but animals even tiny micro-
organisms also need water for their survival. In the absence of water, plants will die, i.e
producers will die. Even the plants in the desert require some amount of water.
 Due to dehydration, animals will die. i.e consumers
 In the case of micro-organism, they need water for proper functioning which we call
water activity. We can take a simple example by giving insight into our kitchen. Dry
fruits can be stored for a long time as compared to juicy fruits.
 Among the various factors, the water activity of an organism also plays a vital role in the
spoilage of the different foods.
Sunlight
 Sunlight is the major source of energy.
 Plants require sunlight for the photosynthesis process. It is the process by which plants
make oxygen and food using carbon dioxide and water and make it available for the
animals.
 The presence of sunlight also affects the breeding cycle in animals.
  Some animals are nocturnal, that they are active only at night time. It is due to the
sunlight.
 Light also determines the reproductive and migratory activities.
 A photographic light meter is used to measure light intensity while the secchi disc
measures light penetration in water

Temperature
 Temperature is an important abiotic factor in an ecosystem.
 With the variations in the temperature, variations occur in the type of plants and animals.
For eg: Yak lives in cold regions where there is low temperature.
 Nature has adjusted the body like the presence of long furs which make it possible to
survive.
 Similarly, in the case of microorganisms, depending on the temperature they are
classified as psychrophiles, mesophiles, thermophiles, thermotolerant, extremophiles.
 The temperature determines the rate of the metabolic reactions. It affects various enzyme-
catalyzed reactions.
 Thermometer is an instrument used to measure temperature

Soil
 Soil is an important abiotic factor. It is made up of rocks along with the decomposed
plants and animals.
 With the help of the roots, plants acquire the water and minerals from the soil. Soil are
also of various types, whose nature and composition vary and have different functions.
 The water holding capacity is also determined by its composition.
 In the aquatic environment, depending upon the characteristics of the sediment, it
determines the type of the benthic animals

Atmosphere
 Due to the atmosphere, life is sustained on the earth.
 Plants use the carbondioxide when animals use oxygen gas.
  The atmosphere also protects the animals from the harmful UV radiation from the sun.
 Humans and other animals are susceptible to the damage by harmful UV radiation.
 On exposure, it may cause some genetic change as well as has the capacity to trigger skin
cancer.
 It looks like a shield that provides protection to the creatures on earth.
pH
 pH (Hydrogen ion Concentration) :pH is the measure of how acidic or alkaline water
is in aquatic animals or soil solution. It influences the distribution of plants and animals
in soil and fresh water ponds. Some plants drive well in acidic conditions while others in
alkaline conditions. The pH of a soil can be altered by leaching fertilizers applied or soil
exhaustion. pH is expressed in terms of Ph scale by use of BDH universal indicator
solution or paper and pH meter

Humidity
 Humidity means the presence of water vapor in the air.
 Too much of the humid environment can be dangerous to the organisms.
 Excessive water may disrupt the internal balance in the organisms in various ways.
Changes in pH may also occur.
 Humidity affects the rate at which water evaporates from the surface of organisms such
as in transpiration or sweating. This in turn affects their distribution on earth. Paper
Hydrometer is used to measure humidity or a wet and dry bulb hydrometer

Wind
Wind is moving air. It increases the rate of water loss from the organisms, therefore
affecting their distribution. Wind is also important information of rain. In deserts winds
form sand dunes which can be habitats for other organisms. It causes wave formation in
lakes and ocean, which enhance aeration of water in this water bodies. It also disperses
spores and seeds hence influence disposal and migration of flying animals. A wind vane
or wind sock is used to determine the direction of prevailing wind and Anemometer is
used to measure the speed of wind.
Salinity:
It refers to the salt concentration of water, causing a division of the aquatic environment into
marine, estuarine and fresh water. Saline conditions immediately outside the body of organism
pose the problem of water loss from the body to the environment. Only animals with suitable
osmoregulation adaptations can occupy such habitats. Salinity can be determined by calculating
percentage of salts on water or by the acid-base titration method.

TYPES OF HABITATS
Habitat refers to a place or location where an organism (or a biological population) lives, resides
or exists. The term habitat came from the Latin “habitatus” meaning “having been inhabited”.
E.g., the habitat of a tadpole is the bottom of freshwater ponds or streams.
There are two main types of habitats namely;
1. Aquatic habitat
2. Terrestrial habitat
Aquatic habitats
There are three kinds of aquatic habitat
a. Marine/salt water habitat e.g, ocean, sea
b. Estuarine habitat
c. Fresh water habitat

Marine habitats
Characteristics of marine Habitat are as follows;
i. The marine habitat constitutes the largest habitat in the biosphere (70% of the earths area)
ii. They do not undergo sudden or rapid changes in physical factors such as temperature, PH
and specific gravity.
iii. Chemical composition; marine water consists of many kinds of dissolved ions including
Na+, K+, Mg ion etc.
iv. Hydrogen ion concentration (PH); salt water is alkaline in nature with a PH of about 8.0-
9.0 near the surface
v. Salinity (salt concentration in water); the sea water has high salinity. The average salinity
of sea water is 35 parts per thousand
vi. The density of marine water is high. It is about 1.028 while that of fresh water is 1.0, this
allows many organisms to float in it
vii. The temperature of the sea changes less quickly than that of the land. However, the
temperature falls with an increase in the depth of the sea.
viii. Oxygen concentration is highest at the surface where the atmospheric oxygen dissolved
in water. The concentration of oxygen decreases with depth.

Distribution of organisms in the marine habitat

i. Organisms of the splash zone include periwinkles; crustaceans eg ghost cabs, sea weeds
and sargassum (algae)
ii. Those of intertidal zone include starfish, sea anemones, sponges, sea urchins, annelids,
Mollusca and barnacles.
iii. In the subtidal zones are crabs, lobsters and cray fish
iv. The benthic zone is unfavourable for life. The producers are absent only few saprophytic
animals are present
v. Oceanic water house sharks, croaker, sea fish, mackerel, bonga fish etc.

Estuarine habitat (brackish water habitats)

An estuary is a body of water formed at the coast where freshwater flowing towards the sea
mixes with the sea (salt water) flowing inland. Estuarine habitats include deltas, lagoons and
bays.
Characteristics of estuarine
i. The salinity fluctuates
ii. The specific gravity is less than that of the sea
iii. They have high turbidity due to disturbances. Hence the rate of photosynthesis and
respiration by organisms reduce
iv. The water is shallow
v. They have a low diversity of species compared to marine habitat
vi. They have high level of nutrients
vii. They have low oxygen content, hence anaerobic activities are common
viii. Plants found in estuaries include planktons, algae, red and white mangrove
ix. Animals including mosquitoes, crustaceans, Mollusca, worms, fishes etc. are found in
estuaries

Fresh water habitats

This is a body of water formed mainly from inland waters and it contains very low or no salt.
Freshwater is of two types based on its mobility
1. Lotic fresh water: these are running waters flowing continuously in a specific
direction e.g. rivers, streams, springs.
 2. Lentic fresh waters: These are stagnant water which do not flow e.g. lakes, ponds,
puddles, swamps and dams

Characteristics of fresh water habitat

i. It contains little or no salt
ii. It is small in size
iii. Oxygen concentration is high, being available in all parts of the water body, especially at
the surface
iv. The water is shallow, hence sunlight penetrates to the bottom
v. The temperature varies with season and depth
vi. It has seasonal variation; decreasing or drying up in the dry season and increasing in the
rainy season
vii. Water currents affect the distribution of organisms, salts and gases, especially in lotic
fresh waters
viii. Plants of fresh water include water lily, spirogyra, water lettuce, water weeds etc.
ix. Animals of freshwater habitat include protozoa, hydra, fishes etc.

Terrestrial Habitat
Terrestrial habitat is a habitat that is found predominantly on land. They include plant and
animals that are found living on the ground and under the ground. Basically, terrestrial habitat is
sub divided into four main parts namely;
i. Marsh
ii. Forest
iii. Grassland/savannah
iv. Arid land/desert

Marsh
Marsh is a low land, flooded in rainy season and usually water logged because of poor drainage.
The vegetation is predominantly of grasses and shrubs. When trees grow in a marsh, it is called a
swamp. Marsh is a transition between aquatic habitat and terrestrial habitat.

Characteristics of marsh habitat

 A marsh is a low land
  It is always flooded, wet and water logged
 It has a high relative humidity
 Its water sometimes contains many decaying organisms
 The water has a foul smell
 The plants found in this habitat include; algae, grasses, water lettuce, water lilies, Raphia
palms, white and red mangrove etc.
 Animals found in marshes include frogs, snakes, crocodiles, hermit crabs, mud-skippers
etc.

Forests
A forest is a community of plants in which trees are dominant. There are different kinds of
forests whose distribution is determined mainly by climatic factors such as temperature, rainfall
and at times by soil elevation and man’s activities such as farming, lumbering, bush burning,
construction of roads and building. The major type of forest in Nigeria is the rain forest.

Characteristics of forests
 The forest is rich in epiphytes and climbers
 The interior of the forest has high humidity, low light intensity and damp floor
 Presence of tall trees with canopies and existing in layers
 Trees are mesophytes with broad leaves
 The trees have buttress roots to support their heavy weight and height
 The trees have thin barks for gaseous exchange and transpiration
 Forest plants (trees) include African walnut, mahogany, obeche, iroko, oil palm
 Most forest animals are arboreal (living on trees) and these include bats, monkeys, snakes,
squirrels, birds, tree frogs, chameleons. Some live in the soil e.g. earthworms and beetles
while others live among the litters on the ground e.g. millipedes, ants and snails.

Grassland (savanna)
This is a plant community in which grass species are dominant, but trees and shrubs may be
present

Characteristics of grassland
 Temperature is usually high and sunshine is intense
 The relative humidity is low and rainfall scanty (60-150cm annual rainfall)
  Abundant grassland with few short trees sparsely distributed
 Bush fire is frequent and trees are fire resistant
 Deciduous plants (plants that shed their leaves in dry season) are present
 Plants possess underground stems and deep roots to search out for water
 Trees have modified leaves for adaptation to the environment
 The grassland plants include; acacia, elephant grass, guinea grass, palms, baobab trees etc.
Basically, there are four major types of savanna in Nigeria, namely;
a. Southern guinea savanna
b. Northern Guinea savanna
c. Sudan savanna
d. Sahel savanna

Arid lands (desert)

These are areas of very low rainfall and high evaporation rate. They are the driest habitat,
receiving less than 25cm rainfall annually. Arid lands are of two types;
i. Hot deserts e.g. Sahara desert (North Africa), Kalahari desert (South Africa)
ii. Cold deserts e.g. desert in North America

Characteristics of a desert
 Water is very scarce
 Temperature is very high by the day and very low by the night
 Vegetation is very scanty
 The soils are sandy or rocky
 Strong winds occur frequently and sunshine very intense
 Presence of drought resistance plants